材料期刊网

EFFECT OF HOT DEFORMATION PARAMETERS ON RECRYSTALLIZATION OF STEEL T91

F. X. Zhu , C. Liu , G. Z. Chui and D. F. Gao (State Key Lab. of Rolling and Autoation , Northeastem University , Shenyang 110006 , China)

金属学报(英文版)

In this paper, the recrystallization behavior of steel 9Gr- 1Mo - V-Wb - N at high temperature was studied using Gleeble - 1500 thermalmechanical simulator.The critical conditions of occurrence of dy- namic recrystallization during hot deformation were obtained,and by means of double hit testing with an inter -hit time, the metabynamic recrystallization between rolling passes and its effect factors were also imitated.Additionally,the deformation activation energy of T91 steel,the relationship between critical stress,strain, temperature, and strain rate were regressed respectively, the results were sati- sfied.

关键词: ferritic stainless steel , null , null

Superconductivity modulated by internal pressure in Ce(1-x)Gd(x)FeAsO(0.84)F(0.16) compounds

Superconductor Science & Technology

It is shown that the superconductivity in Ce(1-x)Gd(x)FeAsO(0.84)F(0.16) compounds can be modulated by internal (chemical) pressure. The internal pressure is induced by Gd substitution for Ce in CeFeAsO(0.84)F(0.16), which compresses the crystal lattice. The temperature dependences of resistivity and magnetization show that the superconducting-transition temperature T(c) is enhanced from 40 K for CeFeAsO(0.84)F(0.16) to 47.5 K for Ce(0.6)Gd(0.4)FeAsO(0.84)F(0.16). The increase and subsequent decrease of Tc upon application of external pressure, as observed previously in LaFeAsO(0.89)F(0.11), is entirely confirmed by the modulation of Tc of the Ce(1-x)Gd(x)FeAsO(0.84)F(0.16) superconductors by internal pressure.

关键词: layered quaternary compound;43 k;iron

Structural evolution of Ce(1-x)Gd(x)FeAsO(0.84)F(0.16) superconductors

Journal of Applied Physics

Structural parameters have a critical impact on superconductivity in iron-based oxypnictide superconductors. Structural evolution study was performed on Ce(1-x)Gd(x)FeAsO(0.84)F(0.16) superconductors by the analysis of the x-ray diffraction patterns with Rietveld refinement. Substitution of Gd for Ce generates internal pressure that compresses the crystal lattice. The contraction of the c axis is also indicated by the reduction of Ce/Gd-As and Ce/Gd-O/F distances, while there is a slight increase in the As-Fe-As block size, which is compensated by a large reduction in the Ce/Gd-O/F-Ce/Gd block with Gd substitution. The diagonal Fe-As-Fe angle for Ce(0.6)Gd(0.4)FeAsO(0.84)F(0.16), with the highest T(c) among Ce(1-x)Gd(x)FeAsO(0.84)F(0.16) compounds, is 111.13 degrees. It is close to the ideal value of 109.47 degrees for the perfect FeAs tetrahedron, which is situated in the region of Fe-As-Fe bond angles where RFeAsO compounds tend to have the highest T(c). (C) 2011 American Institute of Physics. [doi:10.1063/1.3565408]

关键词: layered quaternary compound;high-temperature superconductivity

马普协会煤化所和F. Schüth教授的研究活动

陆安慧

新型炭材料 doi:10.3969/j.issn.1007-8827.2003.04.014

关键词:

GdFeAsO_(1-x)F_x超导体的制备及其超导电性

崔雅静 , 陈永亮 , 杨烨 , 王雅真 , 张勇 , 赵勇

低温物理学报

通过先制备一种纳米尺寸的GdF_3作为GdFeAsO_(1-x)F_x样品中F的反应原料,在相对较低的温度(1120℃)下成功制备出一系列GdFeAsO_(1-x)F_x(x=0,0.05,0.1,0.15,0.2,0.25)多晶样品.X射线衍射结果表明,超导样品属四方ZrCuSiAs-type结构,晶格参数随着掺F量的增加而减小.扫描电子显微镜测试结果表明,样品具有片层状晶体形貌特征.当掺F量x=0.1时,样品表现出超导电性,超导转变温度为22K,随着掺F量的增多,超导转变温度升高.和其他制备方法相比,这种制备方法更有利于F的掺入,而且可有效减少样品中杂质相的含量.

