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CN 21-1315/TG
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      05 October 2019, Volume 35 Issue 10 Previous Issue   
    Orginal Article
    Optimization of annealing treatment and comprehensive properties of Cu-containing Ti6Al4V-xCu alloys
    Cong Peng, Yang Liu, Hui Liu, Shuyuan Zhang, Chunguang Bai, Yizao Wan, Ling Ren, Ke Yang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2121-2131.   DOI: 10.1016/j.jmst.2019.05.020

    The Ti6Al4V-Cu alloy was reported to show good antibacterial properties, which was promising to reduce the hazard of the bacterial infection problem. For the purpose of preparing Ti6Al4V-Cu alloy with satisfied comprehensive properties, it’s important to study the heat treatment and the appropriate Cu content of the alloy. In this study, high Cu content Ti6Al4V-xCu (x = 4.5, 6, 7.5 wt%) alloys were prepared, and firstly the annealing heat treatments were optimized in the α+β+Ti2Cu triple phase region to obtain satisfied tensile mechanical properties. Then the effect of Cu content on the tribological property, corrosion resistance, antibacterial activity and cytotoxicity of the Ti6Al4V-xCu alloys were systematically studied to obtain the appropriate Cu content. The results showed that the optimal annealing temperatures for Ti6Al4V-xCu (x = 4.5, 6, 7.5 wt%) alloys were 720, 740 and 760 °C, respectively, which was resulted from the proper volume fractions of α, β and Ti2Cu phases in the microstructure. The additions of 4.5 wt% and 6 wt% Cu into the medical Ti6Al4V alloy could enhance the wear resistance and corrosion resistance of the alloy, but the addition of 7.5 wt% Cu showed an opposite effect. With the increase of the Cu content, the antibacterial property was enhanced due to the increased volume fraction of Ti2Cu phase in the microstructure, but when the Cu content was increased to 7.5 wt%, cytotoxicity was presented. A medium Cu content of 6 wt%, with annealing temperature of 740 °C make the alloy possesses the best comprehensive properties of tensile properties, wear resistance, corrosion resistance, antibacterial property and biocompatibility, which is promising for future medical applications.

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    Preparation and hydrogen storage properties of MgH2-trimesic acid-TM MOF (TM=Co, Fe) composites
    Zhewen Ma, Jianxin Zou, Darvaish Khan, Wen Zhu, Chuanzhu Hu, Xiaoqin Zeng, Wenjiang Ding
    J. Mater. Sci. Technol.. 2019, 35 (10): 2132-2143.   DOI: 10.1016/j.jmst.2019.05.049

    Two kinds of metal-organic frameworks (MOFs) based on Co (II) and Fe (II) as metal ions and trimasic acid (TMA) as organic linker were synthesized. They were used to prepare corresponding MgH2-TM MOF (TM = Co, Fe) composites via ball-milling. X-ray diffraction analyses show the formation of Mg2Co and α-Fe phases in MgH2-TM MOF composites after decomposition. Both of the well dispersed Mg2Co and α-Fe nanoparticles exhibit considerable catalytic efficiency in accelerating the sorption kinetics of MgH2. The dehydrogenated MgH2-Fe MOF composite shows faster hydriding kinetics than the pure MgH2 and MgH2-Co MOF. Meanwhile, the apparent dehydrogenation activation energy (Ed) of the MgH2-Co MOF and MgH2-Fe MOF composites are 151.3 ± 9.4 and 142.3 ± 6.5 kJ/mol H2, both of which are lower than that of pure MgH2 (181.4 ± 9.2 kJ/mol H2). The improvement on the sorption kinetics of the MgH2-TM MOF powders is mainly attributed to the catalytic effects of nano-sized Mg2Co and α-Fe formed on the surface of Mg/MgH2 particles.

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    Low-valence ion addition induced more compact passive films on nickel-copper nano-coatings
    Quangquan Do, Hongze An, Guozhe Meng, Weihua Li, Lai-Chang Zhang, Yangqiu Wang, Bin Liu, Junyi Wang, Fuhui Wang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2144-2155.   DOI: 10.1016/j.jmst.2019.05.051

    Ni-Cu nano-coatings were prepared by pulsed electroplating technique in the baths containing various amount of boric acid. Their microstructure, morphologies and corrosion resistance were characterized in detail. The addition of boric acid strongly influences on the microstructure of the Ni-Cu coatings. The coating with a grain size of 130 nm, obtained from the bath containing 35 g L-1 boric acid, shows the highest corrosion resistance. This is attributed to the low-valence Cu ion (Cu+) additions in nickel oxide, which could significantly decrease the oxygen ion vacancy density in the passive film to form a more compact passive film. The higher Cu+ additions and the lower diffusivity of point defects (D0) are responsible for the formation of more compact passive film on the coating obtained from the bath with 35 g L-1 boric acid.

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    Nanocrystalline Ti49.2Ni50.8 shape memory alloy as orthopaedic implant material with better performance
    H.F. Li, F.L. Nie, Y.F. Zheng, Y. Cheng, S.C. Wei, R.Z. Valiev
    J. Mater. Sci. Technol.. 2019, 35 (10): 2156-2162.   DOI: 10.1016/j.jmst.2019.04.026

    TiNi alloys, with their unique shape memory effects and super elastic properties, occupy an indispensable place in the family of metallic biomaterials. In the past years, surface treatment is the main technique to improve the bioinert nature of microcrystalline TiNi alloys and inhibit on the release of toxic nickel ions to obtain excellent osteogenesis and osseointegration function. In the present study, nanocrystalline Ti49.2Ni50.8 alloy has been fabricated via equal channel angular pressing (ECAP), and the in vitro and in vivo studies revealed that it had enhanced cell viability, adhesion, proliferation, ALP (Alkaline phosphatase) activity and mineralization, and increased periphery thickness of new bone, in comparison to the commercial coarse-grained counterpart. These findings indicate that the reduction of grain size is beneficial to increasing the biocompatibility of Ti49.2Ni50.8 shape memory alloy.

