Er_2Fe_(17-x)Al_x(x=2,5)化合物的中子衍射研究

利用Rietveld分析方法对Er2 Fe17-xAlx(x =2 ,5)在室温下的中子衍射实验数据进行了精修。Er2 Fe15Al2 化合物具有Th2 Ni17型六角结构 ,空间群为P6 3/mmc ,Al原子分别占据 12 j(占位数0 2 1)和 12k(占位数 0 13)位 ;Er2 Fe12 Al5化合物具有Th2 Zn17型三角结构 ,空间群为R 3m ,Al原子分别占据 18f(占位数 0 35)、18h(占位数 0 36 )和 6c(占位数 0 37)位。所有的Fe原子磁矩间为铁磁性耦合。Er原子磁矩与Fe原子磁矩间为亚铁磁耦合。在 2个样品中 ,磁矩均位于垂直于六重轴的平面内 ,呈面磁晶各向异性。给出了居里温度TC,并对磁性能和结构之间的关系进行了简单的讨论。     

Er2Fe17—xAlx（x=2,5）化合物的中子衍射研究

利用Rietveld分析方法对Er2Fe17-xAlx(x=2,5)在室温下的中子衍射数据进行了精修。Er2Fe15Al2化合物具有Th2Ni17型六角结构,空间群为P63／mmc,Al原子分别占据12j(占位数0．21）和12k(占位数0.13)位;Er2Fe12Al5化合物具有Th2Zn17型三角结构,空间群为R3m,Al原子分别占据18f(占位数0．35）、18h(占位数0．36）和6c(占位数0．37）位。所有的Fe原子磁矩间为铁磁性耦合。Er原子磁矩与Fe原子磁矩间为亚铁磁耦合。在2个样品中,磁矩均位于垂直于六重轴的平面内,呈面磁晶各向异性。给出了居里温度Tc,并对磁性能和结构之间的关系进行了简单的讨论。     

Neutron diffraction study of Er2Fe15Al2 and Er2Fe12Al5

The crystallographic and magnetic structures of Er2Fe15Al2 and Er2Fe12Al5 have been refined in Gaussian peak-shape by Rietveld analysis of Neutron diffraction data.The refined results indicated that Er2Fe15Al2 compound has Th2Ni17-type hexagonal structure (space group:P6 3/mmc) and Er2Fe12Al5 has Th2Zn17-type rhombohedral structure (space group:R3m),The Al atoms prefer 12j and 12k sites with occupancies 0.21 and 0.13 ,respectively,in Er2Fe15Al2 and prefer 18f,18h and 6c sites with occupancies 0.35,0.36 and 0.37,respectively ,in Er2Fe12Al5,The magnetic moments of all Fe atoms display ferromagnetically arrangement and the moments of Eratoms couple ferrimagnetically to the moments of the Fe atoms .The moments lie in the plane perpendicular to the six-fold axis and exhibit planar magnetic anisotropy in both samples,The values of Tc were given and the neutron refined results coincide with that of the magnetic measurements .The relation between magnetic properties and structures was discussed.     

稀土永磁材料Er_2Fe_(15)Mn_2C的中子衍射研究

用中子衍射方法研究了 2∶17型稀土铁基化合物Er2 Fe15Mn2 C的晶体结构和磁结构。研究结果表明 :Er2 Fe15Mn2 C为Th2 Ni17型六角结构 ,空间群为P63 /mmc ,居里温度TC=34 9K ,Mn原子在12k、12 j、6g和 4 f四个晶位均发生替代 ,占位数分别为 0 0 39、0 168、0 0 2 2和 0 336。室温下所有磁性原子的磁矩均位于垂直于六重轴的平面内 ,Er次晶格的磁矩方向与 (Fe ,Mn)次晶格的相反     

La1-xCaxMn0.96Fe0.04O3（x=0.31、0.5、0.6）的中子衍射研究

利用Rietveld分析方法对钙钛矿锰氧化物La_1-xCa_xMn_0.96Fe_0.04O₃（x=0.31、0.5、0.6）室温下中子衍射实验数据进行拟合。结果表明，La_1-xCa_xMn_0.96Fe_0.04O₃化合物具有MnO₆八面体，空间群为Pnma，La（Ca）原子占据4c晶位，Mn（Fe）原子占据4b晶位，O原子分别占据4c和8d晶位。根据拟合结果，计算出Mn-O键的键长和Mn-O-Mn的键角，并对该系列样品结构和磁性能间的关系进行了简单讨论。     

