热损伤奥克托金(HMX) 缺陷的X射线小角散射研究

奥克托金(HMX) 在温度作用下, 会发生热膨胀、 相转变、 热分解等物理、 化学变化, 导致在材料内部产生大量缺陷, 进而会对其宏观性能造成明显影响. 为了深入了解热损伤HMX内部的缺陷演化, 本文采用X射线小角散射和原子力显微技术研究了热损伤HMX的内部缺陷. 结果发现HMX在180 °C相变过程中散射曲线有明显的变化, 颗粒内部生成了大量10nm左右的孔洞, 随着加载时间延长, 其尺寸增大到25nm, 数量明显降低. 当HMX在190 °C、 200 °C保温5h时, 由于HMX热分解内部有新缺陷生成, 小角散射发现其尺寸约为5至8nm, 随着加载温度升高, 其数量增加.     

Hard X-ray optics simulation using the coherent mode decomposition of the Gaussian Schell model

The propagation of a hard X-ray beam from a partially coherent synchrotron source is simulated by using the novel method based on the coherent mode decomposition of Gaussian Schell model and wave-front propagation. We investigate how the coherency properties and intensity distributions of the beam are changed by propagation through optical elements. Here, we simulate and analyze the propagation of the partially coherent radiation trans- mitted through an ideal slit. We present the first simulations for focusing partially coherent synchrotron hard X-ray beams using this novel method. And when compared with the traditional method which assumes the source is a totally coherent point source or completely incoherent, this method is proved to be more reasonable and can also demonstrate the coherence properties of the focusing beam. We also simulate the Young’s double slit experiment and the simulated results validate the academic analysis.     

Quantitative evaluation of equatorial small-angle X-ray scattering for cylindrical fibers

Elongated microvoids, internal fibrillar structure, and edge scattering from both surface refraction cause an equatorial streak in small angle X-ray scattering. A model for analyzing the edge scattering of fibers is proposed. Simulation results indicate that the intensity of edge scattering from surface refraction of a cylindrical fiber is strong and makes an important contribution to the equatorial streak. Two factors influence edge scattering intensity. One is the sample-to-detector distance (D); edge scattering intensity increases with increasing D. The equatorial streak becomes weak when D is shortened. The other factor is the refraction index. Edge scattering intensity increases as the real component of the refraction index decreases. In experiment, weak or even no equatorial streaks were found for samples measured in a roughly index-matching fluid. Edge scattering can be eliminated or weakened, and it can be calculated by comparing the intensities of a cylindrical fiber when it is measured in air and in index-matching fluid. The simulation data are basically in agreement with the experimental data.     

微乳液体系中溶剂热合成Co纳米纤维

纳米材料的小尺寸及大的表面积使其在光学、电学、磁学以及化学性质上与体相材料具有显著的差异 ,从而在催化、电子、光学、磁性存储和超导等多方面具有很大的应用前景 [1] .目前 ,已经开发出许多制备纳米颗粒的技术 ,如溅射法、共沉淀法、溶胶 -凝胶法、水热法和微乳液法等 .其中利用微乳液等两亲分子有序组合体进行化学反应制备纳米材料是近十几年发展起来的新方法 ,该方法由于具有实验装置简单、易于操作和粒度可控等优点而引起人们的重视 [2 ] .微乳液是一种高度分散的间隔化液体 ,水 (或油 )相在表面活性剂 (助表面活性剂 )的作用下以…     

17R4/F127混合水溶液的凝胶结构

结合流变学频率扫描和同步辐射小角X射线散射(SAXS),研究了17R4(PO14-EO24-PO14)含量和温度对17R4/F127(EO99-PO65-EO99)混合水溶液凝胶结构的影响.结果表明,溶胶、软凝胶和硬凝胶分别对应无序结构、无序与立方相共存结构以及立方相结构.对于F127水溶液体系,可以将F127形成的胶束看作硬球,随着温度的升高,胶束的硬球半径和胶束中F127链的聚集数随之减小,这是因为17R4在较低温度下很难形成胶束,当温度升高时,17R4链参与胶束的形成,从而使胶束数目增加,因此每个胶束中的F127链数也随之减小.当17R4含量较高时,胶束外壳中F127部分的PEO链段数随着温度升高而减小,胶束外壳变得更软,因此,当17R4/F127摩尔比为2∶1时,混合溶液在高温下呈现面心立方(fcc)到体心立方(bcc)的结构转变.     

固-液界面可聚合脂多层膜的Ｘ射线散射研究

报道在北京同步辐射装置上有关固-液界面的研究结果,在漫散射站成功实现了固-液界面的X射线散射测量.将二乙炔酸的异丙醇溶液滴在硅基底表面,溶剂挥发后形成晶态二乙炔酸多层膜.X射线在位观测实验表明,和水长时间接触后,水分子渗透到多层膜亲水界面,样品呈液晶态.在大尺度上分子膜的热起伏符合液晶的线性弹性理论模型,但小尺度上分子的位移主要由缺陷引起.光照聚全后分子膜的弯曲模量变大,缺陷引发的分子位移范围也增大.     

上海光源在生命科学和高分子材料中的应用

<正>当代生命科学的主要研究目标是分子生物学,这是自从20世纪50年代DNA双螺旋结构被发现开始的。遗传信息由DNA通过RNA传向蛋白质("中心法则")这一规律的发现,极大地促进了生命科学的发展。1990年,由美国发起了人类基因组计划,这一计划的目标是:测出人体基因组中包含     

金属纳米颗粒-聚电解质多层膜的X射线反射率研究

用静电自组装技术制备了不同层数的Au纳米颗粒-聚电解质多层膜,用X射线反射及原子力显微镜对膜的微结构进行了表征.研究发现,当Au纳米颗粒下面的聚电解质层较薄时,膜中无清晰的界面结构;随着Au纳米颗粒下面的聚电解质层的增厚,金属-聚电解质多层膜的界面变得越来越清晰.     

Small-angle X-ray analysis of the effect of grain size on the thermal damage of octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7 tetrazocine-based plastic-bounded expolsives

The microstructure evolution of plastic-bonded explosives(PBXs) after thermal stimulus plays a key role in PBX performance. In this paper, the nanoscale pores of thermal-treated octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine(HMX)-based PBXs with different HMX particle sizes [approximately 40(FHP) and 100 μm(LHP)] were measured using smallangle X-ray scattering(SAXS). No obvious pore variations were found in the LHP samples heated at 160℃ for 6 h,whereas the amount of pores of FHP decreased when subjected to 160℃ for 6 h. At 180℃, the average pore radii of FHP and LHP decreased from approximately 45 nm to 25 nm, and the total pore volume increased distinctively because of phase transformation. The LHP sample reached a high level of pore content after being held at 180℃ for 1 h, whereas FHP required 3 h. Both FHP and LHP had relatively high pore volumes when subjected to 200℃ for 1 and 3 h.