Showing papers in "Journal of Alloys and Compounds in 2013"
TL;DR: The development of metal deposition processes based on electroless nickel, alloy and composite coatings on various surfaces has witnessed a surge in interest among researchers, with many recent applications made possible from many excellent properties as mentioned in this paper.
Abstract: The development of metal deposition processes based on electroless nickel, alloy and composite coatings on various surfaces has witnessed a surge in interest among researchers, with many recent applications made possible from many excellent properties. In recent years, these coatings have shown promising corrosion and wear resistance properties and large number of newer developments became most important from macro to nano level applications. After a brief review of the fundamental aspects underlying the coating processes, this paper discusses in detail about different electroless nickel alloy, composite, nano plating, bath techniques, preparation, characterization, new depositing mechanism and their recent applications, including brief notes on difficult substrate and waste treatment for green environment. Emphasis will be onto their recent progress, which will be discussed in detail and critically reviewed.
TL;DR: In this article, the photocatalytic degradation of methylene blue dye was successfully carried under UV irradiation over Fe 2 O 3 /TiO 2 nanoparticles embedded various composition.
Abstract: The photocatalytic degradation of methylene blue dye was successfully carried under UV irradiation over Fe 2 O 3 /TiO 2 nanoparticles embedded various composition of Fe 2 O 3 (0–20) wt.% synthesized by sol–gel process. Structural and textural features of the mixed oxide samples were investigated by X-ray diffraction [XRD], Fourier transformer infra-red [FTIR], Energy dispersive X-ray [EDX], Field emission electron microscope [FESEM] and transmission electron microscope [TEM]. However, the optical features were estimated using UV–Vis spectrophotometer. The results reveal that the incorporation of various Fe 2 O 3 up to 7% is associated by remarkable increase in surface area, reduction of particle size, stabilization of anatase phase, shifting the photoexcitation response of the sample to visible region and exceptional degradation of methylene blue dye. On the other hand, increasing Fe 2 O 3 contents up to 20 wt.% is associated by anatase–rutile transformation, increasing in particle size and remarkable decrease in surface area which are prime factors in reducing the degradation process. The experimental results indicate that Fe 2 O 3 /TiO 2 nanoparticles having both the advantages of photodegradation–adsorption process which considered a promising new photocatalysts that involve in the abatement of various organic pollutants.
TL;DR: In this paper, the microstructure and corrosion resistance property of AlCrFeCuCo high-entropy alloy were researched by scanning electron microscopy, X-ray diffraction and electrochemical workstation.
Abstract: The AlCrFeCuCo high-entropy alloys were prepared by the laser cladding method. The microstructure and corrosion resistance property of AlCrFeCuCo high-entropy alloy were researched by scanning electron microscopy, X-ray diffraction and electrochemical workstation. The results show that, under the rapid solidification small microstructure gained, the morphology of AlCrFeCuCo high entropy alloy is simple, the phase mainly compose of FCC and BCC; elements segregated in the alloys; the alloy shows excellent corrosion resistance, along with the increase of the scanning speed, alloy corrosion resistance performance shows a enhancement in the first and then weakened trend. The corrosion resistance performance of AlCrFeCuCo high-entropy alloys in 1 mol/L NaCl solution is better than in 0.5 mol/L H2SO4 solution.
TL;DR: In this article, a quaternary Heusler half-metallic ferromagnets CoFeCrZ was designed and its first-principles calculations showed that, within a generalized gradient approximation for the electronic exchange correlation functional, both CoFeFeCrGa and CoFeGe are nearly halfmetals.
Abstract: The high Curie temperatures and compatible lattice structure with conventional semiconductors for half-metallic Co 2 FeZ and Co 2 CrZ (Z = Al, Si, Ga, Ge) inspired us to design new quaternary Heusler half-metallic ferromagnets CoFeCrZ. Our first-principles calculations show that, within generalized gradient approximation for the electronic exchange–correlation functional, both CoFeCrGa and CoFeCrGe are nearly half-metals, while both CoFeCrAl and CoFeCrSi exhibit excellent half-metallic ferromagnetism with the large half-metallic gaps of 0.16 and 0.28 eV, respectively. The half-metallicity of CoFeCrAl and CoFeCrSi is robust against the lattice compression (up to 7% and 4%, respectively). We also reveal that the half-metallicity is lost for both CoFeCrAl and CoFeCrGa but retentive for both CoFeCrSi and CoFeCrGe when the Coulomb interactions are considered. In addition, both CoFe- and CrSi-terminated (0 0 1) surfaces with and without antisite defects lose the bulk half-metallicity in CoFeCrSi.
TL;DR: In this article, the electrochemical properties of silicon, tin, tin oxide, iron oxides, cobalt oxides and copper oxides are systematically summarized and the challenges and new directions in developing lithium alloys and metal oxides as commercial anodes for the next-generation lithium-ion batteries are also discussed.
