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CN 21-1315/TG
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 Microstructure and Fracture Behavior of 316L Austenitic Stainless Steel Produced by Selective Laser Melting
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 01 February 2020, Volume 38 Issue 0 Previous Issue    Next Issue
Letter
 Select Optimization of <001> grain gene based on texture hereditary behavior of magnetic materials Mengcheng Zhou, Xinfang Zhang J. Mater. Sci. Technol.. 2020, 38 (0): 1-6.   DOI: 10.1016/j.jmst.2019.07.045 Since the intrinsic properties of materials are determined by the properties and arrangement of atoms, including crystal structure and defects, there is a strong analogy between material genes and biological genes. Therefore, improving the performance of materials by optimizing their genes is a new idea of material upgrading. The <001> orientation texture is closely related to the magnetic properties of soft magnetic materials. We designed and experimentally demonstrated a gene optimization in an important soft magnetic material by electric current. The reduction of grain boundary hopping energy barrier caused by the distribution of electromagnetic field promoted <001> orientation grain nucleation and growth, which directly improved the initial <001> orientation grain gene, and the inheritance of <001> orientation texture was used to control the formation of recrystallization texture. Therefore, it is possible to utilize the gene optimization technique in many materials upgrading such as metal materials and biological materials according to the differences in electromagnetic properties of microstructures.
Research Article
 Select Investigation of solar-induced photoelectrochemical water splitting and photocatalytic dye removal activities of camphor sulfonic acid doped polyaniline -WO3- MWCNT ternary nanocomposite Mir Ghasem Hosseini, Pariya Yardani Sefidi, Ahmet Musap Mert, Solen Kinayyigit J. Mater. Sci. Technol.. 2020, 38 (0): 7-18.   DOI: 10.1016/j.jmst.2019.08.020 The camphor sulfonic acid doped polyaniline-WO3-multiwall carbon nanotube (CSA PANI-WO3-CNT) ternary nanocomposite was synthesized during in-situ oxidative polymerization and characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), and Energy-dispersive X-ray spectroscopy (EDS). The application of CSA PANI-WO3-CNT ternary nanocomposite was investigated as the photocatalyst in the degradation of methylene blue dye (MB) and as the noble metal-free photoanode in photoelectrochemical water splitting under solar light irradiation. The degradation percentage of MB dye after 60 min illumination by CSA PANI-WO3-CNT ternary nanocomposite reached 91.40% which was higher than that of pure WO3 (43.45%), pure CSA PANI (48.4%) and CSA PANI-WO3 binary nanocomposite (85.15%). The photocurrent density of indium tin oxide (ITO)/CSA PANI-WO3-CNT photoanode obtained 0.81 mA/cm2 at 1.23 V vs. reversible hydrogen electrode under illumination which was 1.27, 2.13, and 4.26 times higher than that of the ITO/CSA PANI-WO3 (0.64 mA/cm2), ITO/pure CSA PANI (0.38 mA/cm2), and ITO/pure WO3 (0.19 mA/cm2). Also, the applied bias photon-to-current efficiency (ABPE) of ITO/CSA PANI-WO3-CNT was obtained 0.11% which showed two-fold, four-fold, and five-fold enhancements compared to the ITO/CSA PANI-WO3, ITO/CSA PANI, and ITO/WO3, respectively. The electrochemical impedance spectroscopy, as well as the Mott-Schottky results, confirmed the better photoelectrocatalytic activity of ITO/CSA PANI-WO3-CNT in comparison with ITO/WO3, ITO/CSA PANI, and ITO/CSA PANI-WO3. The observed improvement in the photocatalytic and photoelectrocatalytic performances of WO3 in the presence of CSA PANI is due to the formation of type -II heterojunction between WO3 and CSA PANI which allows the separation of charge carriers easier and faster. On the other hand, MWCNT addition to the CSA PANI-WO3 nanocomposite provided the conducting substrate for efficient interfacial charge separation as well as transferring.