中子衍射研究Ho_2Fe_9Ga_2Al_6和Ho_2Fe_9Ga_6Al_2的

在中子三轴谱仪上用粉末中子衍射测定室温下Ｈｏ２Ｆｅ９Ｇａ２Ａｌ６和Ｈｏ２Ｆｅ９Ｇａ６Ａｌ２的晶体结构和磁结构，衍射数据用Ｉｚｕｍｉ的Ｒｉｅｔｖｅｌｄ分析程序ＲＩＥＴＡＮ进行轮廓精修处理，确定替代原子Ｇａ、Ａｌ的占位及占位数以及磁性原子Ｈｏ、Ｆｅ的原子磁矩的大小和方向。Ｈｏ２Ｆｅ９Ｇａ２Ａｌ６显顺磁性，Ｈｏ２Ｆｅ９Ｇａ６Ａｌ２显亚铁磁性，显单轴各向异性。并给出了居里温度和饱和磁化强度随Ｇａ、Ａｌ含量的变化关系。     

用中子衍射研究稀土-富铁永磁合金磁结构和D(H)LAP晶体结构

用粉末中子衍射测量Ｈｏ２Ｆｅ９Ｇａ８－ｘＡｌｘ（ｘ＝２,４）和ＰｒＦｅ１０．５Ｍｏ１．５Ｎｘ的晶体结构和磁结构。衍射数据分别用ＲＸｉｅｔｖｅｌｄ结构精修程序ＲＩＥＴＡＮ和Ｆｕｌｌｐｒｏｆ处理。确定了替代原子Ｇａ,Ａｌ,Ｍｏ及间隙原子Ｎ的占位数以及磁性原子Ｈｏ,Ｆｅ,Ｐｒ的原子磁矩的大小和方向。     

稀土永磁材料Ho_2Fe_9Ga_4Al_4粉末中子衍射研究

制备了稀土永磁材料Ｈｏ２Ｆｅ９Ｇａ４Ａｌ４，居里温度为１６６Ｋ。用粉末中子衍射测定３００和５０Ｋ下样品的晶体结构和磁结构，衍射数据用Ｒｉｅｔｖｅｌｄ分析程序进行轮廓精修处理，确定替代原子Ｇａ、Ａｌ的占位及磁性原子Ｈｏ、Ｆｅ的原子磁矩的大小和方向。中子衍射表明在５０Ｋ时，样品显亚铁磁性，有单轴各向异性。     

RFe10V2（R=Y,Er）的穆斯堡尔谱研究

通过对ＹＦｅ１０Ｖ２中铁晶位配位情况的详细分析，提出在具有ＴｈＭｎ１２结构的稀土－过渡金属间化合物中，铁晶位超精细场指认的一般方法。结合点电荷和有效价键模型，对ＲＦｅ１０Ｖｗ的穆斯堡尔谱进行了研究。     

用中子粉末衍射方法研究Ho2Fe17系列化合物的磁结构

在中子三轴谱仪上用中子粉末衍射方法测定了室温下样品Ａ（Ｈｏ２Ｆｅ１３Ａｌ４Ｃ）、Ｂ（Ｈｏ２Ｆｅ１３Ｇａ４Ｃ２）、Ｃ（Ｈｏ２Ｆｅ９Ｇａ４Ａｌ４）和Ｄ（Ｈｏ２Ｆｅ９Ｇａ６Ａｌ２）的晶体结构和磁结构。衍射数据用Ｉｚｕｍｉ的Ｒｉｅｔｖｅｌｄ分析程序ＲＩＥＴＡＮ进行轮廓精修处理，确定了替代原子Ｇａ、Ａｌ和间隙原子Ｃ的占位及占位数以及磁性原子Ｈｏ、Ｆｅ的原子磁矩的大小和方向。样品Ａ、Ｂ和Ｄ显亚铁磁性，Ｃ显顺磁     

