江伟辉1
,
2
,
彭永烽1
,
刘健敏1
,
冯果1
,
谭训彦1
,
于云2
无机材料学报
doi:10.3724/SP.J.1077.2010.00532
以正硅酸乙酯和无水氯化铝为前驱体, 乙醚为氧供体, 采用非水解溶胶凝胶法制备了直径为0.2~20μm, 长径比高达60~70的莫来石晶须. 借助XRD、SEM和TEM等测试手段研究了莫来石干凝胶粉的活性、矿化剂氟化铝引入方式及其用量、成型压力以及煅烧温度等工艺参数对合成莫来石晶须的影响. 结果表明：采用恒压回流工艺制备的莫来石干凝胶粉, 在12MPa压力下压制成片状, 以外置方式引入3wt%的氟化铝, 在1200℃保温1h可制备质量较好的莫来石晶须.
关键词:
非水解溶胶-凝胶法
,
mullite
,
whisker
,
aspect ratio
Z.M.Yu
金属学报(英文版)
The surface free energy (SFE) of (1× 1)-surfaces of crystals, without reconstructionand adsorption, is calculated using a bond-broken mode. In the mode, the potentialenergy of the crystals is treated as a sum of the energies of the bonds connectingpair-wise atoms (u-bonds). The SFE is calculated based on the bond energy and thearea density of dangling bonds which depends on the structure of the surface. Theresults provide a general expression for the SFE in terms of the bond energy (E)and the bond length (do) of the crystal and Miller indices hkl. The anisotropy ofthe SFE is therefore completely determined with the expression. As the examples,considering the nearest-neighboring bonding, the SFEs of sc, fcc, bcc and cth (cubictetrahedral) crystals are discussed, respectively. Wulff plots of bcc and fcc crystalsare then obtained. The equilibrium forms (EFs) of these crystals ave consequentlygot from their Wulff plots, respectively. It is found that the EFs of bcc and fcc arerespectively the rhombic dodecahedron and the truncated-octahedron that are their firstBrillouin zones, respectively.
关键词:
surface free energy
,
null
,
null
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
谢慕华
,
丁志福
,
李瑞
材料导报
采用高温固相法合成Li1-xNb1-xW1+xO6 (x=0.1,0,-0.1),通过H+交换制备出相应的固体酸H1-x-Nb1-xW1+xO6.采用XRD和FT-IR技术表征固体酸的物相和层板骨架结构,NH3-TPD方法表征其酸性特征.结果表明,3种酸样品的物相相同,但它们的主晶面(002)面间距略有变化.与HNbWO6中的NbO6和WO6八面体结构单元相比,H0.9Nb0.9 W1.1O6和H1.1 Nb1.1 W0.9 O6中的NbO6和WO6八面体发生变形.3种酸样品均有两种不同强度的酸位,它们的弱酸位强度基本相等,强酸位强度大小顺序为HL1 Nb1.1W0.9O6 ＞H0.9 Nb0.9 W1.1 O6＞ HNbWO6,两种酸位的酸量大小顺序均为H1.1 Nb1.1 W0.9 O6＞ HNbWO6＞ H0.9Nb0.9W1.1O6.
关键词:
层状化合物
,
铌钨酸
,
结构
,
酸性
张昌
,
段远源
,
史琳
,
朱明善
,
韩礼钟
工程热物理学报
析了气相声速与理想气体比定压热容的热力学关系，用超声变程干涉仪测定了1,1,1,2,3,3,3-七氟丙烷(HFC-227ea)的72组气相声速值，温度范围273-333 K，压力范围26-315 kPa，测量不确定度小于0.05%。根据这些实验数据，确定了HFC-227ea的理想气体比定压热容和声速第二维里系数，并分别拟合得到了与温度的函数，理想气体比定压热容的不确定度小于0.5%。使用方阱势能模型导出了HFC-227ea的第二维里系数，并与文献值进行了比较。
关键词:
HFC-227ea
,
声速
,
理想气体比定压热容
,
第二维里系数
赵学国
,
罗民华
人工晶体学报
以SrCO3,Sm12 O3,Al2O3,TiO2为原料,采用固相反应法制备了Sr1+xSm1-xAl1-xTixO4(x=0,0.1,0.2,0.3)陶瓷,研究了SrTiO3掺人量对其显微结构和微波介电性能的影响.结果表明:SrSmAlO4晶相中固溶SrTiO3,晶胞出现了明显的膨胀；SrSmAlO4陶瓷中固溶SrTiO3相,可降低其烧结温度和陶瓷烧结体的密度；SrSmAlO4陶瓷中固溶SrTiO3相后,可提高其介电常数和品质因素,但对其温频系数影响较小.在1420C/2 h烧结条件下,Sr1.2Sm0.8Al08Ti0 2 O4陶瓷微波介电性能达到:εr=28,Q×f=52600 GHz,τf=4 ppm/℃.
关键词:
微波介质陶瓷
,
SrSmAlO4陶瓷
,
烧结温度
,
介电性能
Acta Materialia
This work reveals the formation mechanisms of saturation dislocation patterns in three typical multiple-slip oriented [0 0 1], [0 1 1] and [(1) over bar 1 1] copper single crystals. Compared with the single-slip oriented copper single crystals, the three multiple-slip oriented ones show very different dislocation patterns. It was found that the dislocation patterns in cyclically saturated copper single crystals are the Labyrinth structure for [0 0 1], wall structure for [0 1 1] and cell structure for [(1) over bar 1 1] , respectively. Based on a two-phase structure consisting of persistent slip bands and veins for single-slip orientation, the formation mechanisms of the dislocation patterns in multiple-slip oriented crystals are proposed as follows: the formation of the complex dislocation patterns depends on the activating slip system. The easy operation of the critical secondary slip system will contribute to the formation of the Labyrinth structure. The activation of the coplanar secondary slip system will be beneficial to formation of the cell structure. If no secondary slip system is activated, the wall structure is more prone to appear. Finally, the intrinsic relationship between various dislocation patterns and face centered cubic crystal structure was established. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
Orientation effect;Cyclic deformation;Copper single crystals;Dislocation patterns;electron channeling contrast;persistent slip bands;stress-strain;response;low-amplitude fatigue;deformation-behavior;grain-boundaries;orientation;surface;localization;arrangements
Guoqing LI
,
Lijie HAO
,
Ze XIANYU
,
Deren LI
,
Ke SUN
,
Halving LI
材料科学技术（英）
Perovskite-like bulk La1/3Nd1/3Ca1/3MnO3 is prepared by solid phase reaction method. The temperature dependence of the magnetization and the relationship between CMR effect and sintering have been studied. The CMR is up to 673.9% under 1 T applied magnetic field and 100 K temperature, and that also reaches 93.5% in 0.2 T and 100 K.
关键词:
