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Thermal stability improvement and microstructure optimization of high cobalt content Nd-Fe-B magnets via terbium grain boundary diffusion

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Journal of Rare Earths 2024年第8期42卷 1531-1538,I0004页

作者： jiyuan xu Ruiyang Meng Jing Liu Jiateng Zhang Rui Han Yikun Fang Shengzhi Dong Wei Li Division of Functional Materials Research Central Iron and Steel Research InstituteBeijing100081China

The substitution of Fe by Co in the 2:14:1 phase is an effective method to increase the Curie temperature and enhance the thermal stability of the Nd-Fe-B ***,the accumulation of Co ele ment at the grain boundaries(GBs) changes the GBs from nonmagnetic to ferromagnetic and causes the thinlayer GBs to become rare,In this paper,the method of diffusing Tb element was chosen to improve the microstructure and temperature stability of high-Co *** original sintered Nd_(28.5)Dy_(3)-CO_(x)e_(bal)M_(0.6)B_(i)(x=0,6 wt%,12 wt%;M = Cu,Al,Zr) magnets with different Co contents were diffused with Tb by grain boundary diffusion(GBD).After GBD,high-Co magnets exhibit more continuously distributed thin-layer GBs,and their thermal stability is significantly *** high-Co magnets(x=6 wt%),the absolute value of the temperature coefficient of coercivity decreases from 0.603%/K to0.508%/K in the temperature range of 293-413 K,that of remanence decreases from 0.099%/K to 0.091%/K,and the coercivity increases from 18.44 to 25.04 *** electron microscopy(TEM)characterization reveals that there are both the 1:2 phase and the amorphous phase in the high-Co magnet before and after GBD,EDS elemental analysis shows that Tb element is more likely to preferentially replace the rare earth elements in the 2:14:1 main phase than in the 1:2 phase and the amorphous *** concentration of Tb at the edge of the main phase is much higher than that in the 1:2phase and amorphous phase,which is beneficial to the improvement of the *** preferential replacement of Tb elements at the edge of the 2:14:1 phase and thin-layer GBs with a more continuous distribution are synergistically responsible for improving the thermal stability of high-Co *** study indicates that GBD is an effective method to improve the microstructure and thermal stability of high-Co magnets.

关键词： Nd-Fe-B magnets Coercivity Grain boundary diffusion Thermal stability Micro structure Rare earths

Design and fabrication of Nd-Fe-B magnet with excellent thermal stability

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Journal of Rare Earths 2024年第5期42卷 980-986,I0006页

作者： Rui Han Shengzhi Dong Dong Li Dongmin Zhang Hongsheng Chen jiyuan xu George CHadjipanayis Zhuolin Li Ying Zhang Wei Li Division of Functional Materials Research Central Iron and Steel Research InstituteBeijing100081China Department of Physics and Astronomy Sharp Lab University of DelawareNewarkDE19716USA Beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing100190China

A novel Nd-Fe-B type permanent magnet with excellent thermal stability was designed by Co replacing Fe in the main phase and the grain boundary *** remanence and coercivity temperature coefficient reach 0.058%/℃and 0.465%/℃in the te mperature range from 25 to 100℃,which are much lower than those of commercial Nd-Fe-B *** enhanced Curie temperature is obtained for the novel magnet due to the Co substitution,which significantly improves the operating *** microstructure result reveals that an amorphous phase exists in the intergranular grains which is probably responsible for the deterioration of intrinsic *** work can provide a reference for the design and optimization of components of sintered Nd-Fe-B magnets with excellent thermal stability.

关键词： Thermal stability Remanence temperature coefficient Operating temperature Atomic substitution Rare earths

Grassland degradation in the ＂Three-River Headwaters＂ region, Qinghai Province

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Journal of Geographical Sciences 2008年第3期18卷 259-273页

作者： LIU jiyuan xu Xinliang SHAO Quanqin Institute of Geographic Sciences and Natural Resources Research CAS Beijing 100101 China

Supported by MSS images in the mid and late 1970s,TM images in the early 1990s and TM/ETM images in 2004,grassland degradation in the＂Three-River Headwaters＂region （TRH region）was interpreted through analysis on RS images in two time series,then the spatial and temporal characteristics of grassland degradation in the TRH region were analyzed since the *** results showed that grassland degradation in the TRH region was a continuous change process which had large affected area and long time scale,and rapidly strengthen phenomenon did not exist in the 1990s as a *** degradation pattern in the TRH region took shape initially in the mid and late *** the 1970s,this degradation process has taken place continuously,obviously characterizing different rules in different *** humid and semi-humid meadow region,grassland firstly fragmentized, then vegetation coverage decreased continuously,and finally＂black-soil-patch＂degraded grassland was *** in semi-arid and arid steppe region,the vegetation coverage decreased continuously,and finally desertification was *** grassland degradation had obviously regional differences in the TRH region,it could be regionalized into 7 zones, and each zone had different characteristics in type,grade,scale and time process of grassland degradation.

