Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
Impact factor:6.155

The journal has been awarded the excellent periodical in China, and its articles are covered by SCI, EI, CA, SA, JST, RJ, CSA, MA, EMA, AIA etc., PASCAL web. ISI web of Science,SCOPUS.

  Current Issue
      01 October 2020, Volume 54 Issue 0 Previous Issue   
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    Research Article
    Mechanistic study of ammonium-induced corrosion of AZ31 magnesium alloy in sulfate solution
    Hui Pan, Liwei Wang, Yi Lin, Feng Ge, Kang Zhao, Xin Wang, Zhongyu Cui
    J. Mater. Sci. Technol., 2020, 54 (0): 1-13.  DOI: 10.1016/j.jmst.2020.02.074
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    The influence of NH4+ ions on the corrosion behavior of AZ31 magnesium alloy was investigated by immersion test, hydrogen evolution, electrochemical methods and morphology observation. The results demonstrate the acceleration effect of NH4+ on corrosion of AZ31 magnesium alloy due to the disruption of protective MgO film in NH4+-containing solution. The loose and cracked corrosion products of AZ31 magnesium alloy in NH4+-containing solutions are mainly composed of (Mg0.833Al0.167)(OH)2(CO3)0.083·0.75H2O and Mg5(CO3)4(OH)2·5H2O. When the NH4+ concentration is lower than 0.01 M, knife-cut like corrosion occurs in some active area of the surface due to the partial dissolution of MgO layer. As the NH4+ concentration is increased to 0.1 M, the MgO layer is completely disrupted, resulting in the occurrence of uniform corrosion. Both cathodic and anodic reactions are accelerated by NH4+ ions, while the effect of original pH values on the reaction kinetics can be neglected in NH4+-containing solutions.

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    Microstructure evolution and deformation mechanism of amorphous/crystalline high-entropy-alloy composites
    Jia Li, Haotian Chen, Hui Feng, Qihong Fang, Yong Liu, Feng Liu, Hong Wu, Peter K Liaw
    J. Mater. Sci. Technol., 2020, 54 (0): 14-19.  DOI: 10.1016/j.jmst.2020.02.070
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    High-entropy amorphous alloys present high hardness, but low tensile ductility. Here, deformation behavior of the amorphous/crystalline FeCoCrNi high-entropy alloy (HEA) composite prepared by the previous experiment is investigated using atomic simulations. The result shows the partial dislocations in the crystal HEA layer, and the formation of shear bands in the amorphous HEA layer occurs after yielding. The strength of the amorphous/crystalline HEA composite reduces with increasing the thickness of the amorphous layer, agreeing with the previous experiments. The coupled interaction between the crystal plasticity and amorphous plasticity in amorphous/crystalline HEA composites results in a more homogeneous redistribution of plastic deformation to cause interface hardening, due to the complex stress field in the amorphous layer. The current findings provide the insight into the deformation behavior of the amorphous/crystalline HEA composite at the nanoscale, which are useful for optimizing the structure of the HEA composite with high strength and good plasticity.

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    Highly efficient single-crystalline NaNb1-XTaXO3 (X = 0.125) wires: The synergistic effect of tantalum-doping and morphology on photocatalytic hydrogen evolution
    Qianqian Liu, Quan Zhang, Lu Zhang, Wei-Lin Dai
    J. Mater. Sci. Technol., 2020, 54 (0): 20-30.  DOI: 10.1016/j.jmst.2020.05.006
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    For the first time in this work, we manage to synthesize single-crystalline NaNb0.875Ta0.125O3 wires by combining the advantages of one-dimensional (1D) nanostructure and heteroatom doping strategy. Careful Ta doping was performed to figure out the correlation between morphological and structural evolution as well as the photocatalytic performance towards H2 generation. It was found that, the as-prepared NaNb0.875Ta0.125O3 wires presented a highest and stable photocatalytic performance, which was appropriately 41 and 2 folds higher than that of bare NaTaO3 and NaNbO3. The optical activity was mainly ascribed to the synergistic effect between appropriate Ta doping and perfect 1D wire-like morphology, which resulted in fewer defects, improved charge transfer efficiency and higher reduction capability of electrons. On the other hand, a possible photocatalytic mechanism of photocatalytic H2 production was proposed in detail. This work creates a new perspective into designing multi-component materials and understanding the mechanism of H2 evolution, which offers new opportunities for solar-energy conversion.

