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  • The structure and magnetic properties of pure single phase BiFeO3 nanoparticles by microwave-assisted sol-gel method
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-20
    Shuai Zheng, Jiangying Wang, Jingji Zhang, Hongliang Ge, Zhi Chen, YaFeng Gao

    The pure single phase BiFeO3 nanoparticles have been prepared by microwave-assisted sol-gel process and its structure and magnetic properties have been studied. X-ray diffractometer, infrared and transmission electron microscope results show that the synthesized BiFeO3 nanoparticles at the calcining temperature of 450 °C exhibits a rhombohedrally distorted perovskite structure without secondary phase and the size is about 40 nm. Meanwhile, the pure single phase BiFeO3 particles exhibit typical ferromagnetic properties at room temperature and the obvious large exchange bias phenomenon at 60 K. A exchange bias field (HE) of 302 Oe at 60 K for pure single phase BiFeO3 nanoparticles at calcining temperature 450 °C after field cooling at 20 KOe has been observed. The MT curve at H = 100 Oe shows that the FC and ZFC magnetization curves start to differ in the temperature range from 60 K to 300 K revealing spin glass behavior of BiFeO3 nanoparticles at calcining temperature 450 °C, 500 °C and 550 °C. The ferromagnetic behavior is attributed to size of effects, which partially destroy the long-wavelength cycloid spin structure expected in bulk BiFeO3. The exchange bias effect in single crystalline BiFeO3 nanoparticles arises from co-existence of different magnetic phases of an antiferromagnetic core and a ferromagnetic surface. The ferromagnetic, exchange bias effect and spin glass behavior of BiFeO3 nanoparticles are assigned to the uncompensated or canted spins at the ferromagnetic surface and an antiferromagnetic core of BiFeO3 nanoparticles.

    更新日期:2017-11-20
  • Core-shell Fe3O4@Fe ultrafine nanoparticles as advanced anodes for Li-ion batteries
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    Yuepeng Pang, Jing Wang, Zhiguo Zhou, Tao Yuan, Junhe Yang, Dalin Sun, Shiyou Zheng

    Core-shell Fe3O4@Fe ultrafine nanoparticles (nano-Fe3O4@Fe, Fe3O4 content 84 wt%) with a core (Fe) diameter of 5.1 ± 1.4 nm and a shell (Fe3O4) diameter of 10.9 ± 1.6 nm is prepared by a liquid-phase pyrolysis and partial oxidation method. It is found that the core-shell Fe3O4@Fe ultrafine nanostructure can efficiently improve the electrochemical performance of Fe3O4 as anode material for Li-ion batteries in terms of rate capability and cycle life. For instance, specific capacities of 884 and 705 mAh/g can be obtained for the nano-Fe3O4@Fe electrode after 100 cycles at 200 mA/g and 500 cycles at 1000 mA/g, respectively. It is believed that these improvements can be attributed to the significant shortened transfer distance of electrons and Li-ions with relatively low specific surface area, ultrahigh electronic conductivity inside the nanoparticles and good ductility to accommodate the asymmetric volume change.

    更新日期:2017-11-20
  • The evolution of magnetization switching of LuCrO3 by the effect of Mn doping
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    De-xiang Fu, Yu-zhuang Liu, Hong-guang Zhang, Liang Xie, Bin Li

    The crystal structure, magnetic properties and electronic structures of LuCr1-xMnxO3 (x = 0, 0.1, 0.2, and 0.3) series samples were systematically investigated. The crystal structure of the Mn-doped LuCrO3 samples is orthorhombic structure with Pbnm, consistent with the pristine LuCrO3. Synchrotron radiation x-ray absorption spectroscopy of Mn 2p, Cr 2p and O 1s core levels show that Cr ion is trivalent and its valence state does not change with doping. However, the valence state of Mn ions for samples with x = 0.1 and 0.3 is mainly in Mn2+ while it is dominated by Mn3+ for the sample x = 0.2. This leads to the diversely unoccupied 3d states of transitional metal ions, which hybridized with O 2p levels. The energy diagram of each transitional metal ions in our samples were provided. More interesting, magnetic data shows the negative magnetization in zero-field-cooling MZFC(T) curve below TN. And the evolution of MFC(T) and MZFC(T) curves coming to converge and intersect with each other are caused by Mn doping. Also, multiple magnetic phases with a new magnetic phase transition at 30 K were induced by the effect of Mn doping. Our results demonstrate that the antiferromagnetic coupling of Mn2+ being antiparallel with spin moment of Cr3+ is favor of the magnetization switching while the ferromagnetic coupling of Mn3+ overcomes the Cr3+ ions ordering and destroys the magnetization switching.

    更新日期:2017-11-20
  • Structural, magnetic and magnetocaloric properties of HoNi2 and ErNi2 compounds ordered at low temperatures
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    J. Ćwik, Y. Koshkid'ko, K. Nenkov, E.A. Tereshina, K. Rogacki

    In this work we report on the structural, magnetic and magnetocaloric properties of polycrystalline HoNi2 and ErNi2 Laves-phase compounds. Powder X-ray diffraction studies at room temperature show that the compounds crystallize in the cubic C15 structure (MgCu2 type). The magnetic measurements reveal that the second-order magnetic phase transition from ferromagnetic to paramagnetic state appears at TC equal 13.5 K for HoNi2 and 6.5 K for ErNi2. Using direct measurements over a wide field range (up to 11 T), along with indirect methods, we have found low and high field regularities of the magnetocaloric effect characterized by the adiabatic temperature change, ΔTad, and the isothermal magnetic entropy change, ΔSmag. The magnetocaloric properties near the phase transition are discussed in the framework of the Landau theory for the second-order phase transitions.

    更新日期:2017-11-20
  • Characterization of nanostructured biodegradable Zn-Mn alloy synthesized by mechanical alloying
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    P. Sotoudeh Bagha, S. Khaleghpanah, S. Sheibani, M. Khakbiz, A. Zakeri

    In this study, nanostructured biodegradable pure Zn, Zn-4 wt. % Mn and Zn-24 wt. % Mn alloys were produced by 20 h mechanical alloying and consequent cold pressing and sintering. Structural evolutions were investigated using the X-ray diffraction technique. Also, the microstructure was characterized by scanning electron microscopy. The effects of alloy composition on density, mechanical properties, corrosion behavior in Hank's solution, cell viability and cell attachment were investigated. Crystallite size of the synthesized alloys after 20 h of milling reached to less than 40 nm and remained less than 80 nm after consolidation and sintering for 1 h. Alloys contain MnZn13 as second phase which affect mechanical and corrosion properties. Compressive yield strength of Zn, Zn-4Mn and Zn-24Mn alloys reached from 33 to 290 and 132 MPa and corrosion rate of Zn-4Mn tailored to 0.72 mm/yr. Cell viability and cell attachment show biocompatibility of these alloys. Results demonstrate that Zn-Mn alloy can be a new suitable biodegradable candidate.

    更新日期:2017-11-20
  • Ag nanoparticle-decorated biscuit-like Bi24O31Cl10 hierarchical microstructure composed of ultrathin nanoflake with outstanding photocatalytic activity
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    Jian Song, Lei Zhang, Jian Yang, Jin-Song Hu, Xin-Hua Huang

    Fabrication of noble-metal nanoparticle decorated hierarchical heterostructure photocatalyst composed of ultrathin nanoflake can be considered as one of the most effective approach for enhancing the photocatalytic performance due to its unique micro-scale structure and functional combination. Therefore, we report the successful preparation of Ag nanoparticle-decorated biscuit-like Bi24O31Cl10 hierarchical microstructure through a facile solution-phase synthesis route. Experiment indicated that the Bi24O31Cl10 product was comprised of ultrathin nanoflake with thickness of 5–10 nm. After introducing Ag nanoparticle, the as-obtained Ag-Bi24O31Cl10 nanocomposite exhibited improved photocatalytic performance for the decolorization of rhodamine B in comparison to pure Bi24O31Cl10 sample. The amount of Ag in the heterostructure photocatalyst significantly influenced the photocatalytic efficiency, and 4 wt% Ag exhibited the best photocatalytic performance. In addition, an enhanced mechanism of photodegradation activity over Ag nanoparticle-decorated biscuit-like Bi24O31Cl10 hierarchical microstructure was proposed.

    更新日期:2017-11-20
  • Mechanical properties of Al matrix composite reinforced with diamond particles with W coatings prepared by the magnetron sputtering method
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    Guoqin Chen, Wenshu Yang, Ling Xin, Pingping Wang, Shufeng Liu, Jing Qiao, Fengjiao Hu, Qiang Zhang, Gaohui Wu

    In the present work, the effect of W coatings prepared by the magnetron sputtering method on the mechanical performance of the Al matrix composites reinforced with diamond particles (Diamond/Al) has been explored. Since no debonding was observed between the diamond and the Al matrix in the composites with 45 nm and thicker W coatings while serious debonding was found in the composite without W coating, the interfacial bonding between the diamond particles (all the {100} and {111} facets) and the Al matrix has been improved. Further TEM observation indicated that the W coating has been well bonded with the diamond particle and the Al matrix, and no interfacial reaction product has been found. Furthermore, the fracture behaviors of the Diamond/Al composites were also affected by the W coatings. Compared to that of the Diamond/Al composite without W coating, the bending strength and the displacement of the bending failure of the Diamond/Al composites with 45 nm W coating have been improved 24% (from 245 to 304 MPa) and 120% (from 0.28 to 0.62 mm), respectively. Moreover, the summative results from the literatures and the present work indicate that the Diamond/Al composites have higher strength usually demonstrates higher thermal conductivity, which might be related to the interfacial performance of the composites.

