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Materials Science, Biomaterials; Tricalcium phosphate putty scaffold; bioactive ceramics; bone formation, osteogenesis, osteogenic markers, hard tissue histology; immunohistochemical analysis; split-mouth design; sinus floor augmentation; bone grafting materials
Online: 22 June 2017 (18:33:01 CEST)
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This study examines the effect of a hyaluronic acid (HyAc) containing tricalcium phosphate putty scaffold material (TCP-P) and of a particulate tricalcium phosphate (TCP-G) graft on bone formation, volume stability and osteogenic marker expression in biopsies sampled 6 months after bilateral sinus floor augmentation (SFA) in 7 patients applying a split-mouth design. Biopsies were processed for immunohistochemical analysis of resin embedded sections. Sections were stained for collagen type I (Col I), alkaline phosphatase (ALP), osteocalcin (OC) and bone sialoprotein (BSP). Furthermore, the bone area and particle area fraction were determined histomorphometrically. Cone-beam CT data recorded after SFA and 6 month later were used for calculating the graft volume at these two time points. TCP-P displayed more advantageous surgical handling properties and a significantly greater bone area fraction and smaller particle area fraction. This was accompanied by significantly greater expression of Col I and BSP and in osteoblasts and osteoid and a less pronounced reduction in grafting volume with TCP-P. SFA using both types of materials resulted in formation of sufficient bone volume for facilitating stable dental implant placement with all dental implants having been in function without any complications for 6 years. Since TCP-P displayed superior surgical handling properties and greater bone formation than TCP-G, without the Hyac hydrogel matrix having any adverse effect on bone formation or graft volume stability, TCP-P can be regarded as excellent grafting material for SFA in a clinical setting.
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Materials Science, Biomaterials; materials science; nanoscience and nanotechnology; tiny-sized particles; electron-dynamics; nanomedicine applications
Online: 22 June 2017 (11:54:32 CEST)
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Various types of metallic nanoparticles are being used, with coating or bare surface, for various biological and medical applications including the stent ones. Our recent experimental studies reveal that atoms of nanoparticles reveal more or less stretching or deformation depending on the impinging electron streams and the process of synergy. Present study reports metallic tiny-sized particles where electron-dynamics of their atoms safeguard the possible certain impact of application at target. Thus, they may have the pronounced effects on their usage for nanomedicine applications and others –either effective or defective.
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Materials Science, General Materials Science; heat energy; photon energy; materials science; nanoscale phenomenon; atomic scale phenomenon
Online: 20 June 2017 (05:07:01 CEST)
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Technology is in the way to reach in its climax but the basic understanding of science in many phenomena is still awaited despite the fact that nature justifies all those. Scientific research reveals strong analogy between electron and photon. Atoms that execute suitable electronic transitions, on absorbing heat energy at shunt level, excite their electrons. De-excitation of an electron under the gravitational force of its nucleus, where inertia is involved, results into depicting energy in the shape like Gaussian distribution. The wavelength of photon remains in inter-state electron’s gap where the source of generating energy in wave-like fashion is due to confined electron-dynamics of that atom eligible to execute electronic transition; energy configures under electron’s trajectory while excitation period is due to inertia-levitation-inertia behaviours and energy configures under electron’s trajectory while de-excitation period is due to inertia-gravitation-inertia behaviours. Silicon atom is a model system of it. Uninterrupted confined inter-state electron’s motion results into configure force energy that can travel immeasurable length where interruption from the point of generation termed it a photon. Such photons increase wavelength under decreasing energy. Here, I discuss that heat energy is due to merged photons or squeezed photons and photonic current is due to the configuring energy in inter-state electron’s gap under confined electron-dynamics of the atom. Force of repulsion or attraction in certain materials engages the phenomenon of levitism or gravitism where inertia is exempted. Structural motifs and dynamics are subjected to characteristic photons as long as atoms are dealing neutral behavior of field forces. A structural design delivers straight-forward application on dealing photons of certain wavelengths. Here, heat energy and photon energy explore matter at electron level. Thus, devise science to describe.
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Materials Science, Biomaterials; β-amyloid 42; differential pulse voltammetry; Neuro-degenerative disorders; ferrocyanide/ferricyanide redox couple
Online: 13 June 2017 (18:14:57 CEST)
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A simple in vitro biosensor for the detection of β-amyloid 42 in phosphate-buffer saline (PBS) and undiluted human serum was fabricated and tested based on our platform sensor technology. The bio-recognition mechanism of this biosensor was based on the effect of the interaction between antibody and antigen of β-amyloid 42 to the redox couple probe of K4Fe (CN) 6 and K3Fe (CN) 6. Differential pulse voltammetry (DPV) served as the transduction mechanism measuring the current output derived from the redox coupling reaction. The biosensor was a three-electrode electrochemical system, and the working and counter electrodes were 50 nm thin gold film deposited by sputtering technique. The reference electrode was a thick-film printed Ag/AgCl electrode. Laser ablation technique was used to define the size and structure of the biosensor. Cost-effective roll-to-roll manufacturing process was employed in the fabrication of the biosensor making it simple and relatively inexpensive. Self-assembled monolayers (SAM) of 3-Mercaptopropionic acid (MPA) was employed to covalently immobilize the thiol group on the gold working electrode. A carbodiimide conjugation approach using N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC) and N–hydroxysuccinimide (NHS) was undertaken for cross-linking antibody of β-amyloid 42 to the carboxylic groups on one end of the MPA. The antibody concentration of β-amyloid 42 used was 18.75µg/mL. The concentration range of β-amyloid 42 in this study was from 0.0675µg/mL to 0.5µg/mL for both PBS and undiluted human serum. DPV measurements showed excellent response in this antigen concentration range. Interference study of this biosensor was carried out in the presence of Tau protein antigen. Excellent specificity of this β-amyloid 42 biosensor was demonstrated without interference by other species such as T-tau protein.
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Materials Science, Biomaterials; EGF; PS NPs; cellular uptake; clathrin-mediated endocytosis
Online: 2 June 2017 (05:23:52 CEST)
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The interaction between nanoparticles and cells has been studied extensively, but most research has focused on the effect of various nanoparticle characteristics, such as size, morphology, and surface charge, on the cellular uptake of nanoparticles. In contrast, there have been very few studies to assess the influence of cellular factors, such as growth factor responses, on the cellular uptake efficiency of nanoparticles. The aim of this study was to clarify the effects of epidermal growth factor (EGF) on the uptake efficiency of polystyrene nanoparticles (PS NPs) by A431 cells, a human carcinoma epithelial cell line. The results showed that EGF enhanced the uptake efficiency of A431 cells for PS NPs. In addition, inhibition and localization studies of PS NPs and EGF receptors (EGFRs) indicated that cellular uptake of PS NPs is related to the binding of EGF-EGFR complex and PS NPs. Different pathways are used to enter the cells depending on the presence or absence of EGF. In the presence of EGF, cellular uptake of PS NPs is via clathrin-mediated endocytosis, whereas in the absence of EGF, uptake of PS NPs does not involve clathrin-mediated endocytosis. Our findings indicate that EGF enhances cellular uptake of PS NPs by clathrin-mediated endocytosis. This result could be important for developing safe nanoparticles and their safe use in medical applications.
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Materials Science, Biomaterials; hydroxyapatite, xenografts; implant design; implant surface
Online: 1 June 2017 (06:19:41 CEST)
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The aim of the present study was to monitor implant stability after sinus floor elevation with two biomaterials during the first 6 months of healing by a resonance frequency analysis (RFA), and how physico-chemical properties affect the implant stability quotient (ISQ) at the placement and healing sites. Bilateral maxillary sinus augmentation was performed in 10 patients in a split-mouth design using a bobine HA (BBM) as a control and porcine HA (PBM). Six months after sinus lifting, 60 implants were placed in the posterior maxilla. The ISQ was recorded on the day of surgery from RFA at T1 (baseline), T2 (3 months), and T3 (6 months). Statistically significant differences were found in the ISQ values during the evaluation period. The ISQ (baseline) was 63.8±2.97 for BBM and 62.6±2.11 for PBM. The ISQ (T2) was ~ 73.5±4.21 and 67±4.99, respectively. The ISQ (T3) was ~ 74.65±2.93 and 72.9±2.63, respectively. All the used HAs provide osseointegration and statistical increases in the ISQ at baseline, T2 and T3 (follow-up), respectively. The BBM, sintered at high temperature with high crystallinity and low porosity, presented higher stability, which demonstrates that variations in the physico-chemical properties of a bone substitute material clearly influence implant stability.
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Materials Science, Nanotechnology; graphene; chemical vapor deposition; nanomaterials
Online: 30 May 2017 (09:50:07 CEST)
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We report the growth of graphene at a low temperature using the cold wall chemical vapor deposition technique (CWCVD). Few layered (~6-8 layers) graphene were grown on nickel-coated silicon with acetylene as the precursor gas. The advantage of the combination of the acetylene (as a carbon feedstock) and the nickel catalyst was the lowering of the graphene growth temperature. Nickel coated silicon samples were pre-treated (heat treatment in inert atmosphere) before the growth and the effect of the pre-treatment on the catalyst as well as on the grown film was studied. The final samples were characterized with scanning electron microscopy and Raman spectroscopy. In CWCVD route, the heating of only the substrate holder enabled high heating and cooling rates, which, along with the control over partial pressure of the precursor gas had profound effect on the formation of graphene. In the best sample we have achieved almost equal intensity of the G and 2D peaks in Raman spectrum, which implied about ~6-8 layers of Graphene. The defect peak (the D band) was extremely small in the sample and it was attributed to the ripples and the underlying roughness of the nickel film. We analyzed that a proper choice of the thickness of catalyst layer and a higher cooling rate after graphene growth it would be possible to obtain monolayered graphene. Similar samples grown in a normal atmospheric CVD (with some engineered design to promote fast cooling) were also compared with the cold wall CVD grown samples and plasma assisted CWCVD, and cold-wall CVD demonstrated a better control over the quality of graphene film through the fast cooling and a controlled partial pressure of the precursor gas.
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Materials Science, Polymers & Plastics; abrasive flow machining; a helical passageway; surface roughness, mold core
Online: 29 May 2017 (18:54:24 CEST)
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Due to the fact that abrasive media can deform flexibly in abrasive flow machining (AFM) making this method easily to polish the complex holes and the curved surface of the hard machining shapes. Although abrasive media dominate the polishing behavior in AFM process, the mechanism of the abrasive media are not easy to understand because of the high viscous gels, therefore, many finishing works need lots of time to design AFM process. Power laws of the abrasive gels is studied here to evaluate the non-Newtonian flow of abrasive gels in complex holes polishing firstly, at the mean time different abrasive gels are utilized to finish the complex holes to follow the results by non-Newtonian flow calculation. Moreover, traditional AFM has difficulty to achieve a uniform roughness of radial distribution in the complex holes polishing because of the non-uniform abrasive forces. So a helical passageway is proposed to create a multiple motion of abrasive medium and to obtain the even surface of the complex holes in AFM process.
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Materials Science, Surfaces, Coatings & Films; Rare earth rich magnesium alloy, Plasma Electrolytic Oxidation, PEO, Microstructure, Fatigue
Online: 25 May 2017 (18:24:45 CEST)
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Rare earth rich magnesium alloys are used in aerospace and automotive fields because of their high specific strength and good castability. However, due to their low corrosion resistance, protective surface treatments, such as conversion coating or electroless plating are necessary, when they have to be used in humid or corrosive environments. The present study was aimed to evaluate the effect of Plasma Electrolytic Oxidation (PEO) and different surface roughness (Ra≈0.8 μm and Ra≈0.3 μm) on the rotating bending fatigue of an innovative Mg alloy, with a high content of Nd (up to 3.1 wt%) and Gd (up to 1.7 wt %). Fatigue tests revealed a 15% decrease in the fatigue strength of the PEO treated alloy (fatigue strength = 88 MPa) with respect to the bare alloy (fatigue strength = 103 MPa). The reduction of fatigue strength was mainly due to the residual tensile stresses induced by the PEO treatment. The effect of surface roughness on the bare alloy was, instead, negligible. The mechanisms of crack initiation were similar in the untreated and PEO treated alloy, with crack nucleation sites located in correspondence of large facets of the cleavage planes.
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Materials Science, Polymers & Plastics; soy flour; lignin; adhesive; plywood; bond strength
Online: 23 May 2017 (16:29:41 CEST)
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The aim of this study was to using a lignin based resin (LB) to improve the performance of the soy flour based adhesive. Soy flour (SF), polyamidoamine-epichlorohydrin (PAE), LB was used to develop a plywood adhesive. The solid content and viscosity of the adhesive, functional groups, thermo-stability, and crystallinity of the cured adhesive were characterized and the performance of the resultant adhesive was evaluated by fabricating three-ply plywood. Results showed using LB and PAE mixture to modify SF adhesive improves dry and wet bond strength by 66.3 and 184.2%. PAE contributed more for the wet bond strength improvement and the LB contributed more for the dry bond strength. The improvement was attributed to: 1) LB/PAE reacted with the functions of the soy protein and form a cross-linking network; 2) Polycondensation reaction between LB molecules further improved crosslinking density of the adhesive and formed a interpenetration structure with crosslinked protein; 3)The easy penetration of LB on wood surface and formed more interlock with wood. The denser structure created by LB and PAE mixture improved the thermal stability and decreased the crystallinity of cured adhesive. The usage of the LB and PAE mixture increased solid content by 35.5%, meanwhile, makes its viscosity acceptable for the industrial application.
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Materials Science, Polymers & Plastics; single fiber; cutting; fracture morphology; failure mechanism
Online: 22 May 2017 (05:29:48 CEST)
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The present study investigates the failure mechanisms of industrial fiber materials, using a custom designed fiber cutting performance test bench. The fracture morphologies of single PA6 fibers are examined by scanning electron microscopy. The analysis reveals that fiber cutting can be distinguished according to four distinct stages of fiber failure represented by shearing, cutting, brittle fracture, and tensile failure, which are the result of different mechanisms active during the processes of crack initiation, extension and fracture. The results of fractographic analysis are further verified by an analysis of the blade assembly speed with respect to time over the entire fracture failure process based on high-speed camera data. The results of fractographic analysis and blade assembly speed are fully consistent.
