Construction of ternary heterojunction CuS-CdS/TiO2 nanobelts for photocatalytic degradation of gaseous toluene J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-12 Yanjun Xin, Qinghua Chen, Guodong Zhang
The ternary heterojunction CuS-CdS/TiO2 nanobelts (CuS-CdS/TiO2 NBs) were successfully prepared. The CuS-CdS/TiO2 NBs photocatalyst was used for the decomposition of gaseous toluene under simulated solar light irradiation. Results showed that the construction of ternary heterojunction CuS-CdS/TiO2 NBs improved the photocatalytic activity. The coupling of CuS-CdS heterojunction with TiO2 NBs promoted the absorbance in visible light region. CdS and CuS were brought in contact as a cascade structure, forming the stepwise energy level structure, which leads to the increased separation and transfer of photogenerated electrons and holes. The results demonstrated that photocatalytic degradation rate increased with increasing photocatalyst area from 16 to 40 cm2. With an increase in initial concentration, the decomposition of toluene showed a tendency to increase, however, there was an optimum concentration at 4215 ppm. The optimal flow rate and reaction temperature were around 1.5 L/min and 40 °C, respectively. After illumination of 100 min the conversion of toluene was about 88.12% and the produced CO2 was about 9353 ppm, corresponding to a mineralization ratio of 31.70%. It is hoped that our work could provide a valuable evidence for directing the rationally fabrication of ternary nanojunctions photocatalysts for environment cleanup.
Platelet precipitate in an age-hardening Mg-Zn-Gd alloy J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-12 T. Koizumi, M. Egami, K. Yamashita, E. Abe
The structure of a unique platelet precipitate with a three close-packed layer thickness, which occurred in a Mg-1at.%Zn-2at.%Gd alloy aged at low temperatures (<∼500 K), has been determined based on scanning transmission electron microscopy and first principles calculations. The platelet precipitate is constructed by well-defined Gd networks that cause significant atomic displacements in the adjacent close-packed layer, in which the atomic sites are preferentially occupied by Zn atoms. Local Zn concentrations at the reconstructed-layer have been successfully tuned according to a similar manner of Vegard's law by reference to the local Gd-Gd interatomic distance along the c-axis. Therefore, the present platelet precipitate is found to be not a simple ordered hexagonal-close-packed Mg-Gd as previously reported, but a reconstructed ternary Mg-Zn-Gd structure.
Nanoscale serration and creep characteristics of Al0.5CoCrCuFeNi high-entropy alloys J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Shuying Chen, Weidong Li, Xie Xie, Jamieson Brechtl, Bilin Chen, Peizhen Li, Guangfeng Zhao, Fuqian Yang, Junwei Qiao, Karin A. Dahmen, Peter K. Liaw
Nanoindentation tests were performed to investigate the nano-scale plastic deformation in the Al0.5CoCrCuFeNi high entropy alloys at room temperature (RT) and 200 °C, respectively. Serrated plastic flow, manifested as discrete bursts of plasticity on the load-displacement curve, was observed for both temperatures during the loading period, and its behavior and dependence on the temperature was analyzed from both the experimental and theoretical perspectives. The application of a mean-field theory indicated that the displacement bursts exhibited a temperature-dependent power-law distribution, and the universal exponents, κ and λ, were computed to be 1.5 and 0.04, respectively. With the use of the computed universal exponents, a critical annealing temperature for the slip-avalanche size distribution was estimated to be 1120 °C. Creep occurred during the nanoindentation holding period and exhibited very large stress exponent, implying that the dislocation glide-climb is the dominant mechanism. The creep simulations with a two-layer viscoplastic model further revealed that the deformation at a higher temperature (e.g., 200 °C) featured a greater and faster-growing plastic zone underneath the indenter, implying more pronounced dislocation activities.
Co-catalyst-free ZnS-SnS2 porous nanosheets for clean and recyclable photocatalytic H2 generation J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Lijing Wang, Gan Jin, Yanhong Shi, Hao Zhang, Haiming Xie, Bai Yang, Haizhu Sun
Two-dimensional (2D) ZnS-SnS2 porous nanosheets are designed as clean and low cost photocatalysts for water splitting. The composites successfully combine high photoelectron reduction potential of ZnS with the sufficient sunlight harvesting ability of SnS2. Moreover, SnS2 acts as an effective electron transfer medium from ZnS to SnS2 due to the construction of quasi-type II structure. This greatly promotes the transfer of electron-hole pairs and effectively inhibits their recombination. Especially, the unique porous nanosheets structure maintains them high specific surface area and countless reactive sites, which increases the reactants' contact area and facilitates the migration of carriers upon photocatalysis. This further supresses the charge recombination and improves the photocatalysts' stability. As a result, an optimized specific surface area of 246.7 m2 g−1 and photocatalytic H2 generation rate of 536 μmol h−1 g−1 are achieved in the absence of a surfactant and co-catalyst, which is 10 times higher than ZnS and 17 times higher than SnS2. In addition, the porous nanosheets have fairly good photocatalytic stability and can be reused at least five cycles without obvious changes in activity and structure. This work successfully presents the potential of ZnS and SnS2-based photocatalyst for clean and low cost hydrogen production from water splitting.
Effectiveness evaluation of molten salt processing and ultrasonic cavitation techniques during the production of aluminium based hybrid nanocomposites - An experimental investigation J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 C. Kannan, R. Ramanujam
The aim of this research work is to evaluate the effectiveness of two processing methods and treatments on the mechanical properties Al 7075 based hybrid nanocomposite. In this study, Al 7075 based hybrid nanocomposites were fabricated through ultrasonic assisted cavitation and molten salt processing methods, which were further subjected to T6 treatment and deep cryogenic treatment. The microstructural observation was carried out on hybrid nanocomposites using optical and scanning electron microscopy. A hybrid nanocomposite produced by molten salt processing with ultrasonic assistance and optimized mechanical stirring was found to possess superior properties in terms of tensile strength, percentage elongation and hardness over all other samples. Out of these treatments, T6 was found to better enhance the mechanical properties of aluminium alloy and hybrid nanocomposite than deep cryogenic treatment.
Tunable infrared radiation properties of hybrid films co-assembled with semiconductor quantum chips and exfoliated ultra-thin LDH nanosheets J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Gengyao Wei, Qiang He, Tao Zhang, Dongya Yang, Fengxian Qiu, Xuejie Yue, Yuming Zhou
The controllability of glass surface radiation is of great significance on regulating temperature for applications in energy conservation in residential buildings. In this work, nano-scale hybrid films with tunable surface radiation are successfully prepared via layer-by-layer assembly of exfoliated layered double hydroxide (LDH) nanosheets with In2O3 quantum chips covering the surface of glass substrates. In this hybrid system, the ultra-thin LDH nanosheets are exfoliated from hexagonal plate-like particles of Mg-Al-NO3- LDH nanosheets after anion-exchange of Mg-Al-CO32- LDH nanosheets. And In2O3 semiconductor quantum chips are obtained after an annealing treatment from In(OH)3 nanosheets which are prepared in sodium oleate/indium chloride hydrothermal system. The prepared LDH nanosheets and In2O3 quantum chips are assembled layer-by-layer onto glass substrates to form the multilayer films. Morphological and structural evolution of the hybrid films is investigated by X-ray diffraction (XRD) and UV–vis absorption spectra. The characterization results show that the hybrid films exhibit ordered tunable structures, which predicts that the infrared emissivity can be adjusted throughout the infrared spectrum. The surface radiation properties of the hybrid films are studied, and the results show that the number of the layers has a significance influence on the surface radiation properties of the films. Attractively, the hybrid films possess thickness-dependent surface radiation properties with the lowest infrared emissivity of 0.420. The nano-scale hybrid films obtained in this work show great tunability on infrared emission and illustrate to be good candidates for saving energy in the field of energy conservation buildings and smart windows.
Properties of as-deposited and heat-treated Ni-Mn-Ga magnetic shape memory alloy processed by directed energy deposition J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Jakub Toman, Peter Müllner, Markus Chmielus
Ni-Mn-Ga magnetic shape memory alloy was processed by laser metal deposition, an additive manufacturing method. Powder used for deposition was crushed from a cast 10 M martensite Ni-Mn-Ga ingot. The deposited sample was ferromagnetic and showed a 14 M martensite with no detectable macroscopic composition differences throughout, except for a thin layer between substrate and deposit. Layer-by-layer deposition resulted in a layered microstructure due to differences in local thermal histories, and the sample's broad transformation temperature range is proposed to originate from the resulting variations in microstructure. Although the sample is clearly polycrystalline, columnar grains span deposition layers, which is potentially favorable to twin boundary motion. After a homogenizing and ordering heat treatment, transformations regained a typical narrow hysteresis and saturation magnetization increased, while grain growth and/or recrystallization took place. The results show the promise of laser-based additive manufacturing processes for production of magnetic shape memory alloys.
Preparation and electrical properties of a new-type intergrowth bismuth layer-structured (Bi3TiNbO9)1(Bi4Ti3O12)2 ceramics J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Faqiang Zhang, Olivia Wahyudi, Zhifu Liu, Hui Gu, Yongxiang Li
We firstly report an abnormal intergrowth bismuth layer-structured phase, (Bi3TiNbO9)1(Bi4Ti3O12)2, or BTN1BiT2, with non-equal parent blocks. The HRTEM analysis shows that such compound has a long-range-ordered -233- sequence. The crystal structure has been solved in orthorhombic space group A21am with a = 5.458 Å, b = 5.415 Å and c = 91.03 Å. Double dielectric peaks at 668 °C and 760 °C were observed. The thermal stable piezoelectric activity of d33 = 11.6–13.6 pC/N up to 600 °C suggests that the BTN1BiT2 ceramic is a good candidate for piezoelectric device using in high temperature. This work indicates the universality of such abnormal structures and it will obviously expand Aurivillius family for future applications.