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    Brazing temperature-dependent interfacial reaction layer features between CBN and Cu-Sn-Ti active filler metal
    Yonggang Fan, Junxiang Fan, Cong Wang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2163-2168.   DOI: 10.1016/j.jmst.2019.05.041

    CBN/Cu-Sn-Ti (CBN: cubic boron nitride) composites are prepared by active brazing sintering at 1123 K, 1173 K, 1223 K and 1273 K, respectively. The effects of brazing temperature on the wettability, interfacial characteristics, and elemental distribution variations are fully investigated. When the brazing temperature is below 1223 K, completely uncoated and/or partially coated CBN particles with sharp edges can still be observed, and the reaction layer, mainly composed of TiN and TiB2, appears to be thin and uneven. When the brazing temperature is 1223 K, all CBN particles are completely coated, suggesting that adequate wetting has taken place. Besides, as Ti diffuses thoroughly and enriches the interface, the reaction layer, filled primarily by TiN, TiB2 and TiB, becomes thicker (about 1.30 μm), more uniform, stable and continuous. Further increasing the temperature to 1273 K is unnecessary or even harmful as the reaction layer thickness undergoes negligible change yet some tiny micro-cracks appear on the interface, which may likely deteriorate the grinding capability of the final brazing products.

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    3-Phase hierarchical graphene-based epoxy nanocomposite laminates for automotive applications
    Ahmed Elmarakbi, Panagiotis Karagiannidis, Alessandra Ciappa, Franco Innocente, Francesco Galise, Brunetto Martorana, Francesco Bertocchi, Francesco Cristiano, Elvira Villaro ábalos, Julio Gómez
    J. Mater. Sci. Technol.. 2019, 35 (10): 2169-2177.   DOI: 10.1016/j.jmst.2019.05.033

    Two different types of graphene flakes were produced following solution processing methods and dispersed using shear mixing in a bifunctional (A) and a multifunctional (B) epoxy resin at a concentration of 0.8 and 0.6 wt%, respectively. The graphene/epoxy resin mixtures were used to impregnate unidirectional carbon fibre tapes. These prepregs were stacked (seven plies) and cured to produce laminates. The interlaminar fracture toughness (mode-I) of the carbon fiber/graphene epoxy laminates with resin B showed over 56% improvement compared with the laminate without graphene. Single lap joints were prepared using the laminates as adherents and polyurethane adhesives (Sika 7666 and Sika 7888). The addition of graphene improved considerably the adhesion strength from 3.3 to 21 MPa (sample prepared with resin A and Sika 7888) highlighting the potential of graphene as a secondary filler in carbon fibre reinforced polymer composites.

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    N-doped ordered mesoporous carbon spheres derived by confined pyrolysis for high supercapacitor performance
    Juan Du, Lei Liu, Yifeng Yu, Yue Zhang, Haijun Lv, Aibing Chen
    J. Mater. Sci. Technol.. 2019, 35 (10): 2178-2186.   DOI: 10.1016/j.jmst.2019.05.029

    Herein, we report a confined pyrolysis strategy to prepare mesoporous carbon nanospheres by which surface area of carbon spheres is increased, pore size is enlarged and effective N-doping is achieved. In this method, the mesoporous polymer sphere as carbon precursor and 2-methylimidazole as nitrogen precursor are encapsulated in a compact silica shell which provides a confined nano-space for the pyrolysis treatment. The in situ generated gases from mesoporous polymer sphere and 2-methylimidazole under pyrolysis diffuse into the pores of mesoporous polymer sphere in the confined compact silica shell, resulting in increased surface area, larger pore size and N-doping due to self-activation effect. As electrodes in supercapacitor, the N-doped mesoporous carbon nanospheres exhibit a significantly enhanced specific capacitance of 326 F g-1 at 0.5 A g-1, which is 2 times higher than that of mesoporous carbon spheres under unconfined pyrolysis condition, exhibiting its potential for electrode materials with high performance.

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    A self-powered temperature-sensitive electronic-skin based on tribotronic effect of PDMS/PANI nanostructures
    Zize Liu, Tianming Zhao, Hongye Guan, Tianyan Zhong, Haoxuan He, Lili Xing, Xinyu Xue
    J. Mater. Sci. Technol.. 2019, 35 (10): 2187-2193.   DOI: 10.1016/j.jmst.2019.05.038

    A new self-powered temperature-sensitive electronic-skin (e-skin) for real-time monitoring body temperature without external electricity power was fabricated from patterned polydimethylsiloxane/polyaniline (PDMS/PANI) nanostructures. The e-skin can be feasibly attached on the human body and driven by the mechanical motion energy through triboelectric effect. The outputting triboelectric impulse of the PDMS/PANI units is significantly dependent on the local surface temperature of the e-skin, serving as both the power source and temperature sensing signal. The outputting current of the e-skin increases with increasing surface temperature of the device. Under applied bending deformation, the response of the e-skin is up to 63.6 for 38.6 °C. The e-skin can detect minimum temperature change of 0.4 °C. The working mechanism can be ascribed to the coupling effect of triboelectric and semiconductor properties (tribotronic effect). A practical application of the e-skin attaching on the human body for detecting the body temperature range of 36.5-42.0 °C has been simply demonstrated. This work provides a viable method for real-time monitoring body temperature, and can promote the development of wearable temperature sensors and self-powered multifunctional nanosystems.

