Detailed Characteristics of Expansion Velocity of Si from Laser Ablated SiC

Optical emission of plasma is used to investigate the characteristics of dynamics distribution in the plume gen- erated by ablation of a SiC sample using Nd：YAG laser. The plume expansion dynamics is characterized by time-of-flight measurement. We find that the profiles of Si （I） （390.55 nm） split into two components and the Si （1I） （634. 71 nm） spectra show two distinct expansion dynamics regions. The time-of-flight measurement of Si（ll） （634. 71 nm） under different laser irradianee conditions, from 0.236 G W/cm^2 to 1.667 G W/cm^2, are presented and discussed.     

氮化硼纳米管气敏特性的理论研究

采用密度泛函理论计算研究了氮化硼纳米管及碳掺杂氮化硼纳米管对CH4, CO2, H2, H2O, N2, NH3, NO2, O2, F2等十余种气体小分子的气敏特性. 研究结果表明: 氮化硼纳米管对CH4, CO2, H2, H2O, N2, NH3等气体分子不敏感, 而对O2, NO2, F2等气体分子比较敏感. 虽然碳掺杂氮化硼纳米管可以明显地改变其表面的化学反应活性, 增强了气体分子与氮化硼纳米管之间的相互作用, 但是并不能明显地改变其对所研究气体分子的敏感性.     

连续模型处理高剥离态离子在金属表面的能量获得

当高剥离态离子接近清洁金属表面时，表面上的电子由于强库仑相互作用会从金属表面转移到带有高电荷的离子上．这个电子转移过程可以用一速率方程确定，其中速率常数与高剥离态离子所带净电荷数，以及离子与金属表面的距离有关．由于金属表面的镜象势的作用，高剥离态离子在金属表面附近会受到加速作用而获得能量．本文采用经典镜象势，用数值方法处理了确定电子转移的速率方程，计算了高剥离态离子在金属表面的能量获得，计算结果与两组实验数据比较吻合．     

Diels-Alder型自修复聚氨酯胶粘剂的制备及其性能

目前,针对珍贵零件粘接后难以回收重复使用的问题,将可逆共价键引入胶粘体系成为解决问题的方向。研究使用糠醇(FA)和N,N′-(4,4′-亚甲基二苯基)双马来酰亚胺(BMI)制备了含有Diels-Alder(DA)键的二元醇(DA diol),使用六亚甲基二异氰酸酯(HDI)分别与聚四氢呋喃二醇(PTMG-2000)和DA diol反应封端,最后使用1,1,1-三(羟甲基)丙烷(TMP)与封端产物反应形成交联结构的聚氨酯材料(DPU)。结果表明,DPU具备优异的机械性能、热稳定性和粘接性能。DA键在DPU中具有可逆性且DA逆反应(r-DA)的最佳温度为135℃。DA键含量最多的DPU-Ⅳ的修复效率最高可达到89.0%。DPU-Ⅲ、DPU-Ⅳ粘接性能优异,对不锈钢粘接的剪切强度分别可达到(6.41±0.41)和(2.89±0.34) MPa;DPU-Ⅳ具有重复粘接使用的能力,对不锈钢基材重复粘接的3次的剪切强度分别为(2.89±0.34)、(1.91±0.15)和(1.68±0.20) MPa。粘接性能测试体现出胶膜自身强度与粘接的剪切强度、修复效率与重复粘接能力间的相关性。     

Monte Carlo Simulation on Energy Deposition of Low-Energy Electrons in Liquid Water

A Monte Carlo approach to simulate the transport and energy deposition of low energy electrons (E0≤10keV) in liquid water is presented. The elastic scattering of electrons is described by Mott cross section, which is derived from the relativistic wave equation of Dirac. The inelastic scattering model of electrons is based on the dielectric response theory with exchange effect included. A new method of sampling various inelastic scattering events is proposed in the simulation. Using the approach stated, the spatial distribution of inelastic scattering events and energy deposition of electrons in liquid water are computed and the results are compared with other theoretical studies.     

由复映射z←z~α十c(α<0)所构造的广义M-集的研究

阐述了构造复映射z←zα＋c（α＜0）所产生的广义Mandelbrot-集（简称M-集或M-分形图）的逃逸时间算法．通过改变参数a，作出了一系列有趣的分形图．这些分形图为若干卫星群环绕中央恒星的星群结构．定量地研究了恒星和卫星群的几何结构，并对a取非整数时分形图的结构特点和卫星群胚胎出现的原因进行了分析．最后给出几点结论．     

Silicon micro-hemispheres with periodic nanoscale rings produced by the laser ablation of single crystalline silicon

We describe the fabrication of silicon micro-hemispheres by adopting the conventional laser ablation of single crystalline silicon in the vacuum condition without using any catalysts or additives. The highly oriented structures of silicon micro-hemispheres exhibit many periodic nanoscale rings along their outer surfaces. We consider that the self-organized growth of silicon micro-structures is highly dependent on the laser intensity and background air medium. The difference between these surface modifications is attributed to the amount of laser energy deposited in the silicon material and the consequent cooling velocity.     

透镜到靶材的距离对脉冲激光诱导等离子体的影响机理研究

采用高功率抽运调Q激光器分别在真空和空气中烧蚀Ti-Al合金靶材激发等离子体,研究了在不同气体压强下透镜到靶材的距离对等离子体参数的影响机理对于焦距为111mm的聚焦透镜,当透镜到靶材距离小于透镜焦距时,随着距离逐渐接近焦距,真空和空气中电子温度、电子密度和谱线强度均逐渐增强.当透镜到靶材距离大于透镜焦距时,真空中,电子温度和电子密度仍然继续升高,而谱线强度却变化不大.空气中,等离子体参数却有不同的演化特性:等离子体的电子温度、电子密度和谱线强度在透镜到靶材距离为107 mm时达到最大值,当距离继续增大时,均呈现出迅速下降的趋势,当透镜到靶材距离大于112mm时,电子温度和电子密度又有明显上升,特征谱线强度却大幅下降.     

Self-Organized Micro-Columns and Nano-Spheres Generated by Pulsed Laser Ablation of Ti/A1 Alloy in Water

Dense arrays of micro-columns are formed on the surface of Ti-AI alloy by cumulative nanosecond pulsed laser ablation in water. The fabric-like structure characterized by Ti-A1 nano-spheres absorbed on micro-duster in liquid is most likely responsible for the occurrence of laser micro-etching and localized melting, resulting in continuous deepening of micro-holes and the formation of micro-columns. Laser induced plasma spectroscopy is carried out to reveal the effect of micro-columns on subsequent pulse laser ablation. The intensity of spectral lines from Ti ions by additional laser ablation of the modified spot is higher than that created over a smooth surface. These results suggest that the micro-columns lead to an enhanced absorption of the following laser energy. The proposed results and relevant discussions are of importance for the development of light-trapping coatings on a metal surface.     

名优白酒质量指纹专家鉴别系统

利用气相色谱法分析了中国名白酒(茅台、泸州老窖、五粮液、汾酒、董酒等)中的34种主要挥发性香味化学物质,根据这些香味化学物质之间的量比关系提出了中国名白酒的“质量指纹”是决定名白酒香型及质量特征的观点。建立了一套完整的名白酒质量指纹库。一次色谱分析可定量检测白酒中多种酯、醇、醛、酸并确定出它们之间的量比关系,通过计算机专家鉴别系统的自动分析,不仅能鉴别白酒的真伪,还能确定白酒的优劣。