 Select Microstructure evolution, Cu segregation and tensile properties of CoCrFeNiCu high entropy alloy during directional solidification Huiting Zheng, Ruirun Chen, Gang Qin, Xinzhong Li, Yanqing Su, Hongsheng Ding, Jingjie Guo, Hengzhi Fu J. Mater. Sci. Technol.. 2020, 38 (0): 19-27.   DOI: 10.1016/j.jmst.2019.08.019 CoCrFeNiCu (equiatomic ratio) samples (ø 8 mm) were directionally solidified at different velocities (10, 30, 60 and 100 μm/s) to investigate the relationship between solidification velocity and microstructure formation, Cu micro-segregation as well as tensile properties. The results indicate that the morphology of the solid-liquid (S-L) interface evolves from convex to planar and then to concave with the increase of solidification velocity. Meanwhile, the primary and the secondary dendritic arm spacings decrease from 100 μm to 10 μm and from 20 μm to 5 μm, respectively. They are mainly influenced by the axial heat transfer and grain competition growth. During directional solidification, element Cu is repelled from the FCC phase and accumulates in the liquid owe to its positive mixing enthalpy with other elements. Tensile testing results show that the ultimate tensile strength (UTS) gradually increases from 400 MPa to 450 MPa, and the strain of the specimen prepared at the velocity of 60 μm/s is higher than those of others. The fracture mode of all specimens is the mixed fracture containing both ductile fracture and brittle fracture, in which ductile fracture plays a fundamental role. In addition, the brittle fracture is induced by Cu segregation. The improvement of UTS is resulted from columnar grain boundary strengthening.
 Select Low-cycle fatigue life prediction of a polycrystalline nickel-base superalloy using crystal plasticity modelling approach Guang-Jian Yuan, Xian-Cheng Zhang, Bo Chen, Shan-Tung Tu, Cheng-Cheng Zhang J. Mater. Sci. Technol.. 2020, 38 (0): 28-38.   DOI: 10.1016/j.jmst.2019.05.072 A crystal plasticity model is developed to predict the cyclic plasticity during the low-cycle fatigue of GH4169 superalloy. Accumulated plastic slip and energy dissipation as fatigue indicator parameters (FIPs) are used to predict fatigue crack initiation and the fatigue life until failure. Results show that fatigue damage is most likely to initiate at triple points and grain boundaries where severe plastic slip and energy dissipation are present. The predicted fatigue life until failure is within the scatter band of factor 2 when compared with experimental data for the total strain amplitudes ranging from 0.8% to 2.4%. Microscopically, the adjacent grain arrangements and their interactions account for the stress concentration. In addition, different sets of grain orientations with the same total grain numbers of 150 were generated using the present model. Results show that different sets have significant influence on the distribution of stresses between each individual grain at the meso-scale, although little effect is found on the macroscopic length-scale.
 Select Age hardening responses of as-extruded Mg-2.5Sn-1.5Ca alloys with a wide range of Al concentration Qiuyan Huang, Yang Liu, Aiyue Zhang, Haoxin Jiang, Hucheng Pan, Xiaohui Feng, Changlin Yang, Tianjiao Luo, Yingju Li, Yuansheng Yang J. Mater. Sci. Technol.. 2020, 38 (0): 39-46.   DOI: 10.1016/j.jmst.2019.06.025 This article aims to explore the age hardening responses of both as-extruded and as-aged Mg-2.5Sn-1.5Ca-xAl alloys (x = 2.0, 4.0 and 9.0 wt%, termed TXA322, TXA324 and TXA329, respectively) through microstructural and mechanical characterization. Results indicate that grain size of as-extruded TXA322, TXA324 and TXA329 alloys were ～ 16 μm, ～ 10 μm and ～ 12 μm, respectively. A number of and dislocations were observed in all the as-extruded samples. Guinier - Preston (GP) zones were evidently identified in TXA322 alloy, while only a small number of Mg17Al12 phases existed in both TXA324 and TXA329 alloys. An aging treatment facilitated the precipitation of a high number density of GP zones within the matrix of TXA322 alloy. In contrast, no obvious nano-precipitates were in as-aged TXA324 alloy. Numerous nano-Mg17Al12 phases were formed through a following aging treatment in TXA329 alloy. In terms of mechanical properties, it is apparent that an increment in ultimate tensile strength of ～ 46 MPa and ～ 40 MPa was yielded in peak-aged TXA322 and TXA329 alloys, while no obvious variations in UTS were present in peak-aged TXA324 alloy, in comparison with the as-extruded counterparts.
