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Shear transformation zone dependence of creep behaviors of amorphous phase in a CuZr-based bulk metallic glass composite

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Science China(Technological Sciences) 2020年第8期63卷 1560-1565页

作者： JIANG SongShan GAN KeFu HUANG YongJiang XUE Peng SUN JianFei State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China School of Materials Science and Engineering Central South UniversityChangsha 410083China

The creep behaviors of the amorphous phase in a CuZr-based bulk metallic glass composite(BMGC)are studied by nanoindentation.Samples fabricated via higher cooling rates are found to exhibit more prominent creep,but a smaller shear viscosity.The volume of the shear transformation zones(STZs)in the amorphous phase calculated based on a cooperative shear model increases with the cooling rate.The evolution of excess free volume created during creep deformation is clarified.A looser atomic arrangement leads to a larger STZ volume,thus facilitating creep deformation.This study gives a better understanding of the deformation behaviors of the amorphous phase in BMGCs.

关键词： bulk metallic glass composite amorphous phase cooling rate shear viscosity shear transformation zone free volume

amorphous Structure and Bonding Chemistry of Aluminium Antimonide（AISb） Alloy for phase-change Memory Device

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Chemical Research in Chinese Universities 2016年第1期32卷 76-81页

作者： SUN Yu WANG Xuepeng DU Jiaren CHEN Nianke YU Hongmei WU Qi MENG Xing State Key Laboratory on Integrated Optoelectronics College of Electronic Science and Engineering College of Computer Science and Technology College of Physics Jilin University Changchun 130012 P. R. China

With the help of first-principles molecular dynamics calculations, we obtained the atomic picture of amorphous A1Sb（a-A1Sb） for phase-change memory application. Generally, a-A1Sb shows sp3 bonding network, which is the intrinsic characteristic for its good thermal stability. Significant wrong（homogenous） AI-AI bonds can also be observed from the pair correlation function. This hints the amorphous phase may consist of A1 cluster and Sb-rich A1-Sb alloy. Recent experiment has observed the Sb-rich region of AISb alloy can be switched to crystal, on the basis of which, combined with our calculations, we thus propose that on the one hand such a Sb-rich region in a-A1Sb can retain the rapid crystallization like pure Sb solid and on the other hand some AI atoms play the important role of stabilizing Sb rich network with sp3 bonding. The present study offers a microscopic view to understand the phase change mechanism of AlSb alloy for information storage device.

关键词： AISb alloy amorphous phase phase-change memory device Ab initio calculation

Subsurface damage pattern and formation mechanism of monocrystalline β-Ga_(2)O_(3) in grinding process

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Frontiers of Mechanical Engineering 2022年第2期17卷 117-127页

作者： Xin YANG Renke KANG Shang GAO Zihe WU Xianglong ZHU Key Laboratory for Precision and Non-Traditional Machining Technology of Ministry of Education Dalian University of TechnologyDalian 116024China

Monocrystalline beta-phase gallium oxide (β-Ga_(2)O_(3)) is a promising ultrawide bandgap semiconductor material. However, the deformation mechanism in ultraprecision machining has not yet been revealed. The aim of this study is to investigate the damage pattern and formation mechanism of monocrystalline β-Ga_(2)O_(3)in different grinding processes. Transmission electron microscopy was used to observe the subsurface damage in rough, fine, and ultrafine grinding processes. Nanocrystals and stacking faults existed in all three processes, dislocations and twins were observed in the rough and fine grinding processes, cracks were also observed in the rough grinding process, and amorphous phase were only present in the ultrafine grinding process. The subsurface damage thickness of the samples decreased with the reduction in the grit radius and the grit depth of cut. Subsurface damage models for grinding process were established on the basis of the grinding principle, revealing the mechanism of the mechanical effect of grits on the damage pattern. The formation of nanocrystals and amorphous phase was related to the grinding conditions and material characteristics. It is important to investigate the ultraprecision grinding process of monocrystalline β-Ga_(2)O_(3). The results in this work are supposed to provide guidance for the damage control of monocrystalline β-Ga_(2)O_(3)grinding process.