关键词： "Three-River Headwaters" region Qinghai grassland degradation remote sensing spatial pattern temporal process

Encapsulated carbon nanotube array as a thermal interface material compatible with standard electronics packaging

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Nano Research 2023年第8期16卷 11389-11400页

作者： Ruixiang Bai Yangbing Wei jiyuan xu Xiaobo Li Menglin Li Ziwen Zou Xinyan Huang Chengyu Liu Yiwei Sun Menglong Hao Key Laboratory of Energy Thermal conversion and control of Ministry of Education National Engineering Research Center of Power Generation Control and SafetySchool of Energy and EnvironmentSoutheast UniversityNanjing 210096China School of Materials Science and Engineering School of Energy and EnvironmentSoutheast UniversityNanjing 210096China Nanjing Research Institute of Electronics Technology Nanjing 210039China Research Centre for Fire Engineering Hong Kong Polytechnic UniversityKowloon 999077Hong KongChina State Key Laboratory of Bioelectronics School of Instrument Science and EngineeringSoutheast UniversityNanjing 210096China

Vertically aligned carbon nanotubes arrays(VACNTs)are a promising candidate for the thermal interface material(TIM)of next-generation electronic devices due to their attractive thermal and mechanical ***,the environment required for synthesizing VACNTs is harsh and severely incompatible with standard device packaging ***’extremely low in-plane thermal conductivity also limits its performance for cooling hot ***,using a transfer-and-encapsulate strategy,a two-step soldering method is developed to cap both ends of the VACNTs with copper microfoils,forming a standalone Cu-VACNTs-Cu sandwich TIM and avoiding the need to directly grow VACNTs on chip *** new TIM is fully compatible with standard packaging,with excellent flexibility and high thermal conductivities in both in-plane and through-plane *** mechanical compliance behavior and mechanism,which are critical for TIM applications,are investigated in depth using in situ *** thermal performance is further verified in an actual light emitting diode(LED)cooling experiment,demonstrating low thermal resistance,good reliability,and achieving a 17℃ temperature reduction compared with state-of-the-art commercial *** study provides a viable solution to VACNTs’longstanding problem in device integration and free-end contact resistance,bringing it much closer to application and solving the critical thermal bottleneck in next-generation electronics.

关键词： vertically aligned carbon nanotube arrays(VACNTs) sandwich structure thermal conductivity thermal interface materials(TIMs)

Research on Innovative Training of Localized STEM Teachers Grounded in Shared Commitment

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Journal of Contemporary Educational Research 2023年第12期7卷 253-257页

作者： Wei Ye jiyuan xu Education Department of Guangxi Normal University Guilin 541000Guangxi Zhuang Autonomous RegionChina

The high-quality development of a country driven by talent necessitates comprehensive and practical STEM(Science,Technology,Engineering,and Mathematics)*** goal of localizing STEM education is to cultivate comprehensive innovative technology talents that meet the needs of the new *** teachers play a core role in this concept,and the quality of teacher training directly determines the development trend of STEM education and the quality of future talents in the ***,based on the current situation and existing problems in STEM teacher training,the shared commitment to“high-quality STEM teacher training”is employed as a guiding principle,highlighting the role of various elements in the STEM teacher training *** practical path for STEM teacher training is proposed from four aspects:top-level design goal orientation,resource integration to solve supply imbalance,curriculum construction to improve the teaching system,and sustainable development to enhance professional *** study hopes to provide guidelines for innovative training of localized STEM teachers in China.

关键词： STEM teachers The theory of plural subjects Interdisciplinary education Teacher training Modernization of Chinese style education

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环路热管毛细结构的研究进展

中国电机工程学报 2013年第8期33卷 65-73,12页

作者：徐计元邹勇山东大学山东省济南市250061

环路热管是一种利用相变换热的高效传热装置,在电子元件高效散热等领域得到广泛应用。环路热管蒸发器中的多孔毛细结构是整个系统循环的重要动力来源及核心组成部分。文中综述了环路热管蒸发器多孔毛细结构近十年的研究进展,其中包括宏... 详细信息

环路热管是一种利用相变换热的高效传热装置,在电子元件高效散热等领域得到广泛应用。环路热管蒸发器中的多孔毛细结构是整个系统循环的重要动力来源及核心组成部分。文中综述了环路热管蒸发器多孔毛细结构近十年的研究进展,其中包括宏观结构(蒸汽槽道及毛细芯宏观尺寸)优化研究、微观结构优化研究以及新型材料研究,并重点讨论了双孔径毛细芯及复合结构毛细芯的研究进展。文中还对多孔毛细结构的毛细抽吸性能的表征方法进行了简要概述,为进一步优化毛细芯性能提供了理论指导。最后文章对各研究成果进行了总结并提出了未来高性能毛细芯研究的发展方向。