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    Microstructural softening induced adiabatic shear banding in Ti-23Nb-0.7Ta-2Zr-O gum metal
    Silu Liu, Y.Z. Guo, Z.L. Pan, X.Z. Liao, E.J. Lavernia, Y.T. Zhu, Q.M. Wei, Yonghao Zhao
    J. Mater. Sci. Technol., 2020, 54 (0): 31-39.  DOI: 10.1016/j.jmst.2020.03.042
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    Ti-23Nb-0.7Ta-2Zr-O gum metal (GM) is an attractive candidate material for applications that require superior mechanical properties. In our earlier investigation of the GM [1], geometrical softening and the generation of adiabatic shear bands (ASBs) were proposed as primary reasons for the documented anisotropic impact response. In the present study, electron backscattered diffraction (EBSD) analysis reveals two different deformed microstructures, i.e., deformed ultrafine grains (UFGs) and dynamically recrystallized UFGs, formed in the ASBs of GM samples processed by extrusion equal channel angular pressing (ECAP), respectively. Additional calculation of temperature rise during dynamic compression suggests that the above microstructure differences in the ASBs was originated from their different maximum ASB temperatures (608?K for extruded GM and 1159?K for ECAP-processed GM). Moreover, our calculation on the temperature at the onset of ASBs indicates that microstructural softening is the primary cause for the development of ASBs in both extruded GM (321?K) and ECAP-processed GM (331?K).

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    Intergrowth mechanism and morphology prediction of faceted Al3Ni formed during solidification by a spatial geometric model
    Zongye Ding, Qiaodan Hu, Wenquan Lu, Fan Yang, Yihan Zhou, Naifang Zhang, Sheng Cao, Liao Yu, Jianguo Li
    J. Mater. Sci. Technol., 2020, 54 (0): 40-47.  DOI: 10.1016/j.jmst.2020.02.078
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    The interplay and intergrowth characteristic of faceted intermetallic compounds (IMCs) during solidification was originally investigated through the rod-like Al3Ni crystals in the liquid Al/solid Ni interconnection by using synchrotron radiography, and the diversified 3-D morphologies were reconstructed by synchrotron tomography. A spatial geometric model was established to effectively predict the diversified growth patterns of two spatial crystals. For the two overlapping Al3Ni crystals, the impeded crystal growth was divided into three different stages, decided by the hindrance form the other crystal. Further, the groove formed on the crystal surface is directly related to the solute redistribution under the critical condition of boundary layer thickness larger than two crystals distance. The closer distance and smaller crystal size indicate the deeper and larger groove, and the morphology changes from hemispheroid to hemi-ellipsoid with the increased opposite and interacted faces.

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    Research article
    Free-standing ZnO nanorod arrays modified with single-walled carbon nanotubes for betavoltaics and photovoltaics
    Changsong Chen, Jiang Chen, Zhen Wang, Jian Zhang, Haisheng San, Shichao Liu, Chunyu Wu, Werner Hofmann
    J. Mater. Sci. Technol., 2020, 54 (0): 48-57.  DOI: 10.1016/j.jmst.2020.03.040
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    A full-duplex radiant energy converter based on both betavoltaic and photovoltaic effects in an easy-to-implement way is an attractive alternative for the autonomous wireless sensor microsystem. Here, we report a novel beta/photovoltaic cell based on free-standing ZnO nanorod arrays (ZNRAs) modified with metallic single-walled carbon nanotubes (m-SWCNTs), using radioisotope63Ni as beta-emitting source. The ZNRAs were grown on Al-doped ZnO (AZO) conductive glass using hydrothermal method. The optimum length and diameter of ZnO nanorods were determined by Monte Carlo simulation for beta energy deposition in ZNRAs. The m-SWCNTs were anchored into the ZNRAs to form a three-dimensional (3-D) Schottky junction structure for effectively separating the beta/photo-excited electron-hole pairs. Experimentally, the betavoltaic and photovoltaic effects were confirmed through the I-V measurements of beta/photovoltaic cells under beta/UV/Vis irradiations, respectively. It is suggested that the m-SWCNTs play key role for the enhancement of beta/photovoltaic performance through the formation of extensive 3-D Schottky junction, the conductive network for hole transport, and the surface plasmon resonance exciton absorption for visible light.