关键词： monocrystalline beta-phase gallium oxide grinding process subsurface damage nanocrystals amorphous phase

Visible-Light Excitated Photocatalytic Activity of Rare Earth Metal-Ion-Doped Titania

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Journal of Rare Earths 2002年第6期20卷 619-625页

作者：谢一兵李萍袁春伟 National Laboratory of Molecular & Biomolecular Electronics Southeast University

The rare earth ion Ce 4+ doped TiO 2 was prepared by sol-gel method. The average particle sizes are about 10 nm for sol phase and 55 nm for polycrystalline phase. The photocatalytic activities to degrade Reactive Brilliant Red Dye X-3B were investigated. The result reveals that the spectrum response of Ce 4+-TiO 2 has extended to visible region from the UV region(λamorphous phase Ce 4+-TiO 2 sol with an electron scavenger (1.0% atom fraction Ce 4+ ion doping amount) shows the capability of the photocatalytic degradation of the dye X-3B as well as the nanocrystallite Ce 4+-TiO 2 with an interband trap site. Despite of the difference in the morphology of Ce 4+-TiO 2 photocatalyst, there is no apparent difference in respect of the decoloring effects. Whereas, polycrystalline phase Ce 4+-TiO 2 exhibits strong photomineralization power in comparison with the amorphous phase. The photocatalytic oxidation mechanisms of the dye molecule mainly involved in the self-photo-sensitization photolysis process by the first excited singlet oxygen ( 1O 2) and photocatalysis process by hydroxyl radicals(·OH) under visible light irradiation.

关键词： rare earths amorphous phase polycrystalline phase photocatalysis process self-photo-sensitization photolysis interband trap site electron scavenger

Effect of Cu content on microstructure and mechanical properties of in-situ β phases reinforced Ti/Zr-based bulk metallic glass matrix composite by selective laser melting(SLM)

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Journal of Materials Science & Technology 2021年第8期67卷 174-185页

作者： Xuehao Gao Xin Lin Qiaodan Yan Zihong Wang Xiaobin Yu Yinghui Zhou Yunlong Hu Weidong Huang State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an710072China Key Laboratory of Metal High Performance Additive Manufacturing and Innovative Design MUT ChinaNorthwestern Polytechnical UniversityXi'an710072China

In this study,non-toxic in-situβphases of reinforced Ti/Zr-based bulk metallic glass matrix composites(BMGCs)of(Ti_(0.65)Zr_(0.35))100-xCux(x=5,10,15 at.%)are fabricated via selective laser melting.The effect of Cu content on phase formation,microstructure,and mechanical properties is investigated.The average volume fraction and width of theβphase decreases with increasing Cu content,while a more amorphous phase and the(Ti,Zr)_(2)Cu phase forms.In the center zone of the molten pool,theβphase grows in the direction of the temperature gradient,and the amorphous phase distributes among theβphases.This occurs using:sphere morphology(for x=5),a more continuous elongated sphere and network morphology(for x=10),and network morphology(for x=15),respectively.In the edge zone of the molten pool,due to the smaller cooling rate and the existence of a partially molten zone,theβphase becomes coarser,and an amorphous phase forms for more continuous networks.Furthermore,the hardness improves significantly with increasing Cu content.No crack is found for x=5.Although the average volume fraction of theβphase for x=5 is about 90%,the compression yield strength is 1386±64 MPa,reaching to an average level of conventionally fabricated counterparts,due to finer microstructure,and twinning and martensitic transformation of theβphase.

关键词： Metallic glass amorphous phase βphase Bulk metallic glass matrix composites(BMGCs) Additive manufacturing(AM) Selective laser melting(SLM)

Magnetic properties of Nd_2Fe_(14)B/α-Fe nanocomposite magnets with yttrium addition

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Rare Metals 2010年第3期29卷 265-269页

作者： CHEN Zhi'an SUI Yanli GUO Zhimeng Institute of Powder Metallurgy University of Science and Technology Beijing Beijing 100083 China State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Beijing 100083 China

The phase evolution and magnetic properties of Nd9？xYxFe72Ti2Zr2B15 （x = 0,0.5,1,and 2） melt-spun nanocomposite ribbons were studied.It is found that Y addition not only enhances the formability of amorphous phase in the alloy,but also stabilizes the amorphous phase during the annealing treatment.The appropriate content of Y addition effectively enhances the remanence （Jr） of the annealed sample.The residual amorphous intergranular phase in the annealed sample optimizes the squareness of the loop,resulting in an larger maximum energy product （BH）max.The best magnetic properties,Jr = 0.78 T,Hci （coercivity） = 923.4 kA/m,and （BH）max = 98.5 kJ/m3,were obtained from the Nd8YFe72Ti2Zr2B15 ribbon spun at Vs = 4 m/s and annealed at 700°C for 10 min,which is composed of Nd2Fe14B,α-Fe,and amorphous phase.