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Materials Science, Nanotechnology; green synthesis; silver nanoparticles; particle size; antibacterial efficacy
Online: 17 May 2017 (11:22:09 CEST)
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Silver nanoparticles (AgNPs) have been demonstrated to restrain bacterial growth while maintaining the minimal risk in development of bacterial resistance and human cell toxicity that conventional silver compounds exhibit. Several physical and chemical methods have been reported to synthesize AgNPs. However, these methods are expensive and involve heavy chemical reduction agents. An alternative approach to produce AgNPs in a cost-effective and environmentally friendly way employs a biological pathway using various plant extracts to reduce metal ions. The size control issue and the stability of nanoparticles remain some of the latest challenges in such methods. In this study, we used two different concentrations of fresh leaf extract of the plant Arbutus Unedo (LEA) as a reducing and stabilizing agent to produce two size variations of AgNPs. UV-Vis spectroscopy, Dynamic Light Scattering, Transmission Electron Microscopy and zeta potential were applied for the characterization of AgNPs. Both AgNP variations were evaluated for their antibacterial efficacy against the gram-negative species Escherichia coli and Pseudomonas aeruginosa, as well as the gram-positive species Bacillus subtilis and Staphylococcus epidermidis. Although significant differences have been achieved in the nanoparticles’ size by varying the plant extract concentration during synthesis, the antibacterial effect was almost similar.
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Materials Science, Nanotechnology; halloysite nanotube(HNT); hybrid composite; aramid fiber; basalt fiber; interfacial property; fiber reinforced composite; aggregation
Online: 16 May 2017 (07:39:07 CEST)
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Hybrid fiber reinforced composites can be controlled by price, weight and various mechanical properties depending on fiber ratio and lamination method. Despite these excellent hybrid properties, there is a disadvantage that inter-laminar fracture due to external impact, which is the biggest weakness of fiber reinforced composite materials, is weak. The test specimens were prepared by using a vacuum bag method, which is manufactured by using an autoclave device. The pre-preg is manufactured in the form of a B-stage. In the process of fabricating the nanoparticle pre-preg, the homogeneizer using an ultrasonic wave was used to disperse the epoxy subject without the curing agent into nanoparticles. The dispersion of the nanoparticles was dispersed by the weight of the epoxy resin. This is to take into account the cohesion of HNT and to understand the range of cohesion of HNT in a matrix with viscosity and its phenomenon. According to the Comparison of the interlayer interfacial properties and mechanical properties of Aramid / Basalt fiber hybrid composites by HNT addition, the fracture toughness, ILSS and bending strength of specimens with HNT content of more than a certain level were decreased because of the aggregation of HNT.
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Cheolhwan Jeong,
Hyung-Mo Kim,
So Yeon Park,
Myeong Geun Cha,
San Kyeong,
Xuan-Hung Pham,
Eunil Hahm,
Yuna Ha,
Dae Hong Jeong,
Bong-Hyun Jun,
Yoon-Sik Lee
Materials Science, Nanotechnology; surface-enhanced Raman scattering; magnetic aggregation; on-site detection
Online: 15 May 2017 (11:53:34 CEST)
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We report magnetic silver nanoshells (M AgNSs) that have both magnetic and SERS properties for SERS-based detection. The M AgNSs are composed of hundreds of Fe3O4 nanoparticles for rapid accumulation and bumpy silver shell for sensitive SERS detection by near-infrared laser excitation. The intensity of the SERS signal from the M AgNSs was strong enough to provide single particle-level detection. We obtained much stronger SERS signal intensity from the aggregated M AgNSs than from the non-aggregated AgNSs. 4-Fluorothiophenol was detected at concentrations as low as 1 nM, which corresponds to 0.16 ppb. The limit of detection for tetramethylthiuram disulfide was 10 μM, which corresponds to 3 ppm. The M AgNSs can be used to detect trace amounts of organic molecules using a portable Raman system.
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Materials Science, Nanotechnology; lithium-ion batteries; anode materials; MnO; co-precipitation; T-shaped microchannel reactor
Online: 11 May 2017 (07:49:10 CEST)
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Porous MnO/C microspheres have been successfully fabricated by a fast co-precipitation method in a T-shaped microchannel reactor. The structures, compositions and electrochemical performances of the obtained MnO/C microspheres are characterized by X-ray diffraction, emission scanning electron microscopy, transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller analysis, charge-discharge testing, cyclic voltammograms, and electrochemical impedance spectra. Experimental results reveal that the as-prepared MnO/C, with a specific surface area of 96.66 m2·g–1 and average pore size of 24.37 nm, exhibits excellent electrochemical performance, with a discharge capacity of 655.4 mAh·g–1 after cycling 50 times at 1 C and capacities of 808.3, 743.7, 642.6, 450.1, and 803.1 mAh·g–1 at 0.2, 0.5, 1, 2, and 0.2 C, respectively. Moreover, the controlled method of using a micro-channel reactor, which can produce larger specific surface area porous MnO/C with improved cycling performance by shortening lithium-ion diffusion distances, can be easily applied in real production on a large-scale.
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Materials Science, General Materials Science; binary liquid alloy; chemical ordering; sodium; theoretical study; Warren-Cowley parameter
Online: 9 May 2017 (11:28:07 CEST)
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A simple model has been used to investigate the nature of chemical order in Na-Pb and Na-Hg liquid binary alloy at 700K and 673K respectively. The energy parameter obtained from the model was used to calculate the concentration dependent mixing properties such as Gibb’s free energy of mixing, Concentration fluctuations in the long wavelength limit and the Warren-Cowley chemical short range order parameter. Results obtained showed that both alloys are hetero-coordinated throughout the entire concentration and there is tendency for segregation and demixing to take place in the liquid alloys. We observed that Na-Hg liquid alloy is more strongly interacting binary alloy and chemically ordered than Na-Pb liquid alloy.
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Materials Science, Polymers & Plastics; transparent electrode; organic photovoltaic; distributed Bragg reflector
Online: 9 May 2017 (11:09:37 CEST)
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We demonstrated an ITO-free, highly transparent organic solar cell with the potential to be integrated into window panes for energy harvesting purposes. A transparent, conductive ZnO/Ag/ZnO multilayer electrode and a Ag:Ca thin film electrode were used in this transparent device as the bottom and top electrode, respectively. To further improve the transmittance of the solar cell, the thickness of the top ZnO layer was investigated by both experiment and simulation. An average visible transmittance of > 60% was reached, with a maximum transmittance of 73% at 556 nm. Both top and bottom illumination of the solar cell generated comparable power conversion efficiencies, which indicates the wide application of this solar cell structure. In addition, we fabricated distributed Bragg reflector mirrors with sputtered SiO2 and TiO2, which efficiently increased the power conversion efficiency over 20% for the solar cells on glass and PET substrates,
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Materials Science, General Materials Science; Thermoelectric Materials; Energy Harvesting; CoSb3/ZT
Online: 8 May 2017 (18:44:39 CEST)
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Thermoelectric materials may be used in devices as thermoelectric “air conditioner” in a smart house for improved energy efficiency. Energy harvesting uses ambient energy to generate electricity. It provides potentially low-cost, maintenance-free, long-life equipment by reducing the need for batteries or power chords. Energy harvesting (EH) is also known as power harvesting or energy scavenging. EH is considered to give benefits related to environmental friendliness, safety, security, convenience and affordability. EH can be used for brand enhancing. Technically, it can be used to make new things possible depending on visionary engineering. The variety of thermoelectric (TE) materials that can be used in energy harvesting is quite large, and the optimal material for a given application depends mainly on the temperature range in which the material is to be used. In this work we study the development and characterization of thermoelectric materials which were prepared by two different method, which were: a) ball-milling followed by sintering and b) ball-milling, microwave synthesis, high energy planetary ball milling, and sintering. Finally, we study the thermoelectric properties, calculate the band gaps and the ZT for the thermoelectric materials.
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Materials Science, Polymers & Plastics; fibrous composites; periodic structure; fiber contiguity; interphase; thermal conductivities
Online: 8 May 2017 (10:31:50 CEST)
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In this paper, an advanced geometric model to simulate the periodic structure of unidirectional fibrous composites is presented. This model takes into consideration the influence of fiber contiguity in parallel with the concept of interphase on the thermomechanical properties of the overall material. Next, by the use of this model the authors propose closed – form expressions to estimate the longitudinal and transverse thermal conductivity of this type of composites.
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Materials Science, General Materials Science; Pb(Zn1/3Nb2/3) O3-9%PbTiO3; relaxor ferroelectric crystals; structure phase transition; electromechanical coupling factor
Online: 1 May 2017 (10:35:10 CEST)
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Piezoelectric properties are of significant importance to medical ultrasound, actuators, sensor, and countless other device applications. The mechanism of piezoelectric properties can be deeply understood from structure evolutions. In this paper, we report a diagram of structure evolutions of the Pb(Zn1/3Nb2/3)0.91Ti0.09O3 (PZN-9PT) single crystal with excellent piezoelectric properties among the orthorhombic, tetragonal, and cubic phases with temperature increasing from room temperature to 220 C. Through fitting the temperature dependence XRD curves with Gauss and Lorenz functions, we obtained the evolutions of the content ratio of three kinds of phases (orthorhombic, tetragonal and cubic) and the lattice parameters of the PZN-9PT system with the changes of temperature. The XRD fitting results together with Raman and dielectric spectrums show that the phase transitions of PZN-9PT are a typical continuous evolution process, very similar to the phase transition of paraffin from solid to liquid. Additionally, resonance and anti-resonance spectrum show excellent piezoelectric properties of the crystals, which probably originate from the nano twin domains, as demonstrated by the TEM images. Of particular attention is that the thickness electromechanical coupling factor kt is up to 72%.
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Materials Science, Metallurgy; grain boundary sliding; incompatibility stresses; anisotropic elasticity; heterogeneous elasticity; lattice rotations
Online: 1 May 2017 (09:06:32 CEST)
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Non-uniform grain boundary sliding can induce strain and rotation incompatibilities at perfectly planar interfaces. Explicit analytic expressions of stress and lattice rotation jumps are thus derived at a planar interface in the general framework of heterogeneous anisotropic thermo-elasticity with plasticity and grain boundary sliding. Both elastic fields are directly dependent on in-plane gradients of grain boundary sliding. It is also shown that grain boundary sliding is a mechanism that may relax incompatibility stresses of elastic, plastic and thermal origin although the latter are not resolved on the grain boundary plane. This relaxation may be a driving force for grain boundary sliding in addition to the traditionally considered local shears on the grain boundary plane. Moreover, the obtained analytic expressions are checked by different kinds of bicrystal shearing finite element simulations allowing grain boundary sliding and where a pinned line in the interface plane aims at representing the effect of a triple junction. A very good agreement is found between the analytic solutions and the finite element results. The performed simulations particularly emphasize the role of grain boundary sliding as a possible strong stress generator around the grain boundary close to the triple line because of the presence of pronounced gradients of sliding.
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Materials Science, Surfaces, Coatings & Films; polyester fabrics; surface modification; sulfuric acid; polypyrrole; deposition; conductivity
Online: 1 May 2017 (08:48:17 CEST)
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A simple and effective surface modification of polyester fabrics with sulfuric acid to improve the interfacial deposition of polypyrrole was presented in our work. A range of sulfuric acid concentrations were analyzed by studying water contact angle. Effect of sulfuric acid modification on the deposition of polypyrrole was investigated by sheet resistance and color depth of fabric samples. Polyester fabrics coated with polypyrrole layer were confirmed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-Ray diffraction spectra (XRD), Fourier transform infrared spectroscopy (FTIR). XPS showed that sulphur containing functional groups were obviously appeared on the polyester fiber surface after modification, which were advantageous to promote the deposition of polypyrrole onto polyester fabrics. The improved deposition increased electrical conductivity of fabric samples.
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Materials Science, Surfaces, Coatings & Films; electroluminescent; 3D-printing; rapid prototyping; light-emitting fibers; roll-to-roll process
Online: 1 May 2017 (07:25:50 CEST)
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There is a growing interest in fibers supporting optoelectrical properties for textile and wearable display applications. Solution-processed electroluminescent (EL) material systems can be continuously deposited onto fiber or yarn substrates in a roll-to-roll process, making it easy to scale manufacturing. It is important to have precise control over layer deposition to achieve uniform and reliable light emission from these EL fibers. Slot-die coating offers this control and increases the rate of EL fiber production. Here, we report a highly adaptable, cost-effective 3D printing model for developing slot dies used in automatic coating systems. The resulting slot-die coating system enables rapid, reliable production of alternating current powder-based EL (ACPEL) fibers and can be adapted for many material systems. The benefits of this system over dip-coating for roll-to-roll production of EL fibers are demonstrated in this work.
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Materials Science, Metallurgy; 7075 Aluminum alloy; eutectic mixture; formability; hardness.
Online: 26 April 2017 (18:12:46 CEST)
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Strain induced melt activation process (SIMA) creates a globular microstructure which improves the hardness and ultimate tensile stress (UTS) of 7075 aluminum alloys. But, at the grain boundaries of SIMA processed 7075 aluminum alloy, presence of continuous and brittle intermetallic compounds and the eutectic structure result in decreasing mechanical properties, such as elongation, formability and etc. Hence, in order to improve microstructure and formability of 7075 aluminum alloy respect to SIMA process, a new process was done that is called two-step strain induced melt activation (TSSIMA). This process, which has been mentioned in the experimental procedure section, both organized globular structure and significantly modified the microstructure of the alloy compared to that of the SIMA method. It promoted discontinuity and more homogeneity in distribution of the precipitates and, approximately removed the eutectic mixture. Performing the rolling process on the alloy also revealed that it is more effective in formability enhancement in comparison with SIMA process. Also, it increased the hardness of 7075 aluminum alloy respect to that of SIMA process.
