超级微波消解-石墨炉原子吸收光谱法测定虾蛄中镉含量

目的 比较超级微波和普通微波消解方法,建立超级微波-石墨炉原子吸收法测定虾蛄中镉的方法。方法 分别采用超级微波和普通微波消化大虾标准物质,对比消解效果,优选消解方法,采用石墨炉原子吸收法测定,优化基改改进剂、灰化温度等工作参数,确定最佳的分析方法,同时加标回收验证方法的准确性与可靠性。结果 两种消解方法下测得结果均在参考值范围内,在选定方法条件下,镉在质量浓度0.0～2.0 μg/L范围内线性关系良好,相关系数γ=0.999,检出限为0.04 μg/L,定量限为0.12 μg/L,加标回收的准确度为88.5%～105.2%,精密度为2.93%～4.92%。结论 超级微波消解法优于普通微波消解,其耗酸量低、高效便捷、测得数据准确稳定,便于在基层推广,适用于批量虾蛄样品的镉污染监测工作。     

Catalytic Performance of Carbon Materials Supported Pd Nanoparticles in Selective Hydrogenation of Acetylene

Pd/C catalysts were prepared by deposited Pd nanoparticles (NPs) on different carbon supports including activated carbon (AC), graphite oxide (GO), and reduced graphite oxide (rGO) using sol-immobilization method. Through transmission electron microscopy, powder X-ray di raction, and X-ray photoelectron spectroscopy, the role of the carbon supports for the catalytic performances of Pd/C catalysts was examined in selective hydrogenation of acetylene. The results indicate that Pd/AC exhibited higher activity and selectivity than Pd/GO and Pd/rGO in the gas phase selective hydrogenation of acetylene. Thermal and chemical treatment of AC supports also have some effect on the catalytic performance of Pd/AC catalysts. The differences in the activity and selectivity of various Pd/C catalysts were partly attributed to the metal-support interaction.     

The nanomechanical behavior of a graphite nanoplatelet/polycarbonate nanocomposite

Quasi-static nanoindentation has been used to characterize the mechanical properties of polycarbonate reinforced with graphite nanoplatelets (GNPs). Poor dispersion or low quality interfacial interactions of GNPs in a polymer matrix can significantly decrease the relative improvement in the material's mechanical strength and stiffness. In this study, the surfaces of GNPs were modified to achieve better dispersion and interfacial interaction between fillers and matrix. The GNP/PC nanocomposite has a heterogeneous microstructure, and the original mechanical properties between filler and matrix have large differences. Using a spatially sensitive probe method leads to measured values of modulus and hardness that correlate with the indentation sampled volume. A grid indentation procedure was performed with variable sampling volumes to provide a statistical measurement of modulus and hardness for the nanocomposite materials. The surface treatment leads to a significant increase in both stiffness and hardness for GNP reinforced composites.     

固体进样石墨炉原子吸收光谱法测定船用燃料油中硅、铝含量

建立了固体进样石墨炉原子吸收光谱法测定船用燃料油中微量硅、铝元素含量的快速检测方法。通过选择谱线和背景校正模式,优化了石墨炉条件;根据待测样品及元素特点优化了升温程序。硅、铝的测定波长分别为251.6,394.4 nm,采用塞曼背景校正,样品无需前处理,直接通过石墨舟进样检测。燃料油中硅、铝元素的检出限分别为0.165,0.126 ng;3个浓度水平下,硅元素平均回收率为88%~92%,铝元素平均回收率为93%~95%,测定结果的相对标准偏差为4.2%~10.7%(n=6)。采用本法对实际燃料油样品进行测定,硅、铝元素的测定结果与IP 501方法测定结果基本一致。该方法取样量少、操作简便、快速,检验结果准确度高、稳定性好,适用于船用燃料油中微量硅、铝元素含量的定量检测。     