Narrow-band red-emitting phosphor, Gd3Zn2Nb3O14:Eu3+ with high color purity for phosphor-converted white light emitting diodes J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 T.S. Sreena, P. Prabhakar Rao, Athira K.V. Raj, T.R. Aju Thara
In this work, we synthesized and characterized a narrow band red emitting Gd3Zn2Nb3O14:Eu3+ phosphor in order to improve the color qualities of warm white light emitting diodes. The phosphors were synthesized via conventional solid state reaction method and investigated the evolution of emission spectra with partial occupation of Zn2+ ions on both A and B site of the fergusonite type structure. The structural and luminescence property analysis corroborates the occupancy of Eu3+ ions in the Gd3+/Zn2+ ion site (A site). The developed phosphor exhibits a strong red emission peaking at 613 nm with a fwhm of merely ∼3.50 nm under the 392 nm excitation. These compounds produce narrow emissions in the visible red spectral regions that are highly professed by human eye and lead to outstanding chromatic saturation of the red spectra. The enhanced electric dipole transition intensity arises from the symmetry distortion of Eu3+ ions caused by the introduction of Zn2+ ions in the lattice. The distortion of the A site symmetry and the red shift of the charge transfer energy leads to an intense 5D0 – 7F2 hypersensitive electric dipole transition under 392 nm excitation. The relative emission intensity was found to be maximum at x = 0.40 and is 3.9 times higher than that of the commercial red phosphor under the 392 nm excitation. These phosphors with remarkable CIE chromaticity coordinates (0.64, 0.35), good CCT values along with high color purity (94.2%) might have significant applications in display devices and evidence as an efficient red phosphor.
Microstructure, microsegregation and nanohardness of CMT clad layers of Ni-base alloy on 16Mo3 steel J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Monika Solecka, Agnieszka Kopia, Agnieszka Radziszewska, Bogdan Rutkowski
Microstructure and properties of Inconel 625 coatings deposited by the Cold Metal Transfer technique on a 16Mo3 boiler tube were investigated. The clad layers were shown to have a typical cellular-dendritic structure with secondary phases in the interdendritic regions (e.g. Laves phases and complex nitrides/carbides (MX)). Nanohardness of the interdendritic regions was higher than of the ɣ matrix dendritic regions. Energy dispersive X-ray spectroscopy analysis revealed microsegregation of Ni, Cr, Fe to the dendritic regions, as well as interdendritic segregation of Nb and Mo. Based on the phase identifications performed, a new solidification path is proposed.
Luminescence of Er3+ doped oxyfluoride phosphate glasses and glass-ceramics J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 A. Nommeots-Nomm, N.G. Boetti, T. Salminen, J. Massera, M. Hokka, L. Petit
Glasses with the composition (75 NaPO3-(25-x) CaO-xCaF2) (in mol %) were prepared with 0.15 mol% of Er2O3. The effect of the glass composition and of heat treatment on the spectroscopic properties of the newly developed glasses is reported. With the progressive replacement of CaO by CaF2, the Er3+:4I13/2 lifetime and the intensity of the upconversion emission increase whereas the intensity of the emission at 1.5 μm decreases due to the decrease in the phonon energy in the as-prepared glasses. The glasses were heat treated at 20 °C above their respective glass transition temperature for 17 h to form nuclei and then at their crystallization temperature from 15min to 1 h to grow the nuclei into crystals. The heat treatment leads to the precipitation of crystalline phases, the composition of which depends upon the glass composition. As the Er3+:4I13/2 lifetime increases and the intensity of the upconversion increases for the glass with x = 0 after heat treatment, the Er3+ ions are expected to be incorporated into the phosphate-based crystals. However, as the shape of the emission band at 1.5 μm remains unchanged and as the intensity of the upconversion decreases significantly after heat treatment of the glasses with x > 10, the crystals found in the glass-ceramics with x > 10 are thought to free of Er3+ ions. Although Er3+ ions entered in the CaF2 crystals precipitating in aluminosilicate glass, the Er3+ ions are believed to remain in the amorphous phosphate part of the glass-ceramic containing CaF2 crystals.
Burgeoning tool of biomedical applications - Superparamagnetic nanoparticles J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Lavanya Khanna, N.K. Verma, S.K. Tripathi
This review offers a hierarchical preview of the emergence of magnetic nanoparticles (MNPs) and their composites in the biomedical field providing an insight into their essential features. The need for coating their surfaces with stabilizers such as polyethylene glycol (PEG) and silica has also been explained. This is required for reducing their agglomeration and appropriate functionalization for final application. A magnetic material for such an application is required to be nanosized, superparamagnetic and biocompatible; all these requisites have been well discussed. Various research conducted on magnetic materials as maghemite, magnetite and ferrite based nanoparticles of Ni, Co, Mn, Zn, Ca and K have been described in detail, along with their composites such as PEG and silica. Folic acid conjugation is done on the coated MNPs as folate receptors are over-expressed on the tumor cells; this makes their targeting efficiency better and precise. In addition, various challenges associated with magnetic nanoparticles/nanocomposites such as nanoparticle-biomolecule interface, drug loading, drug release properties, blood barrier etc., which inhibit their desired role, have also been described.
Protein-based carbon and platinum nanocomposites as electrocatalysts for methanol oxidation activity J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Young-Geun Lee, Geon-Hyoung An, Hyo-Jin Ahn
Owing to the characteristics of high energy density, low operating temperature, and environmentally-friendly features, direct methanol fuel cells (DMFCs) are a promising renewable energy source. However, the electrocatalysts of the anode are vulnerable in terms of their electrochemical performance, as they can be easily toxified by CO and other hydrocarbons, which might lead to a break-up of the methanol oxidation reaction (MOR). For further advances in the DMFC industry with improved electrochemical performance, this issue should be urgently resolved. Thus, this study proposes a novel approach to synthesize protein-based carbon as platinum electrocatalyst supports (PCPs) from tofu using a carbonization for the improved methanol oxidation activities. Among commercial Pt/C and other samples, the composite loaded 10 wt% Pt electrocatalyst showed the highest anodic current density of 510 mA mgPt−1, the excellent electrocatalytic stability, and the highest retention of 86%. The improved electrochemical performances can be attributed to the good dispersion of Pt electrocatalysts and N-doping effect of protein-based carbon supports. These results suggest that PCPs derived from tofu will be one of promising candidates as platinum catalyst supports to improve methanol oxidation activities.
Room temperature antiferromagnetic ordering in chemically prepared nanocrystalline Co-doped neodymium oxide (Nd1.90Co0.10O3-δ) J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 B.J. Sarkar, M. Dalal, A. Mitra, J. Mandal, A. Bandyopadhyay, P.K. Chakrabarti
Nanocrystalline sample of Co-doped neodymium oxide (Nd1.90Co0.10O3-δ, NCO) is prepared by co-precipitation method. Rietveld analysis of the X-ray diffractograms confirms the formation of desired phase and complete substitution of Co-ions in Nd2O3 lattice. Analyses of transmission electron microscopy and the Raman spectra of NCO recorded at room temperature also substantiate this fact. Magnetization (M) as a function of temperature (T) and magnetic field (H) data shows that antiferromagnetic (AFM) ordering is introduced in the sample at room temperature and below ∼ 100 K, a transition from AFM to ferromagnetic (FM) phase is observed. Susceptibility vs. temperature (χ-T) curve in the temperature range of 300–100 K is successfully fitted by Johnston formula which indicates the coexistence of AFM and paramagnetic (PM) phase and below 100 K, the M-T curve is well fitted by a combined equation generated from three dimensional (3D) spin wave model and Curie-Weiss law which confirms the presence of mixed state of FM and PM phases. Oxygen vacancy mediated ferromagnetism plays an important role behind the onset of FM phase.
Effect of hot extrusion on microstructural evolution and tensile properties of Al-15%Mg2Si-xGd in-situ composites J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Hamidreza Ghandvar, Mohd Hasbullah Idris, Norhayati Ahmad
This study investigates the effect of hot extrusion on microstructure and tensile properties of Al–15 wt %Mg2Si in-situ composite in unmodified and modified with (0.5–5.0 wt %) Gd addition. Furthermore, the morphology evolution of primary and eutectic Mg2Si particles in both unmodified and modified with 1.0 wt % Gd prepared by hot extrusion were examined in detail. The results showed that hot-extrusion process was efficient in transforming truncated octahedral primary and rod-like eutectic Mg2Si particles into near spherical and dot-like morphology, respectively in the modified alloy in which the particle fragmentation and thermal disintegration are the main mechanisms responsible for refinement/modification of primary and eutectic Mg2Si particles. It was suggested that the alteration of Mg2Si particles as well as fragmentation of Gd intermetallic compounds (IMCs) by hot extrusion played a significant role in strengthening the composite, i.e., the ultimate tensile strength (UTS) and elongation (%) values increased from ∼224.62 MPa to 3.75% in the 1.0 wt % modified composite to ∼245.83 MPa and 7.65% in the extruded modified one, respectively. In fact, a higher fracture stress can be established by fine near spherical primary Mg2Si particles through impeding dislocation motions and freeing stress concentrations. Furthermore, fragmentation of eutectic Mg2Si and Gd (IMCs) after extrusion lead to enhancement in ductility. This study demonstrated that combination of Gd addition and hot extrusion is a promising approach in modifying the microstructure and enhancing the tensile properties of in-situ Al-15%Mg2Si composite for industrial applications.
