碳糊电极吸附伏安法测定痕量钒

研究了钒 荧光镓(LMG)络合物在碳糊电极上的吸附伏安行为,发现其在+0.81V(vs.SCE)的阳极二次导数峰电流与钒(V)的浓度在一定范围内呈线性关系。在pH=4.3的0.26mol/L的HAc NH4Ac缓冲溶液中,于+0.4V富集,从+0.4至+1.4V以300mV/s线性扫描,方法线性范围为4.0×10-9～1.0×10-7mol/L(5.0×10-7mol/LLMG)和1.0×10-7～1.2×10-6mol/L(2.0×10-6mol/LLMG),检出限为1.0×10-9mol/L(S/N=3)。该法用于煤飞灰,粉煤灰和水样中钒的测定,结果满意。     

高利用率多壁碳纳米管负载金铂合金纳米粒子催化剂在碱性溶液中的甲醇电催化氧化性能研究

使用乙二醇还原法合成了一系列高利用率多壁碳纳米管负载的金铂双金属纳米粒子电催化剂,在碱性溶液中由循环伏安和计时电流法测试该AuPt催化剂对于甲醇氧化反应的电催化活性.透射电子显微镜、X射线衍射与X射线能谱观测催化剂形貌,表征催化剂结构.结果表明,金铂双金属纳米粒子均匀分散在碳纳米管上,催化剂具有良好甲醇电氧化性能.实验表明Au/Pt/MWCNTs比为10∶8∶32(bymass)时,该催化剂具有最高甲醇电氧化峰电流密度与最负起始氧化电位.     

在Pt/CNTs催化层中预混-溶解La2O3颗粒来构筑孔结构促进甲醇电氧化

为认识孔隙度增加对甲醇电氧化的影响,将熔盐法制备的La2O3颗粒与Pt/CNTs(碳纳米管)预混合然后用HClO4溶掉La2O3颗粒,从而增加了Pt/CNTs催化层的孔隙度.扫描电子显微镜(SEM)观察表明,该处理可以形成孔结构.用循环伏安和计时电流实验考察了孔隙度增加对甲醇电氧化的影响,结果表明甲醇电氧化电流可增加57%.分析认为,电流增加的原因是由于多孔催化层中甲醇更易于到达Pt催化剂表面进行电氧化.该研究表明,通过在催化层中预混-溶解La2O3来增加孔隙是一种改善催化层性能的有效方法.     

Overlapping chemical and genetic diversity in Ligularia lamarum and Ligularia subspicata. Isolation of ten new eremophilanes and a new seco-bakkane compound

Root chemicals and DNA sequences were analyzed for Ligularialamarum samples collected in Yunnan and Sichuan Provinces of China and the relationship between the plant and Ligulariasubspicata, its taxonomically closest species, was examined. Both species produce furanoeremophilanes and eremophilan-8-one derivatives as the major components. Eleven new compounds, including a new seco-bakkane compound, were isolated. The two species were found to harbor overlapping intra-specific diversities with respect to the chemicals and the DNA sequences.     

倾斜均质表面上非等径液滴的聚合特性

对倾斜均匀表面上非等径液滴的聚合过程及特性进行了可视化实验研究,获得了液滴半径和表面倾角等参数对液滴聚合过程中液滴液桥半径、接触角和接触线变化特性的影响规律,进一步说明了倾斜表面上液滴聚合可以加快液滴的运动.     

Triggering and guiding high-voltage discharge in air by single and multiple femtosecond filaments

The abilities to trigger and guide high-voltage discharge by using single and multiple filaments (MFs) are experimentally studied. It is shown that the discharge voltage threshold can be reduced significantly in both regimes of single and MF; however, the MF does not gain a larger reduction than a single filament. This behavior of the MF is attributed to the single discharge path rather than simultaneous multiple ones as one might expect during the discharge process.     

The polarization characteristics of single shot nanosecond laser-induced breakdown spectroscopy of Al

The polarization-resolved laser-induced breakdown spectroscopy (PRLIBS) technique, which can significantly reduce the polarized emission from laser plasma by placing a polarizer in front of the detector, is a powerful tool to improve the line-to-continuum ratio in LIBS applications. It is shown that the continuum emission from the plasma produced through ablating an Al sample by nanosecond laser pulses is much more polarized than the discrete line emission with the singlepulse PRLIBS technique. The effects of laser fluence and detection angle on the Al polarization spectrum are systematically explored experimentally. The calculated result of the polarization spectrum as a function of laser fluence shows that it is in agreement with the experimental observations.     

太赫兹技术在爆炸物检测中的应用

研究了太赫兹成像技术在爆炸物探测中的应用,分析了太赫兹透射型时域光谱系统的实验装置,介绍了太赫兹时域光谱的测量步骤。确定了四种爆炸物样品(TNT,RDX,DNT,HMX)在太赫兹波段的吸收谱。结果表明,这四种爆炸物样品在0~2.5THz的频率范围内均存在特征吸收峰,这为太赫兹技术检测爆炸物提供了一种有效的途径。     

飞秒激光等离子体单丝导电性能的空间分辨研究

对飞秒激光等离子体单丝的导电性能进行空间分辨研究. 在消除测量时引入的接触电阻的影响后,得到单丝电阻在280-630 kΩ/cm范围. 为了进一步研究单丝的导电性能,对单丝诱导放电能力进行了空间分辨测量. 结果显示,最低放电阈值降低至自发放电的~50%. 从每段细丝的电阻和诱导放电阈值的空间分布看出:在成丝阶段,二者的变化趋势基本一致,细丝的电阻值和放电阈值均在焦点附近出现迅速下降. 将每段细丝的电阻和放电阈值相对应,建立了细丝诱导放电阈值-电阻的线性拟合关系,证实了细丝电阻对放电阈值的影响. 关键词： 飞秒激光 等离子体丝 电阻率 接触电阻