Nd-Fe-Co-Al-B永磁合金性能研究

在(Nd,Fe)(76.5)Co_(15)Al_1B_(7.5)的基础上,研究丁Nd,Fe量变化对合金性能的影响,其形式为Nd_(18-x)Fe_(58.5+x)Co_(15)Al_1B_(7.5),x=1,2,3,4,结果合金最佳性能出现在Nd量为15—16at％之间。同时研究了用W,Mo,Zr,Nb替代Al的工作,其替代式为Nd_(16)Fe_(76.5)Co_(15)B_(7.5),M_1,M为W,Mo,Zr,Nb。W替代Al的合金有较好的磁性能和热稳定性能。     

R2Fe17—XAlXNy（R=Pr,Nd）化合物的结构和磁性

研究了Al替代和渗N对二元合金R_2Fe_(17)(R=Pr,Nd)的结构和磁性的影响。X射线衍射表明所有的母合金及其氮化物都结晶为Th_2Zn_(17)型结构。Al替代Fe和渗氮都使晶胞体积增大。R_2Fe_(17-X)Al_X化合物的居里温度随x增大,但R_2Fe_(17-X)Al_X(Al_X)N_Y化合物的居里温度比纯R_2Fe_(17)N_Y化合物的居里温度要低。室温饱和磁化强度随x减小,而且R_2Fe_(17-X)Al_XN_Y化合物的易磁化方向仍在基面内。     

Mossbauer spectra and magnetic properties of amorphous (Fe_(1-x)Co_x)_(77.5)Nd_4B_(18.5) alloys

本文研究了非晶合金(Fe_(1-x)Co_x)_(77.5)Nd_4B_(18.5)(0≤X≤1.O)的~57Fe穆斯堡尔谱和磁的特性.假设Co原子磁矩保持1.21μB,则Fe原子磁矩随着含量X的增加而增加.Fe磁矩的增加与Fe的平均超精细场的增加是一致的.当Co含量在x=0.7时居里温度达最大值,在室温下,晶体化的FeCoNdB合金在Co含量较小时有高的矫顽场和能积.     

MnFe_(1-x)Z_xP_(0.77)Ge_(0.23)(Z=Co,Ni)系列化合物的结构与磁性

利用高能球磨法和粉末烧结法制备了MnFe_(1-x)Z_xP_(0.77)Ge_(0.23)(Z=Co,Ni)系列化合物,研究了样品的物相结构、磁热效应及电子状态.X射线衍射结果表明,该系列化合物均形成Fe2P型六角结构,空间群为P62m.用Co和Ni分别替代Fe,随着Co和Ni含量的增加,晶格常数a逐渐减小,c逐渐增加.磁性测量结果表明,MnFeP_(0.77)Ge_(0.23)化合物的居里温度为360K,用Co和Ni分别替代Fe后,随着Co和Ni含量的增加,化合物的居里温度、热滞和等温磁熵变均降低.FeL_3边XANES分析结果表明,用Co和Ni分别替代Fe后,Fe的+3价态减弱,Fe的+2价态增强.     

Al元素的替代对Gd_2CoSi_2居里温度和磁热效应的影响

通过电弧熔炼制备了Gd2Co Si2-xAlx(x=0,0.1,0.3)系列合金。X射线粉末衍射分析表明该系列合金的主相为具有单斜Sc2Co Si2型结构、空间群为C2/m的Gd2Co Si2相;能谱分析表明在Gd2Co Si2中Al对Si的最大替代量为4 at.%。磁性测量表明:该系列合金的居里温度及最大磁熵变随着Al替代量的增加而减小,在500 Oe外磁场下居里温度分别为226 K、205 K和196 K;在0~20 k Oe磁场变化下的最大磁熵变分别为-1.36、-1.29和-1.23 J/(kg·K)。所有合金的相变类型均为二级磁相变。     

Tm2CrFe16-xSix化合物的结构和居里温度

通过X射线衍射和磁测量手段研究Tm2CrFe16-xSix（X=0,0．5,1．0,1．5,2．0,2．5,3．0）化合物的结构和居里温度．结果表明,Tm2CrFe16-xSix化合物具有Th2Ni17型结构,随着Si替代量X的增加,Tm2CrFe16-xSix化合物的单胞体积、晶胞参数都减小．在Tm2CrFe16-xSix化合物中存在着各向异性的磁弹耦合效应．随着x的增加,Tm2CrFe16-xSix化合物的居里温度升高,在x=1．5时达到最大值,约为450K,比Tm2Fe17化合物的居里温度高出约140K,当x继续增加时,Tm2CrFe16-xSix化合物的居里温度下降．     

