三氨基三硝基苯材料微孔结构的小角x射线散射实验研究

应用同步辐射x射线小角散射技术研究了不同工艺制备的三氨基三硝基苯样品中的微孔状况 ，得到了样品材料有关微结构参数，包括微孔平均孔径及孔径分布、分形特征、Porod常数 及界面参数等，并分析了微孔结构参数的变化规律.结果表明，不同工艺制备的TATB样品材 料其微孔结构有较大差别，都有较显著的特征. 关键词： 小角x射线散射 TATB材料微孔分布     

小角X射线散射应用研究若干进展

文章从小角X射线散射（small-ande X-ray scattering，SAXS）的理论分析出发，结合国内外SAXS理论和应用研究的最新动态，总结了文章作者所在的研究小组近年来在SAXS技术用于材料微结构表征方面的研究成果。主要包括以下三个方面的内容：（1）有机／无机杂化材料中电子密度波动的研究；（2）弦长度分布函数材料的周期结构的研究；（3）纳米粉末晶化过程的研究。     

小角X射线散射模糊数据解析方法

小角X射线散射(SAXS)是研究多孔材料结构的一种有效方法．可得到孔径分布、平均孔径、比表面、界面层厚度、分形维数等许多微结构信息．SAXS理论公式基于点状光源(针孔准直),但实践中则大多采用长狭缝准直条件．简要综述了SAXS在长狭缝准直条件下直接应用模糊强度进行煤、炭、二凝胶、分子筛等多孔材料结构解析的方法、并与针孔准直进行了对比。     

利用x射线小角散射技术研究微晶硅薄膜的微结构

采用x射线小角散射（SAXS）技术研究了由射频等离子体增强化学气相沉积（rf-PECVD）、 热丝化学气相沉积(HWCVD)和等离子体助热丝化学气相沉积(PE-HWCVD)技术制备的微晶硅（ μc-Si:H）薄膜的微结构.实验发现，在相同晶态比的情况下，PECVD沉积的μc-Si:H薄膜微 空洞体积比小，结构较致密，HWCVD沉积的μ-Si:H薄膜微空洞体积比大，结构较为疏松，PE -HWCVD沉积的μc-Si:H薄膜，由于等离子体的敲打作用，与HWCVD样品相比，微结构得到明 显改善.采用HWCVD二步法和PE-HWCVD加适量Ar离子分别沉积μc-Si:H薄膜，实验表明，微结 构参数得到了进一步改善.45°倾角的SAXS测量显示，不同方法制备的μc-Si:H薄膜中微空 洞分布都呈各向异性.红外光谱测量也证实了SAXS的结果. 关键词： 微晶硅薄膜 微结构 微空洞 x射线小角散射     

纳米团聚生长的多重分形谱

采用小角x射线散射（SAXS）方法，对两类具有代表性的纳米团聚的生长分形进行了表征.一 类为用化学方法 (水合肼溶液还原法) 制备的纳米金属Ni粉；另一类通过物理方法(纳米晶 化处理)，由非晶基体相中生长纳米晶相、形成非晶/纳米晶双相结构的Finemet (Fe_{73 .5} Cu₁Nb₃Si_13.5B₉) 合金.上述两 类材料的纳米团聚在生长过程中都存在 明显元素扩散迁移，形成在1—100 nm范围内的元素分布非均匀区域.这些元素分布的非均匀 区域具有多重质量生长分形特征，其尺度大小和分布方式对最终的材料的物理性能至关重要 .SAXS方法是表征这类具有分形生长特征的纳米团聚微观结构信息的强有力手段.从方法论的 角度详述了从SAXS测量到获得多重分形谱的处理过程，这一实验研究分析手段对于定量考察 纳米微结构形貌的生长机理和性能的其他研究课题有一定的帮助作用. 关键词： 纳米材料 分形生长 小角x射线散射 磁性材料     