 Select Effects of external field treatment on the electrochemical behaviors and discharge performance of AZ80 anodes for Mg-air batteries Xingrui Chen, Shaochen Ning, Qichi Le, Henan Wang, Qi Zou, Ruizhen Guo, Jian Hou, Yonghui Jia, Andrej Atrens, Fuxiao Yu J. Mater. Sci. Technol.. 2020, 38 (0): 47-55.   DOI: 10.1016/j.jmst.2019.07.043 In this work, the effects of external field treatment on electrochemical behaviors and discharge performance of as-cast Mg-8%Al-0.5%Zn (wt%) anodes for Mg-air batteries are systematically investigated in 3.5 wt% NaCl solution. The external field treatment particularly the variable-frequency ultrasonic field can dramatically refine the α-Mg grains and β phases. The grain size decreases from 1594.8 ± 43 μm (untreated billet) to 140.6 ± 15 μm after variable-frequency ultrasonic field treatment. The values of open circuit potential, electrochemical activity and corrosion resistance of Mg-8%Al-0.5%Zn anode are improved with external field treatment, which should be attributed to refined grains and dispersive β phase. The external field treatment especially the variable-frequency ultrasonic field improves stability and the value of cell voltage, and enhances the discharge performance of the Mg-8%Al-0.5%Zn anode. The variable-frequency ultrasonic field treated anode has the best discharge capacity and anodic efficiency at current density of 45 mA cm-2, with the values of 1417 mA h g-1 and 63.3%, respectively. The ultrasonic field vibration changes the dissolution behavior of α-Mg matrix during the discharge process, showing the oriented surface morphologies.
 Select Improved formaldehyde gas sensing properties of well-controlled Au nanoparticle-decorated In2O3 nanofibers integrated on low power MEMS platform Dongha Im, Donghyun Kim, Dasol Jeong, Woon Ik Park, Myoungpyo Chun, Joon-Shik Park, Hyunjung Kim, Hyunsung Jung J. Mater. Sci. Technol.. 2020, 38 (0): 56-63.   DOI: 10.1016/j.jmst.2019.09.002 Approaches for the fabrication of a low power-operable formaldehyde (HCHO) gas sensor with high sensitivity and selectivity were performed by the utilization of an effective micro-structured platform with a micro-heater to reach high temperature with low heating power as well as by the integration of indium oxide (In2O3) nanofibers decorated with well-dispersed Au nanoparticles as a sensing material. Homogeneous In2O3 nanofibers with the large specific surface area were prepared by the electrospinning following by calcination process. Au nanoparticles with the well-controlled size as a catalyst were synthesized on the surface of In2O3 nanofibers. The Au-decorated In2O3 nanofibers were reliably integrated as sensing materials on the bridge-type micro-platform including micro-heaters and micro-electrodes. The micro-platform designed to maintain high temperature with low power consumption was fabricated by a microelectromechanical system (MEMS) technique. The micro-platform gas sensor consisting with Au-In2O3 nanofibers were fabricated effectively to detect HCHO gases with high sensitivity and selectivity. The HCHO gas sensing behaviors were schematically studied as a function of the gas concentration, the size of the adsorbed Au nanoparticles, the applied power to raise the temperature of a sensing part and the kind of target gases.
 Select Effect of phase-separated patterns on the formation of core-shell structure Yinli Peng, Nan Wang J. Mater. Sci. Technol.. 2020, 38 (0): 64-72.   DOI: 10.1016/j.jmst.2019.07.041 Revealing the mechanisms of self-organized core-shell (C-S) structure in immiscible systems has drawn considerable attentions, however, the further and fundamental understanding from the point of view of phase-separated pattern remains extremely rare. In this work, by realizing two phase-separated patterns in transparent immiscible system, namely nucleation-growth and spinodal decomposition, their effects on radius of minority-phase droplet (MPD) were examined, and subsequently the effect on C-S structure was further determined. It was found that compared with MPDs produced via nucleation-growth, the MPDs via spinodal decomposition are much larger and easier to form a C-S structure. This is mainly because the larger MPDs can migrate faster and are earlier to reach the sample’s center. In addition, two pathways of core formation were observed during the formation of C-S structure: one evolves from a ring-like structure in the phase separation of spinodal decomposition; the other derives from the collision of numerous MPD at sample’s center. Such a difference is ascribed to the combination of different growth kinetics and the volume fractions of MPD. These findings might provide an in-depth insight into the C-S structure formation in immiscible systems.
