Showing papers in "Materials Science and Engineering B-advanced Functional Solid-state Materials in 2012"
TL;DR: In this article, the size of the magnetite nanoparticles was carefully controlled by varying the reaction temperature and through surface modification, which significantly affected the particle size, the electrical conductivity, and the magnetic properties.
Abstract: Magnetite nanoparticles were synthesized via the chemical co-precipitation method using ammonium hydroxide as the precipitating agent. The size of the magnetite nanoparticles was carefully controlled by varying the reaction temperature and through the surface modification. Herein, the hexanoic acid and oleic acid were introduced as the coating agents during the initial crystallization phase of the magnetite. Their structure and morphology were characterized by the Fourier transform infrared spectroscopy (FTIR), the X-ray diffraction (XRD) and the field-emission scanning electron microscopy (FE-SEM). Moreover, the electrical and magnetic properties were studied by using a conductivity meter and a vibrating sample magnetometer (VSM), respectively. Both of the bare magnetite and the coated magnetite were of the cubic spinel structure and the spherical-shaped morphology. The reaction temperature and the surface modification critically affected the particle size, the electrical conductivity, and the magnetic properties of these particles. The particle size of the magnetite was increased through the surface modification and reaction temperature. In this study, the particle size of the magnetite nanoparticles was successfully controlled to be in the range of 10–40 nm, suitable for various biomedical applications. The electrical conductivity of the smallest particle size was 1.3 × 10−3 S/cm, within the semi-conductive materials range, which was higher than that of the largest particle by about 5 times. All of the magnetite nanoparticles showed the superparamagnetic behavior with high saturation magnetization. Furthermore, the highest magnetization was 58.72 emu/g obtained from the hexanoic acid coated magnetite nanoparticles.
589 citations
TL;DR: In this article, the synthesis of Co doped ZnO nanoparticles by combustion method using citric acid as a fuel for 0, 1, 3, 5% and 10% of Co doping was reported.
Abstract: We report the synthesis of Co doped ZnO nanoparticles by combustion method using citric acid as a fuel for 0%, 1%, 3%, 5% and 10% of Co doping. The structural, optical and dielectric properties of the samples were studied. Crystallite sizes were obtained from the X-ray diffraction (XRD) patterns whose values are decreasing with increase in Co content up to 5%. The XRD analysis also ensures that ZnO has a hexagonal (wurtzite) crystal structure and Co2+ ions were successfully incorporated into the lattice positions of Zn2+ ions. The TEM image shows the average particle size in the range of 10–20 nm for 3% Co doped ZnO nanoparticles. The energy band gap as obtained from the UV–visible spectrophotometer was found gradually increasing up to 5% of Co doping. The dielectric constants (ɛ′, ɛ″), dielectric loss (tan δ) and ac conductivity (σac) were studied as the function of frequency and composition, which have been explained by ‘Maxwell Wagner Model’.
168 citations
TL;DR: In this paper, the performance of a patent magnesium alloy Mg-Nd-Zn-Zr (JDBM) and a reference alloy AZ31 was systematically investigated in Hank's physiological solution.
Abstract: The main challenge for the application of magnesium and its alloy as degradable biomaterials lies in their high degradation rates in physiological environment. In the present work, the biodegradable behavior of a patent magnesium alloy Mg–Nd–Zn–Zr (JDBM) and a reference alloy AZ31 was systematically investigated in Hank's physiological solution. The corrosion rate of JDBM (0.28 mm/year) was much slower than that of AZ31 (1.02 mm/year) in Hank's solution for 240 h. After corrosion products were removed, smooth surface of the JDBM was observed by SEM observation compared to many deep pits on the surface of AZ31. Open-circuit potential and potentiodynamic polarization results manifested that pitting corrosion did not occurred on the surface of JDBM at the early period of immersion time due to the formation of a more protective and compact film layer suggested by electrochemical impedance spectroscopy study. The corrosion rate of magnesium alloys was found to slow down in dynamic corrosion in comparison with that in the static corrosion. This provided the basis for scientific evaluation of in vitro and in vivo corrosion behavior for degradable biomagnesium alloy. The present results suggest that the new patent magnesium alloy JDBM is a promising candidate as degradable biomaterials and is worthwhile for further investigation in vivo corrosive environment.
