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.

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      15 June 2020, Volume 47 Issue 0 Previous Issue    Next Issue
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    Research Article
    Cellular automaton modeling of austenite formation from ferrite plus pearlite microstructures during intercritical annealing of a C-Mn steel
    Chunni Jia, Chengwu Zheng, Dianzhong Li
    J. Mater. Sci. Technol., 2020, 47 (0): 1-9.  DOI: 10.1016/j.jmst.2020.02.002
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    A mesoscopic cellular automaton model was developed to study the microstructure evolution and solute redistribution of austenization during intercritical annealing of a C-Mn steel. This model enables a depiction of three-stage kinetics of the transformation combined with the thermodynamic analysis: (1) the rapid austenite growth accompanied with pearlite degeneration until the pearlite dissolves completely; (2) the slower austenite growth into ferrite with a rate limiting factor of carbon diffusion in austenite; and (3) the slow austenite growth in control of the manganese diffusion until the final equilibrium reached for ferrite and austenite. The effect of the annealing temperature on the transformation kinetics and solute partition is also quantitatively rationalized using this model.

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    Microbiologically influenced corrosion of Cu by nitrate reducing marine bacterium Pseudomonas aeruginosa
    Yanan Pu, Wenwen Dou, Tingyue Gu, Shiya Tang, Xiaomei Han, Shougang Chen
    J. Mater. Sci. Technol., 2020, 47 (0): 10-19.  DOI: 10.1016/j.jmst.2020.02.008
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    The microbiologically influenced corrosion (MIC) mechanisms of copper by Pseudomonas aeruginosa as a typical strain of nitrate reducing bacteria (NRB) was investigated in this lab study. Cu was immersed in deoxygenated LB-NO3 seawater inoculated with P. aeruginosa and incubated for 2 weeks. Results showed that this NRB caused pitting and uniform corrosion. The maximum pit depths after 7 d and 14 d in 125 mL anaerobic vials with 50 mL broth were 5.1 μm and 9.1 μm, accompanied by specific weight losses of 1.3 mg/cm2 (7 d) and 1.7 mg/cm2 (14 d), respectively. Electrochemical measurements corroborated weight loss and pit depth data trends. Experimental results indicated that extracellular electron transfer for nitrate reduction was the main MIC mechanism and ammonia secreted by P. aeruginosa could also play a role in the overall Cu corrosion process.

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    Design and development of a high-performance Ni-based superalloy WSU 150 for additive manufacturing
    Praveen Sreeramagiri, Ajay Bhagavatam, Abhishek Ramakrishnan, Husam Alrehaili, Guru Prasad Dinda
    J. Mater. Sci. Technol., 2020, 47 (0): 20-28.  DOI: 10.1016/j.jmst.2020.01.041
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    This research proposes a design and development strategy of a new nickel-based superalloy for additive manufacturing. A new Ni-based superalloy has been developed by the application of the combinatorial alloy development technique coupled with CALPHAD based solidification modeling by effectively suppressing the precipitation kinetics. The suppression of precipitation during processing paved a way for prevention of cracks during deposition. The new alloy “WSU 150″ revealed excellent room temperature mechanical properties with a yield strength of 867 MPa, an ultimate tensile strength of 1188 MPa, and an elongation of 27.9% in the as-deposited condition. The mechanical properties of the heat-treated alloy were improved significantly to 1114 MPa yield strength, 1396 MPa ultimate tensile strength, and an elongation of 16.1%. Improvement in the mechanical properties is attributed to the additional precipitation and coarsening of γ' and carbides during heat-treatment. Microstructural investigation of the alloy revealed spherical γ' with a rippled size distribution from the center to the interdendritic region. The average size of the γ' particles in the as-deposited condition was found to be around 48 nm in the interdendritic region. Heat-treatment promoted the coarsening of γ' which is explained in the paper.

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    Highly efficient Ag-modified copper phyllosilicate nanotube: Preparation by co-ammonia evaporation hydrothermal method and application in the selective hydrogenation of carbonate
    Huabo Li, Yuanyuan Cui, Yixin Liu, Lu Zhang, Quan Zhang, Juhua Zhang, Wei-Lin Dai
    J. Mater. Sci. Technol., 2020, 47 (0): 29-37.  DOI: 10.1016/j.jmst.2020.02.020
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    Rapidly deactivation of Cu/SiO2 catalysts at high liquid hour space velocity (LHSV) has been an important obstacle for scale-up application. Herein, silver modified copper phyllosilicate nanotubes were fabricated by different strategies, and implemented to the selective hydrogenation of ethylene carbonate (EC) to methanol and ethylene glycol (EG) as alternative route for the indirect utilization of CO2. The CuPs Ag-copre catalyst synthesized by the co-ammonia evaporation hydrothermal process achieved 79% methanol and 99% EG yield within various ranges of EC LHSV, which was attributed to the balanced Cu+/Cu0 ratio and the enhanced H2 dissociation ability. Inlaid silver species over copper phyllosilicate promoted the interaction between the metal and the support, which substantially regulated the reducibility and dispersion of copper species, meanwhile, increased the stability for long-term running of the catalyst.