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    Research Article
    Microscopic stresses in carbon nanotube reinforced aluminum matrix composites determined by in-situ neutron diffraction
    X.X. Zhang, J.F. Zhang, Z.Y. Liu, W.M. Gan, M. Hofmann, H. Andrä, B.L. Xiao, Z.Y. Ma
    J. Mater. Sci. Technol., 2020, 54 (0): 58-68.  DOI: 10.1016/j.jmst.2020.04.016
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    One of the most desired strengthening mechanisms in the carbon nanotube reinforced aluminum matrix composites (CNT/Al) composites is the load transfer strengthening mechanism (LTSM). However, a fundamental issue concerning the LTSM is that quantitative measurements of load partitioning in these composites during loading are very limited. In this study, in-situ neutron diffraction study on the tensile deformation of the 3 vol.% CNT/2009Al composite and the unreinforced 2009Al alloy was conducted. The {311} and {220} diffraction elastic constants (DECs) of the 2009Al alloy were determined. Using those DECs the average stress in the 2009Al matrix of the composite was calculated. Then the average stress in the CNTs was separated by using the stress equilibrium condition. Computational homogenization models were also applied to explain the stress evolution in each phase. Predicted results agree with experimental data. In the present case, the average stress in the CNTs reaches 1630 MPa at the yield strength of the composite based on linear regression of the measured data, which leads to an increment of yield strength by about 37 MPa. As the result of this work, an approach to quantify load partitioning in the CNTs is developed for the CNT/Al composites, which can be applied to optimize the mechanical properties of the composites.

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    Facile synthesis of hierarchical Ni3Se2 nanodendrite arrays for supercapacitors
    Licheng Zhao, Ping Zhang, Yanan Zhang, Zhi Zhang, Lei Yang, Zhi-Gang Chen
    J. Mater. Sci. Technol., 2020, 54 (0): 69-76.  DOI: 10.1016/j.jmst.2020.02.063
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    Rational design has been widely used to develop high-performance metal selenides-based electrode materials for supercapacitors. In this study, we develop a facile one-step solvothermal approach to synthesize binder-free Ni3Se2 nanodendrite arrays grown on nickel foam as advanced positive electrodes for supercapacitors. Our Ni3Se2 nanodendrite arrays on nickel foam exhibit a specific capacitance of 1234 F g-1 (3.70 F cm-2) at a current density of 1 A g-1 and a great rate capability, which is benefited from the excellent electrical conductivity and unique hierarchical nano-dendritic structure. Furthermore, an asymmetric supercapacitor device was assembled using activated carbon as the negative electrode and the Ni3Se2 nanodendrite arrays on nickel foam as the positive electrode, obtaining a high energy density of 22.3 W h kg-1 at a power density of 160.4 W kg-1.

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    Atomic-scale tuned interface of nickel-rich cathode for enhanced electrochemical performance in lithium-ion batteries
    Yongqiang Liu, Xin Wang, Jiyu Cai, Xiaoxiao Han, Dongsheng Geng, Jianlin Li, Xiangbo Meng
    J. Mater. Sci. Technol., 2020, 54 (0): 77-86.  DOI: 10.1016/j.jmst.2020.02.080
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    The Ni-rich layered LiNi0.6Mn0.2Co0.2O2 (NMC622) is one promising cathode for lithium-ion batteries (LIBs), but suffers from poor cycling stability under high cutoff potentials. The performance degradation was reflected as capacity fading and voltage drop, having their roots in instable interface of NMC622. Aimed at improving interfacial stability, in this study, we deposited nanoscale ZrO2 coatings conformally over NMC622 cathodes using atomic layer deposition (ALD). We found that, under a high cutoff voltage (4.5 V), the ALD ZrO2 coatings evidently improved the performance of NMC622 cathode, showing better cyclability and higher sustainable capacity. In addition, the ALD coatings dramatically boosted the rate capability of NMC622. All these compelling performance results are ascribed to the atomic-scale tunable ZrO2 coatings via ALD, which create stable interface and thereby inhibit unfavorable evolutions. In the study, we utilize a suite of characterization tools and various analyses to clarify the effects of ALD ZrO2 coatings. This study will be helpful for improving the performance of nickel-rich cathodes via interfacial engineering using ALD.

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    A unified model for determining fracture strain of metal films on flexible substrates
    Xu-Ping Wu, Xue-Mei Luo, Hong-Lei Chen, Ji-Peng Zou, Guang-Ping Zhang
    J. Mater. Sci. Technol., 2020, 54 (0): 87-94.  DOI: 10.1016/j.jmst.2020.03.043
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    Failure strain determination of polymer-supported thin films is a key for the design of the flexible devices. A theoretical model R/R0=(L/L0) 2 (R, L are the electrical resistance and the length of the stretched film, respectively. R0, L0 are the corresponding initial values.) has been widely used to determine the fracture strain of thin films on flexible substrates. However, this equation loses its function in some special cases. Here, a simple and universal theoretical model was proposed to determine the fracture strain of metal thin films on flexible substrates in more generally situations. With this model, we investigated the thickness-dependent failure strains of Cu-5 at.% Al films with thickness of 10 nm, 200 nm, 1000 nm, and Ti films with thickness of 50 nm, 100 nm, 300 nm. This model was also employed to study the published data available. The results showed that the new model provided a fairly good prediction of the failure strains of different films.