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Materials Science, Polymers & Plastics; polyurethane foams; castor oil; crude glycerol; biopolyols
Online: 20 April 2017 (04:27:10 CEST)
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Rigid polyurethane foams were synthesized using a renewable polyol from the simple physical mixture of castor oil and crude glycerol. The effect of the catalyst and blowing agent in the foams properties was evaluated. The use of physical blowing agent (cyclopentane and n-pentane) allowed obtaining foams with smaller cells in comparison with the foams produced with a chemical blowing agent (water). The increase of water content caused a decrease of density, thermal conductivity, compressive strength and Young's modulus, which indicates that the increment of CO2 production contributes to the formation of larger cells. Higher amount of catalyst in the foam formulations caused a slight density decrease and an increase small significance of thermal conductivity, compressive strength and Young's modulus values. These green foams presented properties that indicate a great potential to be used as thermal insulation, as density (23 - 41 kg m-3), thermal conductivity (0.0128 – 0.0207 W m-1 K-1), compressive strength (45 - 188 kPa) and Young's modulus (3 - 28 kPa). These biofoams are also environmental friendly alternatives and can aggregate revenue to biodiesel industry, contributing for reduction of this fuel prices.
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Materials Science, Biomaterials; polymethylmethacrylate PMMA; henna; physical properties; hardness; surface roughness
Online: 18 April 2017 (12:24:49 CEST)
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Statement of problem: Henna has been added to polymethylmethacrylate (PMMA) as a new type of antifungal agent; however, its effect on the latter’s physical properties has not been investigated. Purpose: This study aimed to evaluate the effect of the addition of various henna concentrations on the surface roughness and hardness of PMMA denture base material. Materials and Methods: A total of 99 specimens of rectangular-shaped (10×20×3 mm3) acrylic specimens were prepared from heat-cured acrylic resin. Specimens were divided into one control group without the addition of henna and five test groups, which were prepared by adding Yamani henna powder to acrylic powder at concentrations of 1wt%, 2.5wt%, 5wt%, 7.5wt%, and 10wt%. The polymer was added to the monomer before being mixed, packed, and processed using the conventional water bath method. After processing, specimens were finished and polished, then kept in distilled water for 48+2 h. A profilometer and Vickers hardness tester were used to measure surface roughness and hardness respectively. Statistical data analysis was conducted via SPSS version 20.0 (IBM, USA). Results: The addition of henna at varying concentrations significantly increased surface roughness values (P ≤ 0.01) while decreasing hardness (P ≤ 0.0001). The most favorable addition value was 1% henna between all henna groups. Conclusion: The addition of henna to the acrylic resin may negatively affect the surface properties of PMMA acrylic denture base.
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Materials Science, General Materials Science; ZnO; ceramic nanopowders; Segmented Flow Tubular Reactor (SFTR); Spark Plasma Sintering (SPS)
Online: 14 April 2017 (12:11:50 CEST)
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Nanopowders are continuously under investigation as they open new perspectives in numerous fields. There are two main challenges to stimulate their development: sufficient low-cost high throughput synthesis methods leading to a production with well-defined and reproducible properties, and for ceramics, conservation of their nanostructure after sintering. In this context, this paper presents the synthesis of a pure nanosized powder of ZnO (dv50 ~ 60 nm, easily redispersable) by using a continuous Segmented Flow Tubular Reactor (SFTR), which has previously shown its versatility and its robustness, ensuring a high powder quality and reproducibility over time. A higher scale of production can be achieved based on a “scale-out” concept by replicating the tubular reactors. The sinterability of ZnO nanopowders synthesized by the SFTR was studied, by natural sintering at 900 °C and 1100 °C, and Spark Plasma Sintering (SPS) at 900 °C. The performances of the synthesized nanopowder were compared to a commercial ZnO nanopowder of high quality. The samples obtained from the synthesized nanopowder could not be densified at low temperature by traditional sintering, whereas SPS led to a fully dense material after only 5 minutes at 900 °C, while limiting the grain growth and thus leading to a nanostructured material.
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Materials Science, Nanotechnology; carbon nanotube yarn; strain sensing; polymer; piezoresistivity; experimental
Online: 10 April 2017 (08:12:01 CEST)
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Carbon nanotube (CNT) yarns are fiber-like materials that exhibit excellent mechanical, electrical and thermal properties. More importantly, they exhibit a piezoresistive response that can be tapped for sensing purposes. The objective of this study is to determine experimentally the piezoresistive response of CNT yarns that are embedded in a polymeric medium while subjected to either compression or tension, and compare it with that of the free or unconstrained CNT yarns. The rationale for this study is the need to know the response of the CNT yarn while in a medium, which provides a lateral constraint to the CNT yarn thus mimicking the response of integrated CNT yarn sensors. The experimental program will include the fabrication of samples and their electromechanical characterization. The CNT yarns are integrated in polymeric beams and subjected to four-point bending, allowing the determination of their response under tension and compression. The electrical resistance data from an Inductance-Capacitance-Resistance (LCR) device is used with the data acquired from the mechanical testing system to determine the piezoresistive response of the CNT yarns. This data and information will be used for future modeling efforts and to study the phenomena that occur when CNT yarns are integrated in polymeric and composite materials and structures.
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Materials Science, Other; bornological set; bornological group
Online: 7 April 2017 (04:17:16 CEST)
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In this work, Further properties of bornological groups are studied to find the sufficient conditions to introduce a bornology on a group. In particular, we show that every left (right) translations in bornological groups are isomorphisms and therefore the bornological group's structures are homogeneous, and this property from the bornological group is not shared with bornological semigroups. Further, the boundedness of a bornological group can be deduced from its boundedness at the identity.
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Materials Science, Nanotechnology; lanthanides; fluorapatite; drug loading; nano carrier
Online: 5 April 2017 (11:26:48 CEST)
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Europium (Eu)-doped fluorapatite (FA) nanorods has a similar biocompatibility with hydroxyapatite (HA) in terms, attracted much attention as cell imaging biomaterials due to their luminescent property. Here, we will discuss the new feature of europium doped fluorapatite (Eu-FA) nanorods as anticancer drug carrier. Eu-FA nanorods was prepared using a hydrothermal method. The morphology, crystal structure, fluorescence and composition are investigated. The specific crystal structure, enabling an effective loading of drug molecules. Doxorubicin (DOX), used as an anticancer model drug, was shown to be effectively loaded onto the surface of the nanorods. The DOX release was fairly pH-dependent, occurring more rapidly at pH 5.5 than pH 7.4 was observed. The intracellular penetration of the DOX-loaded Eu-FA nanorods (Eu-FA/DOX) can be imaged in situ due to the self-fluorescence property. Treatment of melanoma A375 cells with Eu-FA/DOX elicited a more effective apoptosis rate than direct DOX treatment. Overall, Eu-FA show great promise for tracking and treating tumor, may potentially useful as a multifunctional carrier system to effectively load and sustainably deliver drugs.
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Materials Science, Nanotechnology; gelatin-oleic conjugate; self-assembled biodegradable nanoparticles; biomimetic shear stress; cell dynamic environment; cellular drug delivery; paclitaxel
Online: 4 April 2017 (10:59:02 CEST)
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Fluid flow in human body is generally known to influence a variety of cellular behaviors. Different nanoparticle properties as well as cell type, interaction with other cells and cellular environments also show significant effect on nanoparticle uptake and drug efficacy. The aim of this study was to evaluate the effect of shear stress on cellular behaviors of biocompatible and biodegradable nanoparticles to cancer cells (A549 cell lines) in a biomimetic microfluidic system. We prepared a gelatin-oleic conjugate (GOC) as an amphiphilic biomaterial to prepare self-assembled gelatin-oleic nanoparticles (GON). Coumarin-6 and paclitaxel were used as the fluorescence marker and model drug, respectively, and were loaded into GONs by incubation (C-GONs; PTX-GONs). Additionally, we evaluated the cellular uptake of fluorescence labeled C-GONs and the drug efficacy of PTX-GONs. The cellular uptake of C-GONs by A549 cells in the absence of shear stress revealed that the mean fluorescence intensity was slightly decreased compared to that in the presence of shear stress. The results also indicated that negatively charged PTX-GONs had a lower cancer killing effect under dynamic conditions than that under static conditions. It also suggested that fluidic shear stress did not significantly affect drug uptake and efficiency in case of PTX-GONs. The cellular interactions between nanoparticles and cells in drug delivery should be carefully examined according to the physicochemical properties of nanoparticles such as the type of materials, size and mainly surface charge in a biomimetic microfluidic condition.
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Materials Science, Nanotechnology; tin oxide pellets; doping; HRTEM analysis; CO; sensitivity
Online: 4 April 2017 (08:16:13 CEST)
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In this work, we report synthesis of Cu, Pt and Pd doped SnO2 powders and their comparative CO gas sensing studies. Dopants were incorporated into SnO2 nanostructures using chemical and impregnation methods by using urea and ammonia as precipitation agents. The synthesized samples were characterized using X-ray diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM) and High resolution transmission electron microscopy (HR-TEM). The presence of dopants within the SnO2 nanostructures was evidenced from HR-TEM. Doped powders utilizing chemical methods with urea as precipitation agent presented higher sensitivities compared to the remaining, which is due to the formation of uniform and homogeneous particles resulted from the temperature assisted synthesis. The particle sizes of doped SnO2 nanostructures were in the range of 40-100 nm. An enhanced sensitivity around 1783 was achieved with Cu doped SnO2 when compared with two other dopants i.e., Pt (1200) and Pd: SnO2(502). The high sensitivity of Cu: SnO2 is due to formation of CuO and its excellent association and dissociation in the presence of CO with adsorbed atmospheric oxygen at sensor operation temperatures resulted in high conductance. Cu: SnO2 may be an alternative and cost effective sensor for industrial applications.
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Materials Science, Polymers & Plastics; PLA; fused deposition modeling (FDM); surface characterization; vibrational spectroscopy; laser confocal microscopy; X-ray photoelectron spectroscopy
Online: 3 April 2017 (17:34:40 CEST)
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Polylactic Acid (PLA) is an organic polymer commonly used in fused deposition (FDM) printing and biomedical scaffolding that is biocompatible and immunologically inert. However, variations in source material quality and chemistry make it necessary to characterize the filament and determine potential changes in chemistry occurring as a result of the FDM process. We used several spectroscopic techniques, including laser confocal microscopy, Fourier-Transform Infrared (FTIR) spectroscopy and photoacousitc FTIR spectroscopy, Raman spectroscopy, and X-ray photoelectron Spectroscopy (XPS) in order to characterize both the bulk and surface chemistry of the source material and printed samples. Scanning Electron Microscopy (SEM) and Differential Scanning Calorimetry (DSC) were used to characterize morphology, crystallinity, and the glass transition temperature following printing. Analysis revealed calcium carbonate-based additives which were reacted with organic ligands and potentially trace metal impurities, both before and following printing. These additives became concentrated in voids in the printed structure. This finding is important for biomedical applications as carbonate will impact subsequent cell growth on printed tissue scaffolds. Results of chemical analysis also provided evidence of the hygroscopic nature of the source material and oxidation of the printed surface, and SEM imaging revealed micro and sub-micron scale roughness that will also impact potential applications.
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Materials Science, Biomaterials; Soy protein isolate; Microcrystalline cellulose; Metal nanoclusters; Nanocomposite film; Tensile strength
Online: 3 April 2017 (16:42:12 CEST)
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Soy protein isolate (SPI) based materials are abundant, biocompatible, renewable, and biodegradable. In order to improve the tensile strength (TS) of SPI films, we prepared a novel composite film modified with microcrystalline cellulose (MCC) and metal nanoclusters (NCs) in this research. The effects of the modification of MCC on the properties of SPI-Cu NCs and Zn NCs films were investigated. Attenuated total reflectance-Fourier transformed infrared spectroscopy analyses and X-ray diffraction patterns characterized the strong interactions and reduction of the crystalline structure of the composite films. Scanning electron microscope showed the enhanced cross-linked and entangled structure of modified films. Compared with untreated SPI film, the tensile strength of the SPI-MCC-Cu and SPI-MCC-Zn films increased from 2.91 MPa to 13.95 and 6.52 MPa, respectively. Moreover, the results also indicated their favorable water resistance with higher water contact angle. Meanwhile, the composite films exhibited increased initial degradation temperatures, demonstrating their higher thermostability. The results suggested that MCC could effectively improve the performance of SPI-NCs films, which would provide a novel preparation method for environmentally friendly SPI-based films in the applications of packaging materials.
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Materials Science, Metallurgy; Iron Aluminum Alloys; Cold/ Hot PM; Compressibility Factor; Wear Resistance.
Online: 3 April 2017 (16:23:00 CEST)
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Iron powders having average particle sizes of ~40µm are mechanically mixed thoroughly with aluminum powders ranging from 1 to 10 in wt.% with an average particle size of ~10µm. Two different powder metallurgical techniques cold and hot pressing are used to study the effect of the additive element powder on the mechanical properties, wear properties and the microstructure of the iron based alloys. The hot pressing technique was performed at a temperature up to 500°C at 445.6 MPa. The cold pressing technique was performed at 909 MPa in room temperature. By increasing the Al content to 10 wt. % in the base Fe-based matrix, the hardness was decreased from 780 to 690 MPa and the radial strength was decreased from 380 to 202 MPa with reductions of 11.5% and 40%, respectively. Improvement of the wear resistance with the increase addition of the Al powder to the Fe matrix up to 5 times was achieved compared to the alloy without Al addition for different wear parameters namely; wear time and sliding speed.
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Materials Science, Other; light aircraft; crashworthiness; topology optimization; composites materials; finite element analysis
Online: 31 March 2017 (11:13:27 CEST)
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Due to the demands of personal travels and entertainments, light airplanes and small business aircrafts are developing rapidly. Light airplane structure is simple; however, it lacks crashworthiness design, especially the considerations on the impact of energy absorption. Therefore, in an event of accident, significant damage to passengers will be usually incurred. Airplanes made of composite materials structurally have high specific strength and good aerodynamic configuration. These materials have become the primary choice for new airplane development. This study mainly explores the topology optimization analysis of the light aircraft’s cockpit made of carbon fiber reinforced composites. This paper compares the compression amounts in the original models of composite material and aluminum alloy fuselages with the models after optimization during the crash-landing, in order to investigate the safety of fuselages made of different materials after structural optimization under the dynamic crashing. This study found that the energy absorbed by the aluminum alloy fuselage during crash-landing is still higher than that by the carbon fiber reinforced composites fuselage. On the other hand, the aluminum alloy fuselage after topology optimization could have an energy absorption capability enhanced by 40%, as compared to the that of the original model of aluminum alloy fuselage.