YBa2Cu3—xMxO7—y体系的结构和热稳定性及电子局域化

测定了系列单相样品YBa_2Cu~(3-x)M_xO_(7-y)(M=Zn,Co,Ni)的结构参数,热分解温度和电阻一温度关系。结构分析表明Zn在一定范围内有序地取代Cu,而Co和Ni的取代则是无序的。超导电性与有序取代和无序取代有很强的关联。随着x值的增加,热稳定性逐渐降低,电子局域性增加,Tc下降,四者之间存在密切的关系。作者用晶格的不稳定性解释了这一事实。     

La-Zn取代对钡铁氧体微结构和磁性能的影响

用溶胶-凝胶法(sol-gel)化学合成了钡铁氧体(Ba1-xLaxFe11.6-xZnxO19,0≤x≤0.8),并进一步研究了La-Zn取代量对样品微结构和磁性能的影响.当0≤x≤0.6时,样品主要由六角铁氧体相构成,晶格常数a和c随取代量的增加而单调减小.磁化强度σ在x=0.6时达到最大,x进一步增加σ反而下降;而样品矫顽力Hc,各向异性场HA,居里温度Tc随着x增加单调减小;为了使磁化强度达到最大,取代量大的样品需要更高的烧结温度.对实验结果进行了合理的定性解释.     

Y2Co15.24-xFexCr1.76化合物的结构和磁性（英文）

研究了Y2Co15.24-xFexCr1.76(x=2-8)化合物的结构和磁性.室温粉末X射线衍射结果表明,该系列化合物结晶为Th2Ni17型结构,晶格常数a,c和原胞体积V随铁成分增加线性增大.磁取向X射线衍射花样表明,x=2-6化合物显示单轴各向异性,而x=8化合物具有面各向异性,并且出现自旋重取向.该化合物的居里温度TC随铁成分增加而降低.该化合物的饱和磁化强度随温度升高而下降,随铁成分增加而增加.各向异性场Ba和各向异性常数K1在x=6时出现最大值.     

放电等离子烧结热变形Nd-Fe-B磁体的磁性能研究

采用放电等离子烧结技术,利用不同速率的快淬薄带制备出各向异性的热变形Nd-Fe-B磁体,运用振动样品磁强计和扫描电子显微镜对热变形磁体的磁性能和微观结构进行研究.结果表明：随着快淬薄带速率的增加,获得最佳磁性能的热变形温度也逐渐增加,三类热变形Nd-Fe-B磁体获得最佳磁性能的热变形温度分别为650,680和700°C;磁体最佳磁性能中的剩磁和最大磁能积随着快淬薄带速率的增加而降低,而内禀矫顽力却略有增加.磁体的晶粒尺寸随着热变形温度的增加而增大;相同热变形温度下,磁体的晶粒尺寸随快淬速率的增加而减小.     

Co／Al多层膜磁性的界面效应和维度效应

蒸发法制备的Ｃｏ／Ａｌ多层膜的饱和磁化强度Ｍｓ因界面效应随Ｃｏ层厚度减小而下降，并存在一个０．６８ｎｍ的磁性死层、磁性层减小时，Ｍｓ与温度关系不再满足ＢｌｏｃｈＴ＾３／２定律，Ｍｓ随温度下降更快，表现出低于三维的低维磁性特征。同时，Ｃｏ／Ａｌ多层膜的居里温度随Ｃｏ层厚度减小而减小，遵从准二维标度定律，得出居里温度维度位移因子为０．６２。     

Nd—Fe—B磁性能的改善

研究替代元素Al,Co,Dy,烧结温度和时效处理工艺对Nd-Fe-B永磁合金磁性能的影响.结果表明,合金的剩磁由基体强磁性相的成份和结构所决定.矫顽力大小与非基体相分布有关.对于一定成份的磁体,剩磁受烧结温度所制约.时效处理可显著提高矫顽力,复合添加Al,Co,Dy元素,有利于Nd-Fe-B磁体的磁性能改善.     