用中子衍射方法分析Y_2Fe_（17－x）Si_x（X＝2）的结构

在研究稀土永磁性材料Ｙ＿２Ｆｅ（１７－ｘ）Ｓｉ＿ｘ（Ｘ＝２）的磁性时，发现用Ｓｉ取代Ｆｅ后，对提高Ｔｃ的效果很明显。中子衍射证明：Ｓｉ择优占据４ｆ晶位（哑铃位置），且Ｆｅ的磁矩平行于ｂ轴。     

用粉末中子衍射研究YFe_(10)Mo_2N_(0.75)的结构

在中子三轴谱仪上用粉末中子衍射测定室温下ＹＦｅ１０Ｍｏ２Ｎ０．７５的晶体结构和磁结构，衍射数据用ＦＵＬＬＰＲＯＦ轮廓精修程序进行处理，确定了替代原子Ｍｏ和间隙原子Ｎ的占位以及磁性原子Ｆｅ的原子磁矩。并讨论了磁结构对内禀磁性能的影响。     

AN INVESTIGATION OF THE PERMANENT MAGNETS Nd_(15)(Fe, Co)_(77)B_8 WITH Dy AND Al ADDITIVES

Nd-(Fe,Co)-B alloys with Dy and Dy-Al additives have been studied by the Mossbauer effect and X- ray diffraction. The results indicate that the alloys consist of a tetragonal phase, a B-rich phase and a Nd-rich phase. The average magnetic moment of Fe atoms in the tetragonal phase has been determined. The variation of remanence due to Dy and Dy- Al additives has been derived from the Mossbauer data and found to agree with the results of magnetic measurements. The site substitutions of Dy and Al in the alloys are also discussed.     

新型稀土永磁材料Nd_2Fe_(17-x-y)Nb_xAl_y的中子衍射分析及磁性能研究

通过X射线衍射、中子衍射及磁测量等研究了Nb、Al双取代对Nd2Fe17-x-yNbxAly化合物结构和磁性能的协同影响。X射线衍射结果表明,Nd2Fe17-x-yNbxAly的晶胞体积几乎随Al含量的增加而线性增加,当Al含量相同时,Nb的加入引起晶胞体积的增大。中子衍射分析结果表明,Nb优先占据6c晶位,Al优先占据18h晶位。磁测量结果表明,0.0≤y≤3.0时,单取代的Nd2Fe17-yAly化合物的居里温度随Al含量的增加先升高后降低,但双取代的Nd2Fe16.5-yNb0.5Aly化合物的居里温度却随Al含量的增加而线性升高,这表明Nb、Al双取代对磁性能的改善会产生协同效应。     

LaNi5－xAlxDy（x＝0.1，0.25，0.3，0.45，0.5，0.75）微观结构中子衍射研究

在室温下分别测量了一系列LaNi5－xAlx（x＝0.1,0.25,0.3,0.45,0.5,0.75）合金及其氘化物的中子衍射谱,利用FullProf程序对LaNi5－xAlx合金的衍射数据进行了精修,确定了它们的空间群为P6/mmm,得到了合金的晶胞参数、晶胞体积以及原子的占位,发现Al仅替代了部分处于3g位置的Ni,随着Al含量的增加,晶胞体积的变化量与Al替代量之间基本呈线性关系。对LaNi5－xAlxDy衍射数据的精修确定了氘化物的空间群仍为P6/mmm,分析了充氘后的相成分及晶胞参数、晶胞体积变化,得到了氘原子在晶胞中的占位和分布。     

DyxEr5－xSi3系列化合物晶体结构和磁性研究

利用电弧炉制备了DyxEr5－xSi3（x＝0,1,2,3,4,5）系列化合物样品。通过X射线粉末衍射分析和磁性测量研究了Dy替代Er对Er5Si3化合物晶体结构和磁性的影响。结果表明：DyxEr5－xSi3（x＝0,1,2,3,4,5）系列化合物的晶体结构为Mn5Si3型,随着Dy替代量的增加,晶胞体积变大。当0≤x≤2时,样品具有反铁磁性,顺磁居里温度由负值（x＝0）变为正值;而x＝3,4时,样品显现铁磁性,顺磁居里温度均为正值。虽然磁性原子及其相互作用的变化对磁性能影响很大,但所有样品的磁有序转变温度都很好地遵守了DeGennes定律。     