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Materials Science, General Materials Science; copper resources; demand forecasting; system dynamics model; sustainability development
Online: 31 March 2017 (10:50:56 CEST)
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Copper demand for a country's copper industry has a greater pull effect. China's copper consumption in 2015 has accounted for 50% of the world. The scientific forecast of China's copper demands trend is also an important basis for analyzing its future environmental impact. This paper assumes that China's economy will be developing high, medium and low scenarios, and forecasts economic and social indicators such as total GDP, population and per capita GDP in China from 2016 to 2030. Then, predicted the demand of copper resources in China from 2016 to 2030 by the combination of system dynamics model, vector autoregressive moving average model and inverted U-type empirical model. The results show that: (1) in 2020, 2025 and 2030, China's refined copper demand will be 13 Mt, 15 Mt and 15.5 Mt. (2) China's copper demand growth slowed down significantly from 2016-2030. (3) 2025-2030, China's copper resource demand is stable, into the platform of demand growth, the highest peak value in 2027 will be 15.5 Mt. (4) 2030 years later, China's copper resource demand will enter a slow decline.
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Materials Science, Other; Ti-V-Cr-Fe alloy; hydrogen storage characteristics; metal corrosion; heat treatment; crystal structure
Online: 31 March 2017 (09:19:32 CEST)
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In this work, we investigated the effects of heat treatment on the microstructure, hydrogen storage characteristics and corrosion rate of a Ti34V40Cr24Fe2 alloy. The arc melted alloy was divided into three samples, two of which were separately quartz-sealed under vacuum and heated to 1000 °C for 1 h; one of these samples was quenched and the other furnace cooled to ambient temperature. The crystal structures of the samples were studied via X-ray diffractometry and scanning electron microscopy. Absorption/desorption characteristics were investigated using a Sievert apparatus. Potentiostat corrosion tests on the alloys were performed using an AutoLab® corrosion test apparatus and electrochemical cell. All samples exhibited a mixture of body-center-cubic (BCC) and Laves phase structures. The corrosion rate, maximum absorption, and useful capacities increased after both heat treatments. The annealed sample had the highest absorption and reversible capacity. The plateau pressure of the as-cast alloy increased after quenching. The corrosion rate increased from 0.0004 mm/y in as-cast sample to 0.0009 mm/y after annealing and 0.0017 mm/y after quenching, due to a decrease in the Cr-content of the C14 phase.
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Materials Science, Biomaterials; hydroxyapatite; xenografts; physicochemical-characterization; tissue reaction
Online: 31 March 2017 (08:35:07 CEST)
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Detailed information about graft material characteristic is crucial to evaluate their clinical outcomes. The present study evaluates the physicochemical characteristics of two xenografts manufactured on an industrial scale deproteinized at different temperatures (non-sintered and sintered) in accordance with a protocol previously used in sinus lift procedures. It compares how the physico-chemical properties influence the material performance in vivo with a histomorphometric study in retrieved bone biopsies following maxillary sinus augmentation, in 10 clinical cases. X-ray diffraction analysis revealed typical structure of hydroxyapatite for both materials. Both xenografts are porous and exhibit intraparticle pores. Strong differences were observed in terms of porosity, cristallinity, and calcium/phosphate. Histomorphometric measurements on the bone biopsies showed statistically significant differences. The physicochemical assessment of both xenografts in accordance with the protocol developed at industrial scale confirmed that these products present excelent biocompatibilitity, with characteristics similar to natural bone. The sintered HAs xenograft exhibit higher osteoconductivity although were not complete resorbable (30.80±0.88% residual material). On the other hand, the non-sintered HAs xerograft induced about 25.92±1.61% of new bone and almost complete degradation after 6 months implantation. Differences in physico-chemical characteristics found between the two HAs xenograft determine different behavior of this material.
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Materials Science, Biomaterials; hydroxyapatite; xenografts; scanning electron microscopy; degradation; resorption; Ca/P ratio; bone response; biocompatibility
Online: 28 March 2017 (17:09:44 CEST)
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Some studies have demonstrated that in vivo degradation processes are influenced by the material’s physico-chemical properties. The present study compares two hydroxyapatites manufactured on an industrial scale, deproteinized at low and high temperatures, and how physico-chemical properties can influence the mineral degradation process of material performance in bone biopsies retrieved 6 months after maxillary sinus augmentation. Residual biomaterial particles were examined by field scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) to determine the composition and degree of degradation of the bone graft substitute material. According to the EDX analysis, the Ca/P ratio significantly lowered in the residual biomaterial (1.08±0.32) compared to the initial composition (2.22±0.08) for the low-temperature sintered group, which also presented high porosity, low crystallinity, low density, a large surface area, and poor stability and a high resorption rate compared to the high-temperature sintered material. This demonstrates that variations in the physico-chemical properties of bone substitute material clearly influence the degradation process. Further studies are needed to determine whether the resorption of deproteinized bone particles proceeds slowly enough to allow sufficient time for bone maturation to occur.
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Materials Science, Biomaterials; siRNA delivery; aptamer AS1411; nucleolin targeting; gene therapy; RNA interference
Online: 27 March 2017 (17:05:36 CEST)
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RNA interference (RNAi) has potential advantages over other gene therapy approaches due to its high specificity and the ability to inhibit target gene expression. Thus, developing a stable, safe, effective siRNA delivery system is necessary to achieve targeted therapy. Here, we developed such a system by conjugating gelatin-based nanoparticles with the nucleolin-targeted AS1411 aptamer and siRNA sequence together (Apt-GS/siRNA NPs) via a disulphide linker. These Apt-GS/siRNA NPs demonstrated favourable release of siRNA under reducing conditions owing to disulphide cleavage. Furthermore, the Apt-GS/siRNA NPs could selectively deliver siRNA to A549 cells overexpressing nucleolin via a nucleolin-mediated transmembrane process, subsequently resulting in efficient RNAi. These results indicated that the Apt-GS/siRNA NPs could facilitate nucleolin-targeted siRNA delivery and gene silencing in tumours.
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Materials Science, General Materials Science; mesoporous TiO2; reduced graphene oxide; Ag nanoparticles; photocatalytic activity; visible light irradiation
Online: 27 March 2017 (12:01:25 CEST)
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Mesoporous TiO2/reduced graphene oxide/Ag (TiO2/RGO/Ag) ternary nanocomposite with effective electrons transfer pathway is obtained by an electrostatic self-assembly method and photo-assisted treatment. Compared with bare mesoporous TiO2 (MT) and mesoporous TiO2/RGO (MTG), the ternary mesoporous TiO2/RGO/Ag (MTGA) nanocomposite exhibited superior photocatalytic performance for the degradation of MB under visible light, and the degradation rate reached 0.017 min-1, which was 3.4 times higher than that of MTG. It is proposed that Ag nanoparticles can form the local surface plasmon resonance (LSPR) to absorb the visible light and distract the electrons into MT, and RGO can accept the electrons from MT to accelerate the separation efficiency of carriers. The establishment of MTGA ternary nanocomposite make the three components act synergistic effect to enhance the photocatalytic performance.
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Materials Science, Metallurgy; medium-carbon steel; fatigue life estimation; surface roughness
Online: 24 March 2017 (10:50:11 CET)
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Medium-carbon steel is commonly used for the rail, wire ropes, tire cord, cold heading, forging steels, cold finished steel bars, machinable steel and so on. Its fatigue behavior analysis and fatigue life estimation play an important role in the machinery industry. In this paper, the estimation of fatigue life of medium-carbon steel with different surface roughness using established S-N and P-S-N curves is presented. To estimate the fatigue life, the effect of the average surface roughness on the fatigue life of medium-carbon steel has been investigated using 75 fatigue tests in three groups with average surface roughness (Ra): 0.4μm, 0.8μm, and 1.6μm respectively. S-N curves and P-S-N curves have been established based on the fatigue tests. The fatigue life of medium-carbon steel is then estimated based on Tanaka-Mura crack initiation life model, the crack propagation life model using Paris law, and material constants of the S-N curves. 6 more fatigue tests have been conducted to validate the presented fatigue life estimation formulation. The experimental results have shown that the presented model could estimate well the mean fatigue life of medium-carbon steel with different surface roughness
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Materials Science, Metallurgy; Al-Zn-Cr Alloys; powder metallurgy; strengthening; extrusion; dry sliding wear
Online: 21 March 2017 (04:26:13 CET)
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Aluminum base alloys containing chromium (Cr) and zinc (Zn) were produced using extrusion and heat treated powder metallurgy. Cr addition ranged between 5 to 10 wt. % while Zn was added in an amount between 0 to 20 wt. %. Heat treatment processes were performed during powder metallurgy process at different temperatures followed by water quenching. Similar alloys were extruded, with an extrusion ratio of 4.6 to get proper densification. Optical microscopy was used for microstructure investigations of the produced alloys. The element distribution microstructure study was carried out using the Energy Dispersive X-ray analysis method. Hardness and tensile properties of the investigated alloys have been examined. Wear resistance tests were carried out and the results were compared with these of the Al-based bulk alloys. Results showed that the aluminum base alloys containing 10wt. % Chromium and heat treated at 500°C for one hour followed by water quenching exhibited the highest wear resistance and better mechanical properties.
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Materials Science, Polymers & Plastics; waste cooking oil; phthalic anhydride; copolymerization; microwaves
Online: 17 March 2017 (07:36:52 CET)
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Solvent free copolymerization of epoxides derived from fatty acid esters of waste cooking oil with phthalic anhydride using (salen)CrIII Cl as catalyst and n-Bu4NCl/DMAP as co-catalyst was carried out for the first time under microwave irradiation, where reaction time was reduced from number of hours to minutes. The polyesters were obtained with molecular weight (Mw = 3084-6740 g/mol) and dispersity values (D = 1.18-1.92), when (salen)CrIII Cl/n-Bu4NCl was used as catalysts. While in case of DMAP as a co-catalyst, polyesters with improved molecular weight (Mw = 5537-6925 g/mol) and narrow dispersity values (D = 1.07-1.28) were obtained even at reduced concentrations of (salen)CrIII Cl and DMAP. The obtained products were characterized and evaluated by attenuated total reflection-fourier transform infrared spectroscopy (ATR-FTIR), proton nuclear magnetic resonance (1H-NMR) spectroscopy, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) Techniques.
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Materials Science, Metallurgy; 5754 Aluminum alloy; Two-pass hot compression; Dynamic softening; Metadynamic recrystallization
Online: 16 March 2017 (18:28:52 CET)
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Isothermal interrupted hot compression tests of 5754 aluminum were conducted on Gleeble-3500 thermo-mechanical simulator at temperature 350 °C and 450 °C, strain rate 0.1 s-1 and 1s−1. These tests simulated flat rolling to investigate how softening behaviors respond to controlled parameters, such as deformation temperature, strain rate and delay times. This data allowed the parameters for the hot rolling process to be optimized. The delay times during interrupted compression vary between 5s and 60s. The dynamic softening at each pass and metadynamic recrystallization at the intervals of deformation passes were analyzed in detail. 0.2% offset yield strength is applied to calculate the softening fraction undergoing metadynamic recrystallization. A kinetic model was developed to describe metadynamic recrystallization behaviors of the hot deformed 5754 aluminum alloy. Furthermore, the time constant for 50% recrystallization was expressed as functions related to the temperature and the strain rate. The experimental and calculated results were found to be in close agreement, which verified the developed model.
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Materials Science, Biomaterials; stone matrix asphalt; volume parameters; Marshall Stability; flocculent lignin fiber; polyester fiber; mineral fiber; fiber content
Online: 15 March 2017 (08:25:11 CET)
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Lignin fibers typically influence the mixture performance of stone matrix asphalt (SMA), such as strength, stability, durability, noise level, rutting resistance, fatigue life, and water sensitivity. However, limited studies were conducted to analyze the influence of fibers on the percent voids in mineral aggregate in bituminous mixture (VMA) during the mixture design. This study analyzed the effect of different fibers and fiber contents on the VMA in SMA mixture design. A surface-dry condition method test and Marshall Stability test were applied on the SMA mixture with four different fibers (i.e., flocculent lignin fiber, mineral fiber, polyester fiber, blended fiber). The test results indicated that the bulk specific gravity of SMA mixtures and asphalt saturation decreased with the increasing fiber content, whilst the percent air voids in bituminous mixtures (VV), Marshall Stability and VMA increased. Mineral fiber had the most obvious impact on the bulk specific gravity of bituminous mixtures, while flocculent lignin fiber had a minimal impact. The mixture with mineral fiber and polyester fiber had significant effects on the volumetric properties, and, consequently, exhibited better VMA over the conventional SMA mixture with lignin fiber. Modified fiber content range was also provided, which will widen the utilization of mineral fiber and polyester fiber in the applications of SMA mixtures. The mixture evaluation suggested no statistically significant difference between lignin fiber and polyester fiber on the stability. The mineral fiber required a much larger fiber content to improve the mixture performance than other fibers. Overall, the results can be a reference to guide SMA mixture design.
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Materials Science, Biomaterials; TCP-C2S, Nurse ´A ceramic, Biomaterials, adult human mesenchymal stem cells, Solid State Reaction, Biomedical applications.
Online: 14 March 2017 (13:43:13 CET)
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The purpose of this study was to evaluate the bioactivity and cell response of a well-characterized Nurse´s A-phase (7CaO•P2O5•2SiO2) ceramic and his effect compared to a control (tissue culture polystyrene-TCPS) on the adhesion, viability, proliferation and osteogenic differentiation of ahMSCs in vitro. Cell proliferation (Alamar Blue Assay), Alizarin Red-S (AR-s) staining, alkaline phosphatase (ALP) activity, osteocalcin (OCN) and collagen I (Col I) were evaluated. Also, field emission scanning electron microscopy (FESEM) images were acquired in order to visualise the cells and the topography of the material. The proliferation of cells growing in a direct contact with the material was slower at early stages of the study because of the new environmental conditions. However, the entire surface was colonized after 28 days of culture in growth medium (GM). Osteoblastic differentiation markers were significantly enhanced in cells growing on Nurse´s A phase ceramic and cultured with osteogenic medium (OM), probably due to the role of silica to stimulate the differentiation of ahMSCs. Moreover, calcium nodules were formed under the influence of ceramic material. Therefore, it is predicted that Nurse´s A-phase ceramic would present high biocompatibility and osteoinductive properties being a good candidate to be used as a biomaterial for bone tissue engineering.