Ga对β基Co-Ni-Al铁磁性形状记忆合金马氏体和磁性转变的影响

借助光学金相、示差热分析、振动样品磁强计和x-射线能谱分析等分析方法，研究Ga含量对Co41Ni32-Al27-xGax合金马氏体相变和Curie点的影响。研究结果表明：合金马氏体相变温度与Ga含量成正比，在1573和1623K淬火时，X增加1，马氏体相变温度提高25K，但Ga含量对Curie点影响不大；在1573K淬火时，具有高有序度的马氏体相比B2结构相的Curie点高32K，说明结构有序度对Curie点影响较大；淬火温度升高会显著提高合金的马氏体相变温度和Curie点，当淬火温度从1573K升高到1623K时，马氏体相变温度升高43～69K，Curie点平均升高41K；随着Ga含量的增加，合金的熔点降低，在1623K淬火时Co41Ni32Al18Ga9合金发生部分熔化。     

La0.7Mg0.3Ni3.4-x(Al0.3Co0.4)0.2+x(x=0~0.3)合金电极电化学性能研究

在氩气保护下,采用悬浮熔炼法制备La0.7Mg0.3Ni3.4（Al0.3Co0.7）x（x=0,0.2,0.4,0.6）储氢合金,用X射线衍射仪测试相组成,并用MDI Jade 5.0软件分析相组成和晶胞参数,用开口三电极法测试电极电化学性能。结果表明,合金相主要由LaNi5、LaMg2Ni9、La2Ni7和LaNi2.28相组成,随着合金中Al和Co含量的增加,合金放氢平台压下降,最大吸氢量为1.43%（x=0）,合金电极最大放电容量Cmax为381mA.h.g-1（x=0）,合金电极100个充放循环后的容量保持率S100从53.0%（x=0）增加到57.1%（x=0.3）,循环稳定性增强。当x=0.1时,合金电极的电化学动力学性能较好。     

Syntheses, crystal structure and magnetic properties of Rm+nCo5m+3nB2n

The phase relations at the 600℃ and 700℃ isothermal sections of the ternary systems R-Co-B for R= Nd, Pr and R = Sm, Gd respectively were summarized in this paper. For Rm+ n Co5m+3n B2n, two new types ofcompounds R3Co13B2(R=Pr, Nd, Sm, Gd, Dy, Ho, Er, Y) (m=2, n=1) andR5Co19B6(R=Pr, Nd) (m=2,n = 3 ) were synthesized by utilizing the principle of structural combination. Their crystalstructures and easymagnetization direction were determined by X-ray powder diffraction, and structures were refined by the Rietveldmethod. The Curie temperature Tc, saturation magnetization M8 and anisotropic field HA of the new compounds weremeasured using a vibrating-sample magnetometer, an extraction sample magnetometer and M(H) - H curves of samplesin different magnetization directions respectively. The Tc and Ms of Rm + n Co5 m + 3 n B2n increase with increasing values of mat a given n value. HA increases with an increase in n when m is kept invariable. The effects of the substitution of Ni for Co on the magnetic properties of Nd13 Co15- x Nix B2 were also investigated. It was found that TsR decreased monotonously as the concentration of Ni increased, and at x = 3 the easy magnetization direction becomes axial at room temperature. The relations between crystal structure and magnetic properties of Rm + nCo5m+ 3nB2n and the possible routes of synthesizing permanent magnetic materials are also discussed.     

高磁能积低温度系数的铁基永磁合金的磁性能与组织结构

本文研究了Co和Al的添加对NdFeCoAlB永磁合金磁性能与组织结构的影响。获得一种磁能积为278.6～318.4kJ/m~3(35～40MGOe),磁感可逆温度系数α293～373K=-0.06～-0.08％/K的NdFeCoAlB系5元合金。Co主要进入四方相,提高合金的居里点,降低磁感可逆温度系数。当含Co量较高时,在合金中形成了具有MgCu_2型结构的Nd(FeCo)_2相,使合金永磁性能恶化。Al主要进入四方相,使四方相晶粒和富B相块度细化,提高了合金的矫顽力。进一步提高Al含量时,在合金中形成了新相,使合金永磁性能恶化。     

Enhancement of magnetic properties and thermal stability of nanocrystalline (NdDyTb)12.3(FeZrNbCu)81.7B6.0 alloy with Co substitution

