J.H.Flores
,
M.E.H.MaiadaCosta
,
M.I.PaisdaSilva
催化学报
doi:10.1016/S1872-2067(15)61032-4
采用三种不同方法制备了Cu-Zn-Al基甲醇催化剂,然后在水相悬浮液中与H型镁碱沸石混合分散,以制得负载型甲醇催化剂.运用X射线衍射、N2吸附-脱附、透射电镜、程序升温还原、NH3程序升温脱附、H2程序升温脱附和X射线光电子能谱对催化剂进行了表征.考察了催化剂催化CO加氢反应生成二甲醚和烃类的性能.该催化剂是在低和高过饱和度条件下采用共沉淀法和均匀沉淀法制得的.制备方法对前驱体的结构特性(如纯度、结晶度和催化剂颗粒粒径分布)有显著影响.低过饱和度的沉淀条件有利于Cu物种的高度分散,增加了催化剂中金属的比表面积,所得催化剂粒径分布均匀.这些效应进而会影响分子筛的性质,导致其微孔孔体积较小,分子筛酸性位被堵塞.通过Cu比表面积和CO转化速率之间的关联可考察甲醇催化剂的性能.
关键词:
甲醇合成催化剂
,
低和高过饱和度下沉淀
,
合成气
,
镁碱沸石
,
烃类
,
二甲醚
陆景彬
,
刘运祚
,
孙亮
,
杨东
,
梁国栋
,
王守宇
,
马英君
,
赵广义
,
李险峰
,
崔兴柱
,
李明非
,
霍俊德
,
曾国模
,
竺礼华
,
吴晓光
原子核物理评论
doi:10.3969/j.issn.1007-4627.2005.02.003
在稀土区奇奇核πh11/2(×)νi13/2转动带中, 系统地观测到随转动频率或角动量增加, B(M1)/B(E2)曲线表现出所谓parabola-like形状, 即在增加到某一转动频率或自旋后, B(M1)/B(E2)比值快速增强. 基于推转模型和粒子转子模型关于奇奇核二准粒子转动带磁偶极约化跃迁几率的描述, 对稀土区双奇核的这一行为进行了讨论. 指出该现象的发生与νi13/2准中子转动顺排特性密切相关. B(M1)/B(E2)比值在接近第二带交叉(即BC准中子对顺排)的较高频率处的增强效果, 可以理解为主要来源于带交叉引起的波函数中混合四准粒子成分的结果. 通过对B(M1)/B(E2)比值的增强效果发生在较低频率处的分析, 对稀土区奇奇核πh11/2(×)νi13/2带角动量耦合图像有了进一步认识.
关键词:
高自旋态
,
奇奇核
,
电磁跃迁特性
,
顺排
邸学倩
,
杨秋华
,
安宏乐
硅酸盐通报
本文综述了Sn2+或Sr2+取代的无铅或少铅钙钛矿CH3NH3PbX3 (X=Cl,Br,I)的结构及其主要的制备方法,评述了各种方法的优缺点.简要介绍了无铅或少铅钙钛矿材料的能隙以及材料的稳定性对太阳能电池的影响,并对其发展前景进行了展望.
关键词:
无铅或少铅钙钛矿
,
能隙
,
稳定性
,
太阳能电池
Zhaojun LIN
,
Zhanguo WANG
,
Wei CHEN and Lanying LIN(Lab. of Sendconductor Materials Science
,
Institute of Semiconductors
,
Chinese Academy of Sciences
,
Beijing 100083
,
China)
材料科学技术（英文）
Samples have been prepared at different temperatures by loading I2 molecules into the cages of zeolite 5A, and the measurements of the absorption spectra have been carried out for the prepared samples. It is shown that I2 molecular clusters are formed in the cages of zeolite 5A,and it is also found that moIecuIar clusters which are bonded with intermoIecuIar forces have an important feature, namely, the intermolecular distance in molecular clusters can be changed on different preparing conditions and the blue shift of absorption edges can not be as the criterion of forming molecular clusters.
关键词:
Materials Research Innovations
Polycrystalline copper (I) oxide films were deposited on stainless steel substrate by galvanostatic electrodeposition method and were characterized by Xray diffraction and scanning electron microscopy. The effect of bath temperature, bath pH and current density on the compositon, grain size, surface texture and surface morphology of the electrodeposited films were investigated. The films deposited at low bath pH (less than or equal to 7) consisted of copper (I) oxide and metallic copper; while the films deposited at bath pH between 8 and 12 and bath temperature of 60 degrees C were pure copper (I) oxide. The preferred orientation of the copper (I) oxide films depended on the relative growth rate of (111) and (200) faces and could be controlled by adjusting the bath pH and/or the cathodic current density. (100)-oriented copper (1) oxide films could be deposited at pH=9 and current densities in the range of 0.25-1 mA/cm(2) while (111)-oriented films could be prepared at pH=12 or at pH=9 using the current densities between 1.5-2.5 mA/cm(2). Computer simulated crystallite shapes showed that the crystal shape changed from octahedral for (100)-oriented film to trucated pyramids and cubs for (111)-oriented film. And they were approved by scanning electron microscopy.
