Tb0.3Dy0.7Fe2合金的本构参数辨识方法研究

建立了一种简便的、适用于磁畴模型应用的Tb_0.3Dy_0.7Fe₂ 合金本构参数辨识方法. 针对Tb_0.3Dy_0.7Fe₂合金磁畴模型中本构参数不明确且直接实验测试困难的问题, 提出了一种数值计算与实验测试相结合的参数辨识方法. 采用坐标变换与绘制自由能等势曲线相结合的方法, 简化了载荷作用下Tb_0.3Dy_0.7Fe₂ 合金内磁畴角度偏转的数值计算, 研究了合金磁畴角度偏转模型的参数依赖性. 在此基础上, 结合简单的实验测试, 建立了Tb_0.3Dy_0.7Fe₂合金各向异性常数K₁ 和K₂、能量分布因子ω、晶轴取向分布的辨识及修正方法. 该方法能够简单、快速地完成Tb_0.3Dy_0.7Fe₂ 合金磁畴模型中本构参数的辨识, 对完善磁致伸缩材料磁畴偏转的数值计算模型非常有意义. 理论分析可为类磁致伸缩材料磁机耦合模型的建立、完善, 以及材料本构参数的辨识、获取提供参考.     

热处理对非晶态合金Nd4Fe96-xBx磁性的影响

本文研究了用单辊急冷方法制备的非晶态合金Nd₄Fe_96-xB_x的晶化,以及热处理对其硬磁性和相组成的影响,发现非晶态合金Nd₄Fe_96-xB_x的晶化温度比相同B含量的非晶态合金Fe_100-xB_x高120—190K,X射线衍射和热磁测量表明,15≤x≤25的样品晶化相是由Nd₂Fe₁₄B(T 关键词：     

FORMATION AND MAGNETIC PROPERTIES OF NEW COMPOUNDS R3Fe29-xCrx(R=Y,Ce,Nd,Sm,Gd,Tb,and Dy)

A systematic investigation of structure and magnetic properties of the new R₃Fe_29-xCr_x compounds(R=Y,Ce,Nd,Sm,Gd, Tb,and Dy)has been performed. The Curie temperature of R₃Fe_29-xCr_x increased with increasing atomic number fromR=Ce to Gd and de creased from Gd to Dy. The saturation magnetization of R₃Fe_29-xCr_x at 4.2 K decreased gradually with increasing atomic number from R=Y to Dy,except for Ce. The spin reorientations of the easy magnetization d irection were observed at around 230 K for Nd₃Fe_24.5Cr_4.5 and 180 K for Tb₃Fe_28.0Cr_1.0,and the magnetohistory effects were obser ved for Nd₃Fe_24.5Cr_4.5 and Sm₃Fe_24.0Cr_5.0 in a low field of about 0.04 T. First order magnetization process occurs in magnetic field of around 2.3 T at room temperature for Tb₃Fe_28.0Cr_1.0. The saturation magnetization of Y₃Fe_27.2Cr_1.8 at 4.2 K is 52.2μ_B/f.u., which corresponds to an average magnetic moment of 1.92μ_B per each Fe atom.     

电沉积Cu-In-Ga金属预制层的硒硫化研究

以H₂S气体作为硫源、固态蒸发硒蒸气作为硒源对电沉积Cu-In-Ga金属预制层进行硒硫化处理. 通过电沉积Cu-In-Ga金属预制层在不同衬底温度下硒化、硫化和硒硫化的对比实验,发现CuInS₂相和CuIn（S,Se）₂相优先生成,抑制了CuInSe₂相的生成,促使InSe相薄膜向内部扩散,减弱了薄膜两相分离现象. 采用先硒化后硒硫化处理工艺优化了Cu（In,Ga）（S,Se）₂薄膜的制备工艺,在250 ℃预硒化得到了开路电压为570 mV的太阳电池,在更高的预硒化温度得到了较大短路电流的太阳电池,最终优化得到了效率达到10.4%的电池器件. 关键词： 电化学沉积 Cu-In-Ga金属预制层 硒硫化处理 2薄膜')" href="#">Cu(In,Ga)(S,Se)₂薄膜     