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Materials Science, Nanotechnology; anodic aluminum oxide (AAO); subwavelength structure (SWS); antireflection; poly-methyl methacrylate (PMMA); dye-sensitized solar cell (DSSC); conversion efficiency
Online: 14 March 2017 (08:46:39 CET)
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In this study, a high energy conversion efficient dye-sensitized solar cells (DSSC) was successfully fabricated by attaching a double anti-reflection (AR) layer which is composed of a subwavelength moth-eye structured polymethyl methacrylate (PMMA) film and a polydimethylsiloxane (PDMS) film. The efficiency is up to 6.79%. The moth-eye structured PMMA film was fabricated by using anodic aluminum oxide (AAO) template which is simple, low-cost and scalable. The nano-pattern of AAO template has been precisely reproduced onto PMMA film. The photoanode is composed of Titanium dioxide (TiO2) nanoparticles (NPs) with diameter of 25 nm deposited on the fluorine-doped tin oxide (FTO) glass substrate and the sensitizer N3. The double AR layer can effectively improve the short-circuit current density (JSC) and conversion efficiency from 14.77 to 15.79 mA/cm2 and from 6.26% to 6.79%, respectively.
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Materials Science, Biomaterials; micro-arc oxidation; antibacterial ability; Ag; Cu; Zn
Online: 14 March 2017 (07:49:40 CET)
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Ti and its alloys are the most commonly used materials for biomedical applications. However, bacterial infection after implant placement is still one of the significant rising complications. Therefore, the application of the antimicrobial agents into implant surfaces to prevent implant-associated infection has attracted lots of attention. Scientific papers have shown that inorganic antibacterial metal element (e.g. Ag, Cu, Zn) can be introduced to implant surfaces with the addition of metal nanoparticles or metallic compounds into electrolyte via micro-arc oxidation (MAO) technology. In this review, the effects of the composition and concentration of electrolyte and process parameters (e.g. voltage, current density, oxidation time) on morphological characteristics (e.g. surface morphology, bonding strength), antibacterial ability and biocompatibility of MAO antimicrobial coating were discussed in detail. Anti-infection and osseo-integration can be simultaneously accomplished with the selection of the proper antibacterial elements and operating parameters. Besides, MAO assisted by magnetron sputtering (MS) to endow Ti-based implant materials with superior antibacterial ability and biocompatibility was also discussed. Finally, the development trend of MAO technology in the future was forecasted.
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Materials Science, Biomaterials; luffa sponge fiber bundles; mechanical properties; anatomical characteristic; moisture regain; thermal performance
Online: 6 March 2017 (04:32:21 CET)
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The advancement in science and technology has led to luffa sponge (LS) being widely used as a natural material in industrial application as its polyporous structure and light texture. In order to enhance the utility of LS fibers as the reinforcement of lightweight composite materials, this study investigate its water absorption, mechanical properties, anatomical characteristic and thermal performance. Hence, moisture regain, tensile properties of LS fiber bundles were measured in accordance with standards and the structural characteristics were investigated via microscopic observation. Scanning electron microscopy (SEM) was used to observe the surface morphology and fracture surface of fiber bundles. Test results shows that the special structure where the phloem tissues degenerate to cavities had a significant influence on the mechanical properties of LS fiber bundles. Additionally, the transverse sectional area occupied by fibers in a fiber bundle (SF), wall thickness and ratio of wall to lumen of fiber cell, and crystallinity of cellulose had an impact on the mechanical properties of LS fiber bundles. Furthermore, the fiber bundles density of LS varies range of 385.46-468.70 kg/m3, much less than that of jute (1360.40 kg/m3) and Arenga engleri (950.20 kg/m3) while LS fiber bundles has superior specific modulus.
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Materials Science, General Materials Science; perfect metamaterial absorber; terahertz; six-band; cave-cross patch resonator
Online: 3 March 2017 (08:48:31 CET)
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A simple design of an ultrathin six-band polarization-insensitive terahertz perfect metamaterial absorber (PMMA) composed of a metal cross-cave-patch resonator (CCPR) placed over a ground plane was proposed and investigated numerically. The numerical simulation results demonstrate that the average absorption peaks are up to 95% at six resonance frequencies with high quality-factors (>65). In addition, the absorption properties can be kept stability for both normal incident transverse magnetic (TM) and transverse electric (TE) waves. The physical mechanism behind the observed high level absorption is illustrated by the electric and power loss density distributions. The different absorption mainly originates from the higher order multipolar and multipolar plasmon resonance of the structure, which are sharp different to the most previous studies of the PMMAs. Furthermore, the resonance absorption of the PMMA can be tunable by varying the geometric parameters of the unit cell.
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Materials Science, Biomaterials; anodic oxidation; titanium dioxide; electrolyte concentration; sulfuric acid
Online: 2 March 2017 (18:25:55 CET)
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To obtain smooth coatings of TiO2 for building a new design of Ti-6Al-4V heart valve, the anodic oxidation technique in pre-spark conditions was evaluated. TiO2 coating is necessary for its recognize biocompatibility and corrosion resistance. A required feature on surfaces in contact with blood is a low level of roughness (Ra ≤ 50 nm) that not favor the formation of blood clots. The present paper compares the coatings obtained by anodic oxidation of the Ti-6Al-4V alloy using H2SO4 at different concentrations (0.1 M to 4 M) as electrolyte and applying different voltages (from 20 V to 70 V). Color and morphological analysis of coatings are performed using optical and scanning microscopy. The crystalline phases were analyzed by glancing X-ray diffraction. By varying the applied voltage different interference colors coatings were obtained. The differences in morphologies of the coatings, due to the change in concentration, are more evident at high voltages limiting the oxidation conditions for the desired application. Anatase phase was detected from 70 V for 1 M H2SO4. An increase in the concentration of H2SO4 decreases the voltage at which the transformation of amorphous to crystalline coatings occurs, i.e. with 4 M H2SO4 the anatase phase appears at 60 V.
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Materials Science, Nanotechnology; green synthesis; silver nanoparticles; trimethylchitosan nitrate; catalytic activity; antibacterial activity; multidrug-resistant Acinetobacter baumannii
Online: 2 March 2017 (08:49:35 CET)
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We report a facile route for the green synthesis of trimethylchitosan nitrate-capped silver nanoparticles (TMCN-AgNPs) with positive surface charge. In this synthesis, silver nitrate, glucose, and trimethyl chitosan nitrate (TMCN) were used as silver precursor, reducing agent, and stabilizer, respectively. The reaction was carried out in a stirred basic aqueous medium at room temperature without the use of energy-consuming or expensive equipment. We investigated the effects of the concentrations of NaOH, glucose, and TMCN on the particle size, zeta potential, and formation yield. The AgNPs were characterized by UV-visible spectroscopy, photon correlation spectroscopy, laser Doppler anemometry, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalytic activity of the TMCN-AgNPs was studied by the reduction of 4-nitrophenol using NaBH4 as a reducing agent. We evaluated the antibacterial effects of the TMCN-AgNPs on Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus using the broth microdilution method. The results showed that both gram-positive and gram-negative bacteria were killed by the TMCN-AgNPs at very low concentration (< 6.13 μg/mL). Moreover, the TMCN-AgNPs also showed high antibacterial activity against clinically isolated multidrug-resistant A. baumannii strains, and the minimum inhibitory concentration (MIC) was ≤ 12.25 μg/mL.
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Materials Science, General Materials Science; laser wavelength; polysilicon; laser damage; thermal shock
Online: 27 February 2017 (06:56:01 CET)
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Based on PVDF (piezoelectric sensing techniques), this paper attempts to study the propagation law of shock waves in brittle materials during the process of three-wavelength laser irradiation of polysilicon, and discusses the formation mechanism of thermal shock failure. The experimental results show that the vapor pressure effect and the plasma pressure effect in the process of pulsed laser irradiation lead to the splashing of high temperature and high density melt. With the decrease of the laser wavelength, the laser breakdown threshold decreases and the shock wave is weakened. Because of pressure effect of the laser shock, the brittle fracture zone is at the edge of the irradiated area. The surface tension gradient and surface shear wave caused by the surface wave are the result of coherent coupling between optical and thermodynamics. The average propagation velocity of laser shock wave in polysilicon is 8.47×103m/s, and the experiment has reached the conclusion that the laser shock wave pressure peak exponentially distributes attenuation in the polysilicon.
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Materials Science, Metallurgy; fracture toughness, scratch test, residual stress, tool steel, cryogenic treatment
Online: 24 February 2017 (14:46:47 CET)
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The scratch test consists in pushing a tool across the surface of a material at a given penetration depth or applied load. It has several applications in Science and Engineering including strength testing, damage and quality control of thin films and coatings. Despite numerous attempts in scientific literature, the application of scratch test to characterizations of fracture properties remains a heavily controversial topic. Therefore, this investigation arises as an experimental study in order to assess the fracture toughness using scratch test. A study on the effect of cryogenic treatment, performed after tempering, on fracture toughness, via scratch test experiments, of different tool steels has been made. A laboratory investigation on AISI D2, AISI M2 and X105CrCoMo18 steel confirms the possibility of increasing the fracture toughness by carrying out the cryogenic treatment after the usual heat treatment
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Materials Science, Other; Diatomite; ionic exchange; metals removal; heavy metals
Online: 23 February 2017 (10:37:50 CET)
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This work shows the physicochemical and mineralogical characterization of diatomites form the Hidalgo and Jalisco States, Mexico. In the case of the mineral from Hidalgo State, this has the following chemical composition; 70.0 % wt. SiO2, 11.63 wt. % Al2O3, 1.95 wt. % FeO, 1.79 wt. % MgO, 2.41 wt. % K2O, 0.85 wt. % CaO and 6.10 wt. % Na2O. On the other hand, the mineral from Jalisco has the following chemical composition; 93.58 wt. % SiO2, 3.03 wt. % Al2O3, 1.81 wt. % FeO, 0.40 wt. % MgO, 0.92 wt. % K2O, 0.11 wt. % CaO and 0.24 wt. % Na2O. For recovery of metals, both minerals got arsenic, silver, lead and nickel recoveries upper to 95 % and lower to 10 % for chromium. According to efficiency of interchange, the mineral from Hidalgo is slightly higher in the case of arsenic, lead and silver; while for nickel and particularly chromium (VI) the efficiency is higher for the mineral from Jalisco.
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Materials Science, Surfaces, Coatings & Films; biodegradable; Carboxymethyl cellulose (CMC); edible films; mechanical properties; sago starch
Online: 20 February 2017 (06:43:55 CET)
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Using biodegradable films is increasingly growing since they contain natural materials. In this study, sago starch and carboxymethyl Cellulose (CMC) were used in film preparation. Sago starch films with 0, 5, 10, 15 and 20% CMC concentrations were prepared using solvent casting method. The mechanical properties were determined according to standards of American Society for Testing and Materials. In mechanical test of the combined films, increased CMC concentration significantly (P<0.05) increased tensile strength and Young Modulus from 21.04 to 27.74MPa and from 1372.83 to 1842.87kg/m2, respectively, and percent elongation showed significant (P<0.05) reduction from 17.69 to 15.39. Considering biodegradability of the edible films and improvement of their mechanical properties by CMC, they can be utilized in different industries, particularly in food industry, as an edible coating for packaging food and agricultural products. With regard to its properties such as cost saving, biodegradability and mechanical properties when percentage of CMC increased can found a position among food packaging materials.
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Materials Science, General Materials Science; high volume fly ash, high fluidity concrete, early strength, field application
Online: 13 February 2017 (11:44:54 CET)
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In the recent concrete industry, high fluidity concrete is being widely used for the pouring of dense reinforced concrete. Normally, in the case of high fluidity concrete, it includes high binder contents, so it is necessary to replace part of the cement through admixtures such as fly ash to procure economic feasibility and durability. This study shows the mechanical properties and field applicability of high fluidity concrete that using mass of fly ash as alternative materials of cement. The high fluidity concrete mixed with 50% fly ash was measured to manufacture concrete that applies low water/binder ratio to measure the mechanical characteristics as compressive strength and elastic modulus. Also, in order to evaluate the field applicability, high fluidity concrete containing high volume fly ash was evaluated that fluidity, compressive strength, heat of hydration and drying shrinkage of concrete.
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Materials Science, Metallurgy; Fe-Mn-Si alloy; isothermal holding time; powder sintering; density; weight loss; tensile properties
Online: 9 February 2017 (07:06:14 CET)
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This work investigated the isothermal holding time dependence of the densification, microstructure, weight loss and tensile properties of Fe-Mn-Si powder compacts. Elemental Fe, Mn and Si powder mixtures with a nominal composition of Fe-28Mn-3Si (in weight percent) were ball milled for 5h and subsequently pressed under a uniaxial pressure of 400 MPa. The compacted Fe-Mn-Si powder mixtures were sintered at 1200 ℃ for 0, 1, 2 and 3 h, respectively. In general, the density, weight loss and tensile properties increased with the increase of isothermal holding time. A significant increase in density, weight loss and tensile properties occurred in the compacts isothermally holding for 1 h, as compared to those with no isothermal holding. However, further extension of isothermal holding time (2 and 3 h) only played a limited role in promoting the density and tensile properties. The weight loss of the sintered compacts was mianly caused by the sublimation of Mn in Mn depletion region on the surface layer of the sintered Fe-Mn-Si compacts. The length of the Mn depletion region increased as isothermal holding time increased. A single α-Fe phase was detected on the surface of all the sintered compacts, and the locations beyond the Mn depletion region were comprised of a dual dominant γ-austenite and minor ε-martensite.
