Preprint
|
|
|
Materials Science, Biomaterials; smart; calcium phosphate; monetite; barium titanate; bioceramics; orthopedics
Online: 24 June 2018 (08:02:03 CEST)
|
|
Share this article with
×
The present study is first of its kind which deals with the development of a specific bioceramic which qualifies as potential materials in hard-tissue replacements. Specifically, we report the synthesis and evaluation of smart injectable calcium phosphate bone cement (CPC) which we believe will fit into various kinds of orthopedic and spinal-fusion applications. The smart nature of this next generation orthopedic implant is attained by incorporating piezoelectric barium titanate (BT) particles into monetite-based (dicalcium phosphate anhydrous, DCPA) CPC composition. The main hypothesis is to take advantage of the piezoelectric properties of BT, as electromechanical effect plays a vital role in fracture healing at the defect site and bone integration with the implant. Furthermore, radiopacity of BT would help in easy detection of the CPC presence at the fracture site during surgery. Results reveal that BT addition favors in important properties of bone cement like good compressive strength, injectability, bioactivity, biocompatibility and even washout resistance. Most importantly, the self-setting nature of the bone cements are not compromised with BT incorporation. The in vitro results confirm that the developed bone-cement abides with the standard orthopedic requirements making it apt for real-time prosthetic materials.
Preprint
|
|
|
Materials Science, Polymers & Plastics; biodestruction, soil constructions, sustainability, polymers, synthetic hydrogels, peat, CO2 emission, water-retention, modeling.
Online: 22 June 2018 (14:20:10 CEST)
|
|
Share this article with
×
Decomposition of natural and synthetic polymeric materials (peat, humates, biochar, strongly swelling hydrogels and other soil conditioners) in a biologically- and chemically- active soil environment inevitably leads to their degradation and ability to improve the structure, water-retention, absorptive capacity and actual fertility of artificial soil constructions in urbanized ecosystems and agro landscapes (constructozems). Quantitative assessment of the biodegradation process using field and laboratory incubation experiments, as well as mathematical modeling, showed the possibility of significant (up to 30-50% per year) losses of organic matter of constructozems and a corresponding deterioration in their quality. Incubation experiments with the analysis of carbon dioxide emission for polymeric materials under given thermodynamic conditions allow to estimate the potential rates of their decomposition (half-life) and their dependence on the dose of inhibitors of microbial activity. Special nomographs provide an opportunity to determine the optimum depth of the arrangement of organic components in soil constructions to ensure their stable functioning during a fixed operating time in urban conditions. The results of the study are useful for geo-engineers and landscaping practitioners.
Preprint
|
|
|
Materials Science, Biomaterials; macromolecular crystallography; X-ray diffraction; radiation damage; absorption; electronic excitations; quantum chemistry
Online: 22 June 2018 (08:15:27 CEST)
|
|
Share this article with
×
Macromolecular crystallography at cryogenic temperatures has so far provided the majority of the experimental evidence that underpins the determination of the atomic structures of proteins and other biomolecular assemblies by means of single crystal X-ray diffraction experiments. One of the core limitations of the current methods is that crystal samples degrade as they are subject to X-rays, and two broad groups of effects are observed: global and specific damage. While the currently successful approach is to operate outside the range where global damage is observed, specific damage is not well understood and may lead to poor interpretation of the chemistry and biology of the system under study. In this work, we present a phenomenological model in which specific damage is understood as the result of a single process, the steady excitation of crystal electrons caused by X-ray absorption, which acts as a trigger for the bulk effects that manifest themselves in the form of global damage and obscure the interpretation of chemical information from XFEL and synchrotron structural research.
Preprint
|
|
|
Materials Science, General Materials Science; vacuum brazing; metallic glasses; Ti-alloy; mechanical properties
Online: 21 June 2018 (04:12:23 CEST)
|
|
Share this article with
×
The developed microstructure features a long with mechanical properties in vacuum brazing of commercially pure Ti-alloy using Ti20Zr20Cu60-x-Nix (x=10, 20, 30, 40 and 50) metallic filler. Brazing temperatures and holding times employed in this study were 1240-1279 K (967-1006oC) for a period of 10 min, respectively. The mechanical properties of brazed joints were evaluated by nanoindention at a constant peak load of 5000 μN and tensile tests. The number of intermetallic phase, such as NiTi2, Ti2Cu, (Ti, Zr)2Cu, (Ti, Zr)2Ni, β(Ti, Zr), α-Ti and NiTi. The solid solution matrix have been identified at 1279 K out of these different regions the NiTi2 rich region had the highest nanohardness of 17 GPa, It is interesting to note that among five different glasses, the Ti20Zr20Cu10Ni50 has the highest yield strength of 17 GPa, which is mainly due to NiTi2 phase. Based on the tensile test results all cracks propagate along the brittle intermetallic compounds like NiTi2 in the reaction layer the reduction of the strength of the joints and fracture behaviour upon propagation of the crack, which shows the morphological cleavage including facets characteristics.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; bionic composites; thin films; mechanical properties
Online: 20 June 2018 (09:58:32 CEST)
|
|
|
Share this article with
×
Regenerated silk (RS) is a protein-based “biopolymer” that enables the design of new materials; here we sought to “bionic” the process of regenerated silk production by fermentation assisted method. Based on yeast’s fermentation, here we produced a living hybrid composite made of regenerated silk nanofibrils and a single-cell fungi, the Saccharomyces Cerevisiae yeast extract, by fermentation of such microorganisms at room temperature in the dissolution bath of silkworm silk fibers. The fermentation-based processing enhances the beta-sheet content of the RS, corresponding to a reduction in water permeability and CO2 diffusion through RS/yeast thin films enabling the fabrication of mechanically robust film that enhances the food storage durability. Finally a transfer print method, which consists of transferring RS and RS/yeast film layers onto self-adherent paraffin substrate, was used for the realization of heat – responsive wrinkles by exploiting the high thermal expansion of the paraffin substrate that regulates the applied strain, resulting in a switchable coating morphology from the wrinkle-free state to a wrinkled state if the food temperature overcomes a designed threshold. We envision that such efficient and smart coatings can be applied for the realization of smart packaging that through such temperature sensing mechanism can be used to control the food storage conditions.
Preprint
|
|
|
Materials Science, General Materials Science; metallic glasses; Ti-alloy; microstructure; scanning electron microscopy and transmission electron microscopy
Online: 20 June 2018 (03:31:13 CEST)
|
|
Share this article with
×
The present study investigation, our results on characterization of commercially pure-Ti alloy brazed with metallic glass ribbons of Ti20Zr20Cu60-xNix (x = 30, 40, and 50) metallic glass ribbons were produced using a vacuum melt spinner. These ribbons were then used as filler materials for vacuum brazing of two Ti alloy plates at 1268, 1277 and 1279 K for a period of 10 min. Field-Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and the energy dispersive X-ray spectroscopy (EDX). The as-spun ribbons showed fully amorphous structure when examined on both surfaces by XRD and also verified by TEM investigation. The brazing joint of two Ti-plates using the metallic glass ribbon when brazed with Ni50 was found to be of very high strength. FESEM characterization of the cross-section of the brazed joints shows sub-micron size grains uniformly distributed in the matrix with brighter appearance. FESEM and EDX analysis revealed that the sub-micron grains are rich in Ti & Ni while the matrix phase mainly consisted of Ti. BSE image along with EDS Analysis indicated that the brazed joint has a presence of NiTi2 and Cu2 (Ni Zr) phases which could be responsible for increase in the strength of the brazed joint.
Preprint
|
|
|
Materials Science, Biomaterials; fabric classification; fabric wrinkle recovery; PhabrOmeter; directional and side effects
Online: 19 June 2018 (10:47:43 CEST)
|
|
Share this article with
×
It is demonstrated in this study that PhabrOmeter creates genuine wrinkle on fabrics comparable to that in AATCC specifications, and measures fabric wrinkle recovery values fast with repeatable and reliable results with high resolution, over wide range of fabric types. It thus provides an appealing alternative to the existing test methods that are known to be slow, insensitive and unreliable. In addition, with enormous varieties of fabrics, we used a new criterion termed fabric linear density λ so that fabrics can in general be divided into relatively homogeneous groups for further study. The calculation and application of this parameter are showed in this report.
Preprint
|
|
|
Materials Science, Nanotechnology; Nanoparticles; Toxicological effects; Organ-specific effects
Online: 18 June 2018 (15:32:41 CEST)
|
|
Share this article with
×
Nanoparticles (NPs) are widely used in diverse disciplines, including biology, medicine science. The central question that need to be answered is whether NPs have toxic effects on biological cells and molecules or are they safe. The safety of NPs including targeted drug delivery is critical and so is their toxicity in the environment. In recent years, in vitro and in vivo research on animals has generated abundant information about the toxicity of NPs. However, due to varying laboratory conditions, the comparison of the results from ensuing studies is somewhat unreliable. It should be noted that, depending on the type of production, NPs can enter the body through inhalation, skin and via digestive routes. Due to the diversity of NPs and their properties, there is paucity of accurate information on their toxicological effects; particle size, shape, surface area and the chemical levels are considered as key factors in creating health and toxicological effects. Consequently, there is a need for reliable information about their effects on various organs so as to deal with NPs effectively and their impact on health and the environment. This review covers the existing knowledge base on the subject that hopefully prepares us better to address these challenges.
Preprint
|
|
|
Materials Science, Biomaterials; mesoporous silica; surface area; rice husk ash; hydrolysis-ageing time, hydrophobicity
Online: 18 June 2018 (13:38:56 CEST)
|
|
Share this article with
×
This work describes the preparation of mesoporous silica by the green reaction of rice husk ash (RHA) with glycerol, followed by the modification and the potential use as a drug carrier. The reaction was carried out at 215 °C for 2 h. The solution was further hydrolyzed with deionized water and aged for various times (24, 48, 120, 360, 528 and 672 h) before calcinations at 500 oC for 24 h. Further treatment of prepared mesoporous silica was performed using trimethylmethoxysilane (TMMS) to obtain hydrophobic Mesoporous silica. For all synthesized silica, silica contents were as high as 95%wt, whereas organic residues were less than 3%wt. RHA-glycerol showed the highest specific surface area with smallest pore diameter (205.70 m2/g, 7.46 nm) when aged for 48 h. The optimal hydrolysis-ageing period of 120 h resulted in 500.7 m2/g BET surface area, 0.655 cm3/g pore volume and 5.23 nm pore diameter. The surface modification of RHA-glycerol was succeeded through the reaction with TMMS as confirmed by FTIR. Ibuprofen was selected as a model drug for the adsorption experiments. The adsorption under supercritical CO2 was carried out at isothermal temperature of 40 ˚C and 100 bar, % ibuprofen loading of TMMS modified mesoporous silica (TMMS-g-MS) was 6 times less than mesoporous silica aged for 24 h (MS-24h) due to the hydrophobic nature of modified mesoporous silica, not surface and pore characteristics. The release kinetics of ibuprofen-loaded mesoporous silicas were also investigated in vitro. The release rate of ibuprofen-loaded MS-24h was much faster than that of ibuprofen-loaded TMMS-g-MS, but comparable to the crystalline ibuprofen. The slower release rate was attributed to the diffusion control and the stability of hydrophobic nature of modified silica. This would allow the design for the controlled release drug delivery system.
Preprint
|
|
|
Materials Science, Nanotechnology; Nanobeam; fractional-order; nonlinearity; Winkler-Pasternack
Online: 15 June 2018 (14:48:29 CEST)
|
|
Share this article with
×
In the present study, nonlinear vibration of a nanobeam resting on fractional order viscoelastic Winkler-Pasternak foundaion is studied using nonlocal elasticity theory. D'Alembert principle is used to derive the governing equation and the associated boundary conditions. The approximate analytical solution is obtained by applying the multiple scales method. Detailled parametric study is conducted, the effects of variation in different parameters belonging to the application problems on the system are calculated numerically and depicted. We remark that the order and the coefficient of the fractional derivative have significant effect on the natural frequency and the amplitude of vibrations
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; laser cladding; powder flow; 316L stainless steel
Online: 15 June 2018 (11:50:29 CEST)
|
|
Share this article with
×
Laser Cladding is one of the leading processes within Additive Manufacturing technologies, a fact which has concentrated an important amount of effort on its development. In regard to the latter, the current study aims to summarize the influence of the most relevant process parameters in the laser cladding processing of single and compound volumes (solid forms) made from AISI 316L stainless steel powders and using a coaxial nozzle for deposition. Process speed, applied laser power and powder flow are considered to be the main variables affecting laser cladding in single clads, meanwhile overlap percentage and overlapping strategy become also relevant when dealing with multiple clads. By means of setting appropriate values of each process parameter, the main goal of this paper is to develop a processing window in which a good metallurgical bond between the delivered powder and substrate is obtained, trying simultaneously to maintain processing times in their lowest value possible. Conventional metallography techniques were performed on the cross sections of the laser tracks to measure the effective dimensions of clads for dilution analysis, height and width for the values of overlap between contiguous clads and layers, and also to analyze them for physical defects such as porosity and cracks. The resulting solid piece was 8 mm high at 800 mm/min.
Preprint
|
|
|
Materials Science, Polymers & Plastics; biaxial stretching; blend; polycarbonate; PMMA; phase inversion; surface hardness
Online: 15 June 2018 (10:51:13 CEST)
|
|
Share this article with
×
We investigated the structural evolution of the two-phase blends of polycarbonate (PC) and poly(methyl methacrylate) (PMMA) at various blend compositions by simultaneous biaxial stretching using optical microscopy and SEM observation. The spherical PMMA domains and PC matrix in 30/70 PC/PMMA were enlarged uniformly at all in-plane direction, while the anisotropic-shaped co-continuous structure in 50/50 PC/PMMA was deformed to crosshatched one by in-plane bimodal orientation. In 70/30 PC/PMMA, the phase inversion was found to occur by simultaneous biaxial stretching; i.e., the spherical PMMA domains were changed to crosshatched matrix by in-plane bimodal orientation due to coalescence of the PMMA domains during the stretching. Owing to the phase inversion, the surface hardness estimated by pencil hardness test became harder from 2B to 2H with increasing the strain from 1.0 to 2.0.
Preprint
|
|
|
Materials Science, Polymers & Plastics; Keywords: 3D dose imaging; radio-fluorogenic gel; polymer gel dosimetry; radio-fluorogenic co-polymerization; tertiary-butyl acrylate gel; proton beam imaging
Online: 14 June 2018 (16:05:06 CEST)
|
|
Share this article with
×
Abstract: We review the development and application of an organic polymer-gel capable of producing fixed, three-dimensional fluorescent images of complex radiation fields. The gel consists for more than 99% of γ-ray-polymerized (~15% conversion) tertiary-butyl acrylate (TBA) containing ~100 ppm of a fluorogenic compound, e.g. maleimido-pyrene (MPy). The radio-fluorogenic effect depends on copolymerization of the MPy into growing chains of TBA on radiation-induced polymerization. This converts the maleimido residue, which quenches the pyrene fluorescence, into a succinimido moeity (SPy), which doesn't. The intensity of the fluorescence is proportional to the yield of free-radicals formed and hence to the local dose deposited. Because the SPy moieties are built into the cross-linked polymer matrix the image is fixed. The method of preparing the gel and imaging the radiation-induced fluorescence are presented and discussed. The effect is illustrated with fluorescent images of the energy deposited in the gel by beams of X-rays, electrons and protons as well as a radioactive isotope.
