X-RAY POWDER DIFFRACTION DATA AND STRUCTURAL REFINEMENT OF Er_3Co_6Sn_5

１ＩＮＴＲＯＤＵＣＴＩＯＮＲａｒｅｍｅｔａｌｓａｎｄｔｈｅｉｒｃｏｍｐｏｕｎｄｓｈａｖｅｏｕｔｓｔａｎｄｉｎｇｐｒｏｐｅｒｔｉｅｓａｎｄａｒｅｐａｉｄｉｎｃｒｅａｓｉｎｇａｔｅｎｔｉｏｎｔｏ．Ｎｕｍｅｒｏｕｓｉｎｖｅｓｔｉｇａｔｉｏｎｓｉｎｔｈｅ...     

Crystal structure and Rietveld refinement of the new ternary compound Al14Nd5Si

The new ternary compound Al14Nd5Si has been studied by means of the X-ray powder diffraction technique and the Rietveld method. The ternary compound Al14Nd5Si has a hexagonal Ni3Sn-type structure with space group P63/mmc (No.194), the lattice parameters are a = 0.64470 (2) nm and c = 0.45926 (1) nm. The Smith and Snyder figure of merit for the index, FN, is F30 = 97.8 (30). The X-ray diffraction data indicated that the crystal structure of the compound Al14Nd5Si has been successfully refined by the Rietveld method. The R-factors of Riet- veld refinement are Rp = 0.088 and Rwp = 0.120, respectively. The thermal dependence of magnetization for the compound was measured by a vibrating sample magnetometer. The experimentally determined magnetic effective paramagnetic moment is μeff = 3.60 μB per Nd atom. The paramagnetic Currie temperature θp = -33.7 K was also obtained from the Currie-Weiss law.     

Crystal structural refinement for NdAlSi

The compound NdAlSi was studied using X-ray powder diffraction technique and refined by the Rietveld method. The compound NdAlSi has tetragonal α-ThSiE-type structure, space group I41/amd （No. 141）, Z = 4, and the lattice parameters a = 0.41991（1） nm, c = 1.44916（3） nm. The Smith and Snyder figure of merit FN is F30= 103.1（36）. The R-factors of Rietveld refinement are Rp= 0.113 and Rwp= 0.148, respectively. The X-ray powder diffraction data is presented in this article.     

W的添加对MoSi2显微组织的影响

以Mo、W、Si粉为原料,采用机械活化结合热压烧结的方法制备了不同W含量的MoSi2合金试样.结果表明,合金元素W加入后,其主要物相为MoSi2、(Mo,W)Si2固溶体及少量Mo4.8Si3C0.6碳化物,引起MoSi2显微应变增大,晶粒尺寸减小,从而细化了晶粒,晶粒尺寸在59.7～78.6 nm之间,具有纳米晶结构,强化了基体;随着W含量的增多,MoSi2合金材料的晶格参数和晶格体积增大,晶格密度减小.     

Si元素含量对激光快速成形制备Nb-Si二元合金显微组织演变的影响

以铌粉和硅粉为原料,采用双通道同轴送粉制备了四种不同Si元素含量的Nb-Si二元合金,通过扫描电镜（SEM）、能谱仪（EDS）及X射线衍射仪（XRD）等分析了合金的显微组织演变及维氏硬度.结果表明,硅含量由7%增加至25%,合金的显微组织由Nb_SS+Nb₃Si转变为初生Nb_SS+（Nb_SS/Nb₃Si）共晶,硅含量为18%时,呈Nb_SS/Nb₃Si全共晶组织,硅含量提高至25%,合金中出现初生β-Nb₅Si₃相,并仍存在Nb_SS/Nb₃Si共晶组织.铌和硅粉末在激光作用下原位反应并快速凝固,显著细化了Nb-Si合金的显微组织.随硅含量增加,硅化物含量逐渐增加,合金显微硬度由746 HV增至1 342 HV.     

Structural investigation of ternary RIr3B2 compounds (R=Ce and Pr)

Structural studies were performed for the ternary RIr₃B₂ compounds (R=Ce and Pr) from as cast samples. The crystal structure of the ternary boride CeIr₃B₂ (CeCo₃B₂ structure type, space group P6/mmm, a=5.520(3) Å, c=3.066(2) Å, Z=1, V=80.91 ų, ρ_x=15.154 g cm⁻³) was refined to R₁=0.0470, wR₂=0.1240 from single-crystal X-ray diffraction data. The new ternary boride PrIr₃B₂ was found to be isostructural with the CeIr₃B₂ compound. Its lattice parameters a=5.5105(2) Å, c=3.1031(1) Å were obtained from a Rietveld refinement of X-ray powder diffraction data.     