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    Effect of Ni content on high power laser ablation behavior of coatings sprayed by Ni covering graphite/SiO2 powders
    Wenzhi Li, Lihong Gao, Zhuang Ma, Yanbo Liu, Fuchi Wang, Jiawei Wang, Lijun Wang, Hezhang Li
    J. Mater. Sci. Technol., 2020, 47 (0): 38-44.  DOI: 10.1016/j.jmst.2019.11.036
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    Faced with the challenge of high energy ablation problems, especially for laser ablation, effective energy dissipation protective materials fabricate by efficient preparation method is a feasible solution. The Ni-graphite/SiO2 coatings with different Ni content were prepared by plasma spraying method with optimized plasma spraying parameters. All coatings are pure without oxidation and dense. Their ablation behaviors were investigated by high power continuous wave laser. The results indicate that the Ni-graphite/SiO2 coating with appropriate Ni content could realize the purpose of energy consumption by endothermal reaction of graphite/SiO2 and reflection improvement. High Ni content will block the occurrence of endothermal reaction of graphite/SiO2 and increase the heat diffusion to interior part of coating, which can make the ablation situation of coating more serious.

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    High-entropy (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3: A promising thermal/environmental barrier material for oxide/oxide composites
    Zifan Zhao, Heng Chen, Huimin Xiang, Fu-Zhi Dai, Xiaohui Wang, Wei Xu, Kuang Sun, Zhijian Peng, Yanchun Zhou
    J. Mater. Sci. Technol., 2020, 47 (0): 45-51.  DOI: 10.1016/j.jmst.2020.02.011
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    Yttrium aluminum perovskite (YAlO3) is a promising candidate material for environmental barrier coatings (EBCs) to protect Al2O3f/Al2O3 ceramic matrix composites (CMCs) from the corrosion of high-temperature water vapor in combustion environments. Nevertheless, the relatively high thermal conductivity is a notable drawback of YAlO3 for environmental barrier coating application. Herein, in order to make REAlO3 more thermal insulating, a novel high-entropy rare-earth aluminate ceramic (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 was designed and synthesized. The as-prepared (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 ceramic possesses close thermal expansion coefficient (9.02 × 10―6 /oC measured from room temperature to 1200 °C) to that of Al2O3. The thermal conductivity of (Y0.2Nd0.2Sm0.2Eu0.2Er0.2) AlO3 at room temperature is 4.1 W·m-1 K-1, which is almost one third of the value of YAlO3. Furthermore, to effectively prevent the penetration of water vapor from possible pores/cracks of coating layer, which are often observed in T/EBCs, a tri-layer EBC system REAlO3/RE3Al5O12/(Al2O3f/Al2O3 CMCs) is designed. Close thermal expansion coefficient to Al2O3 and low thermal conductivity of (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3, as well as the formation of dense garnet layer at (Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3/Al2O3 interface, indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al2O3f/Al2O3 CMCs.

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    In vitro and in vivo biodegradation and biocompatibility of an MMT/BSA composite coating upon magnesium alloy AZ31
    Jian Wang, Lanyue Cui, Yande Ren, Yuhong Zou, Jinlong Ma, Chengjian Wang, Zhongyin Zheng, Xiaobo Chen, Rongchang Zeng, Yufeng Zheng
    J. Mater. Sci. Technol., 2020, 47 (0): 52-67.  DOI: 10.1016/j.jmst.2020.02.006
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    The performance of biodegradable magnesium alloy requires special attention to rapid degradation and poor biocompatibility, which can cause the implant to fail. Here, a sodium montmorillonite (MMT)/bovine serum albumin (BSA) composite coating was prepared upon magnesium alloy AZ31 via hydrothermal synthesis, followed by dip coating. We evaluated the surface characterization and corrosion behavior in vitro, and the biocompatibility in vitro and in vivo. Biodegradation progress of the MMT-BSA coated Mg pieces was examined through hydrogen evolution, immersion tests, and electrochemical measurements in Hank’s solution. In vitro biocompatibility studies were evaluated via hemolysis tests, dynamic cruor time tests, platelet adhesion, MTT testing and live-dead stain of osteoblast cells (MC3T3-E1). It was found that the MMT-BSA coating had good corrosion resistance and a marked improvement in biocompatibility in comparison to bare Mg alloy AZ31. in vivo studies were carried out in rat model and the degradation was characterized by computed tomography scans. Results revealed that the MMT-BSA coated Mg alloy AZ31 implants maintained their structural integrity and slight degradation after 120 d of post-implantation. A 100% survival rate for the rats was observed with no obvious toxic damages on the organs and tissues. Additionally, we proposed a sound coating formation mechanism. Considering the good corrosion protection and biocompatibility, the MMT-BSA coated Mg alloy AZ31 is a promising candidate material for biomedical implants.

