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  • Magnetostriction of ferromagnetic shape memory alloy Ni2.27Mn0.73Ga studied in magnetic fields up to 10 T
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    V. Khovaylo, I. Tereshina, G. Politova, A. Karpenkov, S. Taskaev, T. Palewski

    Magnetostriction of a non-modulated martensite was measured for Ni2.27Mn0.73Ga ferromagnetic shape memory alloy in steady magnetic fields μ0H up to 10 T at temperatures below room temperature and in μ0H ≤ 1 T at temperatures above room temperature. Linearity of the longitudinal magnetostriction λ|| observed at high fields μ0H > 6 T implies that the magnetostriction is associated with a 3d electron band. The anisotropic magnetostriction obtained in a magnetic field μ0H = 1 T at T = 4.2 K is ∼16 ppm and decreases down to 3 ppm with the increase in temperature. The volume magnetostriction is positive but very small (∼0.6 ppm) under these conditions. In the region of the magnetostructural phase transition the longitudinal and volume magnetostriction showed a complex sigh-changing behavior which depends on the strength of applied magnetic field. Thermal expansion coefficient α of Ni2.27Mn0.73Ga in the martensitic state was measured to be α ∼13 × 10−6 K−1 which is comparable with the thermal expansion coefficient of a non-stoichiometric Ni2.19Mn0.81Ga single crystal.

    更新日期:2018-01-17
  • Ordered corn-like CuCo2O4 nanoforests covering Ni foam for a high-performance all-solid-state supercapacitor
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Yuqiao Wang, Dawei Yang, Jianing Lian, Tao Wei, Yueming Sun

    The ordered corn-like CuCo2O4 nanoforests were directly deposited on Ni foam by a hydrothermal/annealing method as a binder-free electrode for a symmetric supercapacitor. The ordered one-dimensional nanostructure can enhance an effective electron transport. The abundant sub-structure can be used to contribute to increasing a large number of active sites for Faradaic reactions. The binder-free loading can help to reduce the ohmic polarization during the charge/discharge process. For three-electrode configuration, the specific capacitance achieved 820 F/g at a current density of 2 mA/cm2 and long-term capacity retention of ∼94% after 1500 cycle. The symmetric device gained a high energy density of 17 W h/kg at a power density of 480 W/kg.

    更新日期:2018-01-17
  • Dynamic response of surface micro-features subjected to a laser shock wave planishing technique
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Fengze Dai, Jie Geng, Xudong Ren, Jinzhong Lu, Shu Huang

    A periodic micro-groove was fabricated on the surface of LY2 aluminum samples using a picosecond laser system, and then the samples were subjected to a laser shock wave planishing (LSWP) treatment. The deformation of micro-features was evaluated using a non-contact 3D profilometer. The experimental results show that LSWP can effectively lower the height of the micro-features. An axisymmetric 2D model was constructed to simulate the dynamic response of the micro-features at a strain rate of 106 s−1. The profile of micro-features predicted from the finite element modeling matches quite well with the experimental results. The simulated dynamic deformation of micro-features clearly reveals the plastic flow behaviors of the surface materials after the LSWP treatment and provides useful optimized LSWP parameters to control the roughness and profile accuracy of the treated surface.

    更新日期:2018-01-17
  • Degradation of precipitation hardening in 7075 alloy subject to thermal exposure: A Cs-corrected STEM study
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Jingxu Kent Zheng, Xuesong Xu, Ruichun Luo, Xiaoqin Zeng, Bin Chen
    更新日期:2018-01-17
  • Magnetic phase inhomogeneity in frustrated intermetallic compound Sm2Ni0.87Si2.87
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Santanu Pakhira, Chandan Mazumdar, R. Ranganathan, S. Giri

    A new ternary compound Sm2Ni0.87Si2.87, belonging to intermetallic R2TX3 family (R = rare-earth, T = transition metals, X = Si, Ge, etc.), could be synthesized in single phase only by the deliberate introduction of lattice vacancies in the Ni and Si sites. The detailed studies of heat capacity as well as dc and ac magnetization including different non-equilibrium dynamical behaviour, viz., aging effect, temperature and field dependent magnetic relaxation and magnetic memory effect establish the compound to be a cluster-glass material having a spin freezing temperature ∼6.6 K. To understand the nature of the glassy phase, experimental results have been analysed using a few different theoretical models and found that the observed magnetic memory effect favours the hierarchical model over the droplet model. Competing exchange interaction driven magnetic phase inhomogeneity could be further confirmed through exchange bias effect. The observed magnetic phase inhomogeneity has been attributed to random magnetic anisotropy that develops due to local environmental variations between the rare-earth ions.

    更新日期:2018-01-17
  • Enhanced thermoelectric and mechanical properties of Na-doped polycrystalline SnSe thermoelectric materials via CNTs dispersion
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Fei Chu, Qihao Zhang, Zhenxing Zhou, Diankun Hou, Lianjun Wang, Wan Jiang

    SnSe-based thermoelectric materials have captured much attention since single-crystal SnSe exhibited record high ZT. However, the practical application is limited due to the poor mechanical properties and harsh production conditions of single crystals. Herein, we achieve high thermoelectric performances and enhanced mechanical properties in the Na-doped polycrystalline SnSe through implanting carbon nanotubes (CNTs). The CNTs are truncated and uniformly dispersed within the Na-doped SnSe matrix via a combination of cryogenic grinding and spark plasma sintering technique. It is found that Na-doped polycrystalline SnSe/CNTs composites maintain high carrier concentrations of approximately 4 × 1019 cm−3 at room temperature, resulting in great power factors. The dispersion of CNTs reduces the thermal conductivity without significant deterioration on the electrical conductivity. A maximum ZT of ∼0.96 at 773 K is achieved via adding merely 0.25 vol% CNTs. More fundamentally, the Na-doped polycrystalline SnSe samples incorporated with CNTs show superior mechanical properties, which are favorable for device fabrication and practical applications.

    更新日期:2018-01-17
  • Mechanical and tribological properties of NiAl/muscovite composites
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Yukun Han, Kang Yang, Peixing Jing, Bing Xue, Weidong Ma
    更新日期:2018-01-17
  • Facile-synthesized carbonaceous photonic crystals/magnetic particle nanohybrids with heterostructure as an excellent microwave absorber
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Congpu Mu, Jiefang Song, Bochong Wang, Fusheng Wen, Can Zhang, Cong Wang, Zhongyuan Liu, Jianyong Xiang
    更新日期:2018-01-17
  • Magnetic phase transition and large room temperature magnetoresistance in Ni doped FeRh films
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Jia-hui Chen, Jing Ma, Yu-jun Zhang, Liang Wu, C.W. Nan

    We have investigated the structural, magnetic and electrical transport properties of the Ni doped FeRh films prepared by magnetron co-sputtering. A large magetoresistance of 35%, induced by a reversible antiferromagnetic to ferromagnetic phase transition, is obtained at room temperature with only 1 mol.% Ni addition. Magnetic field is revealed to have an equivalent effect as temperature to drive the magnetic phase transition. Moreover, the way to realize a nonvolatile room temperature magetoresistance effect is also discussed. These results give FeRh the possibility of technological application in the spintronic field at room temperature, which are referential to other material systems with a first-order magnetic phase transition.