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    Electrical and optical modulation on ferroelectric properties of P(VDF-TrFE) thin film capacitors
    Xiaohan Li, Biaohong Huang, Weijin Hu, Zhidong Zhang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2194-2199.   DOI: 10.1016/j.jmst.2019.05.040

    Modulating the ferroelectric properties of P(VDF-TrFE) polymers both electrically and optically could open up new opportunities for their applications in non-volatile memories and sensors. Here by using the Nb:SrTiO3 semiconductor as electrode compared with metal Au electrode, we report on the modulation of ferroelectric properties of P(VDF-TrFE) thin film capacitors both by electric field and UV light. A ferroelectric hysteresis loop shift together with the asymmetric switching behavior has been observed when using semiconducting electrode, which could be explained by the band alignment model based on interfacial charge screening. On the basis of band bending near the ferroelectric/semiconductor interface, we could further modulate the ferroelectric switching behaviors reversibly by UV light illumination. Our research provides a new route to engineer the ferroelectric properties of P(VDF-TrFE) polymer thin film capacitors, promising their applications in optoelectronic devices.

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    Grain-scale deformation in a Mg-0.8 wt% Y alloy using crystal plasticity finite element method
    Wenxue Li, Leyun Wang, Bijin Zhou, Chuanlai Liu, Xiaoqin Zeng
    J. Mater. Sci. Technol.. 2019, 35 (10): 2200-2206.   DOI: 10.1016/j.jmst.2019.04.030

    Magnesium (Mg) alloys with hexagonal close-packed (HCP) structure usually have a poor ductility at room temperature. The addition of yttrium (Y) can improve the ductility of Mg alloys. To understand the underlying mechanism, crystal plasticity finite element method (CPFEM) was employed to simulate the tensile deformation of a Mg-0.8 wt% Y alloy. The simulated stress-strain curve and the grain-scale slip activities were compared with an in-situ tensile test conducted in a scanning electron microscope. According to the CPFEM result, basal slip is the dominant deformation mode in the plastic deformation stage, accounting for about 50% of total strain. Prismatic slip and pyramidal 〈a〉 slip are responsible for about 25% and 20% of the total strain, respectively. Pyramidal 〈c + a〉 slip and twinning, on the other hand, accommodate much less strain.

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    Performance enhancement of paper-based SERS chips by shell-isolated nanoparticle-enhanced Raman spectroscopy
    Mingze Sun, Binghan Li, Xiaojia Liu, Jiayin Chen, Taotao Mu, Lianqing Zhu, Jinhong Guo, Xing Ma
    J. Mater. Sci. Technol.. 2019, 35 (10): 2207-2212.   DOI: 10.1016/j.jmst.2019.05.055

    Paper-based flexible surface-enhanced Raman scattering (SERS) chips have been demonstrated to have great potential for future practical applications in point-of-care testing (POCT) due to the potentials of massive fabrication, low cost, efficient sample collection and short signal acquisition time. In this work, common filter paper and Ag@SiO2core-shell nanoparticles (NP) have been utilized to fabricate SERS chips based on shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS). The SERS performance of the chips for POCT applications was systematically investigated. We used crystal violet as the model molecule to study the influence of the size of the Ag core and the thickness of the SiO2coating layer on the SERS activity and then the morphology optimized Ag@SiO2core-shell NPs was employed to detect thiram. By utilizing the smartphone as a miniaturized Raman spectral analyzer, high SERS sensitivity of thiram with a detection limit of 10-9M was obtained. The study on the stability of the SERS chips shows that a SiO2shell of 3 nm can effectively protect the as-prepared SERS chips against oxidation in ambient atmosphere without seriously weakening the SERS sensitivity. Our results indicated that the SERS chips by SHINERS had great potential of practical application, such as pesticide residues detection in POCT.

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    Effect of grain refinement on the hydrogen embrittlement of 304 austenitic stainless steel
    Y.H. Fan, B. Zhang, J.Q. Wang, E.-H. Han, W. Ke
    J. Mater. Sci. Technol.. 2019, 35 (10): 2213-2219.   DOI: 10.1016/j.jmst.2019.03.043

    The effect of grain size (in the range from 4 μm to 12 μm) on the hydrogen embrittlement (HE) of 304 austenitic stainless steel (ASS) was studied. HE susceptibility result shows that HE resistance increases with grain refinement. Electron backscattered diffraction kernel average misorientation (EBSD-KAM) mapping shows that the strain localization can be mitigated by grain refinement. Hence, strain localization sites which act as highways for hydrogen diffusion and preferred crack initiation sites can be reduced along with grain refinement, leading to a high HE resistance. Meanwhile, grain size shows no influence on the strain induced martensite (SIM) transformation during the hydrogen charging slow strain tensile test (SSRT). Hence, the SIM formed during hydrogen charging SSRT is not responsible for the different HE resistance of 304 ASSs with various grain sizes. Hydrogen diffusion is supposed to be controlled by a competition between short-circuit diffusion along random grain boundary (RGB) and hydrogen trapping at dislocations, leading to a maximum hydrogen diffusion coefficient in the 304 ASS with an average grain size of 8 μm.

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    Enhanced tensile plasticity of a CuZr-based bulk metallic glass composite induced by ion irradiation
    Peng Xue, Simon Pauly, Weimin Gan, Songshan Jiang, Hongbo Fan, Zhiliang Ning, Yongjiang Huang, Jianfei Sun
    J. Mater. Sci. Technol.. 2019, 35 (10): 2221-2226.   DOI: 10.1016/j.jmst.2019.06.003

    N+ ion irradiation is utilized to tune the structure and mechanical properties of a Cu48Zr47.2Al4Nb0.8 bulk metallic glass composite (BMGC). Ion irradiation increases the disorder near the surface, as probed by neutron diffraction, and, moreover, causes the phase transformation from B2 CuZr to B19’ CuZr martensitic phase in the studied BMGC. The tensile plasticity of the BMGC is dramatically improved after ion irradiation, which results from multiple shear banding on the surface and the martensitic transformation of the B2 to B19’ CuZr martensitic phase. The experimental results are strongly corroborated by complementary molecular dynamic simulations.