关键词:
copper(I) oxide;electrochemical deposition;thin films;microstructure;electrochemical synthesis;thin-films
刘勤
,
夏锄
,
刘晓东
金属学报
在170,190,210,230,250℃的温度下,采用3.7×10~2,7.4×10~2和1.1×10~(-1)min(-1)的应变速率(平均)对Zn-5%Al共晶合金的m-C-δ(或m-k-δ)关系曲线(简称m-δ关系曲线)进行了测定.所有的曲线均随应变的δ增加而快速上升.俟达到某一定的应变量(极限应变量δ1)后。开始缓慢下降并保持平稳直至断裂.Zn-5%A1共晶合金的m-δ关系曲线不存在k_(?)=k_I(k_(I 1),k_(I 2),k_(I 3),……)=k_F(或C_0=C_I(C_(I 1),C_(I 2),C_(I 3),……)=C_F=1)的简单情况.可应用m-δ方程式[4,5]对曲线上各点C值(包括所有的C_I和C_F值)进行计算.C值随δ值的增加成近似的直线上升.直线的斜率在极限应变(δ1)处突然减小.
关键词:
Fatigue & Fracture of Engineering Materials & Structures
Nominal mode I and mixed mode I/II fatigue tests were carried out using the intermetallic compound Ni3Al(CrB) in the form of single crystal specimens. The effects of crystal orientation and load mode on fatigue crack initiation and growth were studied. The fracture surfaces of the single crystals were characterized by a cleavage-like appearance and cracking occurred either on a single {111} plane or on multiple {111} planes irrespective of whether mode I or mixed mode I/II loadings were applied. It was found that the crack initiation and growth behaviour are dependent on both crystal orientation and applied loading mode. The cracking behaviour predicted by three mixed mode fracture criteria (MTS, SED and G criteria) in polycrystalline materials under mixed mode loading can be understood from the present results on single crystals.
关键词:
fatigue cracking;mixed mode loading;crystallographic orientation;resolved shear stress;Ni3Al(CrB) single crystals;growth;alloy
Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science
Fatigue threshold under mixed-mode I and II loading and elastic plane-strain conditions has been studied in dual-phase steels (DPS) of two types of volume fraction of martensite (V(m)) in laboratory air at room temperature. Near-threshold mixed-mode (I and II) fatigue crack growth occurs mainly by two mechanisms: shear mode, and tensile mode. Particular emphasis was placed on the influence of the mode II component. The mixed-mode threshold is controlled not only by mode I displacement but also by the mode II component. Apparent- and effective-bound curves (corrected closure) are obtained for the threshold condition and discussed in terms of the shape and size of the plastic region of crack tip; crack surface rubbing; and especially, roughness-induced closure and shear resistance of crack surface that resulted in an extremely high extrinsic-toughening contribution to the mixed-mode fatigue threshold values. The ratio of the threshold value of pure mode II to that of pure mode I (DELTAK(th,II)/DELTAK(th,I) attained highly to 1.9 times; the maximum hoop direction stress-intensity factor range of pure mode II branch crack tip is 2.2 times that of pure mode I. Obviously, the resistance of pure mode II crack growth here is far larger than that of pure mode I; the former is just to introduce the shear resistance of crack surface, the latter, to reduce the driving force of crack tip for crack closure. It is proposed that the apparent- and effective-bound curves are nonconservative risky and too conservative for design purposes, respectively. So, the threshold data should be obtained under the specific conditions found by concrete mechanical, microstructural, and environmental factors.
关键词:
superposition model;mild-steel;growth;propagation;behavior;microstructures;fracture
吴崇试
,
潘奕
原子核物理评论
doi:10.3969/j.issn.1007-4627.2002.01.001
系统分析了A≈170区正常形变带[521]1/2-中的ΔI=1颤动现象. 根据旋称伙伴带的跃迁能量提取Δ2 Eγ (I)=[Eγ(I)+Eγ(I-2)]/2-Eγ(I-1)值, 表现出旋称相关的规则上下颤动. 其颤动幅度在低自旋端约为50 keV, 而后随自旋而增大或减小, 大体呈抛物线形. 利用改进的ab公式, 提取了相关的脱耦合系数. 运用Nilsson波函数, 探讨了原子核集体哈密顿量中高阶微扰项的可能形式.
关键词:
正常形变带
,
旋称伙伴带
,
ΔI = 1颤动
,
脱耦合效应
,
改进的ab拟合