小角x射线散射法研究氧化硅溶胶的制备环境依赖性

根据氧化硅溶胶的不同制备环境(如老化时间、酸碱性和溶剂种类等)，利用小角x射线散射( SAXS)技术，辅以动态光散射等方法，对氧化硅溶胶的界面性质和微结构进行比较性分析.发 现在碱或酸催化下氧化硅溶胶的SAXS结果表现出极大差异，用低分子有机酸作催化剂不仅可 以得到聚硅氧烷大分子，而且有机酸和正硅酸乙酯的酸解反应使溶胶形成内部结构很复杂的 颗粒悬浮体系.溶剂极性越大，则颗粒形貌越不规则.甲酸酸解得到的溶胶颗粒的硅氧四面体 形成程度是所有体系中最差的.发现了在水为溶剂时溶胶SAXS结果中不同寻常的正、负偏离 共存情况，并给出了相应的解释. 关键词： 小角x射线散射 氧化硅 溶胶_凝胶     

蠕变镍基单晶高温合金微观结构与界面特征的X射线小角散射研究

利用SAXS技术对蠕变过程中不同尺度范围的微观结构变化分析表明X射线小角散射(SAXS)与中子小角散射(SANS)测量的二维散射图具有明显的差异,由散射强度曲线的变化说明了蠕变过程中二次析出γ'相形貌和不同区域尺寸特征的改变情况.分析结果表明二次析出γ'相存在两类特征尺寸,在蠕变过程中沿[100]或[010]方向的变化趋势类似,均是在第一和第二阶段有所减小,在第三阶段又有所增大,相较而言,特征尺寸较大的γ'相变化也较为显著.二次析出γ'相在蠕变第二阶段元素扩散最严重,相表面最粗糙,在第三阶段两相界面又进一 关键词： 单晶高温合金 二次析出γ'相 X射线小角散射 微观结构     

北京同步辐射装置新建的X射线小角散射站投入运行

北京同步辐射装置（BSRF）是利用同步辐射光源进行科学研究的装置、对社会开放的大型公用科学设施，是我国凝聚态物理、材料科学、化学、生命科学、资源环境及微电子等交叉学科开展科学研究的重要基地。随着小角X射线散射（SAXS）用户的增长。BSRF原有的小角X射线散射站与X射线衍射站分时使用、共享489A光束线已远不能满足需求，广大用户强烈要求新建一条小角X射线散射站。     

小角X射线散射中宇宙线噪声去除方法

针对小角X射线散射（SAXS）测量图样中的宇宙线提出一种去除方法,以纳米结构的周期信息为物理先验计算得到周期性散射信号的坐标信息,对各光斑级次有效信号区域内的宇宙线进行检测并去除。数值模拟了含宇宙线的SAXS测量图样序列,测试该方法对SAXS测量图样序列宇宙线的检测和去除效果,并与现有的宇宙线去除方法进行对比。计算不同曝光时间下去噪前和各方法去噪后SAXS测量图样的评价指标,可以说明该方法对于SAXS测量图样中的宇宙线具有良好的去除效果,并能在长曝光条件下获得明显的信噪比增益。     

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     

我国同步辐射小角X光散射装置

小角X光散射是当X光照射到物质上时发生的在原光束附近小角度范围内的电子相干散射,凡是存在纳米尺度的电子密度不均匀区的物质均会产生小角X光散射现象,因此它是表征纳米、多孔材料结构的理想手段。普通X光源产生的X光强度弱,限制了小角X光散射的应用,采用同步辐射为X光源,则可以大大提高X光强度。目前我国已建立同步辐射小角X光散射站,本文对其装置进行了介绍。     

小角X光散射中干涉效应的判断与处理

小角X光散射是当X光照射到物质上时发生的在原光束附近小角度范围内的电子相干散射,凡是存在纳米尺度的电子密度不均匀区的物质均会产生小角X光散射现象,因此它是表征纳米、多孔材料结构的理想手段。SAXS中的有关理论一般仅适用于稀疏体系,对于密集体系,往往会产生干涉现象。本文简要总结了目前文献中有关干涉效应的判断与处理方法。     