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    (TiZrHf)P2O7: An equimolar multicomponent or high entropy ceramic with good thermal stability and low thermal conductivity
    Zifan Zhao, Huimin Xiang, ZhiDai Fu, Zhijian Peng, Yanchun Zhou
    J. Mater. Sci. Technol.. 2019, 35 (10): 2227-2231.   DOI: 10.1016/j.jmst.2019.05.030

    ZrP2O7 is a promising material for high temperature insulating applications. However, decomposition above 1400 °C is the bottleneck that limiting its application at high temperatures. To improve the thermal stability, a novel multicomponent equimolar solid solution (TiZrHf)P2O7 was designed and successfully synthesized in this work inspired by high-entropy ceramic (HEC) concept. The as-synthesized (TiZrHf)P2O7 exhibits good thermal stability, which is not decomposed after heating at 1550 °C for 3 h. It also shows lower thermal conductivity (0.78 W m-1 K-1) compared to the constituting metal pyrophosphates TiP2O7, ZrP2O7 and HfP2O7. The combination of high thermal stability and low thermal conductivity renders (TiZrHf)P2O7 promising for high temperature thermal insulating applications.

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    Gas sensing selectivity of oxygen-regulated SnO2 films with different microstructure and texture
    Ruiwu Li, Yanwen Zhou, Maolin Sun, Zhen Gong, Yuanyuan Guo, Xitao Yin, Fayu Wu, Wutong Ding
    J. Mater. Sci. Technol.. 2019, 35 (10): 2232-2237.   DOI: 10.1016/j.jmst.2019.06.005

    The selectivity of gas sensing materials is increasingly important for their applications. The oxygen-regulated SnO2 films with (110) and (101) preferred orientation were obtained through magnetron sputtering, followed by annealing treatment. Their micro-structure, surface morphology and gas response were investigated by advanced structural characterization and property measurement. The results showed that the as-prepared (110)-oriented SnO2 film was oxygen-rich and had more adsorption sites while the as-prepared (101)-oriented SnO2 film was oxygen-poor and more sensitive to de-oxidation. H2 gas sensitivity, response speed, selectivity between H2 and CO of the (110)-orientated SnO2 film was superior to that of the (101)-orientated SnO2 film. After treated at high temperature and high vacuum, the reduction of gas-sensing properties of the annealed (110) SnO2 film was much more than that of the annealed (101) SnO2 film. The lattice oxygen was responsible for the difference in gas-sensing response between (110) and (101)-oriented SnO2 films under oxygen regulation. This work indicated the gas-sensing selectivity of the different crystal planes in SnO2 film, providing a significant reference for design and extension of the related materials.

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    Selective laser melting of NiTi alloy with superior tensile property and shape memory effect
    Zhiwei Xiong, Zhonghan Li, Zhen Sun, Shijie Hao, Ying Yang, Meng Li, Changhui Song, Ping Qiu, Lishan Cui
    J. Mater. Sci. Technol.. 2019, 35 (10): 2238-2242.   DOI: 10.1016/j.jmst.2019.05.015

    It is a challenge to develop complex-shaped NiTi shape memory alloy parts by traditional processing methods, due to the poor machinability of NiTi alloy. It is reported that selective laser melting (SLM) of additive manufacturing could overcome this problem. However, the reported SLM-produced NiTi exhibits poor tensile ductility due to the inner defects and adverse unidirectional columnar grains from SLM process. In this work, the defect-less SLM-NiTi with nondirective columnar grains was fabricated by optimizing the intraformational laser scanning length and interformational laser scanning direction. The obtained lath-shaped SLM-NiTi sample exhibits tensile strain of 15.6%, more than twice of the reported maximum result ($\widetilde{7}$%). Besides, the SLM-NiTi part with complex geometry displays a shape memory recovery of 99% under compressive deformation of 50%.

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    A green and effective corrosion inhibitor of functionalized carbon dots
    Yuwei Ye, Dongping Yang, Hao Chen
    J. Mater. Sci. Technol.. 2019, 35 (10): 2243-2253.   DOI: 10.1016/j.jmst.2019.05.045

    In this work, a green and effective corrosion inhibitor of functionalized carbon dots (FCDs) was synthesized by the conjugation of imidazole and citric acid carbon dots (CA-CDs). The corrosion inhibition behavior of FCDs for Q235 steel in 1 M HCl solution was systematically investigated by electrochemical analysis, corrosion morphology and adsorption isotherm. The electrochemical results implied that the as-prepared FCDs inhibitor could effectively suppress the corrosion of Q235 steel in 1 M HCl solution. At the same time, the inhibition efficiency of steel in 1 M HCl solution was more than 90% when the inhibitor concentration exceeded 100 mg/L. This excellent property was attributed to the coverage of adsorption film on the steel surface, which conformed to the Langmuir adsorption model. In addition, the analysis of adsorption isotherm displayed that the adsorption mechanism was the physicochemical interaction at the steel/solution interface.