Experimental determination of interaction coefficients of components in ternary Si-Fe-Al alloy solution J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Yeqiang Zhou, Jijun Wu, Wenhui Ma, Yun Lei, Yongnian Dai
The “same activity” method was used to determine the activity interaction coefficient of Al to Fe in a Si-based solution. Al was dissolved into a binary Si-Fe solution at 1663, 1673, 1693 and 1723 K. The solubility of Fe and Al in silicon was determined at different temperatures, and the interaction coefficients of Al to Fe were calculated and obtained by fitting the solubility data of Al and Fe. Scanning Electron Microscopy-Energy Dispersive Spectrometer (SEM-EDS) and Electron Probe Micro Analyzer (EPMA) techniques were used to verify the uniformity of the Si-Fe-Al alloy samples and the reliability of the interaction coefficient obtained by experiments at 1693 and 1723 K. The X-ray Powder Diffraction (XRD) results displayed the phase transformation from FeAl3Si2 to FeAl2.7Si2.3 to Fe3Al0.3Si0.7 with rising dissolution temperature, and crystallographic data of the phases were obtained by Rietveld refinements.
Synthesis and characterization of superconducting FeSe nanowires J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 You-Rong Tao, Lei Fan, Zhong-Yu Wu, Xing-Cai Wu, Zhi-He Wang
Iron selenide (FeSe) nanowires have been synthesized on the large-scale by a facile surface-assisted vapor-solid reaction. The typical nanowires prepared with Fe foil/Se molar ratio of 1: 0.1 at 550 °C for 12 h have a width of ∼32 nm, a thickness of ∼5 nm, and a length up to 30 μm. The nanowires are indexed as β-FeSe (tetragonal) with trace amounts of α-FeSe (hexagonal) by X-ray diffraction (XRD). High resolution transmission electron microscope of a single nanowire shows intergrowth between β- and α-FeSe. The electric transportation measurements shows that the nanowires are superconductors of Tc0 = 9.2 K (critical temperature of zero resistance). Suitable growth conditions of the nanowires are discussed.
Investigating the properties of bimetallic aluminum-clad copper tubes produced by friction stir welding J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Ahmad Tavassolimanesh, Ali Alavi Nia
Using the Friction Stir Welding (FSW) method and incorporating a new fixture, copper and aluminum tubes were welded in a lap joint configuration, producing bimetallic copper-aluminum tubes with appropriate interdiffusion. Moreover, the effects of welding parameters such as the rotational and traverse speeds on the macro- and microstructure, the hardness profile, and the shear strength of the samples were investigated. The results showed a stronger joint is achieved by increasing the traverse speed from 30 to 60 mm/min and reducing the rotational speed from 1000 to 710 rpm. Furthermore, it was found that the curvature of the tubes and the difference in their physical properties are quite challenging when welding copper and aluminum tubes using this method.
Morphology-controlled synthesis of 3D flower-like NiWO4 microstructure via surfactant-free wet chemical method J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Mohit Kumar, Young Hun Lee, Min Seob Kim, Dong In Jeong, Bong Kyun Kang, Dae Ho Yoon
Three-dimensional (3D) flower-like controllable microstructures of nickel tungsten oxide (NiWO4) were synthesized by using a surfactant free wet chemical method at low temperature (60 °C). The uniform morphologies of NiWO4 were molded by adjusting the temperature, stirring rate, and dosage of hydrazine in aqueous solution. We reported immediate precipitation of the 3D NiWO4 microflowers (MFs) by introducing hydrazine monohydrate (N2H4·H2O). This approach resulted in a better yield and shortened the reaction time. In this work, we investigated the probable mechanism behind the formation of flower-like microstructures. Furthermore, the flower-like microstructure was assessed for its electrochemical properties towards non-enzymatic glucose sensing by addition of 50 μL of a glucose solution (50 μM) in an electrolyte (0.1 M NaOH) using glassy carbon electrode.
Visible-blind quasi-solid-state UV detector based on SnO2-TiO2 nanoheterostructure arrays J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Duo Chen, Lin Wei, Lingpan Meng, Dong Wang, Yanxue Chen, Yufeng Tian, Shishen Yan, Liangmo Mei, Jun Jiao
Self-powered UV detectors have attracted intensive research interest due to their advantages of low cost fabrication, high efficiency and low power consumption. In this paper, high ordered SnO2-TiO2 nanoheterostructure arrays were synthesized using soft chemical methods. A self-powered quasi-solid-state UV detector was constructed using this nanoheterostructure as the photoanode and a polyethylene oxide based quasi-solid-state electrolyte as the hole transfer layer. Because the SnO2-TiO2 core-shell nanoheterojunction simultaneously offers a high electron-hole separation, a low charge recombination and a direct pathway for electron transport, the nanostructured self-powered detector displayed an excellent performance over that based on bare TiO2 nanostructure arrays. A quite high incident photon-to-current conversion efficiency of 55.8% at 340 nm and a fast response time (0.14 s for rise time and 0.06 s for decay time) were observed. That is quite excellent performance for self-powered UV detector. Moreover, the self-powered UV photodetector also shows an excellent spectral selectivity and long-time stability in the air. These excellent photoelectric characteristics will enable significant advancements for next-generation photodetecting applications.
Tailorable thermal expansion and hygroscopic properties of cerium-substituted Y2W3O12 ceramics J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Hongfei Liu, Weikang Sun, Zhiping Zhang, Min Zhou, Xiangdong Meng, Xianghua Zeng
A new series of cerium-substituted Y2W3O12 ceramics were first fabricated with the goal of tailoring the thermal expansion and reducing the hygroscopicity. Influence of cerium substitution on the structure, hygroscopicity and thermal expansion property of Y2W3O12 ceramics were investigated using XRD, FESEM, HRTEM, XPS, TGA and TMA. Results indicate that the Y3+ can partly be substituted by Ce3+ in Y2-xCexW3O12 ceramics and increasing substitution of Y3+ in Y2W3O12 by Ce3+ results in the crystal structure change from orthorhombic to monoclinic. Single-phase Y2-xCexW3O12 ceramics can be synthesized in the range of 0.0 ≤ x ≤ 0.25 with an orthorhombic Y2W3O12-type crystal structure and 1.0 < x ≤ 2.0 with monoclinic Ce2W3O12-type crystal structure, respectively. As the amount of substituted cerium increases, the hygroscopic phenomenon of Y2-xCexW3O12 is significantly promoted, meanwhile the coefficient of thermal expansion gradually decreases. The linear coefficient of thermal expansion of Y2-xCexW3O12 ceramics can be adjusted from −13.094 × 10−6 K−1 to 2.327 × 10−6 K−1 by changing the substituted amount of cerium. Moreover, Y0.25Ce1.75W3O12 does not absorb moisture in air and shows almost zero thermal expansion from 182 °C to 700 °C and its coefficient of thermal expansion is tested to be −0.820 × 10−6 K−1. This low thermal expansion Y0.25Ce1.75W3O12 material may have great potential applications in manufacturing precision device in many fields.
Low temperature sintered magneto-dielectric ferrite ceramics with near net-shape derived from high-energy milled powders J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Zhuohao Xiao, Xinyuan Sun, Hongfang Zhang, Chuanhu Wang, Lie Liu, Zhihong Yang, Tianshu Zhang, Ling Bing Kong
Nanosized Ni0.70Zn0.25Co0.05Fe1.90Mn0.02O4 ferrite ceramics were fabricated from high-energy ball milled powder mixtures with various ratios of Fe2O3/Fe as starting materials, in order to achieve magneto-dielectric materials with near net shape behavior for practical applications. The ferrite ceramics were obtained by sintering the milled powder compacts at 800 °C for 4 h, with a linear expansion of less than 4% as compared to the green pellets. The ceramics had an average grain size of less than 200 nm. The real part of relative permittivity decreases with increasing percentage of Fe2O3 used in the starting mixtures. The sample from the powder mixture with 50% Fe2O3 exhibits promising magneto-dielectric properties at frequencies of up to 90 MHz, which can be used for miniaturization of antennas at very high frequency (VHF) band.
Effect of Na ions in plating baths on coercivity of electroplated Fe-Pt film-magnets J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 T. Yanai, J. Honda, R. Hamamura, H. Yamada, N. Fujita, K. Takashima, M. Nakano, H. Fukunaga
Fe50Pt50 thick-films were electroplated on a Ta substrate using a direct current, and we evaluated the effect of Na ion concentration in plating baths on the magnetic properties of the annealed films. With increasing NaCl content from 2 to 30 g/L, the coercivity of the annealed Fe50Pt50 films increased from 700 kA/m to approximately 900 kA/m. For obtaining further experimental evidence for the increase in the coercivity, we employed trisodium citrate instead of NaCl as an additive in the plating bath. Consequently, as the addition of the trisodium citrate as well as NaCl increased the coercivity, we concluded that a plating bath with high Na ion concentration is effective to obtain the Fe-Pt thick-films with high coercivity.