Preprint
|
|
|
Materials Science, General Materials Science; responsive materials; smart materials; bioinspired materials; non-living plant tissues; anisotropy; thermal fatigue; microstructure; 4D printing; additive manufacturing
Online: 14 June 2018 (09:01:53 CEST)
|
|
|
Share this article with
×
In Nature, it is common for living plants and non-living plant tissues to consist of materials with anisotropic multilayer and non-homogenous structure. The structure of tissues determines their self-shaping and self-folding capabilities in response to a stimulus in order to activate different functionalities. Predetermined movements are realized according to changes in environmental conditions, which trigger the fibrous anisotropic structure of the plants’ material. In this study, we present the fabrication process of low-cost anisotropic multilayer materials that are capable of realizing complex movements caused by small temperature changes (<40 oC). The mismatch in the thermo-mechanical properties between three or more anisotropic thin layers creates responsive materials that alter their shape owing to the developed internal stresses. Isotropic layers can perform only bending movements, whereas anisotropic multilayer materials can perform bending, twisting or complex combined modes. The movements of the material can be controlled by forming anisotropic homogenous metallic strips over an anisotropic polymer. As a result, inexpensive responsive materials can be developed to passively react to a very broad range of thermal requirements. We studied the major parameters that affect the sensitivity of the developed materials, as well as their failure modes and crack formation under thermal fatigue conditions.
Preprint
|
|
|
Materials Science, Biomaterials; Zirconia; primer; priming; bonding; catechol; dental; prosthodontics
Online: 13 June 2018 (06:06:31 CEST)
|
|
Share this article with
×
Zirconia has recently become one of the most popular dental materials in prosthodontics being used in crowns, bridges, and to implants. However, weak bonding strength of dental adhesives and resins to zirconia surface has been a grand challenge in dentistry, thus finding a better adhesion to zirconia is urgently required. Marine sessile organisms such as mussels use a unique priming strategy to produce a strong bonding to wet mineral surfaces; one of the distinctive chemical features in the mussel’s adhesive primer proteins is high catechol contents among others. In this study, we pursued a bioinspired adhesion strategy, using a synthetic catechol primer applied to dental zirconia surfaces to study the effect of catecholic priming to shear bonding strength. Catechol priming provided a statistically significant enhancement (P < 0.05) in shear bonding strength compared to the bonding strength without priming, and relatively stronger bonding than commercially available zirconia priming techniques. This new bioinspired dental priming approach can be an excellent addition to the practitioner’s toolkit to improve dental bonding to zirconia.
Preprint
|
|
|
Materials Science, General Materials Science; Ionic liquids; N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide; Poly(EthyleneOxide); Polymer electrolytes; Lithium polymer batteries
Online: 12 June 2018 (10:02:49 CEST)
|
|
Share this article with
×
Li+-conducting polyethylene oxide-based membranes, incorporating the N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, are as electrolyte separators for all-solid-state lithium polymer batteries operating at medium-high temperatures. The incorporation of the ionic liquid remarkably improves the thermal, ion-transport and interfacial properties of the polymer electrolyte, which, in combination with the wide electrochemical stability even at medium-high temperatures, allow high current rates without any appreciable lithium anode degradation. Battery tests carried out at 80 °C have shown excellent cycling performance and capacity retention even at high rates, never tackled by ionic liquid-free polymer electrolytes. No dendrite growth onto the lithium metal anode was observed.
Preprint
|
|
|
Materials Science, Metallurgy; operational aircraft; skin corrosion; fatigue crack growth; stress corrosion cracking; buckling
Online: 12 June 2018 (08:36:13 CEST)
|
|
Share this article with
×
This paper studies the combined effect of corrosion and fatigue on the growth of cracks in aircraft and on the effect of skin corrosion and stress corrosion cracking on the load bearing capacity of rib stiffened aircraft wings. In this context it is shown that the growth of cracks from surface pitting, and also from intergranular cracking at a fastener hole, can be accurately computed using the Hartman-Schijve variant of the NASGRO crack growth equation. The examples studied support the lead crack approach, that has been independently developed by the USAF and the Australian Defence Science Technology Group, in which the growth of lead cracks is often exponential. In the case of skin corrosion it is shown that to be consistent with the US Joint Service Structural Guidelines (JSSG2006) assessment of its effect on the load bearing capacity of the wing should involve an assessment of whether at 115% DLL the remaining material exceeds the yield stress of the material.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; surface removal; nanoscale process; copper thin film; ultrathin water film
Online: 12 June 2018 (06:11:36 CEST)
|
|
|
Share this article with
×
The surface planarity and asperity removal behaviors of atomic scale under the ultrathin water environment was studied for the nanoscale process by molecular dynamics simulation. The monolayer atomic removal was achieved under the noncontact and monoatomic layer contact conditions with different water film thickness, and the newly formed surface is relatively smooth and no deformed layer and plastic defects exist. The nanoscale processing is governed by the interatomic adhering action during which the water film transmits the loading forces to Cu surface and thereby result in the migration and removal of surface atoms. With scratching depth ≥ 0.5 nm, the abrasive particle squeezed out the water film from scratching region and scratched Cu surface directly, leading to the surface quality deterioration mainly governed by the plowing action. This study brings the goals of “0 nm planarity, 0 residual defects and 0 polishing pressure” closer to us in the nanoscale process for the development of ultra-precision manufacture technology.
Preprint
|
|
|
Materials Science, Other; molecular dynamics simulation; amorphous; physical stability; hydrogen-bond; molecular mobility; mixing energy; molecular interactions
Online: 11 June 2018 (10:24:14 CEST)
|
|
|
Share this article with
×
Amorphous solid dispersions are considered a promising formulation strategy for the oral delivery of poorly soluble drugs. The limiting factor for the applicability of this approach is the physical (in)stability of the amorphous phase in solid samples. Minimizing the risk of reduced shelf life for a new drug by establishing a suitable excipient/polymer-type from first principles would be desirable to accelerate formulation development. Here we perform Molecular Dynamics simulations to determine properties of blends of eight different polymer-small molecule drug combinations for which stability data is available from a consistent set of literature data. We calculate thermodynamic factors (mixing energies) as well as mobilities (diffusion rates and roto-vibrational fluctuations). We find that either of the two factors, mobility and energetics, can determine the relative stability of the amorphous form for a given drug. Which factor is rate limiting depends on physico-chemical properties of the drug and the excipients/polymers. The methods outlined here can be readily employed for an in-silico pre-screening of different excipients for a given drug to establish a qualitative ranking of the expected relative stabilities, thereby accelerating and streamlining formulation development.
Preprint
|
|
|
Materials Science, Biomaterials; wound healing; catechol; conjugated; antioxidant; antiinflammatory; bioadhesion; UV shielding
Online: 8 June 2018 (12:28:07 CEST)
|
|
|
Share this article with
×
The effective treatment for chronic wounds constitute one of the most common worldwide health care problem due to the presence of high levels of proteases, free radicals and exudates in the wound, which constantly activate the inflammatory system avoiding the tissue regeneration. In this study, we describe a multifunctional bioactive and resorbable membrane with in-built antioxidant agent for the continuous quenching of free radicals as well as to control inflammatory response helping to promote the wound healing process. To reach that goal synthesized statistical copolymers of N-vinylcaprolactam (V) and 2-hydroxyethyl methacrylate (H) have been conjugated with catechol bearing hydrocaffeic acid (HCA) molecules. The natural polyphenol (catechol) is the key molecule responsible for the mechanism of adhesion of mussels, and provides the functionalized polymer conjugate a continuous antioxidant response, antiinflammatory effect, UV screen and bioadhesion in the moist environment of the human body, all of them key features in the wound healing process. Therefore, these novel mussel-inspired materials have an enormous potential of application and can act very positively, favoring and promoting the healing effect in chronic wounds.
Preprint
|
|
|
Materials Science, General Materials Science; Impact-sliding wear; Titanium alloy; Laser shock peening; Wear rate
Online: 7 June 2018 (15:13:24 CEST)
|
|
Share this article with
×
Outer particles collision with certain dynamic object is not a pure impact wear behavior; it is typically accompanied by sliding wear phenomena. This study aimed investigating the impact-sliding wear performance of three different TC17 titanium alloys. One was untreated, and the other two were subjected to laser shock peening (LSP) by 5 and 7 J pulse energy, respectively. Wear test was performed on a novel impact-sliding wear testing rig, which can realize multiple impact-sliding motions by changing motion parameters in x and z directions. Present results showed that wear resistance of both treated samples improved compared with the untreated alloy. Given the increase in wear cycles, increment in wear rate of the untreated sample was constantly higher than those of treated samples. All results can be attributed to the increase in surface hardness of the material and residual compressive stress, which was also introduced after LSP.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; crystallization of thin films; ambient crystallization; room temperature crystallization; magnet induce crystallization; sparking discharge
Online: 7 June 2018 (11:32:14 CEST)
|
|
Share this article with
×
Grazing incidence X-Ray Diffraction spectroscopy was employed to characterize crystallinity of Iron, Nickel, Copper and Tungsten, prepared by sparking discharge process in presence of 0.4 T magnetic field at ambient temperature 25 °C. Iron thin film preserved crystallinity even after one year of ageing. Nickel exhibit higher crystallinity when sparked in nitrogen gas flow from the one sparked in oxygen. Tungsten was successfully crystalized after just 40 minutes of sparking inside of magnetic field.
Preprint
|
|
|
Materials Science, General Materials Science; Al-Mn-Mg alloy; dispersoids; heat treatment; elevated temperature; strength; creep resistance
Online: 7 June 2018 (05:59:45 CEST)
|
|
Share this article with
×
Present work has systematically investigated the evolution of dispersoid and elevated-temperature properties including the strength and creep resistance during the various multi-step heat treatments in Al-Mn-Mg 3004 alloys. Results show that only α-Al(MnFe)Si dispersoid is observed in the studied temperature range (up to 625°C) and it coarsens with increasing temperature to 500°C but dissolves at 625°C. The evolution of elevated-temperature strength and creep resistance is greatly related to the temperature of each step during the multi-step heat treatments. Generally, lower temperature at the first-step heat treatment leads to higher properties while the properties decrease with increasing temperature of last-step heat treatment. Suitable models have been introduced to explain the evolution of strength and the creep threshold stress at elevated-temperature during the various heat treatments.
Preprint
|
|
|
Materials Science, Other; collective vibration; raman spectroscopy; superconductivity; CuO2 plane; YBCO system
Online: 6 June 2018 (13:11:24 CEST)
|
|
Share this article with
×
The phonon modes in YBa2Cu3O7-δ and YBa2-xLaxCu3O7-δ systems have been systematically studied by Raman spectroscopy. The new phonon modes of 104 cm-1, 94 cm-1, and 89 cm-1 were found in all these samples. A crude estimate about the wavenumber of the collective vibration of the stable CuO2 plane was given in this paper. The standard deviations of the new phonons in YBa2Cu3O7-δ and YBa2-xLaxCu3O7-δ systems were discussed. The results of the calculation indicated that the 104 cm-1 mode probably stands the c-direction collective vibration of the stable CuO2 plane, the 94 cm-1 mode stands the a-direction vibration, and the 89 cm-1 mode stands b-direction vibration. The relevance between these phonons and the superconductivity was discussed. It is found that, as the Tc decreased, the 104 cm-1 mode and the 94 cm-1 mode softened, and the 89 cm-1 mode hardened slightly.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; cermet coating; aluminia-titania; thermal spraying; cavitation erosion; microstructure; wear model.
Online: 6 June 2018 (12:07:17 CEST)
|
|
Share this article with
×
This manuscript deals with the cavitation erosion resistance of low-velocity oxy-flame (LVOF) sprayed Al2O3–40%TiO2/NiMoAl cermet coatings, a new functional application of cermet coatings. The aim of the study was to investigate the cavitation erosion mechanism and determine the effect of feedstock powder ratio (Al2O3–TiO2/NiMoAl) of LOVF cermet coatings on their cavitation erosion resistance. As-sprayed coatings were investigated for roughness, porosity, hardness, Young’s modulus. Microstructural characteristics of the cross-section and the surface of as-sprayed coatings were examined by light optical microscopy (LOM) and scanning electron microscopy (SEM) equipped with the EDS and XRD methods. Coatings cavitation tests were conducted in accordance with the ASTM G32 standard with usage of reference samples made from steel, copper and aluminum alloys. Cavitation erosion resistance was measured by weight and volume loss, and normalised cavitation erosion resistance was calculated. Surface eroded due to cavitation was examined in successive time intervals by LOM and SEM-EDS. On the basis of coating properties and cavitation investigations, a phenomenological model of the cavitation erosion of Al2O3–40%TiO2/NiMoAl cermet coatings was elaborated. General relationships between their properties, microstructure and cavitation wear resistance were established. The Al2O3–40%TiO2/NiAlMo composite coating containing 80% of ceramic powder has a higher cavitation erosion resistance than the reference aluminium alloy.
Preprint
|
|
|
Materials Science, Metallurgy; titanium matrix composites; microstructure; mechanical properties; forging
Online: 6 June 2018 (05:54:56 CEST)
|
|
Share this article with
×
In this study, a 5vol. % (TiBw+TiCp)/Ti composite pancake with a diameter of 260mm was prepared by casting followed by open die forging in (α+β) phase region. The microstructures of the composite pancake are inhomogeneous, in terms of both matrix microstructure and distribution of reinforcements. The matrix microstructures were gradually refined from the periphery to centre of the pancake. The TiBw and TiCp reinforcements tend to be uniformly distributed in the centre region and. It is suggested that the microstructure difference can be mainly ascribed to the temperature variation from the periphery to the centre. Additionally, tensile testing results showed that the centre region of the composite pancake exhibits higher strength than the peripheral region. The strengthening mechanism and the softening behavior of the composite pancake with temperature is discussed.
Preprint
|
|
|
Materials Science, Biomaterials; molecular graph; degree-based index; silicon-carbon
Online: 5 June 2018 (12:44:44 CEST)
|
|
Share this article with
×
The application of graph theory in chemical and molecular structure research far exceeds people's expectations, and it has recently grown exponentially. In the molecular graph, atoms are represented by vertices and bonded by edges. Closed forms of multiplicative degree-based topological indices which are numerical parameters of the structure and determine physico-chemical properties of the concerned molecular compound. In this article, we compute and analyze many multiplicative degree-based topological indices of silicon-carbon Si2C3-I[p,q] and Si2C3-II[p,q].
Preprint
|
|
|
Materials Science, Nanotechnology; gold nanoparticles; citrate reduction method; pH-effect; concentration
Online: 5 June 2018 (09:49:45 CEST)
|
|
Share this article with
×
Gold nanoparticles (AuNPs) are currently under intense investigation for biomedical and biotechnology applications, thanks to their ease in preparation, stability, biocompatibility, multiple surface functionalities and size-dependent optical properties. The most commonly used method for AuNPs synthesis in aqueous solution is the reduction of tetrachloroauric acid (HAuCl4) with trisodium citrate. We observed variations in the pH and concentration of the gold colloidal suspension synthesized under standard conditions, verifying a reduction in the reaction yield by around 46% from pH 5.3 (2.4 nM) to pH 4.7 (1.29 nM). Citrate-capped AuNPs were characterized by UV-visible spectroscopy, TEM, EDS and zeta-potential measurements, revealing a linear correlation between pH and the concentration of the generated AuNPs. This result can be attributed to the adverse effect of protons both on citrate oxidation and on citrate adsorption onto the gold surface, which is required to form the stabilization layer. Overall, this study provides insight into the effect of the pH over the synthesis performance of the method, which would be of particular interest from the point of view of large-scale manufacturing processes.
