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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

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烧结(Pr,Nd,Dy)_(32.2)Co_(13)Cu_(0.4)Fe_(bal)B_(0.98)磁体磁性能和微观组织的研究

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中国稀土学报 2022年第2期40卷 235-243页

作者：张家滕徐吉元胡成林孟睿阳董生智钢铁研究总院功能材料研究院北京100081 北京青云航空仪表有限公司北京102402

以烧结Nd-Fe-B磁体为基,复合添加了Cu,Co和重稀土Dy,成功制备了具有优良温度稳定性的磁体,磁体最高使用温度T_(w)≈210℃,剩磁温度系数α=-0.053%·℃^(-1)。研究发现,所制备磁体中存在着大量块状富稀土晶界相,而严重缺乏薄层富稀土晶界... 详细信息

以烧结Nd-Fe-B磁体为基,复合添加了Cu,Co和重稀土Dy,成功制备了具有优良温度稳定性的磁体,磁体最高使用温度T_(w)≈210℃,剩磁温度系数α=-0.053%·℃^(-1)。研究发现,所制备磁体中存在着大量块状富稀土晶界相,而严重缺乏薄层富稀土晶界相,即使经过二级回火,薄层富稀土晶界相数量也没有明显增加。在块状富稀土晶界相中有贫Co相和富Co相同时存在的现象。TEM观察发现在富Co相中有RE_(2)(Fe,Co)_(17)相的存在,这不利于矫顽力的提升。研究表明:晶界处Cu和Co是对立分布的,经过合理的回火工艺后,Cu在晶界的分布更为均匀,Co则主要分布在晶界角落。此外,在一级回火水淬态磁体中的富Co相区域内,发现了RE(Fe,Co)_(2)Laves相。

关键词：高温度稳定性富Co相 RE_(2)(Fe,Co)_(17)相 Cu和Co的对立分布 RE(Fe,Co)_(2)Laves相

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烧结[Y_(0.15)(Pr_(0.20)Nd_(0.80))_(0.85)]-Fe-B-M的磁性能和力学性能研究

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中国稀土学报 2022年第5期40卷 785-792页

作者：徐吉元孟睿阳张家滕陈红升董生智方以坤钢铁研究总院有限公司功能材料研究院北京100081

以成分为[Y_(0.15)(Pr_(0.20)Nd_(0.80))_(0.85)]_(31.5)Fe_(bal)B_(1.01)M_(0.72)(M=Al,Cu,Nb)的烧结磁体为主要研究对象,研究了含Y磁体的变温磁性能、力学性能及温度与反向磁场联合作用下磁体的不可逆磁通损失,并对磁体微观组织和断... 详细信息

以成分为[Y_(0.15)(Pr_(0.20)Nd_(0.80))_(0.85)]_(31.5)Fe_(bal)B_(1.01)M_(0.72)(M=Al,Cu,Nb)的烧结磁体为主要研究对象,研究了含Y磁体的变温磁性能、力学性能及温度与反向磁场联合作用下磁体的不可逆磁通损失,并对磁体微观组织和断口形貌进行了表征,同时与相同替代量下的Ce磁体进行了对比。结果表明,与Ce磁体相比,Y磁体具有更低的剩磁温度系数和更高的使用温度和抗弯强度。相同温度下,随着反向磁场的增大,会使Y磁体和Ce磁体不可逆磁损增大,最高使用温度降低。微观分析发现,Y和Ce元素在磁体中的分布具有显著差异,Y元素倾向于分布在2-14-1主相中,而Ce元素倾向于在晶界中,这可能是导致Y磁体抗弯强度得到提升的原因之一。断口形貌分析发现,Y磁体与Ce磁体和普通烧结Nd-Fe-B一样都属于脆性沿晶断裂。

关键词： Y磁体磁性能力学性能反向磁场不可逆磁损

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Excellent tribological properties of epoxy-Ti3C2 with three-dimensional nanosheets composites

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Friction 2021年第4期9卷 734-746页

作者： Fanning meng Zhenyu ZHANG Peili GAO ruiyang KANG Yash BOYJOO Jinhong YU Tingting LIU Key Laboratory for Precision and Non-Traditional Machining Technology of Ministry of Education Dalian University of TechnologyDalian 116024China Key Laboratory of Marine Materials and Related Technologies Zhejiang Key Laboratory of Marine Materials and Protective TechnologiesNingbo Institute of Materials Technology and EngineeringChinese Academy of SciencesNingbo 315201China State Key Laboratory of Catalysis Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023China

As a widely used engineering polymer,epoxy resin has been successfully employed in high-performance components and ***,the poor thermal and friction properties of traditional epoxy resin greatly limit its application in many extreme *** this work,a new kind of epoxy-Ti3C2 with three-dimensional nanosheets(3DNS)composite which was designed by freeze-drying method showed up excellent thermal and friction *** a result,the coefficient of thermal expansion(CTE)of epoxy-Ti3C23DNS 3.0 composites was 41.9 ppm/K at 40℃,which was lower than that of the traditional epoxy resin(46.7 ppm/K),and the thermal conductivity(TC)was also improved from 0.176 to 0.262 W/(m-K).Meanwhile,epoxy-Ti3C23DNS 1.0 composites showed up the best friction property,with wear rate 76.3%lower than that of epoxy *** work is significant for the research of high-performance composite materials.

