J. C. Feng
,
M. Naka
,
J. C. Schuster(School of Materials Science and Engineering
,
Harbin Institute of Technology
,
Harbin
,
150001
,
China
,
Joining and Welding Research Institute
,
Osaka University
,
Mihogaoka 11 - 1
,
Ibaraki
,
Osaka 567
,
Japan
,
Institute of Physical Chemistry
,
University of Vienna
,
Austria )
金属学报(英文版)
Bonding of SiC to SiC using Ni and Ni - 25at%Cr foils was performed at high temperature.Interface structures and reaction phases were investigated by EPMA analyses and XRD diffraction method, re- spectively. At a bonding temperature of 1273K Ni reacts with SiC and forms various Ni silicides con- taining graphite baside SiC. Ni3Si without graphite was formed at Ni side.The interface structure of SiC/Ni joint was SiC/Ni2Si + C/Ni31 Si12 + G/Ni3 Si/Ni. At the interface between SiC and Ni- 25at%Cr alloy the Ni silicide was only Ni2Si at the same bonding temperature,and further(Cr, Ni)7 (Si, C)3 carbide was formed between Ni silicide + graphite zone and Ni - 25at%Cr alloy.The interface structure of SiC/Ni - 25at%Cr alloy was SiC/Ni2Si + C/(Cr, Ni)7 (Si, C)3+Ni(ss. Cr, Si)/Ni - 25at%Cr.
关键词:
interfacial structure
,
null
,
null
,
null
Applied Physics Letters
We have succeeded in synthesizing PrFe11V1-xTix (x=0.2-1) compound and their nitrides with the ThMn12-type structure. The phase formation and magnetic properties have been investigated by x-ray diffraction, differential thermometric analysis, and magnetic measurement. The stable temperature range of the 1-12 phase for PrFe11V1-xTix alloys has been determined as a function of Ti content. PrFe11V compounds with the ThMn12-type structure do not exist and PrFe11Ti compounds with the TnMn(12)-type structure are obtained by annealing in a narrow temperature range between 1303 and 1383 K. Furthermore, 1-12 phase with the ThMn12-type structure can be obtained at lower temperature and wider temperature range with decreasing Ti content x (0.2 less than or equal to x less than or equal to 1). PrFe11V1-xTixNy with x=0.2-1 has a T-c of about 730-785 K, B-a larger than 8 T and M-s in the range 144-148 emu/g. These intrinsic magnetic properties are highly favorable for permanent magnet applications. As a preliminary, an intrinsic coercivity of 5.4 kOe is obtained for PrFe11V0.5Ti0.5Ny at room temperature by using mechanical alloying technique. (C) 1997 American Institute of Physics.
关键词:
Journal of Physics-Condensed Matter
Spin-reorientation transitions in Nd1-xPrxFe11Ti compounds have been studied by measuring the temperature dependence of the a.c. susceptibility and the magnetization. The angular dependence of the magnetization on the applied field was measured on magnetically aligned samples in a SQUID magnetometer. In NdFe11Ti, the easy magnetization direction at room temperature was determined by x-ray diffraction to be the c-axis; at low temperatures, the SQUID measurements show a cone to be stable. At temperatures between 170 and 250 K, the SQUID measurements display more complex behaviour, which is attributed to the occurrence of a first-order magnetization process in this compound. The easy magnetization direction of Nd1-xPrxFe11Ti compounds with 0.2 less than or equal to x less than or equal to 0.4 changes from easy c-axis at high temperatures via a basal plane to easy cone at low temperatures. The magnetic phase diagram of the Nd1-xPrxFe11Ti system is given. For PrFe11Ti, the critical field of the FOMP transition below 230 K, which corresponds to the critical temperature of the first-order transition, and the anisotropy fields at temperatures ranging from 240 to 300 K have been further investigated by means of the SPD technique.
关键词:
anisotropy;curve;pr;nd;tb
徐学武
腐蚀与防护
doi:10.11973/fsyfh-201507010
涠洲11-1至12-1PAP平台海管腐蚀严重,为保证管道安全可靠运行,明确管壁及焊缝的金属损失、裂纹发展情况和位置、管道结构本身的变形程度,通过调研历史维修维护数据、参考国内外管道完整性管理相关标准和规范,对内检测作业准备、几何检测和金属损失检测过程的实施和结果分析进行了全面阐述.重点分析了严重金属损失缺陷的深度、方位分布及发生机理,并提出了后续腐蚀防护与安全监管措施,以及开发多功能检测仪的建议.