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Materials Science, Nanotechnology; nano-cube; heterostructures; bottom-up growth; electron microscopy; bandgap; Ag-WO3
Online: 4 February 2017 (09:23:00 CET)
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A new class of nano-cube core-shell heterostructures containing Ag coating on the top of WO3 was fabricated. Physical vapor deposition was used to produce WO3 based nano-heterostructures. All kind of wet toxic chemical process was avoided to make the process simple and contaminant free. Sputtering of WO3 and a subsequent thermal annealing process was done to create nano-cubes of WO3. After that, sputtering of Ag was performed to form the Ag-WO3 core-shell nano-heterostructures (CSNH). The CSNHs were characterized using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD) and UV-vis spectroscopy. The morphologies, elemental analysis, interfaces, crystallinity, phases, and chemical compositions were analyzed. The bottom-up growth of WO3 nanocubes was studied using different time periods at 900°C. Ag coating was also studied before and after annealing. Finally, an optical property (band gap) was also analyzed using Tauc plot derive from absorption spectra. The tailoring the band gap of WO3 from ~2.9eV to ~ 2.45 eV was observed while Ag-WO3 CSNH formed.
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Materials Science, Biomaterials; amorphous polyphosphate microparticles; retinyl acetate; enamel cracks/fissures; Streptococcus mutans; human mesenchymal stem cells; collagen type I; alkaline phosphatase
Online: 4 February 2017 (07:37:55 CET)
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Here we report the preparation and characterization of a novel biomimetic toothpaste containing morphogenetically active amorphous polyphosphate (polyP) microparticles enriched with retinyl acetate (“a-polyP/RA-MP”). The spherical microparticles (average size, 550±120 nm), prepared by co-precipitating sodium-polyP with calcium chloride and supplemented with retinyl acetate, were incorporated into a basis toothpaste at a final concentration of 1% or 10%. The paste containing “a-polyP/RA-MP” significantly increased the growth of human mesenchymal stem cells (MSC), compared to a commercial toothpaste which acts rather inhibitory and the paste without polyP and retinyl acetate. qRT-PCR experiments revealed that the retinoid causes an induction of the expression of the MSC marker genes for osteoblast differentiation encoding collagen type I and alkaline phosphatase. On the other hand, the polyP ingredient, supplied as Zn-polyP microparticles (“Zn-a-polyP-MP”) strongly inhibited the growth of the cariogenic bacterium Streptococcus mutans. We demonstrate that the amorphous polyP-containing toothpaste, enriched with retinyl acetate, efficiently repairs both cracks/fissures and carious lesions in the tooth enamel, and reseals dentinal tubules, already after a 5 d treatment (brushing) of teeth twice daily for 5 min as examined by SEM and quantitative EDX analysis. The stability of the occlusion of dentin cracks even turned out to resist against short high power sonication treatment. Our results demonstrate that the novel toothpaste prepared here, containing amorphous polyP and retinyl acetate, is particularly suitable for prevention/repair of (cariogenic) damages of tooth enamel/dentin and for treatment of dental hypersensitivity.
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René De La Barré,
Roland Bartmann,
Silvio Jurk,
Mathias Kuhlmey,
Bernd Duckstein,
Arno Seeboth,
Detlef Lötzsch,
Christian Rabe,
Peter Frach,
Hagen Bartsch,
Matthias Gittner,
Stefan Bruns,
Gerhard Schottner,
Johanna Fischer
Materials Science, Surfaces, Coatings & Films; fast switchable wavelength-selective elements, autostereoscopic image splitter, color filter barrier array, Fabry-Pérot color filter, on-off filter mode
Online: 1 February 2017 (16:52:44 CET)
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A time-sequential working, spatially multiplexed autostereoscopic 3D display design consisting of a fast switchable RGB-color filter array is presented. The wavelength-selective filter barrier emits the light from a display over a larger active area than common autostereoscopic barrier displays. An optical modelling of wavelength-selective barriers has been used for instance to calculate the light ray distribution properties of that arrangement. To find well working display designs, automated searches by simulation and computational evaluation has been proceeded. Wavelength-selective filter barrier arrangements exhibit characteristics different from common barrier displays with similar barrier pitch and ascent. In particular, these constructions show strong angular luminance dependency under barrier inclination specified by correspondent slant angle. In time-sequential implementation it is important to avoid that quick eye or eyelid movement lead to visible color artifacts. In the millisecond regime tunable liquid crystal Fabry-Pérot color filters for the colors red, green and blue are presented. They consist of a sub-micrometer thick nematic layer sandwiched between dielectric mirrors and ITO-electrodes. These cells shall switch narrow-banding light of red, green or blue. An array for a glasses-free 3D display has to be equipped with several thousand switchable filter elements having different color apertures. The newly introduced design is usable as a multi user display as well as a single user system with user adaptive control.
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Materials Science, Metallurgy; wüstite; magnetite; eutectoid transformation; oxide scale; hot strip mill
Online: 29 January 2017 (10:47:49 CET)
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It is important to realize the transformation behavior of wüstite because it greatly affects the final structure of the oxide layer and the surface quality of the steel products. In the present study, the transformation behaviors of the wüstite layer are examined under nearly-oxygen-free conditions, to simulate the cooling processes after the hot rolled strip is coiled. As the single phase wüstite was prepared at 950˚C, the 460˚C transformed oxide layer was composed of a mixture of iron and magnetite formed through eutectoid reactions. For the 750˚C-fabricated wüstite, only magnetite was observed after transformation, without iron precipitates and residual wüstite. It is speculated that the unusual transformation behavior of the low-temperature-made wüstite results from the pseudo-structural intermediate phase transformation between wüstite and magnetite. This pseudo-structure is a pre-transformed wüstite and of various concentration of ferrous ion, which is determined by the fabrication conditions. During the hot strip mill process, the so-called wet scale, wüstite, is produced continuously from finish mill to laminar flow sections and ended at 570˚C. Consequently, the final eutectoid transformation below 570˚C is dominantly controlled by the surface temperature ranged from 750˚C to 950˚C for low carbon steel.
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Materials Science, Polymers & Plastics; PEEK; blends; thermal stability; tribological properties; mechanical properties
Online: 25 January 2017 (10:03:49 CET)
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In this study, 10%PTFE/PEEK blend were modified by potassium titanate whisker (PTW) and chopped glass fiber (GF), respectively. The blends were prepared by three-screw extruder. Through the investigation of thermal stability, tribological properties, mechanical properties and rheological behavior, the effects of reinforcing agents were determined. The results illustrated that the mechanical properties of 10%PTFE/PEEK blend can be dramatically improved by adding reinforcing agent of PTW or GF, and the reinforcing effect of GF was especially obvious. As for tribological properties, 1% addition was the best proportion. The friction coefficient and wear rate of the blend with 1% PTW were 0.283 and 4.97 × 10-6 mm3/N · m, which decreased by 7.2% and 21% compared with those of the blend without reinforcing agent.
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Materials Science, Nanotechnology; MoS2; composite; anode; low cost; Li-ion battery
Online: 19 January 2017 (11:08:29 CET)
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A low-cost bio-mass-derived carbon substrate has been employed to synthesize MoS2@carbon composites through a hydrothermal method. Carbon fibers derived from natural cotton provide a three-dimensional and open framework for the uniform growth of MoS2 nanosheets, thus constructing hierarchically coaxial architecture. The unique structure could synergistically benefit fast Li-ion and electron transport from the conductive carbon scaffold and porous MoS2 nanostructures. As a result, the MoS2@carbon composites, when served as anodes for Li-ion batteries, exhibit a high reversible specific capacity of 820 mAh g-1, high-rate capability (457 mAh g-1 at 2 A g-1), and excellent cycling stability. The superior electrochemical performance makes the MoS2@carbon composites to be low-cost and promising anode materials for Li-ion batteries.
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Materials Science, Nanotechnology; vanadium pentoxide; lithium-ion batteries; hollow spheres; cathode
Online: 18 January 2017 (09:48:30 CET)
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Three-dimensional V2O5 hollow structures have been prepared through a simple synthesis strategy combining solvothermal treatment and a subsequent thermal annealing. The V2O5 materials are composed of microspheres 2–3 μm in diameter and with a distinct hollow interior. The as-synthesized V2O5 hollow microspheres, when evaluated as a cathode material for lithium-ion batteries, can deliver a specific capacity as high as 273 mAh·g−1 at 0.2 C. Benefiting from the hollow structures that afford fast electrolyte transport and volume accommodation, the V2O5 cathode also exhibits a superior rate capability and excellent cycling stability. The good Li-ion storage performance demonstrates the great potential of this unique V2O5 hollow material as a high-performance cathode for lithium-ion batteries.
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Materials Science, Other; secondary phases; CZTS film; XPS
Online: 12 January 2017 (11:04:27 CET)
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A Cu2ZnSnS4 (CZTS) film with a thickness of approximately 1.5 μm was fabricated on a Mo-coated glass substrate by annealing a CZTS precursor fabricated from nanoparticle ink. The chemical states of the elements in the CZTS thin film in the depth direction were studied to identify the presence of secondary phases, which are detrimental to the performance of solar cells containing CZTS. X-ray diffraction was unable to detect any secondary phases in CZTS because of their small relative amount. Instead, X-ray photoelectron spectroscopy (XPS), which is highly sensitive to chemical state, was conducted at different depths in the CZTS film to further check the presence of secondary phases. XPS analysis revealed peaks shift consistent with the presence of secondary phases. For the CZTS film annealed in a S atmosphere at 575 °C for 3 h, the film surface consisted of a secondary-phase layer composed of CuS, ZnS, and SnSx (x=1 or 2) originating from the decomposition of CZTS. At depths below 80 nm, the film was pure CZTS. Formation of MoS2 at the CZTS–Mo interface was confirmed by XPS analysis of Mo and S.
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Materials Science, General Materials Science; HfB4; structure prediction; superhard material; anisotropic properties
Online: 12 January 2017 (10:57:03 CET)
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By using the particle swarm optimization algorithm for crystal structure prediction, we reveal a newly orthorhombic Cmcm structure of HfB4, which is more energetically superior to the previously proposed YB4-, ReP4-, FeB4-, CrB4-, and MnB4-type structures in the considered pressure range. The phonon dispersion and elastic constants calculations confirm that the new phase is dynamically and mechanically stable. The calculated large shear modulus (240 GPa) and high hardness (45.7 GPa) imply that the predicted Cmcm-HfB4 is a potential superhard material. Meanwhile, the directional dependences of the Young's modulus, bulk modulus, and shear modulus for HfB4 are systematically investigated. Further analyses of the density of states and electronic localization function indicate that the strong B-B and B-Hf covalent bonds greatly contribute to its high hardness and stability.
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Materials Science, General Materials Science; spin crossover; density functional calculations; Hubbard model; solid state; Slichter-Drickamer model; Monte Carlo simulation; Ising model
Online: 11 January 2017 (09:17:46 CET)
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The total enthalpies of the 16 different spin configurations that can be realized in the unit cell of the archetype spin crossover complex [Fe(phen)2(NCS)2] (phen=1,2-phenanthroline) were calculated applying periodic density functional theory combined with the Hubbard model and the Grimme-D2 dispersion correction (DFT+U/D2). The obtained enthalpy differences between the individual spin configurations were used to determine spin couplings of an Ising-like model and subsequent Monte Carlo simulations for this model allowed to estimate the phenomenological interaction parameter Г of the Slichter-Drickamer model, which is commonly used to describe the cooperativity of the spin transition. The calculational procedure described here, which led to an estimate of about 3 kJ/mol−1 for Г, in good agreement with experiment, may be used to predict from first principles how modifications of spin crossover complexes can change the character of the spin transition from gradual to abrupt and vice versa.
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Materials Science, Polymers & Plastics; nanocomposites; halloysite nanotubes; multi-layer graphene; water absorption; mechanical properties
Online: 5 January 2017 (09:34:10 CET)
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The influence of short term water absorption on the mechanical properties of halloysite nanotubes-multi layer graphene reinforced polyester hybrid nanocomposites has been investigated. The addition of nano-fillers significantly increased the flexural strength; tensile strength and impact strength in dry and wet conditions. After short term water exposure; the maximum microhardness; tensile; flexural and impact toughness values were observed at 0.1 wt% MLG. The microhardness increased up to 50.3%; tensile strength increased up to 40% and flexural strength increased up to 44%. Compared to dry samples; the fracture toughness and surface roughness of all types of produced nanocomposites were increased that may be attributed to plasticization effect. Scanning electron microscopy revealed that the main failure mechanism is caused by the weakening of nano-filler-matrix interface induced by water absorption. It was further observed that synergistic effects were not effective at concentration of 0.1 wt% to produce considerable improvement in mechanical properties of produced hybrid nanocomposites.
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Materials Science, General Materials Science; high-entropy alloys; Al-Ni-Co-Fe-Cr alloys; microstructure; precipitation morphology; mechanical property
Online: 4 January 2017 (10:30:17 CET)
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The present work investigates primarily the morphology evolution of the body-centered-cubic (BCC)/B2 phases in AlxNiCoFeCr high-entropy alloys (HEAs) with increasing Al content, which has been neglected so far. There exist two types of microscopic morphologies of BCC and B2 phases in this HEA series: one is the weave-like morphology induced by the spinodal decomposition, and the other is the microstructure of a spherical disordered BCC precipitation on the ordered B2 matrix that appears in HEAs with a much higher Al content. The shape of coherent precipitates is found to be closely related to the lattice misfit between BCC and B2 phases, which is sensitive to Al. The mechanical properties, including the compressive yielding strength and microhardness of the AlxNiCoFeCr HEAs, are also discussed in light of the concept of the valence electron concentration (VEC).
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Materials Science, Surfaces, Coatings & Films; Superhydrophobic; Water-repellent; Chemical etching; Self-cleaning; Anti-fogging
Online: 2 January 2017 (17:27:05 CET)
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Development of the self-cleaning and anti-fogging superhydrophobic coating for aluminum surfaces which is durable in the aggressive conditions has raised tremendous interest in materials science. In this work, by employing chemical etching technique with mixture of hydrochloric and nitric acid, followed by passivation with lauric acid, superhydrophobic aluminum surface was synthesized. The surface morphology analysis reveals the presence of rough microstructures on coated aluminium surface. Superhydrophobicity with water contact angle of 170 ± 3.9° and sliding angle of 4 ± 0.5° is achieved. Surface bounces off the high speed water jet, indicating excellent water-repellent nature of coating. It is also continuously floated on water surface for several weeks, showing excellent buoyancy nature. Additionally, coating maintains its superhydrophobicity after undergoing 100 cycles of adhesive tape peeling test. Its superhydrophobic nature withstands 90° and 180° bending, and repeated folding and de-folding. Coating exhibits the excellent self-cleaning property. In low temperature condensation test, almost no accumulation of water drops on the surface, showing the excellent anti-fogging property of coating. This approach can be applied to any size and shape of aluminium surface and hence has great industrial applications.