Preprint
|
|
|
Materials Science, Biomaterials; biodegradable nanofibers; PLGA; masquelet technique
Online: 5 June 2018 (05:35:14 CEST)
|
|
Share this article with
×
Masquelet induced-membrane technique for the treatment of segmental bone defects includes a two-stage surgical procedure, and polymethylmethacrylate (PMMA) plays a major role in the treatment. However, the PMMA spacer must be surgically removed. Here, we investigated the potential of poly (lactic-co-glycolic acid) (PLGA) nanofibers, a biodegradable material to replace PMMA spacer, allowing the bioactive membrane to be induced, and the spacer to degrade without the additional surgery on a rabbit femoral segmental bone defect model. PLGA nanofibers were shown to degrade completely six weeks after implantation in the investigated animals, and a thick membrane was found to circumferentially fold around the segmental bone defects. Results from image studies demonstrated that, in the group without bone graft, all studied femurs exhibited either nonunion or considerable malunion. In contrast, the femurs in the bone graft group had a high union rate without considerable deformities. Histological examinations suggested that the membranous tissue in this group was rich in small blood vessels and the expression of BMP2 and VEGF increased. Our results demonstrate that the biodegradable PLGA nanofibers may be useful for replacing the PMMA spacer as the bioactive-membrane inducer, facilitating the process of healing and removing the need for repeated surgeries.
Preprint
|
|
|
Materials Science, Nanotechnology; magnetic nanoparticles; sodium polyacrylate; nanocomposites; draw solutes; forward osmosis
Online: 4 June 2018 (08:43:01 CEST)
|
|
|
Share this article with
×
Aqueous dispersions of magnetic nanocomposites have been proposed as draw electrolytes in forward osmosis. One possible approach for the production nanocomposites based on magnetite nanoparticles and sodium polyacrylate, is the synthesis of the magnetic iron oxide by coprecipitation or oxidative precipitation in presence of an excess of the polymer. In this work we explored the effect of the polymer proportion on the nanomaterials produced by these procedures. The materials obtained were compared s with the obtained by the coating of magnetite nanocrystals produced beforehand with the same polymer. The samples were characterized by chemical analysis, photon correlation spectroscopy, thermogravimetry, X-ray diffraction, infrared spectroscopy, transmission electron microscopy and magnetometry. The general trend observed is that part of the polymer is incorporated to the magnetic material during the synthesis heavily modifying its texture, with a drastic reduction of the particle size and magnetic response. The aqueous dispersions of the nanocomposites were highly stable with hydrodynamic size roughly independent on the polymer proportion. Their osmotic pressure proportional to the concentration of the polyelectrolyte, was similar than the generated by the equivalent amount of free polymer in the case of samples generated by oxidative precipitation and smaller in the case of samples generated by coprecipitation. Finally the possibilities of using these materials as draw electrolytes in forward osmosis will be briefly discussed.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; silicon; nanostructures; percolated networks; nanocomposites; thin films; laser processing; phase separation; liquid phase crystallization
Online: 4 June 2018 (08:10:30 CEST)
|
|
Share this article with
×
Three-dimensional nanocomposite networks consisting of percolated Si nanowires in a SiO2 matrix, Si:SiO2, were studied. The structures were obtained by reactive ion beam sputter deposition of SiOx (x ≈ 0.6) thin films at 450 °C and subsequent crystallization using conventional oven as well as millisecond line focus laser annealing. Rutherford backscattering spectrometry, Raman spectroscopy, X-ray diffraction, cross-sectional and energy-filtered transmission electron microscopy were applied for sample characterization. While oven annealing resulted in a mean Si wire diameter of 10 nm and a crystallinity of 72 % within the Si volume, almost single-domain Si structures with 30 nm in diameter and almost free of amorphous Si were obtained by millisecond laser application. The structural differences are attributed to the different crystallization processes: Conventional oven tempering proceeds via solid state, millisecond laser application via liquid phase crystallization of Si. The 5 orders of magnitude larger diffusion constant in the liquid phase is responsible for the three times larger Si nanostructure diameter. In conclusion, laser annealing offers not only significantly shorter process times but moreover a superior structural order of nano-Si compared to conventional heating.
Preprint
|
|
|
Materials Science, Nanotechnology; Pt-Cu; porous; electrocatalyst; HER; synergetic effect
Online: 1 June 2018 (12:57:52 CEST)
|
|
|
Share this article with
×
Cost-efficient catalyst for hydrogen evolution reaction (HER) and methanol oxidization reaction (MOR) is of great importance for industrial application. The alloying of platinum with cheap transition metal offers a great opportunity to reduce cost and enhance the electro-catalytic performance. Herein, we report a simple and green route to synthesize porous Pt-Cu catalysts, where Pt-Cu solid particles were first produced by using cuprous chloride (CuCl) nanoparticles as the template, followed by a dealloying treatment to obtain final porous product. The porous alloy nanoparticles show higher catalytic activity and superior stability for HER and methanol oxidation reaction, which is beneficial from the porous structure and synergetic effect between Pt and Cu.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; electron microscopy; energy dispersive X-ray spectroscopy (EDX); electron energy loss spectroscopy (EELS); worn surface analysis; tribofilms
Online: 31 May 2018 (11:27:10 CEST)
|
|
Share this article with
×
Friction and wear take place on two solid surfaces in sliding contact as a result of the mechanical, thermal and chemical interactions with the participation of environmental species. Electron microscopy and the associated spectroscopic analyses are powerful in probing these mechanisms in spatial resolutions from micro to atomic scale. This article provides a review of the author’s work in the wear and friction mechanisms of PVD hard coatings in which various SEM- and TEM-based microscopic and spectroscopic techniques were employed. Understanding on the failure mechanisms and the origin of self-adaptive friction has been improved to nano-scale. Other related issues are also discussed, such as sample preparation techniques for cross-sectional electron microscopy, energy dispersive X-ray spectroscopy and electron energy loss spectroscopy.
Preprint
|
|
|
Materials Science, Polymers & Plastics; polymerization theory; photo polymerization kinetic; photoinitiation rate; polymerization efficacy; photodynamic therapy.
Online: 31 May 2018 (11:25:02 CEST)
|
|
Share this article with
×
The kinetics and optimal efficacy conditions of photoinitiated polymerization are theoretically presented. Analytic formulas are derived for the crosslink time, crosslink depth and efficacy function. The roles of photosensitizer (PS)
concentration, diffusion depth and light intensity on the polymerization spatial and temporal profiles, for both uniform and non-uniform cases, are presented . For optimal efficacy, a strategy via controlled PS concentration is proposed, where re-supply of PS in high light intensity may achieve a combined-efficacy similar to low light intensity, but has a much faster procedure. A new criterion of efficacy based on the polymerization (crosslink) [strength] and [depth] is introduced.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; graphene synthesis; silicon carbide; thin film; high-power impulse magnetron sputtering; thermal decomposition, electronic devices
Online: 30 May 2018 (08:22:05 CEST)
|
|
Share this article with
×
This article reports a novel and efficient method to synthesize graphene by thermal decomposition process. In this method, silicon carbide (SiC) thin films grown on Si(100) wafers with an AlN buffer layer were used as substrates. A CO2 laser beam heating without vacuum or controlled atmosphere was applied for SiC thermal decomposition. The physical, chemical, morphological, and electrical properties of the laser-produced graphene were investigated for different laser energy densities. The results demonstrate that graphene was produced in form of small islands with quality, density and properties depending on the applied laser energy density. Furthermore, the produced graphene exhibits a sheet resistance characteristic similar to graphene grown on mono-crystalline SiC wafer, which indicates its potential for electronic device applications.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; direct surface activation; low-temperature vacuum carburization; expanded austenite; supersaturation; acetylene
Online: 30 May 2018 (06:23:47 CEST)
|
|
Share this article with
×
The effect of the acetylene and hydrogen gases mixture ratios in direct low-temperature vacuum carburization was investigated. The gas ratio is an important parameter for producing the free radicals in the carburization. The free radicals can remove the natural oxide film by the strong reaction of the hydrocarbons, and then thermodynamically activity can be increased. When the gas ratio was below 1, the supersaturation expanded austenite layers were formed on the surface of the AISI 316L stainless steel, which had the maximum carbon solubility up to 11.5 at.% at 743 K, were formed. On the other hand, when the gas ratio was above 1, the carbon concentration of them remained low even if the process time was enough increased to reach the maximum carbon solubility. As a result, the carbon concentration underneath the surface was determined to be highly dependent on the gas mixture ratio of acetylene and hydrogen. In conclusion, it is necessary to restrict the ratio of acetylene and hydrogen gases to total mixture gases to form the expanded austenite layer with the high carbon concentration in the direct low-temperature vacuum carburization.
Preprint
|
|
|
Materials Science, General Materials Science; metal-organic gels; doxorubicin loading and release; pH-responsiveness; anticancer effect
Online: 30 May 2018 (05:01:21 CEST)
|
|
|
Share this article with
×
Slow and controlled release systems for drugs, have attracted increasing interest recently. A highly efficient metal-organic gels (MOGs) drug delivery carrier, i.e., MIL-100(Al) gels, has been fabricated by a facile, low cost and environment friendly one-pot process. The unique structure of MIL-100(Al) gels leads to a high loading efficiency (620 mg/g) towards doxorubicin hydrochloride (DOX) as a kind of anticancer drugs. DOX-loaded MOGs exhibited high stability under physiological conditions and sustained release capacity of DOX for up to 3 days (under acidic environments). They further showed sustained drug release behavior and excellent antitumor effects in in vitro experiments on HeLa cells, in contrast with the extremely low biotoxicity of MOGs. Our work provides a promising way for the anticancer therapy, by utilizing this MOGs-based drug delivery system, as an efficient and safe vehicle.
Preprint
|
|
|
Materials Science, Biomaterials; shielding agent; polysarcosine; biodistribution; click-chemistry; lipopolyplex; nucleic acid carrier
Online: 29 May 2018 (10:39:48 CEST)
|
|
Share this article with
×
Shielding agents are commonly used to shield polyelectrolyte complexes, e.g. polyplexes, from agglomeration, precipitation in complex media, like blood, and thus enhance their circulation times in vivo. Since up to now primarily poly(ethylene glycol) (PEG) has been investigated to shield non-viral carriers for systemic delivery, we report on the use of polysarcosine (pSar) as a potential alternative for steric stabilization. A redox-sensitive, cationizable lipo-oligomer structure (containing two cholanic acids attached via a bioreducible disulfide linker to an oligoaminoamide backbone in T-shape configuration) was equipped with azide-functionality by solid phase supported synthesis. After mixing with small interfering RNA (siRNA), lipopolyplexes formed spontaneously and were further surface-functionalized with polysarcosines. Polysarcosine was synthesized by living controlled ring-opening polymerization using an azide-reactive dibenzo-aza-cyclooctyne-amine as an initiator. The shielding ability of the resulting formulations was investigated with biophysical assays and by near-infrared fluorescence bioimaging in mice. The modification of ~100 nm lipopolyplexes was only slightly increased upon functionalization. Cellular uptake into cells was strongly reduced by the pSar shielding. Moreover, polysarcosine-shielded polyplexes showed enhanced blood circulation times in bioimaging studies compared to unshielded polyplexes and similar to PEG-shielded polyplexes. Therefore, polysarcosine is a promising alternative for the shielding of non-viral, lipo-cationic polyplexes.
Preprint
|
|
|
Materials Science, Metallurgy; SA213-T23; cr-mo steel; CGHAZ; PWHT cracking; intergranular ferrite; Tint etching
Online: 28 May 2018 (15:44:20 CEST)
|
|
Share this article with
×
The post-weld heat treatment (PWHT) cracking susceptibility of a coarse grain heat-affected zone (CGHAZ) in SA213-T23 (2.25Cr-1.6W steel), used for boiler tubes employed in thermal power plants, was investigated using a Gleeble thermal cycle simulator. The PWHT cracking susceptibility test was performed at 650℃, 700℃ and 750℃, and it can be judged that the lower the reduce of area, the more susceptible it is to PWHT cracking. The results of the test also showed higher cracking susceptibility at 650℃ and 700℃, mostly involving intergranular fracture, while at 750℃, transgranular fracture was exhibited. Therefore, the PWHT cracking susceptibility is considered to be closely related to grain boundary. The microstructure of the simulated CGHAZ and PWHT at 650℃, 700℃and 750℃ was observed after etching with nital and alkaline sodium picrate etchants. Alkaline sodium picrate etched microstructures showed a white band at the grain boundary at 650℃, 700℃ and 750, that did not appear in nital etching. Analysis of the white band using EPMA, TEM and nanoindentation revealed that it was intergranular ferrite depleted with C, W and Cr as compared to that in the matrix. Based on these results, we investigated the mechanism of intergranular ferrite formation during PWHT and its effect on PWHT cracking susceptibility at 650℃, 700℃ and 750℃.
Preprint
|
|
|
Materials Science, Nanotechnology; graphene; cold field emission; single-tip cathode; electron microscopy
Online: 28 May 2018 (09:02:44 CEST)
|
|
Share this article with
×
Although good field emission from graphene has been demonstrated from a wide variety of different microfabricated structures, very few of them can be used to improve the design of cold field emitters for electron microscopy applications. Most of them consist of densely packed nano-emitters, which produce a large array of defocused overlapping electron beams, and therefore cannot be subsequently focused down to a single nanometer electron probe. This paper reviews the kind of single-tip cathode structures suitable in cold field emission guns for instruments such as scanning electron microscopy, transmission electron microscope or scanning transmission electron microscopy, and reviews progress in fabricating them from graphene-based materials.
Preprint
|
|
|
Materials Science, Metallurgy; titanium; strain hardening; anisotropy; strain heterogeneity; acoustic emission; statistical analysis; collective dislocation dynamics
Online: 25 May 2018 (15:41:14 CEST)
|
|
Share this article with
×
Current progress in the prediction of mechanical behavior of solids requires understanding of spatiotemporal complexity of plastic flow caused by self-organization of crystal defects. It may be particularly important in hexagonal materials because of their strong anisotropy and combination of different mechanisms of plasticity, such as dislocation glide and twinning. These materials often display complex behavior even on the macroscopic scale of deformation curves, e.g., a peculiar three-stage elastoplastic transition, the origin of which is a matter of debates. The present work is devoted to a multiscale study of plastic flow in α-Ti, based on simultaneous recording of deformation curves, 1D local strain field, and acoustic emission (AE). It is found that the average AE activity also reveals three-stage behavior, but in a qualitatively different way depending on the crystallographic orientation of the sample axis. On the finer scale, the statistical analysis of AE events and local strain rates testifies to an avalanche-like character of dislocation processes, reflected in power-law probability distribution functions. The results are discussed from the viewpoint of collective dislocation dynamics and are confronted to predictions of a recent micromechanical model of Ti strain hardening.
Preprint
|
|
|
Materials Science, Metallurgy; Additive manufacturing; Maraging steel; Microstructure; Martensite structure; Orientation relationship; electron backscattering diffraction (EBSD)
Online: 25 May 2018 (15:26:43 CEST)
|
|
Share this article with
×
This study characterizes the microstructure and its associated crystallographic features of bulk maraging steels fabricated by selective laser melting (SLM) combined with a powder bed technique. The fabricated sample exhibited characteristic melt pools in which the regions had locally melted and rapidly solidified. A major part of these melt pools corresponded with the ferrite (alpha) matrix, which exhibited a lath martensite structure with a high density of dislocations. A number of fine retained austenite (gamma) with a <001> orientation along the build direction was often localized around the melt pool boundaries. The orientation relationship of these fine gamma grains with respect to the adjacent alpha grains in the martensite structure was (111) gamma // (011) alpha and [-101] gamma // [-1-11] apha (Kurdjumov–Sachs orientation relationship). Using the obtained results, we inferred the microstructure development of maraging steels during the SLM process. The results depict that new and diverse high-strength materials can be used to develop industrial molds and dies.