 Select Rejuvenated metallic glass strips produced via twin-roll casting Long Zhang, Yi Wu, Shidong Feng, Wen Li, Hongwei Zhang, Huameng Fu, Hong Li, Zhengwang Zhu, Haifeng Zhang J. Mater. Sci. Technol.. 2020, 38 (0): 73-79.   DOI: 10.1016/j.jmst.2019.08.022 The energy state and atomic level structure of metallic glasses (MGs) are very sensitive to their cooling rates, and a lower cooling rate generally causes a lower energy and more relaxed state of MGs. In this work, the Zr41.2Ti13.8Cu12.5Ni10Be22.5 (Vit. 1) ribbons with a thickness of 40 μm and 110 μm and the strips with a thickness of 320 μm and 490 μm were produced by single-roll melt spinning and twin-roll casting, respectively. The increase in thickness of either ribbons or strips results in a lower energy state with a smaller relaxation enthalpy, a lower content of free volume, and a higher hardness. Although the cooling rate of the twin-roll produced 320 μm-thick strip is almost one magnitude lower than that of the single-roll produced 110 μm-thick ribbon, the former, however, possesses a rejuvenated energy state as compared to the latter. Molecular dynamics simulations reveal that the squeezing force during twin-roll casting affects the evolution of connection types of clusters, and the 2-atom and 4-atom connections are prone to be retained, which results in a higher energy state of MGs. Such a rejuvenation process during twin-roll casting can overwhelm the relaxation process caused by the lower cooling rate. Therefore, twin-roll casting is not only a method being capable for producing strips with a large thickness, but also prone to obtain a high energy state of the MG strip.
Letter
 Select Effect of reaction routes on the porosity and permeability of porous high entropy (Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 for transpiration cooling Heng Chen, Zifan Zhao, Huimin Xiang, Fu-Zhi Dai, Jie Zhang, Shaogang Wang, Jiachen Liu, Yanchun Zhou J. Mater. Sci. Technol.. 2020, 38 (0): 80-85.   DOI: 10.1016/j.jmst.2019.09.006 Transpiration cooling technique is a reusable and high-efficiency thermal protection system (TPS), which is potential to improve the reusability and security of re-entry space vehicle. Relatively low density, high permeability and high porosity are general requirements for porous media of transpiration cooling systems. In this work, a new porous high entropy metal hexaboride (Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 is designed and prepared by the in-situ reaction/partial sintering method. Two reaction routes are designed to synthesize (Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6, including boron thermal reduction and borocarbon thermal reduction. The as-prepared porous HE (Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 ceramics possess homogeneous microstructure and exhibit low density, high porosity, high compressive strength and high permeability. The combination of these properties makes porous HE (Y0.2Yb0.2Sm0.2Nd0.2Eu0.2)B6 promising as a candidate porous media for various transpiration cooling applications.
Research Article
 Select Fabrication of textured Ti2AlC lamellar composites with improved mechanical properties Xi Xie, Rui Yang, Yuyou Cui, Qing Jia, Chunguang Bai J. Mater. Sci. Technol.. 2020, 38 (0): 86-92.   DOI: 10.1016/j.jmst.2019.05.070 Textured Ti2AlC lamellar composites have been successfully fabricated by a new method in the present work. The composites exhibit high compressive strength of ca 2 GPa, fracture toughness of 8.5 MPa m1/2 (//c-axis), flexural strength of 735 MPa (//c-axis) and high hardness of 7.9 GPa (//c-axis). The strengthening mechanisms were discussed. The sintering and densification process was investigated and crystal orientation and microstructure were studied by electron backscattered diffraction techniques. The synthesis temperature is reduced to 1200 °C by using high surface-to-volume ratio Ti2AlC nano flakes. The Lotgering orientation factor of Ti2AlC and Ti3AlC2 {00l} planes in the textured top surface reaches 0.74 and 0.49, respectively. This new route may shed light on resolving the difficulties encountered in large scale fabrication of textured MAX phases.