    更新日期:2017-11-20
  • Chestnut husk-like nickel cobaltite hollow microspheres for the adsorption of Congo red
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    Hua Chen, Yingqiu Zheng, Bei Cheng, Jiaguo Yu, Chuanjia Jiang

    Although many materials have been investigated for treating organic dye-containing wastewater, their practical applications are limited because of the high cost, secondary pollution or intricate synthesis method. Herein, magnetic nickel cobaltite (NiCo2O4) hollow microspheres were fabricated by a simple solvothermal method followed by calcination at relatively low temperature, and evaluated for adsorptive removal of Congo red (CR) from water. The electron microscopy images demonstrated that the as-synthesized NiCo2O4 sample had a morphology of chestnut husk-like hollow microspheres with diameters ranging from 4 to 5 μm, which were assembled with plentiful nanorods. Due to the hierarchical hollow structure and positive surface charge under neutral pH condition, the NiCo2O4 hollow microspheres displayed better adsorption capacity compared with single-metal oxides of nickel and cobalt. Intra-particle diffusion and the pseudo-second-order models could well interpret the sorption kinetics of NiCo2O4 hollow microspheres. Meanwhile, the Langmuir model could well explain the isotherm process, and the maximal adsorption quantity of NiCo2O4 was 366 mg g−1. Moreover, the NiCo2O4 sample demonstrated fair recyclability, with a modest decline of the adsorption capacity after five cycle tests, even with a low regeneration temperature of 250 °C. These results imply the potential application of the as-synthesized NiCo2O4 hollow microspheres for the treatment of dye wastewater.

    更新日期:2017-11-20
  • Magnetic hardening of Fe-Pt and Fe-Pt- M (M=B, Si) microwires
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    A. Zhukov, M. Ipatov, A. Talaat, A. Aronin, G. Abrosimova, J.J. del Val, V. Zhukova

    We have prepared Fe-Pt and Fe-Pt- M (M = B, Si) microwires using Taylor-Ulitovsky technique and studied their magnetic properties. Magnetic properties considerably depend on the metallic core composition and annealing conditions. As-prepared microwires present either amorphous or mixture of amorphous and nanocrystalline phases with a presence of BCC FePt, FCC PtFe and small amount of tetragonal FePt phase. After annealing at 500 °C Fe50Pt40Si10 microwires we observed a remarkable magnetic hardening (coercivity increasing from 5 Oe up to 500 Oe) related to crystallization of as-prepared amorphous Fe50Pt40Si10 microwires. Annealed Fe50Pt50 sample present coercivity up to 800 Oe at 5K, but the magnetization of Fe50Pt50 sample is low and rapidly decreases with temperature. We discussed peculiarity of Fe50Pt50 microwires considering the influence of internal stresses on magnetic ordering of Fe-atoms.

    更新日期:2017-11-20
  • Complex dielectric and impedance analysis in a relaxor type ferroelectric/ferrimagnetic magnetoelectric (0.5)PbZr0.52Ti0.48O3+(0.5)CoFe2O4composite
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    M. Atif, S. Ahmed, M. Nadeem, M. Nasir Khan

    Magnetoelectric composite of particular composition (0.5)PbZr0.52Ti0.48O3+(0.5)CoFe2O4 was synthesized by citrate–sol–gel method. Rietveld refinement of X-ray diffraction (XRD) pattern confirmed the presence of cubic spinel structure for CoFe2O4 and the coexistence of tetragonal along with a rhombohedral perovskite structure for PbZr0.52Ti0.48O3 in the prepared sample. Whereas, scanning electron micrograph (SEM) showed dense and homogeneous distribution of constituent phases. Temperature dependent dielectric measurements showed an abnormal frequency dependent behavior in the prepared composition, which is typically a characteristic of relaxor type materials. The observed behavior is explained in terms of structural disorders which give rise to alteration in the octahedron configuration in the PbZr0.52Ti0.48O3 phase that could promote the formation of the polar regions, which changes the dielectric properties of the prepared sample. Impedance spectroscopy was employed to understand the conduction mechanism which is found to be governed by small polaron hopping (SPH) mechanism. Moreover, it was found that the activations energies deduced from the conduction and relaxation process of constituent phases were comparable to each other. These results confirm that electric/dielectric properties and relaxation phenomenon are related to the similar origin.

    更新日期:2017-11-20
  • Antiferromagnetic Kondo lattice CeIrGe2
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    Maria Szlawska, Alexander Gribanov, Svetlana Gribanova, Dariusz Kaczorowski

    A novel ternary intermetallic germanide CeIrGe2 has been studied by means of x-ray diffraction, magnetization, specific heat and electrical resistivity measurements, performed in wide ranges of temperature and external magnetic fields. The compound crystallizes in an orthorhombic structure of the CeNiSi2-type (space group Cmcm). It exhibits a Kondo lattice behavior and orders antiferromagnetically at 4 K.

    更新日期:2017-11-19
  • Porous Fe2O3-C microcubes as anodes for lithium-ion batteries by rational introduction of Ag nanoparticles
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    Qin Li, Huijun Wang, Jingjing Ma, Xia Yang, Ruo Yuan, Yaqin Chai

    To solve the poor conductivity of the anode materials for lithium-ion batteries (LIBs) and enhance the lithium-ion transportation, silver-incorporated Fe2O3-C (Fe2O3-C-Ag) porous microcubes were fabricated through polydopamine reduction of AgNO3 and subsequently high temperature carbonization process using the prussian blue as template. Interestingly, polydopamine not only served as reducing agent for Ag+ but also as carbon source in this work, which avoid adding additional reduction agent and high temperature, resulting in a simple and mild reduction condition. When Fe2O3-C-Ag microcubes were performed as anode materials for lithium-ion batteries (LIBs), the hybrid materials behaved pretty electrochemical properties. The introduction of noble metal (Ag) and carbon to transition metal oxides was an innovative method to form anode materials for lithium-ion batteries (LIBs), which can effectively increase the conductivity of the electrode materials as well as inhibit the volume expansion during cycling. With 10% (wt%) Ag nanoparticles coating in the hybrid composites, the Fe2O3-C-Ag-10 microcubes exhibit good reversible capacities and pretty cyclic performance (858 mAh g−1 after 200 cycles at 100 mA g−1). This novel approach can provide a potential idea to design advanced anode materials for LIBs.

    更新日期:2017-11-17
  • Tm3+ doped barium molybdate: A potential long-lasting blue phosphor
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    Ana Paula de Azevedo Marques, Roseli Künzel, Nancy K. Umisedo, Renato Mazin Latini, Elizabeth Mateus Yoshimura, Emico Okuno

    Molybdates have applications in various fields such as phosphors, optical fibers, scintillators, magnets, sensors and catalysts. Thulium ion is an excellent blue activator and plays an important role in the design of persistent luminescent materials. This paper reports the investigation of the structural and luminescent properties of Barium Thulium Molybdate (Ba1−xTmx)MoO4 microcrystals (with x  = 0, 0.01 or 0.03). The scheelite-type crystalline structure was identified from XRD and Raman studies. Under ultraviolet (359 nm) excitation, photoluminescence (PL) spectra present the characteristic emission bands at 453 nm and 545 nm which are due to the View the MathML source D 1 2 → F 3 4 and View the MathML source D 1 2 → H 3 4 , 5 transitions, respectively, from Tm3+ ions. Thermoluminescence (TL) measurements were performed with powdered samples previously irradiated with beta radiation. The depth of traps, associated with trap levels located inside the band-gap, was determined from TL data using different methods of glow curve analysis. The kinetic parameters, determined from thermoluminescent glow curves, provide evidence about a possible persistent luminescence emission from the (Ba0.97Tm0.03)MoO4 sample. This is a potential blue-light or ultraviolet long-lasting phosphor, with a trapping level lifetime, at room-temperature (300 K), of about 6 days.

    更新日期:2017-11-17
  • Porous Ni@C derived from bimetallic Metal–Organic Frameworks and its application for improving LiBH4 dehydrogenation
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    XianHe Meng, ChuBin Wan, YuTing Wang, Xin Ju

    Hierarchically porous activated carbon (PAC) and Ni@C composite materials have been synthesized initially from MOF-5 and bimetallic Ni(II)-doped MOF-5s with the effective incorporation of Ni2+ ions into the frameworks. The products (PAC-1, Ni@C-1 and Ni@C-2) derived from MOFs contained rich micro/mesoporous structure and high specific surface areas (SSA): 2247, 919, and 484 m2 g−1, respectively. Interestingly, LiBH4 doped with Ni@C-1 showed the lowest onset temperature around 180 °C and fastest dehydrogenation kinetics. Results reveal that favorable synergistic effects of nanoconfinement and catalysis in Ni@C materials may improve hydrogen desorption kinetics, which demonstrates a promising strategy for the hydrogen-storage application of LiBH4.

    更新日期:2017-11-17
  • Thermoelectric response of quaternary Heusler compound CrVNbZn
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-16
    H. Kara, M. Upadhyay Kahaly, K. Özdoğan

    The electronic, magnetic and thermoelectric properties of CrVNbZn quaternary Heusler compound are investigated by means of first-principles calculations in combination with Boltzmann transport theory. The lattice is found to crystallize in the cubic quaternary Heusler structure (space group 216). As observed from the electronic bands near the Fermi level and corresponding densities of states (DOS), a prominent asymmetry in DOS is induced by V and Cr atoms followed by slight contribution from Nb. One sharp electronic band, with maximal contribution from V d electronic states, and just touching the Fermi level makes the system semiconducting, and enhances the thermoelectric figure of merit. The mechanism leading to this behavior is explained in terms of a local spin-polarization introduced by the V ions. Our results indicate that magnetic doping can play a strong role in tuning the electronic and magnetic properties of CrVNbZn compound, and in general in quaternary Heusler compounds.