Impact of morphology and dielectric property on the microwave absorbing performance of MoS2-based materials J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-11 Weidong Zhang, Xue Zhang, Hongjing Wu, Hongxia Yan, Shuhua Qi
Molybdenum disulfide (MoS2), as a significant microwave absorption materials, has been widely reported. However, it is unclear and insufficient about its microwave absorption mechanism. In this work, a series of MoS2-based materials with different morphology, including MoS2 nanosheets (MoS2-NS), hierarchical MoS2 (H-MoS2) microspheres, hollow hierarchical MoS2 (HH-MoS2) microspheres and hydrangea-like MoS2/C (MoS2/C) microspheres, were synthesized via hydrothermal reaction. More importantly, the microwave absorption mechanism and the dielectric properties as well as microwave absorption performance (MAP) were systemically studied. The results indicated that MoS2/C exhibited eminent dielectric properties and MAP, which resulted from the unique structure and component. The minimum reflection loss (RL) value of MoS2/C microspheres/wax with 30 wt% loading is −44.67 dB at the thickness of 1.4 mm, and the corresponding bandwidth with effective attenuation (RL < -10 dB) is up to 3.32 GHz (11.7–15.02 GHz).
Ag nanoparticles promoted LiFePO4F nanospheres cathode with superior cycling stability for lithium-ion batteries J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-10 Yuanyuan Zhang, Tu'an Lv, Ping Gao, Hongbo Shu, Xiukang Yang, Qianqian Liang, Li Liu, Xianyou Wang
Tavorite-like structure LiFePO4F has been recently studied as potential alternative cathode materials for lithium-ion batteries due to its outstanding structural stability, abundant resources and remarkable safety. However, its poor electronic conductivity and lithium-ion diffusion coefficient leads to the unsatisfactory cycling stability and rate capabilities of LiFePO4F. Herein, Ag decorated LiFePO4F nanospheres have been synthesized for the first time via a precipitation method with in-situ reduction of Ag+, simultaneously improving electronic conductivity and lithium-ion diffusion coefficient. The Ag nanoparticles with size of ∼10 nm are in-situ grown on the surface of LiFePO4F nanospheres with impressive electrochemical performance. It delivers a high discharge capacity of 148.7 mAh g−1 (very close to the theoretical capacity of 152 mAh g−1) at 0.1 C. It is worth mentioning that the Ag-decorated LiFePO4F nanospheres reveal superior cycling stability. The initial discharge capacities of Ag-decorated LiFePO4F reaches up to 120.3 mAh·g−1 at 0.5 C, and the capacity retention is as high as 96.1% after 300 cycles, which is remarkable higher than that of pure LiFePO4F nanospheres with initial discharge capacity of 110.2 mAh·g−1 and capacity retention of 83.1% after 300 cycles. Furthermore, the Ag-decorated LiFePO4F displays the average discharge potential loss of only 0.7% which is lower than pure LiFePO4F of 4.7% after 300 cycles, and the corresponding specific energy retention ratio of 95.5% which is higher than that of 80.1%.
Microwave absorption properties of SrxBa3-xCo2Fe24O41 hexaferrites in the range of 0.1–18 GHz J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-10 Dangwei Guo, Wenwen Kong, Juanjuan Feng, Xiling Li, Xiaolong Fan
SrxBa3-xCo2Fe24O41 Z-type hexaferrites have been prepared by the citric acid sol-gel method, and the structural and electromagnetic properties have been investigated in detail. The results showed that single-phase Z-type hexaferrites were observed, and all samples exhibited excellent soft magnetic properties. For the sample with x = 1.5, a high resonant frequency fr = 3.50 GHz and initial permeability μ′ = 2.76 at 100 MHz was obtained. The calculated frequency dependence spectrum of the reflection loss (RL) showed a largest absorbing value of −48.5 dB at 17.6 GHz with a thickness of 5.0 mm. With the increasing thickness t, two local minimum RL values were observed from the RL-t curve. One was −43.6 dB at t = 4.3 mm and the other was −45.8 dB at t = 2.8 mm. The dependence of percentage bandwidth WP on thickness t was studied. As t increasing, WP increased firstly and then slowly decreased, reaching the maximum value of 96.1% at t = 3.3 mm.
Fabrication and electrochemical study of ruthenium-ruthenium oxide/activated carbon nanocomposites for enhanced energy storage J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-10 M. Nur Hossain, Shuai Chen, Aicheng Chen
In this study, nanocomposites consisting of crystalline Ru and RuO2 nanoparticles have been successfully synthesized via a hydrothermal method in the presence of urea followed by calcination. The effect of calcination temperatures on the formation of the Ru and RuO2 nanocomposites are systemically investigated. Our experimental results have shown that the applied annealing temperature of 300 °C facilitated the formation of the nanostructured Ru and RuO2 composite with a large surface area. Further, novel Ru-RuO2 nanoparticle/activated carbon (Ru-RuO2/AC) composites are prepared and tested as an advanced supercapacitor material for energy storage. Our experimental results reveal that the optimized composition of the Ru-RuO2/AC nanocomposite consists of 10 wt.% of Ru-RuO2 and 90 wt.% of AC, and that the specific capacitance of the developed nanocomposite is 1460 F g−1 (in terms of Ru-RuO2) at a current density of a 10 A g−1 in a 0.5 M H2SO4 electrolyte, which is much higher than many other RuO2 based binary composites reported in the literature. In addition, this new Ru-RuO2/AC nanocomposite exhibits a high charging/discharging rate capability and excellent stability. An approximately 94% retention of the initial specific capacitance is achieved over 10,000 cycles at a charging/discharging current density of 50 A g−1.
Structural and magnetic properties, magnetocaloric effect in (La0.7Pr0.3)0.8Sr0.2Mn0.9Ti0.1O3±δ (δ = 0.03, 0.02, −0.03) J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-10 Svetlana Estemirova, Valentin Mitrofanov, Sergey Uporov, Galina Kozhina
Structural and magnetic properties of the compositions (La0.7Pr0.3)0.8Sr0.2Mn0.9Ti0.1O3±δ prepared at different oxygen partial pressures were investigated over a wide temperature range. The temperatures of phase structural transitions were found; their values varied significantly depending on the oxygen index δ. The first structural transition was due to the cooperative Jahn-Teller effect occurred within the orthorhombic system. The second transition occurs at a higher temperature at which the orthorhombic phase transformed into a rhombohedral phase. The temperature of this transition increased with increasingδ and was equal to ∼323 K (δ = +0.03), 353 K (δ = +0.02)and 623 K (δ = −0.03). The temperature dependence of the magnetization evidenced that all compositions exhibited a ferromagnetic to paramagnetic transition at TC = 132–149 K. The transition temperature was found to increase with increasing oxygen content. It was shown that the phase transition from ferromagnetic to paramagnetic state was of the second order. The magnetic entropy change was calculated from the isothermal magnetization curves obtained at different temperatures. A magnetocaloric effect over a wide temperature range in the vicinity of TC with a maximum magnetic entropy change of ∼1 J/kg K and the relative cooling power of 120 J/kg under the applied field of 2 T was found. The relatively large value and broad temperature interval of the magnetocaloric effect make (La0.7Pr0.3)0.8Sr0.2Mn0.9Ti0.1O3compound a promising candidate for magnetic refrigerant.
Design, fabrication and characterization of multi-layer graphene reinforced nanostructured functionally graded cemented carbides J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-10 Jialin Sun, Jun Zhao, Feng Gong, Zuoli Li, Xiuying Ni
Effect of predesigned multi-layer graphene (MLG) gradient on the microstructure as well as mechanical properties of MLG/WC-Co hardmetal has been investigated. Varied organic solvents and surfactants were used to identify the best combination of dispersing medium and dispersant for the dispersion of MLG. Six kinds of designed functionally graded MLG/WC-Co alloys were prepared employing two-step sintering (TSS) method. Results demonstrated that MLG can enhance the densification process and inhibit the grain growth. Meanwhile, MLG with a predesigned gradient opposite the predesigned cobalt gradient can maximally enhance the stability of predesigned cobalt gradient during liquid phase sintering, the generation of residual surface compressive stress and the mechanical properties of MLG/WC-Co composite. The enhancing mechanisms of cobalt gradient stability were systematically discussed by combining theoretical consideration with experimentation.
Diamond powder incorporated oxide layers formed on 6061 Al alloy by plasma electrolytic oxidation J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-10 Quang-Phu Tran, Tsung-Shune Chin, Yu-Cheng Kuo, Chong-Xun Jin, Tran Trung, Chu Van Tuan, Dong Quang Dang
In this study, diamond powder was incorporated into oxide layers formed on 6061 Al alloy by using plasma electrolytic oxidation (PEO) method. Diamond powder, 1.5 μm in average size, was added in an amount of 0, 3, 6 and 9 g/L, respectively, into the electrolyte containing 0.15 M Na2SiO3 and 0.16 M H3BO3. Phases, microstructure and composition of the oxide layers were investigated by XRD, SEM and EDX analyses. Micro-hardness of the coatings was measured using a micro-indenter. Corrosion performance of PEO coatings was evaluated using potentiodynamic polarization in a solution of 3.5% NaCl. Wear resistance was evaluated using a ball-on-disk tribometer. Both XRD and EDX spectra prove the incorporation of diamond into the coating. With increasing content of diamond powder in the electrolyte, analytical results indicate that the thickness, roughness, corrosion and wear resistance of the coatings increase. PEO coatings obtained with an optimum diamond powder content 6 g/L shows the best performance. The best corrosion resistance is 9.70 × 108 Ω cm2, the highest micro-hardness 855 HV, the lowest average friction coefficient 0.29, and showing the least weight and volume losses after wear tests. Performance of the coatings deteriorates when obtained at a higher content of added diamond powder, 9 g/L. This is due to the sudden increase of both porosity and roughness of the coatings. The variation in coating performance is explained based on the evolution of phase, microstructure, micro-hardness, porosity and roughness with the amount of diamond incorporation.