    更新日期:2018-01-17
  • Physicochemical characterizations of Cu2Sn0.7Si0.3S3 made from sputtered precursors for thin film solar cell applications
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Romain Bodeux, Maïmouna W. Diouf

    Cu2(Sn,Si)S3 is a potential material for obtaining cost effective and non-toxic absorber in thin films solar cell devices. Furthermore tunable bandgap can be achieved in the whole optimal range 1.1 eV–1.5 eV depending on the Si/(Sn + Si) ratio. We report on the synthesis of thin Cu2(Sn,Si)S3 films by a cosputtering-annealing route starting from Cu-Sn-Si precursors. The films consisted of densely packed grains. Combination of X-ray diffraction and Raman spectroscopy confirmed the formation of a Cu2Sn0.7Si0.3S3 solid solution with a monoclinic structure. The presence of Cu2SnS3 was also evidenced near the substrate and could be due to the formation kinetic of Cu2SnS3 and Cu2(Sn,Si)S3. Optical and electrical measurements showed that the substitution of 30% Sn by Si leads to a band gap increasing from 0.9 eV to 1.2 eV while maintaining the p-type conductivity. Based on these results, It can be concluded that the Cu2(Sn,Si)S3 compound is a promising absorber to be used in thin film solar cell applications.

    更新日期:2018-01-17
  • Enhanced reactivity of Ni-Al reactive material formed by cold spraying combined with cold-pack rolling
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Huilin Zhao, Chengwen Tan, Xiaodong Yu, Xianjin Ning, Zhihua Nie, Hongnian Cai, Fuchi Wang, Yan Cui

    Near-fully-dense (porosity<1%) Ni-Al reactive bulk materials were obtained by cold spraying and large deformation without crack was successfully achieved by the subsequent gradual cold-pack rolling, and the largest total thickness reduction could reach 95%. The influences of cold-pack rolling on the reactivity of the cold-sprayed Ni-Al reactive materials were investigated. The material reactivity was addressed through the solid-state reaction threshold temperature in thermal explosion mode conducted by differential scanning calorimetry and combustion wave velocity in self-propagating mode measured by a high-speed camera. For the cold-sprayed materials with rolling treatment, the onset of solid diffusion reaction shifted to a lower temperature range by 30–40 °C in the DSC experiment. An obvious increase in the combustion reaction reactivity of the cold-sprayed samples after treatment with cold-pack rolling was demonstrated. The combustion wave velocities for the materials with fifteen gradual rolling passes could reach 130–140 mm/s. The combustion reaction velocity showed a linear dependence on the statistic results of contact area per unit volume (Sv) between Ni and Al reactants and an expression was proposed, giving an activation energy of 129 kJ/mol.

    更新日期:2018-01-17
  • Microstructure evolution and deformation behaviors of AZ31 Mg alloy with different grain orientation during uniaxial compression
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-17
    Minjian Hou, Hua Zhang, Jianfeng Fan, Qiang Zhang, Lifei Wang, Hongbiao Dong, Bingshe Xu

    Effect of grain orientation on deformation behaviors and microstructure evolution of rolled AZ31 Mg alloy during uniaxial compression have been investigated as a function of temperature and strain rate. Rectangular prism samples of rolled AZ31 Mg alloy were compressed along different directions, with the compression axis parallel to the sheet normal direction (ND), the 45° direction and the rolling direction (RD), referred to as ND, 45° and RD sample, respectively. The results indicated that the compression flow curve, the strength and the strain hardening rate were highly anisotropic with respect to the initial grain orientation at various temperature and strain rate, especially at low temperature and low strain rate. This is due to the fact that the crystallographic slips dominate the early deformation in ND sample, the crystallographic slips and {10–12} twinning collectively dominate the early deformation in 45° sample while the {10–12} twinning dominates the early deformation in RD sample at low temperature. The anisotropies gradually decreased with the increasing temperature, which is due to that the dislocation slips gradually begin to dominate the deformation. Obvious dynamic recrystallization (DRX) had taken place with the increasing temperature. CDRX and DDRX were initiated in the ND sample during compressing at elevated temperature. In addition to CDRX and DDRX, {10–12} twin related DRX was also initiated in the RD sample during compressing at elevated temperature.

    更新日期:2018-01-17
  • Intermediate-temperature solid oxide fuel cells with high performance cobalt-doped Pr0.5Ba0.5FeO3-δ anodes
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-16
    Youkun Tao, Yue Zhou, Wenyuan Li, Jing Shao, Lei Bai, Xingbo Liu

    Cobalt doped Pr0.5Ba0.5FeO3-δ perovskite exhibits superior electrochemical performance when it was tested as an anode for intermediate temperature solid oxide fuel cell. For the anode with a composition of Pr0.5Ba0.5Co0.25Fe0.75O3-δ–Ce0.9Gd0.1O2-δ, the polarization resistance Rp was as low as 0.05 Ωcm2 at 700 °C in air and 0.21 Ωcm2 at 700 °C in 3% H2O–97% H2. In addition, this full-ceramic anode was tolerant to 50 ppm H2S and showed stable performance during the preliminary test. The ceramic composite also exhibited superior activity for cathodic oxygen-reduction-reaction (ORR), thus enabled a symmetrical fuel cell. In a lab designed full-ceramic symmetrical fuel cell, a power density of 0.75 Wcm−2 at 750 °C has been achieved, demonstrating the superior properties of this oxide.

    更新日期:2018-01-17
  • Evaluations of cooling rate and initial temperature on thermal shock behavior of ZrB2-SiC ceramic
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-16
    Anzhe Wang, Ping Hu, Cheng Fang, Dongyang Zhang, Xinghong Zhang

    The effects of cooling rate and initial temperature on thermal shock behavior of ZrB2-SiC ceramic were studied by water spraying method with a thermocouple real-time temperature acquisition technique for the first time. It was shown that the cooling rate could be adjusted by changing the water flow rate, and the fracture behavior strongly depended on both the cooling rate and initial temperature. When the extreme value of cooling rate was constant, the decrease of initial temperature would lead to the increase of thermal stress, accompanied by a more serious damage of material, which was mainly because of the nonlinear relationship between thermal expansion coefficient and temperature.

