X.F. Zhang
材料科学技术（英文）
Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations. Usually, decreasing the grain size is the only approach by which both the strength and the toughness of a steel are increased. However, low carbon bainitic steel with small grain size shows a weakening of the low temperature impact toughness in this study. By direct tracking of the morphological evolution during phase transformation, it is found that large austenite grain size dominates the nucleation of intragranular acicular ferrite, whereas small austenite grain size leads to grain boundary nucleation of bainite. This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.
关键词:
In situ observation
X.F. Zhang
材料科学技术（英文）
Plastic prestraining was applied to a solder interconnect to introduce internal defects such as dislocations in order to investigate the interaction of dislocations with electromigration damage. Above a critical prestrain, Bi interfacial segregation to the anode, a clear indication of electromigration damage in SnBi solder interconnect, was effectively prevented. Such an inhibiting effect is apparently contrary to the common notion that dislocations often act as fast diffusion paths. It is suggested that the dislocations introduced by plastic prestraining acted as sinks for vacancies in the early stage of the electromigration process, but as the vacancies accumulated at the dislocations, climb of those dislocations prompted recovery of the deformed samples under
current stressing, greatly decreasing the density of dislocation and vacancy in the solder, leading to slower diffusion of Bi atoms.
关键词:
Electromigration
X.F. Zhang
,
D.J. Wang
,
G. Xie
金属学报(英文版)
The Al/fly ash composites are fabricated by liquid reactive sintering P/M process withfly ash particles as intensifying phases. The reactivity and newly formed phases dur-ing liquid sintering process have been analyzed by combing Thermochemical data basecalculation and XRD characterization. The results show that some of constituents infly ash have reacted with liquid aluminum so that the elemental Si, Fe, Ti as well assome amount of intermetallic compounds occur. The properties of aluminum/fly ashcomposites have been improved. With the fraction of fly ash increase, the compositedensity decreases; the hardness and the modulus of the composite increases, and thecomposite wear resistance are significantly increased. The fly ash reinforced compos-ires represent a sort of low cost product with possible widespread applications in theautomotive, small engine, and electromechanical machinery sectors.
关键词:
aluminum/fly ash composite
,
null
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
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
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
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
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
