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Strategy of preparing SmCo based films with high coercivity and remanence ratio achieved by temperature and chemical optimization

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Journal of Rare Earths 2024年第7期42卷 1289-1297,I0004页

作者： Yansong Gong Zhaoguo Qiu Sizhe Liang Xinrui Zheng Hongxia Meng Zhigang Zheng Deyang Chen Shengfu Yuan Weixing Xia Dechang Zeng J.P.Liu School of Materials Science and Engineering South China University of TechnologyGuangzhou510640China Zhongshan R&D Center for Materials Surface and Thin Films Technology of the South China University of Technology Gent Materials Surface Technology(Guangdong)Co.Ltd.Zhongshan528437China Institute for Advanced Materials South China Academy of Advanced OptoelectronicsSouth China Normal UniversityGuangzhou510006China Yangjiang Branch Guangdong Laboratory Materials Science and Technology Yangjiang Advanced Alloys LaboratoryYangjiang529500China Laboratory of Rare-Earth Magnetic Functional Materials Ningbo Institute of Material Technology and EngineeringChinese Academy of SciencesNingbo315201China Department of Physics University of Texas at ArlingtonArlingtonTX76019USA

SmCo based films with excellent intrinsic magnetic properties have promising applications in micro-electro-mechanical system(MEMS).However,due to the complexity of phase composition and uncontrollable crystallization degree of SmCo hard magnetic phase in the film,both the coercivity(Hc)and remanence(Mr)of films are difficult to enhance *** this paper,SmCo based films were deposited with a Cr underlayer and capping layer on single crystal Si substrates via magnetron sputtering *** effects of annealing parameters and Sm/Co atomic ratio on the phase structure and coercivity of films are *** adjusting the Sm/Co atomic ratio from 1:5 to 1:4,Co soft magnetic phase disappears and the single phase SmCo5 is obtained,leading to the increase of coercivity of the films from 30 to 34 *** influence of deposition temperature and Cu doping on magnetic properties of SmCo based films was *** the deposition temperature increases from room temperature to 250℃,the coercivity will further increase from 34 to 51 ***,a severe kink is observed in the demagnetization curves due to the poor exchanged *** analysis of transmission electron microscopy(TEM)confirms that the average size of non-hard magnetic amorphous phase exceeds the effective exchanged coupling length of SmCo5,which contributes to the decoupling and low remanence ***,doping Cu and applying a post-annealing process can significantly improve the crystallization degree of the *** the coercivity and the remanence ratio of the demagnetization curves are greatly *** propose a plausible strategy to prepare the SmCo based films with high coercivity and remanence ratio by temperature and chemical optimization,which can be utilized in high performed MEMS devices.

关键词： Rare earths SmCo based films Phase composition Crystallization conditions Coercivity Remanence ratio

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Regulation of Active Oxygen Species by Grain Boundaries to Optimize Reaction Paths toward Aerobic Oxidations

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Energy & Environmental Materials 2021年第3期4卷 444-450页

作者： Zicheng Xie Jie Zhang Yu Xiao Yangcenzi Xie Wenkun Zhu Shuyi Yu Tingting Hou Shuquan Liang Liangbing Wang State Key Laboratory for Powder Metallurgy Key Laboratory of Electronic Packing and Advanced Functional Materials of Hunan ProvinceSchool of Materials Science and EngineeringCentral South UniversityChangsha 410083China State Key Laboratory of Environment-friendly Energy Materials Southwest University of Science and TechnologyMianyang 621010China

Aerobic oxidation by using molecular oxygen(O_(2))as the oxidant is highly attractive,in which activating O_(2)to reactive oxygen species(ROS)is a *** some progress has been achieved in regulating ROS by heterogeneous catalysts,the strategies to efficiently control ROS in aerobic oxidation are still urgently ***,grain boundaries(GBs)in metal oxides are discovered to be able to facilely regulate ***,MoO_(3)nanocrystals with high density of GBs(MoO_(3)-600)deliver a mass activity of 83 mmol g^(-1)h^(-1)in aerobic oxidation of benzyl alcohol,7 and 8 times as high as that of MoO_(3)nanoparticles without GBs and Pt/C,*** addition,the selectivity of benzoic acid is 100%during whole reaction process over MoO_(3)-*** studies reveal that the oxygen atoms at GBs in MoO_(3)-600 are highly active to form·OH radicals with the generation of oxygen vacancies,while the oxygen vacancies are replenished by O_(2).The reaction path directly contributes to the excellent catalytic performance.