Abstract: Lithium alloys and metal oxides have been widely recognized as the next-generation anode materials for lithium-ion batteries with high energy density and high power density. A variety of lithium alloys and metal oxides have been explored as alternatives to the commercial carbonaceous anodes. The electrochemical characteristics of silicon, tin, tin oxide, iron oxides, cobalt oxides, copper oxides, and so on are systematically summarized. In this review, it is not the scope to retrace the overall studies, but rather to highlight the electrochemical performances, the lithium storage mechanism and the strategies in improving the electrochemical properties of lithium alloys and metal oxides. The challenges and new directions in developing lithium alloys and metal oxides as commercial anodes for the next-generation lithium-ion batteries are also discussed.
TL;DR: In this paper, the high-temperature flow behavior of 7075 aluminum alloy was studied by hot compressive tests and the efficiencies of power dissipation and instability parameter were evaluated.
Abstract: The high-temperature flow behavior of 7075 aluminum alloy was studied by hot compressive tests. Based on the experimental data, the efficiencies of power dissipation and instability parameter were evaluated. Processing maps were constructed by superimposing the instability map over the power dissipation map. Microstructural evolution of 7075 aluminum alloy during the hot compression was analyzed to correlate with the processing maps. It can be found that the flow stresses increase with the increase of strain rate or the decrease of deformation temperature. The high-angle boundaries and coarse precipitations distributing in the grain interior/boundaries, which may result in the deep inter-granular corrosion and large areas of denudation layer, should be avoided in the final products. The optimum hot working domain is the temperature range of 623–723 K and strain rate range of 0.001–0.05 s−1.
TL;DR: In this article, a series of cost effective Co-free AlxCrCuFeNi2 high entropy alloys were developed, following the valence electron concentration rule, and the solidification microstructure in these alloys showed some anomalies that were rarely seen in other high-entropy alloys or multi-component alloys.
Abstract: A series of cost effective Co-free AlxCrCuFeNi2 high entropy alloys were developed, following the valence electron concentration rule. The solidification microstructure in these alloys showed some anomalies that were rarely seen in other high entropy alloys or multi-component alloys. Specifically, submicron rod-like microstructures existed in the eutectic alloy in spite of the high volume percentage of the rod-like phase; sunflower-like microstructures existed in the hyper-eutectic alloys, with 200 nm sized spinodal decomposed seed particles densely distributed in the disk floret. (c) 2013 Elsevier B.V. All rights reserved.
TL;DR: In this paper, the body centered cubic (BCC) phases of the two BCC phases separated with the increase of Mo content while Mo element preferred to dissolve into FeCr-type solid solution.
Abstract: The AlCrFeNiMox (x = 0, 0.2, 0.5, 0.8, 1.0) high entropy alloys were produced by vacuum arc melting, and their microstructure and mechanical properties were investigated. AlCrFeNi, AlCrFeNiMo0.2, and AlCrFeNiMo0.5 alloys contained two body centered cubic (BCC) phases which were AlNi-type intermetallic compound and FeCr-type solid solution. The diffraction peaks of the two BCC phases separated with the increase of Mo content while Mo element preferred to dissolve into FeCr-type solid solution. When the value of x was higher than 0.5, the FeCrMo-type σ phase appeared and replaced the FeCr-type solid solution. The AlCrFeNiMo0.2 had the highest fracture strength of 3222 MPa and plastic strain of 0.287. The hardness increased obviously from HV472.4 to HV911.5 with the addition of Mo element. The solid-solution strengthening of the BCC matrix and the σ phase hardening were the two main factors that strengthened the alloys. The AlCrFeNiMo0.2 high entropy alloy possesses the excellent mechanical properties which imply its potential application in industrial areas.
TL;DR: In this article, the Al2CrFeCoCuTiNix high-entropy alloys were prepared by laser cladding and the results showed that the surface microhardness of Al2crFeCoCcuTiNiNix was increased by 4 times as the substrate hardness with increasing Ni content.
Abstract: The Al2CrFeCoCuTiNix high-entropy alloys were prepared by laser cladding. Using metallurgical microscope, scanning electron microscopy with spectroscopy (SEM/EDS), X-ray diffraction, micro/Vickers hardness tester, electrochemical workstation and tribometer the structure and hardness, corrosion resistance and wear resistance of Al2CrFeCoCuTiNix high-entropy alloys were tested. The result shows that, Al2CrFeCoCuTiNix high-entropy alloy samples consist of the cladding zone, bounding zone and heat affected zone. The bounding zone is between cladding layer and the substrate of a good combination; the cladding zone is composed mainly of axis crystal, nanocrystalline and fine white crystals. The Al2CrFeCoCuTiNix high-entropy alloys coating phase structure samples (FCC and BCC structure) due to high-entropy effect. The surface microhardness of Al2CrFeCoCuTiNix high-entropy alloys samples up to 1102 HV, about 4 times as the substrate, and the hardness increases with increasing Ni content. Al2CrFeCoCuTiNix high-entropy alloys coating has good corrosion resistance in 1 mol/L NaOH solution and 3.5% NaCl solution. With the increase of Ni content, the corrosion resistance first increases and then decreases. The relative wear resistance of Al2CrFeCoCuTiNix high-entropy alloys coating shows a first increased and then a decreased trend with the increase of Ni content. Both the hardness and ductility are affected by wear resistance. The coating can play a good protective role on substrate Q235 steel.