146 citations
TL;DR: In this article, water-based silver pastes, adapted for screen printing, were formulated with different silver contents (67-75%). These pastes allowed screen printing onto low temperature co-fired ceramic (LTCC) of narrow conductive tracks with a 60-μm line width and a 3.6-10−8-Ωm electrical resistivity.
Abstract: Environmentally friendly, water-based silver pastes, adapted for screen printing, were formulated with different silver contents (67–75%). These pastes allowed screen printing onto low temperature co-fired ceramic (LTCC) of narrow conductive tracks with a 60 μm line width and a 3 × 10−8 Ω m electrical resistivity. Inks were formulated with a mixture of spherical and flake shape silver particles with 2–4 μm mean diameter. Rheological behaviour of pastes was studied in order to determine its effect on printed lines properties. Prepared inks were then screen printed and sintered under normal atmosphere at 875 °C. As expected, electrical properties depended on silver content. Resistivity values varying from 1.6 × 10−8 to 3.3 × 10−8 Ω m were calculated over 36.3 cm line length. These values are very close to bulk silver resistivity (1.6 × 10−8 Ω m). Compared to previous research and commercial pastes, the newly formulated pastes reached equivalent or even better conductivities with lower silver content (70% by weight).
130 citations
TL;DR: In this article, a modified sol-gel method was used to obtain the codoped Er 3+ and Yb 3+ nanocrystalline ZrO 2 -B 2 O 3 phosphor.
Abstract: Codoped Er 3+ and Yb 3+ nanocrystalline ZrO 2 –B 2 O 3 phosphor obtained by a modified sol–gel method is demonstrated. The addition of up to 2.5 mol% B 2 O 3 to nanocrystalline ZrO 2 :Yb(2%), Er(1%) keep the tetragonal rare-earth stabilized ZrO 2 phase; whereas higher B 2 O 3 content destabilize the tetragonal phase, leading to the tetragonal to monoclinic transition with no tetragonal ZrO 2 phase segregation. Visible upconversion of the luminescent active ions, Er 3+ and Yb 3+ , depend strongly on B 2 O 3 content. The PL intensity is strongly quenched for high B 2 O 3 content due to increasing multiphonon relaxation processes related to B O and B O B vibronic modes.
128 citations
TL;DR: In this article, the oxidation of Fe in pure oxygen between 400 and 600 C was investigated in order to obtain Fe oxidation in the presence of pure oxygen, and it was shown that Fe oxidizes at a rate between 400 to 600 C.
Abstract: a b s t r a c t The oxidation of Fe in pure oxygen between 400 ◦ C and 600 ◦ C has been investigated in order to obtain
113 citations
111 citations
TL;DR: In this paper, the effect of AlN filler content (0.1 − 0.7 volume fraction) on thermal conductivity, relative permittivity, and dielectric loss were investigated.
Abstract: Polymethyl methacrylate (PMMA) composites filled with Aluminum Nitride (AlN) were prepared by powder processing technique. The microstructures of the composites were investigated by scanning electron microscopy techniques. The effect of AlN filler content (0.1–0.7 volume fraction (vf)) on the thermal conductivity, relative permittivity, and dielectric loss were investigated. As the vf of AlN filler increased, the thermal conductivity of the specimens increased. The thermal conductivity and relative permittivity of AlN/PMMA composites with 0.7 vf AlN filler were improved to 1.87 W/(m K) and 4.4 (at 1 MHz), respectively. The experimental thermal conductivity and relative permittivity were compared with that from simulation model.
100 citations
TL;DR: In this article, the free vibration of AISI 304 stainless steel sandwich beams with pyramidal truss core is investigated, and the results show that the theoretical solutions agree well with the numerical results.