Invited Review
 Select Visible-light responsive organic nano-heterostructured photocatalysts for environmental remediation and H2 generation Yingzhi Chen, Dongjian Jiang, Zhengqi Gong, Qinglin Li, Ranran Shi, Zexi Yang, Ziyi Lei, Jingyuan Li, Lu-Ning Wang J. Mater. Sci. Technol.. 2020, 38 (0): 93-106.   DOI: 10.1016/j.jmst.2019.09.003 The ease of molecular design and functionalization make organic semiconductors (OSCs) unit the electronic, chemical and mechanical benefits with a material structure. The easily tunable optoelectronic properties of OSCs also make it promising building blocks and thereby provide more possibilities in photocatalytic applications. So far, organic nanostructures have gained great impetus and found wide applications in photocatalytic organic synthesis, remediation of water and air, as well as water splitting into hydrogen. But they still suffer from low charge separation and sunlight absorption efficiencies. Accordingly, many strategies have been explored to address these issues, and one of the most effective solutions is to develop nano-heterostructures. To give an impulse for the developments of this field, this review attempts to make a systematic introduction on the recent progress over the rational design and fabrication of organic nano-heterostructured photocatalysts, including the types of organic semiconductor/semiconductor (OSC/SC), organic semiconductor/metal (OSC/M), organic semiconductor/carbon (OSC/C), and OSC-based multinary nano-heterostructures. The emphasis is placed on the structure/property relationships, and their photocatalytic purposes in environmental and energy fields. At last, future challenges and perspectives for the ongoing development of OSC materials and their use in high-quality optoelectronic devices are also covered.
Research Article
 Select Excellent reusability of FeBC amorphous ribbons induced by progressive formation of through-pore structure during acid orange 7 degradation Miao Fang, Wang Qianqian, Zeng Qiaoshi, Hou Long, Liang Tao, Cui Zhiqiang, Shen Baolong J. Mater. Sci. Technol.. 2020, 38 (0): 107-118.   DOI: 10.1016/j.jmst.2019.07.050 The high-efficient degrading ability of FeBC amorphous ribbons toward acid orange 7 (AO7) via redox reactions is reported and compared with that of FePC amorphous ribbons. The time required for degrading 50% of AO7 using FeBC amorphous ribbons is only 1/3 of that using FePC amorphous ribbons. In the FeBC amorphous matrix, galvanic cell structures are formed between the Fe-B and Fe-C bonds because of the large difference in their bonding strengths, which contributes to the low reaction activation energy and the high degrading efficiency of FeBC amorphous ribbons. The extremely long service life of FeBC amorphous ribbons comes from the progressive formation of 3D porous nanosheet networks that allow more efficient mass transport and a larger specific surface area. The FeBC amorphous ribbons show a satisfying degrading ability in not only acidic but also neutral and weak alkaline AO7 solutions. This work provides an effective and environmental- friendly material for degrading azo dyes.
 Select Facile fabrication of core-shell Ni3Se2/Ni nanofoams composites for lithium ion battery anodes Wang Zhongren, Gao Quanbin, Lv Peng, Li Xiuwan, Wang Xinghui, Qu Baihua J. Mater. Sci. Technol.. 2020, 38 (0): 119-124.   DOI: 10.1016/j.jmst.2019.08.021 Due to the highly porous structure, large specific surface area, and 3D interconnected metal conductive network, nanoporous metal foams have attracted a lot of attention in the field of energy conversion and storage, especially lithium-ion batteries, which are ideal for current collectors. In this work, we develop a facile approach to fabricate core-shell Ni3Se2/Ni nanofoams composites. The Ni3Se2/Ni composites make full use of both the advantages of metal conductive network and core-shell structure, resulting in a high capacity and superior rate performance. In addition, the composites can be directly converted into electrode by a simple mechanical compression, which is more convenient than traditional casting method. What’s more, this material and its structure can be extended to other devices in the field of energy conversion and storage.