TL;DR: In this article, the authors highlight the broad-spectrum of different nano-composite materials that have been used as electrode material in the MFC in recent years and highlight the benefits of these materials.
Abstract: The microbial fuel cell (MFC) is a very promising technology for generating electrical energy from anaerobic fermentation of organic and inorganic matter in wastewater using microorganisms as biocatalysts while simultaneously treating the wastewater. However, the overall low performance of the MFC compared to other more established fuel cell technologies and the high cost of its components compared to the low value of the wastewater it treated, are the two major barriers to commercialization. In recent years, MFC’s performance has been improved by using among other things, cheaper nano-composite materials such as nano-structured carbon in the electrodes that are more conductive and mechanically stabile with larger surface area and higher electrochemical catalytic activity compared to the conventional Pt on carbon. However, the nano-structured carbon electrodes have also been reported to have some serious drawbacks such as toxicity to the microbial consortium in the biofilm attached on its surface, which reduces performance of the MFC. This paper tries to highlight the broad-spectrum of different nano-composite materials that have been used as electrode material in the MFC in recent years.
TL;DR: Magnetically recyclable ZnFe 2 O 4 /ZnO nanocomposites immobilized on different content of graphene with favorable photocatalytic activity under solar light irradiation were successfully prepared on the basis of an ultrasound aided solution method as discussed by the authors.
Abstract: Magnetically recyclable ZnFe 2 O 4 /ZnO nanocomposites immobilized on different content of graphene with favorable photocatalytic activity under solar light irradiation were successfully prepared on the basis of an ultrasound aided solution method The molar ratio of ZnFe 2 O 4 to ZnO and the content of graphene could be controlled by adjusting the amount of zinc salts and graphene oxide dispersions The most excellent photocatalytic activity under solar light irradiation was displayed when the molar ratio of ZnFe 2 O 4 to ZnO was 01 and the weight ratio of graphene to ZnFe 2 O 4 /ZnO was 004 Furthermore, the presence of magnetical ZnFe 2 O 4 will facilitate the recycling process of photocatalyst nanoparticles
TL;DR: In this paper, the phase structures, surface morphologies, functional groups of molecules, chemical compositions of the surfaces and the binding energies of atoms in the coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and Xray photoelectron spectrography (XPS), respectively.
Abstract: In this study, Ti6Al4V alloy was coated in the solution consisting of calcium acetate (CA) and β-calcium glycerophosphate (β-Ca-GP) by plasma electrolytic oxidation (PEO) to produce hydroxyapatite and calcium apatite-based composite used as of bioactive and biocompatible materials in biomedical applications. The phase structures, surface morphologies, functional groups of molecules, chemical compositions of the surfaces and the binding energies of atoms in the coating were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. Anatase, rutile, calcium oxide, titanium phosphide, whitlockite, tri-calcium phosphate (TCP), perovskite calcium titanate and hydroxyapatite phases on the coating were detected by XRD analysis. The surface of coatings produced by PEO method has a porous structure. The amount of amorphous hydroxyapatite is the highest value for the coating produced at 5 min in XPS and ATR-FTIR results, whereas the amount of crystalline hydroxyapatite has the highest value for coating produced at 120 min in XRD results.
TL;DR: In this article, the effect of adding reduced graphene oxide (RGO) on the micro-structure, electric field-induced strain, and ferroelectric properties of polyvinylidene fluoride (PVDF) was described.
Abstract: This study describes the effect of adding reduced graphene oxide (RGO) on the micro-structure, electric field-induced strain, and ferroelectric properties of polyvinylidene fluoride (PVDF). Nanocomposite film was prepared by simple solution casting of the PVDF/graphene oxide (GO) solution. PVDF/RGO film was produced by in situ thermal reduction of the PVDF/GO film. The effects of GO and RGO on the characteristics of PVDF were examined by scanning electron microscopy, energy dispersive spectroscopy, Fourier transform-infrared spectroscopy, and X-ray diffraction measurements. The electric field-induced strain was markedly enhanced up to Smax/Emax = 16.66 pm/V for 0.3 wt% GO loading. The dielectric constant increased from 16 to 69 at 1 kHz. The polarization–electric field loop exhibited enhanced remnant polarization from 0.8 to 2.5 μC/cm2. Therefore, the PVDF/graphene nanocomposite has adjustable piezoelectric and ferroelectric properties to be used for energy harvesting.