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    In vitro and in vivo studies on the biodegradable behavior and bone response of Mg69Zn27Ca4 metal glass for treatment of bone defect
    Junxiu Chen, Jiahui Dong, Huameng Fu, Haifeng Zhang, Lili Tan, Dewei Zhao, Ke Yang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2254-2262.   DOI: 10.1016/j.jmst.2019.04.031

    In the present work, the biodegradable behavior, cytocompatibility and osteogenesis activity of a Mg69Zn27Ca4 metal glass were investigated. Electrochemical test, immersion test, cytotoxicity test and histopathological evaluation were carried out. The results showed that there was a dense protective layer formed on the surface of Mg69Zn27Ca4 metal glass which could inhibit the degradation process in the Hank’s solution. In vitro cytotoxicity test showed that Mg69Zn27Ca4 metal glass had good biocompatibility. Histopathological evaluation showed that the degradation of Mg69Zn27Ca4 metal glass could promote the new bone formation with no obvious inflammatory reactions. After 2 months implantation, the diameter of the bone defect was reduced from the original φ6 mm to φ3.35 ± 0.40 mm with the degradation of Mg69Zn27Ca4 metal glass. Therefore, it can be concluded that Mg69Zn27Ca4 glass has great potential to be used as bone substitutes.

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    High density stacking faults of {10$\bar{1}$1} compression twin in magnesium alloys
    Bo Zhou, Manling Sui
    J. Mater. Sci. Technol.. 2019, 35 (10): 2263-2268.   DOI: 10.1016/j.jmst.2019.05.042

    {10$\bar{1}$1} compression twins with high density stacking faults were studied at atomic scale using Cs-correction transmission electron microscopy. On one side of the {10$\bar{1}$1} twin boundary, there were many steps arranged alternately with the coherent twin boundaries. Most of the steps were linked with stacking faults inside twins. Burgers vector of twinning dislocations and the mismatch strain at steps were characterized. Due to the compressive mismatch strain at steps, the high density stacking faults inside twins were formed at twin tips during twinning process. The localized strain at the steps would be related to the crack nucleation in magnesium alloys.

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    Texture control by {10-12} twinning to improve the formability of Mg alloys: A review
    Bo Song, Qingshan Yang, Tao Zhou, Linjiang Chai, Ning Guo, Tingting Liu, Shengfeng Guo, Renlong Xin
    J. Mater. Sci. Technol.. 2019, 35 (10): 2269-2282.   DOI: 10.1016/j.jmst.2019.03.045

    Texture control of wrought Mg alloys, particularly in rolled Mg alloy sheets, has been an important research topic for the past several decades because it has significant influence on stretch formability at room temperature. For Mg alloys, {10-12} twinning can be easily activated and causes a $\widetilde{8}$6.3° lattice rotation. Thus, pre-twinning deformation is considered as an effective and low-cost method for texture control in wrought Mg and its alloys. Furthermore, it has been verified that texture control via pre-twinning deformation can remarkably improve stretch formability of rolled Mg alloy sheets. In this review, recent researches on texture control via twinning deformation and its influence on stretch formability will be critically reviewed. The main contents include the micro-mechanism and impact factors of control in twin-orientation, plastic processing techniques of pre-inducing twins and the application of pre-induced twins in improvement of stretch formability. Finally, further research directions on this field were proposed.

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    Magnetic properties and magnetocaloric effects of Gd65(Cu,Co,Mn)35 amorphous ribbons
    Peng Jia, Leipeng Duan, Kang Wang, Engang Wang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2283-2287.   DOI: 10.1016/j.jmst.2019.05.056

    The magnetic phase transition and magnetocaloric effects of Gd65(Cu,Co,Mn)35 amorphous ribbons were investigated. The increased Mn substitution for Co or Mn substitution for Cu led into a higher second-order magnetic phase transformation temperature, near 200 K in all ribbons. Under the field change of 7 T, a maximum entropy change (ΔSmmax) of 6 J kg-1 K-1 was achieved in Gd65Cu10Co20Mn5 ribbon and slightly dependent on the compositions. With varied composition, a full width at half of ΔSmmax was greatly widened to be over than 180 K for Gd65Cu15Co10Mn10 ribbon. The refrigeration capacity was also greatly enhanced to 1000 J kg-1 for Gd65Cu20Co10Mn5 ribbon, which was even excellent compared with other Gd-based amorphous systems.

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    Chlorine doped graphitic carbon nitride nanorings as an efficient photoresponsive catalyst for water oxidation and organic decomposition
    Er-Xun Han, Yuan-Yuan Li, Qi-Hao Wang, Wei-Qing Huang, Leng Luo, Wangyu Hu, Gui-Fang Huang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2288-2296.   DOI: 10.1016/j.jmst.2019.05.057

    Rationally engineering the microstructure and electronic structure of catalysts to induce high activity for versatile applications remains a challenge. Herein, chlorine doped graphitic carbon nitride (Cl-doped g-C3N4) nanorings have been designed as a superior photocatalyst for pollutant degradation and oxygen evolution reaction (OER). Remarkably, Cl-doped g-C3N4 nanorings display enhanced OER performance with a small overpotential of approximately 290 mV at current density of 10 mA cm-2 and Tafel slope of 83 mV dec-1, possessing comparable OER activity to precious metal oxides RuO2 and IrO2/C. The excellent catalytic performance of Cl-doped g-C3N4 nanorings originates from the strong oxidation capability, abundant active sites exposed and efficient charge transfer. More importantly, visible light irradiation gives rise to a prominent improvement of the OER performance, reducing the OER overpotential and Tafel slope by 140 mV and 28 mV dec-1, respectively, demonstrating the striking photo-responsive OER activity of Cl-doped g-C3N4 nanorings. The great photo-induced improvement in OER activity would be related to the efficient charge transfer and the ?OH radicals arising spontaneously on CN-Cl100 catalyst upon light irradiation. This work establishes Cl-doped g-C3N4 nanorings as a highly competitive metal-free candidate for photoelectrochemical energy conversion and environmental cleaning application.