One-pot methanol-mediated solvothermal synthesis of 3D porous Co-doped α-Ni(OH)2/RGO nanosheets as a high-performance pseudo-capacitance electrode J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-10 Lili Zhang, Shanshan Song, Hongyan Shi
An environment-friendly and cost-effective route has been explored to prepare three-dimensional (3D) porous Co-doped α-Ni(OH)2 nanosheets vertically arranged on reduced graphene oxide (RGO) by one-pot methanol-mediated solvothermal synthesis. This process avoids the addition of any precipitating agent and oxidizing agent. Herein, methanol acts as solvent, structure-directing agent and it also can be oxidized to release OH−. In addition, Co doping is considered to be an effective approach to improve the electronic conductivity and electrochemical performance for energy conversion. Thus, experiments using different doping amounts of Co are performed. The different feed molar ratios of Co2+ to Ni2+ are simply controlled, and the ultrathin Co-doped α-Ni(OH)2/RGO nanosheets (Co2+:Ni2+ = 0.5:1) display the best capacitive property. The synthesized Co-doped α-Ni(OH)2/RGO nanosheet electrode exhibits the highest specific capacitance of 2322 F g−1 at current density of 1 A g−1, outstanding rate performance of 1933 F g−1 at 20 A g−1, and excellent lifetime cycle with 87.9% retention level after 1000 cycles at 10 A g−1. Moreover, an asymmetric supercapacitor is successfully manufactured with the Co-doped α-Ni(OH)2/RGO as a positive electrode and activated carbon as a negative electrode. The hybrid device delivers a maximum energy density of 38.9 Wh kg−1 and a maximum power density of 8000 W kg−1. Our supercapacitor exhibits a remarkable cycle stability along with 88.2% specific capacitance retained over 2000 cycles at 5 A g−1. These results may provide useful insights for fabricating high-performance electrode materials for energy storage applications.
Bamboo prepared carbon quantum dots (CQDs) for enhancing Bi3Ti4O12 nanosheets photocatalytic activity J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-10 Tao Wang, Xiqing Liu, Changchang Ma, Zhi Zhu, Yang Liu, Zhi Liu, Maobin Wei, Xiaoxun Zhao, Hongjun Dong, Pengwei Huo, Chunxiang Li, Yongsheng Yan
In this work, a novel, simple, economical and green carbon quantum dots (CQDs) were obtained by hydrothermal method using bamboo as a carbon source at the first time. In order to further the use of such CQDs, we reported the facile fabrication of CQDs/Bi3Ti4O12 (BTO) nanosheets photocatalysts. The experimental results indicated that CQDs were successfully coupled with BTO nanosheets, exhibiting excellent photocatalytic activity than bare BTO. The improved photodegradation efficiency was attributed to the extended light absorption range, and increased separation rate of electron-holes pairs. At last, a possible photocatalytic mechanism was proposed. The design of such CQDs from the creature with semiconductor can be extended to photocatalytic systems.
A review of fundamental aspects, characterization and applications of electrodeposited nanocrystalline iron group metals, Ni-Fe alloy and oxide ceramics reinforced nanocomposite coatings J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-09 Alok Kumar Chaudhari, V.B. Singh
Electrochemical co-deposition of materials offers some unique advantages over competing technologies and therefore occupies special place in science and technology. Ni-Fe alloys are of great commercial interest owing to their interesting mechanical, electrical, magnetic and corrosion resistant properties. In this communication the present state of art on the electrodeposition of iron group metals and specially Ni-Fe alloy and oxide ceramic reinforced nanocomposites is reported along with a brief overview of fundamental principles, techniques and engineering applications of these metal matrix composites (MMCs) which include their ductility, hardness, electrical resistivity, thermal stability, corrosion resistance, soft magnetic and superparamagnetic properties. These properties of the deposits are mainly dependent on their composition, plating parameters and nature, size, content and distribution of the incorporated ceramic particles in the matrix. Potential commercial applications of these coatings have been discussed and attempts have been made to define accurate and predictive correlations with plating parameters.
An investigation into the aging behavior of CoCrMo alloys fabricated by selective laser melting J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-09 Mingkang Zhang, Yongqiang Yang, Changhui Song, Yuchao Bai, Zefeng Xiao
This work aimed to investigate the martensitic transformation and precipitation of CoCrMo alloys fabricated by selective laser melting (SLM) under aging heat treatment. SLM-fabricated CoCrMo alloy was a mixture of γ-phase and ε-phase, and the content of γ-phase was about 70%. The content of ε-phase increased with the aging time. A nearly pure ε-phase was achieved by aging at 900 °C for 10 h in the SLM-fabricated part. After aging treatment for a short-time, the microhardness of the parts decreased comparing to the AS-SLM probably due to the disappearance of the honeycomb precipitates. The EDS results showed that those granular precipitates in SLM900 and SLM750 are M23C6. The content of M23C6 increased with aging time. The M23C6 precipitates and martensitic transformation enhanced the microhardness. Specimens with highest microhardness were obtained by aging at 900 °C for 10 h. This result established the relationship between the heat treatment process, microstructure and microhardness.
Kinetic study of electroless cobalt deposition on WC particles J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-09 L. Guo, X.J. Zhao, L.R. Xiao, C.R. Tang, W.Y. Zhang, X.X. Tu, X.Z. Liu, Y.C. Nie
The cobalt coating with an average thickness of 15–20 nm was uniformly plated on the surface of ultra-fine WC powders by electroless plating in the present work. The effects of electroless plating condition parameters on the deposition rate were studied. It was found that the deposition rate increased with the increase of CoSO4·7H2O content, pH value, complexing agent concentration, and bath temperature, while decreased with the increase of reducing agent (NaH2PO2·H2O) concentration. Furthermore, the cobalt deposition rate empirical equation and activation energy were determined. The results show that the activation energy (Ea) for the electroless cobalt on WC substrates is approximately 54.65 kJ/mol.
Twisted nanocolumns for LIBs via phi-sweep method in ion assisted e –beam deposition J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-09 B.D. Karahan, O.L. Eryilmaz, K. Amine, O. Keles
In this work, twisted nanostructured silicon-copper (with 19%at. copper) thin film is fabricated by glancing angle deposition phi-sweep process of ion beam assisted electron beam evaporation method. The thin film delivers 977 mAh g−1 after 100 cycles, when cycled with 100 mA g−1 rate and performs 280 mAh g−1 at 2.5 A g−1 rate. The morphological and the compositional particularities of the electrode might govern this noticeable cycle performance: Gaps among the nanostructures accommodate large volume changes and provide easy access to lithium ions for reacting with silicon to deliver high capacity. Plus, direct connection of nanostructures to the current collector display short lithium travelling distance promoting lithiation kinetic. Moreover, small intermetallics creating electronic conductive pathways enhance the reversibility of the lithiation. And finally, 5 min ion assisted deposition increases the adhesion of the film while avoiding possible delamination, hence quick failure of the electrode in the early stages of cycling.
Electrochemical study of Monel alloy corrosion in hydrochloric acid solution and pyrrolidine dithiocarboxylate self-assembled monolayers as its corrosion protector J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-09 Mojtaba Bagherzadeh, Fatemeh Jaberinia
Herein, the corrosion behavior of Monel alloy was comprehensively studied in 5% HCl solution. Then self-adsorption of pyrrolidine dithiocarboxylate (PDTC), as a corrosion protector, on Monel surface was investigated. Electrochemical methods, such as CV, LSV and EIS, and surface techniques such as SEM and EDX were used for evaluation of PDTC-SAM on Monel. Obtained results showed the corrosion current density (Jcorr) decreased in 5 orders, the slope of Tafel plots increased, the corrosion potential (Ecorr) shifted to positive values, the corrosion rate (CR) decreased from 2.11 to 0.172 mm/yr, and the PE% as 91.9% was observed after 4 h self-assembling time.
Ferroelectric photovoltaic properties of perovskite Na0.5Bi0.5FeO3-based solution-processed solar cells J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-09 Xiaoyan Wu, Zhiyang Wan, Juanjuan Qi, Mingtai Wang
Ferroelectric photovoltaic oxides have attracted extensive attention for low-cost solar cells owing to high structure stability and abundant resources. In this paper, we report new perovskite ferroelectric material Na0.5Bi0.5FeO3 featuring low band gap derived from oxygen vacancies induced by high content Na substitute in A-sites. Solution-processed heterojunction solar cells based on Na0.5Bi0.5FeO3 film with Spiro-OMeTAD as the hole transporter is fabricated, of which photovoltaic properties is found to be significantly improved by pre-polarization treatment. It is demonstrated that the photovoltaic properties of Na0.5Bi0.5FeO3 solar cell are affected by both charge transport dynamic and interfacial charge recombination tuned by ferroelectric polarization.