    更新日期:2018-01-17
  • Large electrocaloric effect in lead-free Ba(ZrxTi1-x)O3 thick film ceramics
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-13
    Xiao-Dong Jian, Biao Lu, Dan-Dan Li, Ying-Bang Yao, Tao Tao, Bo Liang, Sheng-Guo Lu

    Barium zirconate titanate (Ba(ZrxTi1-x)O3) thick film ceramics were prepared using a tape-casting method. Their structures, morphologies, and electric properties were characterized using XRD, SEM and impedance analysis approaches, respectively. The electrocaloric effects (ECE), i.e., isothermal entropy changes and adiabatic temperature changes, were calculated using a Maxwell relation. It was confirmed by XRD and SEM that the obtained thick film ceramics are pure and dense perovskite structures. The dielectric analyses indicate that the Ba(ZrxTi1-x)O3 thick film ceramics show characteristics of transition from normal to relaxor ferroelectrics with the increasing Zr4+ ionic content. The polarization – electric field (P-E) hysteresis loops reveal larger polarizations and the ceramics can withstand an electric field as high as 12 MV/m. The adiabatic temperature changes ΔT calculated via the Maxwell relation and the polarization as a function of temperature, which is extracted from the P-E hysteresis loops measured at 12 MV m−1 are from 3.7 to 0.28 K with the increasing Zr4+ ionic content.

    更新日期:2018-01-13
  • 更新日期:2018-01-13
  • Magnetic properties of DyFe5−xCoxAl7: Suppression of exchange interactions and magnetocrystalline anisotropy by Co substitution
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-13
    D.I. Gorbunov, A.V. Andreev, D.S. Neznakhin, M.S. Henriques, J. Šebek, Y. Skourski, S. Daniš, J. Wosnitza

    In 3d−4f 3 d − 4 f intermetallic compounds, a Co substitution for Fe usually strengthens the exchange interactions due to a shift of the Fermi energy to a region of the 3d 3 d band with higher density of states. Here, we study the influence of Co on the magnetism of ferrimagnetic DyFe5Al7 using magnetization measurements in static (up to 14 T) and pulsed (up to 58 T) magnetic fields. We find that the homogeneity range of DyFe5−xCoxAl7 is limited to x≤2.5 x ≤ 2.5 . The Co substitution for Fe produces a strong detrimental effect on the 3d−3d 3 d − 3 d intrasublattice exchange interactions, which leads to a pronounced decrease of the Curie temperature and of the 3d−4f 3 d − 4 f intersublattice exchange field. A reduction of the density of states at the Fermi level might occur due to a broadening of the 3d 3 d band. A decrease of the rare-earth contribution to the magnetic anisotropy energy is also observed with increasing Co content. This is attributed to a competition between the Fe and Co contributions to the crystal electric field at the Dy site.

    更新日期:2018-01-13
  • The structural and electronic properties of Pt-Cu alloy clusters: Embedding atom method combined with density functional theory study
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-13
    Xueling Lei, Haimen Mu, Shuai Li, Gang Liu, Bo Xu, Chuying Ouyang

    Using an embedding atom method, the low-lying candidate structures of a large Pt-Cu alloy cluster Pt86Cu22 were obtained through screening 105 isomers. The results indicate that the Pt@PtCu core-shell structures with Pt skin and PtCu core are energetically more stable than the others, which is in good agreement with the experimental observation. Furthermore, an impurity Cu atom is preferred to stay at the subsurface instead of the surface region of Pt-Cu alloy clusters, and the doped Cu atoms prefer to disperse in Pt-Cu alloy. The electronic structures of the EAM optimized structures are calculated with density functional theory, and the projected electronic densities of states reveal that Cu doping can obviously enrich the electronic states of surface Pt atoms near the Fermi level, which may provide some clues for understanding the mechanism of enhancement of the catalytic activity for Pt-Cu alloy catalyst.

    更新日期:2018-01-13
  • Characterization of a functionally graded material of Ti-6Al-4V to 304L stainless steel with an intermediate V section
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Lourdes D. Bobbio, Brandon Bocklund, Richard Otis, John Paul Borgonia, R. Peter Dillon, Andrew A. Shapiro, Bryan McEnerney, Zi-Kui Liu, Allison M. Beese
    更新日期:2018-01-12
  • Thermodynamic analysis and experimental study on the phase equilibria in Fe-Mn-Cr-O system
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Yuwen Ding, Ya Liu, Yangtian Yan, Xuping Su

    Oxidation diagram of the Fe-Mn-Cr-O system was determined using Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectrometer and X-ray power diffraction. The 1000 °C isothermal section of the Fe-Mn-Cr-O system was investigated experimentally. The oxide phases, Spinel, Monoxide and Corundum can equilibrate with the Fe-Mn-Cr alloys. Two three-phase equilibrium regions (two oxide phases coexist with alloy phase), Corundum + Spinel + Bcc and Monoxide + Spinel + Fcc, have been detected. The oxide phase boundary of Spinel and Monoxide was obtained. Thermodynamic computations of the Fe-Mn-Cr-O oxidation diagram at 1000 °C and 800 °C were performed. In comparison with the calculated phase diagram, the experimental oxide phase boundary of Spinel and Monoxide turns towards the Fe-Cr side partially. The phase diagram can be used to predict the oxidation of high-strength steel.

    更新日期:2018-01-12
  • Microstructure, mechanical properties and corrosion behavior of an Fe-10Cr-2.7B-5.5Al-13Mn alloy prepared by spark plasma sintering
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Jian Liu, Weiping Chen

    An Fe-10Cr-2.7B-5.5Al-13Mn alloy has been fabricated by the combination of mechanical alloying (MA) and spark plasma sintering (SPS). Microstructure and phase evolution of the alloy powder and sintered specimen were investigated by using scanning electron microscopy (SEM), X-ray diffractometer (XRD) and transmission electron microscopy (TEM). The resultant mechanical properties were determined in Rockwell hardness and compressive strength. The corrosion behavior was tested by immersing test in 750 °C molten pure aluminum for 1 h and 4 h. Results have shown that the sintered specimen is mainly composed of Fe2AlCr intermetallic, CrFeB-type boride and Mn2B-type boride uniformly distributed in theγmatrix. The sintered specimen achieves Rockwell Hardness and compressive strength of 59.7 ± 0.2 HRC and 2823 ± 21.0 MPa at room temperature, respectively. Especially, compressive strength of the sintered specimen at 600 °C reaches 902 ± 15.5 MPa. The high hardness and compressive strength can be attributed to solid solution of Al, Cr and Mn, precipitation of CrFeB, Mn2B and Fe2AlCr in the γ-Fe matrix and nanocrystalline microstructure produced by the combine of MA and SPS. The corrosion rate of the sintered Fe-10Cr-2.7B-5.5Al-13Mn in molten aluminum is ~ 36% of that of H13. CrFeB, Mn2B and Fe2AlCr play a key role in improving the corrosion resistance of the sintered specimen in molten aluminum. They are embedded in the corrosion products (intermetallics) and act as roots to capture the intermetallics from falling off.