关键词: 铁基超导体 , ZrCuSiAs结构

Preparation and Superconducting Properties of F-doped SmO_1-xF_xFeAs

Zhiyong Liu

材料科学技术（英文）

Here we report the fabrication and superconductivity of the iron-based arsenic oxide SmO_1-xF_xFeAs compound. X-ray diffraction (XRD) results prove that the lattice parameters a and c decrease systematically with increasing x in between 0<x≤0.35, but when x>0.35 the a and c increase with the decrease of x in
the SmO_1-xF_xFeAs. The critical temperature (T_c) increases with increasing x in between 0.15≤x≤0.3, while x>0.3 the T_c decreases with the increase of x. It is found that at x=0.3 SmO_0.7F_0.3FeAs has the highest onset resistivity transition temperature of 55.5 K. The critical current density (J_c) value at 10 K for the obtained SmO_0.7F_0.3FeAs is 1.3×10⁵ A/cm² (0 T). Meanwhile one can estimates H_c2(0) from the slope of the H_c2(T) curve at T=T_c (H_C2 is the upper critical field), and for the 90% normal-state resistivity (ρ_n) criterion (T_c=55 K), H_c2(0) is determined to be ~253 T.

关键词: SmO_1-xF_xFeAs compound

Investigations of EPR g Factors and Rhombic Distortion for the Rhombic Cu2+ Centers in K2Zn1-x Cu (x) F-4 Crystals at Low Temperature

Applied Magnetic Resonance

The electron paramagnetic resonance g factors g (i) (i = x, y, z) of two rhombic Cu2+ centers, Cu2+(II) and Cu2+(III), in K2Zn1-x Cu (x) F-4 crystals found at low temperature are calculated from the complete diagonalization (of energy matrix) method based on the cluster approach. The calculations show that the ground state wave function of the two rhombically compressed Cu2+ centers is with a small admixture of . The rhombic distortions for both Cu2+ centers are obtained from the calculations. The results are discussed.

关键词: electron-paramagnetic-resonance;atomic screening constants;hyperfine;parameters;gyromagnetic factor;spin resonance;scf functions;field;copper(ii);dependence;spectra

适用钛不同焦距X射线照相用的KUP-T-F曝光曲线

魏惠元

稀有金属材料与工程

介绍了可适用钛金属0.4 m～1.2 m不同焦距、微粒胶片X射线照相用的KUPTF新型曝光曲线的制作原理及方法.试验结果表明,新型曝光曲线具有制作简便、经济实用、可兼顾底片象质和拍片效率的优点,是钛制压力容器现场变焦距透照选取准确管电压值的理想工具.

关键词: 钛 , X射线照相 , KUPTF , 曝光曲线

用于X射线成像板的Ba7F12Cl2:Eu2+水热合成及其表征

梁庆华 , 史瑶 , 马望京 , 杨新民 , 李智

影像科学与光化学 doi:10.7517/j.issn.1674-0475.2014.02.150

X射线成像板的成像性能很大程度上取决于存储荧光粉材料的物理化学性能.本文采用水热制备方法,以BaCl2、EuBr2、NaBF4为反应原料,以乙二胺四乙酸(EDTA)为辅助剂制备了Ba7 F12 Cl2:Eu2+荧光粉.利用X射线粉末衍射(XRD)、场发射扫描电镜(SEM)、X射线能量损失谱(EDS)、拉曼光谱(Raman)、荧光光谱(PL)等对制备的Ba7 F12 Cl2:Eu2+进行了表征.根据反应条件对产物的影响,初步提出了产物的形成过程.结果表明:反应温度及EDTA用量对产物物相和形貌有显著影响;制备的Ba7 F12 C12:Eu2+荧光粉有较好的发光性能.

关键词: 荧光粉 , 水热合成 , Ba7F12Cl2 , 成像板

Theoretical studies of g factors and defect structures for cubic, tetragonal, and orthorhombic Fe+ Centers in alkali halides MX (M = Li, Na; X = F, Cl)

Communications in Theoretical Physics

The EPR g factors for cubic, tetragonal and orthorhombic Fe+ centers in alkali halides MX (M = Li, Na; X = F, Cl) are calculated from second-order perturbation formulas of g factors based on cluster approach for 3d(7) ions in three symmetries. From calculations, the g factors of these Fe+ centers in MX crystals are reasonably explained and the defect structural data for the tetragonal and orthorhombic Fe+ centers are estimated. The results are discussed.

关键词: crystal;and ligand-field theory;electron paramagnetic resonance;defect structure;atomic screening constants;spin-orbit interaction;superposition model;resonance-spectra;epr parameters;crystal-field;scf functions;ions;co2+