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    Prediction of stable high-pressure structures of tantalum nitride TaN2
    Wandong Xing, Zijie Wei, Rong Yu, Fanyan Meng
    J. Mater. Sci. Technol.. 2019, 35 (10): 2297-2304.   DOI: 10.1016/j.jmst.2019.05.035

    Structure searches based on a combination of first-principles calculations and a particle swarm optimization technique unravel two new stable high-pressure structures (C2/m and Cmce) for TaN2. The structural features, mechanical properties, formation enthalpies, electronic structure, and phase diagram of TaN2 are fully investigated. Being mechanically and dynamically stable, the two phases could be made metastable experimentally at ambient conditions.

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    Ta-doped modified Gd2O3 film for a novel high k gate dielectric
    Shuan Li, Yanqing Wu, Guoling Li, Hongen Yu, Kai Fu, Yong Wu, Jie Zhang, Wenhuai Tian, Xingguo Li
    J. Mater. Sci. Technol.. 2019, 35 (10): 2305-2311.   DOI: 10.1016/j.jmst.2019.05.028

    Gadolinium oxide (Gd2O3) film has potential as a candidate gate dielectric to replace HfO2. In this work, we provide a simple method by trace Ta ($\widetilde{1}$%) doping to significantly improve the dielectric properties of Gd2O3 film. And effects of annealing temperatures of Ta-doped Gd2O3 (GTO) films are investigated in detail. Results show that GTO film annealed at 500 °C exhibits excellent performance as a novel gate dielectric material for integrated circuit, showing a small surface roughness of 0.199 nm, a large band gap of 5.45 eV, a high dielectric constant (k) of 21.2 and a low leakage current density (Jg) of 2.10 × 10-3 A/cm2. All properties of GTO films are superior to pure Gd2O3 films and these GTO films meet the requirements for next-generation gate dielectrics. In addition, impedance spectrum is first used to analyze the equivalent circuit of GTO based metal-oxide-semiconductor (MOS) capacitors, which represents a new insight to understand observed electrical behaviors.

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    Construction of one dimensional ZnWO4@SnWO4 core-shell heterostructure for boosted photocatalytic performance
    Huaqiang Zhuang, Wentao Xu, Liqin Lin, Mianli Huang, Miaoqiong Xu, Shaoyun Chen, Zhenping Cai
    J. Mater. Sci. Technol.. 2019, 35 (10): 2312-2318.   DOI: 10.1016/j.jmst.2019.05.036

    The one-dimensional ZnWO4@SnWO4 photocatalyst with a core-shell heterostructure was successfully constructed by a simple two-step method. It is interesting to note that ZnWO4@SnWO4 composite photocatalyst owns a higher photocatalytic activity for RhB degradation under visible light irradiation. The introduction of SnWO4 shell layer, which forms a clear heterogenous interface between ZnWO4 and SnWO4, increases the photo-absorption efficiency of ZnWO4 nanorods. In addition, its band-edge absorption evidently shifts toward the visible region. Based on the photoelectrochemical (PEC) and electron spin resonance (ESR) measurements, it is found that the photocatalytic activity was attributed to the efficient separation and transfer of photo-generated charge carriers. Hence, they can produced more hydroxyl radical (?OH) as the main active species in the photocatalytic reaction process.

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    Dispersed distribution derived integrated anode for lithium ion battery
    Boya Zhang, Dongxiang Li, Jiaqi Wan
    J. Mater. Sci. Technol.. 2019, 35 (10): 2319-2324.   DOI: 10.1016/j.jmst.2019.05.022

    With the development of portable communication devices and electric vehicles, there is a great need for energy storage devices with lighter weight and higher energy density. In this paper, a new method by combining waster-paper-synthesized conductive paper (CP) and active material MnO2 together is developed to obtain a new type of anode without any binder for lithium ion batteries. By this way, we can obtain low density anode with active material in CP, instead of the commonly-used heavy metal current collector. Also, binder has been abandoned, which are usually used to combine active material into anode, to further decrease weight. The multi walled carbon nanotube (MWCNT) was added in serves as a component of CP and the conductive agent for active material. Compared to traditional anode coated on Cu current collector, the CP-combined anode can greatly improve the electrochemical performance of active material MnO2. It can let more particles to fully participate in the reaction and therefore boost the specific capacity to a great extent (about 3 times higher). It delivered an initial specific capacity of 1629.9 mA h g-1 at a current density of 100 mA g-1 and maintained about 67% even after 100 cycles. What’s more, it shows reversible capacity of about 260 mA h g-1 at high current density of 1000 mA h g-1. Our original synthesis method of anode, which shows far-reaching referential value and environmental significance, can be generalized to other electrodes and other battery systems.

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    Synthesis of montmorillonite-chitosan hollow and hierarchical mesoporous spheres with single-template layer-by-layer assembly
    Peng Chen, Yunliang Zhao, Tianxing Chen, Tingting Zhang, Shaoxian Song
    J. Mater. Sci. Technol.. 2019, 35 (10): 2325-2330.   DOI: 10.1016/j.jmst.2019.05.046

    In order to develop a facile and precisely controlled approach to synthesize hierarchical mesoporous materials with tailored property, in this work, a novel study was carried out to fabricate montmorillonite-chitosan hollow and hierarchical mesoporous spheres (MMTNS@CS-HMPHS) based on single-template layer-by-layer (LbL) assembly. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area analysis and X-ray photoelectron spectroscopy (XPS) analyses were carried out to characterize the morphology and surface properties of MMTNS@CS-HMPHS. Benefitting from the unique lamellar structure of MMTNS, mesoporous channels are formed on the shell of MMTNS@CS hollow spheres, resulting in high surface area. Moreover, the surface functionalization and pore size of MMTNS@CS-HMPHS can be easily tuned, due to the tailored property through LbL assembly method. Besides the unique microstructure, MMTNS@CS-HMPHS also possesses the active sites generated from both MMT and chitosan, which greatly promotes its performance in fields of adsorption, drug delivery and catalyst supports, etc.