关键词： molybdenum oxide aerobic oxidation grain boundary reactive oxygen species benzyl alcohol

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Theoretical investigation on the stability, mechanical and thermal properties of the newly discovered MAB phase Cr4AlB4

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Journal of Materials science & technology 2020年第4期39卷 161-166页

作者： Fu-Zhi Dai Haiming Zhang Huimin Xiang Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing100076China School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing100044China

The nanolaminated MAB phases have attracted great research interests in recent years due to their similarities to MAX phases,which display both metallic and ceramic-like *** the present work,a newly discovered MAB phase Cr4AlB4 was investigated by first principles *** evaluations indicate that Cr4AlB4 can be synthetized in Al lean condition,which can further transform to Cr2AlB2 in Al rich *** full set of elastic properties and their dependences on temperature,ideal strengths under different tensile and shear deformations,and thermal expansions of Cr4AlB4 were *** results reveal that the properties of Cr4AlB4 are dominated by the layered crystal structure and weak bonding nature between Al and Cr2B2 layers,including low elastic stiffness and large thermal expansion along[010]direction(the stacking direction of Al and Cr2B2 layers),low shear resistances in(010)plane,and preferentially cleavage along and/or shear in(010)***,it suggests that Cr4AlB4 displays similar mechanical properties to MAX phases,including readily machinable,thermal shock resistant,and damage *** combination with the fact that Cr,Al and B all can form dense oxides to protect the material from further oxidation,Cr4AlB4 is regarded as a promising high temperature ceramic.

关键词： MAB phase Cr4AlB4 First-principles Mechanical properties Thermal properties

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Oxidation behaviors of(Hf_(0.25)Zr_(0.25)Ta_(0.25)Nb_(0.25))C and(Hf_(0.25)Zr_(0.25)Ta_(0.25)Nb_(0.25))C-SiC at 1300-1500℃

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Journal of Materials science & technology 2021年第1期60卷 147-155页

作者： Haoxuan Wang Shouye Wang Yejie Cao Wen Liu Yiguang Wang Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi’anShaanxi 710072PR China School of Materials Science and Engineering Zhengzhou UniversityZhengzhouHenan 450052PR China Institute of Advanced Structure Technology Beijing Institute of TechnologyHaidian District 100081BeijingPR China

In this work,high-entropy ceramics(Hf_(0.25) Zr_(0.25)Ta_(0.25)Nb_(0.25))C(HZTNC) and HZTNC doped with 20 vol%SiC(HZTNC-SiC) were fabricated by spark plasma *** oxidation behavior was investigated over the temperature range of 1300-1500℃ for up to 60 *** HZTNC and HZTNC-SiC exhibited good oxidation resistance,and their weight change as a function of oxidation time obeyed a parabolic *** XRD,microstructure observation,and elemental mapping analysis of the oxide layers,it was found that the formation of Nb_(2) Zr_(6) O_(17),Hf_(6) Ta_(2) O_(17),and(Ta,Nb)_(2) O_(5) mixed-oxide layers effectively protected the matrix from further *** began to appear on the oxide layer of HZTNC at high temperatures after 60 min of ***,the addition of SiC in HZTNC suppressed these microcracks at high temperatures due to the active oxidation of *** with the oxides formed on HZTNC,the additional formation of Hf(Zr)SiO_(4) on HZTNC-SiC could further improve its oxidation resistance over HZTNC ceramics.

关键词： High-entropy carbide Oxidation resistance Oxidation mechanism

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Controlled synthesis of silicon carbide whiskers via nickel-based alloy catalyst-assisted carbothermal reduction unraveling vapor-liquid-solid growth and Ni3Si2 droplet dynamics

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Ceramics International 2025年

作者： Chen, Chen Li, Wenhao Zhen, Qiang Li, Rong Zhang, Shaowei Li, Xingchao Wang, Jinming Materials Science and Engineering Shanghai University Shanghai200444 China Nano-Science &Technology Research Center Shanghai University Shanghai200444 China College of Engineering Mathematics and Physical Sciences University of Exeter ExeterEX4 4QF United Kingdom Science and Technology of Advanced Functional Composite Materials Laboratory Aerospace Research Institute of Materials & Processing Technology Beijing100076 China