 Select Effects of strain state and slip mode on the texture evolution of a near-α TA15 titanium alloy during hot deformation based on crystal plasticity method Zhao Jie, Lv Liangxing, Wang Kehuan, Liu Gang J. Mater. Sci. Technol.. 2020, 38 (0): 125-134.   DOI: 10.1016/j.jmst.2019.07.051 A thorough understanding of the texture evolution of near-α titanium alloys during the hot metal forming can help obtain an optimal crystallographic texture and material performance. The strain state has an obvious effect on the texture evolution of near-α titanium alloys during the hot metal forming. In this paper, the texture evolution of a near-α TA15 titanium alloy during the hot metal forming under different strain states were discussed based on the crystal plasticity finite element method. It is found that the basal and prismatic slip systems are regarded as the dominant slip modes due to the similar low critical resolved shear stress during the hot metal forming of the TA15 sheet rotating the lattice around the [10$\bar{1}$0] and 〈0001〉 axis, respectively. Once both of them cannot be activated, the pyramidal-2 slipping occurs rotating the lattice around the [10$\bar{1}$0] axis. The relationship between the texture evolution and strain state is established. All the (0001) orientations form a band perpendicular to the direction of the first principal strain. The width of the band along the direction of the second principal strain depends on the ratio of the compressive effect to the tensile effect of the second principal strain. This relationship can help control the crystallographic texture and mechanical properties of the titanium alloys component during the hot metal forming.
 Select On the nature of a peculiar initial yield behavior in metastable β titanium alloy Ti-5Al-5Mo-5V-3Cr-0.5Fe with different initial microstructures Fan Jiangkun, Zhang Zhixin, Gao Puyi, Yang Ruimeng, Li Huan, Tang Bin, Kou Hongchao, Zhang Yudong, Esling Claude, Li Jinshan J. Mater. Sci. Technol.. 2020, 38 (0): 135-147.   DOI: 10.1016/j.jmst.2019.07.053 The compressive yielding phenomenon of titanium alloys is not as focused and sufficiently ascertain as the tensile yielding phenomenon. In the present work, the peculiar compressive yielding behavior and the different dynamic responses of three different initial microstructures (single β, clavate α and lamellar α) were investigated in an attractive metastable β titanium alloy Ti-5553 using electron microscopes/crystallographic calculation/crystal plastic finite element simulation. Results reveal that the distinct compressive yielding behavior, steep peaks of sudden drop in the initial stage (very small true strain $\widetilde{0}$.03) of stress loading have appeared in the compression stress-strain curves except for the lamellar α initial microstructure. Dislocation slip is the essential mechanism of the initial yielding behavior. Interlaced multiple-slip bands formed in the single β initial microstructure during the warm deformation process. A small quantity of single slip bands was observed in the deformed clavate α initial microstructure. The abundant varied nano/ultrafine αs precipitates were nucleated dynamically and dispersedly in all the three deformed initial microstructures. The multiple-slip bands formation and substantial nanoscale αs result in the highest peak of flow stress for single β initial microstructure. The compressive slip bands are formed early in the elastic - plastic deformation stage. As the increasing strain, the sample showed a significant compressive bulge, or eventually forming a strong adiabatic shear band or crack. These results are expected to provide a reference for the study of deformation behavior and mechanical properties of metastable β titanium alloys.
 Select How does anodization time affect morphological and photocatalytic properties of iron oxide nanostructures? Lucas-Granados Bianca, Sánchez-Tovar Rita, M. Fernández-Domene Ramón, María Estívalis-Martínez José, García-Antón José J. Mater. Sci. Technol.. 2020, 38 (0): 159-169.   DOI: 10.1016/j.jmst.2019.07.046 Iron oxide nanostructures are promising materials to be used as photocatalysts in different photoelectrochemical applications. There are different techniques in order to synthesize these nanostructures, but one of the most inexpensive and simple method is electrochemical anodization. This method can lead to different nanostructures by controlling its parameters. Anodization time is one of the most critical parameters since it considerably affects the properties of the obtained nanostructures. In this work, different anodization times (5, 10, 15, 30 and 60 min) were studied. The resulting nanotubes were characterized by field emission scanning electron microscopy, Raman laser confocal microscopy, water splitting measurements, Mott-Schottky analysis and electrochemical impedance spectroscopy, in order to test their viability for being used as photocatalysts in photoelectrochemical applications. Results showed that the best photocurrent density values in water splitting tests (0.263 mA m-2) were achieved for the sample anodized for 10 min under hydrodynamic conditions.
