石墨炉内石墨探针表面上的原子化机理研究 III. 铬的原子化机理

本文利用探针原子化技术, 研究了普通管式石墨炉内石墨探针表面上铬化合物的原子化过程。X射线衍射分析(XRD)、俄歇电子能谱(AES)、化学分析光电子能谱分析(ESCA)与石墨炉原子吸收光谱(GFAAS)测量的综合结果表明, 铬化合物在灰化阶段即可转化为稳定的碳化物, 最后由碳化物的热分解生成气态铬原子。     

CuO-Ag2O/γ-Al2O3催化剂的TPR特性及氧化活性研究

采用程序升温还原技术(TPR)研究CuO-Ag2O/γ-Al2O3双组分及其单组分催化剂的还原特性以及热处理温度对其还原性能的影响。发现不同负载量的Cuo-Ag2O/γ-Al2O3催化剂的还原特性有明显差异, 反映出催化剂表面存在着不同种类的铜物种。Ag2O的存在, 使催化剂的TPR峰位与单组分CuO/γ-Al2O3的TPR曲线产生明显差异, 还原峰发生位移, 随Ag2O添加量的增加, 位移增大。对苯的完全氧化反应结果表明, 催化剂的氧化活性次序为:CuO-Ag2O/γ-Al2O3>CuO/γ-Al2O3>Ag2O/γ-Al2O3。热处理温度升高, 使催化剂表面铜物种分散状态及其还原性能发生变化。从500~900℃, 存在一个使铜物种达到最佳分散态的温度。讨论了负载于γ-Al2O3载体上的CuO-Ag2O双组分及其单组分催化剂在还原过程中金属与载体, 金属与金属间的相互作用以及热处理温度对其还原性能的影响。     

Experimental evidence for reduced chain segment mobility in poly(amide)-6/clay nanocomposites

Poly(amide)-6/clay nanocomposites are investigated by means of modulated temperature differential scanning calorimetry. The importance of polymer–filler interaction is explored by comparing nanocomposites based on untreated and organically modified clay. During quasi-isothermal crystallization experiments, an excess contribution is observed in the recorded heat capacity signal due to reversible melting and crystallization. The magnitude of this excess contribution depends on the nanocomposite investigated. We suggest that it is directly related to the segmental mobility of the polymer chains in the interphase region. As such, the magnitude of this excess contribution can be used to quantify the efficiency of the polymer–clay interaction. Depending on the clay type used, differences in interfacial interaction can be achieved, which is of great importance with respect to the improvement of material properties. Based on thermal analysis results, a simple interphase model is proposed that is able to account for both the thermal and mechanical properties of poly(amide)-6/clay nanocomposites.     

任意多阶程序升温优化程序用于氨基酸对映体的分离

用氨基酸对映体在手性毛细管柱上扮离作实例, 研究了任意多阶程升优化程序的普遍适用性. 按计算结果进行实验所得的实际色谱图证明, 优化程序的应用将有助于在保证分离度的前提下, 大大缩短分析时间.提出了一种可以大体反映程序升温下复杂样品各组分在柱内运动过程的轨迹图(x-t图).轨迹图上所显示的每一组分在到达行程终点的时间的准确性得到了色谱实验的验证, 从而为探讨物质在各种条件下的柱内运动状,况特别是为多维色谱的深入研究提供了可能性.     

ZSM-5分子筛转化乙醇为乙醚的研究

用原位红外技术、程序升温热脱附和X射线光电子能谱研究了乙醇和乙醚在HZSM-5和PZSM-5上的吸附及表面状态, 并与催化乙醇为乙醚的活性和选择性相关联. 结果表明, 乙醇与质子酸中心作用形成吸附态乙醇, 该吸附态乙醇与气相乙醇反应生成吸附态乙醚, 然后从表面脱附. 磷的掺入能有效抑制积炭发生.     

MORPHOLOGY EVOLUTION IN PTFE AS A FUNCTION OF MELT TIME AND TEMPERATURE Ⅱ. LOW MOLECULAR WEIGHT FOLDED CHAIN SINGLE CRYSTALS AND BAND STRUCTURES

The effect of sintering dispersed and bulk, low molecular weight (Mn = 50,000 Da), nano-emulsion polytetrafluoroethylene (PTFE) particles near their melting point is described. With the nascent particles consisting of ca.75 nm diameter, hexagonal, single crystals, sintering at, e.g., 350℃, results, initially, in merger of neighboring particles,followed by individual molecular motion on the substrate and the formation of folded chain, lamellar single crystals and spherulites, and on-edge ribbons. It is suggested these structures develop, with time, in the mesomorphic "melt". Sintering of the bulk resin yields extended chain, band structures, as well as folded chain lamellae; end-surface to end-surface merger,possibly by end-to-end polymerization, occurs with increasing time.     

CdO掺杂对BaTiO3基半导化陶瓷PTCR效应的改善

钛酸钡基半导化陶瓷中的PTCR效应通常与材料中的施受主掺杂切相关,蒸汽掺杂能够大幅度影响材料的PTCR效应。CdO在高温下具有较高的蒸汽压,是一种适用的蒸汽掺杂剂,研究了CdO以及CdO蒸汽对掺Y^3+的Ba1-xSrxTiO3陶瓷的PTCR效应的影响,结果首次发现了Cd^2+掺杂样品的PTCR效应都有不同程度的提高,采用蒸汽掺杂时,效果更为显著。现有的理论很难解释Cd^2+掺杂能够提高钛酸钡基材料PTCR效应。我们从缺陷化学的角度,分析了Cd^2+在BaTiO3基材料中的行为,推断表明这种现象可能是由于铁电相变时,处于晶界区的Cd^2+在Ba位和Ti位之间转换造成的。