TL;DR: In this article, the microstructure evolution and mechanical properties of hypereutectic Al-20%Si alloy with rare earth cerium (Ce) additions (0, 0.3,0.5, 1.8 and 1.0 ) were investigated.
Abstract: It is well known that the mechanical properties of hypereutectic Al–Si alloys are influenced by the size, morphology and distribution of primary and eutectic Si crystals. In the present work, the microstructure evolution and mechanical properties of hypereutectic Al–20%Si alloy with rare earth cerium (Ce) additions (0, 0.3, 0.5, 0.8 and 1.0 wt.%) were investigated. The as-cast samples were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA) with wavelength dispersive spectroscopic (WDS). The microstructural observation showed that primary Si crystals were significantly refined from coarse polygonal and star-like shape to fine blocky shape with smooth edges and corners, and eutectic Si phases were modified from coarse platelet-like/needle-like structure to fine fibrous structure and discrete particles with increasing the addition contents of rare earth Ce. The mechanical properties were investigated by tensile test with various concentration of Ce. It was found that the ultimate tensile strength (UTS) and elongation (El) increased by 68.2% and 53.1%, respectively, due to decreasing of the size and changing of morphology on primary and eutectic Si crystals.
TL;DR: The influence of calcination temperature on crystallite size, morphology, band gap and luminescence properties of resultant material have been investigated in this paper, where different trends were observed in the phase transformation, particle growth, shift in energy band gap, and in luminecence with the change in tensile strain to compressive strain of the prepared nanomaterial.
Abstract: Pure and mixed phase TiO 2 have been prepared by sol–gel method; calcinated at four different temperatures. The influence of calcination temperature on crystallite size, morphology, band gap and luminescence properties of resultant material have been investigated. Different trends were observed in the phase transformation, particle growth, shift in energy band gap and in luminescence with the change in tensile strain to compressive strain of the prepared TiO 2 nanomaterial. X-ray diffraction (XRD) showed that prepared nanocrystals have pure anatase and anatase-rutile mixed structures. The prepared samples having crystallite size between 19 nm to 68 nm were observed at different calcination temperatures. Williamson-Hall plot results indicate the presence of tensile strain at 400, 500 and 600 °C while compressive strain at 700 °C. Scanning electron microscopy (SEM) shows that the particles are non-uniform. Ultraviolet-Visible spectroscopy (UV-Vis) is used to calculate the energy band gap of materials and it has been observed that the band gap decreases with increase in temperature. Fourier transform infrared spectroscopy (FTIR) describes local environment around TiO 2 nanoparticles. Photoluminescence spectroscopy (PL) exhibits the change in PL intensity with phase change and different trends have been observed in emission edges.
TL;DR: In this paper, a polymer assisted co-precipitation method using polyethylene oxide (PEO) as a capping and a polymer structure directing reagent was successfully synthesized by a single crystalline nickel ferrite (NiFe 2 O 4 ) nanorods.
Abstract: Highly ordered single crystalline nickel ferrite (NiFe 2 O 4 ) nanorods have been successfully synthesized by a polymer assisted co-precipitation method using polyethylene oxide (PEO) as a capping and a polymer structure directing reagent. In this synthesis, the addition of high concentration of PEO seems to play an important role in the formation, size and shape control of the nanorods. Powder X-ray diffraction (XRD) and selected area electron diffraction (SAED) exhibit that the obtained nanorods can be indexed to single crystalline inverse spinel with Fd3m space group. The synthesized NiFe 2 O 4 products were characterized in terms of their structural and magnetic properties. The morphological investigations using high resolution scanning electron microscopy (HRSEM) and transmission electron microscopy (TEM) reveal that the grown products are rod-like structure with the diameters in the range of 60–65 nm and length of 142–147 nm. The coercivity of prepared nanorods with high concentration of PEO reached as high as 904.46 Oe at room temperature (300 K), superior to that of nanoparticles obtained with low concentration of PEO. Hence, it can be used for high frequency electronics and gas sensing applications. On the basis of these experimental results, possible influence mechanisms in the growth processes are discussed.
TL;DR: In this paper, a comparative evaluation of as-cast Sn-Bi, Sn-Ag and Sn-Zn alloys as a function of the resulting microstructural arrays with a view to application as solder materials is presented.