Abstract: Free vibration of AISI 304 stainless steel sandwich beams with pyramidal truss core is investigated in the present paper. The lattice truss core is transformed to a continuous homogeneous material. Considering the deformation characteristics of the sandwich beam, the following assumptions are made: (1) the thickness of the sandwich beam remains constant during deformation; (2) for the thin face sheets, only bending deformation is considered, neglecting the effect of transverse shear deformation; (3) for the core, only shear deformation is considered as the core is too weak to provide a significant contribution to the bending stiffness of the sandwich beam. The shear stress is assumed to be constant along the thickness of the core. The governing equation of free vibration is derived from Hamilton's principle, and the natural frequencies are calculated under simply supported boundary conditions. Finally, numerical simulation is carried out to get the mode shapes and natural frequencies. Our results show that the theoretical solutions agree well with the numerical results. It indicates the present method would be useful for free vibration analysis of sandwich beams with lattice truss core.
92 citations
TL;DR: In this article, double extrusion process was adopted to refine microstructure and improve mechanical properties of Mg-2.25Nd-Zn-Zr alloy, which is a promising biodegradable magnesium alloy due to good biocompatibility, desired uniform corrosion mode and outstanding corrosion resistance.
Abstract: Mg–Nd–Zn–Zr alloy is a novel and promising biodegradable magnesium alloy due to good biocompatibility, desired uniform corrosion mode and outstanding corrosion resistance in simulated body fluid (SBF). However, the corrosion resistance and mechanical properties should be improved to meet the requirement of the biodegradable implants, such as plates, screws and cardiovascular stents. In the present study, double extrusion process was adopted to refine microstructure and improve mechanical properties of Mg–2.25Nd–0.11Zn–0.43Zr and Mg–2.70Nd–0.20Zn–0.41Zr alloys. The corrosion resistance of the alloys after double extrusion was also studied. The results show that the microstructure of the alloys under double extrusion becomes much finer and more homogeneous than those under once extrusion. The yield strength, ultimate tensile strength and elongation of the alloys under double extrusion are over 270 MPa, 300 MPa and 32%, respectively, indicating that outstanding mechanical properties of Mg–Nd–Zn–Zr alloy can be obtained by double extrusion. The results of immersion experiment and electrochemical measurements in SBF show that the corrosion resistance of Alloy 1 and Alloy 2 under double extrusion was increased by 7% and 8% respectively compared with those under just once extrusion.
92 citations
TL;DR: In this paper, the performance of 9,10-anthraquinone (AQ), and 5,7,12,14-pentacenetetrone (PT) as active materials for rechargeable lithium batteries was investigated.
Abstract: The performance of 9,10-anthraquinone (AQ), and 5,7,12,14-pentacenetetrone (PT) as active materials for rechargeable lithium batteries was investigated. Positive-electrodes in which AQ and PT were incorporated showed initial discharge capacities of greater than 200 mAh/g (AQ or PT) . The obtained discharge capacities suggest that a multi-electron redox reaction takes place in each derivative. The discharge capacity of the positive-electrode with AQ rapidly decreased during the charge/discharge cycles; however, the positive-electrode with PT showed a relatively good cycle-life performance; it maintained about 80% of the initial capacity even after 100 cycles.
TL;DR: In this paper, the influence of high-temperature pre-precipitation treatment on corrosion behaviors of 7055 aluminum alloy is investigated, and the results indicate that the Cu-rich, discrete and coarse grain-boundary precipitates and the decreasing potential difference among inter-granular phases in the grain boundary are responsible for the enhancement of corrosion resistance.
Abstract: In this paper the influence of high-temperature pre-precipitation treatment on corrosion behaviors of 7055 aluminum alloy is investigated. High-temperature pre-precipitation treatment enhances the discontinuing distribution of the coarse precipitates along the grain boundary, and increases the Cu content of grain-boundary precipitates, which obviously improves stress corrosion resistance, suppresses the serve fracture of sub-grain boundary under the stress corrosion and reduces inter-granular corrosion (IGC) susceptibility with the same strength and ductility. The electrochemical corrosion results of inter-granular phases indicate that the Cu-rich, discrete and coarse grain-boundary precipitates and the decreasing potential difference among inter-granular phases in the grain boundary are responsible for the enhancement of corrosion resistance of 7055 alloy.