    更新日期:2017-11-17
  • Electrical, dielectric and magnetic properties of Sn-doped hematite (α-SnxFe2-xO3) nanoplates synthesized by microwave-assisted method
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    K. Bindu, K.M. Ajith, H.S. Nagaraja

    Hematite nanoparticles are of interest due to their exceptional electrical and magnetic behavior and various technological applications. The doping of hematite can vary its electrical and magnetic properties. Here, we report the effect of different concentrations of Tin doping on electrical, dielectric and magnetic properties of hematite synthesized by the microwave-assisted method. Tin-doped α- Fe2O3 (α-SnxFe2-xO3) samples have been characterized using XRD, TGA, FESEM, and EDS (mapping). XRD pattern shows the rhombohedral structure of α-SnxFe2-xO3. The synthesized samples have nanoplate like structure with a uniform distribution of tin throughout the sample. Electrical properties were investigated using dielectric and impedance studies. The dc resistivity and ac conductivity decreased with increase in concentration up to x = 0.06 (Sn0.06Fe1.94O3). However, its increased with further increase in the concentration of tin. The hopping of electrons between Fe3+ and Fe2+ in octahedral sites accounts for the observed conduction behavior. A single semi-circle of the cole-cole plot for α-SnxFe2-xO3 indicates the dominant grain boundary effect in conduction. Dielectric constant and loss factor reveal the dielectric relaxation in α-SnxFe2-xO3 samples. The magnetic properties were studied using VSM, which shows that α-SnxFe2-xO3 are antiferromagnetic/weakly ferromagnetic in nature with high coercivity.

    更新日期:2017-11-17
  • Facile synthesis of CuFe2O4 crystals efficient for water oxidation and H2O2 reduction
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Yuqian Liu, Zhijuan Niu, Yiran Lu, Lin Zhang, Kai Yan

    Synthesis of a robust and bifunctional catalyst with earth-abundant element efficient for electrocatalytic reduction and oxidation is crucial in electrocatalytic energy conversion and storage. Herein we show that a facile method to synthesize CuFe2O4 crystals with octahedral shape as a bifunctional catalyst efficient for water oxidation and H2O2 reduction. These as-obtained CuFe2O4 catalysts exhibited high-performance for water oxidation (2.2 times current density higher than that of commercial RuO2), lower Tafel slope (∼50 mV dec−1), larger anodic current density and much enhanced electrochemical durability. Besides, the resulted CuFe2O4 catalyst was also efficient for electrocatalytic H2O2 reduction, it shows 5-fold increment of current density in the presence of 5 mM H2O2, high sensitivity and much improved stability. The cost-effective synthesis route holds great promise for the controllable synthesis of nanostructured spinel, and is expected to show promising applications in the generation of renewable energy.

    更新日期:2017-11-17
  • Ce @ TiO2 nanocomposites: An efficient, stable and affordable photocatalyst for the photodegradation of diclofenac sodium
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    M. Thiruppathi, P. Senthil Kumar, P. Devendran, C. Ramalingan, M. Swaminathan, E.R. Nagarajan

    In the present study, we explored the effective and enhanced photocatalytic degradation of diclofenac (DF) using Ce@TiO2 nanocomposites. The Ce@TiO2 nanocomposites was synthesized by simple precipitation method and characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and diffuse reflectance spectroscopy (DRS). The photocatalytic degradation of DF solution was investigated in the presence of Ce@TiO2 nanocomposites under UV irradiation. The extensive analysis of stability and reusability were investigated with photocatalytic degradation of DF, rose Bengal (RB) and acid red (AR). The catalyst was stable up to 6th run. The present investigation may be much useful for the application of Ce@TiO2 nanocomposite in wastewater treatment.

    更新日期:2017-11-17
  • Electrochemical characterization of nanocrystalline RuO2 with aqueous multivalent (Be2+ and Al3+) sulfate electrolytes for asymmetric supercapacitors
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Juan C. Icaza, Ramesh K. Guduru

    Ruthenium oxide (RuO2) is one of the most investigated electrode materials due to its unique characteristics, such as high reversibility and high capacitance, etc. However, it has always been tested with univalent electrolyte systems for charge storage applications. In contrast, here, for the first time, we examined electrochemical characteristics of a nanocrystalline RuO2 using multivalent aqueous 0.5 M BeSO4 (pH-2.2) and 0.167 M Al2(SO4)3 (pH-2.8) electrolytes and then compared the performance with the data obtained using a commonly investigated univalent 0.5 M H2SO4 (pH-1.08) electrolyte. The asymmetric two electrode systems of RuO2 Vs. activated carbon (AC) showed maximum capacitances of 397 (at 3.12 Ag−1) and 189 Fg−1 (at 3.65 Ag−1) with Be2+ and Al3+ sulfate electrolytes, respectively, reflecting both the double layer and pseudo capacitance mechanisms for charge storage. These studies present an advantage of multivalent electrolytes for RuO2 based charge storage applications.

    更新日期:2017-11-17
  • Sintering of a hypoeutectic high chromium cast iron as well as its microstructure and properties
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Jinghong Gu, Pingan Xiao, Jianyong Song, Zhihua Li, Ruiqing Lu

    A hypoeutectic high chromium cast iron (HCCI) was fabricated by super-solidus liquid phase sintering (SLPS) technology with gas atomized powders as raw materials. The effects of sintering parameters on densification, microstructure evolution and mechanical properties of the alloy were investigated systemically. The results showed that samples with full density could be fabricated and sintering temperature window suitable for SLPS is around 20 °C. The X-ray diffraction (XRD) revealed that the hypoeutectic HCCI mainly consists of martensite matrix and M7C3 carbide as well as small amount of austenite, and optical metallographic analysis showed that M7C3 carbides are of crystal square bars with uniform distribution in the matrix. As sintering temperature or holding time is raised, both grain and carbide are gradually coarsen, while the strength and toughness of the alloy increase at first and then decline. The mechanical properties of sintered hypoeutectic HCCI in an optimized sintering process were of hardness HRC63, bending strength 2241 MPa, and impact toughness 8.0 J/cm2. A model about microstructure evolution in sintered hypoeutectic HCCIs has been proposed.

    更新日期:2017-11-17
  • Influence of Mn-substituted on the magnetic and thermal properties of TbCrO3
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Megha Vagadia, S. Rayaprol, A.K. Nigam

    Studies on the Mn-substitution induced modification in the structural, thermal, magnetic and magnetocaloric properties of TbCrO3 orthochromite are presented. The phase formation and purity of the samples were examined by analyzing X-ray diffraction (XRD) patterns. Magnetization measurements as a function of temperature reveal the antiferromagnetic ordering of Cr3+ spins (TN1) at ∼ 157 K and Tb3+ spins (TN2) ∼ 5 K for TbCrO3 sample. The substitution of Mn-atoms at Cr-site results in a decrease in TN1 whereas an increase in TN2. The isothermal magnetization measurements reveal the presence of metamagnetic transition at 5 K and 2 K. Results of, ac and dc magnetization and isothermal remnant magnetization suggest a spin-glass like ordering below TN2. The heat capacity measurements show peaks corresponding to the magnetic ordering of Cr3+ and Tb3+ spins. The temperature variation of magnetic entropy change (-ΔSm) for different ΔH suggests the presence of the magnetocaloric effect in the vicinity of TN2. It is found that values of -ΔSm decreases with the increase in Mn-substitution. Present results have been understood in terms of modifications in magnetic exchange interactions introduced by the Mn-substitution at Cr-site.

    更新日期:2017-11-17
  • Enhanced nonlinear optical activity and Ca2+-conductivity in Са10.5-xPbx(VO4)7 ferroelectrics
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Sergey Yu. Stefanovich, Daria A. Petrova, Vladimir A. Morozov, Elena A. Fortalnova, Dmitry A. Belov, Dina V. Deyneko, Oksana V. Barishnikova, Alexei A. Belik, Bogdan I. Lazoryak

    Са3(VO4)2-based compositions are considered as promising multifunctional materials combining ferroelectric, optical nonlinear, and Ca2+-ion conductive properties. Their ferroelectric Curie points stretch from minimal for β-Ca3(PO4)2 type compounds temperatures of about 800 K to very high. Investigated in this paper lead substitution for calcium is as a factor controlling ferroelectricity, ionic-conductivity and non-linear optical activity in Ca3(VO4)2-based materials. Polar phase containing powders and ceramics in Ca10.5-xPbx(VO4)7 system are synthesized for 0 ≤ x ≤ 9.5 by the solid state method, and structurally characterized with X-ray powder diffraction and transmission electron microscopy. Dielectric properties, differential thermal analysis and second harmonic generation (SHG) evidence that Ca10.5-xPbx(VO4)7 solid solution (0 ≤ x ≤ 4.5) belongs to whitlockite-type ferroelectrics. SHG activity strongly increases with x up to its maximum at x = 4.5, where it has a record value among all studied before Ca3(XO4)2-related compounds (X = P,V). Ferroelectric Curie temperatures of Ca3(VO4)2 drops from its known value Tc = 1368 K (x = 0) to 770 K (x = 4.5). Crystal symmetry at Tc changes from R3c to View the MathML source R 3 ¯ c . After this, one more phase transition to the symmetry R View the MathML source 3 ¯ m takes place, its temperature bringing down from 1387 K (x = 0) to 804 K (x = 4.5). Ferroelectric and non-ferroelectric phase transitions in the Са10.5-xPbx(VO4)7 are separated by a broad interval Δ Δ T = 20–50 K and both classified as first-order transformations going in the sequence: R3c ↔ View the MathML source R 3 ¯ c ↔ View the MathML source R 3 ¯ m . Structures of Са10.5-xPbx(VO4)7 compositions with x = 0.5–4 were refined by the Rietveld method and peculiarities of the Pb2+cations distribution in the M1 - M2 and M3 sites of β-Ca3(PO4)2-type structure are discussed regarding the optical nonlinear, ferroelectric and ion-conductive properties. Manifold increased Ca2+- ion conductivity of Са10.5-xPbx(VO4)7 in vicinity of 1000 K at x = 4–4.5 in combination with their ferroelectric and optical nonlinear properties extends applicability of ion-exchange technologies to new promising materials.