关键词： magnetic properties nanocomposite yttrium addition formability amorphous phase

amorphous molybdenum sulfide mediated EDTA with multiple active sites to boost heavy metal ions removal

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Chinese Chemical Letters 2021年第9期32卷 2797-2802页

作者： Qi Huang Yizhong Zhang Wei Zhou Xiang Huang Yiliang Chena Xin Tan Tao Yu School of Chemical Engineering and Technology Tianjin UniversityTianjin 300350China School of Environmental Science and Engineering Tianjin UniversityTianjin 300350China School of Science Tibet UniversityLhasa 850000China School of Science Tianjin UniversityTianjin 300350China Research Center of Environmental Pollution Control Engineering Technology Chinese Research Academy of Environmental SciencesBeijing 100012China

The rational design of strong affinity adsorbents for heavy metal ions removal remains a critical challenge for water treatment.In this study,amorphous molybdenum sulfide composites(EDTA-MoSx(x=2,3))were fabricated via a facile hydrothermal method mediated by EDTA,which was applied to heavy metal ions(Cu^(2+),Cd^(2+),Pb^(2+),Zn^(2+)and Ni^(2+))removal from aqueous solutions.A case study for Cu^(2+)ions showed that the adsorption capacity of EDTA-MoSx(x=2,3)was superior to crystalline phase MoS2 at pH 6.0 with an initial concentration of 200 mg/L.Adsorption mechanisms of different sulfide groups and—COOH of EDTA-MoSx(x=2,3)were verified systematically via a series of experiments,characterizations,and density functional theory(DFT)calculations.Both bridging S_(2)^(2-)and—COOH covalently bonded with Cu^(2+)ions were ascribed to the critical factors for this enhanced removal efficiency on the surface of EDTA-MoSx(x=2,3).This work offers a new method to enhance the adsorption performance of molybdenum sulfide-based materials by controlling crystallinity mediated with an organic complex small molecule.

关键词： amorphous phase MoS_(2) MoS_(3) Adsorption Heavy metal ions DFT calculations

Fabrication and microstructure of nanostructured Mg-3Ni-2MnO_(2) by ball milling in hydrogen atmosphere

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Transactions of Nonferrous Metals Society of China 2009年第S2期19卷 359-362页

作者：房文斌房娃孙宏飞于振兴 School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China

Nanostructured Mg-3Ni-2MnO_(2) was synthesized by ball milling elemental powders of Mg,Ni and MnO_(2) in hydrogen atmosphere.The microstructures of the powder prepared at different milling time were analyzed by X-ray diffractometry(XRD), scanning electron microscopy(SEM)and high resolution electron microscopy(HREM).The milling time is the most key parameter impacting on the grain size and the microstructure of material.With prolonging the milling time,particle size becomes smaller and smaller.But after the ball milling time reaches about 20 h,reduction of grain size becomes slowly.When the milling time is more than 50 h,nanocrystalline fully forms.When the milling time is more than 80 h,there are more amorphous phases in materials.The average particle diameter of material is about 1μm and the grain size is 10-30 nm.

关键词： nanocrystalline ball milling grain size amorphous phase

amorphous Formation in an Undercooled Binary Ni-Si Alloy under Slow Cooling Rate

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Journal of Materials Science & Technology 2009年第3期25卷 370-372页

作者： Yiping Lu Gencang Yang Xiong Li Yaohe Zhou State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xilan 710072 China

High undercooling up to 392 K was achieved in eutectic Ni70.2Si29.8 alloy melt by using glass fluxing combined with cyclic superheating. A small quantity of amorphous phase was obtained in bulk eutectic Ni70.2Si29.8 alloy when undercooling exceeds 240 K under slow cooling conditions （about 1 K/s）. The amorphous phase was confirmed by high-resolution transmission electron microscopy and differential scanning calorimetry.

关键词： Eutectic alloy amorphous phase Rapid solidification