Synchrotron small angle X-ray scattering study on the conformation of polystyrene in compressed CO2-toluene mixture

Synchrotron small angle X-ray scattering (SAXS) was performed to investigate the effect of dissolved CO2 in toluene on the conformation of polystyrene (PS) in the solution. It has been found that the second virial coefficient A2 and the radius of gyration Rg decrease with the increasing antisolvent CO2 pressure. The scattering intensity of PS chain followed l(h)∞h-αunder different antisolvent pressures (0, 0.6, 1.5, 2.4, 3.3, and 4.2 MPa), suggesting that the PS chain has self-similar structure behavior or a fractal structure in the presence of antisolvent CO2.All this reveals a large effect of antisolvent pressure or the solubility of CO2 in the solution on PS structure. The fractal dimensions increase with the increasing antisolvent pressure, indicating that the polymer chain changes from a swollen coil into a rather dense globule in the course of adding antisolvent CO2.     

An analysis of fractal geometry of macromolecular gelation

With fractal geometry theory and based on experiments, an analysis of fractal geometry behavior of gelation of macromolecules was carried out. Using the cross-linking copolymerization of styrene-divinylbenzene (DVB) as an example, through the determinations of the evolution of the molecular weight, size and the dependence of scattering intensity on the angle of macromolecules by employing laser and synchrotron small angle X-ray scattering, respectively, this chemical reaction was described quantitatively, its fractal behavior was analyzed and the fractal dimension was also measured. By avoiding the complex theories on gelation, this approach is based on modern physical techniques and theories to perform the analysis of the behavior of fractal geometry of macromolecular gelation and thus is able to reveal the rules of this kind of complicated gelation more essentially and profoundly.     

SiO2—PEG溶胶的网络结构与分形特征

添加少量聚乙二醇（ＰＥＧ）于ＴＥＯＳ－Ｈ２Ｏ－Ｃ２Ｈ５ＯＨ－ＮＨ４ＯＨ溶胶体系中，可以改变ＳｉＯ２溶胶粒子的生长过程和网络结构的分形结构。通过小角Ｘ光散射，透射扫描电镜，激光粒度分布仪等手段对这一过程进行分析测试，同时探讨了ＰＥＧ对ＳｉＯ２溶胶－凝胶的修饰机理，有力地证明了分形行为的存在，着重研究了其分数维的变化规律，并提出ＰＥＧ在该溶胶中的作用模型。     

Ti-Mo合金氢化物微观缺陷的小角X射线散射研究

采用小角X射线散射(SAXS)方法对Ti-Mo合金氢化物的微观缺陷进行了研究.结果表明,氢化物样品中Mo含量为5at％时,所测定的SAXS强度在高散射角区明显低于其他样品的SAXS强度.氢化物中的晶粒及其内部的亚结构是引起SAXS现象的散射体,而这些亚结构是由合金氢化时引入的大量位错所产生.Mo 含量为5at％合金主要为hcp结构而其他合金为bcc结构,但两种合金氢化后都成为fcc结构的氢化物.据此,认为hcp结构与bcc结构Ti-Mo合金在氢化时氢化物结构相同但引入的位错缺陷特征不同. 关键词： Ti-Mo合金氢化物 小角X射线散射 微观缺陷     

飞行时间计数器端盖模型中光产生和传输的蒙德卡罗模拟

描述了北京谱仪中端盖飞行时间闪烁计数器模型的光产生和传输的蒙德卡罗模拟. 其结果与实验符合较好.     

大鼠骨质疏松模型的小角x射线散射研究

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北京同步辐射装置及科学活动

简要介绍北京同步辐射装置及其在生物学、材料科学、催化学、地矿和Ｘ射线光刻等领域的科学研究进展。     

SAXS测定二氧化硅胶体粒子结构

本文考察了正硅酸乙酯(TEOS)在碱性催化条件下通过水解和缩聚而制得的二氧化硅胶体的小角X-射线散射(SAXS)特征，通过散射数据对Porod负偏离的分析和校正，测定了胶体粒子的几何结构，包括胶团尺度分布、胶核尺度分布及平均界面层厚度，这有助于认识胶体的物理化学特征。