    更新日期:2017-11-17
  • Creep deformation of a nickel-based single crystal superalloy under high stress at 1033 K
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Dongqing Qi, Dong Wang, Kui Du, Yang Qi, Langhong Lou, Jian Zhang, Hengqiang Ye

    The microstructure of a nickel-based single crystal superalloy has been investigated after creep deformation at 1033 K under stress up to 850 MPa. High density of stacking faults are formed in γ′ precipitates during the creep deformation. At 700 MPa and 850 MPa, bi-directional stacking faults are observed. These stacking faults are induced by the movement of a/3<112> partial dislocations. Two formation mechanisms of a/3<112> partial dislocations, reaction and dissociation mechanisms, are simultaneously observed in this alloy after deformation. The proportion of a/3<112> dislocations formed by the dissociation mechanism increases as the applied stress increases. The primary creep strain of this alloy is 2.45% at 850 MPa, which may be attributed to the combination of these two mechanisms.

    更新日期:2017-11-17
  • K2[B3O3(OH)5]: A new deep-UV nonlinear optical crystal with isolated [B3O3(OH)5]2- anionic groups
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Qian Wang, Chensheng Lin, Guohong Zou, Mengjiao Liu, Daojiang Gao, Jian Bi, Ling Huang

    A new noncentrosymmetric material, namely, K2[B3O3(OH)5] has been obtained by conventional solution reaction. It crystallizes in the orthorhombic space group Ama2 (no. 40). In the structure of K2[B3O3(OH)5], the BO2(OH) triangles and BO2(OH)2 tetrahedra are linked via sharing corners forming the isolated [B3O3(OH)5]2- anionic groups with no dangling bonds in oxygen atoms. And K2[B3O3(OH)5] is the first synthetic noncentrosymmetric borates with [B3O3(OH)5]2- anionic groups. Powder second-harmonic generation (SHG) using the Kurtz−Perry technique showed that K2[B3O3(OH)5] is type I phase-matchable, and the measured SHG coefficient is 0.32 times that of KH2PO4. The UV transmittance spectroscopy measurement indicated that the UV absorption edge was below 200 nm, suggesting that K2[B3O3(OH)5] might be a promising deep-UV nonlinear optical material. Band structure and optical property calculations based on DFT methods were also performed.

    更新日期:2017-11-17
  • Electrodeposited tungsten oxide films onto porous silicon for NO2 detection at room temperature
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Dali Yan, Shenyu Li, Shiyu Liu, Ming Tan, Meng Cao

    Here we prepare a composite of tungsten oxide films/porous silicon (WO3/PS) hybrid structure synthesized by electrochemical deposition of WO3 films onto p-type PS with subsequent annealing process in air. The obtained WO3/PS products were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy (RS). The gas-sensing properties of WO3/PS composite to NO2 ranging from room temperature (RT, ∼25 °C) to 200 °C were studied. The result indicated that all the WO3/PS gas sensors showed typical p-type semiconductor behavior and had an optimal working temperature of RT. Furthermore, compared with PS, the proper deposited WO3/PS composite exhibited a higher gas response, shorter response-recovery time, good repeatability and selectivity toward NO2 gas at RT. This improvement probably owing to the heterojunction effect and its unique microstructure properties. In addition, the possible NO2-sensing mechanisms were also discussed in this paper.

    更新日期:2017-11-17
  • Ethylenediamine-assisted synthesis of microsized cobalt sulfide as advanced anode materials for sodium ion batteries
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Xue Liu, Hua Ma, Qiongzhen Liu, Yuedan Wang, Zhentan Lu, Mufang Li, Jianbin Wang, Dong Wang

    Microsized cobalt sulfide is prepared via a solvothermal method in ethylenediamine solution by using CoCl2·6H2O as cobalt resource and thioacetamide as the sulfiding reagent. By varying the reaction parameters, CoS-24 and CoS-48 are obtained at 180 °C for 24 h and 48 h, respectively. Scanning electron microscopy and transmission electron microscopy images reveal that the microstructures are both assembled by nanosheets with width in the range of 130–160 nm and thickness of 30–50 nm. When used in SIBs, the more dispersed CoS-48 electrode exhibits superior sodium storage performances than that of CoS-24. For CoS-48, a specific capacity of 753 mAh g−1 is delivered at the current density of 100 mA g−1 in the potential window of 0.1–3.0 V. Moreover, 392 mAh g−1 can still be maintained at the current density of 1000 mA g−1 after 200 cycles, corresponding to 80% retention. These results demonstrate the potential of the carbon-free cobalt sulfide as high performance anode materials for energy storage.

    更新日期:2017-11-17
  • Investigation of thermal and mechanical properties of Cu-Al alloys with silver addition prepared by powder metallurgy
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Ghulam Abbas Gohar, Tareq Manzoor, Asad Naeem Shah

    In this study, Cu-10 wt.% Al-X wt.% Ag alloys (X = 0.0, 2.0, 2.5, 3.0, 4.0, 5.0, 5.5, 6.0) were synthesized through Powder Metallurgy. The effect of silver addition on microstructural, thermal and mechanical properties of the prepared alloys were investigated by using Scanning Electron Microscopy (SEM), Energy Dispersion Spectroscopy (EDS), X-rays Diffractometry (XRD), Transient Plane Source method (TPS), Rockwell hardness tester and Universal testing Machines. The XRD result of raw materials such as pure copper, pure aluminum, pure silver were qualified through JCPDS cards, and subsequently quantified. The microstructural analysis of all samples was carried out, with heating rate of 5 ̊C/min and annealed at room temperature. The results indicated that presence of silver in Cu-Al alloy offered better hardness up-to 3%Ag and compression strength increases up to 2%Ag in Cu-10 wt. %Al alloys which shows intermetallic structure in XRD analysis. Thermal conductivity and thermal diffusivity of the prepared alloys are investigated with help of TPS method in this work. It is observed that both thermal conductivity and thermal diffusivity increased with the increase of silver contents in the alloys owing to higher conductive behavior of silver.

    更新日期:2017-11-17
  • WO3-SnO2 nanosheet composites: Hydrothermal synthesis and gas sensing mechanism
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Mingli Yin, Yao Yao, Haibo Fan, Shengzhong Liu

    WO3-SnO2 nanosheet (NS) composites consisting of inner WO3 nanosheets surrounded by outer mixed phase SnO2 nanoparticles (NPs) were successfully synthesized by a simple two-step hydrothermal method. The density of SnO2 NPs on WO3 NSs can be controlled from sparse discrete state to complete shell structure by varying the amount of tin precursor. Apparent interface state density dependent gas sensing responses were observed for the WO3-SnO2 nanocomposites. The response of the WO3-SnO2 nanocomposites coated with complete SnO2 shell to 50 ppm acetone vapor is as high as 32.1, ∼10 times higher than that of the pristine WO3 NS sensor, with a response time less than 2 s. The improvement in response and selectivity of the WO3-SnO2 nanocomposite sensors upon exposure to acetone molecules can be mainly attributed to the multifunctional interfaces between WO3 NSs and SnO2 NPs, exposed special facets of WO3 NSs, core-shell type nanostructures as well as the special physical and chemical properties of acetone molecules.

    更新日期:2017-11-17
  • Tunable NIR long persistent luminescence and discovery of trap-distribution-dependent excitation enhancement in transition metal doped weak-crystal-field CaZnGe2O6
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    Ru Kang, Jianmin Nie, Xiaojing Dou, Shaoan Zhang, Guifang Ju, Li Chen, Yihua Hu, Yang Li

    A long persistent phosphor (LPP) CaZnGe2O6: Cr3+ has been rationally designed and successfully fabricated. The weak crystal field surrounding Cr3+ activator enables an afterglow emission band 700–1200 nm almost covering the biological transparency window. In this work, a feasible route of Mn2+ codoping is suggested to precisely control the spectral shape, which further meets the demand of wide range and steady response to different photo-detectors in the biological transparency window. An interestingly synchronous improvement of persistent duration of Cr3+ and Mn2+ emission center is discovered in this process. Meanwhile, this codoping technique also achieves the enhancement of afterglow-excitation intensity. The design approach employed here inherently involves the ingenious engineering for combining the isolated traps in Cr3+, Mn2+ singly doped LPP, and for forming a continuous-distribution trap in Cr3+, Mn2+ co-doped LPP according to the thermoluminescent measurement. The highlighted redeployment of trap distribution will opens a vista of potential avenues for LPP design, afterglow mechanism analysis and functionalized application of bio imaging.