基片对交替溅射制备的MnZn铁氧体薄膜结构和磁性的影响

使用成分分别为MnFe₂O₄和ZnFe₂O₄的靶,使用射频溅射交替沉积制备了成分不同的Mn_1-xZn_xFe₂O₄薄膜,沉积薄膜所用基片分别为单晶硅Si（100）,氧化的单晶硅SiO₂/Si（100）, ZnFe₂O₄为衬底的单晶硅ZnFe< 关键词： MnZn铁氧体 纳米晶 软磁性 磁性薄膜     

Ni83Cr7Fe3Si4B3非晶态合金在常压及高压下的晶化过程

本文研究了Ni₈₃Cr₇Fe₃Si₄B₃非晶态合金在1bar及100kbar压力下的晶化过程,得到了“时间-温度-变态”图。其结果表明:经高压热处理后的非晶合金其晶化温度降低,fcc-Ni相区域加宽及亚稳Ⅱ相没有形成。另外,还分别计算了常压及100kbar压力下的晶化激活能。 关键词：     

电弧炉制备的Sm2Fe17-xCrx化合物的结构与磁性

通过X射线衍射、磁测量等手段对电弧炉制备的不同热处理条件的Sm₂Fe_17-xCr_x（x=1—3）化合物的结构和磁性进行了研究.结果表明1050 ℃下退火5 d的Sm₂Fe_17-xCr_x（x=1—3）化合物具有菱方相的Th₂Zn₁₇型结构,同样温度下退 关键词： 2Fe_17-xCr_x化合物')" href="#">Sm₂Fe_17-xCr_x化合物 磁体积效应 居里温度 磁晶各向异性     

NiTi合金薄膜厚度对相变温度影响的X射线光电子能谱分析

采用X射线衍射和X射线光电子能谱实验手段对不同厚度的NiTi薄膜相变温度的变化进行了分析.结果表明在相同衬底温度和退火条件下,3?μm厚度的薄膜晶化温度高于18?μm厚度的薄膜.衬底温度越高,薄膜越易晶化,退火后薄膜奥氏体相转变温度As越低.薄膜的表面有TiO₂氧化层形成,氧化层阻止了Ni原子渗出;膜与基片的界面存在Ti₂O₃和NiO.由于表面和界面氧化层的存在,不同厚度的薄膜内层的厚度也不同,因而薄膜越薄,Ni原子的含量就越高.Ni原子的含量的不同会影响薄膜的相变温度. 关键词： NiTi合金薄膜 X射线衍射 相变 X射线光电子能谱     

R2Fe14B(R=Ce,Pr,Gd)磁晶各向异性常数K1,K2随温度的变化

本文在1.5—300K温度范围内测量了R₂Fe₁₄B(R=Ce,Pr,Gd)各向异性常数K₁,K₂和各向异性场H_A随温度的变化。同时用单离子模型计算了Pr³⁺离子对Pr₂Fe₁₄B磁晶各向异性的贡献,得到与实验值半定量符合的结果。 关键词：     

(Nd1－xGdx)3Fe27.31Ti1.69化合物的结构和磁性

通过X射线衍射和磁性测量等手段研究了(Nd_1-xGd_x)₃Fe_27.31Ti_1.69(0≤x≤0.6)化合物的结构和磁性.X射线衍射测量结果表明Gd替代后并未改变Nd₃(Fe,Ti)₂₉化合物的晶体结构，但引起了晶胞体积收缩.随着Gd含量的增加，化合物的居里温度T_C和室温磁晶各向异性场B_a单调增加，而自旋重取向 关键词： 1-xGd_x)₃Fe_27.31Ti_1.69化合物')" href="#">(Nd_1-xGd_x)₃Fe_27.31Ti_1.69化合物 磁晶各向异性 自旋重取向 磁相图     

光盘存储材料非晶GdTbFe膜的性能

用偏压磁控溅射所制备得的非晶钆铽铁膜具有适用于磁光存储的材料参数。垂直膜面磁各向异性能常数随着偏压的增加而增加,借助于Johnson-Mehl-Avrami方程和Kissinger方程的计算,报道了非晶Gd₂₇Tb₁₀Fe₆₃膜的晶化动力学参数,激活能△E=2.0电子伏,转变指数n=1。上述成份的GdTbFe膜的晶化温度、激活能都要高于二元系统的GdCo,GdFe膜,等温退火的结果表明,GdTbFe膜具有磁光存储应用所必须要求的较好的热稳定性。 关键词：     