Ag, B, and Eu tri-modified BiVO4 photocatalysts with enhanced photocatalytic performance under visible-light irradiation J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Min Wang, Jin Han, Chunmei Lv, Yu Zhang, Meiyan You, Tingyu Liu, Songli Li, Tong Zhu
To enhance the photocatalytic performance of a bismuth vanadate (BiVO4) photocatalyst, Ag, B, and Eu tri-modified BiVO4 (ABE-BVO) photocatalysts were successfully prepared through an ethylene glycol sol-gel process and photodeposition. The prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), high resolution transmission electron microscopy(HRETEM), energy dispersive X-Ray spectroscopy(EDX), X-ray photoelectron (XPS), UV–Vis diffuse reflectance spectra (DRS) and photoluminescence (PL). It was found that the Ag, B, and Eu tri-modified BiVO4 catalyst displays an apparently elevated photocatalytic performance towards methyl orange (MO) and tetracycline (TC) degradation compared to the as-prepared pure, single or co-modified BiVO4 samples. A possible mechanism for the improved photocatalytic activity of Ag, B, and Eu tri-modified BiVO4 was also investigated. The enhanced photocatalytic activity can be mainly ascribed to the improved charge separation and transfer efficiency originating from the synergistic effect of the Ag, B, and Eu introduction.
High-temperature order-disorder phase transition in Fe-18Ga alloy evaluated by internal friction method J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Meng Sun, Xianping Wang, Le Wang, Hui Wang, Weibin Jiang, Wang Liu, Ting Hao, Rui Gao, Yunxia Gao, Tao Zhang, Li Wang, Qianfeng Fang, Changsong Liu
The structure, internal friction (IF) behavior, resistivity and magnetostriction property of Fe-18Ga alloy were systematically analyzed in this investigation. In the IF spectra of Fe-18Ga alloy covered from room temperature (RT) to 800 °C, a prominent IF peak (labeled as Ptr peak) was observed in the high temperature range 530 °C–690 °C besides the reported IF peak related with grain boundary relaxation in the moderate temperature range 400 °C–530 °C. The peak position of Ptr peak hardly changes with measuring frequency, implying that its mechanism is most possibly related with phase transition. Considering from the wide peak shape, Ptr peak can be decomposed into two components: the lower temperature Ptr1 peak located around 530 °C–605 °C and the higher temperature Ptr2 peak located around 605 °C–690 °C. Combined with calculated phase diagram, resistivity and magnetostriction analysis, the mechanism of Ptr peak was suggested to originate from the order-disorder phase transition related with Ga atom distribution in Fe-18Ga alloy: Ptr1 peak was ascribed to D03→B2 transition and Ptr2 peak was ascribed to B2→A2 transition, respectively.
Tunable ferromagnetic resonance linewidth of cobalt-substituted NiCuZn ferrites J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Kaiwei Li, Ke Sun, Chuan Chen, Xin Liu, Rongdi Guo, Hai Liu, Zhong Yu, Xiaona Jiang, Zhongwen Lan
Polycrystalline ferrites Ni0.5-xCu0.12Zn0.4CoxFe1.98O4-δ with different cobalt-substituted contents (x = 0, 0.003, 0.006, 0.009, 0.012, 0.015) are synthetized via the solid-state reaction method. The magnetocrystalline anisotropy constant is calculated based on the law of approach to saturation. As the amount of cobalt substitution increases, the absolute value of the magnetocrystalline anisotropy constant first decreases and then rises due to the positive compensation by the Co2+ ions. The value of the magnetocrystalline anisotropy constant tends to be zero for the samples with cobalt substitution contents in the range of 0.003–0.006. Meanwhile, when the cobalt substitution content is 0.003, the NiCuZn ferrite shows minimum ferromagnetic resonance linewidth (9.87 kA/m) and low dielectric loss tangent (tgδε, 1.1 × 10−4) at 9.4 GHz as well as a high magnetization (Ms, 406 kA/m) and high squareness ratio (Br/Bs, 0.83). Furthermore, the linewidth contribution is identified by the anisotropy and porosity linewidth broadening model based on the spin-wave approach, and the results show that porosity linewidth broadening is the predominant effect.
Van der Waals graphene/g-GaSe heterostructure: Tuning the electronic properties and Schottky barrier by interlayer coupling, biaxial strain, and electric gating J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Huynh V. Phuc, Victor V. Ilyasov, Nguyen N. Hieu, Bin Amin, Chuong V. Nguyen
Graphene-based van der Waals heterostructures are expected recently to design and fabricate many novel electronic and optoelectronic devices. The combination of the electronic structures of graphene and graphene-like GaSe monolayer (g-GaSe) in an ultrathin heterostructure has been realized experimentally, such as graphene/g-GaSe field effect transistor and dual Schottky diode device. In the present work, we investigate the electronic properties of the graphene/g-GaSe heterostructures under the applied electric field, in-plane strains, and interlayer coupling. Our results show that the electronic properties of the graphene/g-GaSe heterostructures are well preserved owing to a weak vdW interaction. Especially, a tiny band gap of 13 meV has opened in the presence of the g-GaSe monolayer. We found that the n-type Schottky contact is formed in the graphene/g-GaSe heterostructure with a Schottky barrier height of 0.86 eV, which can be efficiently modulated by applying the electric field, in-plane strains, and interlayer coupling. Furthermore, a transformation from the n-type to p-type Schottky contact is observed when the applied electric field is larger than 0.1 V/Å or the interlayer distance is smaller than 3.2 Å. Our results may provide helpful information to design and fabricate the future graphene-based vdW heterostructures, such as graphene/g-GaSe heterostructure and understand the physics mechanism in the graphene-based 2D vdW heterostructures.
Preparation and electrical characteristics of N-doped In-Zn-Sn-O thin film transistors by radio frequency magnetron sputtering J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Jinbao Su, Ye Wang, Yaobin Ma, Qi Wang, Longjie Tian, Shiqian Dai, Ran Li, Xiqing Zhang, Yongsheng Wang
Bottom-gate top-contact thin film transistors (TFTs) with an active layer of N-doped Indium-Zinc-Tin-Oxide (IZTO:N) were prepared and their electrical properties were studied in this paper. The IZTO:N film was deposited on SiO2/Si substrates by radio frequency (RF) magnetron sputtering at room temperature. The transmittance of the IZTO:N film was over 80% in the visible range. Secondary ion mass spectrometry (SIMS) result showed all the species (In, Zn, Sn, O and N) were uniformly distributed in the film. X-ray diffraction (XRD) patterns revealed that the film was amorphous structure. The obtained IZTO:N TFT operating in the enhancement mode exhibited promising electrical performance with a high saturation mobility of 35.1 cm2/V·s, on/off current ratio of 7.2 × 107, and threshold voltage of 0.4 V.
Comparison of corrosion behaviors between Ti-based bulk metallic glasses and its composites J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Y.J. Yang, Z.S. Jin, X.Z. Ma, Z.P. Zhang, H. Zhong, M.Z. Ma, X.Y. Zhang, G. Li, R.P. Liu
The corrosion behaviors of the Ti-based bulk metallic glasses (Zr30.88Ti33.57Cu7Ni5.39Be23.16) as well as the in-situ Ti-based bulk metallic glass matrix composites (Zr28.92Ti42.22Cu6.57Nb6Be16.29) in 0.6 mol/L NaCl, 1 mol/L HCl and 0.5 mol/L H2SO4 solutions were analyzed. The potentiodynamic polarization analyses indicated a drastic increase in the current densities for all specimens in the NaCl and HCl solutions, which could be related to the passive breakdown caused by pitting corrosion. In contrast, no active-passive transition existed in the H2SO4 solution. SEM and EDS analyses were performed to clarify the morphologies and chemical states of the elements prior to and following electrochemical testing. The results demonstrated that both alloys exhibited entirely different corrosion behaviors in the chloride-containing and chloride-free solutions. The surfaces of the samples were locally damaged by a chloride-induced pitting process. Specifically for the composites, a selective dissolution occurred. In contrast, a low portion of corrosion occurred within the chloride-free media. The chemical compositions were identified as the main factor to affect the corrosion performance of the alloys.
Optical and thermal properties of Sb/Bi-modified mixed Ge-Ga-Se-Te glasses J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 R. Golovchak, A. Kozdras, T. Hodge, J. Szlęzak, C. Boussard-Pledel, Ya Shpotyuk, B. Bureau
The non-isothermal crystallization kinetics of novel BixGa5Ge20Sb10-xSe45Te20 (x = 1,3,5,10) glasses are studied with differential scanning calorimetry method, and analysed using Frazer-Suzuki fitting function. The applicability of Johnson-Mehl-Avrami (JMA) model to describe the crystallization kinetics in these materials is verified, and JMA exponent is determined for the relevant crystallization processes. It is found, that substitution of Sb with Bi in glass composition leads to a decrease in optical gap and thermal stability of the glass, and increase in the density and crystallization activation energy for glass-ceramics formation.
Reduction of Eu3+ to Eu2+ in α-Y2Si2O7 and X1-Y2SiO5 and their luminescent properties J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Azucena Arias Martínez, Rubén Arroyo-Murillo, Katleen Korthout, Dirk Poelman
Due to its bright tunable emission, Eu-doped yttrium silicates are very interesting materials for LED applications. The microparticles of α-Y1.98 Eu0.02 Si2O7 and the low-temperature phase of Y1.98 Eu0.02 SiO5 (X1) were prepared by sol gel technique. Then, the samples were reduced at high temperatures using pure hydrogen as reduction agent. The materials obtained were characterized by X-Ray diffraction, Scanning Electron Microscopy, Energy Dispersive X-Ray and Photoluminescence spectroscopy. The presence of Eu2+ in the materials after the reduction was confirmed by the blue-green band emission and the wide absorption band, observed only in the excitation spectra of the reduced samples. These bands are congruent with the information previously reported in the literature. A red shift of the broadband emission of Eu2+ doped α-Y2Si2O7 system was observed compared to previously reported results. Also, the luminescent properties of Eu2+ host in X1-Y2SiO5 are presented for first time. The relative contribution of Eu2+ and Eu3+ depends on the excitation wavelength leading to a tunable emission phosphor with potential application in white LEDs. Summarizing, the reduction of Eu ions in yttrium silicates is presented in this work, leading to a tunable emission phosphor with potential application in white LEDs.