Preprint
|
|
|
Materials Science, Biomaterials; pretreated cellulosic biomass; critical point drying; surface area; pore size distribution; Brunauer-Emmett-Teller; cellulose; hornification
Online: 25 May 2018 (11:57:19 CEST)
|
|
Share this article with
×
Surface area and pore size distribution of Eucalyptus samples pretreated by different methods were determined by the Brunauer-Emmett-Teller (BET) technique. Three methods were applied to prepare cellulosic biomass samples for BET measurements: air, freeze, and critical point drying (CPD). Air and freeze drying caused severe collapse of biomass pore structures, but CPD effectively preserved biomass morphology. Surface area of CPD prepared Eucalyptus samples was determined to be 58–161 m2/g, whereas air and freeze dried samples were 0.5–1.3 and 1.0–2.4 m2/g, respectively. Average pore diameter of CPD prepared Eucalyptus samples were 61–70Å. CPD preserved Eucalyptus sample morphology by replacing water with a non-polar solvent, CO2 fluid, which prevented hydrogen bond reformation in the cellulose.
Preprint
|
|
|
Materials Science, Biomaterials; haemoglobin detection; SPR spectroscopy; biosensors; computer simulation; core-shell Fe3O4@Au
Online: 25 May 2018 (10:02:27 CEST)
|
|
|
Share this article with
×
A theoretical analysis of haemoglobin (Hb) concentration detection is presented in this work with the objective of achieving more sensitive detection and monitoring low concentrations. Surface-enhanced SPR spectroscopy on silver nanoparticles was employed for recording Hb concentrations less than 10 g/L. In this paper, Fe3O4@Au core-shell, nanocomposite spherical nanoparticle consisting of a spherical Fe3O4 core covered by Au shell, was used as an active material for biomolecules detection in the Surface Plasmon Resonance (SPR)-based biosensor in the wavelength 632.8 nm. We present the simulation of detection amplification technique through Attenuated Total Reflection (ATR) spectrum in the Kretschmann configuration. The system consists of a four-layer material i.e prism/Ag/Fe3O4@Au+Hb/air. Dielectric function determination of the core-shell nanoparticle (Fe3O4@Au) and the composite (Fe3O4@Au+Hb) was done by applying the Effective Medium Theory approximation and the calculation of the reflectivity is carried out by varying the size of core-shell (r0). In this simulation, the refractive index of the BK7 prism is 1.51; the refractive index of Ag thin film is 0.13455+3.98651i with the thickness of 40 nm, and the refractive index of the composite is varied depending on the size of nanoparticle core-shell. Our results show that by varying the radius of the core and the shell thickness, the dip of the reflectivity (ATR) spectrum is shifted to the larger angle of incident light and the addition of core-shell in the conventional SPR-based biosensor leads to enhancement of the SPR biosensor sensitivity, for the core-shell radius 10 nm, the sensitivity increased by 1.35% for F = 0.1, and by 4.89% for F =0.8 compared to the sensitivity of the conventional SPR-based biosensor without core-shell addition.
Preprint
|
|
|
Materials Science, Biomaterials; 316L; electrodeposition; nano-hydroxyapatite; carbon nanotubes; osteoblasts; gene expression
Online: 24 May 2018 (06:18:52 CEST)
|
|
Share this article with
×
Herein, we evaluated the electrophoretic deposition of nanohydroxyapatite/superhydrophilic multiwalled carbon nanotube composites (nHAp/MWCNT) onto stainless steel biomedical alloys for applications in bone tissue engineering. First, nHAp/MWCNT composites were dispersed into 0.042 mol L−1 of Ca(NO3)2·4H2O + 0.025 mol L−1 NH4H2PO4 electrolytes (pH = 4.8) at two different concentrations. Next, a voltage of −2 V was applied using 316L stainless steel as a working electrode and (0.27 cm2), a high-purity platinum coil wire as the auxiliary electrode, and an Ag/AgCl(3 M) electrode was used as the reference electrode. The nHAp/MWCNT composites were characterized by transmission electron microscopy. The deposited nHAp and nHAp/MWCNT films were characterized by profilometry, scanning electron microscopy, X-Ray diffractometry and Raman spectroscopy. Human osteoblast cells were cultivated with the different materials, and in vitro cytotoxicity was evaluated using lactate dehydrogenase (LDH) assay. The osteogenesis process was evaluated by mRNA levels of the three genes that are directly related to bone repair: Alkaline Phosphatase, Osteopontin and Osteocalcin. We showed that rough, crystalline apatite thin films containing phases of nHAp were successfully deposited onto 316L stainless steel alloys. Also, we noticed that nHAp/MWCNT thin films deposited onto 316L stainless steel alloys upregulated the expression of important genes related to bone mineralization and maturation. Our results strongly support the possibility of this new alternative to modify the surface of metallic biomedical alloys to promote bone tissue regeneration.
Preprint
|
|
|
Materials Science, Other; ultra-dilution; droplets; water; evaporation; X-ray fluorescence
Online: 24 May 2018 (05:43:52 CEST)
|
|
Share this article with
×
The analysis of particulate matter (PM) in dilute solutions is an important target for environmental, geochemical and biochemical researches. Here we show how the microdrop technology may allow to control, through the evaporation of small droplets, the deposition of insoluble materials dispersed in a solution on a well-defined area with a specific spatial pattern. Using this technology the superficial density of the deposited solute can be accurately controlled. In particular, it becomes possible to deposit an extremely reduced amount of insoluble material -in the order of few μg- on a confined area, thus allowing a relatively high superficial density to be reached within a limited time. In this work we quantitatively compare the microdrop technique for the preparation of particulate matter samples with the classical filtering technique. After having been optimized, the microdrop technique allows to obtain a more homogeneous deposition and limit sample consumption of a factor ~25. This method is potentially suitable for many novel applications in different scientific fields.
Preprint
|
|
|
Materials Science, Metallurgy; laser beam, T-joints, weldability, TMCP steel
Online: 22 May 2018 (05:47:25 CEST)
|
|
Share this article with
×
The article presents tests aimed to verify the possibility of making T-joints in TMCP steel using laser. The tests involved the use of 10 mm thick high yield point steel S700MC obtained in an industrial manufacturing process. The joints made in the tests were single and double-sided. Subsequent non-destructive tests revealed that the joints obtained in the tests represented quality level B in accordance with PN-EN ISO 13919-1. Single-sided welding performed using the laser beam having a power of 11 kW enabled the obtainment of 8 mm deep penetration without visibly deforming the web of the joint. The double-sided welded joints were characterised by proper geometry and the presence of gas pores in the welds not compromising the requirements of quality level B (strict requirements). The weld structure was bainitic-ferritic. The weld hardness was by approximately 60 HV1 higher than that of the base material (280 HV1). The HAZ area was slightly softer than the base material. The tests of thin foils performed using a high-resolution scanning transmission electron microscope revealed that, during welding, an increase in the content of the base material in the weld was accompanied by an increase in contents of alloying microagents Ti and Nb, particularly near the fusion line. The above-named alloying microagents, in the form of fine-dispersive (Ti,Nb)(C,N) type precipitates, could reduce plastic properties of joints.
Preprint
|
|
|
Materials Science, Biomaterials; poly(butylene succinate-co-adipate); zinc phenylphosphonate; nanocomposites; crystallization; biodegradation
Online: 21 May 2018 (11:40:10 CEST)
|
|
Share this article with
×
Biocompatible and biodegradable poly(butylene succinate-co-adipate) (PBSA)/hexadecylamine-modified PPZn (m-PPZn) nanocomposites were prepared using a melt mixing process. Experimental results of wide-angle X-ray diffraction and transmission electron microscopy revealed that the stacking layers of the m-PPZn were partially intercalated and partially exfoliated into the PBSA polymer matrix. The isothermal crystallization kinetics of PBSA/m-PPZn nanocomposites were studied at the temperature range of 62−70 °C and the half-time for crystallization of 3 wt % PBSA/m-PPZn nanocomposite was reduced by 27−35% compared with that of pure PBSA. This finding suggests that the incorporation of m-PPZn might cause the heterogeneous nucleation and the subsequent crystallization growth, which enhances the isothermal crystallization rate of PBSA/m-PPZn nanocomposite. The biodegradation rates of PBSA using Lipase from Pseudomonas sp. increase as the contents of m-PPZn increase. The degradation behavior of the neat PBSA investigated using the change of weight-average molecular weight belongs to exo-type hydrolysis activity. It is necessary to point out that the change of degree of crystallinity and degradation rate are almost linearly proportional to the loading of hexadecylamine-modified PPZn. This finding would provide an important information for the manufacturing biodegradable PBSA nanocomposites.
Preprint
|
|
|
Materials Science, General Materials Science; ionic liquids; ionic liquid-assisted solvothermal reaction; reaction time; titanium dioxide; heterogeneous photocatalysis; visible light
Online: 15 May 2018 (09:10:42 CEST)
|
|
Share this article with
×
Spherical microparticles of TiO2 were synthesized by the ionic liquid-assisted solvothermal method at different reaction time (3, 6, 12 and 24h). The properties of the prepared photocatalysts were investigated by means of UV-vis diffuse-reflectance spectroscopy (DRS), BET surface area measurements, scanning electron microscopy (SEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that the efficiency of phenol degradation was related with a time of the solvothermal synthesis as determined for TiO2_EAN(1:1)_24h sample. Microparticles of TiO2_EAN(1:1)_3h formed during the only 3h of synthesis time revealed really high photoactivity under visible irradiation – 75%. This value increased to 80% and 82% after 12h and 24h, respectively. The photoactivity increase was accompanied by the increase of the specific surface area thus pores size, as well as ability to absorb UV-vis irradiation. The high efficiency of phenol degradation of IL-TiO2 photocatalysts was ascribed to the interaction between the surface of TiO2 and ionic liquid components (carbon and nitrogen).
Preprint
|
|
|
Materials Science, Polymers & Plastics; polymer electrolyte; single-ion conducting; ionic conductivity; Raman spectroscopy
Online: 15 May 2018 (08:45:58 CEST)
|
|
Share this article with
×
Solvent-free, single-ion conducting electrolytes are sought after for use in electrochemical energy storage devices. Here, we investigate the ionic conductivity and how this property is influenced by segmental mobility and conducting ion number in crosslinked single-ion conducting polyether-based electrolytes with varying tethered anion and counter-cation types. Crosslinked electrolytes are prepared by the polymerization of poly(ethylene glycol) diacrylate (PEGDA), poly(ethylene glycol) methyl ether acrylate, and ionic monomers. The ionic conductivity of the electrolytes is measured and interpreted in the context of differential scanning calorimetry and Raman spectroscopy measurements. A lithiated crosslinked electrolyte prepared with PEG31DA and STFSI monomers is found to have a lithium ion conductivity of 3.2 × 10-6 and 1.8 × 10−5 S/cm at 55 and 100 °C, respectively. The percentage of unpaired anions for this electrolyte was estimated at about 23% via Raman spectroscopy. Despite the large variances in metal cation – STFSI binding energies as predicted via DFT and large variations in ionic conductivity, STFSI-based crosslinked electrolytes with the same charge density and varying cations (Li, Na, K, Mg, and Ca) were estimated to all have unpaired anion populations in the range of 19 to 29%.
Preprint
|
|
|
Materials Science, Nanotechnology; fluorescent magnetic submicronic polymer nanoparticles; human breast cancer; MCF-7 cell line; anticancer; cytotoxicity; in vitro cell culture
Online: 15 May 2018 (06:25:09 CEST)
|
|
Share this article with
×
Breast cancer treatment mostly revolved around radiation therapy and surgical interventions, these treatments doesn’t provide satisfactory relief to the patients and carry unmanageable side-effects. Nanomaterials show promising results in treating cancer cells and have many advantages such as high biocompatibility, bioavailability and effective therapeutic capabilities. Interestingly, fluorescent magnetic nanoparticles have been used in many biological and diagnostic applications, but there is no report of use of fluorescent magnetic submicronic polymer nanoparticles (FMSP-nanoparticles) in the treatment of human breast cancer cells. In the present study, we have tested the effect FMSP-nanoparticles on human breast cancer cells (MCF-7). We have tested different concentrations (1.25µg/1mL, 12.5µg/mL and 50µg/1mL) of FMSP-nanoparticles in MCF-7 cells and evaluated the nanoparticles response morphometrically. Our results revealed that FMSP-nanoparticles produced a concentration dependent effect on the cancer cells, dose of 1.25µg/mL produced no significant effect on the cancer cell morphology and cell death, whereas dosages of 12.5µg/mL and 50µg/mL respectively showed significant nuclear augmentation, disintegration, chromatic condensation followed by dose dependent cell death. Our results demonstrate FMSP-nanoparticles have ability to induce cell death in MCF-7 cells and may be considered as a potential anti-cancer agent for breast cancer treatments.
Preprint
|
|
|
Materials Science, Nanotechnology; nanohybrid; synthesis; standard electron potential; crystal phase; reducing agents
Online: 14 May 2018 (11:51:21 CEST)
|
|
|
Share this article with
×
Carbon nanotubes are hybridized with metal crystals to impart multifunctionality into the nanohybrids (NHs). Simple but effective synthesis techniques are desired to form both zero-valent and oxides of different metal species on carbon nanotube surfaces. Sol-gel technique brings in significant advantages and is a viable technique for such synthesis. This study probes the efficacy of sol-gel process and aims to identify underlying mechanisms of crystal formation. Standard electron potential (SEP) is used as a guiding parameter to choose the metal species; i.e., highly negative SEP (e.g., Zn) with oxide crystal tendency, highly positive SEP (e.g., Ag) with zero-valent crystal-tendency, and intermediate range SEP (e.g., Cu) to probe the oxidation tendency in crystal formation are chosen. Transmission electron microscopy and X-ray diffraction are used to evaluate the synthesized NHs. Results indicate that SEP can be a reliable guide for the resulting crystalline phase of a certain metal species, particularly when the magnitude of this parameter is relatively high. However, for intermediate range SEP-metals, mix phase crystals can be expected. For example, Cu will form Cu2O and zero-valent Cu crystals, unless the synthesis is performed in a reducing environment.
Preprint
|
|
|
Materials Science, Metallurgy; ferrite; carbide; bainite; continuous cooling transformation (CCT) curve; charpy impact test
Online: 14 May 2018 (10:29:18 CEST)
|
|
Share this article with
×
2.25Cr-1Mo steel with high strength at high temperatures and good hydrogen resistance is widely used for power generation boiler material in high temperature and pressure use environments. Following the test evaluation of the ASME Boiler and Pressure Vessel Code, specimens from the base metal of a boiler pipe were found to have impact toughness values of 285 and 21 ft-lb, which are drastically different values. The analysis of the fracture surface of the 21 ft-lb test specimen revealed MnS inclusions, and it was found that cracks initiated at the inclusions. Observation of the cross-section of the crack propagation front revealed that cracks propagated along the ferrite regions and precipitate voids. Inclusions were also found in the 285 ft-lb impact specimen; however, the volume fraction of the inclusions was significantly less than that of the 21 ft-lb specimen. It was also found that the ferrite and carbide content of the 285 ft-lb specimen was less than 21 ft-lb specimen. The reason that the inclusions, ferrite, and carbide content differed in the two adjacent impact test specimens was analyzed. The effects of micro-segregation, such as MnS inclusions on ferrite and carbide, were compared and analyzed.