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    The influence of microtexture on the formation mechanism of nodules in Zircaloy-4 alloy tube
    Yingdong Zhang, Fusen Yuan, Fuzhou Han, Muhammad Ali, Wenbin Guo, Geping Li, Chengze Liu, Hengfei Gu
    J. Mater. Sci. Technol., 2020, 47 (0): 68-75.  DOI: 10.1016/j.jmst.2020.02.010
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    Corrosion resistance of Zircaloy-4 alloy tube in superheated steam at 673 K/10.3 MPa is anisotropic. A part of the surface undergoes uniform corrosion while the other suffers nodular corrosion. Narrow and wide nodules are observed after an exposure period of 3 and 30 days, respectively. A new matrix transformation method is established in order to study the formation mechanism of nodules in the cross-section (CS) of Zircaloy-4 alloy tube using the EBSD technique, while the CS perpendicular to axial direction (AD). The results reveal that the microtexture is a key factor behind the two types of corrosion. Furthermore, the oxide layers grow anisotropically over the corroded surface. A thick oxide layer forms over the nodular corrosion region on the grains with c-axis oriented in the range of 40° around tangential direction (TD), whereas a thin oxide layer over the uniform corrosion region is detected on the grains with c-axis oriented in the range of 68° around TD. In short, the anisotropic growth of oxide layer was caused by the change of microtexture of the Zr-4 alloy tube, and this anisotropic growth of oxide layer contributed to the nodules formation.

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    Effects of 405 stainless steel on crevice corrosion behavior of Alloy 690 in high-temperature pure water
    Fangqiang Ning, Jibo Tan, Xinqiang Wu
    J. Mater. Sci. Technol., 2020, 47 (0): 76-87.  DOI: 10.1016/j.jmst.2020.02.004
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    Effects of 405 stainless steel (405 SS) on crevice corrosion behavior of Alloy 690 in high-temperature pure water were investigated. Results revealed that the corrosion rate of Alloy 690 was low within the crevice. It was likely attributed to the fact that a Cr-rich inner oxide film and a Ni-rich layer beneath this oxide film formed upon Alloy 690, inhibiting the diffusion of oxygen towards the oxide/matrix interface. Moreover, the Fe2+ ions dissolved from 405 SS consumed most of oxygen, leading to less oxygen participating in the oxidation of Alloy 690. In addition, it was found that Fe concentration continuously decreased from the surface of the inner oxide film to the oxide/matrix interface of Alloy 690 within the crevice, which was probably due to the diffusion of Fe2+ ions dissolved from 405 SS into the inner oxide film.

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    Formation mechanism and evolution of surface coarse grains on a ZK60 Mg profile extruded by a porthole die
    Jianwei Tang, Liang Chen, Guoqun Zhao, Cunsheng Zhang, Xingrong Chu
    J. Mater. Sci. Technol., 2020, 47 (0): 88-102.  DOI: 10.1016/j.jmst.2019.11.037
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    Porthole die extrusion of Mg alloys was studied by means of experimental and numerical studies. Results indicated that an inhomogeneous microstructure formed on the cross-section of the extruded profile. On the profile surface, abnormal coarse grains with an orientation of <11-20> in parallel to ED (extrusion direction) appeared. In the profile center, the welding zone was composed of fine grains with an average size of 4.19 μm and an orientation of <10-10> in parallel to ED, while the matrix zone exhibited a bimodal grain structure. Disk-like, near-spherical and rod-like precipitates were observed, and the number density of those features was lower on the profile surface than that in the profile center. Then, the formation and evolution of coarse grains on the profile surface were investigated, which were found to depend on the competition between static recrystallization and grain growth. The stored deformation energy was the factor dominating the surface structure through effective regulation over nucleation of the precipitates and recrystallization. A profile with a low stored deformation energy suppressed formation of precipitates and consequently facilitated grain growth rather than recrystallization, resulting in the formation of abnormal coarse grains. Finally, the surface coarse grains contributed detrimentally to hardness, tensile properties, and wear performance of the bulk structure.