YFe10Mo2的粉末中子衍射研究

在中子三轴谱仪上用粉末中子衍射测定室温下ＹＦｅ１０Ｍｏ２的晶体结构和磁结构，衍射数据用ＦＵＬＬＰＲＯＦ轮廓精修程序进行处理，确定替代原子Ｍｏ的占位、占位数以及磁性原子Ｆｅ的原子磁矩的大小和方向。ＹＦｅ１０Ｍｏ２显铁磁性，为单轴各向异性。     

Micro-XRF and micro-XAFS studies of an Al matrix Fe–Ni composite

We report on the distribution and local coordination of Fe and Ni in an Al matrix Fe–Ni composite, by means of X-ray Fluorescence mapping (XRF), micro- (μ-) and conventional Extended X-ray Absorption Fine Structure (EXAFS) spectroscopies. The μ-XRF maps reveal that Fe segregates and forms Fe-rich islands which are depleted of Ni. The combined μ-EXAFS and EXAFS results reveal that both metals are bonded only to Al. More specifically, the Fe-rich islands are identified as FeAl₃ microcrystallites while in the Fe-poor regions, Fe belongs to an intermetallic FeAl phase. The bonding environment of Ni is also modified due to the variations in the distribution of the metals. In the region with high Ni concentration, i.e. Fe-poor regions, the Ni atoms are bonded to 10.5 ± 1.1 Al atoms that substitute Ni in fcc Ni. On the contrary, in the Ni-poor regions, where the Fe concentration exhibits maxima, the number of Al atoms in the first nearest shell of Ni is equal to 7.8 ± 0.9, i.e. in this region, Ni forms intermetallic NiAl. Finally, the atomic percentage of the Fe and Ni atoms that belong to the Fe-rich and Fe-poor islands is determined from the Fe-K and Ni-K edge EXAFS analysis. The majority of the Fe atoms (～80 at%) belongs to the FeAl₃ microcrystallites, embedded into a FeAl matrix. On the contrary, the same atomic percentage of Ni atoms (～50 at%), occupies sites in both the NiAl regions as well as in the matrix of the (Ni, Al) solid solution.     

Simulation of thermal stress in Er2O3 and Al2O3 tritium penetration barriers by finite-element analysis

The physical vapor deposition method is an effective way to deposit Al2O3 and Er2O3 on 316L stainless steel substrates acting as tritium permeation barriers in a fusion reactor.The distribution of residual thermal stress is calculated both in Al2O3 and Er2O3 coating systems with planar and rough substrates using finite element analysis.The parameters influencing the thermal stress in the sputter process are analyzed,such as coating and substrate properties,temperature and Young's modulus.This work shows that the thermal stress in Al2O3 and Er2O3 coating systems exhibit a linear relationship with substrate thickness,temperature and Young's modulus.However,this relationship is inversed with coating thickness.In addition,the rough substrate surface can increase the thermal stress in the process of coating deposition.The adhesive strength between the coating and the substrate is evaluated by the shear stress.Due to the higher compressive shear stress,the Al2O3 coating has a better adhesive strength with a 316L stainless steel substrate than the Er2O3 coating.Furthermore,the analysis shows that it is a useful way to improve adhesive strength with increasing interface roughness.     

Cr和Mo对Fe3Al合金中微观缺陷和电子密度的影响

测量了二元Ｆｅ３Ａｌ及含Ｃｒ或Ｍｏ的Ｆｅ３Ａｌ合金的正电子寿命谱参数,计算了合金基体和缺陷处的价电子密度。实验结果表明,Ａｌ和Ｆｅ结合形成Ｆｅ３Ａｌ合金时,Ａｌ原子提供价电子与Ｆｅ原子的３ｄ电子形成局域的共价键。Ｆｅ３Ａｌ合金中金属键和共价键共存。Ｆｅ３Ａｌ合金晶界缺陷的开空间大于Ｆｅ空位或Ａｌ空位的开空间,晶界缺陷处价电子密度比基体低,晶界的键合力较弱。在Ｆｅ３Ａｌ合金中加入Ｍｏ,降低了合金中的