Abstract: The aim of this paper is to develop a comparative evaluation of mechanical properties of as-cast Sn–Bi, Sn–Ag and Sn–Zn alloys as a function of the resulting microstructural arrays with a view to application as solder materials. The resulting microstructures, ultimate and yield tensile strengths and elongations of Sn–40 wt.% Bi, Sn–3.5 wt.% Ag and Sn–9 wt.% Zn alloys were examined and compared with the corresponding results of the traditional Sn–40 wt.% Pb solder alloy. Tensile tests were carried out using specimens selected from specific positions along the length of the directionally solidified castings and Hall–Petch type correlations have been proposed relating the resulting tensile properties of each alloy to a parametric scale of the microstructure. It was found that all Pb-free alloys examined comply with a compromise between compatible mechanical strength and environmental protection. The Sn–Bi alloy has the highest ultimate tensile strength of all alloys examined, while both Sn–Ag and Sn–Zn alloys are lighter and exhibited higher ductility than the Sn–Pb and Sn–Bi alloys.
TL;DR: In this paper, the size of ZnO nanoparticles was investigated and the effects of process parameters such as the molar ratio, pH of reactants and calcination temperatures on the size was investigated.
Abstract: This article describes the controlled size of ZnO nanoparticles when they are synthesized using the sol–gel method without the involvement of a capping agent. The effects of process parameters such as the molar ratio, pH of reactants and calcination temperatures on the size of the synthesized ZnO nanoparticles were investigated. The hexagonal wurtzite phase structure of ZnO nanoparticles was obtained in the form of spherical shapes for all samples. It was found that the ZnO nanoparticles were small in size and experienced reduced agglomeration at a 1:2 molar ratio of the starting material and pH of 2.0 ± 0.2. The results showed that the ZnO nanoparticles had increased in size and experienced a larger agglomeration when the ratio and pH were at higher or lower than the optimal condition. The morphological observations showed increase in particle size when the calcination temperature was increased. The functional group for the ZnO nanoparticle showed a peak in the range of 494–500 cm−1. The optical properties of the ZnO nanoparticles with the best band gap of 3.19 eV were also evaluated under the optimal experimental conditions. The surface charge of the ZnO nanoparticles did not change, which indicated that there was no relationship between surface charge and particle size for the same type of catalyst.
TL;DR: In this article, a polycarbosilane precursor was successfully fabricated by pyrolysis of poly carbide precursors and free carbon nanodomains and the direct-current electrical conductivity, dielectric and microwave absorption properties over the frequency range of 8.2-12.4 GHz (X band) were investigated.
Abstract: Porous silicon carbide ceramics were successfully fabricated by pyrolysis of a polycarbosilane precursor. The direct-current electrical conductivity, dielectric and microwave absorption properties over the frequency range of 8.2–12.4 GHz (X band) were investigated. Polymer derived silicon carbide is composed of SiC nano-crystals and free carbon nanodomains. The high-temperature direct-current conductivities of samples indicate the transformation of amorphous semiconductor into polycrystalline semiconductor with the increase of the annealing temperature. After annealed at 1500 °C, the real permittivity, imaginary permittivity and the loss tangent increase from 3.6, 0.17 and 0.05 to 8.49, 10.01 and 1.18, respectively. The increases of the relative complex permittivity and loss tangent are ascribed to the appearance of SiC nano-crystals and free carbon nanodomains. The average reflectivity of the polymer derived SiC ceramics annealed at 1400 °C is −9.9 dB, which exhibits a promising prospect as microwave absorbing materials.
TL;DR: In this paper, structural studies suggested a transition in phase from tetragonal to cubic symmetry with increase in Lanthanum content and Rietveld Refinement technique employed for investigation confirmed the same.
Abstract: Ba 1− x La 2 x /3 TiO 3 (0.00 ⩽ x ⩽ 0.10, in a step of 0.02) ceramics have been prepared through solid state reaction route. Structural studies suggested a transition in phase from tetragonal to cubic symmetry with increase in Lanthanum content. Rietveld Refinement technique employed for investigation confirmed the same. Photoluminescence study revealed introduction of structural disorder by means of A-site vacancies and displacement of M–O bond leading to shallow defects. Optical band gap value calculated from UV–Vis spectra decreased with increase in La concentration. A drastic decrease in grain size of undoped BT was observed with introduction of La through Scanning Electron Micrographs. Dielectric studies were performed and a gradual decrease in the Curie temperature with increase in La content in coherence with structural studies was observed along with pinching effect. Normal ferroelectric character was obtained for the composition x = 0.00 to x = 0.06 while relaxor like behavior was observed for composition x ⩾ 0.08. The composition x = 0.10 made a good Vogel–Fulcher fit. Inhomogeneity induced in the BT lattice due to 8% La doping is strong enough to make an onset of such behavior. P ∼ E hysteresis loop showed a regular decrease in remnant polarization and coercive field featuring similar relaxor like behavior.
TL;DR: In this paper, the structural evolution in high-energy cryogenically alloyed nanocrystalline Cu-Ta alloys was investigated and it was found that the onset of grain growth occurs at temperatures higher than that for pure nano-coarse Cu.%Ta.