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    Microstructure and mechanical properties of FexCoCrNiMn high-entropy alloys
    Tao Zhang, Lijun Xin, Fufa Wu, Rongda Zhao, Jun Xiang, Minghua Chen, Songshan Jian, Yongjiang Huang, Shunhua Chen
    J. Mater. Sci. Technol.. 2019, 35 (10): 2331-2335.   DOI: 10.1016/j.jmst.2019.05.050

    The microstructure and tensile properties of FexCoCrNiMn high-entropy alloys (HEAs) were investigated. It was found that the FexCoCrNiMn HEA has a single face-centered cubic (fcc) structure in a wide range of Fe content. Further increasing the Fe content endowed the FexCoCrNiMn alloys with an fcc/body-centered cubic (bcc) dual-phase structure. The yield strength of the FexCoCrNiMn HEAs slightly decreased with the increase of Fe content. An excellent combination of strength and ductility was achieved in the FexCoCrNiMn HEA with higher Fe content, which can be attributed to the outstanding deformation coordination capability of the fcc/bcc dual phase structure.

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    Optimization of mechanical property, antibacterial property and corrosion resistance of Ti-Cu alloy for dental implant
    Jiewen Wang, Shuyuan Zhang, Ziqing Sun, Hai Wang, Ling Ren, Ke Yang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2336-2344.   DOI: 10.1016/j.jmst.2019.03.044

    Ti-Cu alloys with different Cu contents (3, 5 and 7 wt%) were fabricated and studied as novel antibacterial biomaterials for dental application. The Ti-Cu alloys were annealing treated at different temperatures (740 ℃, 830 ℃ and 910 ℃) in order to obtain three typical microstructures, α-Ti + Ti2Cu, α-Ti + transformed β-Ti, and transformed β-Ti. Mechanical, antibacterial and biocorrosion properties of Ti-Cu alloys with different microstructures were well analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile test, electrochemical test and antibacterial test. The results indicated that the Ti-Cu alloys with microstructure of α-Ti + Ti2Cu showed the best ductility compared with other Ti-Cu alloys with microstructures of α-Ti + transformed β-Ti and complete transformed β-Ti, and meanwhile, increase of the Cu content significantly contributed to the decreased ductility due to the increasing amount of Ti2Cu, which brought both solid solution strengthening and precipitation strengthening. Finally, the Ti-5Cu alloy with microstructure of α-Ti + Ti2Cu exhibited excellent ductility, antibacterial property and corrosion resistance, providing a great potential in clinical application for dental implants.

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    Corrosion kinetics and patina evolution of galvanized steel in a simulated coastal-industrial atmosphere
    Chuang Qiao, Lianfeng Shen, Long Hao, Xin Mu, Junhua Dong, Wei Ke, Jing Liu, Bo Liu
    J. Mater. Sci. Technol.. 2019, 35 (10): 2345-2356.   DOI: 10.1016/j.jmst.2019.05.039

    The corrosion kinetics and patina (corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn5(OH)6(CO3)2 and Zn4(OH)6SO4 are identified as the main stable composition and exhibit an increasing relative amount; while Zn12(OH)15Cl3(SO4)3 cannot stably exist and diminish in the patina layer as the corrosion develops.

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    Effect of partial replacement of carbon by nitrogen on intergranular corrosion behavior of high nitrogen martensitic stainless steels
    Wei-Chao Jiao, Hua-Bing Li, Jing Dai, Hao Feng, Zhou-Hua Jiang, Tao Zhang, Da-Ke Xu, Hong-Chun Zhu, Shu-Cai Zhang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2357-2364.   DOI: 10.1016/j.jmst.2019.06.004

    The microstructure evolution and intergranular corrosion (IGC) behavior of high nitrogen martensitic stainless steels (MSSs) by partial replacing C by N were investigated by using microscopy, X-ray diffraction, nitric acid tests and double-loop electrochemical potentiokinetic reactivation (DL-EPR) tests. The results show that the partial replacement of C by N first reduces and then increases the size and content of precipitates in high nitrogen MSSs, and converts the dominant precipitates from M23C6 to M2N, furthermore first improves and then deteriorates the IGC resistance. The high nitrogen MSS containing medium C and N contents provides good combination of mechanical properties and IGC resistance.

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    Development of extruded Mg-6Er-3Y-1.5Zn-0.4Mn (wt.%) alloy with high strength at elevated temperature
    Mingquan Zhang, Yan Feng, Jinghuai Zhang, Shujuan Liu, Qiang Yang, Zhuang Liu, Rongguang Li, Jian Meng, Ruizhi Wu
    J. Mater. Sci. Technol.. 2019, 35 (10): 2365-2374.   DOI: 10.1016/j.jmst.2019.05.053

    A new Mg-6Er-3Y-1.5Zn-0.4 Mn (wt.%) alloy with high strength at high temperature was designed and extruded at 350 °C. The as-extruded alloy exhibits ultimate tensile strength of 301 MPa, yield strength (along ED) of 274 MPa and thermal conductivity of 73 W/m·K at 300 °C. Such outstanding high-temperature strength is mainly attributed to the formation of nano-spaced solute-segregated basal plane stacking faults (SFs) with a large aspect ratio throughout the entire Mg matrix, fine dynamically recrystallized (DRXed) grains of 1-2 μm and strongly textured un-DRXed grains with numerous sub-structures. Microstructural examination unveils that long period stacking ordered (LPSO) phases are formed in Mg matrix of the as-cast alloy when rational design of alloy composition was employed, i.e. (Er + Y): Zn = 3: 1 and Er: Y = 1: 1 (at.%). It is worth mentioning that it is the first report regarding the formation of nano-spaced basal plane SFs throughout both DRXed and un-DRXed grains in as-extruded alloy with well-designed compositions and processing parameters. The results provide new opportunities to the development of deformed Mg alloys with satisfactory mechanical performance for high-temperature services.