浊点萃取-高分辨连续光源石墨炉原子吸收光谱法测定环境水样中的痕量铅

比较了三种不同的分离富集方法——共沉淀法、离子交换法和浊点萃取法对水样中痕量铅的富集效果,其中,浊点萃取法水样用量少、富集因子大、操作简便,故选取浊点萃取法对环境水样中的铅进行富集。采用浊点萃取-高分辨连续光源石墨炉原子吸收光谱法测定了采自北京市通惠河水样中的痕量铅。结果表明,该测定方法的检出限为0.08 μg·L-1,相对标准偏差为1.3%~4.5%(n=6),加标回收率为93%~108%,样品溶液的富集因子为29。通惠河13个采样点水样中铅含量均符合国家规定的地表水水质Ⅰ类水标准,且从通州区至朝阳区呈现铅含量逐渐减少的趋势。     

基于CSY-998型传感器研究金属的线膨胀系数

本文基于改造其它实验中的自动控制加热炉,利用CSY-998型传感器平台研究铜棒的线膨胀系数,一方面是利用现有仪器进行改装,提高仪器的利用率;另一方面对学生拓展思维、开拓视野、创新实验也起到了较好的作用。     

Electronic Effect of Carbon Support on Pt Catalyst Supported on Graphite Intercalation Compound

Graphite intercalation compounds(GIC) were tested as an experimental model for studying the electronic effect of carbon support on the catalytic activity and poisoning tolerance of Pt catalyst for direct methanol fuel cells. The GIC samples with different intercalation degrees were prepared by electrolyzing graphite flake in H2SO4 for varying the periods of time. The GIC-supported Pt catalyst was deposited electrochemically. The catalytic activity and poisoning tolerance of the GIC-supported Pt catalysts were evaluated. It was found that GIC with sulfate anion as intercalate was able to catalyze methanol electrooxidation, which could be related to the positive charges generated on the graphite layer upon intercalation. As intercalation degree increased, the catalytic activity of the GIC-supported Pt catalyst decreased while the poisoning tolerance improved. This suggests that electron donation from support to catalyst had great effect on both catalytic activity and poisoning tolerance of Pt catalyst. And intercalation can be adopted as another important way to make modification on carboneous catalyst support.     

Structure Characterization of CuCl2-FeCl3-H2SO4 Graphite Intercalation Compounds

"Graphite intercalation compounds with CuCl2-FeCl3-H2SO4 were synthesized via a hydrothermal treatment at 150 oC and exfoliation method. The structure and composition of these graphite intercalation compounds were analyzed by means of X-ray diffraction, energy dispersive X-ray and high-resolution transmission electron microscopy. The results demonstrate that the CuCl2-FeCl3-H2SO4 molecules were successfully intercalated into the interlayer of the graphite sheets. The temperature dependence of magnetization was measured from 5 K to 300 K. Two antiferromagnetic transitions of the graphite intercalation compounds were observed at low temperatures. The critical transition temperatures are estimated to be about 50 and 102 K. The related magnetic properties are discussed briefly."     

石墨管涂覆-塞曼效应石墨炉原子吸收法测定土壤和沉积物中钡

样品使用硝酸-氢氟酸-高氯酸湿法消解,在0.015 mol·L-1硝酸介质中,采用自制涂钨石墨管,塞曼效应背景校正技术石墨炉原子吸收法测定了土壤和沉积物中的钡。经涂钨处理的石墨管表面形成了稳定的碳化钨层,有效避免了在原子化过程中待测元素钡与石墨管直接接触形成难熔碳化物,大幅度提高了检测的灵敏度和精密度,显著延长了石墨管使用寿命。碳化钨为间充型碳化物,在高温下可以产生较强的还原性氛围,可在一定程度上避免土壤和沉积物中常见的高浓度基体成分在原子化阶段生成难熔的氧化物而干扰钡的测定。氢氧化钙分子带背景干扰可以通过稀释法消除。该法测定土壤和沉积物中钡操作简便, 快速;检出限为4.2×10-10 g·g-1。环境样品中钡测定的相对标准偏差范围为2.0％～6.5％, 测定标准土壤的相对偏差均小于5％。