    更新日期:2017-11-17
  • First-principles study of structural, electronic, energetic and optical properties of substitutional Cu defect in Li2B4O7 scintillator
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-15
    C. Santos, A.F. Lima, M.V. Lalic

    Quantum-mechanical effects of incorporation of the Cu ions at the Li sites in Li2B4O7 crystal matrix are investigated by means of first-principles calculations on density-functional-theory level. The isolated Cu defect is considered in various charge states with objective to simulate situations of the capture of an electron or a hole. In all cases the defective crystal is computationally relaxed, Cu-O chemical bonds carefully analyzed and local structure around the defects precisely determined. It is found that the defect vastly perturbs its O neighborhood and the Cu itself exhibits significant off-site dislocation from initial Li position in its Cu1+ and Cu0 charge states, while the Cu2+ stabilizes approximately at the Li site. Resulting defect formation energies demonstrate that the Cu1+ and Cu0 centers are the most stable ones. Electronic structure calculations reveal that the Cu introduces its d- and s-states within the gap and their energies and occupation depend strongly on the charge state of the defect. Experimental optical absorption spectra are well reproduced by the sole Cu1+ defect spectra, leading to the conclusion that in the as-grown material just Cu1+ centers are formed, with possible presence of small concentration of the Cu2+ centers. In the case of irradiated material, present study predicts formation of the interstitial Cu0 defects, whose presence should significantly change the optical absorption and emission of the material.

    更新日期:2017-11-17
  • Cd-doped SnO2/CdS heterostructures for efficient application in photocatalytic reforming of glycerol to produce hydrogen under visible light irradiation
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Tuany N.S. Trindade, Luciana A. Silva

    A series of mixed oxide (CdySn(1-y)O2) were synthesized by Pechini method followed by ion exchange with sulfide ions and heat treatment in nitrogen atmosphere to reach Cd-doped SnO2 and binary (Cd-SnO2/CdS) and ternary (Cd-SnO2/CdO/CdS and SnO2/CdO/CdS) composites. These materials have demonstrated able to absorb visible light and some of them are actives in photocatalytic reforming reaction of glycerol aqueous solution to produce hydrogen. The materials obtained in each step of the synthesis were characterized using different techniques (XRD, Raman, DRS, MEV and EDX). The influence of the calcination temperature in the ion exchange step, as well as the cadmium content in the formation of oxides and composites were investigated. A type II heterostructure, Cd(7%)-SnO2/(CdS)0.3, was obtained when the start solution had the same amount of cadmium and tin and this composite has demonstrated the best photocatalytic activity in hydrogen production, around 290 μmol g−1 h−1. This value is very close to the obtained with commercial CdS, but with a great advantage, it has a lower content of cadmium, being less toxic.

    更新日期:2017-11-15
  • Electric transport and enhanced dielectric permittivity in pure and Al doped NiO nanostructures
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    M. Naseem Siddique, Ateeq Ahmed, P. Tripathi

    In this paper, we have studied the electrical and transport properties of Ni1-xAlxO(x = 0.00, 0.01, 0.03, 0.05) nanoparticles which have been synthesized through wet chemical route via a sol-gel method at 600 °C. The XRD patterns reveal that the NiO nanoparticles have a cubic polycrystalline crystal structure with average crystallite size ranging from 18.20 nm to 9.54 nm and 17.20 nm to 11.53 nm which are calculated by Debye-Sherrer and William Hall method, respectively. The morphology and size of the nanoparticles have also been observed by Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) for pure and Al-doped (5%) NiO nanoparticles. We have also studied the DC resistivity and activation energy (0.19 eV-0.49 eV) of our samples using two probe measurement. It is observed that pure and Al-doped NiO nanoparticles exhibit a giant value of dielectric permittivity (103-104). The high value of dielectric constant of Al-doped NiO nanoparticles depends on Al concentration and can be ascribed to the thermally activated and Maxwell–Wagner polarization mechanism.

    更新日期:2017-11-15
  • Local structure evolutions of metallic glasses during shear deformation investigated by computer simulations
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    M.H. Yang, J.H. Li, B.X. Liu

    Based on the experimental data and first-principle calculations, the newly constructed long-range empirical potential was first developed for the Ni-Hf-Mo system. Taking the realistic interatomic potential as the starting point, the atomic-level structure and its correlation with the shear deformation process of the Ni-Hf-Mo metallic glasses were investigated and characterized by atomic simulations and various analysis methods. Interestingly, the appropriate amount of Mo addition to Ni-Hf alloys could enhance the intrinsic strength, while reducing the plasticity. By monitoring atomic-scale structure during the shear deformation, local shear behaviors are closely correlated with the structural and mechanical response. In addition, the connectivity degree of the spatial network could have a considerable effect on the structure and performance of metallic glasses.

    更新日期:2017-11-15
  • Microstructural and electrochemical comparison between TiN coatings deposited through HIPIMS and DCMS techniques
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Hasan Elmkhah, Faridreza Attarzadeh, Arash Fattah-alhosseini, Kwang Ho Kim

    Recently, high power impulse magnetron sputtering (HIPIMS) technique has been widely applied to deposit hard coatings such as Ti-based coatings on industrial tools due to its strong merits of high coating density, smooth surface, and excellent adhesion. In this work, TiN (Titanium Nitride) nanostructured coatings were deposited by two different methods (HIPIMS and DCMS techniques) with constant processing parameters and their electrochemical behaviors were investigated in a 3.5% NaCl solution. X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), and atomic force microscopy (AFM) were used to characterize and evaluate the coatings composition, surface morphology, and surface roughness, respectively. It is found that the preferred orientation depends on the applied deposition technique. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy (EIS) were used to compare the electrochemical responses of these nanostructured coatings in 3.5% NaCl solution. The results indicate that HIPIMS-TiN coating is of well-defined denser nanocrystalline structure, which not only is smoother but also has a superior passivation and better protects the substrate against the ingress of aggressive anions.

    更新日期:2017-11-15
  • Effects of process parameters of vacuum pre-oxidation on the microstructural evolution of CoCrAlY coating deposited by HVOF
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Yujun Han, Zhiying Zhu, Baosen Zhang, Yajie Chu, Yan Zhang, Jinkai Fan

    The CoCrAlY coatings deposited using the high velocity oxygen fuel process (HVOF) onto the Inconel 718 superalloy were employed by three different vacuum pre-oxidation heat treatments, and subsequently, the specimens were subjected to isothermal oxidation exposure testing in air at 1050 °C for up to 100 h. The spinel oxides were found in the CoCrAlY coatings during the high velocity oxygen fuel process, and subsequently, after isothermal oxidation exposure in air, both the spinel and CoO oxides were formed in the TGO of the NVHT specimen. The evolution of both the phase transformation and the thermally grown oxides' (TGO) growth rate could be significantly influenced by adjusting certain process parameters of vacuum pre-oxidation heat treatments. The TGO of the VHT specimen was predominantly composed of θ-Al2O3 and α-Al2O3; however, Co(Cr, Al)2O4 and alumina were observed in the TGO of the VHT950 and VHT1000 specimens. The θ-Al2O3 to α- Al2O3 phase transformation in the TGO of the VHT specimen could be delayed after isothermal oxidation exposure. The TGO growth rate was significantly suppressed after the vacuum pre-oxidation heat treatments, and the order of the TGO growth rate was as follows: NVHT<VHT950<VHT<VHT1000. The tensile stress at the alumina area of the TGO in the VHT and VHT950 specimens reduced considerably compared to that in the NVHT specimen, and finally, for the VHT1000 specimen, the tensile stress turned to compressive stress. The elemental interdiffusion behaviour between the HVOF-coating and nickel-based superalloy was characterized, and the diffusion activation energy of cobalt, aluminium and chromium were attempted to be estimated.

    更新日期:2017-11-15
  • Novel Li4Ti5O12/Ti3C2Tx nanocomposite as a high rate anode material for lithium ion batteries
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Changjie Shen, Yule Cao, Aiguo Zhou, Qianku Hu, Gang Qin, Zhengpeng Yang, Xuqing Liu, Libo Wang

    Li4Ti5O12/Ti3C2Tx nanocomposite was prepared by high temperature calcination method using Ti3C2Tx and LiOH as raw materials. The developed nanocomposite demonstrated excellent rate capability and capacity retention. It delivers a reversible capacity of 236 mAh/g at a current density of 50 mA/g and had a relatively high specific capacity of 500 mA/g and 4000 mA/g, which is significantly better than pure Ti3C2Tx and LiTiO2. The exceptional electrochemical performance of Li4Ti5O12/Ti3C2Tx electrode can be attributed to the improvement of electronic conductivity by Ti3C2Tx and nano-size of Li4Ti5O12 particles in the Li4Ti5O12/Ti3C2Tx composite.

    更新日期:2017-11-15
  • Growth, structure and characterization of physico-chemical and magnetic properties of CdCr2Se4:Mn single crystals
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Izabela Jendrzejewska, Tadeusz Groń, Joachim Kusz, Jerzy Goraus, Andrzej Kita, Zoia Barsova, Andrzej Ślebarski, Marcin Fijałkowski, Ewa Pietrasik, Paweł Zajdel, Henryk Duda

    Crystal structure, magnetic and specific heat measurements, electrical conductivity, as well as DSC/TG measurements for single-crystalline CdxMnyCrzSe4 (where x + y + z ≈ 3) spinels are presented. The electrical conductivity and dc magnetic susceptibility measurements exhibit thermally activated semiconducting properties and ferromagnetic (FM) order for all compositions below the Curie temperature TC = 130 K, respectively. The long-range FM interactions, defined by the Curie temperature, do not substantially depend on the manganese content, and the nearest neighbour FM interactions, represented by the positive value of the Curie-Weiss temperature, decrease from 183 K to 156 K. Hysteresis loops of all crystals have a very small coercive field (∼18 Oe) and remanence (∼0.09 μB/f.u.) with full saturation above 10 kOe. These effects are interpreted in terms of the superexchange integrals for the first two coordination spheres including spin defects.