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    On the localised corrosion of carbon steel induced by the in-situ local damage of porous corrosion products
    Lin Pang, Zhengbin Wang, Yugui Zheng, Xueming Lai, Xu Han
    J. Mater. Sci. Technol., 2020, 54 (0): 95-104.  DOI: 10.1016/j.jmst.2020.03.041
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    The effect of in-situ local damage of uniform porous corrosion products on the localised corrosion of carbon steel is investigated using the wire beam electrode technique (WBE) combined with morphology characterisation and electrochemical tests. The WBE measurements demonstrate that the localised corrosion is enhanced by the in-situ local removal of porous corrosion products, supported by the morphology characterisation and electrochemical tests. The enhanced localised corrosion does not originate from the damaged wire in WBE where the corrosion products are removed but from the other undamaged wires, which is reported for the first time. A mechanism is proposed that the intensive anodic polarisation effect of the damaged wire on the undamaged wires could account for the enhanced localised corrosion, which is due to the protective corrosion products newly formed on the damaged surface and the increase in the potential of damaged wire.

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    The importance of H2 in the controlled growth of semiconducting single-wall carbon nanotubes
    Feng Zhang, Jia Sun, Yonggang Zheng, Peng-Xiang Hou, Chang Liu, Min Cheng, Xin Li, Hui-Ming Cheng, Zhen Chen
    J. Mater. Sci. Technol., 2020, 54 (0): 105-111.  DOI: 10.1016/j.jmst.2020.02.067
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    H2 is considered an indispensable component of the atmosphere for the growth of high-quality single-wall carbon nanotubes (SWCNTs) by chemical vapor deposition. However, details of the roles H2 playing are still unclear due to the complex conditions of SWCNT growth. In this study, we elucidate the functions of H2 in the selective growth of semiconducting SWCNTs (s-SWCNTs) by using monodispersed uniform Fe nanoparticles as a catalyst. High-quality s-SWCNTs were synthesized by finely tuning the concentration of H2 and the other growth parameters. Experimental data combined with atomistic simulations indicate that H2 not only adjusts the concentration of the carbon source, but also serves as a mild etchant that selectively removes small carbon caps grown by a perpendicular mode from the Fe nanoparticles. These results provide useful hints for the controlled growth of SWCNTs with a semiconducting or metallic conductivity, and even a specific chirality.

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    A new sight into the glass forming ability caused by doping on Ba- and Ti-site in BaTi2O5 glass
    Hao Liu, Xuan Ge, Qiaodan Hu, Fan Yang, Jianguo Li
    J. Mater. Sci. Technol., 2020, 54 (0): 112-118.  DOI: 10.1016/j.jmst.2020.02.076
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    La- and Nb-doped BaTi2O5 (BT2) spherical glasses were prepared by a containerless aerodynamic levitation method and their glass-forming regions were established. It is found that La-doping on the Ba-site (network-modifier) and Nb-doping on the Ti-site (network-former) show distinct difference in the glass-forming region: less than 10 % La can replace Ba whereas 40 % Nb can incorporate into BT2 glass. The distinction in glass-forming ability induced by La- and Nb-doping is discussed mainly from the structural arrangement of the glass. Raman spectroscopy analysis shows that La-doping elongates the short Ti-O bonds in the distorted [TiO5] polyhedra and thus relaxes the network. Nb-doping introduces [NbO6] polyhedra into BT2 and there exists a critical doping level (20 %), below which incorporation of Nb into BT2 relaxes the [TiOn] polyhedra by shortening the long Ti-O bond and above which [NbO6] starts to participate in the network skeleton construction resulting in a dramatic change in the glass structure, which is supported by the dramatic change in the exothermic peak on the DTA curves. This work triggers the speculation that the network-modifiers in BT2 glass possess a very important role in the structure of network-former skeleton than those in glasses based on traditional network-former oxides such as SiO2, GeO2 and B2O3, which may provide a useful strategy for modifying the properties of these novel glasses by chemical doping.