    更新日期:2018-01-12
  • Optical anisotropy modulation in nonpolar a-plane AlGaN by manipulating the anisotropic in-plane strains through SiNx interlayers engineering
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Yi Zhang, Jun Zhang, Hanling Long, Jingwen Chen, Shuai Wang, Ju He, Jiangnan Dai, Changqing Chen

    The achievement of high polarization nonpolar III-nitrides has been hindered by high density of defects, large surface fluctuations and in-plane strains. Here, we show that these critical challenges can be improved by manipulating the growth time of SiNx interlayers. The discolation density of nonpolar a-plane Al0.1Ga0.9N has been effectively reduced by introducing the in-situ deposited SiNx interlayer, as the nonpolar a-plane Al0.1Ga0.9N can only nucleate at open pores of SiNx nanomask. During the growth process, the lateral overgrowth will occur from the openings with the dislocation bending and annihilation. Furthermore, the strip distributed nanomask can change the anisotropy of in-plane strains and optical properties of nonpolar a-plane Al0.1Ga0.9N. When the growth time of SiNx increased from 0 min to 2 min, the in-plane strain along m-axis and c-axis direction changed from −0.2250% and −0.5145% to −0.0638% and −0.2728%, respectively. More importantly, the optical degree of polarization of nonpolar a-plane Al0.1Ga0.9N has been changed from 0.4385 to 0.8129 along with the increase SiNx deposition time by polarized photoluminescence. By simplely changing the SiNx growth time, high polarization nonpolar a-plane devices may be fabricated on this high quality strain-modulatable nonpolar AlGaN template, which is desirable for high efficiency liquid crystal displays or other polarization sensitive photodetectors.

    更新日期:2018-01-12
  • Phase-separation phenomenon of NiGePt alloy on n-Ge by microwave annealing
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Chung-Chun Hsu, Kun-Lin Lin, Wei-Chun Chi, Chen-Han Chou, Guang-Li Luo, Yao-Jen Lee, Chao-Hsin Chien

    During the formation of distinct bilayer NiGePt alloy, a phase-separation phenomenon was observed using microwave annealing and structural engineering. The microstructures of bilayer NiGePt [PtGe(Ni)–NiGe(Pt)] alloys fabricated with 10-nm Ni and various thicknesses of Pt (5, 10, and 15 nm) were characterized. Within the same thermal budget as microwave annealing, the diffusion of Ni exhibited stronger alloy formation ability with Ge and drilled through the Pt layer without resistance. The higher diffusivity of Ni atoms dominated the diffusion of Ni through the Pt layer to form a stable crystalline layer, NiGe(Pt). Ge diffused outwardly toward the Pt layer to form a PtGe(Ni) layer. This special phenomenon of bilayer alloy formation was elucidated using nanobeam electron diffraction by transmission electron microscopy in conjunction with energy-dispersive spectrometry. Comparing the differences in metal alloys between microwave and rapid thermal annealing, microwave annealing formed a bilayer alloy more apparently than rapid thermal annealing. The results and electrical characteristics indicated that a thicker Pt layer for forming a bilayer NiGePt alloy with alloy separation could also effectively improve the leakage current of NiGePt [PtGe(Ni)– NiGe(Pt)]/n-Ge Schottky junctions.

    更新日期:2018-01-12
  • Electrosprayed graphene decorated with ZnO nanoparticles for supercapacitors
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Edmund Samuel, Priyanka U. Londhe, Bhavana Joshi, Min-Woo Kim, Karam Kim, Mark T. Swihart, Nandu B. Chaure, Sam S. Yoon

    A binder-free nanocomposite consisting of ZnO nanoparticles (NPs) grown directly on graphene sheets by electrospraying was fabricated for use as an electrode material in supercapacitors. The optimal concentrations of graphene and ZnO NPs were determined from the capacitive characteristics of the composite. Scanning electron microscopy confirmed that the ZnO NPs grew in a uniformly distributed manner on the graphene sheets and that they exhibited negligible agglomeration. Further, X-ray diffraction analysis confirmed that ZnO growth was preferentially oriented along (100) plane in ZnO/graphene composite. (R2-1)A symmetric supercapacitor fabricated using this composite exhibited an energy density of 67 mWh·cm−3 and power density of 6000 mW·cm−3. The composite also showed good long-term cycling performance, retaining 90% of its capacitance after 1000 galvanostatic charge/discharge cycles.

    更新日期:2018-01-12
  • Photoluminescence efficiency significantly enhanced by surface modification of SiO2 coating on β-sialon:Eu2+ phosphor particle
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Chenning Zhang, Tetsuo Uchikoshi, Rong-Jun Xie, Lihong Liu, Yoshio Sakka, Naoto Hirosaki

    The surface modification on the β-sialon:Eu2+ phosphor particles was successfully achieved by the SiO2 coating via a sol-gel method. The photoluminescence (PL) intensity of the phosphor was effectively enhanced and dominantly depending on the homogeneity of the SiO2 coating. It was found that more homogeneous and smooth SiO2 coating was responsible for higher PL intensity. The strongest emission intensity was obtained after the SiO2 homogenously coating under an optimized preparation condition of tetraethoxysilane (TEOS):H2O = 1:1 in molar ratio by improving ∼39% of intensity compared to that of the uncoated β-sialon:Eu2+ phosphor, due to effective elimination on the surface groups of the phosphor particles. However, with increasing the molar ratio of TEOS:H2O, the PL intensity of the coated phosphor became deteriorated owing to the poor homogeneity in the coating layer, even became lower than that of the uncoated sample when TEOS:H2O = 1:40 in molar ratio. This technique would be potentially applied in various phosphors assembling for the white light-emitting diodes by significantly improving their photoluminescence efficiencies.

    更新日期:2018-01-12
  • Lüders-like martensitic transformation in a Cu/carbon-steel nanocomposite: An in situ synchrotron study
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Yadong Ru, Kaiyuan Yu, Shuangqiang Dai, Fangmin Guo, Shijie Hao, Yang Ren, Lishan Cui

    A Cu/carbon-steel nanocomposite is fabricated by pressing, rolling and wire drawing. The average layer thickness is about 69 nm for steel and 67 nm for Cu. Cu suppresses the growth of prior austenite at elevated temperature, and thus the steel layer thickness barely increases during austenization. Subsequent quenching results in a large amount of metastable retained austenite within the steel layers. The martensitic transformation behavior of the composite during plastic deformation is investigated by in situ tensile test using synchrotron X-ray diffraction at room temperature. It is found that the retained austenite, rather than Cu, dominates the plastic deformation of the nanocomposite. In situ results verify that the transformation of retained austenite initiates in a manner of Lüders-like band due to stress-induced martensitic transformation, followed by strain-induced martensitic transformation until fracture.

    更新日期:2018-01-12
  • 更新日期:2018-01-12
  • 更新日期:2018-01-12
  • Thermal fatigue damage and residual mechanical properties of W-Cu/Ag-Cu/1Cr18Ni9 brazed joint
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Chunzhi Xia, Weiwei Sun, Yi Zhou, Xiangping Xu

    Thermal fatigue properties of W-Cu/1Cr18Ni9 steel brazed joint with Ag-Cu filler metal has been studied in this paper. With the increment of fatigue cycles, fatigue damage of the brazed joint became increasingly serious. There were micro holes and cracks appeared on the interface between brazing seam and base metals, and bending strength decreased from 690 MPa of the original joint to 380 MPa after 200 fatigue cycles. Fracture characteristic of W-Cu/Ag-Cu/1Cr18Ni9 joint changed from ductile fracture of the original joint to mixed ductile-brittle fracture after 200 fatigue cycles under external bending load and internal fatigue damage. The ductile fracture located on the Ag-based solid solution of brazing seam, and the brittle fracture occurred on the W-Cu composite.