STRUCTURAL AND MAGNETIC PROPERTIES OF ( PrxSm1 - x ) Mn2Si2

１ＩＮＴＲＯＤＵＣＴＩＯＮＴｅｒｎａｒｙｌａｙｅｒｅｄｉｎｔｅｒｍｅｔａｌｉｃｃｏｍｐｏｕｎｄｓＲＭｎ２Ｘ２（Ｒ＝ｒａｒｅｅａｒｔｈａｎｄＸ＝Ｓｉ,Ｇｅ）ｈａｖｅｂｅｃｏｍｅｏｆｒｅｎｅｗｅｄｉｎｔｅｒｅｓｔｒｅｃｅｎｔｌｙｂｅｃａｕｓｅｏｆｔｈｅｌ...     

Molten glass corrosion resistance of new. Mo‐Ru‐Si compounds

In spite of a very promising potential for a large field of high temperature applications, MoSi₂ shows only a limited resistance against molten glass corrosion. Efforts to improve the performance of MoSi₂‐based materials led to the investigation of the Mo‐Ru‐Si phase diagram. The isothermal section at 1673 K revealed five new intermetallics with original structures. The crystallographic study of two of them was made using standard and synchrotron X‐ray measurements combined with KKR (Korringa‐Kohn‐Rostoker) calculations. The use of such total energy electronic structure calculations was helpful in order to localize accurately Mo and Ru in the new compound β‐Mo₂₆Ru₄₇Si₂₇. This compound crystallizes in P4/mmm space group with a = 9.2164(1) Å, c = 2.88721(1) Å, Dx = 9.69(1) g/cm³. The structure has been refined by the Rietveld method down to R_p = 1.1%, R_B = 12.0 %, R_F = 8.7% for 6814 observed data and 271 independent reflections. Moreover, electrochemical techniques enabled the determination of the redox properties of the new intermetallic compounds. It has been shown that, in contact with molten glass at 1623 K, Mo‐Ru‐Si compounds were subjected to electrochemical reactions leading to the simultaneous oxidation of silicon and molybdenum. The progressive superficial depletion of Si and Mo resulted in the more or less rapid formation of a thick, porous and low adherent Ru‐layer. Consequently, the results showed that Ru‐additions had no positive effect on the molten glass corrosion resistance of MoSi₂‐based materials. The formation of a porous Ru‐layer should even accelerate the degradation kinetics through galvanic coupling occurring between the superficial layer and the bulk material.     

A new high-pressure polymorph of NiSb2

A new polymorph of NiSb₂ was obtained under high-pressure/temperature condition of 6 GPa and 550–650°C. The crystal structure is orthorhombic with the space group Pbca (No. 61), isostructural with the low-temperature form of NiAs₂ (pararammelsbergite). The crystallographic parameters were refined by the Rietveld analysis of the powder X-ray diffraction data (a=0.62866(2) nm, b=0.63643(2) nm, c=1.23670(3) nm, Z=8). The structure can be regarded as an intermediate structure between the marcasite-type and the pyrite-type. The pararammelsbergite-type NiSb₂ is a high-pressure form of NiSb₂ and the density is slightly higher than that of ambient pressure form with the marcasite-type structure.     

Structure and magnetic properties of intermetallic compounds Gd5Si2-xGe2-xM2x

1 Introduction Nowadays, there is much interest in magnetic refrigeration materials, as they offer the prospect of an energy-efficient and environment friendly alternative for the traditional vapour cycle refrigeration technique. Magnetic refrigeration is…     

LiC0O2电极材料晶体结构的XRD和TEM研究

报道了X射线衍射和电子衍射在研究锂离子正极材料LiC0O2晶体结构中的作用。测定了不同温度下合成的LiC0O2以及脱锂态产物LixC0O2（0〈x〈1）的晶体结构。X射线衍射反映了LiC0O2粉末颗粒晶体结构的统计性集体特征，电子衍射反映了LiC0O2单颗粒的精细晶体结构特征，2种方法结合起来才能较为全面地考察LiC0O2粉末颗粒的晶体结构，从而为采取综合措施提高其电化学性能提供依据。     