关键词： epoxy-Ti3C23DNS composite three-dimensional nanosheets thermal performances friction properties

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An Experimental Study on the Gait Patterns and Kinematics of Chinese Mitten Crabs

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Journal of Bionic Engineering 2013年第3期10卷 305-315页

作者： Jianqiao Li Xiaodong Zhang meng Zou Rui Zhang Benard Chirende ruiyang Shi Cangang Wei Key Laboratory of Bionic Engineering (Ministry of Education China) Jilin University Changehun 130022 P. R. China Agricultural Research Council Institute for Agricultural Engineering Private Bag X 519 Silverton 0127 Pretoria South Africa

Despite the many studies on eight-legged animals and the importance of their mechanics of terrestrial locomotion, the mechanical energy of crabs in voluntary locomotion on uneven, unpredictable terrain surfaces has received little attention thus far. In this paper, motion video images of Chinese mitten crab （Eriocheir sinensis Milne-Edwards） locomotion on five types of terrains were recorded using a high-speed three-dimensional （3D） recording video system. The typical variables of locomotion such as gait patterns, duty factor, mechanical energy of the mass center, mass-specific write of the total mechanical power of the mass center, and percentage recovery, were analyzed. Results show that the Chinese mitten crab uses random gaits instead of the alternating tetrapod gait with the increasing terrain roughness. The duty factors of the rows of the leading legs are greater for all terrains than those of the rows of the trailing legs. On smooth terrain, the duty factors of the rows of the trailing legs are greater than that on rough terrains. Kinematic measurements and calculations reveal that similar to mammals, birds, and arthropods, the Chinese mitten crab uses two fundamental gaits to save mechanical energy： the inverted pendulum gait and the bouncing gait. The bouncing gait is the main pattern of mechanical energy conservation. The low probability of injury and energy expenditure due to adaptations to various terrains induce the Chinese mitten crab to modify the mass-specific rate of the total mechanical power of the mass center. The statistical results of percentage recovery also reveal that the Chinese mitten crab has lower energy recovery efficiency over rough terrains compared with smooth terrains.

关键词： biomechanics Chinese mitten crab gait patterns kinematics

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How Does Debt Structure Influence Stock Price Crash Risk?

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Journal of Systems Science & Complexity 2018年第2期31卷 473-492页

作者： JIA Zichao DENG Lu XU ruiyang School of Economics and Management BeiHang University

This paper uses the financial data of Chinese listed firms to explore the relationship between the debt structure, which is measured as the ratio of trade credit to bank loan, and future stock price crash risk. The empirical results show that the ratio of trade credit to bank loan is positively associated with the firm-specific crash risk while a good institutional environment reduces this positive relationship. In addition, considering the firm＇s ownership type, the authors find that the positive relationship between the debt structure and crash risk is more significant in the SOEs.

关键词： Bank loan crash risk debt structure trade credit.

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Single entity electrochemistry and the electron transfer kinetics of hydrazine oxidation

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Nano Research 2021年第11期14卷 4132-4139页

作者： ruiyang Miao Lidong Shao Richard G.Compton Department of Chemistry Physical and Theoretical Chemistry LaboratoryUniversity of OxfordSouth Parks RoadOxfordOX13QZUK Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power Shanghai University of Electric Power2103 Pingliang RoadShanghai200090China

The mechanism and kinetics of the electro-catalytic oxidation of hydrazine by graphene oxide platelets randomly decorated with palladium nanoparticles are deduced using single particle impact electrochemical measurements in buffered aqueous solutions across the pH range 2–11. Both hydrazine, N2H4, and protonated hydrazine N2H5+ are shown to be electroactive following Butler-Volmer kinetics, of which the relative contribution is strongly pH-dependent. The negligible interconversion between N2H4 and N2H5+ due to the sufficiently short timescale of the impact voltammetry, allows the analysis of the two electron transfer rates from impact signals thus reflecting the composition of the bulk solution at the pH in question. In this way the rate determining step in the oxidation of each specie is deduced to be a one electron step in which no protons are released and so likely corresponds to the initial formation of a very short-lived radical cation either in solution or adsorbed on the platelet. Overall the work establishes a generic method for the elucidation of the rate determining electron transfer in a multistep process free from any complexity imposed by preceding or following chemical reactions which occur on the timescale of conventional voltammetry.