    更新日期:2018-01-12
  • The first principles study of the sulfur oxidation on Ni surface with H2O
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Yanxing Zhang, Xiaopei Xu, Zongxian Yang
    更新日期:2018-01-12
  • Activated nitrogen-doped porous carbon ensemble on montmorillonite for high-performance supercapacitors
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Wenwen Zhang, Zhenbo Ren, Zongrong Ying, Xindong Liu, Hui Wan

    An activated nitrogen-doped porous carbon ensemble on montmorillonite (MMT) was prepared through hydrothermal carbonization of glucose on MMT followed by carbonization with melamine and activation with KOH at high temperatures. The carbonaceous species was effectively guided to be heterogeneously deposited onto the surface of MMT and inserted into the interlayer spacing. The resulting N-doped carbon composite has a unique microstructure, large specific surface area (657 m2 g−1), high nitrogen content (5.5 at%), maximum specific capacitance of 223 F g−1 at a current density of 1 A g−1 and an outstanding rate capability (205 F g−1 retained at 3 A g−1) in a 6 M KOH aqueous electrolyte. Moreover, approximately 90% of the initial capacitance was retained after 8000 cycles at a current density of 1 A g−1, suggesting an excellent cycling stability.

    更新日期:2018-01-12
  • Synthesis and electrochemical performances of Zn3V3O8 as novel anode material for lithium ion battery application
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Junjie He, Xiaolin Liu, Xiao Chen, Hao Zheng, Chuanqi Feng

    Zn3V3O8 microspheres are successfully synthesized by a facile solvothermal method. Then a serious of time-dependent experiments is explored to study the effects of different reaction time on the growth process for Zn3V3O8 microspheres. The structure and morphology of the as-prepared samples are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM) and transmission electron microscopy (TEM) techniques. The results indicate that pure phase of Zn3V3O8 with good crystallinities synthesized. It takes morphology of microspheres with the diameter of 2–3 μm. The electrochemical performances of different samples as anode material for lithium ion battery are also investigated. The Zn3V3O8 sample synthesized for 18 h exhibits high capacity, excellent rate capability and stable cycle performance. The initial discharge capacity of the Zn3V3O8 is1358 mAh g−1at 100 mA g−1 and retained it at 1019 mAh g−1 after 100 cycles in the voltage range of 0.01–3.0 V. The superior electrochemical performances of Zn3V3O8 make it possible to be used as promising anode for future application.

    更新日期:2018-01-12
  • Enhancement of multiferroic properties in Bi0.92Ho0.08Fe0.97Mn0.03O3/Zn0.5Ni0.5Fe2O4 bilayered thin films by tunable schottky barrier and interface barrier
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Meiyou Guo, Guoqiang Tan, Wei Yang, Long Lv, Zhongwei Yue, Zhengjun Chai, Yun Liu, Huijun Ren, Ao Xia, Ruilian Tan
    更新日期:2018-01-12
  • The effects of neodymium addition on the intermetallic microstructure and mechanical properties of Al-7Si-0.3Mg-0.3Fe alloys
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Qi Tang, Jianhua Zhao, Tao Wang, Jing Chen, Ke He

    The effects of neodymium (Nd) addition (0, 0.03, 0.06 and 0.09 wt.%) on the intermetallic microstructure and mechanical properties of Al-7Si-0.3Mg-0.3Fe (wt.%) alloys were investigated in this study. The microstructures of the intermetallic compounds in the alloys were observed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The Nd-rich particles gradually coarsened with increase of Nd addition and attached to the β-AlFeSi phase surface. Besides, the larger Nd-rich particles in the alloys decreased in size and became spherical after T6 heat treatment. In addition, the Nd addition could influence the amount of the π-AlSiMgFe phase by affecting the undercooling of the quaternary eutectic reaction (Liq. → Al + Si + Mg2Si + Al8FeMg3Si6). The amount of the π-AlSiMgFe phase increased when a little (0.03 wt.%) Nd was added, however with the further increasing Nd content, the larger Nd-rich particles often tightly attached on the β-AlFeSi phase surface and reduced the amount of the π-AlSiMgFe phase. Furthermore, the 0.03Nd as-cast alloy had the optimal conditions for the formation of the π-AlSiMgFe and the spherical Nd-rich particles with the ultimate tensile strength about 302 MPa and elongation about 3.1% after T6 heat treatment.

    更新日期:2018-01-12
  • An investigation on diffusion bonding of TZM alloy and Nb-Zr alloy using Ni foil as an interlayer
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    J.M. Lin, Z.W. Yang, H.H. Wei, Y. Wang, Z.Q. Ma, D.P. Wang

    Diffusion bonding of TZM alloy and Nb-Zr alloy without and with Ni interlayer was carried out at the temperature ranging from 1000 °C to 1100 °C for 30min under a pressure of 10 MPa. The effects of bonding temperature and the thickness of Ni interlayer on the microstructure and mechanical properties of the diffusion bonded joints were investigated systematically. Compared with the direct diffusion bonding method, sound TZM/Nb-Zr joints were obtained with Ni interlayer at a low bonding temperature of 1000 °C. When the bonding temperature was 1100 °C, sound joints could be achieved for both methods. But the joint shear strength with 30 μm Ni interlayer reached 228 MPa, which was 60% higher than that bonded without Ni interlayer. The diffusion-induced reaction layers were determined to be NiMo, Ni3Mo + Ni4Mo, Ni8Nb, Ni3Nb and Ni6Nb7, whose thickness and micro-hardness were measured at different bonding conditions to establish a correlation between the interfacial microstructure and joint properties. It was found that the thickness of Ni3Nb layer and the remained Ni foil were beneficial to the joint shear strength. By changing Ni foil from 0 to 45 μm, the shear strength was improved obviously, and then kept at around 250 MPa with further increasing Ni foil to 120 μm. The maximum shear strength was 264 MPa when the joint was bonded at 1100 °C for 30min with 45 μm Ni foil. Cracks were initiated from NiMo and Ni6Nb7 diffusion layers, and then propagated across the central diffusion layers.