57Fe Mössbauer study of amorphous Fe81B13.5Si3.5C2

The amorphous ferromagnet Fe₈₁B_13.5Si_3.5C₂ (Metglas^® 2605SC) has been investigated with Mössbauer spectroscopy. The hyperfine interaction parameters are studied between 80 and 300 K from which some characteristic properties are deduced. The behaviour of the amorphous alloy at higher temperatures has been studied by the room temperature spectra of annealed samples. After a structural relaxation process, a two step crystallization transformation is observed leading to Fe-Si alloy and Fe₂(B, C). X-ray diffraction of samples annealed at higher temperatures reveals the presence of an orthorhombic Fe-B-Si phase of which the structure changes slightly with annealing temperature.     

Mössbauer study of phase separation in Ni80 57Fe1P19 amorphous alloys

Mössbauer spectroscopy, X-ray diffractometry, scanning calorimetry and electrochemical measurements were used to study the crystallization process of Ni₈₀ ⁵⁷Fe₁P₁₉ amorphous alloys kept in melt at different temperatures before quenching. Samples were heated up to 430°C and 720°C at a rate of 20°C/min, in order to reach characteristically different stages of crystallization. Even at the same crystallization, stage the room temperature Mössbauer spectra and the X-ray differactograms were different depending on the temperature (1050°C or 1400°C) at which the samples were kept before quenching the melt. The Mössbauer spectra showed a paramagnetic component and two sextets (H=267 kOe and H=245 kOe) at 430°C while at 720°C there was only one sextet (H=267 kOe) besides the paramagnetic component. The changes in the Mössbauer spectra of different samples due to crystallization are consistent with the explanation that phase separation occurs in Ni₈₀ ⁵⁷Fe₁P₁₉ rapidly quenched from the melting temperature of 1050°C.     

Crystallization of Fe-B amorphous alloy powders produced by chemical reduction

The crystallization behaviour of the Fe?B amorphous alloy powders prepared by the chemical reduction method has been investigated by Mössbauer spectroscopy. In comparison to amorphous ribbons prepared by melt-spinning, a different crystallization behaviour has been observed. After annealing the amorphous samples entirely crystallized into three crystalline phases: α-Fe, Fe₃B, and Fe₂B. In the case of Fe₈₀B₂₀ amorphous alloy ribbons produced by melt-spinning technique eutectic crystallization is commonly observed and results in the crystalline phases: α-Fe and Fe₃B. This kind of crystallization was not observed in the chemically prepared samples. The metastable tetragonal Fe₃B phase transformed completely into α-Fe and Fe₂B after annealing at 973 K for one hour.     

Nanocrystallization process and ferromagnetic properties of amorphous (Fe0.99Mo0.01)78Si9B13 ribbons

The nanocrystallization process of soft ferromagnetic (Fe_0.99Mo_0.01)₇₈Si₉B₁₃ ribbons has been studied in detail. Microstructural and ferromagnetic properties are examined by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), differential scanning calorimetry (DSC) and magnetization measurements. The Curie and crystallization temperatures are determined to be T_C=665 K and T_x=750 K, respectively. The T_x value is in well agreement with DSC measurement results. XRD patterns had shown two metastable phases (Fe₂₃B₆, Fe₃B) which were formed under in situ nanocrystallization process. These metastable phases embedded in the amorphous matrix have a significant effect on magnetic ordering. The ultimate nanocrystalline (NC) phases of α-Fe(Mo, Si) and Fe₂B at optimum annealing temperature had been observed respectively. It is notable that the magnetization of the amorphous phase decreases more rapidly with increasing temperature than those of NC ferromagnetism, which suggest the presence of the distribution of exchange interaction in the amorphous phase or high metalloid contents.     