A theoretical investigation of structural, electronic and optical properties of bulk copper nitrides J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Mohammed S.H. Suleiman, Mahlaga P. Molepo, Daniel P. Joubert
We present a first-principles density functional theory (DFT) study of the structural stability and electronic properties of bulk crystalline Cu4N, Cu3N, CuN and CuN2 in a set of twenty one different structural phases. By analysing the energetics of these systems, we show that D09, B17 and C18 are the most stable phases in the parameter space considered for the Cu3N, CuN and CuN2 stoichiometric series, respectively. This study predicts that other Cu3N phases (i.e. RhF3 and D02) have similar stability to D09, and may be present during the nitridation process. These stable Cu3N phases are found to be indirect band-gap semiconductors with lower bulk moduli, whereas CuN(B17) preserves the metallicity and has a larger bulk modulus than pure Cu. Furthermore, the optical spectra of the experimentally synthesized Cu3N phase (D09) is investigated by GW0 calculations within the random phase approximation to the dielectric tensor. The obtained optical energy band-gap significantly improves the DFT values and agrees with some experiments.
Hollow nickel microtube /carbon nanospheres Core–Shell arrays as electrode material for rechargeable Li-ion batteries J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Meili Qi, Yu Zhong, Minghua Chen, Ye Dai, Xinhui Xia
Carbonaceous anode materials are widely used for a variety of applications in current electrochemical energy storage field. However, carbon nanospheres are much more difficult to be directionally assembled into self-supported arrays. In this paper, we demonstrate a facile and controlled strategy to effectively synthesize the hollow nickel microtube/carbon nanospheres core–shell arrays. The unique core–shell arrays structural is beneficial to electron conduction and structural stability of whole composite material as a binder-free electrode. The hollow nickel microtube/carbon nanospheres core–shell arrays exhibit good the reversible capacity, rate capability and a specific capacity of 148 mAhh g−1 after 100 cycles by the effective improved of electrical conductivity and constructing open channels for Li ion diffusion.
Cobalt phosphide microsphere as an efficient bifunctional oxygen catalyst for Li-air batteries J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Feng Zhang, Minghui Wei, Jing Sui, Chao Jin, Yong Luo, Shiyu Bie, Ruizhi Yang
An efficient bifunctional catalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly desired for the application of rechargeable metal air batteries. Herein, urchin-like CoP microspheres have been synthesized by a facile hydrothermal method with cetrimonium bromide as soft template. In alkaline solution, the as-prepared CoP catalyzes the ORR with an onset potential of −0.11 V (vs. Ag/AgCl) and a potential gap of 62 mV compared with commercial Pt/C catalyst. Meanwhile, the CoP catalyst exhibits better OER activities than the commercial RuO2 catalyst. Interestingly, when employed as cathodic catalyst for Li-air batteries, the battery shows good discharge capacity of 2994 mAh g−1 at 100 mA g−1, high round-trip efficiency of over 90%, excellent rate capability and cycle stability of sustaining 80 cycles without any capacity degradation at a high discharge current density of 500 mA g−1.
Facile synthesis of Au@α-Fe2O3@RGO ternary nanocomposites for enhanced electrochemical sensing of caffeic acid toward biomedical applications J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 G. Bharath, Emad Alhseinat, Rajesh Madhu, Samuel M. Mugo, Saleh Alwasel, Abdel Halim Harrath
Demonstrated herewith is a novel eco-friendly Au@α-Fe2O3@RGO ternary nanocomposites using chlorophyll as reductants and stabilizers. Systematic characterizations studies confirm Au and α-Fe2O3 nanoparticles are uniformly decorated on the surfaces of reduced graphene oxide (RGO) nanosheets. As a proof-of-concept, the developed Au@α-Fe2O3@RGO ternary nanocomposites were coated on a glass carbon electrode (GCE) and evaluated for electrochemical detection of caffeic acid. The electrochemical mechanism involves the synergistic electrocatalytic activity of Au and α-Fe2O3 towards caffeic acid oxidation, with the RGO serving as an efficient electron shuttling mediator–enhancing the sensor performance. The Au@α-Fe2O3@RGO modified GCE caffeic acid sensor exhibited a wide linear response range of 19–1869 μM, sensitivity of 315 μA μM−1 cm-2, and a detection limit of 0.098 μM at very low potential of 0.21 V. This ternary nanocomposite provides high catalytic performance as well as excellent selectivity toward caffeic acid. To demonstrate real life application of the Fe2O3@RGO modified GCE caffeic acid sensor, caffeic acid in a coffee sample was measured. The α-Fe2O3, Au-NPs, and conductive graphene sheets composites, result in a highly catalytic and stable electrode system, with no pulverization problems. As such, it is demonstrated herewith that the Fe2O3@RGO ternary nanocomposite electrode is rapid, highly stable, and sensitive, with promised for utilization in fabrication of other multifarious biosensors.
Synthesis, characterization and electrochemical performance of carbon/Ni-doped CeO2 composites J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Sumalin Phokha, Sitchai Hunpratub, Narong Chanlek, Somchai Sonsupap, Santi Maensiri
The electrochemical properties of carbon were improved by forming composites with Ni-doped CeO2 nanoparticles to obtain a material with potential for application in high performance energy storage devices. Composites of Ni-doped CeO2 (Ce1-xNixO2, x = 0, 0.05, 0.10 and 0.20) nanoparticles were formed with carbon by hydrothermal treatment at a temperature of 150 °C for 12 h, hitherto referred to as carbon/CeO2, carbon/5Ni CeO2, carbon/10Ni CeO2 and carbon/20Ni CeO2 for x = 0, 0.05, 0.10 and 0.20, respectively. CeO2 nanoparticles without carbon were also prepared by the same method for comparison. All samples were characterized by X-ray diffraction (XRD), Raman spectroscopy (Raman), energy dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM) - elemental mapping, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and a potentiostat/galvanostat electrochemical cell system. The samples exhibited XRD and Raman peaks corresponding to carbon and FCC CeO2, confirming the formation of composites. The presence of Ce4+, Ce3+/oxygen vacancies and Ni2+ in all composites was confirmed by XPS measurements. The specific capacitances at a current density of 0.25 A/g were in the range of 138.8–252.6 F/g for electrodes made from carbon/Ni-doped CeO2, which were higher than that of CeO2 (11.9 F/g) and carbon (64.1 F/g) alone. These results suggest that composites of Ni-doped CeO2 nanoparticles with carbon have improved capacitive behavior as electrodes due to a higher concentration ratio of Ce3+/Ce4+.
Crystal structure, phase composition and microwave dielectric properties of Ca3MSi2O9 ceramics J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Xiao-Qiang Song, Kang Du, Xian-Zhe Zhang, Jie Li, Wen-Zhong Lu, Xiao-Chuan Wang, Wen Lei
Ca3MSi2O9 (M = Zr, Hf, Sn1−xTix; x = 0–0.40) low-permittivity microwave dielectric ceramics with cuspidine structure were prepared using conventional solid-state method at 1325 °C–1400 °C for 10 h in air. The lattice parameters of Ca3MSi2O9 (CMS) linearly decreased when M changed from Zr to Sn0.85Ti0.15, and a single phase was formed. For M = Sn1−xTix (x = 0.20–0.40), a second phase of CaTiO3 (CT) appeared. The relative permittivity (εr), quality factor (Q × f), and temperature coefficient of resonant frequency (τf) were closely related to ionic polarizability, relative covalence of M site, unit-cell volume, and CaTiO3 second phase. As a result, the highest Q × f value of 72840 GHz was obtained for M = Sn0.95Ti0.05, and near zero τf value was achieved for M = Sn0.7Ti0.30. The microwave dielectric properties of which are as follows: εr = 11.07, Q × f = 42400 GHz, and τf = −5.1 ppm/°C.
Materials, processing and reliability of low temperature bonding in 3D chip stacking J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-07 Liang Zhang, Zhi-quan Liu, Sinn-Wen Chen, Yao-dong Wang, Wei-Min Long, Yong-huan Guo, Song-quan Wang, Guo Ye, Liu Wen-yi
Due to the advantages of small form factor, high performance, low power consumption, and high density integration, three-dimensional integrated circuits (3D ICs) have been generally acknowledged as the next generation semiconductor technology. Low temperature bonding is the key technology to ensure the chip (or wafer) stacking in 3D ICs. In this paper, different low temperature bonding methods for chip (or wafer) stacking were reviewed and described systematically. Materials, processing and reliability will be extremely important, their effects on the 3D IC structure were addressed in detail, the challenging reliability issues may be considered as the major concern in the future work. The latest development of low temperature bonding in 3D ICs is also given here, which helpful may provide a reference for the further study of low temperature bonding.