TL;DR: In this paper, hydroxyapatite/TiO2 composite photocatalysts were obtained from sol-gel prepared TiO2 and commercial hydroxyapatitic (HA) powders.
Abstract: Hydroxyapatite/TiO2 composite photocatalysts were obtained from sol–gel prepared TiO2 and commercial hydroxyapatite (HA) powders. Composites with different HA/TiO2 ratio were studied to assess the influence of HA on the morphology and the photocatalytic behavior of the materials. Morphological SEM analysis revealed that the presence of HA diminishes the aggregation of TiO2 particles and leads to their higher dispersion in the composites that was confirmed by the N2 adsorption–desorption isotherms and Barret–Joyner–Halenda analysis. The photocatalytic activity of the prepared catalysts was examined by monitoring photocatalytic oxidation of NOx model gases over catalysts under UV illumination. The NOx oxidation over the composite catalysts was improved in comparison with pure TiO2 powder. Moreover, the decrease of the TiO2 content, which is the photocatalytically active component in the composites, resulted in enhanced NOx removal. Maximum activity was recorded for composites with HA/TiO2 ratios 1 and 2 that was related to improved TiO2 dispersion and NO2 trapping by the composite materials.
TL;DR: In this paper, a multiscale approach for vibration frequency analysis of graphene/polymer composites is presented, where the graphene is modelled at the atomistic scale, and the matrix deformation is analysed by the continuum finite element method.
Abstract: This paper presents a multiscale approach for vibration frequency analysis of graphene/polymer composites. The graphene is modelled at the atomistic scale, and the matrix deformation is analysed by the continuum finite element method. Inter-connectivity between graphene and polymer matrix are assumed to be bonded by van der Waals interactions at the interface. The impact of geometrical configuration (armchair and zigzag), boundary conditions and length on the overall stiffness of the graphene reinforced plastics (GRP) is studied. The natural frequency and vibrational mode shapes of GRP studied have displayed dependence on the length and also the boundary conditions. The exceptional vibrational behaviour and large stiffness displayed by GRP makes them a potential replacement for conventional composite fibres such as carbon and glass fibres.
TL;DR: In this article, the morphology, thermal stability, function groups and crystallinity of the electrospun membranes were characterized by scanning electron microscope (SEM), thermal analysis (TG), Fourier transform infrared spectra (FT-IR), and differential scanning calorimetry (DSC), respectively.
Abstract: Nanofibrous membranes based on Poly (vinyl difluoride) (PVdF)-Poly (vinyl chloride) (PVC) (8:2, w/w) were prepared by electrospinning and then they were soaked in a liquid electrolyte to form polymer electrolytes (PEs). The morphology, thermal stability, function groups and crystallinity of the electrospun membranes were characterized by scanning electron microscope (SEM), thermal analysis (TG), Fourier transform infrared spectra (FT-IR) and differential scanning calorimetry (DSC), respectively. It was found that both electrolyte uptake and ionic conductivity of the composite PEs increased with the addition of PVC. The composite PVdF–PVC PEs had a high ionic conductivity up to 2.25 × 10 −3 S cm −1 at 25 °C. These results showed that nanofibrous PEs based on PVdF–PVC were of great potential application in polymer lithium-ion batteries.
TL;DR: This review attempts to provide a comprehensive analysis of the current research activity in the development of CaP based ceramic and polymer-ceramic hybrid systems for non-viral gene delivery.