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    The effect of crack tip environment on crack growth behaviour of a low alloy steel at cathodic potentials in artificial seawater
    Yong Li, Zhiyong Liu, Endian Fan, Zhongyu Cui, Jinbin Zhao
    J. Mater. Sci. Technol., 2020, 54 (0): 119-131.  DOI: 10.1016/j.jmst.2020.04.034
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    The environment at crack tip and its effect on the crack growth behaviour of low alloy steel- E690 steel were studied at cathodic potentials in artificial seawater. The results showed that the micro environment at crack tip and crack growth behaviour were related to the electrochemical reactions at crack tip, which were affected by the stress state and applied potentials. The crack tip environment was acidified under cyclic loading, resulting from the crack tip anodic dissolution reaction and corresponding hydrolysis reaction. Because of the hydrogen evolution and the inhibited anodic dissolution inside the crack, the crack tip pH increases as the cathodic potential decreases. The effect of cathodic potentials on the electrochemical reactions caused the variation of the hydrogen content, which influenced the crack growth rate because the crack growth behaviour was controlled by hydrogen embrittlement mechanism. This resulted in a fact that with the negative decrease of potential, the crack growth rate first decreased and then increased, with the minimum rate at -0.75 V. And the crack growth path exhibited transgranular fracture.

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    Improving cyclic oxidation resistance of Ni3Al-based single crystal superalloy with low-diffusion platinum-modified aluminide coating
    H. Liu, M.M. Xu, S. Li, Z.B. Bao, S.L. Zhu, F.H. Wang
    J. Mater. Sci. Technol., 2020, 54 (0): 132-143.  DOI: 10.1016/j.jmst.2020.05.007
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    A low-diffusion NiRePtAl coating ((Ni,Pt)Al outer layer in addition to a Re-rich diffusion barrier layer) was prepared on a Ni3Al-base single crystal (SC) superalloy via electroplating and gaseous aluminizing treatments, wherein the electroplating procedures consisted of the composite deposition of Ni-Re followed by electroplating of Pt. In order to perform a comparison with conventional NiAl and (Ni,Pt)Al coatings, the cyclic oxidation performance of the NiRePtAl coating was evaluated at 1100 and 1150 °C. We observed that the oxidation resistance of the NiRePtAl coating was significantly improved by the greater presence of the residual β-NiAl phase in the outer layer and the lesser outward-diffusion of Mo from the substrate. In addition, the coating with the Re-rich diffusion barrier demonstrated a lower extent of interdiffusion into the substrate, where the thickness of the second reaction zone (SRZ) in the substrate alloy decreased by 25 %. The mechanisms responsible for improving the oxidation resistance and decreasing the extent of SRZ formation are discussed, in which a particular attention is paid to the inhibition of the outward diffusion of Mo by the Re-based diffusion barrier.

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    Amino-functionalized Ti3C2Tx with anti-corrosive/wear function for waterborne epoxy coating
    Han Yan, Meng Cai, Wen Li, Xiaoqiang Fan, Minhao Zhu
    J. Mater. Sci. Technol., 2020, 54 (0): 144-159.  DOI: 10.1016/j.jmst.2020.05.002
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    Two-dimensional Ti3C2Tx flakes have great application potential in various areas due to their optical, electronic, electrochemical and mechanical properties, but their anti-corrosion and wear-resistance performance were not well understood. The difficulties in achieving good dispersity and interface interaction of inorganic additives in organic coatings hinder the incorporation of Ti3C2Tx into the epoxy coating. Here, few-layered Ti3C2Tx sheets with amino-functionalization were prepared, and as reinforced-additives were added into the waterborne epoxy coating. Anti-corrosion and tribological properties of as-prepared composite coatings were investigated in detail. The results reveal that the composite coating with 0.5 wt.% amino-functionalized Ti3C2Tx sheets shows excellent corrosion protection (the lowest frequency impedance was 3.12 × 109 Ω cm 2) and wear resistance (wear rate was reduced by 72.74%). The greatly improving performance of composite coatings mainly depends on: (a) good dispersity and compatibility of amino-functionalized Ti3C2Tx in organic matrix, (b) high adhesion strength between coating and metal substrate and (c) the intrinsic properties of Ti3C2Tx sheets. The work provides a good path for applications of MXene as multifunctional additives.

