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Structural stability of single-layered LaNi_4.25Al_0.75 film and its electro-chemical hydrogen-storage properties

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Rare Metals 2006年第5期25卷 543-548页

作者： WANG Zhongmin Chi Ying Vanessa Li zhou huaiying Sammy Lap Ip Chan SHI Liu Center of Material Science and Engineering Guilin University of Electronic Technology Guilin 541004 China School of Materials Science and Engineering University of New Sooth Wales Sydney NSW 2052 Australia Institute of Metal Research Chinese Academy of Sciences China

AB5-based hydrogen storage thin fdms （LaNi4.25Al0.75）, deposited on Cu substrate by dc magnetron sputtering were investigated in this study. X-ray diffraction （XRD） revealed that the microstructure of the layer was in crystal form. SEM and AFM analyses proved that the film appeared to be rather rough with numerous randomly sized pores of approximately 15-40 in nm diameter. Structural stability of the film was examined by the combined analyses of DSC, XRD, and SEM, which indicated that this film maintained its structural stability below 500 K or so, and a network structure was observed on the film after being heated at 700 K for 30 min. Electrochemical hydrogen-storage properties of the films were investigated by simulated battery tests. It was found that single-layered LaNi4.25A10.75 film exhibited electrochemical hydrogen-storage properties similar to typical AB5 alloys in bulk, and the maximum discharge capacity of the film was about 220 mAh/g. After 20 charge/discharge cycles, small needle-shaped aluminium oxide was formed on some fractions of the film surface.

关键词： hydrogen storage thin film magnetron sputtering structural stability electrochemical properties

Influence of A-site doping barium on structure,magnetic and microwave absorption properties of LaFeO_(3)ceramics powders

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Journal of Rare Earths 2022年第7期40卷 1106-1117页

作者： Lei Huang Lichun Cheng Shunkang Pan Qingrong Yao Qianxin Long Man Wang Yucheng Chen huaiying zhou School of Materials Science and Engineering Guilin University of Electronic TechnologyGuilin 541004China Guangxi Key Laboratory of Information Materials Guilin University of Electronic TechnologyGuilin 541004China

In this paper,the effect of Ba^(2+)ions A-site doping LaFeO_(3)on structure,magnetic properties and microwave absorption properties was investigated by the sol-gel method.According to the TEM and FullProf refinement results,the structure of LaFeO_(3)changes from orthogonal(SG:Pnma)to cubic(SG:Pm-3 m)when the Ba doping amount is x=0.4.The SEM image shows that the particles size tends to decrease with the increase of Ba content.The production of weak ferromagnetism indicates that Ba doping has a significant effect on the magnetic properties of LaFeO_(3).The Neel temperature(TN)decreases significantly with the increase of Ba doping amount.An appropriate amount of Ba doping can effectively increase the dielectric and magnetic loss of LaFeO_(3)ceramics powders.The increase permittivity(ε’andε″)may be attributed to the hopping of the electrons between the Fe^(3+)and Fe^(4+)ions with the Ba^(2+)ions doping.The minimum reflection loss(RL_(min))of La_(0.9)Ba_(0.1)FeO_(3)at 6.72 GHz reaches-30.04 dB,its effective bandwidth(RL≤-10 dB)is 2.1 GHz,and the matching thickness is only 3.2 mm.These results indicate that Ba doping can effectively control the microwave absorption properties of LaFeO_(3),especially in the Cband.

关键词： LaFeO_(3)ceramics Crystal structure Magnetic Electromagnetic parameters Microwave absorption Rare earths

Improvement in magnetic properties,corrosion resistance and microstructure of Nd-Fe-B sintered magnets through intergranular addition of Tb_(68)Ni_(32)

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Journal of Rare Earths 2022年第5期40卷 784-791,I0004页

作者： Jia Li Qingrong Yao Weichao Huang Jue Xie Zhilin Mo Jianqiu Deng Jiang Wang Guanghui Rao huaiying zhou Guangxi Key Laboratory of Information Materials School of Materials Science and EngineeringGuilin University of Electronic TechnologyGuilin 541004China China Rare Metals and Rare Earth(Guangxi)Jinyuan New Materials Co. Ltd.Hezhou 542603China

New energy vehicles and offshore wind power industries have a high demand for sintered Nd-Fe-B magnets with high intrinsic coercivity and high corrosion resistance.In this study,the magnetic properties,anticorrosion properties,and micro structure of Nd-Fe-B sintered magnets with the intergranular addition of low-melting-point eutectic Tb_(68)Ni_(32) alloy powders were investigated.The aim is to determine if the addition of Tb_(68)Ni_(32) can improve these properties.A low melting-point eutectic alloy Tb_(68)Ni_(32) powders was prepared as a grain boundary additive and blended with the master alloy powders prior to sintering.The coercivity of the resultant magnets gradually increases from 1468 to 2151 kA/m by adding increasing amounts of Tb_(68)Ni_(32).At the same time,the remanence first increases and then slightly decreases.After studying the microstructure and elemental composition of the Tb_(68)Ni_(32) added magnets,it is found that the significant increase in coercivity and the negligible reduction in remanence is due to densificatio n,improved grain orientation,a unifo rm and continuous boundary phase distribution,as well as the generation of a(Nd,Pr,Tb)_(2) Fe_(14)B "core-shell" structure surrounding the main-phase grain.Moreover,the corrosion resistance of the magnet is greatly improved owing to the enhancement of electrochemical stability,as well as the optimization of the distribution and morphology of the intergranular phase.