Preprint
|
|
|
Materials Science, Biomaterials; Caenorhabditis elegans; toxicity; gold nanoparticles; nanocomposites; Lectin Protein; ROS
Online: 9 May 2018 (08:11:49 CEST)
|
|
Share this article with
×
The lectin found in the tubers of the Winter Aconite (Eranthis hyemalis) plant (EHL) is a Type II Ribosome Inactivating Protein (RIP); type II RIPs have shown anti-cancer properties, and have great potential as therapeutic agents. Similarly, colloidal gold nanoparticles are successfully used in biomedical applications as gold nanoparticles can be functionalised with ligands with high affinity and specificity for target cells to create therapeutic and imaging agents. Herein we present the synthesis and characterization of gold nanoparticles conjugated with EHL. The aim was to establish the viability of the conjugate and perform a set of initial assays to establish whether the biological effect of EHL is altered by the conjugation. The biological assays were performed in Caenorhabditis elegans, a free living nematode commonly used for toxicological studies; previous work from some of the authors using first life stage (L1) nematodes has shown that EHL has a strong biocidal effect on C. elegans. Gold nanoparticles functionalised with EHL (AuNPs@EHL) were successfully synthesised by bioconjugation with citrate gold nanoparticles (AuNPs@Citrate); the conjugates were analysed by UV-Vis spectroscopy, Dynamic Light Scattering (DLS), Zeta Potential analysis and Transmission Electron Microscopy (TEM). Results indicate that an optimal functionalisation was achieved with the addition of 100 µL of EHL (concentration 1090 ± 40 µg/mL) over 5 mL of AuNPs (concentration [Au0] = 0.8 mM). Biological assays on the effect of AuNPs@EHL on C. elegans were performed, using first life stage (L1) and pre-adult stage (L4) nematodes. Citrate gold nanoparticles did not have any obvious effect on the nematodes. For L1 stage nematodes, the assays show that conjugation with gold nanoparticles reduced the biological effect of EHL on C. elegans. As lectin binding activity is essential for the natural protein to bind and allow entry to cells, conformational changes due to conjugation may have affected this binding affinity. For L4 stage nematodes, both EHL alone and AuNPs@EHL showed biological activity, and reproductive delays and reduced fecundity were observed in both cases. These assays indicate that EHL can be conjugated to gold nanoparticles and retain elements of biocidal activity.
Preprint
|
|
|
Materials Science, Polymers & Plastics; natural rubber; GO-NH-MCM-41; graphene oxide; mesoporous; intumescent flame retardants
Online: 9 May 2018 (05:50:26 CEST)
|
|
Share this article with
×
Aiming to improve the flame retardancy performance of natural rubber (NR), we developed a novel flame retardant synergistic agent through grafting of MCM-41 to graphene oxide (GO)，named as GO-NH-MCM-41，as an assistant of intumescent flame retardants (IFR). The structure of GO-NH-MCM-41 was characterized by FTIR, TEM and SEM tests, which confirmed that a fine grafting had been applied between GO and MCM-41. The flame retardancy of NR/IFR/GO-NH-MCM-41 composites was evaluated by limited oxygen index (LOI), UL-94 and cone calorimeter test. The LOI value of NR/IFR/GO-NH-MCM-41 reached to 26.3%; the UL-94 ratings improved to V-0 rating. Moreover, the addition of GO-NH-MCM-41 obviously decreased the peak heat release rate (PHRR) and the total heat release (THR) of the natural rubber composites. And the addition of GO-NH-MCM-41 increased the thickness of char residue. The images of SEM indicated the char residue were more compact and continuous. The degradation of GO-NH-MCM-41 based NR composites completed with a mass loss of 35.57% at 600 ℃. The tensile strength and the elongation at break of NR/IFR/GO-NH-MCM-41 composites were 13.9 MPa and 496.7%, respectively. The results of rubber process analyzer (RPA) reached the maximum value, probably due to a better network of the fillers in the matrix.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; stone; nanocomposite; protective coating; electrokinetic characterization; Zeta potential; isoelectric point; alkyl alkoxysilane; contact angle; water absorption; surface modification
Online: 8 May 2018 (10:01:28 CEST)
|
|
Share this article with
×
The characterization of protective coatings applied on natural stones is often a complex task due to the difficulty of identifying and quantifying the various factors contributing to the overall behaviour of the coating-stone system. In particular, linking information about the coating-stone interaction to macroscopic effects in terms of physical behaviour of treated stones can be especially arduous owing to the inherent structural complexity of stone substrates. Electrokinetic analysis based on streaming current measurements, having already proved the ability to sense even minor changes in the chemical composition of different materials surfaces upon treatment, may provide useful insights in view of better understanding the extent of stone surface modification. In particular, involving the interaction of stones with a water-based solution, the streaming current technique could extend the characterization of stone surface to the outermost part of the pore network, which is part of every treatment-induced modification of surface properties. In this work, the effectiveness of streaming current measurements as analytical tool for the characterization of coatings applied on natural stones is assessed by considering different lithotypes and coatings and trying to correlate the results of electrokinetic analysis with the physical behaviour of treated stones, with specific regard to wettability and capillary water absorption.
Preprint
|
|
|
Materials Science, Biomaterials; biomass; biochar; activation; activated carbon; thermal treatment, physical activation; porosity, specific surface areas
Online: 7 May 2018 (10:30:25 CEST)
|
|
Share this article with
×
Activated carbons (ACs) can be produced from biomass in a thermal process either in a direct carbonization-activation process or first by carbonizing the biomass and later on activating the biochars into activated carbons. The properties of the ACs are dependent on the type of process used for production. In this study, the properties of activated carbons produced in a one-stage and a two-stage process are considered. Activated carbons were produced by physical activation of two types of starting materials, biochars produced from spruce and birch chips in a commercial carbonization plant and from the corresponding raw chips. The activated carbons produced were characterized regarding specific surfaces, pore volumes and pore size distributions. The unactivated biochars had some degree of surface area and some porosity. According to the results obtained, two slightly different types of activated carbons are produced depending if a one-stage or a two-stage carbonization and activation process is used. The ACs produced in the one-stage process had higher specific surface areas compared to the ones produced in a two-stage process. In addition, total pore volumes were higher in one-stage process but development of micropores is greater compared to two-stage process. There was no significant difference in total carbon content between one-stage and two-stage process.
Preprint
|
|
|
Materials Science, Biomaterials; Peptide; self-assembly; nanomaterial; hydrogel; aspergillosis; candidiasis.
Online: 4 May 2018 (12:58:24 CEST)
|
|
|
Share this article with
×
The threat of antimicrobial resistance to society is compounded by a relative lack of new clinically effective licensed therapies reaching patients over the past three decades. This has been particularly problematic within antifungal drug development leading to a rise in fungal infection rates and associated mortality. This paper highlights the potential of an ultrashort peptide, (naphthalene-2-ly)-acetyl-diphenylalanine-dilysine-OH (NapFFKK-OH), encompassing hydrogel-forming and antifungal properties within a single peptide motif, thus overcoming formulation (e.g. solubility, drug loading) issues associated with many current employed highly hydrophobic antifungals. A range of fungal susceptibility (colony counts) and cell cytotoxicity (MTS cell viability, LIVE/DEAD staining® with fluorescent microscopy, haemolysis) assays were employed. Scanning electron microscopy confirmed the nanofibrous architecture of our self-assembling peptide, existing as a hydrogel at concentrations of 1% w/v and above. Broad-spectrum activity was demonstrated against a range of fungi clinically relevant to infection (Aspergillus niger, Candida glabrata, Candida albicans, Candida parapsilosis and Candida dubliniensis) with greater than 4 log10 CFU/mL reduction at concentrations of 0.5% w/v and above. We hypothesise antifungal activity is due to targeting of anionic components present within fungal cell membranes resulting in membrane disruption and cell lysis. NapFFKK-OH demonstrated reduced toxicity against mammalian cells (NCTC 929, ARPE-19) suggesting increased selectivity for fungal cells. However, further studies relating to safety for systemic administration is required, given the challenges toxicity has presented in the wider context of antimicrobial peptide drug development. Overall this study highlights the promise of NapFFKK-OH hydrogels, particularly as a topical formulation for the treatment of fungal infections relating to the skin and eyes, or as a hydrogel coating for the prevention of biomaterial related infection.
Preprint
|
|
|
Materials Science, Polymers & Plastics; immiscible blend; compatibilization; homogeneous phase; alcoholysis; carbonyl group; copolymers
Online: 3 May 2018 (07:57:59 CEST)
|
|
Share this article with
×
An immiscible blend of poly(hydroxy ether of bisphenol-A) (phenoxy) and poly(1,4-butylene terephthalate) (PBT) with phase separation was observed in as-blended samples. However, compatibilization of the phenoxy/PBT blends can be promoted through chemical exchange reactions of phenoxy with PBT upon annealing. In contrast to the as-blended samples, the annealed phenoxy/PBT blends had a homogeneous phase with a single Tg that could be enhanced by annealing at 260°C. Infrared (IR) spectroscopy demonstrated that phase homogenization could be promoted by annealing of the phenoxy/PBT blend, where alcoholytic exchange occurred between the dangling hydroxyl group in phenoxy and the carbonyl group in PBT in the heated blends. The alcoholysis reaction changes the aromatic linkages to aliphatic linkages in carbonyl groups, which initially led to the formation of a graft copolymer of phenoxy and PBT with an aliphatic/aliphatic carbonyl link. The progressive alcoholysis reaction resulted in the transformation of the initial homopolymers into block copolymers and finally into random copolymers, which promoted phase compatibilization in blends of phenoxy with PBT. Due to the fact that the amount of copolymers increased upon annealing, crystallization of PBT was inhibited by alcoholytic exchange in the blends.
Preprint
|
|
|
Materials Science, Polymers & Plastics; fibrous composites; longitudinal molulus; upper bound; strength of materials; interphase
Online: 2 May 2018 (12:42:48 CEST)
|
|
Share this article with
×
In this paper, an upper bound of the longitudinal elastic modulus of unidirectional fibrous composites is proposed according to strength of materials approach, on the premise that the fiber is much stiffer than the matrix. In the mathematical derivations, the concept of boundary interphase between fiber and matrix was also taken into account and the main objective of this work is the attainment of an upper bound for the interphase stiffness with respect to fiber concentration by volume. The novel element here is that the authors have not taken into consideration any specific variation law to approximate the interphase modulus. The theoretical results arising from the proposed formula were compared with those obtained from some reliable theoretical models as well as with experimental data found in the literature, and a satisfactory agreement was observed.
Preprint
|
|
|
Materials Science, Nanotechnology; BaTiO3; hydrothermal synthesis; in situ; X-ray diffraction; nanoparticles
Online: 2 May 2018 (11:25:23 CEST)
|
|
|
Share this article with
×
Ferroelectric materials are crucial for today’s technological society, and nanostructured ferroelectric materials are important for downscaling of devices. Controlled and reproducible synthesis of these materials are therefore of immense importance. Hydrothermal synthesis is a well-established synthesis route, with a large parameter space for optimization, but a better understanding of nucleation and growth mechanisms is needed for full utilization and control. Here we use in situ X-ray diffraction to follow the nucleation and growth of BaTiO3 formed by hydrothermal synthesis using two different titanium precursors, an amorphous titania precipitate slurry and a Ti-citric acid complex solution. Sequential Rietveld refinement was used to extract the time dependency of lattice parameters, crystallite size, strain and atomic displacement parameters. Phase pure BaTiO3 nanoparticles 10 - 15 nm in size were successfully synthesized at different temperatures (100, 125, and 150 °C) from both precursors after reaction times ranging from a few seconds, to several hours. The two precursors resulted in phase pure BaTiO3 with similar final crystallite size. Finally, two different growth mechanisms were revealed, where the effect of surfactants present during hydrothermal synthesis is discussed as one of the key parameters.
Preprint
|
|
|
Materials Science, Biomaterials; capsaicin; chitosan; lecithin; dissipative particle dynamics
Online: 2 May 2018 (11:07:01 CEST)
|
|
|
Share this article with
×
Transport of hydrophobic drugs in the human body exhibits complications due to the low solubility of these compounds. With the purpose of enhancing the bioavailability and biodistribution of such drugs, recent studies have reported the use of amphiphilic molecules, such as phospholipids, for synthesis of nanoparticles or nanocapsules. Given that phospholipids can self–assemble in liposomes or micellar structures, they are ideal candidates to function as vehicles of hydrophobic molecules. In this work, we report mesoscopic simulations of nanoliposomes, constituted by lecithin and coated with a shell of chitosan. The stability of such structure and the efficiency of encapsulation of capsaicin, as well as the internal and superficial distribution of capsaicin and chitosan inside the nanoliposome were analyzed. The characterization of the system was carried out through density maps and the potentials of mean force for the lecithin–capsaicin, lecithin–chitosan and capsaicin–chitosan interactions. The results of these simulations show that chitosan is deposited on the surface of the nanoliposome, as has been reported in some experimental works. It was also observed that a nanoliposome of approximately 18 nm in diameter is stable during the simulation. The deposition behavior was found to be influenced by pattern of N-acetylation of chitosan.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; Centella asiatica extract; gelatin; carboxymethyl cellulose (CMC); antioxidant; functionality properties
Online: 1 May 2018 (11:10:24 CEST)
|
|
Share this article with
×
This study aimed to characterize the antioxidant, mechanical and physical properties of chicken skin gelatin/CMC/Centella asiatica blended film. The influence of Centella asiatica at 0.3% and 0.7% on antioxidant activities; mechanical properties and physical properties of chicken skin gelatin/CMC/Centella asiatica film were investigated. Characterization of the blended films with 0.7% Centella asiatica extract shows higher antioxidant activities with a total phenolic content of 0.36 mg/g of GAE, DPPH of 89.26%, and reducing power of 0.80 nm compared to 0.3% Centella asiatica extract. The addition of 0.3% of Centella extract provide higher value in tensile strength (5.0 × 10−2 MPa), elongation at break (281%), melting point (131.31 °C), transparency (0.86) but lower UV-light penetration. While the addition of 0.7% Centella extract contribute to higher value in WVP (1.13 × 10−4 g m−1s−1Pa−1) and puncture test (0.06 N). There are no significant differences between functional groups obtained from this blended film as evaluated by FTIR analysis (p > 0.05). Furthermore, XRD analysis showed the addition of extract decrease the crystallinity of film. In conclusion, the incorporation of Centella asiatica extracts on film greatly increased antioxidant levels and improved some of the mechanical and physical properties of the film blends.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; Cemented carbides, cermets, iron binders, oxide coating, radiation shielding, nanoindentation, passivation, silicides.
Online: 1 May 2018 (11:04:54 CEST)
|
|
Share this article with
×
An oxidation resistant coating on cemented tungsten carbides is characterised in this work. Cemented tungsten carbides (cWCs) are routinely used in mining and manufacturing but are also candidate materials for compact radiation shielding in fusion power generation. In both environments, cWCs will suffer significant degradation due to oxidation at relatively low temperatures. In a recent study, a Si-deposition coating method was demonstrated to improve the oxidation resistance of cWCs by up to a factor of 1,000. This work focusses on the growth kinetics, phase composition, and mechanical properties of these coatings. By combining quantitative X-ray diffraction, electron microscopy and nanoindentation, we show that the coating layer has a 20 % higher hardness than the substrate, which was explained on the basis of a previously-unknown presence of a fine distribution of very hard SiC laths. To interpret the coating stability, a coating growth map is developed. The map shows the structure is stable under a broad range of processing temperatures and composite compositions, demonstrating the potential application of these coatings in a variety of nuclear shielding cWCs.
Preprint
|
|
|
Materials Science, Polymers & Plastics; Oil palm; Liquefaction; Residue; Polyhydric alcohols
Online: 30 April 2018 (18:50:24 CEST)
|
|
Share this article with
×
Resides derived from liquefaction of oil palm trunk in the presence of polyhydric alcohol with different liquefaction temperature and time were characterized to provide a new approach to understand some fundamental aspects of the liquefaction reaction. Higher temperature and longer reaction time resulted in lower residue content, indicating more decomposition of components of oil palm trunk. The amorphous polymer comprised of lignin, hemicellulose, starch, and cellulose with non-crystalline structure are firstly degraded at low liquefaction temperature, followed by the decomposition of crystalline region of cellulose. Although it was relatively difficult to destroy the ordered structure of cellulose, most of them could be liquefied via prolonging reaction time or enhancing reaction temperature. Nevertheless, it was found that re-condensation of liquefied products occurred during the liquefaction process when higher temperature of 180 oC was used after 60 min, leading to the gradual increase of residue content with increase of reaction time.