    更新日期:2018-01-12
  • Structural analysis of Ce0.83Dy0.14Ca0.03O1.90 (CDC) and enhanced electrical conductivity of its composites with alkali carbonates for LT-SOFCs
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Khagesh Tanwar, Nandini Jaiswal, Pulkit Sharma, Devendra Kumar, Om Parkash

    Present work mainly deals with two important aspects of co-doped ceria based solid electrolytes. First, the occurrence of micro-strain or structural distortions in ceria lattice on doping of Dy3+ and Ca2+ at the place of Ce4+. Second, an enhancement in electrical conductivity by formation of nano-composites of Ce0.83Dy0.14Ca0.03O1.90 (CDC) and eutectic mixture of sodium and lithium carbonates [(Li0.52Na0.48)2CO3] (LNCO). CDC ceramic powder was synthesized by citrate-nitrate auto-combustion route. Nano-composites were prepared by mixing the CDC powder with LNCO using a ball mill. X-ray diffraction studies were carried out to analyze the crystal structure of CDC and to study the amorphous nature of carbonates in the nanocomposites. Thermal behavior of the nanocomposites was studied by differential scanning calorimetry (DSC). XRD data of CDC were refined by Rietveld analysis to determine the lattice parameters, atomic positions, bond lengths, bond angles, oxygen deficiency and possible micro-strain. Microstructures of the specimens were studied using scanning electron microscope. Electrical conductivity of the nanocomposites was investigated by using complex plane impedance analysis. A significant improvement in electrical conductivity was observed in nanocomposites with varying concentration of carbonates. Maximum conductivity, 1.05× × 10−1 S cm−1 at 500 °C, was observed in the composite with 30 wt% (CDC/30LNCO) of carbonates content.

    更新日期:2018-01-12
  • Electrochemical activation of novel Fe-based Li-rich cathode material for lithium-ion batteries
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Taolin Zhao, Yuxia Zhang, Yanting Li, Xiuguo Sun, Yikai Li, Rixin Ji
    更新日期:2018-01-12
  • Sol-gel synthesis of MnxNi1-xCo2O4 spinel phase materials: Structural, electronic, and magnetic properties
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Tarekegn Heliso Dolla, Karin Pruessner, David G. Billing, Charles Sheppard, Aletta Prinsloo, Emanuela Carleschi, Bryan Doyle, Patrick Ndungu

    A series of spinel-type MnxNi1-xCo2O4 (x = 0, 0.3, 0.5, 0.7, 1) oxides were synthesized by using a citrate sol-gel technique. The structural, magnetic and electronic properties of the oxides with different Mn content were investigated using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), vibrating sample magnetometer (VSM) and X-ray photoelectron spectroscopy (XPS). The XRD and FTIR studies revealed that MnxNi1-xCo2O4 formed in a cubic structure for all the compositions synthesized. Transmission electron microscopy (TEM) studies show cubic nano-plates for x = 0 and on increasing Mn concentration, agglomerated nanoparticles with sphere-like shape are observed with a particle size in the range of 11.7 nm–22.1 nm. This is in close agreement with the results of XRD analysis. The Mn 2p, Ni 2p, and Co 2p XPS spectra reveal the coexistence of Mn2+, Mn3+, Ni2+, Ni3+, Co2+, and Co3+ species on the surface of MnxNi1-xCo2O4 samples in differing proportions. The measurements of magnetic properties at room temperature show that the samples have some ferromagnetic behaviour. The saturation magnetization, remnant magnetization, and coercivity of the nanoparticles vary significantly with a concentration of Mn, which tends to be distributed in both tetrahedral and octahedral positions of the spinel lattice.

    更新日期:2018-01-12
  • Effect of Cu redistribution in grain boundary on magnetic properties of Sm(Co0.665Fe0.25Cu0.06Zr0.025)7 permanent magnets
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-12
    Y.Q. Wang, M. Yue, D. Wu, D.T. Zhang, W.Q. Liu, H.G. Zhang, Y.H. Du
    更新日期:2018-01-12
  • ZnO hierarchical microsphere for enhanced photocatalytic activity
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Sheng Wang, Panyong Kuang, Bei Cheng, Jiaguo Yu, Chuanjia Jiang
    更新日期:2018-01-12
  • Sulfur codoping enables efficient oxygen electroreduction on FeCo alloy encapsulated in N-Doped carbon nanotubes
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Dengke Zhao, Ligui Li, Lihong Xie, Ni Zhou, Shaowei Chen
    更新日期:2018-01-12
  • Microstructural evolution and phase transformation kinetics of MnBi alloys
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Zhen Xiang, Taolei Wang, Shangjun Ma, Liwei Qian, Zhengyi Luo, Yiming Song, Huawei Yang, Wei Lu

    The low temperature phase (LTP) compound of MnBi is a promising, rare-earth metal free, and permanent magnetic material. However, it is difficult to obtain pure LTP MnBi, which results from a peritectic reaction between Mn and Bi atoms. In this study, the microstructural evolution and phase transformation kinetics of MnxBi100-x (x = 50, 55, 60) alloys were systematically investigated. Choosing an appropriate Mn content (Mn55Bi45) was found to promote the formation of the LTP MnBi. The results of the phase transformation kinetics indicated that the nucleation, growth and soft impingement processes are involved in the phase transformation process. In addition, in the initial stage of the LTP phase transformation, it was shown that the diffusional transformation was governed by two- and three-dimensional nucleation and growth, as well as a single mechanism of diffusion-controlled growth, which describes the entire transformation. At the final stage of the phase transformation, diffusion controlled growth, with soft impingement effects, dominates the process. The phase transformation kinetics analysis was confirmed with the X-ray diffraction and scanning electron microscopy results. This work implies that the local activation energy, Ec(α), and local Avrami exponent, n(α), can be applied to characterize the phase transformation behaviors of the LTP MnBi alloy.

    更新日期:2018-01-12
  • Effects of calcium doping on yttrium titanate for microwave absorbing applications
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Qinlong Wen, Wancheng Zhou, Yiding Wang, Fa Luo, Dongmei Zhu, Zhibin Huang, Yuchang Qing

    We reported on the dielectric and microwave absorbing properties of Ca-doped Y2Ti2O7 prepared by hot-pressing sintering. The structure, thermogravimetric analysis, conductivity, dielectric and microwave absorbing properties were systematically investigated. The results indicated that the main charge compensation mechanism was oxygen vacancies at low Ca2+ doping concentration, while at high Ca2+ doping levels, oxygen vacancies and Ca interstitials coexisted in the Y2-xCaxTi2O7. The major types of polarization process involved in this study are electronic, atomic and space charge polarization and orientational polarization. The minimum reflection loss of Y1.8Ca0.2Ti2O7 can reach −40.9 dB with a thickness of 1.1 mm. These properties manifest that Ca-doped Y2Ti2O7 ceramics have the potential applications as microwave absorbing materials.

    更新日期:2018-01-12
  • Effect of solution heat treatment on microstructure and electrochemical behavior of electron beam smelted Inconel 718 superalloy
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Xiaogang You, Yi Tan, Longhai Zhao, Qifan You, Yinong Wang, Fei Ye, Jiayan Li

    Effect of solution heat treatment on microstructure and electrochemical behavior was investigated for the electron beam smelted (EBS) 718 superalloy. The results imply that the solution heat treatment has a great influence on the precipitation behavior of EBS 718 superalloys and thus affects the electrochemical behavior. The increase of solution temperature gives rise to the solution of δ phase for both solution treated and aged EBS 718 superalloys. The 980 °C solution treated and aged EBS 718 superalloy exhibits the maximum content of the volume fraction of γʹʹ phase, in parallel with the highest lattice misfits. Further increase of solution temperature results in the precipitation of dispersively distributed γʹ particles. The pitting potential for the solution treated superalloys increases gradually with increase of solution temperature, and a similar behavior is observed for the aged superalloys with an exception of the alloy processed at 980 °C. The effect of solution temperature on the solution treated superalloys can be elucidated by considering the variation of the volume fraction and the size of δ precipitates. For the aged superalloys, the deterioration effect of Nb rich γʹʹ is obvious due to the tetragonal distortion and accompanying strain field in the nearby matrix. Higher solution temperature results in a uniform distribution of the nano-scale γʹ phase and smallest lattice misfits, with the highest apparent activation energy derived to be 52.86 kJ/mol.

