Structure and mechanical properties of Al/AlN multilayer with different AlN layer thickness

Nanometer scale Al/AlN multilayers have been prepared by dc magnetron sputtering technique with a columnar target. A set of Al/AlN multilayers with the Al layer thickness of 2.9 nm and the AlN layer thickness variation from 1.13 to 6.81 nm were determined. Low angle X-ray diffraction (LAXRD) was used to analyze the layered structure of multilayers. The phase structure of the coatings was investigated with grazing angle XRD (GAXRD). Mechanical properties of these multilayers were thoroughly studied using a nanoindentation and ball-on-disk micro-tribometer. It was found that the multilayer hardness and reduced modulus showed no strong dependence on the AlN layer thickness. Al2.9 nm/AlN1.13 nm multilayer had more excellent tribological properties than single layers and other proportion multilayers with a lowest friction coefficient of 0.15. And the tribological properties of all the multilayers are superior to the AlN single layer.     

小分子硫原子团簇正离子的结构稳定性

用分子图形软件设计出 4 9种硫原子团簇Sn+ (n =3～ 13)的结构 ,使用B3LYP密度泛函进行几何构型优化和振动频率计算 ,根据分子的总能量得出最稳定的同分异构体 .在硫原子团簇正离子中 ,大部分原子为二配位成键 .带有一、三配位的原子结构的总能量较高 .部分最稳定硫原子团簇正离子的构型与最稳定的中性硫原子团簇的构型完全不同 .     

新超导体MgCNi3的虚晶掺杂研究

用全势线性缀加平面波方法,考虑局域自旋密度近似研究虚晶掺杂MgCNi3的超导电性和磁性.计算了自旋极化能带结构、体弹性模量和它对压力的导数、原子磁矩 m 及其变化率.计算结果表明,对于电子掺杂的Mg1-xAlxCNi3(0≤x≤0.5), 超导电性和磁涨落随掺杂量的增加逐渐减小.空穴掺杂的Mg1-xNaxCNi3,在x＝0.12处出现铁磁相变,超导电性消失.在MgCNi3少量空穴掺杂区域(0≤x<0.12),表现为超导与磁涨落共存的不稳定状态.     

一种新的磷化铟复合沟道高电子迁移率晶体管小信号物理模型

针对磷化铟(InP)复合沟道高电子迁移率晶体管(HEMT)的特点，对常规单沟道HEMT的小信号物理模型进行了修正，提出了一种新的用于复合沟道HEMT的小信号物理模型，用商用器件模拟软件ISE(integrated systems engineering)对其进行了仿真验证，对比了实测和仿真的I-V特性及转移特性曲线，重点研究了在InGaAs/InP双层沟道中考虑量子效应后的电场和电流密度随着不同栅电压的变化趋势，研究结果表明，由于在沟道中存在量子效应，在栅下靠源端低电场区域，电流主要分布在InGaAs沟道 关键词： 高电子迁移率晶体管 复合沟道 物理模型 磷化铟     

SHS等离子喷涂制备FeAl2O4-Al2O3-Fe纳米复合涂层的研究

利用SHS等离子喷涂技术,将经过机械团聚法制备的Fe2O3-Al复合粉体送入等离子焰流,沉积出厚度约为400 μm的复合涂层.利用XRD,SEM 和TEM等检测手段对涂层的成分和组织进行了分析,测定了涂层的显微硬度、断裂韧性以及耐磨性.结果表明涂层为具有纳米结构的FeAl2O4-Al2O3-Fe纳米复合组织;涂层的显微硬度为HV100g870;断裂韧性是普通Al2O3涂层的2倍;无润滑磨损的耐磨性是普通Al2O3涂层的2.5倍.     

过量Zn对β-Zn4Sb3热电性能影响的研究

采用真空熔融缓冷方法制备了单相β-Zn4Sb3以及含有过量Zn的β-Zn4Sb3块体热电材料.在300—700K的温度范围内测试了材料的电导率、Seebeck系数和热导率,研究了β-Zn4Sb3化合物中过量Zn的分布状态及其对材料热电性能的影响规律.结果表明：过量的Zn作为第二相较均匀的分布在β-Zn4Sb3的晶界上,随着Zn含量增加,材料电导率和热导率上升,Seebeck系数下降,Zn第二相的引入能有效提高材料的功率因子,Zn过量2at%的材料在700K时其ZT值达到1.10.     

SiO2-羟基表面上金属原子的第一性原理研究

采用第一性原理方法研究了SiO2-羟基表面上几种金属原子的吸附性质,发现In和Ga在SiO2-羟基表面上的结合很弱,而Fe,Co,Ni在该表面上与Si,O形成强的化学键.等势能面和扩散势垒计算表明In(Ga)的扩散激活能只有0.1-0.3 eV,表明这两种原子容易在表面上扩散.这些结果可以定性地解释纳米合成中的一些实验现象.     

复杂像散椭圆光束的轨道角动量的实验研究

提出一种直接测量光束的轨道角动量的方法，其原理是把具有轨道角动量的光束照射到一个金属靶上，使其在光束的角动量作用下发生转动. 通过测量靶转动的角度来计算光束的角动量值. 对几种不同参数的光束的轨道角动量进行了测量，获得了轨道角动量与光束参数之间的关系，实验结果与理论分析较好地符合. 关键词： 复杂像散椭圆光束 轨道角动量 测量     

Features of the total disintegration events of heavyemulsion targets caused by 4.5A GeV/c16O

Total disintegration events produced by 4.5\,A GeV/c $^{16}$O--AgBr interactions are analysed to investigate the characteristics of secondary charged particles produced in such collisions. The multiplicity distributions of grey, black, and relativistic charged particles can be well represented by Gaussian distribution. The average multiplicity of grey particles is found to increase with the mass of projectile increasing, while that of black particles is found to decrease with the mass of projectile increasing. This result is in good agreement with the prediction of fireball model. Finally, the linear dependence between grey and black particles is observed, but there is no distinct dependence between the production of relativistic charged particles and the target excitation.     

Molecular dynamics of MgSiO3 perovskite melting

The melting curve of MgSiO分子动力学 MgSiO3钙钛矿 熔化温度 高压melting temperature, molecular dynamics, high pressureProject supported by the National Natural Science Foundation of China (Grant Nos 10274055 and 10376021),the Natural Science Foundation of Gansu Province, China (Grant No 3ZS051-A25-027) and the Scientific Research Foundation of Education Bureau of Gansu Province, China (Grant No 0410-01).2005-01-125/8/2005 12:00:00 AMThe melting curve of MgSiO3 perovskite is simulated using molecular dynamics simulations method at high pressure. It is shown that the simulated equation of state of MgSiO3 perovskite is very successful in reproducing accurately the experimental data. The pressure dependence of the simulated melting temperature of MgSiO3 perovskite reproduces the stability of the orthorhombic perovskite phase up to high pressure of 130GPa at ambient temperature, consistent with the theoretical data of the other calculations. It is shown that its transformation to the cubic phase and melting at high pressure and high temperature are in agreement with recent experiments.