The major drawbacks of Nd-Fe-B magnets are relatively low Curie temperature and poor thermal stability. Ribbons with the near stoichiometric 2:14:1 composition of Nd_10.8Dy_0.75Tb_0.75Fe_79.7-xCo_xZr_0.8Nb_0.8Cu_0.4B_6.0 (x=0, 3, 6, 9, 12, 15) were prepared by rapid quenching and subsequent heat treatment. The effect of Co element on the magnetic properties, thermal stability, and microstructure of the ribbons was systematically studied by vibrating sample magnetometer (VSM), thermal magnetic analysis, atomic force microscopy (AFM), and transmission electron microscopy (TEM). It was found that Co substitution was significantly effective in improving the magnetic properties and the thermal stability of nanocrystalline ribbons. Although the intrinsic coercivity decreased from 1308.7 kA/m for x=0 to 817.4 kA/m for x=15, the remanence polarization and maximum energy product increased from 0.839 T and 116.5 kJ/m3 for the Co-free samples to 1.041 T and 155.1 kJ/m3 for the 12at% Co-substituted samples, respectively. About 10 K increase in Curie temperature was observed for the 2:14:1 phase with 1at% Co substitution. The absolute values of temperature coefficients of induction and coercivity were significantly decreased with Co substitution, which may be attractive for high operational temperature applications. The microstructure of nanocrystalline ribbons was slightly refined with Co substitution.     

添加Co3O4纳米颗粒引起的残余结构应变对粉末冶金制备的Al/Co3O4纳米复合材料的结构、硬度和磁性能的影响

Al composites are of interest due to their appropriate ratio of strength to weight. In our research, an Al/Co₃O₄ nanocomposite was generated using a sintering technique. The powders of Al with various Co₃O₄ nanoparticle contents (0wt%, 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, and 2.5wt%) were first blended using planetary milling for 30 min, and compressed in a cylindrical steel mold with a diameter of 1 cm and a height of 5 cm at a pressure of 80 MPa. The samples were evaluated with X-ray diffractometry (XRD), scanning electron microscopy (SEM), Vickers hardness, and a vibrating sample magnetometer (VSM). Although the crystallite size of the Al particles remained constant at 7–10 nm, the accumulation of nanoparticles in the Al particle interspace increased the structural tensile strain from 0.0045 to 0.0063, the hardness from HV 28 to HV 52 and the magnetic saturation from 0.044 to 0.404 emu/g with an increase in Co₃O₄ nanoparticle content from 0wt% to 2.5wt%.     

Chemical states of the atoms in magnetic multilayersTa/NiOx/Ni81Fe19/Ta and Co/AlOx/Co

Ta/NiOx/Ni81Fe19/Ta and Co/AiOx/Co multilayers were prepared by rf reactive and dc magnetron sputtering. The exchange coupling field (Hex) and the coercivity (Hc)of NiOx/Ni81Fe19 as a function of the ratio of Ar to O2 during the deposition process were studied. The composition and chemical states at the interface region of NiOx/NiFe were also investigated using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that when the ratio of Ar to O2 is equal to 7 and the argon sputtering pressure is 0.57 Pa, the x value is approximately 1and the valence of nickel is +2. At this point, NiOx is antiferromagnetic NiO and the corresponding Hex is the largest.As the ratio of Ar/O2 deviates from 7, the Hex will decrease due to the presence of magnetic impurities such as Ni+3 or metallic Ni at the interface region of NiOx /NiFe, while the Hc will increase due to the metallic Ni. Al layers in Co/AIOx/Co multilayers were also studied by angle-resolved XPS. Our finding is that the bottom Co could be completely covered by depositing an Al layer about 1.8 nm. The thickness of AIOx was 1.2 nm.     

真空退火对Co/Ru多层膜磁阻性能的影响

采用超高真空电子束蒸镀的方法制备了Co/Ru金属多层膜,通过透射电镜、X射线衍射分析等结构分析仪器、磁性测试手段对薄膜的、微观与局域结构及磁性进行了研究.对Co/Ru多层膜样品进行真空退火处理,研究了退火后界面的变化及其对磁性和磁电阻性能的影响.退火增加了多层膜界面与表面的粗糙程度.Co/Ru界面处的互扩散和混合程度逐渐增大,多层膜的周期性有所降低.随着退火温度的升高,负磁阻逐渐减小,同时高场下开始出现正磁阻.