Silicon carbide whiskers (SiCw) are highly promising for ultra-high-temperature thermal protection systems due to their excellent mechanical properties and heat resistance. However, precisely controlling their size and shape during production remains challenging. This study achieved the controllable preparation of SiC whiskers (70–280 nm in diameter, aspect ratios of 50–300) via nickel-alloy-catalyzed carbothermal reduction. The vapor-liquid-solid (V-L-S) mechanism dominated the growth, with dynamically evolving Ni-Si alloy droplets playing a critical role. Combined experimental and thermodynamic analyses confirmed that Ni3Si2 alloy droplets stabilized above 1000 °C regulated whisker growth through a dual-pathway mechanism: adsorption of CO(g), Si(g), and SiO(g) to drive axial growth while synchronously precipitating amorphous SiO2 layers to suppress radial expansion. First-principles DFT calculations revealed strong adsorption of CO and SiO on the Ni3Si2(101) surface (adsorption energies: 1.459 eV and 2.677 eV), inducing 53.8 % and 49.2 % elongations of C-O and Si-O bonds, respectively. These findings elucidate alloy catalysts' atomic-scale "adsorption-activation-nucleation" mechanism in V-L-S growth and provide critical insights for designing SiCw-reinforced thermal protection materials. © 2025 Elsevier Ltd and Techna Group S.r.l.

关键词： Aspect ratio

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Interplay of Crosslinking Structures and Segmental Dynamics in Solid-Liquid Elastomers

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Chinese Journal of Polymer science 2022年第10期40卷 1297-1306,I0012页

作者： Hao Wang Wan-Su Peng Qi Wu Yan Zhao Shi-Tai Wang Yi Yang Jin-Rong Wu Xiao-Liang Wang Rong-Chun Zhang South China Advanced Institute for Soft Matter Science and Technology(AISMST) School of Emergent Soft MatterSouth China University of TechnologyGuangzhou 510640China Key Laboratory of High-Performance Polymer Materials and Technology of Ministry of Education Department of Polymer Science and EngineeringSchool of Chemistry and Chemical EngineeringNanjing UniversityNanjing 210093China State Key Laboratory of Polymer Materials Engineering College of Polymer Science and EngineeringSichuan UniversityChengdu 610065China Suzhou Niumag Analytical Instrument Corporation Chengdu 610065China Guangdong Provincial Key Laboratory of Functional and Intelligent Hybrid Materials and Devices South China University of TechnologyGuangzhou 510640China

There have been significant interests in recent years for incorporating dynamic bonds into polymer materials for achieving multiple functionalities,such as self-healing,recycling,stimuli-responsiveness,and so ***,the impact of dynamic bonds on the polymer dynamics is actually less *** this study,we investigate a self-healing solid-liquid elastomer(SLE),which is a dual-crosslinked network made by coupling a permanently crosslinked polydimethylsiloxane(PDMS)network with polyborosiloxane(PBS)via abundant dynamic boron/oxygen dative *** double-quantum(DQ)NMR reveals that the crosslinking degree is reduced while the structural heterogeneity of network is enhanced with increasing PBS content,i.e.,increasing the content of dynamic boron/oxygen dative *** experiments clearly reveal two chain relaxation modes in the SLE samples with a characteristic relaxation time of around 2.1 s and 11.8 s,corresponding to the relaxation of coupled PBS and PDMS chains,*** master curves obtained from variable-temperature frequency-dependent rheological experiments also reveal enhanced heterogeneity of chain relaxation with increasing PBS ***,the impact of boron/oxygen dative bonds on the Rouse dynamics is further revealed by fast-field-cycling(FFC)NMR experiments,where the spinlattice relaxation rate(R_(1))of all SLE samples follows the same power law of R_(1)(ω)∝ω^(-0.33).Nevertheless,the incorporation of PBS did slightly increase the energy barrier of Rouse *** study well demonstrates a combined use of rheology and solid-state NMR spectroscopy can provide piercing insights into the interplay of crosslinking structures and dynamics of polymer materials.