关键词： single entity electrochemistry hydrazine electro-oxidation electro-catalysis graphene oxide palladium nanoparticles

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Physics-informed neural networks for solving time-dependent mode-resolved phonon Boltzmann transport equation

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npj Computational Materials 2023年第1期9卷 181-189页

作者： Jiahang Zhou ruiyang Li Tengfei Luo Department of Aerospace and Mechanical Engineering University of Notre DameNotre DameIN 46556USA Department of Chemical and Biomolecular Engineering University of Notre DameNotre DameIN 46556USA Center for Sustainable Energy at Notre Dame(ND Energy) University of Notre DameNotre DameIN 46556USA

The phonon Boltzmann transport equation(BTE)is a powerful tool for modeling and understanding micro-/nanoscale thermal transport in solids,where Fourier’s law can fail due to non-diffusive effect when the characteristic length/time is comparable to the phonon mean free path/relaxation ***,numerically solving phonon BTE can be computationally costly due to its high dimensionality,especially when considering mode-resolved phonon properties and time *** this work,we demonstrate the effectiveness of physics-informed neural networks(PINNs)in solving time-dependent mode-resolved phonon *** PINNs are trained by minimizing the residual of the governing equations,and boundary/initial conditions to predict phonon energy distributions,without the need for any labeled training *** results obtained using the PINN framework demonstrate excellent agreement with analytical and numerical ***,after offline training,the PINNs can be utilized for online evaluation of transient heat conduction,providing instantaneous results,such as temperature *** is worth noting that the training can be carried out in a parametric setting,allowing the trained model to predict phonon transport in arbitrary values in the parameter space,such as the characteristic *** efficient and accurate method makes it a promising tool for practical applications such as the thermal management design of microelectronics.

关键词： phonon resolved equation

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Alloying elements characterization in a Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-1Nd titanium alloy by carbon addition

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Journal of University of Science and Technology Beijing 2005年第3期12卷 252-256页

作者： ShangzhouZhang HuizhongXu ZiquanLiu HuiluLi ruiyang SchoolofEnvironmentalandMaterialsEngineering YantaiUniversityYantai264005China InstituteofMetalResearch ChineseAcademyofSciencesShenyang110016China

The effects of carbon addition (0.01wt%-0.43wt%) on a Ti-5.6Al-4.8Sn-2Zr-1Mo-0.35Si-1Nd (wt%) alloy with a bimodal microstructure were investigated. Electron probe microanalysis was carried out to examine the partitioning behavior of carbon and the relation of carbon content to the distributions of Al and Mo in the primary αp phase (α p) and β transformed structure (β). It was found that interstitial carbon is enriched in the α p phase and its content slightly reduces with the increase of the volume fraction of α p. The measurements of carbon content in the present alloy with an α p of 15vol% showed that the carbon content in the α p phase increases with the increment of carbon addition until a maximum but keeps almost constant in the β phase. The addition of carbon reduces the solubility of Al and Mo in the α p phase and leads to the increment of Mo partitioning to the β phase. When the carbon content is over 0.17wt% (0.67at%), carbide precipitation occurs in the matrix and its volume fraction is related to the volume fraction of α p which can be explained in term of the difference of carbon solubility in the α p and β phases.

关键词： high-temperature titanium alloy carbon alloying elements partitioning

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Electro-oxidation of hydrazine shows marcusian electron transfer kinetics

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Science China Chemistry 2021年第2期64卷 322-329页

作者： ruiyang Miao Lifu Chen Richard G Compton Department of Chemistry Physical and Theoretical Chemistry LaboratoryUniversity of OxfordSouth Parks RoadOxfordOX13QZUK

Although hydrazine(N2 H4) oxidation in an electrochemical environment has been of great interest for years,its intrinsic electron transfer kinetics remain *** report that the phenomenological Butler-Volmer(BV) theory is not appropriate for interpreting the process of hydrazine oxidation for which an astonishingly wide range of transfer coefficients,Tafel slopes and diffusion coefficient have been previously *** Tafel analysis for voltammetry recorded at Glassy Carbon(GC)electrodes reveals a strong potential dependence of the anodic transfer coefficient,consistent with the symmetric Marcus-Hush(sMH) *** to the relationship β=λ+FEf^0/2λ-F/2λ E,the reorganization energy(0.35±0.07 eV) and an approximate formal potential of the rate-determining first electron transfer were successfully extracted from the voltammetric responses.

关键词： hydrazine electrode kinetics transfer coefficient Butler-Volmer theory Marcus-Hush theory

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