    更新日期:2018-01-12
  • Improved upconversion efficiency and thermal stability of NaYF4@SiO2 photonic crystal film
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Cheng Zhu, Wenying Zhou, Jiaojiao Fang, Yaru Ni, Liang Fang, Chunhua Lu, Zhongzi Xu, Zhitao Kang

    Fluorescent photonic crystal films (PCFs), which consisted of monodisperse NaYF4:10Yb, 0.5Tm@SiO2 or NaYF4:10Yb, 0.5Er, 0.2Tm@SiO2 core-shell spheres (10%, 0.5% and 0.2% represent the reactant mole percentage), were successfully fabricated. The morphologies and structures of PCFs were measured, while the fluorescent properties of NaYF4 in PCFs with different photonic band gap (PBG) positions were investigated. Besides, the energy transfer process in thermal coupled energy levels of NaYF4:10Yb, 0.5Tm@SiO2 under different temperatures was discussed. The results indicated that the short wave emission of NaYF4 can be enhanced by the regulation of photon mode density (PMD) in photonic crystals. Particularly, when the infrared 800 nm emission peak was in the range of PBG position of the PCF sample, the energy transfer process of 3H4-3H6 was suppressed and the short wave emission was enhanced by 1.64 times. Due to the well thermal radiation ability of silica shell, the thermal coupled energy levels (3F3 and 3H4) of NaYF4:10Yb, 0.5Tm@SiO2 core-shell spheres exhibited more stable emission intensities than NaYF4:10Yb, 0.5Tm nanoparticles, when the experimental temperatures varied from 30 to 300 °C.

    更新日期:2018-01-12
  • Structural investigation of Ca/Zr co-substituted BaTiO3 through XRD and Raman spectroscopy
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Vijayeta Pal, O.P. Thakur, R.K. Dwivedi

    The present work reports the synthesis of Lead free (Ba1-xCax)(ZryTi1-y)O3 with x = 0.13, y ≤ 0.15 (i.e. BCTZ) piezoceramics by semi-wet route and effect of additives viz., Ca2+, and Zr4+ on phase formation, microstructure, piezoelectric and electromechanical properties. Detailed structural analysis suggests the formation of tetragonal perovskite phase with P4mm symmetry, which was also confirmed by Rietveld refinement and Raman spectra. SEM micrographs showed that the average grain size decreased with Zr4+ which acts as grain growth inhibitor. Composition with x = 0.13 and y = 0.10 exhibited the optimum piezoelectric and electromechanical properties (d33 = 367 ± 2 pC/N and kp = .39 ± 0.01) and showed higher densification (relative density ∼ 98%).

    更新日期:2018-01-12
  • 更新日期:2018-01-12
  • Effect of morphology on the electrophoretic deposition of hydroxyapatite nanoparticles
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Morteza Farrokhi-Rad

    Electrophoretic deposition (EPD) was performed from alcoholic suspensions of spherical (SHA) and fiber (FHA) hydroxyapatite nanoparticles. FHA particles were horizontally aligned in deposits prepared at lower voltages since they can find enough space and time to rotate upon reaching the deposit and sit horizontally on it. While, they are more randomly oriented at higher voltages since more FHA particles aligned parallel to electric field reach to the substrate and also particles cannot find enough time and space for rotation. FHA particles are highly interlocked together in FHA deposits reinforcing them and also the drying shrinkages are lower for them resulting in their less cracking. The cracks are parallel to each other in FHA coating deposited from methanolic suspension at 5 V due to the more horizontal and parallel alignment of FHA particles in it. The crack-free SHA coating decreased the corrosion rate of substrate more efficiently due to its less porosity.

    更新日期:2018-01-12
  • Al2O3 coated Li1.2Ni0.2Mn0.2Ru0.4O2 as cathode material for Li-ion batteries
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Na Su, Yingchun Lyu, Run Gu, Bingkun Guo
    更新日期:2018-01-12
  • 更新日期:2018-01-12
  • Microstructure and properties of C/C–ZrC composites prepared by hydrothermal deposition combined with carbothermal reduction
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Cuiyan Li, Guibiao Li, Haibo Ouyang, Jianfeng Huang, Xianghui Hou

    Carbon fiber reinforced carbon matrix containing ZrC (C/C–ZrC) composites were prepared by hydrothermal deposition combined with carbothermal reduction. The submicron ZrC particles (100–300 nm) were dispersed in the matrix. The stress-strain curves of the composites presented a typical pseudo-plastic fracture behavior. The mass and linear ablation rates of the composites were 3.7 × 10−3 g/s and 4.2 × 10−3 mm/s, respectively. The formation of ZrO2 glass layer reduced erosion of the composites in the ablation center. The continuous C–ZrC–ZrO2 skeleton layer generated from the oxidation of ZrC can protect the composites from erosion at the ablation brim region. The obtained C/C–ZrC composites present a promising potential as ablation resistance materials.

    更新日期:2018-01-12
  • The effective fingerprint detection application using Gd2Ti2O7:Eu3+ nanophosphors
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Sung Jun Park, Ji Yoon Kim, Jin Hyeok Yim, Na Yun Kim, Chan Hyeok Lee, Seung Joon Yang, Hyun Kyoung Yang
    更新日期:2018-01-11
  • 更新日期:2018-01-11
  • Dislocation density based model for Al-Cu-Mg alloy during quenching with considering the quench-induced precipitates
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Ruichao Guo, Jianjun Wu

    The accurate prediction of residual stress for as-quenched Al-Cu-Mg alloy requires profound knowledge on the materials' constitutive behavior. In present work, the flow stress of as-quenched Al-Cu-Mg alloy is modeled using a dislocation density based model which considers the influences of precipitation, solid solution and forest dislocation. The radii and volume fractions of precipitates at different cooling rates and temperatures are predicted by a multi-class precipitation kinetics model. Parameters of the constitutive model are obtained by calibration using isothermal tensile tests. The model predictions are in good agreement with experimental data in terms of the flow stress and volume fraction evolution. The results show that volume fraction of precipitates decreases with the increasing temperature and cooling rate, in contrast to the increasing trend for radius of precipitates. The quench-induced precipitates have an influence only on the magnitudes of flow stress at low temperatures. However, for the large precipitates, the dislocation loops, i.e. geometrically necessary dislocations (GND's), can influence both the strain hardening rates and magnitudes of flow stress.