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    Direct writing of silver microfiber with precise control on patterning for robust and flexible ultrahigh-performance transparent conductor
    Tao Chen, Heping Li, Jing Li, Sanyuan Hu, Pin Ye, Youwei Yan
    J. Mater. Sci. Technol., 2020, 47 (0): 103-112.  DOI: 10.1016/j.jmst.2020.01.043
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    Ultrafine silver fiber is an alternative to commercial indium tin oxide (ITO) as a new-generation flexible transparent conductor that can be used in flexible electronics. However, its primary limitation is the unrepeatable optoelectronic properties due to the disordered distribution of silver fibers. In this work, we report the in-situ direct writing of the silver microfiber pattern with high conductivity and transparency to attain a flexible transparent conductor. The silver network is composed of silver microfibers, which can be artificially designed and regularly patterned under the precise control of the fiber position and shape; this is crucial for regulating its optoelectronic properties. Herein, a high-performance conductor is achieved in the silver network with high stability. This novel conductor has a sheet resistance of 2 Ω sq-1 at 90% transparency, which corresponds to a high Figure of merit σdcopt = 1742. The in-situ direct writing technique developed here is distinct from other fabrication methods because it requires no transfer steps, templates or heating. Further, this silver network is integrated into a light-printable rewritable device, and can be used as a wearable heater; this heater when driven by a 1.5 V battery attains a temperature of up to 55.6 ℃. Therefore, in-situ direct writing is expected to offer a new platform for facile, scalable, and ultralow-cost production of high-performance metal networks for flexible transparent conductors.

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    Construction of nickel cobalt sulfide nanosheet arrays on carbon cloth for performance-enhanced supercapacitor
    Tao Liu, Jiahao Liu, Liuyang Zhang, Bei Cheng, Jiaguo Yu
    J. Mater. Sci. Technol., 2020, 47 (0): 113-121.  DOI: 10.1016/j.jmst.2019.12.027
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    Materials featured with self-supported three-dimensional network, hierarchical pores and rich electrochemical active sites are considered as promising electrodes for pseudocapacitors. Herein, a novel strategy for the growth of nickel-cobalt bisulfide (NiCoS) nanosheets arrays on carbon cloth (CC) as supercapacitor electrodes is reported, involving deposition of two-dimensional metal-organic framework (MOF) precursors on the CC skeletons, conversion of MOF into nickel-cobalt layered double-hydroxide by ion exchange process and formation of NiCoS by a sulfidation treatment. The NiCoS nanosheets with rough surface and porous structures are uniformly anchored on the CC skeletons. The unique architecture endows the composite (NiCoS/CC) with abundant accessible active sites. Besides, robust electrical/mechanical joint between the nanosheets and the substrates is attained, leading to the improved electrochemical performance. Moreover, an asymmetric supercapacitor device is constructed by using NiCoS/CC and activated carbon as a positive electrode and a negative electrode, respectively. The optimized device exhibits a high specific capacitance, large energy density and long cycle life. The NiCoS/CC electrode with intriguing electrochemical properties and mechanical flexibility holds great prospect for next-generation wearable devices.

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    Carbide precipitation behavior and mechanical properties of micro-alloyed medium Mn steel
    Luhan Hao, Xiang Ji, Guangqian Zhang, Wei Zhao, Mingyue Sun, Yan Peng
    J. Mater. Sci. Technol., 2020, 47 (0): 122-130.  DOI: 10.1016/j.jmst.2019.12.024
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    The carbide precipitation behavior and mechanical properties of advanced high strength steel deformed at different temperatures are investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) equipped with an energy dispersing spectroscopy (EDS), and tensile tests. The medium Mn steel was subjected to controlled deformation up to 70% at 750 °C, 850 °C, 950 °C, and 1050 °C, and then quenched with water to room temperature, followed by intercritical annealing at 630 °C for 10 min. In comparison with the undeformed and quenched specimen, it can be concluded that acicular cementite precipitates during the quenching and cooling process, while granular NbC is the deformation induced precipitate and grows during the following annealing process. As the deformation temperature increases from 750 °C to 1050 °C, the product of strength and elongation increases at first and then decreases. The smallest average size of second phase particles (20 nm) and the best mechanical properties (32.5 GPa.%) can be obtained at the deformation temperature of 950 °C.

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    Effect of warm rolling process on microstructures and tensile properties of 10¬タノMn steel
    Bin Hu, Xin Tu, Haiwen Luo, Xinping Mao
    J. Mater. Sci. Technol., 2020, 47 (0): 131-141.  DOI: 10.1016/j.jmst.2019.12.026
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    The influence of warm rolling processes on the microstructures and tensile properties of 10 Mn steel was studied. Strength appeared to increase with the rolling temperature but strengthening mechanisms varied. The increase of warm rolling temperature from 250°C to 600°C leads to enhanced recrystallization in martensite during the intercritical annealing (IA) at 620°C for 5 h. As a result, both ultimate tensile strength (UTS) and total elongation (TE) increase. However, the size of relatively coarse recrystallized austenite grains and the resultant yield strength (YS) remain almost constant in this temperature range. The further increase of rolling temperature to 700-800°C causes a considerable amount of pearlite to be formed during the IA, and then martensite is formed after the IA, resulting in dramatical increases in both YS and UTS but at the great loss of ductility. The warm rolling at 600°C with 63% thickness reduction can produce the steel with the best mechanical combination of 1.2 GPa UTS and 35% TE, due to the formation of many ultrafine austenite grains and strain-induced cementite precipitates. This demonstrates that the mechanical combination of non-V-alloyed medium Mn steel can be improved to an equivalent level of 0.7% V alloyed 10 Mn steel just via the economic strain-induced cementite precipitation.