Abstract: Nanocrystalline Cu–Ta alloys belong to an emerging class of immiscible materials with potential for high-temperature applications. Differential scanning calorimetry (DSC), Vickers microhardness, transmission and scanning electron microscopy (TEM/SEM), and atomistic simulations have been applied to study the structural evolution in high-energy cryogenically alloyed nanocrystalline Cu–10 at.%Ta. The thermally induced coarsening of the as-milled microstructure was investigated and it was found that the onset of grain growth occurs at temperatures higher than that for pure nanocrystalline Cu. The total heat release associated with grain growth was 0.553 kJ/mol. Interestingly, nanocrystalline Cu–10 at.%Ta maintains a mean grain size (GS) of 167 nm after annealing at 97% of its melting point. The increased microstructural stability is attributed to a combination of thermodynamic and kinetic stabilization effects which, in turn, appear to be controlled by segregation and diffusion of Ta solute atoms along grain boundaries (GBs). The as-milled nanocrystalline Cu–10 at.%Ta exhibits Vickers microhardness values near 5 GPa surpassing the microhardness of conventional pure nanocrystalline Cu by ∼2.5 GPa.
TL;DR: In this article, the authors used ethanol/water mixtures with varied volume ratios from 0:1 to 1:0 in a facile hydrothermal process with CeCl 3 ⋅7H 2 O as cerium source and N 2 H 4 ⋆H 2O as mineralizer to control the morphology change from thin nanorod to short-thick nanorods, and then to nanoparticles.
Abstract: Morphology control of CeO 2 nanostructures was achieved by using ethanol/water mixtures with varied volume ratios from 0:1 to 1:0 in a facile hydrothermal process with CeCl 3 ⋅7H 2 O as cerium source and N 2 H 4 ⋅H 2 O as mineralizer. It was found that the increase of ethanol/water ratio resulted in the morphology change from thin nanorods to short-thick nanorods, and then to nanoparticles, which is mainly attributed to the influences of hydrocarbon chains, dielectric constant, and viscosity of the solution on the thermodynamics of the reaction system and kinetics of nucleation. Various characterization techniques have been used to study the CeO 2 nanostructures, including XRD, XPS, SEM, HRTEM, Raman, and PL spectra. Photoluminescence spectra of the CeO 2 nanoparticals exhibited an unique UV–violet–blue emission which is likely associated with the defect states existing extensively between Ce 4f and O 2p bands, better crystallinity of the sample, and higher concentration of Ce 3+ ions in sample.
TL;DR: In this article, the deformation behavior of a hypoeutectic Ti-6Al-4V-0.1B alloy in (α + β) phase field is investigated with special reference to flow response, kinetics and microstructural evolution.
Abstract: Hot deformation behavior of a hypoeutectic Ti–6Al–4V–0.1B alloy in (α + β) phase field is investigated in the present study with special reference to flow response, kinetics and microstructural evolution. For a comparison, the base alloy Ti–6Al–4V was also studied under identical conditions. Dynamic recovery of α phase occurs at low temperatures while softening due to globularization and/or dynamic recrystallization dominates at high temperatures irrespective of boron addition. Microstructural features for both the alloys display bending and kinking of α lamellae for near α test temperatures. Unlike Ti–6Al–4V, no sign of instability formation was observed in Ti–6Al–4V–0.1B for any deformation condition except for cavitation around TiB particles, due to deformation incompatibility and strain accumulation at the particle–matrix interface. The absence of macroscopic instabilities and early initiation of softening mechanisms as a result of boron addition has been attributed to microstructural features (e.g. refined prior β grain and α colony size, absence of grain boundary α layer, presence of TiB particles at prior β boundaries, etc.) of the respective alloys prior to deformation.