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    Achieving ultra-high strength in Mg-Gd-Ag-Zr wrought alloy via bimodal-grained structure and enhanced precipitation
    Yu Zhang, Wei Rong, Yujuan Wu, Liming Peng
    J. Mater. Sci. Technol., 2020, 54 (0): 160-170.  DOI: 10.1016/j.jmst.2020.04.031
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    Mg-13.1Gd-1.6Ag-0.4 Zr (wt%) alloy was either iso-thermally extruded at 350 °C or differential-thermally extruded with respectively pre-heated billet at 500 °C and die at 350 °C. The iso-thermal extrusion leads to a near fully recrystallized structure and a [0001]//ED (extrusion direction) texture. In contrast, the differential-thermally extruded alloy develops a bimodal-grained structure composed of fine equiaxed recrystallized grains and coarse elongated unrecrystallized grains with a 011ˉ0//ED texture. The differential-thermally extruded alloy has a higher number density of precipitates after post-extrusion ageing than that of the iso-thermally extruded counterpart. Moreover, precipitation in the differential-thermally extruded alloy is further enhanced with cold rolling before ageing. Finally, the alloy obtains room temperature tensile yield strength of 421 MPa and ultimate tensile strength of 515 MPa via differential-thermal extrusion, cold rolling and ageing, mainly ascribed to the coupled strengthening from the bimodal-grained structure and enhanced precipitation. Strength of the alloy is noticeably higher than those of Mg-Gd(-Y)-Ag extruded alloys with similar compositions reported previously and is comparable to those of other high-strength Mg wrought alloys. The findings suggest that differential-thermal extrusion plus strain ageing is a suitable approach for achieving high strength in age-hardenable Mg alloys.

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    Effect of Ni content in Cu1-xNix coating on microstructure evolution and mechanical properties of W/Mo joint via low-temperature diffusion bonding
    Mei Rao, Guoqiang Luo, Jian Zhang, Yiyu Wang, Qiang Shen, Lianmeng Zhang
    J. Mater. Sci. Technol., 2020, 54 (0): 171-180.  DOI: 10.1016/j.jmst.2020.02.005
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    The 93W and Mo1 refractory metals were bonded with different Cu1-xNix coating interlayers of various Ni content using plasma-activated sintering at 700?°C. The effects of the Ni content in the Cu1-xNix coating interlayer on the interfacial microstructure evolution and mechanical properties of the W/Mo joints were studied. The maximum average shear strength of the W/Mo joint was 316.5?MPa when the Ni content of the Cu1-xNix coating interlayer was 25 %. When the Ni content of the Cu1-xNix coating interlayer was below 50 %, the atomic diffusion at the W/Mo joint interface was adequate without the formation of intermetallic compounds, as demonstrated by the High Resolution Transmission Electron Microscope analyses of the joints. The presence of Ni in Cu1-xNix promoted diffusion bonding at the interface, which contributed to the high mechanical properties of the W/Mo joint. With an increase in the Ni content of the Cu1-xNix coating interlayer, the MoNi intermetallic compound (IMC) nucleated and grew at the Cu1-xNix coating/Mo1 interface. When the Ni content of the Cu1-xNix coating interlayer was above 50 %, the generation of a brittle MoNi IMC weakened the shear strength of the W/Mo joint dramatically.

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    Vanadium-doped TiO2-B/anatase mesoporous nanotubes with improved rate and cycle performance for rechargeable lithium and sodium batteries
    D.P. Opra, S.V. Gnedenkov, A.A. Sokolov, A.B. Podgorbunsky, A.Yu. Ustinov, V.Yu. Mayorov, V.G. Kuryavyi, S.L. Sinebryukhov
    J. Mater. Sci. Technol., 2020, 54 (0): 181-189.  DOI: 10.1016/j.jmst.2020.02.068
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    TiO2-B/anatase nanotubes doped by vanadium have been synthesized through a facile one-step hydrothermal reaction. The material shows a mesoporous structure with a specific surface area of 179.1 m2 g-1. XPS data presume the presence of V3+, V4+, V5+, and Ti3+ in doped TiO2-B/anatase. As found by XRD and EIS investigations, the vanadium expands bronze titania crystal structure and enhances the conductivity of material by three orders of magnitude. When tested for lithium storage, the V-modified titania nanotubes show a specific capacity of 133 mA h g-1 after 100 charge/discharge cycles at the current density of 3000 mA g-1 with a Coulombic efficiency of around 98.9%, resulting in its good cycleability. The material still possesses a reversible capacity of 114 mA h g-1 at a very high current load of 6000 mA g-1, demonstrating superior rate characteristics for secondary lithium batteries. Furthermore, V-doped TiO2-B/anatase mesoporous nanotubes show promise performance as anode material for sodium-ion batteries, delivering about 119 mA h g-1 and 101 mA h g-1 at the current loads of 10 and 1500 mA g-1, respectively.