Mössbauer study of isothermally annealed amorphous Fe-Nb-Cu-Si-B alloys

Amorphous ribbons of Fe_73.5Nb₃Cu₁Si_13.5B₉ have been annealed above the crystallization temperature. Annealed samples consisted of crystalline and amorphous phases in a wide temperature range. Two samples of different thicknesses of 33 µm and 27 µm were isothermally annealed at a temperature of 545°C from 0.5 to 5 h in a vacuum furnace. The amount of crystalline phase increases rapidly in the ticker sample. The crystalline part of the Mössbauer spectrum consists of four sharp sextets which can be assigned to a DO₃-structure FeSi alloy. After 700°C annealing the amorphous phase was not observed and the crystalline phase consisted of the DO₃-structure FeSi alloy, paramagnetic FeNbB and presumably Fe₂₃B₆ and Fe₃SiB₂.     

Magnetic Behavior of Nanocrystalline FeNbCrBCu Alloys at Elevated Temperatures

The magnetic behavior of nanocrystalline Fe_73.5Nb_4.5Cr₅B₁₆Cu₁ alloys is investigated in a series of specimens with different volume fractions of crystalline phase. It is shown that the Curie temperature of amorphous phase firstly decreases after structural relaxation in amorphous state and then rapidly increases during the first stages of crystallization. The strikingly different behavior of coercivity at elevated temperatures is observed for the samples with low and high volume fractions of nanocrystalline particles.     

Surface properties of Fe76Mo8Cu1B15 alloy after annealing

NANOPERM-type alloy Fe₇₆Mo₈Cu₁B₁₅ is investigated in amorphous and in partially crystallized state. Samples were prepared by 1 h isothermal annealing in vacuum at temperatures ranging from 330°C up to 700°C. Bulk and surface microstructural characteristics were studied using transmission and conversion electron Mössbauer effect techniques, respectively. Surface features were checked by the help of atomic force microscopy. Presence of nanocrystalline bcc-Fe phase was detected during the first crystallization stage. The crystallization process starts at 450°C and it is more pronounced in surface regions than in the bulk. With progressing crystallization, hyperfine parameters especially of the amorphous residual phase are altered. Distinctions in surface morphology are revealed between wheel and air side of the ribbon-shaped samples.     

Phase segregation and crystallization in the amorphous alloy Ni70Mo10P20

Structural evolution of the amorphous alloy Ni₇₀Mo₁₀P₂₀ has been studied by x-ray diffraction, and by following transmission and high-resolution electron microscopy annealing both above and below the glass-transition temperature. When annealed above this temperature, the amorphous phase undergoes segregation into regions about 100 nm in size having different chemical composition. Diffraction from such samples produces diffuse rings, and the scattering vector corresponding to the maximum intensity varies from point to point within the interval of 4.88 to 4.78 nm⁻¹. When occurring between the glass-transition and crystallization temperatures, crystallization produces groups of nanocrystals, 20–30 nm in size, which are in direct contact with one another and form a polymorphic mechanism. The crystallization mechanism changes when the annealing temperature is brought below the glass-transition point. At these temperatures the amorphous matrix crystallizes entectically with formation of eutectic colonies. Fiz. Tverd. Tela (St. Petersburg) 40, 1577–1580 (September 1998)     

LnPO4: RE3+ (La = La, Gd; RE = Eu, Tb) nanocrystals: solvo-thermal synthesis, microstructure and photoluminescence

Through altering the solvents, we have obtained the Eu³⁺/Tb³⁺ ions-doped LnPO₄ (Ln = La, Gd) phosphors with different particle sizes, microstructures and morphologies via a facile solvo-thermal technology. X-ray powder diffraction (XRD), transmission electron microscope (TEM), and scanning electron microscope (SEM) have shown that the products using different solvents have various structures and morphologies. With the increase of DMA/water volume ratio, the microstructure has changed from hexagonal phase to monoclinic one, and the morphology from nanorod to nanoparticle, revealing the decreased oriented growth. The presence of DMA is an important factor in guiding the anisotropic growth of hexagonal lanthanide phosphates. Besides, N-methyl-2-pyrrolidone has been used as solvent to induce the Eu³⁺/Tb³⁺ ions-doped LnPO₄ (Ln = La, Gd) phosphors with different morphologies and structures. Finally, the photoluminescence behaviors of these nanocrystals have been investigated, which are dependent on their microstructures and morphologies.