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    Effect mechanisms of micro-alloying element La on microstructure and mechanical properties of hypoeutectic Al-Si alloys
    Qiuju Zheng, Lili Zhang, Hongxiang Jiang, Jiuzhou Zhao, Jie He
    J. Mater. Sci. Technol., 2020, 47 (0): 142-151.  DOI: 10.1016/j.jmst.2019.12.021
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    The rare earth influence on the as-cast microstructures and mechanical properties of aluminum alloys attracted great attentions in the last decades. But up to date no reports can be found on the effect of micro-alloying element La (La addition is below 0.1 wt.%) on the solidification of hypoeutectic Al-Si alloys. This study carried out solidification experiments with Al-6Si alloys micro-alloyed by element La. The α-Al grain refinement, the eutectic Si modification and the tensile properties improvement caused by micro-alloying element La were investigated. The effect mechanisms of La were discussed. It is demonstrated that the addition of La as low as 100 ppm can deprave the more effective heterogeneous nucleation conditions for the eutectic Si caused by the impurity P. The addition of 0.06 wt.% La is sufficient to achieve an ideal α-Al grain refinement, eutectic Si modification and ductility improvement of the alloys. LaAlSi phase forms in the Al-Si alloy with the additive amount of La higher than 0.06 wt.%. It has a tetragonal structure. Micro-alloying element La refines the α-Al grains by working as a surfactant and modifies the eutectic Si by promoting the formation of the significant multiple Si twins.

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    Retarding the precipitation of η phase in Fe-Ni based alloy through grain boundary engineering
    Honglei Hu, Mingjiu Zhao, Lijian Rong
    J. Mater. Sci. Technol., 2020, 47 (0): 152-161.  DOI: 10.1016/j.jmst.2020.02.018
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    It is important to inhibit the precipitation of η phases in precipitation strengthened Fe-Ni based alloys, as they will deteriorate not only the mechanical property but also the hydrogen resistance. The present investigation shows that grain boundary engineering (GBE) can retard the formation and growth of η phase in J75 alloy. After GBE treatment with 5% cold rolling followed by annealing at 1000 °C for 1 h, the fraction of special boundaries (SBs) increases from 38.4% in conventional alloy to 77.2% and the fraction of special triple junctions increases from 10% to 74%. During 800 °C aging treatment, quite amount of cellular η phases adjacent to random grain boundary (RGB) will be found in conventional alloy, and only a few small η phases have been observed in GBE treatment alloy subjected to the same aging treatment for long time. The reason for GBE in inhibiting precipitation of η phase can be attributed to not only introducing high fraction of SBs but also breaking the connectivity of RGB networks. As nucleation and growth of η phases on SBs are difficult due to their lower Ti concentration and diffusion rate, and the disruption of RGB networks reduces supply of Ti atoms to the η phases significantly, which impedes their growth at RGB.

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    Characterization of nanoparticle mixed 316 L powder for additive manufacturing
    Wengang Zhai, Wei Zhou, Sharon Mui Ling Nai, Jun Wei
    J. Mater. Sci. Technol., 2020, 47 (0): 162-168.  DOI: 10.1016/j.jmst.2020.02.019
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    Nanoparticles reinforced steels have many advantaged mechanical properties. Additive manufacturing offers a new method for fabricating nanoparticles reinforced high performance metal components. In this work, we report the application of low energy ball milling in mixing nanoparticles and micron 316 L powder. With this method, 0.3 and 1.0 wt% Y2O3 nanoparticles can be uniformly distributed on the surface of 316 L powder with the parameters of ball-to-powder ratio at 1:1, speed at 90 rpm and 7 h of mixing. The matrix 316 L powders remain spherical in shape after the mixing process. In the meantime, the effect of low energy ball milling and the addition of Y2O3 nanoparticles on the powder characteristics (flowability, apparent density and tap density) are also studied. Results show that the process of low energy ball milling itself can slightly decrease the flowability and apparent density of the 316 L powder. The addition of 0.3 and 1.0 wt% Y2O3 nanoparticles can also decrease the flowability, the tap density and the apparent density compared with the original 316 L powder. All of these changes result from the rough surface of the mixed powder produced by ball milling and the addition of Y2O3 nanoparticles. The powder’s rough surface can increase the coefficient of friction of powders. The mixture of 316 L powder and Y2O3 nanoparticles can be successfully used for selective laser melting (SLM). The relative density of SLM 316 L-Y2O3 is measured at 99.5%. However, Y2O3 agglomerations were observed which is due to the poor wettability between 316 L and Y2O3.