    更新日期:2018-01-11
  • Study on the reaction mechanism and intermetallic compound formation in tri-metal Ti/Al/Nb composite
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Robabeh Jafari, Beitallah Eghbali

    Tri-dissimilar Ti/Al/Nb multilayer composites were produced from Ti, Al and Nb sheets by solid state diffusion bonding through hot pressing and subsequent hot rolling. By annealing the produced composites at temperatures higher than the melting point of Al, the microstructures consisted of dispersed intermetallic particles in an Al matrix were obtained. The microstructural characterizations were performed by scanning electron microscope, X-ray diffraction and transmission electron microscope. Also, the interactions between Ti, Al and Nb were studied by observation of the microstructural evolutions during annealing at different temperatures (700–760 °C) and durations (30–120 min). Results showed that there are three distinct regions in the diffusion reaction zone (DRZ). In the first region, irregular shaped and angular particles were observed, which are distributed in a wide region of Al matrix. Prolonged annealing times caused formation of a dense intermetallic compound (Ti, Nb)Al3 layer. The second region has consisted of only Al matrix and in the third region, TiAl3 spherules were formed and expelled into the liquid by new TiAl3 spherules and, the composition of these particles is changed to (Ti,Nb)Al3 after prolonged annealing times.

    更新日期:2018-01-11
  • Synthesis of tremella-like graphene@SiC nano-structure for electromagnetic wave absorbing material application
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Xinkun Wang, Liuyan Yin, Chen Chen, Jinshan Yu, Xingui Zhou, Honglei Wang, Binshi Xu, Shicheng Wei

    A kind of particle with “tremella-like” surface and core-shell structure was synthesized by pyrolysizing polycarbosilane (PCS). The “tremella-like” surface was mainly composed of graphene, which perpendicularly grew on the nucleus. The nucleus was composed of polycrystalline SiC, in which β-SiC nano-crystal randomly dispersed in amorphous matrix. This kind of particle was believed to have a great potential in the electromagnetic wave absorbing material application, because it had a huge specific surface area, core-shell structure, electromagnetic wave absorbing SiC core. The formation mechanism of this kind of particle was also discussed. It was thought that this kind of particle was derived from the small PCS molecules released during the pyrolysis of PCS precursor. Moreover, the carbon atoms participating in the growth of graphene was believed to separate out from the SiC nucleus at higher temperature.

    更新日期:2018-01-11
  • Crystal structure and magnetic properties of Ti-doped Bi0.84La0.16FeO3 at morphotropic phase boundary
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    P.T. Tho, E.M. Clements, D.H. Kim, N. Tran, M.S. Osofsky, M.H. Phan, T.L. Phan, B.W. Lee

    We have studied the crystal structure and magnetic properties of Bi0.84La0.16Fe1-xTixO3 (x = 0.02–0.1) at the morphotropic phase boundary of R3c, Imma, and Pbam phases. The results of Rietveld-refined X-ray diffraction patterns reveal the existence of multi-phase structures, including R3c + Imma for x = 0.02–0.06 and Imma + Pbam for x = 0.08–0.1. The studies of Raman scattering spectra indicate a structural transformation through the disappearance of typical R3c modes. This strongly influences the magnetic properties that are dependent on the crystalline phase ratio. In particular, the magnetic coercivity of x = 0.04–0.06 drastically changes when the Imma phase is dominant. A mechanism of magnetic interactions occurring at the phase boundary is proposed to explain the features of magnetic hysteresis loops of the compounds.

    更新日期:2018-01-11
  • Nanocrystalline Ti/AZ61 magnesium matrix composite: Evolution of microstructure and mechanical property during annealing treatment
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Huan Yu, Yu Sun, Zhipeng Wan, Haiping Zhou, Lianxi Hu

    Nanocrystalline Ti/AZ61 magnesium matrix composite, prepared by mechanical milling, was annealed in the temperature range of 573–723 K for various durations. During annealing treatment, diffusion of Al and Ti elements, formation of precipitates and grain growth behavior were observed and the evolution of hardness was obtained. Based on microstructural evolution, the mechanism for the precipitating of Ti and Al from magnesium matrix was analyzed. And the corresponding schematic illustration of microstructural evolution model was proposed. By the observation from high-resolution transmission electron microscopy, it was found that dispersing nanometer sized particulates, precipitated from Ti and Al supersaturated Mg solid solution, pined up magnesium grain boundaries. During annealing treatment, the nano-scaled precipitates together with original submicron Ti particulates hindered the movement of grain boundaries. Thus, the thermal stability for magnesium grains was improved. After annealing treatment at 723 K for 600 min, this magnesium matrix composite with the average grain size of ∼93 nm was still nanocrystalline. In addition, influence of temperature and time on hardness was investigated. After annealing treatment at 723 K for 600 min, the hardness of annealed Ti/AZ61 composite is approximately 116 HV, presenting outstanding thermal stability.

    更新日期:2018-01-11
  • Pattern selection of twinned growth in aluminum alloys during Bridgman solidification
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    Luyan Yang, Shuangming Li, Junbo Guo, Kai Fan, Yang Li, Hong Zhong, Hengzhi Fu

    By using the electron backscattered diffraction (EBSD) technique, pattern selection of twinned growth in Al-4.5 wt.% Cu alloy has been studied in Bridgman solidification experiments. Based on the original twin planes formed at 3000 μm/s, the twinned growth was produced till the end of solidification after abruptly decreasing the growth rate to 100, 50, 20, 10, 5, 3, 1 and 0.3 μm/s. The stable twinned growth could be achieved during a wide range of solidification process. For the first time, the so-called twinned cell pattern was observed and prevailed in the solidified structure at 3 and less than 3 μm/s. The twinned growth in aluminum alloy was not limited to dendrite pattern as has previously been reported. The twinned pattern selection map was also revealed. Meanwhile, an interesting orientation rotation phenomenon was elucidated using EBSD technique on both sides of the coherent twin boundary during twinned cell growth. At a lower rate of 0.3 μm/s, the orientation rotation deflection concerning the original Σ3 60° twinning relation was confirmed. Some coincidence site lattice boundaries with higher Σ values served as the preferred states for this orientation deflection during growth.

    更新日期:2018-01-11
  • High-pressure strengths of Ni3Al and Ni-Al-Cr
    J. Alloys Compd. (IF 3.133) Pub Date : 2018-01-11
    S.V. Raju, B.K. Godwal, A.K. Singh, R. Jeanloz, S.K. Saxena

    High-pressure x-ray diffraction on Ni3Al, non-hydrostatically compressed at room temperature to 30 GPa in radial geometry can be interpreted in terms of a hydrostatic pressure–volume equation of state. We found the yield strength of Ni3Al to increase from about 0.2 to 2 GPa as pressure increases from 0 to 30 GPa. Yield-strength values determined from x-ray diffraction in axial geometry by including a Poisson ratio effect and pressure gradient methods are in good accord with each other. Our results indicate that the strengths of both pure and Cr-doped (7 at. %) Ni3Al increase with pressure, with the yield strength of Ni3Al slightly higher than Ni-Al-Cr alloy.

    更新日期:2018-01-11
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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