    更新日期:2017-11-15
  • Ni–TiN and Ni-Co-TiN composite coatings for corrosion protection: Fabrication and electrochemical characterization
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    A. Hefnawy, N. Elkhoshkhany, A. Essam

    The Ni coating is one of metal coatings that are commonly deposited by electrodeposition for corrosion inhibition. The addition of particles such as TiN and Co in the Ni coating modifies coating properties. In the present work, Ni–TiN and Ni-Co-TiN composite coatings with different amounts of TiN microparticles were prepared by using the electrodeposition technique. Different characterization methods including X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX) and Vicker's microhardness tester were used to investigate the effects of adding cobalt and TiN microparticles on the surface morphology, grain size, and hardness of the Ni-TiN and Ni-Co-TiN composite coatings. The electrochemical corrosion behavior of the composite coating was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in NaCl solution. The addition of cobalt in the Ni–Co-TiN composite coating resulted in the grain size decrease (≈41.8 nm) and hardness increase. The microstructure analysis showed that, the (111) planes were the close packed planes compared with the (200) planes. Thus, with adding Co and TiN particles the (200) texture changed to the (111) texture. The electrochemical analysis showed that, the anti-corrosion behavior of the Ni-Co-TiN composite coating significantly enhanced by adding Co and TiN particles.

    更新日期:2017-11-15
  • Controlled synthesis of manganese tungstate nanorods for highly selective NH3 gas sensor
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Do Dang Trung, Nguyen Duc Cuong, Khuc Quang Trung, Thanh-Dinh Nguyen, Nguyen Van Toan, Chu Manh Hung, Nguyen Van Hieu

    In this paper, single-crystalline MnWO4 nanorods were prepared through a facile single-step hydrothermal approach and used for gas sensing. The morphology and phase of the products were characterized in detail through transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and elemental dispersive spectrum analyses. Results showed that the as-prepared MnWO4 nanorods possess uniform shape with their length of 250–300 nm and width of 20–30 nm. The nanorods were used to fabricate sensors for detecting reducing gases such as NH3, H2 and CO and evaluate gas sensing properties. The sensors exhibit not only good response and fast response time, but also almost full recovery and good stability, to NH3 gas.

    更新日期:2017-11-15
  • Spectral attributes of Eu3+ doped borotellurite glasses containing Mn3O4 nanoparticles
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Siti Maisarah Aziz, M.R. Sahar, S.K. Ghoshal

    Glass samples of composition (59-x)TeO2-30B2O3-10MgO-1Eu2O3-xMn3O4, where x = 0, 0.5, 1.0, 1.5 and 2.0 mol % were prepared using melt quenching method. The Mn3O4 nanoparticles (MNPs) concentration dependent spectral properties were determined. XRD pattern verified the amorphous nature of prepared glasses and the presence of MNPs inside the glass matrix. TEM images revealed the nucleation of MNPs of average diameter 15 ± 1 nm. High resolution TEM data confirmed the NPs growth along (1 0 3) crystal plane orientation having lattice spacing ≈ 0.276 nm. Raman spectra displayed a shift in the vibrational modes of TeO4 and TeO3 units and thereby confirmed the alteration in the glass network structures mediated by NPs. The bonding characteristics of Eu3+ and ligand field parameters were evaluated. The observed increase in the network covalency was attributed to the MNPs assisted changes in the electron distribution. The emission spectra of glass samples revealed five prominent peaks centred at 578 nm, 591 nm, 610 nm, 651 nm and 700 nm which were assigned to the transition from 5D0→7FJ (J = 0, 1, 2, 3, 4) states of Eu3+ ion. Judd-Ofelt intensity parameters were calculated. The prepared glasses exhibited paramagnetic behaviour. EPR spectra verified the predominant occurrence of Mn2+ with effective g ≈ 2.0.

    更新日期:2017-11-15
  • Facile preparation of nanoscale silicon as an anode material for lithium ion batteries by a mild temperature metathesis route
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Kui Liang, Hailin Yang, Wenxun Guo, Jianlong Du, Lingyun Tian, Xiaofeng Wen

    Silicon has been regarded as a promising alternative anode material for next-generation lithium ion batteries (LIBs) due to its high theoretical specific capacity of 3590 mAh g−1 (Li3.75Si formed at room temperature). In this work, nanoscale silicon has been synthesized via a simple and effective metathesis reaction in which SiCl4 is the silicon source and Zn is the reductant and solvent, at a mild temperature of 500 °C. The preparation process is very simple, facile and low-cost. The as-prepared silicon particles are spherical with a diameter of 150–200 nm, and the delithiation capacity of the nanoscale silicon can reach 1747.7 mAh g−1 at a current density of 0.2 A g−1.

    更新日期:2017-11-15
  • Investigations on magnetic properties of Cr-doped LiZnP by first principle calculations
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Meng-Xia Wang, Hua-Long Tao, Juan Cai, Yu-Xin Wang, Ming He, Bo Song, Tian-Bo Yang, Zhi-Hua Zhang

    The electronic structures and magnetic properties for Cr doped LiZnP system are studied by first principles calculations. The results indicate that Cr doped LiZnP structures with Cr concentration 6.25 at.% favors spin polarized ground states and the system should be magnetic. The magnetic coupling results show that the system exists in the ferromagnetic (FM) stable state and the FM interactions in the Cr-Cr pair can be attributed to the p-d exchange interactions as Cr↑-P↓-Cr↑. VLi act as donor in Li(Zn,Cr)P host, which increasing the carrier concentration and thus lead to the FM state more stable. VZn has less influence on FM stability, and VP weakens FM stability of the system.

    更新日期:2017-11-15
  • Combined effect of process parameters during aluminothermic reaction process on the microstructure and mechanical properties of in situ Al/TiB2 composite
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    A.S. Vivekananda, S. Balasivanandha Prabu, R. Paskaramoorthy

    Al/TiB2 particle reinforced composites were processed through aluminothermic reaction process using potassium hexafluorotitanate (K2TiF6) and potassium tetrafluoroborate (KBF4) salts as precursors and Al (A380) alloy as a matrix material, with different processing conditions such as addition time (AT) of precursors (10 min, 20 min, 30 min), holding time of melt (HT) (20 min, 30 min, 40 min) and melt temperature (700 °C, 750 °C, 800 °C, 850 °C). The combined effect of the process parameters of aluminothemic reaction on the formation of TiB2, size and distribution of TiB2 particles in the microstructure and the mechanical properties of Al/TiB2 composite were studied. The formation of TiB2 particles were confirmed from XRD pattern. The microstructures showed uniform distribution of TiB2 particle in Al matrix in the processing condition: addition time (20 min), holding time (30 min) and melt temperature (800 °C). The hardness and ultimate tensile strength of composite have improved 57%, 59% respectively in this condition. The resultant properties were correlated to the microstructure and process parameters. Coarser particles were formed at a lower addition time (10 min) and holding time (20 min) of precursors with all the processing temperatures.

    更新日期:2017-11-15
  • An evaluation of the B4C formation in sintered ZrB2-SiC ceramic composites at 2100 °C
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Dayang Salyani Abang Mahmod, Amir Azam Khan, Nicolas Glandut, Jean-Claude Labbe

    The present study was concerned with the high temperature sintering behaviour of zirconium diboride ceramics mixed with fine silicon carbide. Zirconium diboride-silicon carbide (ZrB2-SiC) ceramic composites were pressureless sintered at 2100 °C under flowing argon environment, for a hold time of 150 min. The pressureless sintered ZrB2-SiC pellets were characterized for microstructure and phase analysis. The sintered microstructure was observed through Scanning Electron Microscopy (SEM) embedded with Energy Dispersive Spectroscopy (EDS) and different phases were analyzed through X-ray Diffraction (XRD). The investigation revealed the presence of boron carbide (B4C) within the sintered pellets containing 20 mol.% SiC. The B4C was formed during sintering without the presence of any free carbon as part of initial powder mixture. Possible routes to identify and explain the formation of B4C in the absence of free carbon were discussed.

    更新日期:2017-11-15
  • Reduction, sintering and mechanical properties of rhenium-tungsten compounds
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-14
    Chen Lai, Jinshu Wang, Fan Zhou, Wei Liu, Naihua Miao

    Porous tungsten-rhenium powders with various compositions were prepared by a spray drying method combined with two-stage hydrogen reduction. Using the W-Re powders, W-Re alloy substrates were successfully fabricated by high temperature sintering under the protection of hydrogen. X-ray diffraction analysis, thermogravimetric analysis and temperature programmed reduction were carried out to study the reduction behavior of the tungsten and rhenium containing precursor powders prepared by spray drying. It reveals that the first stage reduction temperature has a significant impact on the microstructure of the W-Re powders. Rhenium in the mixed powder affects the reduction behavior of WO3. Properties of the W-Re alloy matrices, including relative density, open porosity, mechanical characteristics and electronic structures are also investigated. The first-principles calculation method proved that rhenium reduces the reduction barrier of WO3, and W-Re compounds obtained in this study are suggested to be a ductile material.