Abstract: Gene therapy has garnered much interest due to the potential for curing multiple inherited and/or increases in the acquired diseases. As a result, there has been intense activity from multiple research groups for developing effective delivery methods and carriers, which is a critical step in advancing gene delivery technologies. In order for the carriers to effectively deliver the genetic payloads, multiple extracellular and intracellular barriers need to be overcome. Although overcoming these challenges to improve the effectiveness is critical, the development of safe gene delivery agents is even more vital to assure its use in clinical applications. The development of safe and effective strategies has therefore been a major challenge impeding gene therapy progress. In this regard, calcium phosphate (CaP) based nano-particles has been considered as one of the candidate non-viral gene delivery vehicles, but has been plagued by inconsistent and low transfection efficiencies limiting its progress. There has been major research effort to improve the consistency and effectiveness of CaP based vectors. Currently, it is therefore thought that by controlling the various synthesis factors such as Ca/P ratio, mode of mixing, and type of calcium phosphate phase, such variability and inefficiency could be modulated. This review attempts to provide a comprehensive analysis of the current research activity in the development of CaP based ceramic and polymer-ceramic hybrid systems for non-viral gene delivery. Preliminary transfection results of hydroxyapatite (HA or NanoCaPs), amorphous calcium phosphate (ACP) and brushite phases are also compared to assess the effect of various CaP phases, and correspondingly, changes in the dissolution characteristic of the pDNA-CaP complex on the gene transfection efficiency.
TL;DR: Li and Co co-doped NiO (LCNO) ceramics prepared by a simple sol-gel route have been investigated in this paper, where the relationship between the activation energies of dielectric relaxation and conduction and charge compensation mechanism in this system were discussed.
Abstract: Dielectric properties and charge compensation of Li and Co co-doped NiO (LCNO) ceramics prepared by a simple sol–gel route have been investigated. The concentration of Co makes a great influence on microstructure, dielectric properties and charge compensation mechanism of the LCNO ceramics. Grain size of the ceramics increases from 5.6 μm to 7.2 μm with dependence on Co concentration. By using a complex impedance analysis at different temperatures, the samples exhibit an electrically heterogeneous structure, which is responsible for a giant dielectric permittivity. The relationship between the activation energies of dielectric relaxation and conduction and charge compensation mechanism in this system were discussed.
TL;DR: In this paper, the intent of this study was to obtain 4A zeolites from kaolin in order to obtain 5A Zeolites through ionic exchange with the previously synthesized zeolite.
Abstract: The synthesis of adsorbing zeolite materials requires fine control of the processing variables. There are distinct process variable settings for obtaining specific desired types of zeolites. The intent of this study was to obtain 4A zeolites from kaolin in order to obtain 5A zeolites through ionic exchange with the previously synthesized zeolite. This zeolite 5A was used as an adsorbent for arsenic ions. The results obtained were satisfactory.
TL;DR: In this article, the main electrical and photocurrent properties of the Au/PVA(Co-doped)/n-Si diodes were investigated by using currentvoltage (I-V) measurements at dark and various illumination intensity.
Abstract: In this work, we investigate the some main electrical and photocurrent properties of the Au/PVA(Co-doped)/n-Si diodes by using current–voltage (I–V) measurements at dark and various illumination intensity. Two types of diodes with and without polyvinyl alcohol (PVA) (Co-doped) polymeric interfacial layer were fabricated and measured at room temperature. Results show that the polymeric interfacial layers and series resistance (Rs) strongly affect the main electrical parameters of these structures. Also, metal/polymer/semiconductor (MPS) diode with PVA (Co-doped) interfacial organic layer is very sensitive to the light such that the current in reverse bias region increase by 103–104 times with the increasing illumination intensity. The open circuit voltage Voc and short-circuit current Isc values of this MPS diode under 100 mW/cm2 illumination intensity were found as 0.28 V and 19.3 μA, respectively.
TL;DR: In this article, Ag2S quantum dots (QDs) were deposited on ordered TiO2 nanotube arrays (TNTAs) using a sequential chemical bath deposition (S-CBD) approach.
Abstract: Ag2S quantum dots (QDs) were deposited on ordered TiO2 nanotube arrays (TNTAs) using a sequential chemical bath deposition (S-CBD) approach. AgNO3 and thiourea were used as the precursor materials of Ag+ and S2− ions, respectively. The decoration of Ag2S QDs significantly shifted the absorption spectrum of the TNTAs to visible light region. As a result, Ag2S QDs-sensitized TNTAs exhibited much higher photocurrent density than pure TNTAs under visible light irradiation.