关键词:
清管
,
内检测
,
腐蚀
,
金属损失
,
缺陷
Journal of Physics D-Applied Physics
The structural and magnetic properties of mixed compounds Tb1-xYxFe11Mo with x = 0-1.0 have been investigated by means of x-ray diffraction and magnetic measurements. The compounds crystallize in the tetragonal ThMn12-type structure with space group I4/mmm. The lattice parameters a, c and the unit-cell volume V vary slightly with the Y content, since the atomic radius of Y is close to that of Th. The Curie temperature of the compounds increases for x <= 0. 1, then decreases with the increase in the Y concentration. Spin reorientation phenomena in the Tb1-xYxFe11Mo compounds have been studied in detail. The room temperature easy-magnetization direction of Tb1-xYxFe11Mo compounds changes from planar to the c-axial with increasing Y concentration. Variation of the anisotropy constants of the Fe-sublattice K-1(Fe) (T) with temperature is determined experimentally. By minimizing the magnetocrystalline anisotropy energy, the derived spin reorientation temperature for the Tb1-xYxFe11Mo system shows reasonable agreement with the observations.
关键词:
intrinsic magnetic-properties;rare-earth compounds;phase-transitions;alloys;mossbauer;yfe12-xmox;diagram;series;r=y;lu
Yexin CHEN and Xaojing WAN(Institute of Materials Science
,
Shanghai University
,
Shanghai 200072
,
China)
材料科学技术（英）
The effects of hydrogen on the mechanical properties at room temperature of a Ti3Al based alloy Ti-24Al-11Nb-3V-1Mo have been investigated. The results show a parabolic rate relationship between the average hydrogen concentration of the alloy at constant temperature and charging time. The mechanical properties (ultimate bending strength and deflection) decrease with increasing hydrogen content in the alloy. The fractographic feature indicates that the decrease of the mechanical properties is due to the crack nucleation and propagation at the hydride Ti3AIH
关键词:
郑建东
,
任晓光
材料导报
采用反相微乳液-共沉淀法制备了一系列以La、Sr作为镜面阳离子、锰离子作为活性组分的六铝酸盐催化剂La1-xSrxMnAl11O19-δ(x=0.2、0.4、0.5、0.6、0.8).利用X射线衍射、比表面积分析等分析方法及甲烷燃烧对催化剂的结构和性质进行了考察,主要考察了不同含量的La和Sr离子的掺杂量对催化剂结构及对甲烷催化燃烧活性的影响.结果表明,La和Sr同时作为镜面阳离子,不但可以形成完整的六铝酸盐,而且所制备的催化剂具有较高的催化活性.不同含量的La和Sr离子掺杂对于催化剂的特性有较大影响.当x=0.5时,所制备的催化剂La0.5-Sr0.5MnAl11O19-δ具有较高的催化活性,起燃温度T10%=502℃,至683℃甲烷完全转化.催化剂在低转化率下的宏观动力学实验结果表明,甲烷催化燃烧在La1-xSrxMnAl11O9-δ催化剂上为一级动力学反应,反应速率受催化剂固有性质控制.
关键词:
六铝酸盐
,
催化燃烧
,
甲烷
,
活性
,
动力学
郑国华
,
宋小龙
,
赵阳
材料开发与应用
通过疲劳升降法对汽轮机叶片钢2Cr11Mo1NiWVNbN在100℃下的疲劳强度(107)进行测定,分别用经验公式、Basquin模型和Langer模型对测定结果进行计算和验证.结果表明:2Cr11Mo1NiWVNbN钢在100℃下的条件疲劳极限为530 MPa,大于由经验公式计算的411 MPa,这是由于M23C6析出相弥散强化及Cr和Mo元素提高了钢的淬透性所致;Langer模型对条件疲劳极限的拟合结果比Basquin模型更接近实测值,且Langer模型拟合得到的不同存活率下条件疲劳极限的分散性较小,建议在计算2Cr11Mo1NiWVNbN钢的疲劳强度时采用Langer模型.
关键词:
升降图
,
疲劳极限
,
P-S-N曲线
,
弥散强化
Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences
An ab initio method based on the density functional theory has been employed to investigate the behaviours of the bimetallic Ag(2)-doped silicon clusters at a size of n = 1-11. The possible geometrical configurations, growth-pattern behaviours, stabilities, energy gaps, and electronic properties are presented and discussed. The optimized geometries reveal that the silicon atom surface-capped and silver atom substituted 3D structures are dominant growth patterns. The calculated averaged binding energy, fragmentation energy, and the second-order difference of energy manifest that the most stable structures of Ag(2)Si(n) (n = 1-11) clusters are Ag(2)Si(2) and Ag(2)Si(5) isomers, which is in qualitative agreement with the AgSi(n) clusters. In addition, the gap between highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) exhibits that the Ag(2)Si(3) and Ag(2)Si(5) isomers have dramatically enhanced chemical stability. Natural population analysis shows that the charge-transfer phenomena are coincidence with the AgSi(n) clusters but different from Mo(2)Si(n) systems. Furthermore, the dipole moments of stable Ag(2)Si(n) (n = 1-11) display a pronounced odd-even oscillation with the number of silicon atoms.
关键词:
Ag-Si Cluster;Geometric Configuration;Density Function Method;laser-absorption spectroscopy;flight mass-spectroscopy;supersonic;molecular-beam;small silicon clusters;gold silicides;copper silicide;states;silver;ions