 Select Solidification microstructure of Cr4Mo4V steel forged in the semi-solid state Liu Weifeng, Cao Yanfei, Guo Yifeng, Sun Mingyue, Xu Bin, Li Dianzhong J. Mater. Sci. Technol.. 2020, 38 (0): 170-182.   DOI: 10.1016/j.jmst.2019.07.049 Semi-solid forging of iron-based alloys during solidification has unique characteristics distinct from those of the classical hot forging. With the aim of acquiring precise knowledge concerning the microstructural evolution of bearing steel Cr4Mo4V in this process, a series of semi-solid forging experiments were carried out in which samples were wrapped in a designed pure iron sheath. The effects of forging temperature and forging reduction on the grain morphology and liquid flow behavior were investigated, respectively. By forging solidifying metal (FSM), bulky primary dendrites were broken and spheroidal grains with an average shape factor of 0.87 were obtained at 1360 °C. With the decreasing forging temperature to 1340 °C, the microstructural homogeneity can be improved. On the other hand, it shows that a higher forging reduction (50%) is essential for the spheroidization of grains and elimination of liquid segregation. Those microstructural characteristics are related to different motion mechanisms of solid and liquid phases at different forging temperatures. Additionally, the effect of semi-solid forging on the eutectic carbides was also investigated, and the results demonstrate that the higher diffusion capacity and less liquid segregation jointly lower the large eutectic carbides and consequently cause its uniform distribution during FSM.
 Select A controllable soft-templating approach to synthesize mesoporous carbon microspheres derived from d-xylose via hydrothermal method Su Jian, Fang Changqing, Yang Mannan, Cheng Youliang, Wang Zhen, Huang Zhigang, You Caiyin J. Mater. Sci. Technol.. 2020, 38 (0): 183-188.   DOI: 10.1016/j.jmst.2019.03.050 Highly dispersed carbon microspheres (CMSs) derived from D-xylose were successfully synthesized under hydrothermal conditions and followed by further carbonization, in which F127 was used as a soft template. As-synthesized products were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), flourier transform infrared spectroscopy (FT-IR), thermal gravimetric (TG) and X-ray diffraction (XRD). The results showed that the morphology and structure of the CMSs prominently depended on the stirring speed during hydrothermal reaction. The resultant CMSs principally had non-porous structure without stirring and had a very smooth surface. When the stirring speed increased to 200 rpm, the synthesized mesoporous carbon microspheres at 220 °C for 24 h (CMSs-5) had a uniform size distribution of 1-1.4 μm and a specific surface area of 452 m2/g. Nevertheless, with further increasing to 400 rpm, as-fabricated carbon products were mostly amorphous with a low degree of sphericity. Results demonstrated that the diameter of the products decreased with the increase of stirring speed. Furthermore, the sphericity product yield of CMSs reduced with the increase of stirring speed. XRD result showed that all the obtained samples contained partial graphite phase. In addition, a formation mechanism was proposed that involved polymerization product as the precursors for microsphere formation. The controllable and green strategy may provide a great convenience to study properties and applications of carbon microspheres.
 Select Static and cyclic oxidation of Nb-Cr-V-W-Ta high entropy alloy in air from 600 to 1400 °C Varma S.K., Sanchez Francelia, Moncayo Sabastian, Ramana C.V. J. Mater. Sci. Technol.. 2020, 38 (0): 189-196.   DOI: 10.1016/j.jmst.2019.09.005 An oxidation resistance study has been made on Nb-Cr-V-W-Ta high entropy alloy in a range of temperature from 600 to 1400 °C in air. Static oxidation study has been performed for either (a) 12 or 24 h of heating time or (b) 3 or 10 °C/min heating rates to the desired oxidation temperature. Cyclic oxidation study conducted for three and a half days has been conducted at 600, 700, and 800 °C using 12 h of heating cycles. The alloy can withstand the cyclic oxidation process with only a reasonable loss of alloy. The identification of oxides indicates crystals of W and Ta oxides in cylindrical form while Nb and Cr oxides show a nodular or granular morphology at both 1000 and 1200 °C while and additional of oxide of V in whisker forms at 1200 °C.