TL;DR: In this paper, Fe 78 Si 9 B 13 metallic glass was employed to remediate wastewater contaminated with a mixture of organic dyes, and the removal rate of chemical oxygen demand was up to 23.93% in 30min and 21.67% in 45min, respectively.
Abstract: This work pioneered the use of the Fe 78 Si 9 B 13 metallic glass ribbons in wastewater treatment. Fe 78 Si 9 B 13 metallic glass was employed to remediate wastewater contaminated with a mixture of organic dyes. The removal rate of chemical oxygen demand (COD) with Fe 78 Si 9 B 13 metallic glass and metallic Fe 0 was up to 23 ± 0.93% in 30 min and 21 ± 0.67% with in 45 min, respectively. The dosage of Fe-based metallic glass was only 1/25 of that of metallic Fe 0 to obtain equivalent effects. The mechanism of wastewater treatment through Fe-based metallic glasses is discussed.
TL;DR: In this paper, a terpyridine-modified cellulose nanocrystals with azide functional groups with 2,2′:6′,2″-terPyridine side chains were obtained via surface modification of cellulose nanocellulosic material.
Abstract: Due to their natural origin, biocompatibility, and non-toxicity, cellulose nanocrystals are promising candidates for applications in nanomedicine. Highly fluorescent nanocellulosic material was prepared via surface modification of cellulose nanocrystals with 2,2′:6′,2″-terpyridine side chains followed by supramolecular assembly of terpyridine-modified perylene dye onto the terpyridine-modified cellulose nanocrystals (CTP) via RuIII/RuII reduction. The prepared terpyridine-modified cellulose-RuII-terpyridine-modified perylene (CTP-RuII-PeryTP) fluorescent nanocrystals were characterized using cross-polarized/magic angle spin 13C nuclear magnetic resonance (CP/MAS 13C NMR), Fourier transform infrared (FTIR), UV–visible, and fluorescence spectroscopy. In addition, further self-assembly of terpyridine units with azide functional groups onto CTP-RuII-PeryTP was possible via repeating the RuIII/RuII reduction protocol to prepare supramolecular fluorescent nanocrystals with azide functionality (CTP-RuII-PeryTP-RuII-AZTP). The prepared derivative may have potential application in bio-imaging since the terminal azide groups can be easily reacted with antigens via “Click” chemistry reaction.
TL;DR: In this paper, the effect of alloying elements on the microstructure of dissimilar joints of a Mg-Zn-Zr alloy (ZK60) and titanium by using friction stir welding (FSW) was examined.
Abstract: Friction stir welding (FSW) is a solid-state joining process, and the joining temperature is lower than that in the fusion welding process. The effect of alloying elements on the microstructure of dissimilar joints of a Mg–Zn–Zr alloy (ZK60) and titanium by using FSW, was examined. A commercial ZK60 and a titanium plates with 2 mm in thickness was butt-joined by inserting the probe into the ZK60 plate, and slightly offset into the titanium plate side to ensure the direct contact between them. The average tensile strength of the joint was 237 MPa, which was about 69% of that of ZK60 and a fracture occurred mainly in the stir zone of ZK60 and partly at the joint interface. A thin Zn and Zr-rich layer with about 1 m in thickness was formed at the joint interface, which affected the tensile strength of the dissimilar joint of ZK60 and titanium.
TL;DR: In this article, a one step sonochemical route has been developed to prepare graphene-Mn 2 O 3 nanocomposite with uniform distribution of Mn 2O 3 nanoparticles throughout the surface of graphene nanosheet, which can store electrons and circulate them towards dye molecules through the formation of hydroxyl radical under the exposure of UV-light.