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    Seeded growth of Ti-46Al-8Nb polysynthetically twinned crystals with an ultra-high elongation
    Hao Jin, Qing Jia, Quangang Xian, Ronghua Liu, Yuyou Cui, Dongsheng Xu, Rui Yang
    J. Mater. Sci. Technol., 2020, 54 (0): 190-195.  DOI: 10.1016/j.jmst.2019.10.046
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    Large size polysynthetically twinned crystals of Ti-46Al-8Nb alloy with a parallel lamellar microstructure were successfully prepared using a Ti-43Al-3Si seed by our new operation. A large amount of columnar B2 phase paralleling to the growth direction was found in the final lamellar microstructure. Higher growth rate (>30?mm/h) led to the failure of seeding process. Based on these results, a new mechanism is proposed to describe the seeding process of the hypo-peritectic TiAl alloys. The peritectic α phase is suggested to directly nucleate from the melt, and then act as nucleus for transformed α phase in the subsequent β to α transformation. At the higher growth rate, the appearance of β phase secondary dendrites and homogeneous nucleation lead to the failure of seeding process. High Nb addition leads to a large amount of residual β phase, and these β dendrites finally evolve into B2 phase. The room temperature tensile elongation was measured to be 11.9-18.5% for Ti-46Al-8Nb PST crystals, which is the highest ever reported value for TiAl based alloys.

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    Tailoring grain growth and solid solution strengthening of single-phase CrCoNi medium-entropy alloys by solute selection
    G.W. Hu, L.C. Zeng, H. Du, X.W. Liu, Y. Wu, P. Gong, Z.T. Fan, Q. Hu, E.P. George
    J. Mater. Sci. Technol., 2020, 54 (0): 196-205.  DOI: 10.1016/j.jmst.2020.02.073
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    In the present study, we selected solutes to be added to the CrCoNi medium-entropy alloy (MEA) based on the mismatch of self-diffusion activation energy (SDQ) between the alloying elements and constituent elements of the matrix, and then investigated their grain growth behavior and mechanical properties. Mo and Al were selected as the solutes for investigation primarily because they have higher and lower SDQ, respectively, than those of the matrix elements; a secondary factor was their higher and lower shear modulus. Their concentrations were fixed at 3 at.% each because previous work had shown these compositions to be single-phase solid solutions with the face-centered cubic structure. Three alloys were produced by arc melting, casting, homogenizing, cold rolling and annealing at various temperatures and times to produce samples with different grain sizes. They were (a) the base alloy CrCoNi, (b) the base alloy plus 3 at.% Mo, and (c) the base alloy plus 3 at.% Al. The activation energies for grain growth of the CrCoNi, CrCoNi-3Mo and CrCoNi-3Al MEAs were found to be ~251, ~368 and ~219?kJ/mol, respectively, consistent with the notion that elements with higher SDQ (in this study Mo) retard grain growth (likely by a solute-drag effect), whereas those with lower values (Al) accelerate grain growth. The room-temperature tensile properties show that Mo increases the yield strength by ~40 % but Al addition has a smaller strengthening effect consistent with their relative shear moduli. The yield strength as a function of grain size for the three single-phase MEAs follows the classical Hall-Petch relationship with much higher slopes (>600?MPa μm?0.5) than traditional solid solutions. This work shows that the grain growth kinetics and solid solution strengthening of the CrCoNi MEA can be tuned by selecting solute elements that have appropriate diffusion and physical properties.

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    Selective growth of tin whiskers from its alloys on Ti2SnC
    Jingwen Tang, Peigen Zhang, Yushuang Liu, Chengjie Lu, Yan Zhang, Wei He, Wubian Tian, Wei Zhang, Zhengming Sun
    J. Mater. Sci. Technol., 2020, 54 (0): 206-210.  DOI: 10.1016/j.jmst.2020.02.081
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    The spontaneous growth of metal whiskers has been investigated for more than 70 years. However, there is still no agreement on its growth mechanism, and moreover, new characteristics of this whiskering phenomenon continue to emerge. In this study, Ti2SnC is found to be capable of extracting Sn out of its alloys (SnBi, SnAg) by selectively growing Sn whiskers, and the Sn whiskers share the features of the traditional whiskers on platings and solders. Replacing the Ti2SnC substrate with TiC or SiC, under the same conditions, however, the selective growth of Sn whisker does not happen, which means Ti2SnC plays a critical role in it. Based on the unique crystal structure of Ti2SnC, active Sn atoms diffusing through the basal planes of Ti2SnC is proposed to explain the selectivity. The driving force is suggested to be the high interfacial energy between Ti2SnC and tin. This study is of importance to further understand the growth mechanism of metallic whiskers, and it may be also possible to be harnessed to develop paradigm-shifting technologies of metal purification and metallic whisker/nanowire preparation.