    更新日期:2017-11-15
  • Large reversible normal and inverse magneto-caloric effects in the RE2BaCuO5 (RE = Dy and Er) compounds
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Lingwei Li, Kunpeng Su, Dexuan Huo

    The magneto-caloric effect (MCE) in the polycrystalline rare-earth cuprates Dy2BaCuO5 and Er2BaCuO5 has been researched. An inverse MCE under low magnetic field changes (ΔH) and at low temperatures together with a large normal reversible MCE under high ΔH was observed for the both compounds. These behaviours are corresponding to the fact of AFM (antiferromagnetic) ground state and the field-induced metamagnetic transition (first order) from AFM to FM (ferromagnetic) state in Dy2BaCuO5 and Er2BaCuO5 compounds. For the ΔH of 0–7 T, the values of −ΔSMmax (maximum magnetic entropy change), RCP (relative cooling power) and RC (refrigerant capacity) are found to be 8.3 J/kg K, 204 J/kg and 153 J/kg for Dy2BaCuO5, and to be 9.6 J/kg K, 230 J/kg and 176 J/kg for Er2BaCuO5, respectively.

    更新日期:2017-11-14
  • Effect of vapor deposition in shrouded plasma spraying on morphology and wettability of the metallic Ni20Cr coating surface
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Jie Li, Cheng-Xin Li, Guan-Jun Yang, Chang-Jiu Li

    A Ni20Cr coating surface with a micro-nano hierarchical structure was successfully prepared by shrouded plasma spraying method in the present study. By adjusting the spraying parameters to control the heating degree of the powder particles and using a designed shield deposition method, we confirmed that the nanostructures were the products of vapor deposition by vaporization of the material during the spraying. In addition, an interesting phenomenon was found that, without any additional chemical modification, the surface with micro-nano structures underwent a wettability transition from super-hydrophilicity to super-hydrophobicity during the storage in air. The results show that the selective spontaneous adsorption of the nanostructures can effectively reduce the surface free energy. The nanostructures deposited on the top of the surface made the surface form a unique hierarchical structure, which can effectively reduce the contact area of the droplet with the surface. Nanostructures affected the wettability of the coating surface both in the chemical composition and the structural aspects, which demonstrated that they were the key to obtaining super-hydrophobic property on the coating surface.

    更新日期:2017-11-14
  • Corrosion resistance of Fe77Mo5P9C7.5B1.5in-situ metallic glass matrix composites
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Arman Zarebidaki, Amir Seifoddini, Taher Rabizadeh

    A novel in-situ Fe-based metallic glass matrix composite with a composition of Fe77Mo5P9C7.5B1.5 was developed by injection casting. Scanning electron microscopy (SEM) and X-Ray diffraction (XRD) confirmed the presence of α-Fe dendrites as a secondary phase across the glassy matrix. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods were utilized to study the corrosion behavior of Fe77Mo5P9C7.5B1.5 in deaerated 1 M HCl solution and to compare it with that obtained for AISI Type 301 stainless steel as a Fe-base crystalline alloy. The electrochemical characterizations showed the lower corrosion resistance of the synthesized Fe-MGMC which was due to the galvanic cells formed between α-Fe dendrites and the glassy matrix. Energy dispersive spectroscopy (EDS) analysis of the corroded Fe-MGMC revealed the role of B and C in forming a passive layer mirrored by a stable vertical line in the anodic part of the corresponding potentiodynamic polarization curve. Although, the stainless steel sample yielded a lower corrosion rate and a higher charge transfer resistance, a passive-transpassive transition was observed in its anodic polarization curve confirming the lower stability of the passive film formed on the specimen. The preferential dissolution of α-Fe dendrites and formation of micro-sized pits were the characteristic corroded surface morphology of Fe77Mo5P9C7.5B1.5 and AISI Type 301 stainless steel, respectively.

    更新日期:2017-11-14
  • Effects of olefin and acid stabilizer on the properties of insoluble sulfur
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Yan-xia Wang, Feng Li, Feng Wang, Yan-feng Wang, Ning Zhao, Fu-kui Xiao

    The effects of the polymerization conditions on the yield of insoluble sulfur were investigated by using olefin, such as the 1,-dodecene, 1,-tetradecene, 1,-octadecene as well as acids, such as the salicylic acid, lauric acid and the oleic acid as polymerization stabilizers. The properties of the as-prepared insoluble sulfur were characterized by micro-Raman spectrometer and differential scanning calorimetry (DSC). The results demonstrated that both the olefin and acid stabilizers could couple with the end groups of the IS, thus improved the thermal stability of the IS, and the olefin stabilizers were superior to the acid stabilizers. The stabilizing effect of oleic acid was the best for the acid stabilizers, and the C<img border="0" alt="double bond; length as m-dash" src="https://cdn.els-cdn.com/sd/entities/dbnd">C in the oleic acid played a crucial role in the stabilization of the IS.

    更新日期:2017-11-14
  • Controlled synthesis of NiCo2S4 hollow spheres as high-performance electrode materials for supercapacitors
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Kangqiang Liang, Weidong He, Xiaolong Deng, Hong Ma, Xijin Xu

    Nickel cobalt sulfides (NiCo2S4) with different morphologies have been synthesized and used as pseudocapacitive materials. Particles, sheets and hollow spheres can be easily synthesized with different components of reagents or chemical reaction time. Benefits from the hollow structure, the electrolyte can diffuse easily into active material and result in a lower resistance. The electrochemical performances of NiCo2S4 depend on the morphologies, among which the hollow NiCo2S4 spheres exhibit the highest specific capacitance of 756 Fg−1 at 1 Ag−1, and longer cycle stability. This method may give some suggestion to synthesis of hollow particles and enhancement of electrochemical capacitors.

    更新日期:2017-11-14
  • The evolution and effects of second phase particles during hot extrusion and re-extrusion of a NiTi shape memory alloy
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Jiao Luo, Wan-jun Ye, Xiao-xiao Ma, John O. Bobanga, John J. Lewandowski

    Second phase particles (SPPs) that are formed during melting process have a significant effect on the hot extrusion and re-extrusion processes of NiTi. In the present work, the evolution of Ti4Ni2Ox (with x ≤ 1) particles during hot extrusion and re-extrusion of near equiatomic Ti-50.6 at.% Ni billets, and their effects on the surrounding matrix microstructure were studied using OM, SEM, TEM and EBSD. The analyses indicate that Ti4Ni2Ox (with x ≤ 1) are the particles that precipitate in the austenite matrix. After hot extrusion and re-extrusion, some particles are elongated and preferentially oriented along the ED. Eventually, these elongated particles are located at the grain boundaries. The size distribution of the SPPs is non-uniform after the first hot extrusion, and this non-uniformity increases after re-extrusion. The presence of non-deforming SPPs produces inhomogeneous deformation with a sharp increase in dislocation density in the surrounding matrix. This is shown to exert a profound effect on the processes of recovery and recrystallization for the surrounding matrix.

    更新日期:2017-11-14
  • Generation of palladium silicide in the PdAu-SiO2 nanocomposites during heating in hydrogen
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Monika Radlik, Wojciech Juszczyk, Krzysztof Matus, Tomasz Szumełda, Alicja Drelinkiewicz, Zbigniew Karpiński

    Heating PdAu nanoparticles deposited on silica in hydrogen results in palladium silicide(s) formation. The degree of palladium extraction by silicon species (ex-silica) is conversely correlated with the gold content in the PdAu alloys. In addition, the phase changes are less extensive than analogous transformations in a previously investigated PdCu-silica composite. Very high temperatures (>550 °C) are required to initiate the transformation of PdAu-SiO2 into respective bulk metal silicide(s), whereas for the PdCu-SiO2 (and Pd-SiO2) similar changes have already been observed at ≤450 °C. Based on existing literature data, it is considered that the reason for this difference is a relative availability of palladium-rich material at the Pd-IB alloy-silica phase boundary. In the case of PdAu, the segregation of gold at the surface is very pronounced, making this alloy more resistant against Pd extraction required for the silicide formation.

    更新日期:2017-11-14
  • Phase transitions and optical absorption edge in (Cu6PS5Br)1-x(Cu7PS6)x mixed crystals
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    I.P. Studenyak, V. Yu Izai, V.I. Studenyak, S.O. Rybak, A.I. Pogodin, O.P. Kokhan, M. Kranjčec

    (Cu6PS5Br)1-x(Cu7PS6)x mixed crystals were grown by chemical vapour transport. Low-temperature isoabsorption and polarisation studies of phase transitions (PT) were performed. A second-order PT characterised by appearance of light transmission in the polariser-crystal-analyser system and a typical knee at the isoabsorption dependence, is clearly revealed. With increasing Cu7PS6 content in (Cu6PS5Br)1-x(Cu7PS6)x mixed crystals, the second-order PT shifts down in temperature range and becomes smeared. Temperature behaviour of the optical absorption edge is studied in the temperature interval 77–320 K. In the superionic phase the absorption edge has an exponential shape and a characteristic Urbach bundle is observed. In the vicinity of the second-order PT, a variation of the Urbach absorption edge parameters and exciton-phonon interaction is revealed. Influence of compositional disordering on the parameters of the Urbach absorption edge, exciton-phonon interaction parameters, and the PT temperatures is studied.