关键词： Nd-Fe-B sintered Magnets Tb_(68)Ni_(32)alloy Magnetic properties Corrosion resistance Microstructure Rare earths

Effect of wheel speed on phase formation and magnetic properties of (Nd_(0.4)La_(0.6))-Fe-B melt-spun ribbons

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Journal of Rare Earths 2018年第11期36卷 1179-1183页

作者： Liang Wang Jiang Wang Maohua Rong Guanghui Rao huaiying zhou School of Material Science and Engineering & Guangxi Key Laboratory of Information Materials Guilin University of Electronic Technology Guilin 541004China

The effect of wheel speed on phase formation and magnetic properties of （Ndo.4La0.6）lsFeTzsBzs and （Ndo.4La0.6）13.4Fe79.9B6.7 ribbons prepared by melt-spinning method was investigated experimentally. Based on X-ray diffraction results, all melt-spun ribbons consist of the main phase with the tetragonal 2：14：1 type structure and the minor α-Fe phase. Magnetic measurements show the maximum magnetic energy product （（BH）max） and the remanence （Mr） increases firstly and then decreases with the increase of wheel speed, while the coercivity （Hci） increases, resulting from the variation of the average volume fraction of the ^-Fe phase and the average grain size in the melt-spun ribbons. Using Henkel plots, the interaction between the 2：14：1 phase and the ^-Fe phase in the melt-spun ribbons was analyzed and the intergranular exchange coupling is manifested. Optimal magnetic properties of Hci - 7.27 kOe, Mr - 90.94 emu/g and （BH）max -- 12.10 MGOe are achieved in the （Ndo.4La0.6）lsFeTzsBT.s ribbon with the wheel speed of 26 m/s. It indicates that magnetic properties of Nd-Fe-B melt-spun ribbons with highly abundant rare earth element La can be improved by optimizing alloy composition and preparation process.

关键词： Nd-La-Fe-B ribbons Phase formation Melt-spinning Magnetic properties Rare earths

Effect of heat treatment on hydrogen storage properties and thermal stability of V68Ti20Cr12 alloy

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Progress in Natural Science:Materials International 2017年第5期27卷 543-549页

作者： Maohua Rong Feng Wang Jiang Wang Zhongmin Wang huaiying zhou School of Materials Science and Engineering & Guangxi Key Laboratory of Information Materials Guilin University of Electronic Technology School of Materials Science and Engineering Beihang University

Effect of heat treatment on the crystal structure, microstructure, hydrogen storage properties and thermal stability of V68Ti20Cr12alloy prepared by arc-melting was studied in this work. It was found that both the as-cast and annealed(973 K/72 h) V68Ti20Cr12alloys consisted of a single body-centered cubic(bcc) phase. After heat treatment, the hydrogen absorption/desorption kinetic characteristics of the as-cast alloy was improved greatly due to the homogeneous composition and perfect structure. The mechanism of hydrogen absorption/desorption process in the as-cast and annealed alloys was further investigated according to the Johnson-Mehl-Avrami(JMA) equation. The hydrogen absorption process of the as-cast and annealed alloys would be controlled by the one-dimensional diffusion process, while the hydrogen desorption process in the as-cast and annealed alloys was dominated by the geometrical contraction model. The pressure-composition-temperature(PCT) measurements show that the plateau pressure of the annealed alloy becomes comparatively flat. Furthermore, the activation energies of the dehydrogenation in the as-cast and annealed alloys were calculated using the Kissinger method, indicating that heat treatment is a very beneficial way to improve hydrogen absorption/desorption kinetics of the alloy.

关键词： V-Ti-Cr alloys Hydrogen storage properties Thermal stability Heat treatment

Phase diagrams of permanent magnet alloys: Binary rare earth alloy systems

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Journal of Rare Earths 2019年第10期37卷 1040-1046页

作者： Kaicheng Yang Jiang Wang Qingrong Yao Zhao Lu Maohua Rong huaiying zhou Guanghui Rao School of Materials Science and Engineering & Guangxi Key Laboratory of Information Materials Guilin University of Electronic Technology

Thermodynamic optimization of the binary rare earth alloy(Cee La, Cee Pr, Cee Nd and Lae Nd) systems was performed in this work through the CALPHAD method based on the critical evaluation of all available phase diagram and thermodynamic data reported in the literature. During the thermodynamic modeling, the solution phases including liquid, bcc, fcc and dhcp, were treated as the substitutional solution model. Thermodynamic parameters of the stable phases in the Cee La, Cee Pr, Cee Nd and Lae Nd binary systems are obtained finally and would be used directly to develop the thermodynamic database of the multi-component Nde Fee B-based alloys, which is indispensable for designing alloy compositions and processes of Nde Fee B permanent magnets with highly abundant rare earth metals.