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Materials Science, General Materials Science; crystal structure; Hume-Rothery phases; structure stability
Online: 2 January 2017 (10:42:19 CET)
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Crystal structures of simple metals and binary alloy phases based on the face-centered cubic (fcc) structure are analyzed within the model of Fermi sphere – Brillouin zone interactions to understand the stability of original cubic structure and derivative structures with distortions, superlattices and vacancies. Examination of the Brillouin-Jones configuration in relation to the nearly-free electron Fermi sphere for several representative phases reveals significance of the electron energy contribution to the phase stability. Representation of complex structures in the reciprocal space clarifies their relationship to the basic cubic cell.
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Xiaodong Wang,
Shengcheng Mao,
Jianfei Zhang,
Zhipeng Li,
Qingsong Deng,
Jin Ning,
Xudong Yang,
Li Wang,
Yuan Ji,
Xiaochen Li,
Yinong Liu,
Ze Zhang,
Xiaodong Han
Materials Science, Nanotechnology; piezoresistive sensor; electron microscope; in situ mechanical test
Online: 30 December 2016 (04:16:25 CET)
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In this work, we designed a MEMS device which allows simultaneous direct measurement of mechanical properties during deformation under external stress and characterization of the evolution of microstructure of nanomaterials within a transmission electron microscope. This MEMS device makes it easy to establish the correlation between microstructure and mechanical properties of nanomaterials. The device uses piezoresistive sensors to qualitatively measure the force and displacement of nanomaterials, e.g., in wire and thin plate forms. The device has a theoretical displacement resolution of 0.19 nm and a force resolution of 2.1 μN. The device has a theoretical displacement range limit of 2.74 μm and a load range limit of 27.75 mN.
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Materials Science, General Materials Science; MoS2; carbon nanofibers; electrospinning; anode material
Online: 28 December 2016 (10:49:33 CET)
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The one-dimensional MoS2/carbon nanofibers (1D MoS2/CNFs) are synthesized by electrospinning using exfoliated MoS2 nanosheets and polyacrylonitrile as raw materials. The exfoliated MoS2 nanosheets with size of about 150 nm are encapsulated in carbon nanofibers, and the free-standing MoS2/CNFs can be easily cut into flexible tablet and directly used as binder-free anode for lithium storage. The resultant 1D MoS2/CNFs exhibit a very high reversible capacity of 700 mAh g-1 at 100 mA g-1 after 50 cycles, high rate capacity (450 mAh g-1 at 1000 mA g-1 after 200 cycles) and good cycle stability.
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Materials Science, Surfaces, Coatings & Films; chemical phosphate coating; EIS; nano TiO2; TAFEL
Online: 23 December 2016 (10:23:24 CET)
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The present study aims at deposition of zinc phosphate coatings with the incorporation of nano Titanium dioxide particles by chemical phosphating method. Zinc phosphate coatings were developed on low carbon steel by using nano TiO2 in the standard phosphating bath. The Coated low carbon steel samples were assessed for corrosion studies using electrochemical impedance spectroscopy and potentiodynamic polarisation techniques in 3.5% NaCl solution. Chemical composition of the coatings was analysed by energy dispersive X-ray spectroscopy (EDX). Significant variations in the coating weight, porosity and corrosion resistance were observed with the addition of nano TiO2 in the phosphating bath. Corrosion rate of nano TiO2 incorporated chemical phosphate coated samples was found to be 3.5 mpy which was 4 times less than the bare uncoated low carbon steel (~14 mpy). Electrochemical impedance spectroscopy studies revels in the reduction of porosity in nano TiO2 phosphate coated samples. It was found that nano TiO2 particles in the phosphating solution yielded phosphate coatings of higher coating weight, greater surface coverage and enhanced corrosion resistance than the normal zinc phosphate coatings (developed using normal phosphating bath).
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Materials Science, General Materials Science; discrete element method; hypervelocity impact; debris cloud; fragmentation; space debris; multiscale modeling; computer simulation; high performance computing
Online: 23 December 2016 (10:21:21 CET)
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In this paper we introduce a computational model for the simulation of hypervelocity impact (HVI) phenomena which is based on the Discrete Element Method (DEM). Our paper constitutes the first application of DEM to the modeling and simulating of impact events for velocities beyond 5 kms−1. We present here the results of a systematic numerical study on HVI of solids. For modeling the solids, we use discrete spherical particles that interact with each other via potentials. In our numerical investigations we are particularly interested in the dynamics of material fragmentation upon impact. We model a typical HVI experiment configuration where a sphere strikes a thin plate and investigate the properties of the resulting debris cloud. We provide a quantitative computational analysis of the resulting debris cloud caused by impact and a comprehensive parameter study by varying key parameters of our model. We compare our findings from the simulations with recent HVI experiments performed at our institute. Our findings are that the DEM method leads to very stable, energy–conserving simulations of HVI scenarios that map the experimental setup where a sphere strikes a thin plate at hypervelocity speed. Our chosen interaction model works particularly well in the velocity range where the local stresses caused by impact shock waves markedly exceed the ultimate material strength.
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Materials Science, Metallurgy; Pin geometry; friction stir spot welding; mechanical properties; aluminum alloy
Online: 20 December 2016 (11:15:04 CET)
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Aluminum alloy Al 2024-T3 were successfully joined using friction stir spot jwelding joining (FSSW). Satisfactory joint strengths were obtained at different welding parameters (tool rotational speed, tool plunge depth, dwell time) and tool pin profile (straight cylindrical, triangular and tapered cylindrical). Resulting joints were welded with welded zone. The different tools significantly influenced the evolution on the stir zone in the welds. Lap-shear tests were carried out to find the weld strength. Weld cross section appearance observations were also done. The macrostructure shows that the welding parameters have a determinant effect on the weld strength (x: the nugget thickness, y: the thickness of the upper sheet and SZ: stir zone). The main fracture mode was pull out fracture modes in the tensile shear test of joints. The results of tensile shear tests showed that the tensile-shear load increased with increasing rotational speed in the shoulder penetration depth of 0.2 mm. Failure joints were obrerved in the weld high shoulder penetration depth and insufficient tool rotation.
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Materials Science, Surfaces, Coatings & Films; CuInSe2 electrodeposition; alkaline doping; current sensing atomic force microscopy
Online: 18 December 2016 (09:48:30 CET)
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The local electrical response in alkaline-doped CuInSe2 films prepared by single step electrodeposition onto Cu substrates was studied by current sensing atomic force microscopy. The CIS films were prepared from single baths containing the dopant ions (Li, Na, K or Cs) and were studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and photocurrent response. Increased crystallinity and surface texturing as the ion size increases was observed as well as enhanced photocurrent response in Cs doped CIS. Li and Na doped films have larger conductivity than the undoped film while the K and Cs doped samples display shorter currents and the current images indicate strong charge accumulation in the K and Cs doped films forming surface capacitors. Corrected CAFM IV curves were adjusted with Shockley equation.
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Materials Science, Nanotechnology; W18O49; microstructure; phase transformation; photocatalytic activity
Online: 14 December 2016 (08:33:41 CET)
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Hierarchical tungsten oxide assemblies such as spindle-like, flowers with sharp petals, nanowires and regular hexagonal structures are successfully synthesized via a solvothermal reduction method by simply adjusting the reaction conditions. On the basis of the experimental results, it is determined that the reaction time significantly influences the phase transition, microstructure and photocatalytic activity of the prepared samples. The possible mechanisms for the phase transition and morphology evolution process have been systematically proposed. Moreover, the as-prepared products exhibit significant morphology-depended photocatalytic activity. The flower-like W18O49 prepared at 6 h possesses large specific surface area (150.1 m2g-1), improved separation efficiency of electron-hole pairs and decreased electron-transfer resistance by the photoelectrochemical measurements. As a result, the flower-like W18O49 prepared at 6 h exhibits the highest photocatalytic activity for the degradation of Methyl orange aqueous solution. The radical trap experiments showed that the degradation of MO was driven mainly by the participation of h+ and •O2− radicals.
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Materials Science, Surfaces, Coatings & Films; Cryogenic treatment; wear resistance; Raman intensity rate
Online: 7 December 2016 (11:13:10 CET)
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This study explored the effects of cryogenic treatment on the microstructure, hardness, and wear-resistance of diamond-like carbon (DLC) by cryogenically treating NAK 80 mold steel coated with DLC. Raman spectroscopy analyzed the structure of the DLC film. Nanoindenter analyzed the hardness and Young’s modulus of the film, and their relationship determined the wear resistance. Wear test assessed the wear rate and friction coefficient of the DLC film. The results showed that cryogenic treatment increased the rate of carbide precipitation and refined the grain structure. Raman spectroscopy indicated that the Raman intensity rate (ID/IG) of treated DLC films was smaller than those without cryogenic treatment. When the sp3 bond increased, the hardness and wear-resistance of the DLC film also increased.
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Materials Science, Biomaterials; water-based polyurethane; hyaluronic acid; cartilage tissue engineering; scaffold
Online: 30 November 2016 (04:28:15 CET)
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Diseases in articular cartilages have affected millions of people globally. Although the biochemical and cellular composition of articular cartilages is relatively simple, there is the limitation in self-repair ability of cartilage. Therefore, developing the strategies for cartilage repair is very important. Here, we reported a new manufacturing process of water-based polyurethane based photosensitive materials with hyaluronic acid and applied the materials for 3D printed customized cartilage scaffolds. The scaffold has high cytocompatibility and is one that closely mimics the mechanical properties of articular cartilages. It is suitable for culturing human Wharton's jelly mesenchymal stem cells (hWJMSCs) and the cells showed an excellent chondrogenic differentiation capacity. We consider that the 3D printing hybrid scaffolds may have potential in customized tissue engineering and facilitate the development of cartilage tissue engineering.
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Materials Science, Other; recycled ceramic mortars, stress-strain of mortars, elasticity module of mortars, recycled ceramic aggregates, toughness of recycled mortars, resilience of recycled mortars, formulation of recycled mortar behavior by numerical simulation
Online: 28 November 2016 (17:47:31 CET)
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The difficult current environmental situation, caused by construction industry residues containing ceramic materials could be improved by using these materials as recycled aggregates in mortars, with their processing causing a reduction in their use in landfill, contributing to recycling and also minimizing the consumption of virgin materials. Although some research is currently being carried out into recycled mortars, little is known about their stress-strain (σ-ε); therefore this work will provide the experimental results obtained from recycled mortars with recycled ceramic aggregates (with contents of 0, 10, 20, 30, 50 and 100%), such as: the density, the compression strength, as well as the σ-ε curves representative of their behavior. The values obtained from the analysis process of the results are those of: σ (elastic ranges and failure maximum), ε (elastic ranges and failure maximum), and Resilience and Toughness; in order to finally obtain, through numerical analysis, the equations to predict their behavior (related to their recycled content). At the end of the investigation it is established that mortars with recycled ceramic aggregate contents of up to 20% could be assimilated just like mortars with the usual aggregates, and the prediction equations produced could be used in cases of similar applications.
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Materials Science, Metallurgy; Al wire, free air ball (FAB),electronic flame-off (EFO), coating, bias test
Online: 18 November 2016 (15:03:34 CET)
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Aluminum wire is a common material for wire bonding due to its resistance to oxidation and low price. It does not melt when becoming a free air ball (FAB) during the electronic flame-off (EFO) process with wettability, and is applied by wedge bonding. This study used 20μm Zn-Coated Al-0.5wt.%Si (ZAS) wires to improve the FAB shape after the EFO process, while maintaining stability of the mechanical properties, including the interface bonding strength and hardness. In order to test circuit stability after ball bonding, the current-tensile test was performed. During the experiment, it was found that 80nm ZAS with wire bonding has lower resistance and higher fusing current. For the bias tensile test, the thicker Zn film diffused into the Al-Si matrix easily, after which the strength was reduced. The ball-bond interfaces had no change in their condition before and after the bias. Accordingly, ZAS could be a promising candidate for ball bonding in the future.
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Materials Science, Polymers & Plastics; textile composite; biaxial tensile; modulus; plain weave fabric (PWF)
Online: 16 November 2016 (13:34:41 CET)
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This paper addresses a new micromechanical model to predict biaxial tensile moduli of plain weave fabric (PWF) composites by considering the interaction between the orthogonal interlacing strands. The two orthogonal yarns in micromechanical unit cell (UC) were idealized as the curved beams with a path depicted by using sinusoidal shape functions. The biaxial tensile moduli of PWF composites were derived by means of the minimum total complementary potential energy principle founded on micromechanics. The biaxial tensile tests were respectively conducted on the RTM-made EW220/5284 PWF composites at five biaxial loading ratios of 0, 1, 2, 3 and ∞ to validate the new model. The predictions from the new model were compared with experimental data and good correlation was achieved between the predictions and actual experiments, demonstrating the practical and effective use of the proposed model. Using the new model, the biaxial tensile moduli of plain weave fabric (PWF) composites could be predicted based only on the properties of basic woven fabric.
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Materials Science, Biomaterials; cell-penetrating peptides (CPPs); reverse-transcriptase-subunit of telomerase (hTERT); GV1001; heat shock protein 90
Online: 11 November 2016 (09:59:30 CET)
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Cell-penetrating peptides (CPPs), a group of small peptides capable of promoting the transport of molecular cargo across the plasma membrane, have become important tools in promoting the cellular uptake of exogenously delivered macromolecules. GV1001, a peptide derived from a reverse-transcriptase subunit of telomerase (hTERT) and developed as a vaccine against various cancers, reportedly has unexpected CPP properties. Unlike typical CPPs, such as the HIV-1 TAT peptide, GV1001 enabled the cytosolic delivery of macromolecules such as proteins, DNA and siRNA via extracellular heat shock protein 90 (eHSP90) and 70 (eHSP70) complexes. The eHSP-GV1001 interaction may have biological effects in addition to its cytosolic delivery function. GV1001 was originally designed as a MHC class II-binding cancer epitope, but its CPP properties may contribute to its strong anti-cancer immune response relative to other telomerase peptide-based vaccines. Cell signaling via eHSP-GV1001 binding may lead to unexpected biological effects, such as direct anticancer or antiviral effects. In this review, we focus on the CPP effects of GV1001 bound to eHSP90 and ehsp70.