Abstract: A one step sonochemical route has been developed to prepare graphene–Mn 2 O 3 nanocomposite with uniform distribution of Mn 2 O 3 nanoparticles throughout the surface of graphene nanosheet. Growth of such nanoparticles over this two dimensional carbon network is simply accelerated by the simultaneous reduction of potassium permanganate along with graphene oxide, in which metal ions are first anchored through binding with oxy-functional groups of graphene oxide and finally reduced by hydrazine. The final product ensure a new platform for the photodegradation of organic dyes, as it can store electrons and circulate them towards dye molecules through the formation of hydroxyl radical under the exposure of UV-light. Almost 80% photocatalytic degradation of eosin, methylene blue and rhodamine B have been observed within few minutes, which has not been obtained by using bare manganese oxide itself.
TL;DR: In this article, the synthesis of calcium hydroxyapatite (Ca-HA) starting from calcium carbonate and different orthophosphate sources, including Orthophosphoric acid, potassium, sodium and ammonium dihydrogen orthophophosphates, was investigated under ambient conditions.
Abstract: The synthesis of calcium hydroxyapatite (Ca-HA) starting from calcium carbonate and different orthophosphate sources, including orthophosphoric acid, potassium, sodium and ammonium dihydrogen orthophosphates, was investigated under ambient conditions. The reaction started with calcium carbonate dissolution in an acid medium, followed by rapid precipitation of calcium cations with orthophosphate species to form calcium phosphate based particles which were in the size range of 0.4–1 μm. These particles then agglomerated into much larger ones, up to 350 μm in diameter (aggregates). These aggregates possessed an unstable porous structure which was responsible for the porosity of the final products. The highest specific surface area and pore volume were obtained with potassium dihydrogen orthophosphate. On the other hand, orthophosphoric acid led to the highest dissolution of calcium carbonate and the complete precipitation of orthophosphate species. Under ambient conditions, calcium phosphate based solid products of low crystallinity were formed. Different intermediates were identified and a reaction pathway proposed.
TL;DR: In this article, a rose-like Bi2WO6 photocatalyst was successfully synthesized through a simple hydrothermal route using thiourea and acetic acid as complexing agents.
Abstract: Hierarchical rose-like Bi2WO6 photocatalyst was successfully synthesized through a simple hydrothermal route using thiourea and acetic acid as complexing agents. The as-synthesized product was determined as pure orthorhombic Bi2WO6 based on the results of X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. The photocatalyst had an average diameter of 2–3 μm and it was constructed by many nanoflakes. The surfaces of these nanoflakes were coarse and had many nanocrystals on them. The hierarchical rose-like structure was formed through a typical hierarchical assembly process with the synergistic action of acetic acid and thiourea. The photocatalyst showed excellent visible-light-driven photocatalytic performance, it could decompose rhodamine B(RhB) within 50 min. This excellent performance resulted from its special microstructure and the relatively large surface area.
TL;DR: In this article, the extrusion process of a thin-walled hollow aluminum profile was simulated by means of the HyperXtrude commercial software, and the effect of extrusion stem speed on metal flow behavior at die exit, temperature distribution, extrusion force, and welding pressure was investigated.
Abstract: Extrusion stem speed is one of important process parameters during aluminum profile extrusion, which directly influences the profile quality and choice of extrusion equipments. In this paper, the extrusion process of a thin-walled hollow aluminum profile was simulated by means of the HyperXtrude commercial software. Through a serial of numerical simulation, the effects of stem speed on extrusion process, such as metal flow behavior at die exit, temperature distribution, extrusion force, and welding pressure, have been investigated. The numerical results showed that there existed an optimum value of stem speed for flow velocity distribution. With the increasing stem speed, the temperature of the extrudate and required extrusion force increased, and the welding quality of extrudate would be improved. Through comprehensive comparison and analysis, the appropriate stem speed could be determined for practical extrusion production. Thus, the research results could give effective guideline for determining initial billet and die temperature and choosing the proper extrusion press in aluminum profile industry.
TL;DR: Amorphous silicon has been successfully electrodeposited on copper using a SiCl 4 based organic electrolyte under galvanostatic conditions as mentioned in this paper, and the deposited films were tested for possible application as anodes for Li-ion battery.