Phase boundary sliding of a reticular-structured Mg-O-9Al alloy J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-06 S.W. Kang, H. Kang, H.J. Choi, D.H. Bae
In a Mg-9Al alloy containing O atoms (Mg-O-9Al alloy) supplied from the decomposition of TiO2 nanoparticles in a Mg-9Al melt, the O atoms are mostly located in the eutectic β-phase after solidification. During homogenization treatment, the β-phase decomposes and the α′′-phase (hard) surrounded by thick α′-phase (soft) gradually develops by the spinodal decomposition of the homogenized α-phase. That is, when the compositions of both Al and O atoms are reached at near 5 at% in the α-phase, the spinodal decomposition activates in the range of the homogenization temperatures. The core-mantle structured (i.e., reticular-structured) Mg-O-9Al alloy shows high hardness and elastic modulus, and yield stress of 129 MPa and elongation to failure of 15.7%, much higher than those obtained in the homogenized Mg-9Al alloy (87 MPa and 8.7%). Because the hard α′′-phase is wrapped by the soft α′-phase, the α′′-phase undergoes phase boundary sliding during plastic deformation at room and high temperatures, exhibiting the α′′-phase rotation and shear deformation of the α′-phase. The alloy shows a strain rate sensitivity in the range of 0 (dislocation activity) to 1 (diffusion flow), depending on the plastic deformation mechanism of the α′-phase.
Experimental investigation and thermodynamic modelling of LiF-NdF3-DyF3 system J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-06 A. Abbasalizadeh, S. Sridar, Z. Chen, M. Sluiter, Y. Yang, J. Sietsma, S. Seetharaman, K.C. Hari Kumar
Electrolysis of molten fluorides is one of the promising methods for the recovery and recycling of rare earth metals from used magnets. Due to the dearth of phase equilibria data for molten fluoride systems, thermodynamic modelling of LiF-DyF3-NdF3 system using the CALPHAD approach was carried out. Gibbs energy modelling for LiF-NdF3 and LiF-DyF3 systems was performed using the constitutional data from literature. Ab initio calculations were used to obtain enthalpy of reaction of LiDyF4, an intermediate phase that is found to exist in the LiF-DyF3 system. Differential thermal analysis was carried out for selected compositions in the NdF3-DyF3 system, in order to determine liquidus and solidus temperatures. The Gibbs energy parameters for the limiting binaries determined in this work is used for modelling the Gibbs energy functions of equilibrium phases in the ternary system. Selected compositions of LiF-NdF3-DyF3 were subjected to DTA in order to validate the calculated phase temperatures involving melt.
Resistance of microcrystalline and nanocrystalline Cu/Cr pseudo-alloys to vacuum discharge J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-06 K.V. Kuskov, A.S. Rogachev, S.G. Vadchenko, N.F. Shkodich, S. Rouvimov, A.S. Shchukin, E.V. Illarionova, V.A. Kudryashov, A.S. Mukasyan
Microcrystalline and nanocrystalline Cu/Cr pseudo-alloy electrodes were prepared from elemental powders using high-energy ball milling and spark plasma sintering, and were characterized by SEM, TEM, EDS, and AFM. Vacuum discharge tests were conducted in order to reveal how the microstructure influences the material resistance to surface damage by vacuum electric sparks and arcs. Numerous micro-craters with morphologies typical for explosive electron emission appeared on the surface of the microcrystalline cathode, while the surface of nanocrystalline cathode remained undamaged. At the same time, vacuum discharge caused Cu to melt on the anode surface for both types of microstructure, and vacuum arc melts Cu and Cr independent of the microstructure and electrode polarity. Thus, a decrease of the Cr grain size may prevent cathode material damage by explosive electron emission (probably due to electron scattering on the grain boundaries), and only slightly influences the resistance of electrodes against arcing or high-energy electron bombardment. These results can be used in development of new electrodes for vacuum interrupters, cathodes of vacuum diodes and other equipment that involve vacuum discharges.
Insight into the structure and functional application of Mg-doped Na0.5Bi0.5TiO3 electrolyte for solid oxide fuel cells J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-06 Yao Lu, Carlos Alberto López, Jie Wang, José Antonio Alonso, Chunwen Sun
Na0.5Bi0.5TiO3 (NBT) and its acceptor-doped perovskites, as lead-free piezoelectric materials before, have been found to be excellent oxygen-ion conductors with potential applications in intermediate-temperature solid oxide fuel cells (SOFCs). Among them, the Bi deficient and B-site Mg doped sodium bismuth titanate (Na0.5Bi0.49Ti0.98Mg0.02O2.965, NBTM) exhibits a remarkable oxygen ionic conductivity. Here, we report a structural analysis on NBT and NBTM ceramics using high-temperature in situ neutron diffraction (NPD) to gain insight into the effects of Mg doping on ionic conductivity and structure. Both perovskite oxides exhibit two consecutive phase transformations from R3c to P4bm at ∼400 °C and from P4bm to Pm 3 ¯ m at ∼600 °C. The effects of Bi deficiency and Mg substitution on oxygen vacancy concentration and ion displacements are revealed. In addition, a NBTM supported single cell consisting of Ag-NBTM cathode and Ni-NBTM anode is fabricated to evaluate the possibility of its application in intermediate-temperature SOFCs. The structural stability of NBTM is still a major concern that hinders its utilization at high temperature and under reducing atmosphere.
The similar Cole-Cole semicircles and microwave absorption of Hexagonal Co/C composites J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-06 Wenjia Xing, Ping Li, Hua Wang, Qin Lei, Yong Huang, Junlong Fan, Guangliang Xu
Hexagonal Co/C composites have been successfully prepared by hydrothermal method. And the preparation of hexagonal Co/C composites can provide possibilities for fabricating other metal/C composites. With different content carbon, the absorbing capacities of hexagonal Co/C are different. By analyzing the electromagnetic parameters, we have proved the similar Cole-Cole semicircles in μ″-μ′ curves and each similar Cole-Cole corresponds to a loss of resonance. However, the first similar Cole-Cole semicircle has more important to reflection loss (RL). The optimum RL value is −47.5 dB, and the broadest band of RL ≤ -10 dB is 5.6 GHz.
Crystal structure refinement, dielectric and magnetic properties of A-site and B-site co-substituted Bi0.90Nd0.10Fe1-xTixO3 (x=0.00, 0.02, 0.05 & 0.07) ceramics J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-06 Manisha Yadav, Ashish Agarwal, Sujata Sanghi, R.K. Kotnala, Jyoti Shah, Tanvi Bhasin, Muskaan Tuteja, Jogender Singh
Nd and Ti co-doped Bi0.90Nd0.10Fe1-xTixO3 (x = 0.00, 0.02, 0.05 & 0.07) ceramics were prepared via conventional solid state reaction method. The crystal structure was investigated by X-ray diffraction at room temperature. The XRD data was further studied by Rietveld refinement using Full prof suite which revealed the structural transformation from rhombohedral (R3c) into triclinic (P1) phase. Low values of R factors and χ2 showed good agreement between experimental and refined intensities. The analysis of Raman spectra is consistent with the earlier reported data. Dielectric response of all the prepared samples was analyzed in the frequency range 100 Hz to 7 MHz at different temperatures. All the samples exhibited dispersion in dielectric constant values at lower frequencies and became nearly constant at higher frequencies. With Ti substitution, the dielectric constant became stable at higher frequencies due to suppression of oxygen vacancies. The temperature variation of dielectric constant and tanδ displayed sharp anomalies in the vicinity of Neel temperature. Impedance spectroscopy disclosed appearance of grain contributions in the prepared samples. Magnetic characterization was performed by using Vibrating sample magnetometer upto a field of 5 kOe at room temperature. The hysteresis loop exhibited inherent antiferromagnetism with a weak ferromagnetism. The maximum remnant magnetization (Mr) is observed for Bi0.90Nd0.10Fe0.95Ti0.05O3 is 3.15 memu/g and the corresponding value of coercive field is 130.65 Oe.
Fabrication of hierarchical bristle-grass-like NH4Al(OH)2CO3@Ni(OH)2 core-shell structure and its enhanced Congo red adsorption performance J. Alloys Compd. (IF 3.133) Pub Date : 2018-04-06 Yingqiu Zheng, Hongyang Wang, Bei Cheng, Wei You, Jiaguo Yu
Hierarchical bristle-grass-like NH4Al(OH)2CO3@Ni(OH)2 core-shell structure is fabricated through a simple hydrothermal approach combined with subsequent chemical bath deposition. Electron microscopy characterization reveals that the ammonium aluminum carbonate hydroxide (NH4Al(OH)2CO3) microfibers were uniformly covered with interconnected and vertically aligned nickel(II) hydroxide (Ni(OH)2) nanosheets, forming hierarchical pore structure. The NH4Al(OH)2CO3 microfibers not only serve as substrate for the growth of the Ni(OH)2 nanosheets but also prevent the nanosheets from aggregating. The synthesized hierarchical bristle-grass-like NH4Al(OH)2CO3@Ni(OH)2 composite showed excellent adsorption performance toward Congo red (CR), which was superior to the aggregated Ni(OH)2 microspheres and the bare NH4Al(OH)2CO3 microfibers. The adsorption isotherm can be well described by the Langmuir model, with an estimated maximum adsorption capacity of 426 mg g−1 for the NH4Al(OH)2CO3@Ni(OH)2 composite. The major adsorption mechanism is electrostatic interaction between the CR molecules with negative charge and the positively charged sample surface of the Ni(OH)2 nanosheets at neutral pH. The as-prepared NH4Al(OH)2CO3@Ni(OH)2 core-shell microfibers can be expected to act as potential materials for CR removal in purification of wastewater.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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