Preprint
|
|
|
Materials Science, Nanotechnology; III-N Nanowires; Piezoelectric generation; Atomic force microscope; Piezo-generators; Energy harvesting
Online: 30 April 2018 (18:31:29 CEST)
|
|
Share this article with
×
We demonstrate for the first time efficient mechanical to electrical energy conversion using InGaN/GaN nanowires (NWs). Using an atomic force microscope equipped with a modified Resiscope module, we analyse the piezoelectric energy generation of GaN NWs and demonstrate an important enhancement when integrating in their volume a thick In-rich InGaN insertion. The piezoelectric response of InGaN/GaN NWs can be tuned as a function of the InGaN insertion thickness and position in the NW volume. The energy harvesting is favoured by the presence of a PtSi/GaN Schottky diode which allows to efficiently collect the piezo-charges generated by InGaN/GaN NWs. Average output voltages up to 330 ± 70 mV and a maximum value of 470 mV per NW has been measured for nanostructures integrating 70 nm-thick InGaN insertion capped with a thin GaN top layer. This latter value establishes an increase of about 35% of the piezo-conversion capacity in comparison with binary p-doped GaN NWs. By considering these output signals, we estimate a maximum power density generated by one layer of dense InGaN/GaN-based NW of about 3.3 W/cm2. These results settle the new state-of-the-art for piezo-generation from GaN-based NWs and offer a promising perspective for extending the performances of the piezoelectric sources.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; hemp bast fibre; hydrothermal processing; KOH activation; activated carbon
Online: 28 April 2018 (12:29:14 CEST)
|
|
|
Share this article with
×
Synthesis of activated carbon from waste biomass is of current interest towards sustainability. The properties of biomass derived activated carbon largely depends on the carbonization process. This study reports preparing extremel high surface area mesoporous activated carbon from hemp bast fibre using hydrothermal processing. Processing in hot water (390-500oC), then activation using KOH and NaOH was investigated at different loading ratios. The described approach was found to enhance the mesoporosity (centered at 3.0 to 4.5 nm) of the hemp derived activated carbon (HAC) from activation (confirmed by BJH pore size distribution and TEM imaging). BET results showed that the product has an extremely high surface area (2425 m2/g) while the surface functional groups (-OH, COOH, C=C/C-C) were confirmed and quantified by XPS and FTIR results. Increasing KOH concentration was found to enhance the surface area with an optimum biochar to KOH ratio of 1:3. The crystallite domain size of HAC was determined using Raman spectroscopy of different wavelengths. The procedure described in this study is an environmentally friendly scalable route for the mass production of activated carbon using hemp fiber.
Preprint
|
|
|
Materials Science, Nanotechnology; fullerenes; nanohybrids; nanobiotechnology; bioconjugation; chemical stability
Online: 28 April 2018 (11:46:45 CEST)
|
|
Share this article with
×
The high hydrophobicity of fullerenes and the resulting formation of aggregates in aqueous solutions hamper the possibility of their exploitation in many technological applications. Noncovalent bioconjugation of fullerenes with proteins is an emerging approach for their dispersion in aqueous media. Contrary to covalent functionalization, bioconjugation preserves the physicochemical properties of the carbon nanostructure. The unique photophysical and photochemical properties of fullerenes are then fully accessible for applications in nanomedicine, sensoristic, biocatalysis and materials science fields. However, proteins are not universal carriers. Their stability depends on the biological conditions for which they have evolved. Here we present two model systems based on pepsin and trypsin. These proteins have opposite net charge at physiological pH. They recognize and disperse C60 in water. UV-Vis spectroscopy, zeta-potential and atomic force microscopy analysis demonstrates that the hybrids are well dispersed and stable in a wide range of pH’s and ionic strengths. A previously validated modelling approach identifies the protein-binding pocket involved in the interaction with C60. Computational predictions, combined with experimental investigations, provide powerful tools to design tailor-made C60@proteins bioconjugates for specific applications.
Preprint
|
|
|
Materials Science, Nanotechnology; silicon solar cells; semiconductors; electron-hole pairs
Online: 27 April 2018 (09:46:15 CEST)
|
|
Share this article with
×
Band-gap alignment engineering has now been extensively studied due to its high potential application. Here we demonstrate a simple route to synthesize two metal oxide layers and align them together according to their bandgaps on surface of crystalline silicon (c-Si) solar cells. The metal oxide layers can not only extend absorption spectrum to generate extra carriers but also serve to separate electron-hole pairs more efficiently. As a consequence, the photovoltaic performance of SnO2/CdO /Si double-layer solar cell (DLSC) is highly improved compared to CdO/Si and SnO2/Si single-layer solar cells(SLSCs) and SnO2/CdO/Si double-layer solar cell (DLSC). By the alignment engineering, the SnO2/CdO/Si DLSC produces a short circuit photocurrent (Jsc) of 38.20 mA/cm2, an open circuit photovoltage (Voc) of 0.575 V and a fill factor (FF) of 68.7%, corresponding to a light to electric power conversion efficiency (η) of 15.09% under AM1.5 illumination. These results suggest that with the use of metal oxide layers by band-gap alignment engineering, new avenues have been opened for developing high-efficiency and cost-effective c-Si solar cells.
Preprint
|
|
|
Materials Science, Nanotechnology; TiO2-SiO2 functionalization; superhydrophilic coating; nanocomposite coating
Online: 26 April 2018 (10:30:04 CEST)
|
|
Share this article with
×
In this study, a novel binary nanocomposite system based on TiO2-SiO2 was functionalized with trimethylolpropane triacrylate (TMPTA) and characterized by XPS and XRD. Results revealed that TiO2-SiO2 nanoparticles were covalently functionalized. Functionalized nanoparticles at low concentrations (0.1 wt% and 0.5 wt%) were dispersed in acrylic acid acting as a polymer matrix. Nanocomposite coatings analysis demonstrate to achieve superhydrophilic properties as well as very good optical characteristics. Water contact angle characterization showed the functionalization effect by achieving a superhydrophilic behavior with a contact angle less than 5°. UV-Vis measurements demonstrated high optical transmittance above 95% for the coatings. Based on the obtained results a mechanism describing the chemical interactions of the constituents responsible for the synergy in the nanocomposite as well as the morphological play role in the behavior are presented.
Preprint
|
|
|
Materials Science, Nanotechnology; metal nanocomposite hydrogels; particle distribution; nanoplasmonic sensor; preparation methods; SEM imaging; volume imaging
Online: 26 April 2018 (08:16:47 CEST)
|
|
Share this article with
×
The distribution of noble metal nanoparticles in hydrogels are influencing their nanoplasmonic response and signal used for biosensor purposes. By controlling the particle distribution, it is possible to obtain new nanoplasmonic features with new sensing modalities. Particle distributions can be characterized by using volume-imaging methods such as the focused ion beam-scanning electron microscope (FIB-SEM) and the serial block-face scanning electron microscopy (SBFSEM) techniques . Since the pore structure of hydrogels is contained by the water absorbed in the polymer network it may pose challenges for volume-imaging based on electron microscope techniques since the sample must be in a vacuum chamber. The structure of hydrogels can be conserved by choosing appropriate preparation methods, which also depends on the composition of the hydrogel used. In this paper, we have prepared low-weight percentage hydrogels, with and without gold nanorods (GNR) for conventional SEM imaging by using two different drying techniques; (1) the critical point drying (CPD) technique and (2) hexamethyldisilazane (HMDS) drying of hydrogels. A qualitative characterization of the GNR-hydrogels was carried out to study the GNRs positioned in the polymer network. The effect of the two different drying methods on the hydrogel morphology were also compared. The use of HMDS as an alternative to the CPD has several advantages involving less parametrical variables for drying, involving less effort, being cost-effective, and requires no equipment use. In addition, choosing an optimized sample preparation method for SEM with optimized imaging parameters is highly important for obtaining accurate information about materials that is not correlated to artifacts. Hence, the results obtained from the preparation methods and SEM imaging parameters in this paper are useful for developing methods for mapping the metal particle distributions in micro-hydrogels by using FIB-SEM and SBFSEM techniques.
Preprint
|
|
|
Materials Science, Polymers & Plastics; aminofunctional starch (ANS); biodegradation; carboxylated nitrile butadiene rubber (XNBR) latex films
Online: 25 April 2018 (07:53:16 CEST)
|
|
Share this article with
×
The Aminofunctional starch/Carboxylated nitrile butadiene rubber (ANS/XNBR) latex films were prepared with control (0), 5, 10, 15, and 20 phr of ANS loadings. The films were subjected to soil burial test for 8 weeks, which recovered every two weeks to quantify the degraded properties. The control (week 0) and biodegraded films were subjected to physical tests (crosslink density, tensile, and tear strength tests) and biodegradation quantification (mass loss retention, and water vapor transmission rates). The optimum physical properties of ANS/XNBR films were subjected to further assessment of its degradation properties which include morphological (optical and scanning electron microscopes (SEM)), Fourier transform infrared (FTIR) analysis, and thermogravimetric analysis (TGA) respectively. Overall, mechanical properties of biodegraded ANS/XNBR latex films decreased as biodegradation period elapses. The biodegradation assessment via water vapor transmission rates and mass loss analyses indicates the high degree of biodegradation rates were observed with higher loading of ANS/XNBR latex films. Morphological analyses via optical microscope shows the transformation of the films surface opacity during biodegradation test. SEM images depicted the microorganism remains on the film surfaces. For FTIR analysis, the most significant changes in the spectras of the films appeared in the region of 790–3000 cm−1. TGA thermograph shows the thermal retention of the materials decreased, as the biodegradation period elapses for optimum ANS/XNBR latex films. From the results obtained, ANS/XNBR latex films shows optimum degradation and mechanical properties at 10 phr filler loading.
Preprint
|
|
|
Materials Science, Polymers & Plastics; Renewable resources; Lignocellulosic Biomass; Polymerization; Reaction mechanisms; Furfuryl alcohol
Online: 20 April 2018 (14:19:30 CEST)
|
|
Share this article with
×
Furfuryl alcohol (FA) is a biobased monomer derived from lignocellulosic biomass. The present work describes its polymerization in presence of protic polar solvents, i.e. water or isopropyl alcohol (IPA), using maleic anhydride (MA) as acidic initiator. The polymerization was followed from the liquid to the rubbery state by combining DSC and DMA data. In the liquid state, IPA disrupts the expected reactions during all the FA polymerization due to a stabilization of the furfuryl carbenium center. This causes the initiation of the polymerization at higher temperature, which is also reflected by higher activation energy. In water system, the MA opening allows to start the reaction at lower temperature. A higher pre-exponential factor value is obtained in that case. The DMA study of final branching reaction occurring in the rubbery state has highlighted continuous increase of elastic modulus until 290 °C. This increasing tendency of modulus was exploited to obtain activation energy dependences (Eα) of FA polymerization in the rubbery state.
Preprint
|
|
|
Materials Science, Biomaterials; Jute fiber; Starch matrix; Epoxy resin; Biocomposite; Microstructure
Online: 20 April 2018 (13:58:18 CEST)
|
|
Share this article with
×
In this article, bio-composites derived from starch-glycerol biodegradable matrix reinforced with jute fibers have been fabricated using the wet hand lay-up and compression moulding techniques. Samples having different weight percentages of jute fiber in the starch matrix have been analysed. The fibers surface was chemically treated by alkaline sodium hydroxide for improving the interphase bonding between fiber and matrix. Tensile test for the composites were done and the sample with highest tensile strength was selected for further tests that included water absorption, scanning electron microscopy and thermal analysis. It has been concluded that the ultimate tensile strength was found to be maximum for the composition of 15% fiber by weight composite as 7.547 MPa without epoxy coating and 10.43 MPa with epoxy coating. The major disadvantage of bio-composite is its high water absorption property, which in this study has been inhibited by the epoxy resin layer. Herein, the results of various tests done disclose a noteworthy improvement in the overall properties of bio-composite, in comparison to the neat biodegradable starch matrix.
Preprint
|
|
|
Materials Science, Nanotechnology; fundamental and applied physics; process parameters; force-energy; anisotropic particles; one-dimensional particles; three-dimensional particles
Online: 19 April 2018 (10:41:36 CEST)
|
|
|
Share this article with
×
Developing particles of different geometric anisotropic shapes are the hot topic since decades as they guarantee some special features of properties not possible through other means. Again, controlling atoms to develop certain size and shape particle is a quite challenging job. In this study, gold particles of different shapes are developed via pulse-based electronphoton-solution interface process. Here, it is discussed that gold atoms under certain transition state amalgamated at solution surface to develop monolayer assembly around the light glow of electrons and photons, which is known in plasma, generating through flowing argon gas copper capillary, which is known in cathode. The rate of uplifting gold atoms to solution surface is controlled under the fixed optimized entrance of forced energy electron streams and photons of high forcing energy. Uplifting gold atoms dissociated on dissociation of precursor under the dissipating heat energy resulted by propagating photonic current through graphite rod immersed in the solution, which is known in anode. On the other hand, packets of nano shape energy resulted by the controlled tuned pulse protocol developing tiny particles of own shape by binding transition state atoms of compact monolayer assembly. At solution surface, adjusting atoms of monolayer tiny particle into one-dimensional arrays under the disconcerted lateral forces following by their elongation under uniformly exerted opposite poles forces. This results into convert them in a structure of smooth elements where adjacently placed electrons and those in the outer rings of elongated atoms inter-connecting side-to-side by introducing orientational-based stretching of clamped energy knots. Tiny sized particles developed their atoms of one-dimensional arrays in structure of smooth elements exert an immersing force at favorable side tips and where many such tiny particles around the light glow work as one unit for each case resulting into pack by inter-connecting at inside their common point to nucleate the shape of certain particle. Depending on the development zone of such tiny sized particles and their amount of simultaneous packing under naturally maintained orientations develop their different geometric anisotropic shaped particles. At fixed precursor concentration, increasing the process time results into develop particles of low aspect ratio. Under tuned parameters, developing mechanisms of particles of high aspect ratio exhibiting unprecedented features are discussed.
Preprint
|
|
|
Materials Science, Polymers & Plastics; Chitosan-g-PMMA amphiphilic nanoparticles; thiolated polymers; mucoadhesion; mucosal drug delivery; Caco2 and HT29-MTX cell lines; apparent permeability in vitro.
Online: 18 April 2018 (16:28:21 CEST)
|
|
Share this article with
×
Engineering of drug nanocarriers combining fine-tuned mucoadhesive/mucopenetrating properties is currently being investigated to ensure more efficient mucosal drug delivery. Aiming to improve the transmucosal delivery of hydrophobic drugs, we designed a novel kind nanogel produced by the self-assembly of amphiphilic chitosan graft copolymers ionotropically crosslinked with sodium tripolyphosphate. In this work, we synthesized for the first time chitosan-g-poly(methyl methacrylate) nanoparticles thiolated by the conjugation of N-acetyl cysteine. First, we confirmed that both non-crosslinked and crosslinked nanoparticles in the 0.05-0.1% w/v concentration range display very good cell compatibility in two cell lines that are relevant to oral delivery, Caco2 cells that mimic the intestinal epithelium and HT29-MTX cells that produce mucin. Then, we evaluated the effect of crosslinking, nanoparticle concentration and thiolation on the permeability in vitro utilizing monolayers of (i) Caco2 and (ii) Caco2:HT29-MTX cells (9:1 cell number ratio). Results confirmed that the ability of the nanoparticles to cross Caco2 monolayer was affected by the crosslinking. In addition, thiolated nanoparticles interact more strongly with mucin, resulting in a decrease of the apparent permeability coefficient (Papp) compared to the pristine nanoparticles. Moreover, for all the nanoparticles, higher concentration resulted in lower Papp suggesting indicating that the transport pathways could undergo saturation.