TL;DR: In this paper, the authors investigated the concentration dependent spectroscopic properties of Sm 3+ ions in the prepared x Sm:PbFB lead fluorobororate glasses with the composition (40−− x )B 2 O 3 −+20PbO+16PbF 2 ǫ+12Bi 2 O −+12ZnO+x Sm 2 O ¼
Abstract: Concentration dependent spectroscopic properties of Sm 3+ ions are investigated in the prepared x Sm:PbFB lead fluorobororate glasses with the composition (40 − x )B 2 O 3 + 20PbO + 16PbF 2 + 12Bi 2 O 3 + 12ZnO + x Sm 2 O 3 (where x = 0.05, 0.1, 0.5, 1, 2 and 3 wt.%). Surface morphological analysis and structural behaviors of the prepared glasses have been explored through SEM, EDX, XRD, FTIR and Raman spectral analysis. The amorphous nature of the prepared glasses have been confirmed through XRD spectral analysis. The presence of BO 3 , BO 4 , B–O–B and Pb/Bi–O–B vibrational stretching units in the prepared glasses are confirmed through FTIR and Raman spectral analysis. The optical characterizations were carried out using UV–vis–NIR absorption, luminescence spectra and decay curves of the present glasses. The calculated bonding parameter ( β ¯ and δ ) values reveal the ionic nature of the Sm–O bond in the prepared glasses. The Judd–Ofelt intensity parameters, Ω λ , were evaluated from the measured oscillator strength of the various absorption bands to study the bonding environment around the Sm 3+ ions in the prepared glasses. From the JO intensity parameters and emission spectral measurements, the radiative properties such as stimulated emission cross-section ( σ P E ) , branching ratio ( β R ) and radiative lifetime ( τ R ) for the 6 H J =5,7,9,11 emission transitions have been calculated. The experimental lifetime for the excited 4 G 5/2 level of the Sm 3+ ions in the prepared glasses were calculated from the decay analysis and it is found to decrease with the increase in Sm 3+ ion content. The decay curves are found to be non-exponential for the higher concentration of Sm 3+ ion which is due to the efficient energy transfer between Sm 3+ –Sm 3+ ions. To understand the nature of the energy transfer, the non-exponential decay rates were fitted to Inokuti–Hirayama (IH) model for S = 6 which reveals that the energy transfer process is of dipole–dipole in nature. Among the prepared glasses, 0.5SmPbFB glass exhibit higher values of emission characteristic parameters and quantum efficiency for the 4 G 5/2 level suggesting that 0.5SmPbFB glass could be useful for optoelectronic device fabrication and laser applications.
TL;DR: In this article, a N-doped BiVO 4 photocatalyst with high visible light activity was synthesized by the complexing sol-gel method using citric acid as a chelate and hexamethylene tetramine (C 6 H 12 N 4 ) as a nitrogen source.
Abstract: A N-doped BiVO 4 photocatalyst with high visible light activity was synthesized by the complexing sol–gel method using citric acid as a chelate and hexamethylene tetramine (C 6 H 12 N 4 ) as a nitrogen source. The as-prepared N-doped BiVO 4 samples were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface area (BET) and UV–Vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity was evaluated by photocatalytic degradation of methyl orange (MO) solution under visible light. This technique revealed that pure BiVO 4 and all the N-doped samples were in a monoclinic phase; no peaks of any other phases or impurities were detected. Nitrogen atoms were doped into the BiVO 4 lattice and filled the atomic sites of oxygen to form O–Bi–N–V–O bonds, which contributed to the appearance of the more active species V 4+ and oxygen vacancies. The doped nitrogen resulted in a red shift in the absorption edge. However, the N-doping only slightly changed the morphologies and BET special surface areas of the samples. The photocatalytic activity of BiVO 4 significantly depended on the N-doping content and the calcination temperature. The maximum activity was observed for the catalyst obtained via calcination at 500 °C, for which the molar ratio of N to Bi was 0.20. Excess N-doping decreased the light absorption.
TL;DR: In this article, the specific capacitance of Fe2O3-graphene nanocomposite is 226 F/g at a current density of 1 A/g.
Abstract: Fe2O3-graphene nanocomposite with high capacitive properties had been prepared friendly and facilely by hydrothermal method in one-step. The morphology and structure of the obtained material were examined by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscope (TEM) techniques. It was revealed by TEM images that Fe2O3 nanoparticles grow well on the surface of graphene and the formation of Fe2O3 nanoparticles hinders the aggregation of graphene (reduced graphene oxide, namely, RGO). Electrochemical properties of the synthesized materials were characterized by serials of electrochemical measurements in 1 M Na2SO4 electrolyte. Fe2O3-graphene nanocomposite electrode show higher specific capacitance than graphene, indicating an accelerative effect of Fe2O3 and graphene on improving the electrochemical performance of the electrode. The specific capacitance of Fe2O3-graphene nanocomposite is 226 F/g at a current density of 1 A/g. These attractive results indicate it is possible to seek and develop the promising, environmentally benign and commercial electrodes material based on Fe2O3 and graphene. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.
TL;DR: Magnetic ZnFe2O4/graphene composite has been successfully synthesized by a facile one-pot solvothermal method as discussed by the authors, which showed powerful visible-light photocatalytic activity for the degradation of Rhodamine B (RhB), methyl orange (MO), and methylene blue (MB) in the presence of H2O2.
Abstract: Magnetic ZnFe2O4/graphene composite (ZnFe2O4/G) has been successfully synthesized by a facile one-pot solvothermal method. Graphene oxide (GO) was reduced to graphene and the ZnFe2O4 particles were simultaneously grown on the graphene sheets under the conditions generated in the solvothermal system. Importantly, the ZnFe2O4/G composite showed powerful visible-light-photocatalytic activity for the degradation of Rhodamine B (RhB), methyl orange (MO) and methylene blue (MB) in the presence of H2O2. The ZnFe2O4/G composite serves a dual function as the catalyst for photoelectrochemical degradation of dyes and the generator of a strong oxidant hydroxyl radical ( OH) via photoelectrochemical decomposition of H2O2 under visible light irradiation. ZnFe2O4/G composite has excellent magnetic properties, which makes it magnetically recyclable in a suspension system. Therefore, the ZnFe2O4/G magnetic composite may find potential applications in dye water treatment and the degradation of organic dyes.