Study on syntheses and structures of nine-coordinated mononuclear K[TbⅢ(edta)(H2O)3]·5H2O and binuclear K4[TbⅢ2(Httha)2]·14H2O complexes

The crystal and molecular structures of the K[TbⅢ(edta)(H2O)3]-5H2O (edta = ethylenediaminetetraacetic acid) and K4[TbⅢ2(Httha)2]+14H2O (ttha = triethylenetetraminehexaacetic acid) complexes have been determined by sin-gle-crystal X-ray diffraction analyses. The crystal of the K[TbⅢ(edta)(H2O)3]·5H2O complex belongs to orthorhombic crys-tal system and Fdd2 space group. The crystal data are as follows: a = 1.9373(5) nm, b = 3.5429(10) nm, c = 1.2114(3) nm, V = 8.315(4) nm3, Z= 16, M = 630.35, Dc = 2.014 g cn-3, m = 3.683 mm-1 and F(000) = 5024. The final R and wR values are 0.0224 and 0.0557 for 3189 [I> 2.0o(I)] unique reflections, and 0.0245 and 0.0567 for all 8206 reflections, respectively. The [TbⅢ(edta)(H2O)3]- complex anion has a nine-coordinated pseudo-monocapped square antiprismatic structure in which the nine coordinate atoms, two N and seven O come from one edta ligand and three water molecules. The crystal of the K4[TbⅢ2(Httha)2]·14H2O complex belongs to monoclinic system and P2(1)/n sp     

Al2O3-CeO2-ZrO2-Ni复合球磨粉末的热稳定性研究

采用高能球磨法制备Al2O3-CeO2-ZrO2-Ni复合粉末,并模拟催化剂的工作环境对球磨粉末进行焙烧。运用XRD研究了球磨粉体的组织结构,测定其耐热性能。结果表明,经30h球磨的复合粉体中Al2O3,CeO2和ZrO2均明显细化,而Ni较难磨细。该球磨粉体在600℃低温下的热稳定性良好。若温度不超过1000℃短时焙烧,粉末基本保持活性相,但温度一旦高达1100℃,则完全变成无活性相。     

Structure refinement of nonstoichiometric TiS2 (Ti1.083S2)

The structure of high temperature growth Ti_1.083S₂ has been refined carefully from single crystal X-ray data. Deviations from the ideal 1T-Ti_1+xS₂ structure model are very small. However, the possibility of a slight lengthening of the Ti-Ti distance cannot be ruled out. The good accuracy obtained in this study (R = 0.016) indicates that the structure of low-xTi₁₊S₂ materials should be re-examined.     

X-ray investigations of ternary R3Pd4Ge4 samples

Ternary R₃Pd₄Ge₄ samples (R=Nd, Eu, Er) were investigated by means of X-ray single crystal (four circle diffractometer Philips PW1100, MoK radiation) and powder diffraction (MX Labo diffractometer, CuK radiation). The Er₃Pd_3.68(1)Ge₄ compound belongs to the Gd₃Cu₄Ge₄ structure type, space group Immm, a=4.220(2) Å, b=6.843(2) Å, c=14.078(3) Å, R₁=0.0484 for 598 reflections with F_o>4σ(F_o) from X-ray single crystal diffraction data. No ternary R₃Pd₄Ge₄ compound when R is Nd or Eu was observed. The Nd and Eu containing samples appeared to be multiphase. Ternary phases observed in the Nd₃Pd₄Ge₄ and Eu₃Pd₄Ge₄ alloys and their crystallographic characteristics are the following: NdPd₂Ge₂, CeGa₂Al₂ structure type, space group I4/mmm, a=4.3010(2) Å, c=10.0633(2) Å (X-ray powder diffraction data); NdPd_0.6Ge_1.4, AlB₂ structure type, space group P6/mmm, a=4.2305(2) Å, c=4.1723(2) Å (X-ray powder diffraction data); Nd(Pd_0.464(1)Ge_0.536(1))₂, KHg₂ structure type, space group Imma, a=4.469(2) Å, b=7.214(2) Å, c=7.651(3) Å, R₁=0.0402 for 189 reflections with F_o>4σ(F_o) (X-ray single crystal diffraction data); Eu(Pd,Ge)₂, AlB₂ structure type, space group P6/mmm, a=4.311(2) Å, c=4.235(2) Å; EuPdGe, EuNiGe structure type, space group P2₁/c, and ternary compound with unknown structure (X-ray powder diffraction data).     