Abstract: Amorphous silicon has been successfully electrodeposited on copper using a SiCl 4 based organic electrolyte under galvanostatic conditions. The electrodeposited silicon films were characterized for their composition, morphology and structural characteristics using glancing angle X-ray diffraction (GAXRD), scanning electron microscopy (SEM), and Raman spectroscopy. GAXRD and Raman analyses clearly confirm the amorphous state of the deposited silicon film. The deposited films were tested for possible application as anodes for Li-ion battery. The results indicate that this binder free amorphous silicon anode exhibits a reversible capacity of ∼1300 mAh g −1 with a columbic efficiency of >99.5% up to 100 cycles. Impedance measurements at the end of each charge cycle show a non-variable charge transfer resistance which contributes to the excellent cyclability over 100 cycles observed for the films. This approach of developing thin amorphous silicon films directly on copper eliminates the use of binders and conducting additives, rendering the process simple, facile and easily amenable for large scale manufacturing.
TL;DR: In this article, a solar cell is fabricated by sensitizing porous TiO2 thin film with SnS QDs and the cell characteristics are analyzed using two different size quantum dots.
Abstract: Tin sulphide (SnS) quantum dots of size ranging from 2.4 to 14.4 nm are prepared by chemical precipitation method in aqueous media. Growth of the SnS particles is monitored by controlling the deposition time. Both XRD and SAED patterns confirm that the particles possess orthorhombic structure. The uncapped SnS particles showed secondary phases like Sn2S3 and SnS2 which is visible in the SAED pattern. From the electrochemical characterization. HOMO-LUMO levels of both TiO2 and SnS are determined and the band alignment is found to be favorable for electron transfer from SnS to TiO2. Moreover, the HOMO-LUMO levels varied for different particle sizes. Solar cell is fabricated by sensitizing porous TiO2 thin film with SnS QDs. Cell structure is characterized with and without buffer layer between FTO and TiO2. Without the buffer layer, cell showed an open circuit voltage (V-oc) of 504 mV and short circuit current density (J(sc)) of 2.3 mA/cm(2) under AM1.5 condition. The low fill factor of this structure (15%) is seen to be increased drastically to 51%, on the incorporation of the buffer layer. The cell characteristics are analyzed using two different size quantum dots. (C) 2012 Elsevier B.V. All rights reserved.
TL;DR: In this article, the anodizing process was performed on Ti-6Al-4V alloy surface to enhance the adhesion of these composite coatings on Ti alloy, and the nano-TiO 2 particles could be co-deposited on the Ti−6Al−4V alloys and capable of reinforcing the hydroxyapatite coating, subsequently increasing the hardness and refining the structure.
Abstract: This study elucidated structure and mechanical properties of the electroplated hydroxyapatite/nano-TiO 2 composite coatings on Ti–6Al–4V alloy. Their effect on the corrosion and wear corrosion resistance in Hanks’ solution was examined as well. The anodizing process was performed on Ti–6Al–4V alloy surface to enhance the adhesion of these composite coatings on Ti alloy. Anodizing treatment was then conducted at 10 V at room temperature with different times of 40, 50, 60, 120 and 180 min. Experimental results indicate that the hardness of Ti–6Al–4V alloy was increased due to the anodizing treatment, capable of improving the adhesion of electroplated calcium phosphate coating in addition to the electroplated hydroxyapatite/nano-TiO 2 composite coatings. Additionally, the coatings on anodic substrate exhibited a higher uniformity and Ca/P ratio and thickness than that on nonanodized substrate. The nano-TiO 2 particles could be co-deposited on the Ti–6Al–4V alloys and capable of reinforcing the hydroxyapatite coating, subsequently increasing the hardness and refining the structure. Moreover, the corrosion and wear corrosion resistance of the electroplated hydroxyapatite/nano-TiO 2 composite coatings were also improved significantly when increasing the duration of anodizing alloy substrates.