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Materials Science, Biomaterials; polyhydroxybutyrate; nanofibrillated cellulose; paper coating; hydrophobicity
Online: 7 November 2016 (06:59:27 CET)
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This study reports on the development of bio-based hydrophobic coatings for packaging papers through deposition of polyhydroxybutyrate (PHB) particles in combination with nanofibrillated cellulose (NFC) and plant wax. In a first approach, PHB particles in micrometer range (PHB-MP) were prepared through a phase-separation technique providing internally nanosized structures. The particles were transferred as a coating by dip-coating filter papers in the particle suspension, followed by sizing with a carnauba wax solution. This approach allowed partial to almost full surface coverage of PHB-MP over the paper surface resulting in static water contact angles of 105° to 122° and 129° to 144° after additional wax coating. In a second approach, PHB particles with submicron sizes (PHB-SP) were synthesized by an oil-in-emulsion (o/w) solvent evaporation method, and mixed in aqueous suspensions with 0 to 7 wt% NFC. After dip-coating filter papers in PHB-SP/NFC suspensions and sizing with a carnauba wax solution, static water contact angles of 112° to 152° were obtained. The intrinsic properties of the particles were analyzed by scanning electron microscopy, thermal analysis and infrared spectroscopy, indicating higher crystallinity for PHB-SP than PHB-MP. The chemical interactions between the more amorphous PHB-MP particles and paper fibers were identified as an esterification reaction, while the morphology of the NFC fibrillar network was playing a key role as binding agent in the retention of more crystalline PHB-SP at the paper surface, hence contributing to higher hydrophobicity.
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Materials Science, Polymers & Plastics; direct laser writing; ultrafast laser; 3D laser lithography; 3D printing; hybrid polymer; integrated microoptics; optical damage; photonics; pyrolysis; ceramic 3D structures
Online: 1 November 2016 (04:59:50 CET)
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We introduce optically clear and resilient free-form micro-optical of pure (non-photosensitized) organic-inorganic SZ2080 material made by femtosecond 3D laser lithography (3DLL). This is advantageous for rapid printing of 3D micro-/nanooptics, including their integration directly onto optical fibers. A systematic study on the fabrication peculiarities and quality of resultant structures is performed. Comparison of microlenses’ resiliency to CW and femtosecond pulsed exposure is determined. Experimental results prove that pure SZ2080 is ∼3 fold more resistant to high irradiance as compared with a standard photo-sensitized material and can sustain up to 1.91 GW/cm2 intensity. 3DLL is a promising manufacturing approach for high-intensity micro-optics for emerging fields in astro-photonics and atto-second pulse generation. Additionally, pyrolysis is employed to shrink structures up to 40% by removing organic SZ2080 constituents. This opens a promising route towards downscaling photonic lattices and creation of mechanically robust glass-ceramic structures.
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Materials Science, Nanotechnology; stainless steel; severe plastic deformation; strength
Online: 31 October 2016 (01:55:15 CET)
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Enhancement in the strength of austenitic steels with a small content of carbon can be achieved by a limited number of methods, among which is the ultrafine-grained (UFG) structure formation, especially efficient with the use of severe plastic deformation (SPD) processing that enables increasing significantly the contribution of grain-boundary strengthening, and also involves a combination of other strengthening factors (work hardening, twins, etc.). In this paper, we demonstrate that the use of SPD processing combined with conventional methods of deformation treatment of metals, such as rolling, may lead to an additional strengthening of UFG steel. Analysis of the results of the study on the change of the microstructure and mechanical properties of the Cr-Ni stainless austenitic steel after a combined deformation reveals a substantial increase in the strength properties of this steel, resulting from a consecutive application of SPD processing via equal-channel angular pressing and rolling at a temperature of 400 С, yielding a strength more than 1.5 times higher that that produced by any of these two methods used separately.
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Materials Science, General Materials Science; A. Ceramics; A. Oxides; C. X-ray diffraction; D. Crystal structure; D. Microstructure
Online: 28 October 2016 (08:09:48 CEST)
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The aim of this work is to compare two softwares (MAUD and TOPAS) based on the Rietveld algorithm and to test the concept of tolerance factor using the dissolution at high temperature of yttrium into BaTiO3. In general, both softwares give up different values of the crystalline parameters however the trends are similar in most cases but the analysis of the strain and crystallite size in the BaTiO3 crystals suggests that, in this particular case, MAUD offered results more consistent with the expected behavior. Using the crystalline parameters calculated by Rietveld, the tolerance factor values were obtained and these data suggest even better stability in the crystalline structure than that expected using theoretical parameters. Tolerance factor concept also indicates that Ti4+ should be preferred.
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Materials Science, Nanotechnology; immobilization, lipase, magnetic nanoparticles, chitosan, collagen, squaric acic
Online: 27 October 2016 (18:40:02 CEST)
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The synthesis of new collagen, chitosan and chitosan-collagen coated magnetic nanoparticles have been done. Two types of cross-linkers for polymer shell stabilization were used: glutaraldehyde (Gla) as a standard cross-linker and new one – squaric acid (SqA). Structure and morphology of prepared nanoparticles were characterized by ATR-FT IR, XRD and TEM analysis. The immobilization of lipase from Candida rugosa was performed on the nanoparticles surface. The amount of immobilized enzyme was quantified by the Bradford method. All of lipase-biopolymers coated nanoparticles were characterized with good activity recovery. A little hyperactivation of lipase immobilized on nanoparticles with SqA was observed. All of prepared lipase-immobilized nanoparticles were characterized with very good reusability.
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Materials Science, General Materials Science; Moiré patterns; MoS2; Graphene; WS2; WSe2; HRTEM
Online: 24 October 2016 (05:03:50 CEST)
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We present a series of computer-assisted high resolution transmission electron (HRTEM) simulations to determine Moiré patters by induced twisting effects between slabs at rotational angles of 3°, 5°, 8°, and 16°, for molybdenum disulfide, graphene, tungsten disulfide, and tungsten selenide layered materials. In order to investigate the electronic structure, a series of numerical simulations using DFT methods was completed using CASTEP with a generalized gradient approximation to determine both band structure and density of states on honeycomb like new superlattices. Our results indicate metallic transitions when rotation approaches 8° with respect to each other for most of the two-dimensional systems that were analyzed.
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Materials Science, Other; GaN ultraviolet photodetector; periodic trapezoid column-shape patterned sapphire substrate; responsivity; UV-to-visible rejection ratio
Online: 18 October 2016 (08:19:48 CEST)
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GaN ultraviolet photodetector with metal-semiconductor-metal structure is achieved by growing on a periodic trapezoid column-shape patterned sapphire substrate using metalorganic chemical vapor deposition. Under 5-V reverse bias, the photodetector fabricated on such patterned sapphire substrate exhibits a lower dark current, a higher photocurrent, and a 476 % enhancement in the maximum responsivity as compare with those of the photodetector fabricated on conventional flat sapphire substrate. It is also found that the much larger UV-to-visible rejection ratio and the fact that responsivity drops in a smaller cut-off region are observed from photodetector fabricated by using a periodic trapezoid column-shape patterned sapphire substrate. These phenomena may all be attributed to the reduction of threading dislocation density and the improved quality of GaN film, as well as the internal reflection and/or scattering effect on the interface between GaN film and the periodic trapezoid column-shape pattern of the substrate.
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Materials Science, Metallurgy; Fe-Cr alloy; oxidation; sulfidation; H2S corrosion
Online: 18 October 2016 (08:04:51 CEST)
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Fe-(9, 19, 28, 37)wt.% Cr alloys were corroded at 700 and 800 oC for 70 h under 1 atm of N2,
1 atm of N2/3.2%H2O-mixed gas, and 1 atm of N2/3.1%H2O/2.42%H2S-mixed gas. The corrosion rate of
Fe-9Cr alloy increased with the addition of H2O, and furthermore with the addition of H2S in N2 gas.
Fe-9Cr alloy was always nonprotective. In contrast, Fe-(19, 28, 37) wt.%Cr alloys were protective in N2 and N2/H2O-mixed gas because of formation of the Cr2O3 layer. They were, however, nonprotective in N2/H2O/H2S-mixed gas because sulfidation dominated to form the outer FeS layer and the inner Cr2S3 layer containing some FeCr2S4.
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Materials Science, Other; steel slag; electric arc furnace slag; magnetite; radiation shielding concrete; concrete; EAF; aggregate
Online: 4 October 2016 (09:28:42 CEST)
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Electric arc furnace oxidizing slag (EAF) has a high density of 3.0~3.7 t/m3 and therefore has a high bulk density when mixed with concrete. Extensive research has been conducted on the use of concrete with high unit volume weight as heavyweight concrete for radiation shielding concrete. In this study, to examine the possibility of developing a radiation shielding concrete, the physical properties of normal concrete, magnetite concrete, EAF concrete, and EAF concrete with added iron powder, were compared. Also, their radiation shielding performance was assessed through shielding tests against X-rays and γ-rays. While the unit volume weight of EAF concrete (3.21 t/m3) appeared lower than that of magnetite concrete (3.5 t/m3), the compressive strength of EAF concrete was greater than those of magnetite and normal concretes. The radiation shielding ratio of magnetite concrete was observed to be 93.9% from the X-ray shielding test, followed by 91.2% of EAF concrete, and 73.7% of normal concrete, indicating a linear relationship with unit volume weight. From the γ-ray shielding test, the performance of EAF and magnetite concretes appeared to be similar. Based on the excellent physical properties and radiation shielding performance of EAF concrete, its potential applicability as radiation shielding concrete was confirmed.
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Materials Science, Surfaces, Coatings & Films; CO2 enhanced capture; SBA-15 habilitation for CO2 sorption; desilication; silanol functionalization; covalent coordinated CO2 deposition
Online: 29 September 2016 (12:38:24 CEST)
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Special preparation of SBA-15 materials has been carried out for creating adsorbents exhibiting an enhanced and selective adsorption toward CO2. This creation starts from an adequate conditioning of the silica surface, via a thermo-alkaline treatment to increase the population of silanol species on it. CO2 adsorption is only reasonably achieved when the SiO2 surface becomes aminated after put in contact with a solution of an amino alkoxide compound in the right solvent. Unfunctionalized and amine-functionalized substrates were characterized through X-ray diffraction, N2 sorption, Raman spectroscopy, electron microscopy, 29Si solid-state NMR, and NH3 thermal programmed desorption. These analyses proved that the thermo-alkaline procedure desilicates the substrate and eliminates the micropores (without affecting the SBA-15 capillaries), present in the original solid. NMR analysis confirms that the hydroxylated solid anchors more amino functionalizing molecules than the unhydroxylated material. The SBA-15 sample subjected to hydroxylation and amino- functionalization displays a high enthalpy of interaction, a reason why this solid is suitable for a strong deposition of CO2 but with the possibility of observing a low-pressure hysteresis phenomenon. Contrastingly, CH4 adsorption on amino-functionalized, hydroxylated SBA-15 substrates becomes almost 5 times lesser than the CO2 one, thus giving proof of their selectivity toward CO2.
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Materials Science, Surfaces, Coatings & Films; carbonyl iron; composites film; external magnetic field; microwave absorption properties
Online: 28 September 2016 (10:32:52 CEST)
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The carbonyl iron particles were dispersed in a polychloroprene rubber (CR) matrix under an external magnetic field for practical application as microwave absorption composites film. The film prepared under external magnetic field with a thickness of only 0.54 mm showed least reflection loss of -15.98 dB and the reflection loss value less than -10.0 dB over the frequency range of 11.4~14.8 GHz. In comparison with the microwave absorption properties of calculation by transmission line theory based on the tested relative complex permittivity and permeability and film prepared by general route without external magnetic field, the film made with external magnetic field exhibited more excellent microwave absorption properties, strongly depending on the increment of anisotropy and rearrangement of magnetic particles. The results indicated the composite film made under external magnetic field have excellent microwave absorption properties, which suggest that the composites thin film could be used as a thinner and lighter microwave absorber.
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Materials Science, Surfaces, Coatings & Films; nano-Au particles; NIPAAm hydrogel; plasma treatment; UV grafting
Online: 28 September 2016 (09:49:23 CEST)
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In this study, a new type of temperature sensor device was developed. The circular electrode of the thermal sensitive sensor was modified with TMT and O2 plasma to enhance the conductivity by forming a thin SnOxCy layer on the electrode surface. The Nano-Au particles were subjected to O2 plasma pretreatment to form peroxide groups on the surface. The thermally sensitive sensor was made by mixing the above-treated Nano-Au particles with N-isopropylacrylamide (NIPAAm) to form solution and then UV-induced grafting polymerization of the NIPAAm-containing solution onto the electrode substrate. The composite hydrogels on the electrode introduce thermo-sensitive polymeric surface films for temperature sensing. Using ambient environment resistance test to measure the resistance, the LCST (lower critical solution temperature) of Nano-Au (MUA) mixed with NIPAAm hydrogel was found to be 32 °C. At ambient temperatures higher than LCST, the electrode resistance decreases linearly.
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Materials Science, General Materials Science; neutron absorber; Mo-based composites; ball milling; microstructure; thulium oxide
Online: 27 September 2016 (10:45:47 CEST)
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The microstructural evolution, thermodynamics and kinetics of Mo-21%Tm2O3 (mass fraction, %) powder mixtures during ball milling were investigated using X-ray diffraction and transmission electron microscopy. Ball milling induced Tm2O3 to be decomposed and then dissolved into Mo crystal. The supersaturated nanocrystalline solid solution of Mo (Tm, O) was obtained after 96 h of ball milling. The elements of Mo, Tm and O were distributed uniformly in the ball-milled particles. Based on the semi-experimental theory of Miedema, a thermodynamic model was developed to calculate the driving force of phase evolution. There was no chemical driving force to form a crystal solid solution of Tm atoms in Mo crystal or an amorphous phase because the Gibbs free energy for both processes was higher than zero. For Mo-21%Tm2O3, it was mechanical work, not negative heat of mixing, that provided the driving force to form supersaturated nanocrystalline Mo (Tm, O) solid solution.