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    Facile autoreduction synthesis of core-shell Bi-Bi2O3/CNT with 3-dimensional neural network structure for high-rate performance supercapacitor
    Han Wu, Jingdong Guo, De’an Yang
    J. Mater. Sci. Technol., 2020, 47 (0): 169-176.  DOI: 10.1016/j.jmst.2020.02.007
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    Core-shell Bi-Bi2O3/CNT (carbon nanotube) with 3-dimensional neural network structure where Bi-Bi2O3 nanospheres act as cell bodies supported by a 3-dimensional network of CNTs acting as synapses is designed and prepared by simple solvothermal method and subsequent annealing autoreduction treatment, and this structure facilitates the efficient transport of electrons. It can provide two electron transfer paths due to the double contact of Bi2O3 shell with CNT and metal Bi core which enhances the efficiency of the electrochemical reaction. The Bi-Bi2O3/CNT electrode shows a high gravimetric capacitance of 850 F g-1 (1 A g-1), and the specific capacitance of Bi-Bi2O3/CNT can be still 714 F g-1 at 30 A g-1 indicating excellent rate performance. The asymmetric supercapacitor is assembled with Bi-Bi2O3/CNT as the negative electrode and Ni(OH)2/CNT as the positive electrode, delivering a high energy density of 36.7 Wh kg-1 and a maximum power density of 8000 W kg-1. Therefore, the core-shell Bi-Bi2O3/CNT with 3-dimensional neural network structure as the negative electrode of supercapacitor shows great potential in the field of energy storage in the future.

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    Microstructure evolution and mechanical property characterization of a nickel-based superalloy at the mesoscopic scale
    Qiang Zhu, Gang Chen, Chuanjie Wang, Lukuan Cheng, Heyong Qin, Peng Zhang
    J. Mater. Sci. Technol., 2020, 47 (0): 177-189.  DOI: 10.1016/j.jmst.2020.02.021
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    Nickel-based superalloys have become the critical materials of micro-parts depending on outstanding mechanical properties. The effects of the grain size and precipitates on the mechanical properties at the mesoscopic scale are difficult to be revealed using conventional macroscopic material constitutive models. In the present study, the microstructure evolution of the γ″ phase and the tensile mechanical properties of a nickel-based superalloy at the mesoscopic scale were investigated systematically. Three variants of γ″ phases precipitated corresponding to [00], [00] and [001] orientations of the matrix γ phase. The quantitative statistics results showed that as the aging time increases, the particle size and volume fraction of the γ″ phase increase. As the grain size increases, the flow stress decreases due to the dwindling of grain boundary strengthening. Furthermore, the precipitation strengthening of γ″ and γ′ phases induces the increase of flow stress. An important conclusion is drawn that the size effect at the mesoscopic scale depends not only on the sample size and grain size but also on the particle size and volume fraction of the precipitates. The established constitutive model which considers grain boundary strengthening, precipitation strengthening and solid solution strengthening can accurately describe the flow stress characteristics of nickel-based superalloys at the mesoscopic scale.

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    Mechanical properties, biodegradability and cytocompatibility of biodegradable Mg-Zn-Zr-Nd/Y alloys
    Shi Jin, Dan Zhang, Xiaopeng Lu, Yang Zhang, Lili Tan, Ying Liu, Qiang Wang
    J. Mater. Sci. Technol., 2020, 47 (0): 190-201.  DOI: 10.1016/j.jmst.2020.02.017
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    Biodegradable magnesium alloys have been turned out to be a promising candidate for orthopedic applications. In this study, the mechanical properties, degradation behavior and cytocompatibility of Mg-Zn-Zr-Nd and Mg-Zn-Zr-Y alloys were studied in comparison with pure Mg. Mechanical tests showed that the strength and ductility of Mg-Zn-Zr-Nd and Mg-Zn-Zr-Y alloys were excellent. The corrosion resistance analyzed by electrochemical test and immersion test in alpha modified eagle (α-MEM) medium with 10% fetal bovine serum (FBS) revealed the degradation of Mg-Zn-Zr-Nd and Mg-Zn-Zr-Y alloys were faster than pure Mg at an early stage but slowed down after long time immersion. The metal ion concentrations were consistent with the corrosion rate. Mg-Zn-Zr-Nd alloy shows better mechanical properties than pure Mg and better corrosion resistance than Mg-Zn-Zr-Y alloy. The direct and indirect in vitro tests with MC3T3-E1 cells demonstrate that Mg-Zn-Zr-Nd shows the best cytocompatibility and osteogenesis. The results suggest that Mg-Zn-Zr-Nd alloy shows an ideal combination of mechanical, corrosive and biological properties. In summary, these results implying the Mg-Zn-Zr-Nd alloy has great potential to benefit the future development of orthopedic applications.