关键词： Fast-field-cycling NMR Multiple-quantum NMR Rheology Dynamics Dynamic bonds

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Ru-Co-Mn trimetallic alloy nanocatalyst driving bifunctional redox electrocatalysis

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science China Materials 2022年第1期65卷 131-138页

作者： Shan Liu Erhuan Zhang Xiaodong Wan Rongrong Pan Yuemei Li Xiuming Zhang Mengyao Su Jia Liu Jiatao Zhang School of Materials Science&Engineering Beijing Key Laboratory of Construction-Tailorable Advanced Functional Materials and Green ApplicationsExperimental Center of Advanced MaterialsBeijing Institute of TechnologyBeijing 100081China

Water electrolysis is one of the most promising approaches for producing ***,it has been hindered by the sluggishness of the anodic oxygen evolution *** this work,we fabricated Ru-Co-Mn trimetallic alloy nanoparticles on N-doped carbon support(RuCoMn@NC)via the pyrolysis-adsorption-pyrolysis process using ZIF-67 as a *** RuCoMn@NC catalyst exhibited excellent electrocatalytic performance for the hydrogen evolution reaction(HER)over a wide range of pH and glucose oxidation reaction in alkaline *** showed exceptional HER activity in alkaline medium,superior to that of the commercial Pt/C catalyst(20 wt%),and good electrochemical ***,a two-electrode alkaline electrolyzer pairing RuCoMn@NC as both cathode and anode was employed,and only a cell voltage of 1.63 V was required to attain a current density of 10 mA cm^(-2)in glucose electrolysis,which is about 270 mV lower than that in the overall water-splitting *** paper provides a promising method for developing efficiently bifunctional electrocatalysts driving redox electrocatalysis,and it would be beneficial to energy-saving electrolytic H_(2) production.

关键词： Ru-Co-Mn trimetallic alloy HER glucose oxidation reaction redox electrocatalysis

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2022 roadmap on hydrogen energy from production to utilizations

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Rare Metals 2022年第10期41卷 3251-3267页

作者： Zheng-Xuan Yang Xiu-Gang Li Qi-Lu Yao Zhang-Hui Lu Ning Zhang Jun Xia Kai Yang Yu-Qing Wang Kan Zhang Hai-Zhen Liu Liu-Ting Zhang Huai-Jun Lin Qing-Jun Zhou Fang Wang Zhi-Ming Yu Jian-Min Ma School of Physics and Electronics Hunan UniversityChangsha410082China College of Material and Chemical Engineering Tongren UniversityTongren554300China Key Laboratory of Functional Small Molecules for Ministry of Education College of Chemistry and Chemical EngineeringJiangxi Normal UniversityNanchang330022China School of Materials Science and Engineering Central South UniversityChangsha410083China School of Chemistry and Chemical Engineering Jiangxi University of Science and TechnologyGanzhou341000China School of Materials Science and Engineering Nanjing University of Science and TechnologyNanjing210094China Guangxi Novel Battery Materials Research Center of Engineering Technology Guangxi Key Laboratory of Processing for Non-Ferrous Metallic and Featured MaterialsGuangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related TechnologySchool of Physical Science and TechnologyGuangxi UniversityNanning530004China School of Energy and Power Jiangsu University of Science and TechnologyZhenjiang212003China Institute of Advanced Wear and Corrosion Resistance and Functional Materials Jinan UniversityGuangzhou510632China College of Science University of Shanghai for Science and TechnologyShanghai200093China School of Materials Science and Engineering Changchun University of Science and TechnologyChangchun130022China School of Materials and Energy University of Electronic Science and Technology of ChinaChengdu611731China

Hydrogen has been always the hot topic,which drives a lot of researchers to study and explore hydrogenrelated projects and *** first subfield is hydrogen production with green and cost-effective *** methods have been intensively used for high-efficient hydrogen production,i.e.,catalytic chemical hydrogen generation,electrocatalytic hydrogen evolution,photocatalytic hydrogen evolution,photo-electrocatalytic hydrogen *** of them are driven by various ***,the hydrogen storage is also an important question,which is also a present research hot topic,although the history is long with several *** fuel cells have also obtained great attention due to the zero *** related research mainly focuses on the cell systems and electrocatalysts *** this background,we invite some excellent research groups to write this progress on hydrogen from production to ***,we believe that this roadmap on hydrogen can give some useful guidance in future research.