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    Kinetic role of Cu content in reaction process, behavior and their relationship among Cu-Zr-C system
    Qiaodan Hu, Xianrui Zhao, Siyu Sun, Hua Zheng, Sheng Cao, Jianguo Li, Mengxian Zhang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2375-2382.   DOI: 10.1016/j.jmst.2019.05.034

    The influence of Cu content on the reaction process, reaction behavior and obtained products in the Cu-Zr-C system, as well as their relationships, were investigated. The results showed that ZrC was synthesized through the diffusion and dissolution of C into a Cu-Zr liquid. Increasing the Cu content enhanced the amount of Cu-Zr liquid formed at the early stage but decreased the amount of C atoms dissolving into the melt at unit time. Consequently, the ignition time initially decreased and then increased. Conversely, with an increased Cu content, the energy required for igniting the neighboring unreacted powders increased, while the heat released by the reaction and the dwell time of the compact at high temperatures decreased. These effects then resulted in the reduction of combustion wave velocity, combustion temperature and ZrC particle size. Furthermore, the synthesis of ZrC is a multistage process, which provides a nonuniform distributed ZrC particle size. The sub-μm ZrC particle reinforced Cu matrix composite was fabricated by adding a ZrC-Cu master alloy prepared through a self-propagating high-temperature synthesis reaction into liquid Cu.

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    Quantitative effects of phase transition on solute partition coefficient, inclusion precipitation, and microsegregation for high-sulfur steel solidification
    Lintao Gui, Mujun Long, Shixin Wu, Hua Zheng, Zhihua Dong, Jianguo Li, Dengfu Chen, Yunwei Huang, Yunwei Huang, Huamei Duan, Levente Vitos
    J. Mater. Sci. Technol.. 2019, 35 (10): 2383-2395.   DOI: 10.1016/j.jmst.2019.05.058

    Segregation and inclusion precipitation are the common behaviours of steel solidification, which are resulted from the redistribution and diffusion of the solute elements at the solid-liquid interface. The effect of the phase transition of high-sulfur free-cutting steel is quantified in the present work for the solute partition coefficient (ki), inclusion precipitation, and microsegregation by establishing a coupling model of microsegregation and inclusion precipitation, wherein the quantified dependencies of ki in terms of temperature, phase and carbon (C) content were applied. Results showed that the solidification temperature range and phase transition of high-sulfur steel that under different solidification paths and C contents were quite different, leading to differences in ki and eventually in microsegregation. kC, kP, and kS were mainly affected by phase composition and kSi was primarily by temperature, while kMn depended on both phase composition and temperature during solidification. Increasing the C content within the interval 0.07-0.48 wt%, the ‘proportion of the δ phase maintained temperature region during solidification’ (Pδ), kPave and kSave (kiave, the average value of the ki across the whole stages of solidification) decreased monotonically, whereas kCave increased linearly. The peritectic reaction impacted on the phase composition and ki, leading to the change in microsegregation. Such effect of the peritectic reaction was more significant at the last stage of solidification. When the Pδ was between 75% and 100% (corresponding to 0.07-0.16 wt% C), the solidification path resulted in a greater effect on the microsegregation of solutes C, P, and S because of the peritectic reaction. The microsegregation of solutes Mn and S were comprehensively influenced by kMn, kS and MnS precipitation as well. The studies would help reveal the solute redistribution at the solid-liquid interface, and improve the segregation of high-sulfur steel by controlling the solidification and precipitation in practice.

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    In situ fabrication of Na3V2(PO4)3 quantum dots in hard carbon nanosheets by using lignocelluloses for sodium ion batteries
    Qihao Zhang, Xudong Zhang, Wen He, Guogang Xu, Manman Ren, Jinhua Liu, Xuena Yang, Feng Wang
    J. Mater. Sci. Technol.. 2019, 35 (10): 2396-2403.   DOI: 10.1016/j.jmst.2019.06.002

    The rational assembly of quantum dots on two-dimensional (2D) carbonaceous materials is very promising to produce materials, but remains a challenge. Here, we develop an assembly strategy of growing Na3V2(PO4)3 quantum dots with superlattice structure (NVP-QDs-SL) for obtaining precise control of the size, distribution and crystallinity. The multifunctional lignocelluloses (LCs) used as a hard carbon source induce heterogeneous nucleation and confined growth of NVP-QDs-SL, leading to the uniform distribution of NVP-QDs-SL in H/S-doped hard carbon ultra-thin nanosheets (HCS). Detailed electrochemical analysis results from sodium-ion batteries of NVP-QDs-SL show that NVP-QDs-SL could trap the electrons inside HCS, significantly enhancing Na ion storage and transfer kinetics. Compared to the common Na3V2(PO4)3 nanoparticle cathode, the NVP-QDs-SL/HCS cathode exhibits a high reversible capacity of 149.2 mA h g-1 at a 0.1 C rate, which is far beyond the theoretical capacity of Na3V2(PO4)3 (117.6 mA h g-1). At the ultrahigh current rate of 100 C, this cathode still remains a high discharge capacity of 40 mA h g-1. Even after cycling at 20 C over 3000 cycles, an ultrahigh coulombic efficiency close to 100% is still obtained, highlighting its excellent long cycling life, remarkable rate performance and energy density.

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    Porous high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)B2: A novel strategy towards making ultrahigh temperature ceramics thermal insulating
    Heng Chen, Huimin Xiang, Fu-Zhi Dai, Jiachen Liu, Yanchun Zhou
    J. Mater. Sci. Technol.. 2019, 35 (10): 2404-2408.   DOI: 10.1016/j.jmst.2019.05.059
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