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    Microstructure and cavitation erosion behavior of sputtered NiCrAlTi coatings with and without N incorporations
    Zhengliang Liu, Shenglong Zhu, Mingli Shen, Yixuan Jia, Wen Wang, Fuhui Wang
    J. Mater. Sci. Technol., 2020, 54 (0): 211-222.  DOI: 10.1016/j.jmst.2020.02.072
    Abstract   HTML   PDF

    The NiCrAlTi coatings free of N and with N incorporations were deposited on austenitic stainless steel 304L by magnetron sputtering in Ar and in gas mixture of Ar and N2, respectively. The N incorporated in the coatings existed as nitride precipitates (from ~3 vol.% to ~17 vol.%) after vacuum annealing. All the NiCrAlTi coatings, whatever free of N or with N incorporations, exhibited better resistance against cavitation erosion than ion plating TiN coating and the substrate 304 L in ultrasonic cavitation tests. The NiCrAlTi coating free of N incorporation presents superior cavitation erosion resistance. However, the nitrogen incorporation within the NiCrAlTi coatings showed negative effects on the resistance against cavitation erosion.

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    3D carbon network supported porous SiOC ceramics with enhanced microwave absorption properties
    Chen Chen, Sifan Zeng, Xiaochun Han, Yongqiang Tan, Wanlin Feng, Huahai Shen, Shuming Peng, Haibin Zhang
    J. Mater. Sci. Technol., 2020, 54 (0): 223-229.  DOI: 10.1016/j.jmst.2020.03.018
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    Porous SiOC ceramic was successfully prepared by pyrolysis of dimethylsilicone oil, silane coupling agent and melamine foam. The microwave absorbing properties of porous SiOC were studied for the first time. At the matching layer thickness of 3.0 mm, the paraffin-based composite with porous SiOC displays a minimum reflection coefficient (RC) of -39.13 dB (11.76 GHz) and an effective absorption bandwidth (EAB) of 4.64 GHz which are much larger than that of paraffin-based composite with ordinary SiOC. It is found that the porous structure of SiOC is crucial to achieve its high microwave absorption performance by improving both the polarization loss and conduction loss. The enhanced polarization loss is originated from the dipole polarization and interfacial polarization, while the improvement of conduction loss is attributed to the carbon skeleton of porous SiOC. These results indicate that porous SiOC ceramic is a promising candidate for high-performance ceramic-based microwave absorbing materials.

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    Warm white emission of LaSr2F7:Dy3+/Eu3+ NPs with excellent thermal stability for indoor illumination
    Yongbin Hua, Jae Su Yu
    J. Mater. Sci. Technol., 2020, 54 (0): 230-239.  DOI: 10.1016/j.jmst.2020.02.066
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    The novel single Dy3+-activated and Dy3+/Eu3+ co-activated LaSr2F7 NPs-based phosphors were successfully synthesized via a simple precipitation reaction method at room temperature. The phase formations and cell parameters of single Dy3+-activated and Dy3+/Eu3+ co-activated LaSr2F7 NPs were verified in detail by the Rietveld refinement technique based on the recorded X-ray diffraction patterns. The doping concentration of single Dy3+-activated LaSr2F7 NPs was optimized to be 0.1 mol with the concentration quenching dominated by the electric dipole-dipole interaction. Meanwhile, a variety of Eu3+-activated La0.9Sr2F7:0.1Dy3+ NPs exhibited tunable luminescent properties and emitted warm white light in close to standard warm white light under 363 nm excitation. The valid energy transfer (ET) efficiency from Dy3+ to Eu3+ ions was estimated to be about 86.02% based on the emission intensity while the electric dipole-quadrupole interaction dominated the concentration quenching mechanism in ET process. Eventually, the thermal quenching of the obtained samples was studied, showing the excellent thermal stability. All the results manifest that Eu3+-activated LaSr2F7:Dy3+ NPs could emit warm white light with excellent thermal stability for indoor illumination.

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ISSN: 1005-0302
CN: 21-1315/TG
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