Crystal structure and thermoelectric properties of β-MoSi2

A powder sample of a metastable phase β-MoSi₂ having the C40-type crystal structure was prepared by heating Mo sheets with a Na–Si melt at 858 K for 12 h to determine details of the crystal structure. The lattice constants (a = 4.6016(3) Å and c = 6.5700(3) Å) and Si atom coordinate (y = 0.1658(2)) of β-MoSi₂ were determined by Rietveld analysis of the X-ray powder diffraction. The thermoelectric properties were refined for a bulk sample prepared by sintering the β-MoSi₂ powder at 773 K and 600 MPa. The electrical resistivity of the sintered β-MoSi₂ sample with a relative density of 65% of the theoretical one was 2.5 mΩ cm at 300 K, and slightly increased with increasing temperature from 300 to 725 K. The Seebeck coefficients changed from +60 to +89 μV/K in the temperature range from 330 to 725 K. The maximum thermoelectric power factor was 2.2 × 10^?6 W cm^?1 K^?2 at 725 K.     

铸态Mg-Sn-Si-Sr合金的显微组织与力学性能

采用X射线衍射仪(XRD)、扫描电镜(SEM)和光学显微镜(OM)分别研究Mg-5Sn-xSi-0.5Sr(x=1,2)和Mg-5Sn-ySi-2Sr(y=1,2)合金的相组成和显微组织,采用力学性能试验机测定合金的拉伸性能。结果表明:Mg-Sn-Si-Sr系合金组织由α-Mg、MgSnSr、Mg2Sn、Mg2Si相所组成。Mg2Si相含量随Si元素的增加而增加,加入Sr元素会促进MgSnSr相的形成,抑制相界上Mg2Sn相的析出。Sn和Sr均能够细化Mg2Si相。当Sr含量由0.5%提高到2%(质量分数)后Mg2Si和Mg2Sn相均能得到显著细化,从而显著提高合金的抗拉强度与屈服强度。     

采用铝灰和粉煤灰合成Sialon粉

以铝灰、粉煤灰和碳黑为主要原料,采用碳热铝热复合还原氮化工艺制备了Sialon粉体.研究了原料组成(Si/Al比分别为1.5、1和0.27)、碳黑含量(分别为10%、17%、22%和27%)以及合成反应温度(分别为1400, 1450, 1500 ℃)对生成物相的影响.结果表明,合成温度为1450 ℃,可以得到较纯的物相;随着还原剂碳黑含量的增加,使还原氮化反应进行的更为充分;在原料中Si/Al比为1时,加入17%的碳黑可以得到主要物相为Si_3Al_3O_3N_55(β-Sialon,z=3)和SiAl_4O_2N_4(15R)的产物;在原料中Si/Al比为1.5时,即加入80%的粉煤灰,在1450 ℃可以制备较纯的Si_3Al_3O_3N_5粉.     

Crystal structure and Rietveld refinement of the new ternary compound Al14Nd5Si

The new ternary compound Al₁₄Nd₅Si has been studied by means of the X-ray powder diffraction technique and the Rietveld method. The ternary compound Al₁₄Nd₅Si has a hexagonal Ni₃Sn-type structure with space group P6₃/mmc (No.194), the lattice parameters are a = 0.64470 (2) nm and c = 0.45926 (1) nm. The Smith and Snyder figure of merit for the index, F_N, is F₃₀ = 97.8 (30). The X-ray diffraction data indicated that the crystal structure of the compound Al₁₄Nd₅Si has been successfully refined by the Rietveld method. The R-factors of Rietveld refinement are R_p = 0.088 and R_wp = 0.120, respectively. The thermal dependence of magnetization for the compound was measured by a vibrating sample magnetometer. The experimentally determined magnetic effective paramagnetic moment is μ_eff = 3.60 μ_B per Nd atom. The paramagnetic Currie temperature θ_p = −33.7 K was also obtained from the Currie-Weiss law.     

Cr_3C_2粉体的高能球磨细化

采用高能球磨工艺对Cr3C2粉末进行研磨。研究了粉体粒度随球磨时间的变化。结果表明:随着球磨时间的增加,粉体粒度不断细化,最后BET粒度趋于稳定在50nm左右。Cr3C2粉末高能球磨细化机理是:机械力通过破碎一次颗粒间的烧结颈,并不断细化粉末,Cr3C2粉末的最终粒度取决于一次颗粒的晶粒尺寸;长时间球磨不能进一步细化粉末反而容易形成新的团聚体。