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    Effects of combined chemical design (Cu addition) and topographical modification (SLA) of Ti-Cu/SLA for promoting osteogenic, angiogenic and antibacterial activities
    Rui Liu, Yulong Tang, Hui Liu, Lilan Zeng, Zheng Ma, Jun Li, Ying Zhao, Ling Ren, Ke Yang
    J. Mater. Sci. Technol., 2020, 47 (0): 202-215.  DOI: 10.1016/j.jmst.2019.10.045
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    Cu has been proved to possess various beneficial biological activities, while sandblasting and acid etching (SLA) is widely used to modify the commercial dental implant in order to improve osseointegration. Based on the above, a novel antimicrobial dental implant material, Ti-Cu alloy, was treated with SLA, to combine chemical design (Cu addition) and topographical modification (SLA). In this work, the effects of SLA treated Ti-Cu alloys (Ti-Cu/SLA) on osteogenesis, angiogenesis and antibacterial properties were evaluated from both in vitro and in vivo tests, and Ti/SLA and Ti-Cu (without SLA) were served as control groups. Benefiting by the combined effects of chemical design (Cu addition) and micro-submicron hybrid structures (SLA), Ti-Cu/SLA had significantly improved inhibitory effects on oral anaerobic bacteria (P. gingivalis and S. mutans) and could induce upregulation of osteogenic-related and angiogenic-related genes expression in vitro. More importantly, in vivo studies also demonstrated that Ti-Cu/SLA implants had wonderful biological performance. In the osseointegration model, Ti-Cu/SLA implant promoted osseointegration via increasing peri-implant bone formation and presenting good bone-binding, compared to Ti/SLA and Ti-Cu implants. Additionally, in the peri-implantitis model, Ti-Cu/SLA effectively resisted the bone resorption resulted from bacterial infection and meanwhile promoted osseointegration. All these results suggest that the novel multiple functional Ti-Cu/SLA implant with rapid osseointegration and bone resorption inhibition abilities has the potential application in the future dental implantation.

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    Achieving strong microwave absorption capability and wide absorption bandwidth through a combination of high entropy rare earth silicide carbides/rare earth oxides
    Heng Chen, Biao Zhao, Zifan Zhao, Huimin Xiang, Fu-Zhi Dai, Jiachen Liu, Yanchun Zhou
    J. Mater. Sci. Technol., 2020, 47 (0): 216-222.  DOI: 10.1016/j.jmst.2020.02.015
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    Developing electromagnetic (EM) wave absorbing materials with low reflection coefficient and optimal operating frequency band is urgently needed on account of the increasingly serious EM pollution. However, the applications of common EM absorbing materials are encumbered by poor high-temperature stability, poor oxidation resistance, narrow absorption bandwidth or high density. Herein, the strong EM absorption capability and wide efficient absorption bandwidth of high entropy ceramics are reported for the first time, which are designed by a combination of the novel high entropy (HE) rare earth silicide carbides/rare earth oxides (RE3Si2C2/RE2O3). Three HE powders, i.e., HERSC-1 (HE (Tm0.2Y0.2Dy0.2Gd0.2Tb0.2)3Si2C2), HERSC-2 HE (Tm0.2Y0.2Pr0.2Gd0.2Dy0.2)3Si2C2/HE (Tm0.2Y0.2Pr0.2Gd0.2Dy0.2)2O3) and HERSC-3 (HE (Tm0.2Y0.2Pr0.2Gd0.2Tb0.2)3Si2C2/HE (Tm0.2Y0.2Pr0.2Gd0.2Tb0.2)2O3), are synthesized. Although HERSC-1 exhibits a limited absorption effect (the minimum reflection loss (RLmin) is -11.6 dB at 3.4 mm) and a relatively narrow effective absorption bandwidth (EAB) of 1.7 GHz, the optimal absorption RLmin value and EAB of HERSC-2 and HERSC-3 are -40.7 dB (at 2.9 mm), 3.4 GHz and-50.9 dB (at 2.0 mm), 4.5 GHz, respectively, demonstrating strong microwave absorption capability and wide absorption bandwidth. Considering the better stability, low density and strong EM absorption effect, HE ceramics are promising as a new type of EM absorbing materials.