Preprint
|
|
|
Materials Science, Polymers & Plastics; acrylamide; microwave assistance; intrinsic viscosity; flocculant; phenol removal
Online: 18 April 2018 (15:48:27 CEST)
|
|
Share this article with
×
A composite flocculant P(AM–DMDAAC) was synthesized by the copolymerization of acrylamide (AM) and dimethyl diallyl ammonium chloride (DMDAAC). Using microwave (MV) assistance with ammonium persulfate as initiator, the synthesis provided short reaction time and better solubility product. Nuclear magnetic resonance spectroscopy (1H NMR and 13C NMR), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential thermal analysis-thermo gravimetric analyzer (DTA-TGA) were used to determine the structure and morphology of P(AM–DMDAAC). Parameters affecting the intrinsic viscosity ([η]) of P(AM–DMDAAC), such as microwave time, mass ratio of DMDAAC to AM, initiator ammonium persulfatedosage, sodium benzoate dosage, bath time, reaction temperature and pH value were examined. Results showed that the optimum synthesis conditions were microwave time 1.5 min, m(DMDAAC): m(AM) is 4:16, 0.5 wt‰ initiator, 0.4 wt‰ EDTA, 0.3 wt‰ sodium benzoate, 2 wt‰ urea, 4 h bath time, 4.0h reaction time and pH 2. To study the removal of phenol by P(AM–DMDAAC), the influence of flocculant dose, pH value and the stirring speed were investigated, with optimization providing 99.8 % removal.
Preprint
|
|
|
Materials Science, General Materials Science; ultrasound; TiO2 nanoparticles; oxygen vacancy; photocatalytic activity; visible light
Online: 18 April 2018 (09:45:18 CEST)
|
|
Share this article with
×
TiO2 nanoparticles were successfully synthesized using a facile and scalable sol-gel method followed by calcination in air. The structural and optical properties, along with the photocatalytic performance of the nanoparticles were analyzed using X-ray diffraction, infrared spectroscopy, transmission electron microscopy, energy dispersive spectroscopy, UV-vis spectroscopy, photoluminescence spectroscopy, and degradation of anionic azo dye (methyl orange (MO)) under visible light irradiation. The prepared TiO2 nanoparticles crystallize in the anatase structure with a highly crystalline order. The results showed a band gap energy of 3.59, 3.79 and 3.54 eV, respectively, which suggests a better photocatalytic activity for sample calcined at 450 °C compared to other samples’ thermal treatments. The synthesis route employed for the preparation of the TiO2 nano-photocatalyst resulted to be efficient for degradation reactions MO of dyes.
Preprint
|
|
|
Materials Science, Nanotechnology; prefabricated metal crowns (PMCs); nickel (Ni); chromium (Cr); iron (Fe); ion release
Online: 18 April 2018 (08:38:25 CEST)
|
|
Share this article with
×
Dental caries is a public health problem worldwide according to WHO data. Among treatments in pediatric dentistry, prefabricated metal crowns (PMCs) have been one of the most successful options since they were introduced in cases of considerable tooth destruction. Our objective was to detect the presence and concentration of iron (Fe), chromium (Cr), and nickel (Ni) in saliva of patients who require rehabilitation with PMCs, before and after their placement. A quasi-experimental study was performed in 32 patients who attended dental care in a pediatric dentistry clinic at a public university and who required rehabilitation with PMCs. Parametric tests (ANOVA and Pearson correlation) were performed, and a p ≤ 0.05 was considered statistically significant. Statistically significant differences were found when comparing the Ni release before, 1 week, and 1 month after placing the crowns. Similarly, we observed a positive correlation between the number of crowns and Ni release. No tests were performed for Fe and Cr because the amounts of these metals were less than 0.1 ppb, which was not detectable by inductively coupled plasma optical emission spectrometry (ICP-OES). The levels of Fe, Cr, and Ni released were below toxic health levels. Studies are required to evaluate whether this release has negative effects at cellular levels.
Preprint
|
|
|
Materials Science, General Materials Science; fly ash; nanocomposite; environmental pollution; volatile organic compounds; heavy metal
Online: 16 April 2018 (16:15:22 CEST)
|
|
Share this article with
×
Air pollutants such as volatile organic compounds (VOCs), nitrogen oxides (NOx), sulfur dioxide (SO2), as well as water pollutants including heavy metal, are harmful to human and environment. Effective control and reduction of their pollution is therefore an important topic for today’s scientists. Fly ash (FA) is a type of industrial waste that can cause multiple environmental problems if discharged into the air. On the other hand, because of its high porosity, large specific surface area, and other unique characteristics, the FA can also be used as a low-cost and high efficient adsorbent with some simple modifications. This paper reviews the effects of FA on treatment of the above air and water pollution based on our research experience over many years, including to the current status of global FA utilization, physicochemical properties, principle of adsorption, and the application direction of FA in the future. It focuses on the use of nanocomposite technology to fabricate functional FA fibrous membranes to adsorb VOCs from air, and treat heavy metal wastewater. This present review first describes the fabrication technology of FA nanocomposites and their mechanism of adsorption VOCs from air. Utilization of nanofiber technology to fabricate multi-functional FA emerging composite materials to mitigate air and water pollution has great potential in the future, especially use of pollutant material to control other pollutants.
Preprint
|
|
|
Materials Science, Metallurgy; pitting; sigma phase; 2205; duplex stainless steel
Online: 16 April 2018 (09:32:02 CEST)
|
|
Share this article with
×
The precipitate phases often play an important influence on the corrosion resistance of 2205 Duplex stainless steel (DSS). In the presented paper, the microstructure and corrosion resistance in the hot-rolled and cold-rolled 2205 DSS aging for different time at 850 °C was investigated by XRD, SEM and potentiodynamic polarization. It has been found that the Chi(χ) phase and Sigm(σ) phase were precipitated in turn after aging treatment of hot-rolled and cold-rolled materials, but the precipitate amount in cold-rolled material is much more than that of hot-rolled samples. The corrosion resistance of the solution-annealed cold-rolled material is similar to the hot-rolled material, but the corrosion resistance of cold-rolled material with precipitate is weaker than that of hot-rolled material after aging treatment. Pitting initiates preferentially in the Cr-depleted region from σ phase in aged hot-rolled 2205, and severe selective corrosion occurs on sigma/ferrite interfaces aged for a long aged lime. However, the initiation of pitting corrosion may take place at the phase boundary, defect and martensite in the aged cold-rolled 2205. The σ phase is further selectively dissolved by electrochemical method to investigate the difference of microstructure and corrosion behavior in hot-rolled and cold-rolled 2205 duplex stainless steel.
Preprint
|
|
|
Materials Science, Polymers & Plastics; reactive energetic plasticizer; 1,3-dipolar cycloaddition; polyurethane; energetic binder
Online: 16 April 2018 (08:22:59 CEST)
|
|
Share this article with
×
Reactive energetic plasticizers (REPs) coupled with hydroxy-telechelic poly(glycidyl azide-co-tetrahydrofuran) (PGT)-based energetic polyurethane (PU) binders for use in solid propellants and plastic-bonded explosives (PBXs) were investigated. The generation of gem-dinitro REPs along with a terminal alkyne stemmed from a series of finely designed approaches to not only satisfy the common demands as conventional energetic plasticizers but prevent the migration of plasticizers. The miscibility and rheological behavior of a binary mixture of PGT/REP with various REP fractions were quantitatively determined by differential scanning calorimetry (DSC) and rheometer, respectively, highlighting the promising performance of REPs in the formulation process. The kinetics on the distinct reactivity of propargyl vs. 3-butynyl species of REPs towards the azide group of the PGT prepolymer in terms of Cu-free azide-alkyne 1,3-dipolar cycloaddition (1,3-DPCA) was studied by monitoring 1H nuclear magnetic resonance spectroscopy and analyzing the activation energies (Ea) obtained using DSC. The thermal stability of the finally cured energetic binders with the incorporation of REPs indicated that the thermal stability of the REP/PGT-based PUs was maintained independently of the REP content. The tensile strength and modulus of the PUs increased with increasing the REP content. In addition, the energetic performance and sensitivity of REP and REP triazole species was predicted.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; hard coating; TiN; atomic nature; expansion-contraction; potential energy; force-energy behaviors; ground point; structure evolution
Online: 16 April 2018 (06:00:30 CEST)
|
|
Share this article with
×
Coatings of suitable materials of thickness of few atoms to several microns on certain substrate is the basic need of society and attend the regular attention of scientific community working in different domains; decorative and protective coatings, transparent and insulating coatings, coating medical implants and surgical instruments, coatings for drug delivery and security purposes, ultra-precision machine coatings, coating cutting tools, coatings for MEMS and NEMS, and so on. Different coatings develop under significant composition of certain nature atoms where their force-energy behaviors while certain transition state provide the provision for electron in outer ring of gas atom to clamp another energy knot clamped unfilled state in the outer ring of solid atom. Under certain process conditions, different nature atoms upto a certain extent oppositely-switch force-energy behaviors to the ones which possess those behaviors originally where they locate ground points at common mid-points of accommodating levels resulting into grasp binding. Because of adjusting expansion-contraction of clamped energy knots to electrons under different potential energy as per exerting orientational force of gravitation-levitation behaviors, different nature atoms develop structure at near ground surface substrate termed as hard coating, which is known since antiquity. On arresting different nature atoms under their binding at nearly oppositely-worked force-energy, non-conservative energies of ground surface are involved to engage the non-conservative forces exerting their neutral behavior viable at electron level. Different properties and characteristics of hard coatings such as hardness, adhesion, roughness, friction coefficient, resistivity and morphology-structure are emerged as per order of rescued force-energy of their structure. Here, hard coatings invent science opening to several new areas.
Preprint
|
|
|
Materials Science, General Materials Science; : carbon; atomic structure; atomic behavior; atomic binding; force-energy behaviors; glassy carbon
Online: 16 April 2018 (05:55:12 CEST)
|
|
Share this article with
×
Many studies deal synthesis of carbon-based materials because of the versatility of carbon element where lack the arresting of understanding at convincing and compelling levels. A non-conservative energy is required to transfer occupied state electron to nearby unfilled state along both left and right sides of the gas state carbon atom to convert it into its graphitic state where exerting forces of relevant poles of transferring electrons remain neutral at the instant of tracking the arc-like trajectory to go into unfilled state. Changing the position of two electrons in each state carbon atom results into originate its new physical behavior. Different state carbon atoms were obtained under confined inter-state electron-dynamics under the involvement of non-conservative energies where engaging the non-conservative forces instead of conservative were engaged. Structure evolution for graphitic, nanotube, and fullerene states atoms mainly engages the surface format forces where involved arc-shape energies enable execution of confined inter-state electron-dynamics binding to amalgamating atoms in one quadrant, two quadrants and four quadrants to develop structure of one-dimension, two-dimension and four-dimension, respectively. However, a graphite structure is evolved under the application of electron-dynamics of attaining graphitic state atoms as well as under their attained dynamics, only. Evolution of structure in diamond and lonsdaleite state atoms are under the joint application of surface format force and grounded format force where electrons of binding atom deal another clamping of energy knots belonging to unfilled states of deposited atoms while visualizing the force of south to their bottom tips through them. Structural evolution of graphene engages both surface format and space format forces to work neutral at the instant of binding atom through its four electrons dealing another clamping of energy knots belonging to unfilled states of deposited atoms while visualizing the force of north to their top-sides through them. Growth of diamond is south to ground but binding of atoms is ground to south, so it is tetra-double-clamped energy knot ground to south topological structure. Same is the case for lonsdaleite state atoms except it is bi-double-clamped energy knot ground to south topological structure. Growth of graphene is north to ground but binding of atoms is ground to north, so it is tetra-double-clamped energy knot ground to north structure. Glassy carbon is related to a wholly layered-topological structure where tri-layers of gas carbon atoms, graphitic state atoms and lonsdaleite state atoms order in repetition manner. In glassy carbon, forces of space format, surface format and grounded format work as neutral while binding atoms of successive tri-layers. Due to maintenance of electrons at above ground surface in gas state carbon atoms, they do not attain the favorable point for binding. Hardness of carbon-based materials as per identified in literature is sketched under the exploration of different force-energy behaviors exerting at electron level is described. A carbon atom is a best model to explain binding mechanism in atoms of various elements and in fullerene state, it is a best model to understand the working forces at ground surface.
Preprint
|
|
|
Materials Science, Nanotechnology; photocatalysis; Z-scheme; conjugated polymer; Bi2MoO6
Online: 12 April 2018 (09:58:11 CEST)
|
|
|
Share this article with
×
Search for appropriate materials with favorable staggered energy band arrangements is important and of great challenge to fabricate Z-scheme photocatalysts with high activity in visible light. In this study, we demonstrated a facile and feasible strategy to construct highly active organic-inorganic Z-scheme hybrids (P-BMO) with linear pyrene-based conjugated polymer (P17-E) and Bi2MoO6 via in-situ palladium-catalyzed cross-coupling reaction. Characterization results revealed C-O chemical bond formed at the heterointerface between P17-E and Bi2MoO6 after in-situ polycondensation and endowed the hybrids with observably improved photogenerated carries transfer capability. Visible light driven photocatalytic removal of ciprofloxacin and Cr(VI) were significantly enhanced after the incorporation of P17-E into Bi2MoO6 whether with the morphology of nanosheets, nanobelts or microspheres. Moreover, this P-BMO hybrids were also found to exhibit sustainable excellent photocatalytic performance after four runs of photocatalytic evaluation test, suggesting its high activity and stability. To better eliminate the redox ability enhancement of P-BMO, a reasonable Z-scheme electrons transferring mechanism between P17-E and Bi2MoO6 was proposed and proved by the determination of •O2– and •OH and Pt nanoparticles photodeposition experiments. This work might provide a viable source and insight into the design of Z-scheme photocatalysts with excellent redox ability for environmental remediation.
Preprint
|
|
|
Materials Science, General Materials Science; magnesium alloy; EV31A; MAGMASoft; simulation; casting; foundry
Online: 9 April 2018 (11:06:49 CEST)
|
|
Share this article with
×
Carrying out technological tests and research is indispensably connected with high costs and elongation of implementation time of new casting technologies and their modifications in industry. Hence, the application of specialised computer software, enabling the simulation and analysis of metallurgical and casting processes in modern foundry industry is of special interest. The present work presents an experimental application of MAGMASoft software in casting process of EV31A magnesium alloy structural element of helicopter engine. The results of computer simulation have been compared with industrial cast of the simulated element, fabricated in the same conditions. It has been revealed that the computer simulation provides a complex information on the analysed process, leading to reduction of costs and time, connected with technological tests in implementation of new casting technologies.