关键词： Hydrogen Hydrogen production Hydrogen generation Hydrogen evolution Hydrogen storage Fuel cells

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Awakening the oxygen evolution activity of MoS_(2) by oxophilic-metal induced surface reorganization engineering

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Journal of Energy Chemistry 2021年第11期30卷 546-551,I0013页

作者： Xueqin Mu Yang Zhu Xiangyao Gu Shipeng Dai Qixin Mao Lintao Bao Wenxuan Li Suli Liu Jianchun Bao Shichun Mu Jiangsu Key Laboratory of Biofunctional Materials School of Chemistry and Materials ScienceNanjing Normal UniversityNanjing 210023JiangsuChina Key Laboratory of Advanced Functional Materials of Nanjing Nanjing Xiaozhuang UniversityNanjing 211171JiangsuChina State Key Laboratory of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070HubeiChina Foshan Xianhu Laboratory of the Advanced Energy Science and Technology Guangdong Laboratory Xianhu hydrogen ValleyFoshan 528200GuangdongChina

Although molybdenum disulfide (MoS_(2))-based materials are generally known as active electrocatalysts for the hydrogen evolution reaction (HER), the inert performance for the oxygen evolution reaction (OER) seriously limits their wide applications in alkaline electrolyzers due to there exists too strong metal-sulfur (M−S) bond in MoS_(2). Herein, by means of surface reorganization engineering of bimetal Al, Co-doped MoS_(2) (devoted as AlCo_(3)-MoS_(2)) through in situ substituting partial oxidation, we successfully significantly activate the OER activity of MoS_(2), which affords a considerably low overpotential of 323 mV at −30 mA cm^(−2), far lower than those of MoS_(2), Al-MoS_(2) and Co-MoS_(2) catalysts. Essentially, the AlCo_(3)-MoS_(2) substrate produces lots of M−O (M=Al, Co and Mo) species with oxygen vacancies, which trigger the surface self-reconstruction of pre-catalysts and simultaneously boost the electrocatalytic OER activity. Moreover, benefiting from the moderate M−O species formed on the surface, the redistribution of surface electron states is induced, thus optimizing the adsorption of OH* and OOH* intermediates on metal oxyhydroxides and awakening the OER activity of MoS_(2).

关键词： Surface reorganization engineering Porous nanosheets Oxygen evolution reaction MoS_(2) Oxophilic-metal

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Coercivity enhancement mechanism of Tb-diffusion Nd-Fe-B sintered magnets studied by magneto-optical Kerr optical microscope

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Rare Metals 2021年第3期40卷 570-574页

作者： Dan Wu Wei-Qiang Liu Ming Yue Qiong Wu Dong-Tao Zhang Qing-Mei Lu Xu-Liang Li Jing-Wu Chen Key Laboratory of Advanced Functional Materials College of Materials Science and EngineeringBeijing University of TechnologyMinistry of Education of ChinaBeijing 100124China State Key Laboratory of Rare Earth Permanent Magnetic Materials Hefei 231500China

The coercivity,microstructure,and magnetic domain structure of Nd-Fe-B sintered magnets by grain boundary diffusion process(GBDP) with TbH3 nanoparticles were systematically *** to the original magnet,the coercivity(Hci) of the GBDP magnets improved from 1702 to 2374 kA·m^(-1) with few remanence reduced from 1.338 to 1.281 *** probe microanalysis(EPMA) analysis showed that Tb diffused along grain boundary,mainly concentrated in the boundary layer of the main phase,and formed a core-shell ***-optical Kerr optical microscope(MOKE) analysis showed that there were two types of magnetic domain reversal in one grain:gradual reversal(GR) and abrupt reversal(AR).When the applied field decreased from saturated magnetic field,the reversal magnetic domain nucleated and then spread over the whole grain gradually,which was called ***,some grains kept the single domain state until Hh which was a value of reverse direction applied field in second quadrant in hysteresis *** the applied field increased above Hh,reversed magnetic domain would suddenly appear and occupy most of the area of the grain,which was called *** is because AR grains have higher reversed magnetic domain nucleation field(HRN2) than GR grains(HRN1).After GBDP,the area of AR region increased obviously and GR region decreased accordingly,indicating that the core-shell structure could change GR grain into AR *** coreshell structure could suppress flipping of the magnetization of the grains due to the large magnetic anisotropy of Tbrich ***,large AR area led to high coercivity.

关键词： Coercivity enhancement mechanism Magnetic domain Grain boundary diffusion Nd-Fe-B sintered magnets

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