Studies of intrawall porosity in the hexagonally ordered mesostructures of SBA-15 by small angle X-ray scattering and nitrogen adsorption

Ordered mesoporous silicas (OMSs) such as SBA-15 (p6mm symmetry group) synthesized in the presence of block copolymers containing poly(ethylene oxide) blocks possess irregular complementary pores in the walls of ordered mesopores. The X-ray scattering caused by this complementary porosity contributes to the background of the SAXS patterns. This work shows the possibility of using the SAXS data for the study of intrawall channels interconnecting ordered cylinders in SBA-15. The proposed SAXS analysis was tested by using a series of SBA-15 samples obtained at different temperatures of hydrothermal treatment (from 60 to 180 °C). The structural modelling of the SAXS patterns recorded for a series of SBA-15 samples was performed by using the continuous density function (CDF) technique in combination with the derivative difference minimization (DDM) method of full-profile refinement. This method is well suited for extraction of the background curves from the SAXS patterns. The resulting smooth background curves were analyzed by the well-known method in the SAXS theory used for evaluation of heterogeneity distributions, which in this case characterize the intrawall complementary porosity. A relatively good agreement has been observed between the data obtained by SAXS and nitrogen adsorption analysis. The SAXS analysis is sufficiently sensitive for examination of heterogeneous microporosity in SBA-15 materials. The average diameter of intrawall pores for the SBA-15 sample obtained at 60 °C was only about 1.4 nm. However, this diameter increased with the increasing temperature of hydrothermal treatment; namely, it was 1.5, 1.8, 2.6, 2.6, 3.5 and 5.2 nm for the SBA-15 samples hydrothermally treated at 80, 100, 120, 140, 160 and 180 °C, respectively.     

Amphiphilic diblock copolymers with adhesive properties: I. Structure and swelling with water

We study asymmetric block copolymers with the simple diblock AB architecture, in the case where the longer block A is both hydrophobic and “soft”, whereas the shorter block B is hydrophilic and “hard”. Materials with such a particular combination of physico-chemical and mechanical properties have distinctive advantages, in particular for designing water-compatible adhesive materials. The phase diagram is established, combining NMR and SAXS characterisations of the materials. The swelling with water is monitored through gravimetry and “time-resolved” SAXS. Indications of maintained adhesive properties in a wet environment are given.     

Simultaneous small‐ and wide‐angle scattering at high X‐ray energies

Combined small‐ and wide‐angle X‐ray scattering (SAXS/WAXS) is a powerful technique for the study of materials at length scales ranging from atomic/molecular sizes (a few angstroms) to the mesoscopic regime (～1 nm to ～1 µm). A set‐up to apply this technique at high X‐ray energies (E > 50 keV) has been developed. Hard X‐rays permit the execution of at least three classes of investigations that are significantly more difficult to perform at standard X‐ray energies (8–20 keV): (i) in situ strain analysis revealing anisotropic strain behaviour both at the atomic (WAXS) as well as at the mesoscopic (SAXS) length scales, (ii) acquisition of WAXS patterns to very large q (>20 Å^?1) thus allowing atomic pair distribution function analysis (SAXS/PDF) of micro‐ and nano‐structured materials, and (iii) utilization of complex sample environments involving thick X‐ray windows and/or samples that can be penetrated only by high‐energy X‐rays. Using the reported set‐up a time resolution of approximately two seconds was demonstrated. It is planned to further improve this time resolution in the near future.     