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    High surface area, high catalytic activity titanium dioxide aerogels prepared by solvothermal crystallization
    Xian Yue, Junhui Xiang, Junyong Chen, Huaxin Li, Yunsheng Qiu, Xianbo Yu
    J. Mater. Sci. Technol., 2020, 47 (0): 223-230.  DOI: 10.1016/j.jmst.2019.12.017
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    Titanium dioxide has been considered to be one of the most effective and environmental friendly photocatalytic material. It has been widely used in photocatalytic degradation of various pollutants. As we known, an anatase crystal form typically obtained by high temperature heat treatment (>600℃), usually shows higher catalytic activity. In order to further improve the catalytic efficiency, we prepared TiO2 with a non-supercritical drying method to form a high specific surface area aerogel structure, along with an increased active contact site. However, with the inevitable of internal pores collapse in the process of high temperature crystallization, a large amount of porous structure and specific surface area is reduced. Here, to enhance the photocatalytic activity of titania, we propose a synergistic strategy to fabricate a porous titania structure with a high specific surface area. It was crystallized at a lower temperature (120℃) in a low-boiling solvent (ethanol, acetone, etc.). The lattice structure was identified by X-ray diffractometry; specific surface area (over 300 m2/g) of our sample was also measured through BET test; in the subsequent photocatalytic degradation test, the photocatalytic degradation efficiency of fabricated TiO2 is proved to be more excellent than P25 powder. By a freeze-drying/mild crystallization method, a high-specific surface area and high catalytic activity TiO2 aerogel was synthetized. This study provides some insights in the combining of crystallization and high specific surface area of titanium dioxide photocatalysis.

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    A modified theta projection model for creep behavior of RPV steel 16MND5
    Peng Yu, Weimin Ma
    J. Mater. Sci. Technol., 2020, 47 (0): 231-242.  DOI: 10.1016/j.jmst.2020.02.016
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    During a hypothetical severe accident of light water reactors, the reactor pressure vessel (RPV) could fail due to its creep under the influence of high-temperature corium. Hence, modelling of creep behavior of the RPV is paramount to reactor safety analysis since it predicts the transition point of accident progression from in-vessel to ex-vessel phase. In the present study we proposed a new creep model for the classical French RPV steel 16MND5, which is adapted from the “theta-projection model” and contains all three stages of a creep process. Creep curves are expressed as a function of time with five model parameters θi(i=1-4 and m). A model parameter dataset was constructed by fitting experimental creep curves into this function. To correlate the creep curves for different temperatures and stress loads, we directly interpolate the model’s parameters θi(i=1-4 and m) from this dataset, in contrast to the conventional “theta-projection model” which employs an extra single correlation for each θi(i=1-4 and m), to better accommodate all experimental curves over the wide ranges of temperature and stress loads. We also put a constraint on the trend of the creep strain that it would monotonically increase with temperature and stress load. A good agreement was achieved between each experimental creep curve and corresponding model’s prediction. The widely used time-hardening and strain-hardening models were performing reasonably well in the new method.

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    Additive manufacturing of composite materials and functionally graded structures using selective heat melting technique
    Kalaimani Markandan, Ruijing Lim, Pawan Kumar Kanaujia, Ian Seetoh, Muhammad Raziq bin Mohd Rosdi, Zhi Huey Tey, Jun Seng Goh, Yee Cheong Lam, Changquan Lai
    J. Mater. Sci. Technol., 2020, 47 (0): 243-252.  DOI: 10.1016/j.jmst.2019.12.016
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    The feasibility of using selective heat melting (SHM) to fabricate composite materials and functionally graded structures was investigated. We report, for the first time, the successful 3D printing of copper (Cu)-polyethylene (PE) composite, iron (Fe)-polyethylene (PE) composite and functionally graded CuO foams using the SHM technique. It was found that a low feed rate, high airflow rate and high airflow temperature were required for efficient delivery of heat from the emitted hot air to the powder bed, so that the PE binder particles can melt and form dense composites with smooth surfaces. The best mechanical properties were exhibited by composites with 80 vol.% PE, as lower PE concentrations led to deficient binding of the metal particles, while higher PE concentrations meant that very few metal particles were available to strengthen the composite. The strength exhibited by Cu-PE composites was comparable to engineering plastics such as polycarbonate, with the added advantage of being electrically conductive. The average conductivity of the samples, 0.152 ± 0.28 S/m, was on par with physically cross-linked graphene assemblies. By subjecting a Cu-PE composite, with Cu concentration graded from 10 vol.% to 30 vol.%, to a high temperature debinding and sintering treatment in air, CuO foam with graded porosity can be obtained. This CuO foam was observed to fail in a layer-by-layer manner under mechanical compression, which is a characteristic of functionally graded materials. Our study shows that, compared to existing 3D printing techniques, SHM can be cheaper, have wider material compatibility, occupy a smaller footprint and potentially induce less residual stresses in the fabricated parts. Therefore, it could be a valuable complement to current additive manufacturing techniques for fabricating mechanically strong composite materials and functionally graded structures.

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