关键词： Permanent magnets Rare earth alloys Phase diagrams CALPHAD

Effects of Sm-doping on microstructure,magnetic and microwave absorption properties of BiFeO_(3)

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Journal of Rare Earths 2021年第7期39卷 835-843,I0003页

作者： Chuang Tian Qingrong Yao Zhaofei Tong huaiying zhou Guanghui Rao Jianqiu Deng Zhongmin Wang Jiang Wang School of Materials Science and Engineering Guilin University of Electronic TechnologyGuilin 541004China Guangxi Key Laboratory of Information Materials Guilin University of Electronic TechnologyGuilin 541004China

In this paper,polycrystalline samples of Bi_(1-x)Sm_(x)FeO_(3)(x=0,0.05,0.1,0.15) were successfully synthesized by sol-gel method.The effects of Sm concentration on the crystal structure,morphology,chemical states,magnetic properties and microwave absorption performance were studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),a vibrating sample magnetometer(VSM) and a Vector network analyzer(VNA),respectively.The results show that the rare earth Sm doping causes the crystal structure to change.When x≤0.1,Bi_(1-x)Sm_(x)FeO_(3) is the distorted rhombohedral structure with space group R3c.With the increase of Sm doping amount to x=0.15,the phase structure of Bi_(1-x)Sm_(x)FeO_(3) changes from rhombohedral structure to cubic structure with the space group Pm3 m.The particle size decreases with the increase of the Sm doping amount.The analysis results show that Sm doping can effectively reduce the oxygen vacancies and significantly improve its magnetic properties.The results exhibit that moderately doped rare earth Sm element can effectively improve microwave absorption properties of Bi_(1-x)Sm_(x)FeO_(3) powders.When Sm doping amount of x is 0.1,the Bi_(0.9)Sm_(0.1)FeO_(3) compound has good microwave absorption performance,and the minimum reflection loss value of Bi_(0.9)Sm_(0.1)FeO_(3) powder reaches about-32.9 dB at11.7 GHz,and its effective absorption bandwidth(RL <-10 dB) is 2.6 GHz with the optimal matching thickness of 2.0 mm.

关键词： BiFeO_(3) Crystal structure Magnetic properties Microwave absorption Reflection loss Rare earths

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刘庄墓地年代、性质的再认识

华夏考古 2024年第3期 50-60页

作者：常怀颖中国社会科学院考古研究所北京市100101

依据邻近地区同类器的排比,刘庄墓地的年代上限当不会早于相当于二里头文化二期,文化属性也不属于下七垣文化。刘庄墓地反映了夏商之际,太行山东、西麓间存在人群的往来互动,太行山以西地区经由豫北与二里头文化的核心区发生交流。

关键词：刘庄墓地下七垣文化太行山西麓

Parallel Physics-Informed Neural Networks Method with Regularization Strategies for the Forward-Inverse Problems of the Variable Coefficient Modified KdV Equation

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Journal of Systems Science & Complexity 2024年第2期37卷 511-544页

作者： zhou Huijuan School of Science Shanghai Maritime UniversityShanghai 201306China

This paper mainly introduces the parallel physics-informed neural networks(PPINNs)method with regularization strategies to solve the data-driven forward-inverse problems of the variable coefficient modified Korteweg-de Vries(VC-MKdV)equation.For the forward problem of the VC-MKdV equation,the authors use the traditional PINN method to obtain satisfactory data-driven soliton solutions and provide a detailed analysis of the impact of network width and depth on solving accuracy and speed.Furthermore,the author finds that the traditional PINN method outperforms the one with locally adaptive activation functions in solving the data-driven forward problems of the VC-MKdV equation.As for the data-driven inverse problem of the VC-MKdV equation,the author introduces a parallel neural networks to separately train the solution function and coefficient function,successfully addressing the function discovery problem of the VC-MKdV equation.To further enhance the network’s generalization ability and noise robustness,the author incorporates two regularization strategies into the PPINNs.An amount of numerical experimental data in this paper demonstrates that the PPINNs method can effectively address the function discovery problem of the VC-MKdV equation,and the inclusion of appropriate regularization strategies in the PPINNs can improves its performance.

关键词： Data-driven forward-inverse problems parallel physics-informed neural networks regularization strategies variable coefficient modified KdV equation