Software for the high-throughput collection of SAXS data using an enhanced Blu-Ice/DCS control system

Biological small-angle X-ray scattering (SAXS) provides powerful complementary data for macromolecular crystallography (MX) by defining shape, conformation and assembly in solution. Although SAXS is in principle the highest throughput technique for structural biology, data collection is limited in practice by current data collection software. Here the adaption of beamline control software, historically developed for MX beamlines, for the efficient operation and high-throughput data collection at synchrotron SAXS beamlines is reported. The Blu-Ice GUI and Distributed Control System (DCS) developed in the Macromolecular Crystallography Group at the Stanford Synchrotron Radiation Laboratory has been optimized, extended and enhanced to suit the specific needs of the biological SAXS endstation at the SIBYLS beamline at the Advanced Light Source. The customizations reported here provide a potential route for other SAXS beamlines in need of robust and efficient beamline control software. As a great deal of effort and optimization has gone into crystallographic software, the adaption and extension of crystallographic software may prove to be a general strategy to provide advanced SAXS software for the synchrotron community. In this way effort can be put into optimizing features for SAXS rather than reproducing those that have already been successfully implemented for the crystallographic community.     

Time-resolved SAXS measurements facilitated by online HPLC buffer exchange

Small‐angle X‐ray scattering (SAXS) is a powerful technique to structurally characterize biological macromolecules in solution. Heterogeneous solutions are inherently challenging to study. However, since SAXS data from ideal solutions are additive, with careful computational analysis it may be possible to separate contributions from individual species present in solution. Hence, time‐resolved SAXS (TR‐SAXS) data of processes in development can be analyzed. Many reported TR‐SAXS results are initialized by a sudden change in buffer conditions facilitated by rapid mixing combined with either continuous or stopped flow. In this paper a method for obtaining TR‐SAXS data from systems where the reaction is triggered by removal of a species is presented. This method is based on fast buffer exchange over a short desalting column facilitated by an online HPLC (high‐performance liquid chromatography) connected to the SAXS sample cell. The sample is stopped in the sample cell and the evolving reaction is followed. In this specific system the removal of phenol initiates a self‐association process of long‐acting insulin analogues. For this experiment, data were collected in time series while varying concentrations. The method can be generally applied to other systems where removal of a species or other changes in experimental conditions trigger a process.     

Performance on absolute scattering intensity calibration and protein molecular weight determination at BL16B1, a dedicated SAXS beamline at SSRF

The optical system and end‐station of bending‐magnet beamline BL16B1, dedicated to small‐angle X‐ray scattering (SAXS) at the Shanghai Synchrotron Radiation Facility, is described. Constructed in 2009 and upgraded in 2013, this beamline has been open to users since May 2009 and supports methodologies including SAXS, wide‐angle X‐ray scattering (WAXS), simultaneous SAXS/WAXS, grazing‐incidence small‐angle X‐ray scattering (GISAXS) and anomalous small‐angle X‐ray scattering (ASAXS). Considering that an increasing necessity for absolute calibration of SAXS intensity has been recognized in in‐depth investigations, SAXS intensity is re‐stated according to the extent of data processing, and the absolute intensity is suggested to be a unified presentation of SAXS data in this article. Theory with a practical procedure for absolute intensity calibration is established based on BL16B1, using glass carbon and water as primary and secondary standards, respectively. The calibration procedure can be completed in minutes and shows good reliability under different conditions. An empirical line of scale factor estimation is also established for any specific SAXS setup at the beamline. Beamline performance on molecular weight (MW) determination is provided as a straightforward application and verification of the absolute intensity calibration. Results show good accuracy with a deviation of less than 10% compared with the known value, which is also the best attainable accuracy in recent studies using SAXS to measure protein MW. Fast MW measurement following the demonstrated method also enables an instant check or pre‐diagnosis of the SAXS performance to improve the data acquisition.     

SAXS studies of blends of high- and low-density polyethylene

It is shown that in blends of PE having different melting temperatures the morphology depends drastically on the cooling rate. In these heterogeneous PE, the correlation relationship L = r between the long period L of the solid state and the dimension of the coils r in the liquid state is observed only in rapidly quenched materials. In slowcooled materials the SAXS spectra are interpreted in terms of segregation of two types of PE, on a scale of the order of the dimension of the coils, the arrangement of the crystalline lamellae being paracrystalline and statistical.