关键词：环路热管毛细芯毛细抽吸性能双孔径

我国学院学术委员会权力:内容构成、逻辑定位与运行机制

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湖南师范大学教育科学学报 2020年第2期19卷 28-36页

作者：徐靖徐纪元中南大学法学院湖南长沙410083

学院学术委员会是高等学校二级学院内的最高学术机构,享有学院学术事务的自主管理权。学院学术委员会的权力分为学术判断权和审议咨询权,且具有不同定位:学术判断是学院行政决策的直接依据,审议与咨询意见是学院行政决策的重要参考。性... 详细信息

学院学术委员会是高等学校二级学院内的最高学术机构,享有学院学术事务的自主管理权。学院学术委员会的权力分为学术判断权和审议咨询权,且具有不同定位:学术判断是学院行政决策的直接依据,审议与咨询意见是学院行政决策的重要参考。性质差异和定位不同决定了学院学术委员会的学术判断权和审议咨询权有着不同运行方式;与此同时,学院学术委员会权力行使需受到程序规制,以确保权力健康运行。

关键词：学院学术委员会学术判断权审议咨询权党政联席会议有限学术自治

烧结镍毛细芯的孔参数控制及其对抽吸性能的影响

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化工学报 2012年第2期63卷 463-469页

作者：徐计元邹勇程林山东大学热科学与工程研究中心山东济南250061 山东大学材料液态结构及遗传性教育部重点实验室山东济南250061

采用溶盐造孔法成功制备了孔隙率及孔径分布可控的高强度烧结镍毛细芯,分析了不同质量及粒度的溶盐对毛细性能的影响。实验结果表明:随溶盐添加量的增加,烧结镍芯孔隙率趋于线性增长,当添加量为40%(质量)时,烧结镍芯孔隙率高达73%,且有... 详细信息

采用溶盐造孔法成功制备了孔隙率及孔径分布可控的高强度烧结镍毛细芯,分析了不同质量及粒度的溶盐对毛细性能的影响。实验结果表明:随溶盐添加量的增加,烧结镍芯孔隙率趋于线性增长,当添加量为40%(质量)时,烧结镍芯孔隙率高达73%,且有足够的强度。改变溶盐的粒度影响毛细芯孔径的分布,但对整体孔隙率影响不大。所制备试样的毛细抽吸特性研究表明,毛细芯的毛细抽吸性能不仅仅受孔隙率的影响,同样受孔径分布状态的影响,孔隙率相当的情况下,孔径较小且分布集中的毛细芯表现出更优异的毛细抽吸性能。

关键词：溶盐造孔烧结毛细芯毛细抽吸性能孔径分布

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一种新的基于自适应分数阶的活动轮廓模型

计算机研究与发展 2017年第5期54卷 1045-1056页

作者：张桂梅徐继元刘建新江西省图像处理与模式识别重点实验室(南昌航空大学) 南昌330063 西华大学机械工程学院成都610039

区域可调拟合(region scalable fitting,RSF)活动轮廓模型在分割弱纹理、弱边缘图像时,优化易陷入局部极小导致曲线演化速度缓慢;同时该模型中的局部拟合项为高斯核函数,导致目标的边界模糊,影响分割精度.针对该问题,提出了一种基于自... 详细信息

区域可调拟合(region scalable fitting,RSF)活动轮廓模型在分割弱纹理、弱边缘图像时,优化易陷入局部极小导致曲线演化速度缓慢;同时该模型中的局部拟合项为高斯核函数,导致目标的边界模糊,影响分割精度.针对该问题,提出了一种基于自适应分数阶的活动轮廓模型,用于图像的分割.首先将全局G-L(Grünwald-Letnikov)分数阶梯度融合到RSF模型中,以增强灰度不均匀和弱纹理区域的梯度信息,从而提高对曲线初始位置选择的鲁棒性,并提高了图像分割的精度和速度;然后用双边滤波函数替换局部拟合项中的高斯核函数,解决了高斯核函数在演化过程中造成的边界模糊问题;最后根据图像的梯度模值和信息熵构建自适应分数阶阶次的数学模型,并计算出最佳分数阶阶次.理论分析和实验结果均表明:提出的算法可以用于灰度不均匀和弱纹理、弱边缘区域的图像分割,并能根据图像的特征自适应计算最佳分数阶阶次,避免曲线演化陷入局部最优.用多幅图像进行实验,得出该方法的分割精度和分割效率都有较大提高.

关键词： Grünwald-Letnikov分数阶自适应分数阶 RSF模型活动轮廓模型图像分割