材料期刊网

Alabaster and Selenite Gypsum: I-Dehydration-Rehydration Comparison Studies

El-Sayed I.Al-Wakeel , null

材料科学技术（英文）

Two types of gypsum raw materials, selenite and alabaster, were used to prepare dental stone (α-hemihydrate). Gypsum lumps (0.8~2.5 cm) were hydrothermally treated at 135, 160 and 180°C for 6, 2 and 1 h respectively. The physicochemical properties and composition characteristics of the α-hemihydrates prepared from selenite and alabaster raw gypsum were determined. The results indicated that both the selenite and alabaster raw gypsum show the same chemical and mineralogical composition of calcium sulphate dihydrate. They differs only in their microstructure, selenite raw gypsum exhibits perfect regular crystals while alabaster gypsum, on the other hand, exhibits irregular, large size and interlocked crystals. Selenite is more accessible to dehydration than alabaster raw gypsum. The α-hemihydrate samples prepared from alabaster raw gypsum showed a very short setting time and a lower compressive strength values in relation to that prepared from selenite gypsum. The compressive strength values of the all prepared samples were higher than that specified by A.D.A specification for dental use. To optimize the setting time of both products further studies are needed.

关键词: Selenite , null , null , null

Mode I and mixed mode I/II fatigue cracking in Ni3Al(CrB) single crystals

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

V对γ-Fe-Mn与γ-Fe-Mn-Al合金的Néel温度及电阻率的影响

朱乃平 , 张彦生

材料研究学报

<正> 1 引言γ-Fe-Mn 合金与Cr 均系典型的巡游电子能隙型反铁磁性物质。出于反铁磁性理论研究及发展反铁磁新功能合金的需要,较系统地研究过Al、Si、Cr 及Mn 对γ-Fe-Mn 基合金顺磁-反铁磁性转变及电阻率反常行为的影响。Al、Si 为非过渡族元素,Mn、Cr 为反铁磁性元素,如进一步研究周期表中位于Mn、Fe 左侧的3d 电子未满顺磁性元素V 的影响是有一定意义的,但迄今尚未见报道。

关键词: Fe-Mn 合金 , resistivity , antiferromagnetic transformation

有机EL和LED与无机EL和LED发光机制的异同

李文连

液晶与显示 doi:10.3969/j.issn.1007-2780.2001.01.007

比较了有机EL和LED与无机EL和LED的主要差异。有机EL属于电注入发光，无机EL属于高场激发下的碰撞离化机制，而且有机LED和无机LED的激发和发光机制也不同。无机半导体中往往存在着局域载流子，而有机LED必须从电极注入，在未注入载流子之前，它们是绝缘体。不能简单地用无机LED中的p-n结理论来解释有机LED的发光现象。

关键词: 有机电致发光 , 半导体 , 发光

电子束蒸发Al2O3/TiO2复合膜及在无机EL中的应用

黄浩 , 肖田 , 张羿 , 林明通

液晶与显示 doi:10.3969/j.issn.1007-2780.2006.05.014

开发高可靠性的绝缘层薄膜几十年来一直是TFEL显示器研制中的重要努力方向之一.采用双靶脉冲电子束蒸发法制备了Al2O3/TiO2单元结构为10 nm/10 nm、20 nm/20 nm、40 nm/40 nm、总厚度约600 nm的多层复合薄膜,同时采用共蒸发法制备了800 nm的AlxTiyOz复合薄膜,研究了它们的介电性能,并与Al2O3、TiO2单层膜的介电性能做了比较,最后将性能较优的AlxTiyOz薄膜应用到ZnS:Mn TFEL器件中.Al2O3/TiO2多层复合膜随着结构单元中Al2O3、TiO2厚度由10 nm增至40 nm,介电常数由20.2减小到16.1,击穿场强由154 MV/m增至174 MV/m,反映介电损耗的参数ΔVy由0.09 V降为0.04 V,在50 MV/m下漏电流密度由1×10-6 A/cm2增至1×10-4 A/cm2,品质因子由2.62 μC/cm2降为2.46 μC/cm2.AlxTiyOz薄膜的品质因子大于3.6 μC/cm2,应用于ZnS:Mn TFEL器件中获得在200 Hz下较高的L50(58 cd·m-2)、很低的阈值电压(60～70 V),而且各个像素的L-V性能有很好的重复性.