TL;DR: In this paper, a visible-light-responsive Graphene-Ag/ZnO nanocomposites were fabricated using a facile, one-pot, nontoxic solvothermal process for the photodegradation of organic dyes.
Abstract: Visible-light-responsive Graphene-Ag/ZnO nanocomposites were fabricated using a facile, one-pot, nontoxic solvothermal process for the photodegradation of organic dyes. During the solvothermal process reduction of graphene oxide and loading of Ag-doped ZnO nanoparticles on two-dimensional graphene sheets were achieved. Electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, BET surface area measurements, X-ray photoelectron spectroscopy and powder X-ray diffraction were used to confirm that the Ag-doped ZnO nanoparticles as randomly dispersed and effectively decorated on graphene sheets via covalent bonds between Zn and C atoms. Optical properties studied using UV-vis diffuse reflectance spectroscopy confirmed that the absorption edge of Ag-doped ZnO shifted to visible-light region with the incorporation of graphene. The as-synthesized Graphene-Ag/ZnO nanocomposites showed unprecedented photodecomposition efficiency compared to the Ag-doped ZnO, pristine ZnO and commercial ZnO under visible-light. The textile mill effluent containing organic substances was also treated using photocatalysis and the reduction in the chemical oxygen demand (COD) of the treated effluent revealed a complete destruction of the organic molecules along with colour removal. This dramatically enhanced photoactivity of the composite which is attributed to retarded charge recombination rate, great adsorption of dyes, enhanced visible light absorption and fast transfer processes. This research has the potential to provide new avenues for the in situ fabrication of the Graphene-Ag/ZnO composites as highly efficient photocatalysts. Â© 2013 Elsevier B.V. All rights reserved.
TL;DR: In this article, the influence of the annealing process on the magnetic properties of soft magnetic composite (SMC) materials with alumina insulator coating was investigated, and the results of energy dispersive X-ray spectroscopy (EDS), XRD, Fourier transform infrared spectrograph (FTIR), and density measurements showed that the iron powders were uniformly coated by a thin layer of alumina coating with high thermal stability.
Abstract: In this study, influences of the annealing process on the magnetic properties of new soft magnetic composite (SMC) materials with alumina insulator coating were investigated. Iron powders were coated with alumina by the sol–gel process at room temperature. The results of energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and density measurements showed that the iron powders were uniformly coated by a thin layer of alumina coating with high thermal stability. Magnetic measurements indicated that the annealing treatment increased the permeability of the composites at low and medium frequency ranges. It was shown that the annealed composites exhibited noticeably higher frequency stability of the magnetic permeability compared to the heat treated pure iron compacts at the same annealing temperature. The results of the loss separation implied that the heat treatment suppressed the hysteresis loss coefficient while it increased the eddy current loss coefficient of the SMCs. The annealed SMCs showed a lower eddy current loss and higher hysteresis loss coefficients compared to the relaxed pure iron compacts due to the preservation of the alumina coating after heat treatment.
TL;DR: In this paper, the compressive and plateau strength of aluminum alloy A356 filled with silicon carbide hollow spheres (SiC HS) was investigated for quasi-static (10 −3 ǫs −1 ) and high strain rate (up to 1520 Ãµ s − 1 ) compressive properties.
Abstract: Aluminum alloy A356 filled with silicon carbide hollow spheres (SiC HS ) is investigated for quasi-static (10 −3 s −1 ) and high strain rate (up to 1520 s −1 ) compressive properties. Such closed cell composite foams, called syntactic foams, are of interest in weight sensitive structural applications. The present work is focused on understanding the compressive failure mechanism and relating them with the material microstructure. The compressive and plateau strengths of syntactic foams with SiC HS are found to be 163 and 110 MPa, respectively. The measured properties are considerably higher than the existing fly ash cenosphere filled aluminum matrix syntactic foams. Compressive failure mechanisms are studied for A356/SiC HS syntactic foams and direct evidence of hollow sphere crushing at the end of the elastic regions is obtained. The predictions of compressive strength obtained from an existing model are validated with the experimental results. Extensive analysis of data on open and closed cell foams containing gas porosity and syntactic foams is presented. A clear advantage in terms of low density and high yield strength is observed in A356/SiC HS syntactic foams compared to other foams. Yield strength of aluminum foams may be different at high strain rate compression compared to quasi-static values but most of the foams do not show strong evidence of strain rate sensitivity within the high strain rate regime.