新型金属间化合物R_2Fe_(17)N_(2.4)的结构与磁性

本文采用适当的热处理,使氮原子进入到R_2Fe_(17)的结构中去.利用X射线衍射、磁测量和中子衍射技术研究了R_2Fe_(17)N_(24)的晶体结构和内禀磁性及其之间的联系.中子衍射研究结果表明,氮原子在Th_2Zn_(17)型菱方结构中,占据9e间隙位置.氮的加入使晶胞体积增大、Curie温度升高;使铁原子3d电子正负能带电子数目差额扩大、饱和磁矩增强;并且氮原子对稀土晶位的晶场效应有重大影响,导致Sm_2Fe_(17)N_(24)具有易磁化轴.所有这些效应使得Sm_2Fe_(17)N_(24)具备了研制高矫顽力永磁体的内禀性能.     

R2Fe17CNx的结构和磁性

采用适当的热处理,使碳原子和氮原子先后进入到R_2Fe(17)的结构中去。利用X射线折射和磁测量技术研究了R_2Fe_(17)CN_x的晶体结构和内禀磁性。碳、氮的加入使晶胞体和膨胀、居里温度升高、饱和磁矩增大,并加强了稀土晶位的轴各向异性。     

非晶态As-Se二元系短程结构的EXAFS研究

用12kW转靶X射线衍射装置测定了非晶半导体a-As₂Se₃,a-AsSe以及a-As_0.05,Se_0.95的k吸收EXAFS,a-As₂Se₃经T≤T_g(玻璃转变温度)的不同温度处理后,亦进行了测定。由获得的径向结构函数分析表明:尽管a-As₂Se₃的短程结构与晶态c-As₂Se₃十分相似,但经过低于T_g的退火处理后,其径向结构函数发生了一定的变化。熔态淬火制备的a-As₂Se₃块体亦发生结构弛豫。此外,在非晶态As-Se二元系中随As含量的变化,材料的近程结构亦不同。 关键词：     

CRYSTALLOGRAPHIC STRUCTURE AND MAGNETIC PROPERTIES OF R_(2)Fe_(17)N_(2.4)

By a proper thermal treatment, the nitrogen atoms can enter the R2Fe17 structure. The crystallographic and intrinsic magnetic properties as well as their relationship have been studied by magnetic measurements, X-ray and neutron diffraction techniques. The neutron data indicate that the nitrogen atoms occupy the interstitial sites in the Th2Zn17-type rhom-bohedral structure. The inserting nitrogen atoms are found to dilate the cell volume, increase the Curie temperature and enhance the saturation moment by raising the difference in the electron number between the spin-up and spin-down 3d subbands of the Fe atoms. Furthermore, the nitrogen atoms have an important effect on the magnetocrystallic anisotropy, which results in an easy axis with Sm2Fe17N2.4. All these make Sm2Fe17N2.4 favorable for permanent magnet applications.     

CRYSTALLOGRAPHIC STRUCTURE AND INTRINSIC MAGENTIC PROPERTIES OF R2Fe14BNx

We found that the nitrogen atoms can enter into the R₂Fe₁₄B structure by a proper heat treatment in nitrogen atmosphere. The crystallographic structure and magnetic properties of R₂Fe₁₄BN_x, R =Nd and Y, have been investigated by using X-ray and neutron diffraction techniques as well as magnetic measurements. The neutron diffrac-tion data show that the nitrogen atoms occupy the 4f interstices. The interstitial nitrogen atoms were found to have an effect of enhancing Curie temerature, whereas, decreasing saturation magnetization and magneto-crystalline anisotropy. The rela-tionship of the crystal structure and the intrinsic magnetic properties of this crystal is discussed.     

CRYSTALLOGRAPHIC STRUCTURE AND INTRINSIC MAGENTIC PROPERTIES OF R2Fe14BNx

We found that the nitrogen atoms can enter into the R₂Fe₁₄B structure by a proper heat treatment in nitrogen atmosphere. The crystallographic structure and magnetic properties of R₂Fe₁₄BN_x, R =Nd and Y, have been investigated by using X-ray and neutron diffraction techniques as well as magnetic measurements. The neutron diffrac-tion data show that the nitrogen atoms occupy the 4f interstices. The interstitial nitrogen atoms were found to have an effect of enhancing Curie temerature, whereas, decreasing saturation magnetization and magneto-crystalline anisotropy. The rela-tionship of the crystal structure and the intrinsic magnetic properties of this crystal is discussed.     

Nd(Fe,Mo)_(12)N_x磁粉的内禀磁性与永磁性能

本文在研究Nd(Fe,Mo)_(12)N_x的形成条件、结构特点和内禀磁性的基础上,制备了Nd(Fe,Mo)_(12)N_x型永磁体。采用常规球磨的方法,制成各向异性磁粉,矫顽力_iH_c可达501.7 kA/m(6.3 kOe)。研究了矫顽力与微粉颗粒度的关系。发现具有高矫顽力的微粉,对应为小于1μm的单晶颗粒。利用机械合金化工艺制成的磁粉,矫顽力_iH_c可达692.3 kA/m(8.7 kOe),并具有明显的钉扎特征。各向异性磁粉的最大磁能积为95.5 kJ/m~3(12.0 MGOe)。研究了上述两类磁粉矫顽力和剩余磁感应强度随温度的变化,并与Nd_2Fe_(14)B型磁体矫顽力的温度性能进行了对比。     

含轻元素二元合金成分的无标样X光能谱定量分析

本文对利用试样中不同元素X光强度相对比值分析成分的无标样定量分析方法提出了改进。首先对电子散射的“完全扩散”模型进行适当的修正和简化,得到标识X光的台阶状深度分布曲线,从而得到试样成分和标识X光强度的定量关系。对Cu-Si,FeS₂,NaCl和GaAs等二元合金的成分分析得到比较满意的结果。本文比较了用此法和Russ法(利用计算得到的纯元素标识X光强度因子并且经ZAF修正分析成分)得到的结果,表明用我们的方法分析的结果有所改善,计算程序也更简单。 关键词：     

纯元素厚试样的标识X射线强度比

本文在15—30kV加速电压下测定了电子激发的八种纯元素(从铝到锗)的K系X射线强度和四种纯元素(从镍到锗)的L系X射线强度。利用经过我们修正并简化的“完全扩散”电子扩散模型,计算出了这些元素的标识X射线强度比值。新模型本身包含了背散射效应,由模型给出的台阶状X射线分布函数,得出了各元素的吸收修正因子,还考虑了连续谱的荧光效应。计算值与实验值相符合,从而验证了模型的可靠性。 关键词：     

二元合金成份的无标样X光能谱定量分析

一般用电子探针对合金成份进行定量分析时都用标样进行对比。本文提出了一个不用标样的二元合金成份的定量分析方法。利用扫描电子显微镜-X光能谱分析装置同时测定二元合金(Cu-Ga,GaAs)中二元素的K_a光子数比值后,由简化的入射电子能量损失公式和X光激发截面公式并考虑了二次荧光效应后,可计算出二元合金的成份。当入射电子的过电压保持在2—3时,得到和实际成份一致的结果。利用上述简化模型对文献中不同纯元素特征X光的“仪器灵敏度”进行了计算和讨论。 关键词：