机械合金化过程中Fe70B30粉末晶粒尺寸和微观应变的研究

用Ｘ射线和电镜研究了Ｆｅ＿（７０）Ｂ＿（３０）粉末经不同时间高能球磨后晶粒尺寸和微观应力的变化。在机械合金化过程中，粉末的Ｘ射线衍射谱的宽度随球磨时间的增加逐渐加宽，这是晶粒细化和内部微观应力共同作用的结果。Ｘ射线衍射结果表明：随着机械合金化的进行，粉末的晶粒尺寸逐渐减小，球磨初期晶粒尺寸下降较快，经１５ｈ球磨，晶粒尺寸为２５ｎｍ，机械合金化进行到一定时间后晶粒尺寸下降缓慢，８０ｈ球磨后晶粒尺寸可达５ｎｍ。在机械合金化过程中球磨所造成的微观应变不大，球磨初期粉末的内应力随球磨时间增加而增加，当粉末粒子尺寸很小时，随球磨的进行粉末中的微观应变显著下降。     

Enhanced electron emission from phosphorus-doped diamond-cladsilicon field emitter arrays

Undoped and phosphorus (P)-doped diamond-clad Si field emitter arrays have been successfully fabricated using microwave plasma chemical vapor deposition (MPCVD) technology. The electron emission from the blunt diamond-clad microtips are much higher than those for the pure Si tips with sharp curvature due to a lower work function. Furthermore, the characteristics of emission current against applied voltage for the P-doped diamond-clad tips show superior emission at lower field to the undoped ones. After the examination of Auger electron spectroscopy (AES) and electrical characteristics of as-grown diamond, such a significant enhancement of the electron emission from the P-doped diamond-clad tips is attributed to a higher electron conductivity and defect densities     

Modeling electromigration lifetime under bidirectional currentstress

Electromigration reliability of interconnect under bidirectional current stress has been studied in a wide frequency range (mHz to 200 MHz). Experimental results show that the AC lifetime rises with the stress current frequency. The current density exponent and the activation energy of AC lifetime are found to be twice that of DC lifetime. Pure AC current stress failure at extremely high current density is believed to result from thermal migration of metal at hot/cold transition points     

Multiple negative-differential-resistance (MNDR) phenomena of ametal-insulator-semiconductor-insulator-metal (MISIM)-like structurewith step-compositioned InxGa1-xAs quantum wells

In this paper, a new multiple negative-differential-resistance (MNDR) device based on a metal-insulator-semiconductor-insulator-metal (MISIM)-like structure with step-compositional In_xGa_1-x As quantum wells has been fabricated and demonstrated. The interesting MNDR phenomena are found in the current-voltage (I-V) characteristics of this device. At room temperature, the triple switching behaviours and quadruple stable operation states are obtained. In addition, the sixfold switching behaviors and a staircase-shaped I-V characteristic are observed at -105°C. A sequential carrier accumulation at InGaAs subwells and the potential lowering process are used to qualitatively explain the interesting MNDR phenomena. From the experimental results, it is shown that the studied device has good potential in multiple-valued logic applications     

Mathematical simulation and experimental verification of melting resulting from the coupled effect of natural convection and exothermic heat of mixing

When melting processes are associated with an exothermic heat of mixing, unique coupled transport phenomena take place. In this article, a mathematical model has been developed to simulate these unique coupled heat and mass transfer events. The model was based on the control-volume finite difference approach and on an enthalpy method. In order to verify the mathematical model, a low-temperature physical model was established consisting of ice and sulfuric acid solutions. In this physical model, both temperature and velocity measurements were carried out. The model predictions were compared with experimental measurements, and they were found to be in good agreement. The model was also applied to a high-temperature system, namely, the melting of silicon metal in liquid high carbon iron. The predictions distinguished two periods present in the entire melting process. In the first period, the silicon was heated up. The second period, i.e., free melting period, occurred in tandem with the exothermic reaction, and consequently, the melting process was greatly accelerated. As was the case with the low-temperature physical model, as with the high-temperature system, good agreement was obtained between the predicted results and the experimental measurements.     

聚合物复合材料填充剂的改性

在前人研究的基础之上，归纳总结了聚合物复合材料填充剂的种类，综述了对其进行表面改性的目的、条件、方法、工艺以及对改性结果的表征等。文章还分析了影响填充聚合物复合材料性能的因素，指出了今后发展的方向。     

无机膜的应用与展望

本文综述了无机膜的发展、制备方法和应用。