    更新日期:2017-11-14
  • Development and characterization of biaxially-textured lanthanum zirconate film grown on cold-rolled Ni-W substrate by chemical solution deposition
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Angelo Vannozzi, Andrea Augieri, Giuseppe Celentano, Alessandro Rufoloni, Sergey Rubanov, Traian Petrisor

    High temperature superconducting tapes based on cuprate compounds are nowadays available on long lengths by several companies. Because high superconducting properties are strongly influenced by the crystallographic orientation of the superconducting film, and because the appropriate crystallographic orientation is obtained through epitaxial film growth, the development of an oriented template is of crucial technological importance. In the rolling assisted biaxially textured substrate (RABiTS) technique, a strong cube texture is obtained by cold rolling fcc metal tape and high temperature annealing, followed by the deposition of one or more buffer layer by either physical vapor deposition (PVD) or chemical solution deposition (CSD). Using the latter approach, it has been recently shown that it is possible to combine substrate recrystallization and buffer layer growth in a single step if the onset of recrystallization occurs at a temperature lower than buffer layer nucleation. In the present contribution, a detailed investigation of biaxially-oriented La2Zr2O7 (LZO) buffer layer grown on cold-rolled Ni-W substrate by combined EBSD, AFM and TEM analyses is reported. It is shown that it is possible to obtain highly {001}〈110〉-textured LZO film directly on cold-rolled Ni-W substrate. Although some small polycrystalline regions appear, this approach leads to a strong suppression of grain boundary grooving typically occurring in RABiT-type substrates. Further, it is shown that, notwithstanding the microstructure of the metal substrate continues to evolve during the conversion heat treatment, the obtained LZO film is well adherent, without cracks or delamination.

    更新日期:2017-11-14
  • Structural, magnetic, dielectric, vibrational and optical properties of Zr substituted Bi0.90Gd0.10FeO3 multiferroics
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Manoj Kumar, Manisha Arora, Sunil Chauhan, Himanshu Pandey

    We report the evolution of structural, physical and magnetic properties of Zr doped Bi0.90Gd0.10Fe1-xZrxO3, (x = 0.0, 0.03, 0.07 and 0.10) nanoparticles prepared by tartaric acid based sol gel route. Rietveld refinement of X-ray diffraction patterns shows the coexistence of rhombohedral (R3c) and orthorhombic (Pbnm) phase in all the samples. Morphological studies confirm the compositional driven reduction in particle size with increasing Zr concentration due to filling of oxygen vacancies and hence lower grain growth. The magnetic measurements at room temperature indicate that Zr substitution induces weak ferromagnetism and discerns large and non-zero remanant magnetization. Both dielectric constant (ε′) and loss factor (tan δ) of these samples decrease with increasing Zr concentration, indicating improved dielectric properties due to the suppression of oxygen vacancies in co-doped compositions. An anomaly in dielectric constant and dielectric loss is observed in the vicinity of antiferromagnetic Neel temperature. Fourier transform infrared spectra show that the Fe–O bond length decreases with increasing Zr concentration which is consistent with the Rietveld analysis. The UV–visible diffuse reflectance spectroscopy measurements show a significant reduction in the optical band gap value from 2.35 eV to 2.05 eV for Bi0.90Gd0.10Fe1-xZrxO3 samples.

    更新日期:2017-11-14
  • The electrical and electrochemical properties of graphene nanoplatelets modified 75V2O5–25P2O5 glass as a promising anode material for lithium ion battery
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Mesfin A. Kebede, Nithyadharseni Palaniyandy, Rawya M. Ramadan, Eslam Sheha

    A V2O5 anode material significantly challenged on its further development to be used in lithium ion batteries in-terms of its structural degradation, poor cyclability and low conductivity. Thus researchers started to work on composite matrix such as V2O5–P2O5 and in this work we synthesized pristine and 7.5% GNP modified 75V2O5–25P2O5 and used for the first time as anode for lithium-ion batteries; the anodes delivered with corresponding first discharge capacities of ∼1400 and ∼1600 mA h g−1 (almost equal to theoretical capacity of V2O5 1472 mA h g−1 during a fully reduction from V5+ to V0), respectively. The rapid capacity fade was observed in the first few initial cycles (up to 10th cycle) for both materials; however highest discharge capacity of 446 mAh g−1 was retained after 100th cycles for 7.5% GNP modified 75V2O5–25P2O5 than unmodified composite, with the capacity retention of 89% with respect to 10th cycle discharge capacity. The electrical conductivity of 75V2O5–25P2O5 drastically increases with GNP modification. The superior electrochemical performance of 75V2O5–25P2O5–7.5%GNP attributed to the high electronic and ionic conductivity due to graphene nano-platelets.

    更新日期:2017-11-14
  • Enhanced upconversion based on the ultrahigh local field enhancement in a multilayered UCNPs-metamaterial composite system
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Shiping Zhan, Xiaofeng Wu, Chao Tan, Jian Xiong, Shigang Hu, Junshan Hu, Shaobing Wu, Yongyi Gao, Yunxin Liu

    In this paper, we reported a multilayer metamaterial system with ultrahigh absorption, consisting of silver nanoring, upconversion nanoparticles(UCNPs) and silver film, which can dramatically enhance the upconversion emission. A simplified theoretical expression of the upconversion enhancement factor(EFupc) was derived, and the structure parameter and the local field-UCNPs coupling were considered for the EFupc analysis. It was found that the bottom silver film was crucial for the tremendous upconversion enhancement since it gave rise to a pronounced absorption peak and resulted in a strong field confinement of the 980 nm excitation light. Comparing with the nanodisk, the nanoring performed better in enhancing the upconversion, and an enhancement factor of ∼3.2 × 104 was achieved based on the numerical and theoretical analysis. This metamaterial system provided a novel approach in enhancing upconversion, and the research findings could be helpful to the design of biosensor and photovoltaic devices.

    更新日期:2017-11-14
  • Kerosene-fuelled high velocity oxy-fuel (HVOF) spray of Ti2AlC MAX phase powders
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Zheng Zhang, Suo Hon Lim, Jianwei Chai, Doreen Mei Ying Lai, Poh Chong Lim, Augustine Kok Heng Cheong, Shijie Wang, Hongmei Jin, Jisheng Pan

    Kerosene-fueled high velocity oxy-fuel (HVOF) spray was employed to deposit commercial Ti2AlC MAX phase powders onto Inconel 600 substrates. After optimizing three process parameters including flow rates of kerosene and oxygen as well as spray distance, a dense Ti2AlC coating with a very low decomposition was obtained. Using Rietveld phase analysis of the X-ray diffraction pattern, the weight percentage of Ti2AlC in the coating was determined to be 53.0%, which is not only far better than the coating deposited by plasma spray, but also is comparable with the optimum Ti2AlC coatings sprayed by H2-fueled HVOF and cold spray. This optimized Ti2AlC coating was further analyzed by a variety of techniques to probe its surface chemistry, morphology, cross-sectional microstructure, mechanical properties and salt fog corrosion resistance.

    更新日期:2017-11-14
  • Microstructure, hardness and corrosion resistance of Al2CoCrCuFeNiTix high-entropy alloy coatings prepared by rapid solidification
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Xingwu Qiu

    The Al2CoCrCuFeNiTix high-entropy alloy coatings were prepared by laser cladding on Q235 steel surface. The microstructure, hardness and corrosion resistance were investigated by means of scanning electron microscopy with spectroscopy (SEM/EDS), transmission electron microscopy (TEM), micro/Vickers hardness tester and electrochemical workstation. Experimental results show that the cladding coating consists of cladding zone (CZ), bounding zone (BZ) and heat affected zone (HAZ). Al2CoCrCuFeNiTix high-entropy alloy coating was mainly composed of equiaxed grain; the distribution of chemical compositions is uniform. Alloy coating exhibited high hardness due to solid solution hardening and dispersion strengthening effect, the highest surface hardness of 988 HV, about 4.5 times as much as the substrate; the passivation film on Al2CoCrCuFeNiTix high-entropy alloy coating surface made the alloy have excellent corrosion resistance in 0.5 mol/L H2SO4 solution, the alloy coatings were appearing repassivation except Ti1.0 alloy coating. The coating have good corrosion resistance in 3.5% NaCl solution because Ti elements can maintain a stable state of purification. Circular polarization curves show that the Al2CoCrCuFeNiTix high-entropy alloy coating does not appear pitting in 0.5 mol/L H2SO4 and 3.5% NaCl solutions.

    更新日期:2017-11-14
  • Densification and microstructure of magnesium aluminate spinel for adding method of Sc2O3
    J. Alloys Compd. (IF 3.133) Pub Date : 2017-11-13
    Jianhua Liu, Xiaojun Lv, Jie Li, Libo Zhang, Jinhui Peng

    The effect of adding method of Sc2O3 on the densification and microstructure of magnesium aluminate spinel prepared by co-precipitated method was investigated. Sintered products were characterized in terms of densification, phase analysis, quantitative elemental analysis, microstructure and flexural strength. Sintering additives were added in the form of Sc salt and in the form of scandium oxide, respectively. No matter in what way to add, sintering additives exist in the form of Sc2O3. Moreover, incorporating of Sc3+ into the spinel structure increases lattice parameters, which improves the diffusion, mass transfer, and densification. The microstructure of sintered samples with adding Sc salt as a sintering additive is more compact and the grain size distribution is more uniform although their grain size is larger compared with that of sintered samples with adding scandium oxide as a sintering additive. Moreover, the optimum flexural strength (97 MPa) of the sintered products is obtained on sintering at 1650 °C with the addition of Sc salt.

    更新日期:2017-11-14
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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