关键词: 电子束蒸发 , Al2O3-TiO2复合膜 , 介电性能 , ZnS:Mn器件

有机EL与无机EL和LCD的比较及其未来前景

李文连

液晶与显示 doi:10.3969/j.issn.1007-2780.2002.01.005

通过比较有机EL与无机EL、LCD在平板显示应用方面的差异,展示了OELD的美好应用前景.由于无机薄膜EL缺乏高亮度蓝基色成分以及驱动电压是100V左右的交流,难于制成低压彩色超薄显示器;无机分散型EL屏采用的是十几微米厚的粉末材料,也难于制成高分辨率超薄显示器,因此它们都无法与OELD相比.OELD显示器体积可以是LCD的1/2,功耗也大大低于LCD,所以OELD将有望取代LCD.评述了当前OELD的最新发展趋势:采用荧光染料掺杂式的模糊界面结构的电致荧光器件和采用荧光染料掺杂式的电致磷光器件是当前OELD发展的主要潮流.文中还评述了采用低折射率材料提高外量子效率的情况.

关键词: 电致发光 , 磷光 , 发光平板显示

用于有机EL器件的电极材料

李文连

液晶与显示 doi:10.3969/j.issn.1007-2780.2000.02.005

由于有机EL属于电注入发光,因而电极材料在EL器件的载流子注入中起着重要作用,但这往往被人们所忽略.本文描述了正负电极材料的功函数、电极材料及结构等对EL器件性能有着重要影响,并对电极材料工作机制进行了讨论.

关键词: 电极材料 , 有机电致发光器件 , 聚合物

有机EL器件的研究及产品开发现状

张素梅 , 石家纬 , 李靖

液晶与显示 doi:10.3969/j.issn.1007-2780.2004.01.008

介绍了有机EL器件的结构、工作原理及特点,概述了有机EL器件的研究现状及产品开发现状,对器件今后的发展做了展望.

关键词: 有机 , EL器件 , 产品开发

The formation of stacking fault tetrahedra in Al and Cu I Dipole annihilation and the nucleation stage

Acta Materialia

The present work focuses on stacking fault tetrahedron (SFT) nucleation upon annihilation of edge dislocation dipoles in Al and Cu SFT nucleation is promoted by relatively low vacancy migration barriers along defected channels, typical of pipe diffusion-like processes, forming small vacancy clusters and elemental SFTs Within about 1 ns, depending on the material under investigation, the small initial vacancy clusters aggregate into larger clusters, including complete, incomplete and truncated SFTs Cluster aggregation occurs by diffusion of vacancy complexes whose mutual transformation and energetics are analyzed and compared It is concluded that the unique presence of deformation-induced SFTs, such as those found experimentally in Al, originates from a local mechanism of forced vacancy injection by dislocation reactions Subsequent stages of SFT growth by successive vacancy absorption and ledge expansion are deferred to companion papers (C) 2010 Acta Materialia Inc Published by Elsevier Ltd All rights reserved

关键词: Stacking fault tetrahedron;Dislocation dipole;Dislocation;annihilation;Molecular dynamics simulations;Pipe diffusion;edge-dislocation dipoles;fcc metals;plastic-deformation;tensile;properties;vacancy clusters;single-crystals;temperature-dependence;anomalous production;energy calculations;saddle-points

Fe(acac)3-Al(i-Bu)3对马来酸酐与茴香脑共聚的催化性能

杨科芳 , 房江华 , 高连勋

催化学报

研究了Fe(acac)3-Al(I-Bu)3(acac=乙酰丙酮)催化体系对马来酸酐(MA)与茴香脑(ANE)共聚反应的催化性能. 动力学研究结果表明,MA与ANE共聚对单体的浓度呈一级反应,其表观活化能为31.0 kJ/mol. 用IR和13C NMR研究了共聚物的结构,结果表明聚合物是交替的,其中酸酐的含量为45.6%. 用GPC测定了聚合物的分子量及其分布,结果表明分子量的分布较窄,PDI=1.19～1.42. 用DTA研究了聚合物的热力学性质,其分解温度为501.1 ℃.

关键词: 乙酰丙酮铁 , 三异丁基铝 , 马来酸酐 , 茴香脑 , 共聚反应