 Select Pesticide-induced photoluminescence quenching of ultra-small Eu3+-activated phosphate and vanadate nanoparticles Periša Jovana, Antić Željka, Ma Chong-Geng, Papan Jelena, Jovanović Dragana, D.Dramićanin Miroslav J. Mater. Sci. Technol.. 2020, 38 (0): 197-204.   DOI: 10.1016/j.jmst.2019.09.004 The aim of this research was to investigate the luminescent behavior of ultra-small Eu3+-activated phosphate and vanadate nanoparticles in the presence of pesticides. Nanoparticles have an average diameter of approximately 2 nm with a narrow size distribution. The monazite crystal structure of phosphate-based particles (space group P121/n1) and single tetragonal zircon-type structure of vanadate-based particles (space group of I41/amd) have been confirmed using X-ray diffraction measurements. All synthesized Eu3+-activated colloidal nanoparticles show sharp emission peaks in the red spectral region. Photoluminescence measurements revealed emission quenching upon addition of millimolar concentrations of following pesticides: 4-Chloro-2-methyl-phenoxyacetic acid (MCPA), 2,4-Dichlorophenoxyacetic acid (2,4-D) and N-(phosphonomethyl)glycine (Glyphosate). In both phosphate and vanadate-based colloidal nanoparticles luminescence quenching is more evident in the presence of 2,4-D pesticide with the lowest limit of detection (0.7 μM) obtained for phosphate-based nanoparticles.
Invited Review
 Select Structural defects in MAX phases and their derivative MXenes: A look forward Zhang Hui, Hu Tao, Wang Xiaohui, Zhou Yanchun J. Mater. Sci. Technol.. 2020, 38 (0): 205-220.   DOI: 10.1016/j.jmst.2019.03.049 MAX phases and corresponding 2D derivative MXenes have attracted considerable interests due to not only their fascinating mechanical, physical and chemical properties but also their unique atomically laminated structures. As the most important way to tailor the materials properties, the structural defects in MAX phases and MXenes have been extensively investigated but lack of systematic survey although six reviews and two books in this field have been published. To make the defect-engineering based materials design and exploration more efficient and targeted, this paper provides a review of the recent progress on the nature of different-dimensional structural defects and their influence on the properties, in the hope of facilitating the conversion of established experiment and simulation results into practical guideline for optimizing defects in a broad range of demand-oriented materials development in the future. Also, unsolved issues on the structural defects of these scientifically and technologically important materials are also highlighted for the future study.
 Select Surface/interface engineering of noble-metals and transition metal-based compounds for electrocatalytic applications Zhang Mengmeng, Li Xiaopeng, Zhao Jun, Han Xiaopeng, Zhong Cheng, Hu Wenbin, Deng Yida J. Mater. Sci. Technol.. 2020, 38 (0): 221-236.   DOI: 10.1016/j.jmst.2019.07.040 Surface/interface engineering plays an important role in improving the performance and economizing the cost and usage of electrocatalysts. In recent years, substantial progress has been achieved in designing and developing highly active electrocatalysts with the deepening understanding of surface and interface enhanced mechanism. In this review, recent development about optimizing the surface and interfacial structure in promoting the electrocatalytic activity of noble-metals and transition metal compounds is presented and the chemical enhancements are also described in detail. The relationship between the surface/interface structures (both atomic and electronic configuration) and the electrochemical behaviors has been discussed. Finally, personal perspectives have been proposed, highlighting the challenges and opportunities for future development in tuning the surface/interface active sites of electrocatalysts. We believe that this timely review will be beneficial to the construction of highly active and durable electrode materials through optimizing surface atomic arrangement and interfacial interaction, which can largely promote the development of next-generation clean energy conversion technologies.
Research Article
 Select Direct patterning of reduced graphene oxide/graphene oxide memristive heterostructures by electron-beam irradiation O. Kapitanova Olesya, V. Emelin Evgeny, G. Dorofeev Sergey, V. Evdokimov Pavel, N. Panin Gennady, Lee Youngmin, Lee Sejoon J. Mater. Sci. Technol.. 2020, 38 (0): 237-243.   DOI: 10.1016/j.jmst.2019.07.042 Memristive heterostructures, composed of reduced graphene oxide with different degree of reduction, were demonstrated through a simple method of ‘direct electron-beam writing’ on graphene oxide. Irradiation with an electron beam at various doses and accelerating voltages made it possible to define high- and low-conductivity graphene-oxide areas. The electron beam-reduced graphene oxide/graphene oxide heterostructure clearly exhibited a nonlinear behavior and a well-controlled resistive switching characteristic at a low operating-voltage range (< 1 V). The proposed memristive heterostructures are promising for highly-efficient digital storage and information process as well as for analogous neuromorphic computations.
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