Preprint
|
|
|
Materials Science, Polymers & Plastics; additive manufacturing; desktop 3D printing; fused deposition modeling; fused filament fabrication; polylactic acid; anisotropy; interlayer bonds; mechanical strength; digital fabrication
Online: 9 April 2018 (10:33:56 CEST)
|
|
Share this article with
×
This work investigates how the user-controlled parameters of the 3D printing process define temperature conditions on the boundary between layers of the part being fabricated and how these conditions influence the structure and strength of the part. The process studied is fused filament fabrication with a desktop 3D printer and the material utilized is PLA (polylactic acid). As a characteristic of the part strength the fracture load in the case of a three-point bend and calculated related stress were used. During the printing process parts were oriented with the long side along the Z axis, thus, in the bend tests, the maximum stress occurred orthogonally to the layers. During the fabrication process, temperature distribution on the sample surface was monitored with thermal imager. Sample mesostructure was analyzed using SEM. The influence of the extrusion temperature, the intensity of part cooling, the printing speed and the time between printing individual layers were considered. The influence of all the parameters can be expressed through two generalizing factors: the temperature of the previous layer and the flow efficiency, determining the ratio of the amount of extruded plastic to the calculated. A regression model was proposed that describes the effect of the two factors on the printed part strength. Along with interlayer bonding strength, these two factors determine the formation of the part mesostructure (the geometry of the boundaries between individual threads). It is shown that the optimization of the process parameters responsible for temperature conditions makes it possible to approximate the strength of the interlayer cohesion to the bulk material strength.
Preprint
|
|
|
Materials Science, Nanotechnology; bimetallic nanoparticles; optical properties; magnetic properties; biological applications
Online: 9 April 2018 (10:20:00 CEST)
|
|
Share this article with
×
Metal nanoparticles are extensively studied due to their unique chemical and physical properties, which differ from the properties of their respective bulk materials. Likewise, the properties of heterogeneous bimetallic structures are far more attractive than those of single-component nanoparticles. The incorporation of a second metal into the nanoparticle structure alters the surface plasmon resonance and magnetic properties of the bimetallic composite. This review focuses on the enhanced optical and magnetic properties offered by bimetallic nanoparticles and their corresponding impact on biological applications. We summarize the predominant structures of bimetallic nanoparticles, outline their synthesis methods, and highlight their use in biological applications, both diagnostic and therapeutic, which are dictated by their various optical and magnetic properties.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; Cu/Al laminated composites; deformation behavior; interface; microstructure; constitutive equation
Online: 9 April 2018 (07:55:59 CEST)
|
|
Share this article with
×
In order to understand the hot deformation behavior of novel Cu/Al laminated composites, isothermal hot compression tests were conducted by Gleeble-1500D thermo-mechanical simulator. And the effect of bonding interface, deformation temperature and strain rate on the deformation behavior was analyzed. Results show that under the interface constraint effect, soft Al layer trends to flow synchronously with hard Cu layer. And further microstructure examinations indicate the cooperative deformation capability of Cu/Al composites increases with increasing stain rate and decreasing deformation temperature. Strain hardening exponent, calculated based on the true stress-true strain data, also proves the effect of deformation temperature and strain rate on the cooperative deformation behavior. Meanwhile, unique composites structure allows the Al matrix to exhibit the characteristic of dynamic recrystallization during the hot deformation process. Lastly, strain compensated Arrhenius-type constitutive equation was employed to describe the coupling effect of temperature, strain rate and strain on the flow stress.
Preprint
|
|
|
Materials Science, Nanotechnology; carbonization; laser annealing; mesophase; graphitization; porous carbon
Online: 8 April 2018 (12:07:13 CEST)
|
|
Share this article with
×
Porous graphite was prepared without the use of template by rapidly heating the carbonization products from mixtures of anthracene, flourene, and pyrene with a CO2 laser. Rapid CO2 laser heating at a rate of 1.8 × 10 6 °C/s vaporizes out the fluorene-pyrene derived pitch while annealing the anthracene coke. The resulting structure is that of graphite with 100 nm spherical pores. The graphitizablity of the porous material is the same as pure anthracene coke. Transmission electron microscopy revealed that the interface between graphitic layers and the pore walls are unimpeded. Traditional furnace annealing does not result in the porous structure as the heating rates are too slow to vaporize out the pitch, thereby illustrating the advantage of fast thermal processing. The resultant porous graphite was prelithiated and used as an anode in lithium ion capacitors. The porous graphite when lithiated had a specific capacity of 200 mAh/g at 100 mA/g. The assembled lithium ion capacitor demonstrated an energy density as high as 75 Wh/kg when cycled between 2.2 V to 4.2 V.
Preprint
|
|
|
Materials Science, Other; surface; textiles; flame retardant; plasma; ultraviolet; durability; phosphorus; nitrogen; polyurethane; thermal analysis; scanning electron microscopy
Online: 8 April 2018 (11:59:49 CEST)
|
|
Share this article with
×
Conventional flame retardant (FR) application processes for textiles involve aqueous processing which is resource intensive in terms of energy and water usage. Recent research using sol-gel and layer-by-layer chemistries, while claimed to be based on more environmentally-sustainable chemistry, still require aqueous media with the continuing problem of water management and drying processes being required. This paper outlines the initial forensic work to characterise commercially produced viscose/flax, cellulosic furnishing fabrics which have had conferred upon them durable flame retardant (FR) treatments using a novel, patented atmospheric plasma/UV excimer laser facility for processing textiles with the formal name - Multiplexed Laser Surface Enhancement (MLSE) system. This system (MTIX Ltd., UK), is claimed to offer the means of directly bonding of flame retardant precursor species to the component fibres introduced either before plasma/UV exposure or into the plasma/UV reaction zone itself, thereby eliminating a number of wet processing cycles. Nine commercial fabrics, pre-impregnated with a semi-durable, proprietary FR finish and subjected to the MLSE process have been analysed for their flame retardant properties before and after a 40 °C 30 min water soak. For one fabric, the pre-impregnated fabric was subjected to a normal heat cure treatment which conferred the same level of durability as the plasma/UV-treated analogue. TGA and LOI were used to further characterise their burning behaviour and the effect of the treatment on surface fibre morphologies were assessed. Scanning electron microscopy indicated that negligible changes had occurred to surface topography of the viscose fibres occurred during plasma/UV excimer processing.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; volatile renewable resources; microbial infection; secondary plant metabolites; antimicrobial essential oils; biologically-active polymers; plasma-assisted technique
Online: 5 April 2018 (03:32:08 CEST)
|
|
Share this article with
×
The persistent issue of bacterial and fungal colonization of artificial implantable materials and decreasing efficacy of conventional systemic antibiotics used to treat implant-associated infections has led to the development of a wide range of antifouling and antibacterial strategies. This article reviews one such strategy where inherently biologically active renewable resources, i.e. secondary plant metabolites (SPMs) and their naturally occurring combinations (i.e. essential oils) are used for surface functionalization and synthesis of polymer thin films. With a distinct mode of antibacterial activity, broad spectrum of action and diversity of available chemistries, secondary plant metabolites present an attractive alternative to conventional antibiotics. However, their conversion from liquid to solid phase without significant loss of activity is not trivial. Using select examples, this article shows how plasma techniques provide a sufficiently flexible and chemically reactive environment to enable the synthesis of biologically-active polymer-coatings from volatile renewable resources.
Preprint
|
|
|
Materials Science, General Materials Science; photocatalyst; flower-like SnS2; nanocomposites; visible light; methylene blue
Online: 3 April 2018 (10:53:52 CEST)
|
|
Share this article with
×
Semiconductor materials have been shown to have better photocatalytic behavior and can be utilized for the photodegradation of organic pollutants. In this work, three-dimensional flower-like SnS2 were synthesized by a facile hydrothermal method. Core-shell structured SiO2@α-Fe2O3 nanocomposites were then deposited on the top of the SnS2 flowers. The as-synthesized nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) and photoluminescence spectroscopy (PL). The photocatalytic behavior of the SnS2-SiO2@α-Fe2O3 nanocomposites was observed by observing the degradation of methylene blue (MB). The results show an effective enhancement of photocatalytic activity for the degradation of MB especially for the 15 wt. % SiO2@α-Fe2O3 nanocomposites on SnS2 flowers.
Preprint
|
|
|
Materials Science, Nanotechnology; enzyme; immobilization; organic-inorganic nanoflower; nanobiocatalysts
Online: 2 April 2018 (08:15:44 CEST)
|
|
Share this article with
×
A recent breakthrough in preparation of immobilized enzyme based biocatalysts achieving highly enhanced enzymatic activities and stabilities has become a great alternative to conventional immobilization techniques. The functional hybrid nanobiocatalysts (FHNs) fabricated in this immobilization composed of organic components (amino acid, peptide, protein, enzyme and plant extract) and inorganic components (various metal ions) give flower-like morphology with narrow size distribution and porous structure. The enzyme incorporated FHNs exhibite greatly enhanced catalytic activities and stabilities compared to free and conventionally immobilized enzymes under various experimental conditions. In addition to that, the FHNs consisting of other organic components act as Fenton-like reagents and show peroxidase-like activity owing to presence of metal ions and porous structure in the FHNs. This report basically focuses on preparation, characterization, and bioanalytical applications of the FHNs and explain mechanism of the FHNs formation and thier enhanced activities and stabilities.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; lubricant additives; boundary lubrication; ab initio molecular dynamics; tribochemistry; organophosphorus additives
Online: 30 March 2018 (09:57:07 CEST)
|
|
|
Share this article with
×
We performed for the first time to our knowledge fully ab initio molecular dynamics simulations of additive tribochemistry in boundary lubrication conditions. We consider an organophosphourus additive that has been experimentally shown to reduce friction in steel-on-steel sliding contacts thanks to the tribologically-induced formation of an iron phosphide tribofilm. The simulations allow us to observe in real time the molecular dissociation at the sliding iron interface under pressure and to understand the mechanism of iron phosphide formation. We discuss the role played by the mechanical stress by comparing the activation times for molecular dissociation observed in the tribological simulations at different applied loads with that expected on the basis of the dissociation barrier.
Preprint
|
|
|
Materials Science, Polymers & Plastics; cellulose nanofiber; boron nitride nanosheet; oxygen barrier; food packaging
Online: 30 March 2018 (09:46:30 CEST)
|
|
Share this article with
×
Herein, we introduce a boron nitride nanosheet (BNNS)-reinforced cellulose nanofiber (CNF) film as a sustainable oxygen barrier film that can potentially be applied in food packaging. Most of commodity plastics are oxygen-permeable. CNF exhibits an ideal oxygen transmittance rate (OTR) of <1 cc/m2/day in highly controlled conditions. A CNF film typically fabricated by the air drying of a CNF aqueous solution reveals an OTR of 19.08 cc/m2/day. The addition of 0-5 wt% BNNS to the CNF dispersion before drying results in a composite film with highly improved OTR, 4.7 cc/m2/day, which is sufficient for meat and cheese packaging. BNNS as a 2D nanomaterial increases the pathway of oxygen gas and reduces the chances of pin-hole formation during film fabrication involving water drying. In addition, BNNS improves the mechanical properties of the CNF films (Young’s modulus and tensile strength) without significant elongation reductions, probably due to the good miscibility of CNF and BNNS in the aqueous solution. BNNS addition also produces negligible color change, which is important for film aesthetics. An in vitro cell experiment was performed to reveal the low cytotoxicity of the CNF/BNNS composite. This composite film has great potential as a sustainable high-performance food packaging material.
Preprint
|
|
|
Materials Science, General Materials Science; Cholesteric Blue Phase III; nonlinear viscoelasticity; disclination network; fracture
Online: 29 March 2018 (12:00:13 CEST)
|
|
Share this article with
×
Nonlinear rheological properties of chiral crystal cholesteryl oleyl carbonate (COC) in blue phase III are investigated under different shear deformations; large amplitude oscillatory shear, step shear deformation, and continuous shear flow. Rheology of the liquid crystal is significantly affected by structural rearrangement of defects under shear flow. One of the examples on the defect-mediated rheology is the blue phase rheology. Blue phase is characterized by three dimensional network structure of the disclination lines. It has been numerically studied that the rheological behavior of the blue phase is dominated by destruction and creation of the disclination networks. In this study, we find that the nonlinear viscoelasticity of BPIII is characterized by the fracture of the disclination networks. Depending on the degree of the fracture, the nonlinear viscoelasticity is divided into two regimes; the weak nonlinear regime where the disclination network locally fractures but still show elastic response, and the strong nonlinear regime where the shear deformation breaks up the networks, which results in a loss of the elasticity. Continuous shear deformation reveals that a series of the fracture process delays with shear rate. The shear rate dependence suggests that force balance between the elastic force acting on the disclination lines and the viscous force determines the fracture behavior.
Preprint
|
|
|
Materials Science, General Materials Science; Fe-6.5wt.% Si alloy; hot bar rolling; microstructure; texture; mechanical property
Online: 29 March 2018 (06:15:08 CEST)
|
|
Share this article with
×
Cylindrical Fe-6.5wt.% Si bars with 7.5 mm in diameter were successfully fabricated from as cast ingot through three rolling stages within 10 passes: rough rolling at 850–900 °C and 8–10 m/min, medium rolling at 800–850 °C and 10–15 m/min, and finish rolling at 800–850 °C and 12–18 m/min. The evolution of microstructure, texture and ordered structure, and the mechanical property are investigated. The results showed that the grains were refined by the hot bar rolling. Area fractions of the {100}<011> oriented grains and the {011}<100> oriented grains decreased to 0 during the hot bar rolling. Whereas, the {100}<001> component, the {011}<211> component and the {112}<110> component increased, and γ fiber with {111}<110> component was dominant. DO3 ordered phase were suppressed, and B2 ordered domains were refined after the hot bar rolling. Ductility of the as rolled bar was higher than that of the rotary swaged bar, due to the absence of the DO3 ordered phase and the fine grains in the rolled bar. Hence, the hot bar rolling technology is an excellent process to fabricate the Fe-6.5wt.% Si bars.
Preprint
|
|
|
Materials Science, Surfaces, Coatings & Films; accelerated weathering test; color change; poplar OSB; wettability
Online: 29 March 2018 (04:38:44 CEST)
|
|
Share this article with
×
Oriented strand board (OSB) panels are widely marketed for several applications, from building to packaging. The manufacturing of poplar OSB started recently in Northern Italy representing a relevant innovation in the sector since this product is usually made of coniferous wood. The thermal treatment is widely used for reducing the hygroscopicity of wood-based products, nonetheless it influences the mechanical behavior and degrades the main components of wood, which can affect their finishing. Therefore, it is important to know the properties of the treated surfaces. To this purpose, in this study a lot of OSB panels, made of poplar wood, 15 mm thick and with a density of 590 kg/m3, were thermally treated under vacuum conditions at 190 °C for 2 h and then subjected to accelerated weathering. The changes in color and in wettability due to treatment and accelerated weathering were studied. The thermal treatment determined a significant darkening of the color; the accelerated weathering darkened the untreated surfaces and, on the opposite, lightened the thermo-treated surfaces. The wettability decreased after thermal treatment and increased after weathering, more evidently in treated panels. Overall, this study improves the knowledge about the behavior of the surface of thermo-treated poplar OSB, which is relevant for the industrial coating of this product.
Preprint
|
|
|
Materials Science, Metallurgy; superalloy; double vacuum smelting; cogging; inclusion.
Online: 28 March 2018 (09:38:29 CEST)
|
|
Share this article with
×
Cogging is a key part in the production process of superalloy, but inclusions affect the performance of superalloy. It is therefore particularly important to study the effects of cogging on the inclusions in superalloy. In our study, the superalloy GH4738 was made by double vacuum smelting. Cogging was performed by unidirectional drawing, upsetting and drawing, and upsetting/drawing with radial forging. The types and distributions of the inclusions after the three cogging processes were analyzed using scanning electron microscopy, energy dispersive spectroscopy, and software such as Image Pro Plus. The results showed that double vacuum smelting essentially determined the types of the inclusions in the GH4738 superalloy. Four types of inclusions were found in the experiments: TiC-TiN-Mo-S composite, TiC-TiN composite, Ce-Mo-S composite, and SiC inclusions. In the case of cogging by unidirectional drawing, the average size of the inclusions first decreased and then increased, from the center to the edge. In the case of upsetting and drawing, and upsetting/drawing with radial forging, the average size of inclusions decreased from the center to the edge.