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。     

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。     

新建北京同步辐射小角X射线散射站的必要性

本文分析了同步辐射小角X射线散射的特点与应用、国内外现状及新建北京同步辐射小角X射线散射站的必要性与机遇。     

同步辐射二维小角X光散射实验装置的建立与应用

与一维小角散射实验法相比,二维小角X光散射实验法可用于研究非球对称的体系,即可探测物质中取向体系的颗粒度(或孔径)的变化、颗粒(或孔)形状的变化等信息.介绍了北京同步辐射装置二维小角X光散射实验设备的建造及所建立的分析方法,并用于研究不同活化剂条件下制备出来的沥青基活性炭纤维中孔分布的变化,得到了炭纤维中的孔的平均体积随活化剂中NH3含量的降低而变大的结论.     

用SAXS和XRD方法研究TiO2纳米颗粒微观结构

用溶胶-凝胶方法制备了TiO₂纳米样品,并对该样品在300℃到800℃温度区域进行了退火处理.应用同步辐射X射线粉末衍射(XRD)方法研究了经不同热处理温度的TiO₂纳米颗粒的结构相变.应用同步辐射小角X射线散射(SAXS)方法研究了TiO₂纳米颗粒的表面分形与界面特性.得到纳米颗粒粒度与退火温度的变化规律,讨论了表面界面特征与相变的关系. 关键词： X射线小角散射 X射线衍射 2纳米颗粒')" href="#">TiO₂纳米颗粒     

同步辐射SAXS技术在TATB含能材料微孔结构研究中的初步应用

TATB含能材料的微结构对该材料的感度等有明显的影响,因而对于材料的安全性有着特别重要的意义.小角X射线散射(SAXS)技术是一种分析物质微观结构的重要手段,应用SAXS分析技术可以获取材料中几纳米到几百纳米尺度范围的亚微结构信息.利用同步辐射作为X射线源对TATB钝感炸药进行了小角散射实验测量,获得了SAXS测量谱.对实验谱数据进行处理,可得到样品材料的颗粒分布及内部微孔大小等微结构参数.     

中子小角散射讲座：第三讲 中子小角散射在材料科学中的应用

X射线小角散射在材料科学中是分析物质结构的重要手段之一[1].由于中子吸收截面小,所以中子小角散射可以采用较大的厚块样品.长波长的冷中子,既可以避免X射线结晶学中的双布拉格衍射,又可以在较小的散射矢量Q范围内研究中子散射强度的分布.某些近邻元素(如 Al,Mg等),对X射线的散射能力几乎一样,而它们的中子散射振幅则是无规的.所以,中于小角散射又特别适宜研究相邻元素合金中的分凝现象.中子具有磁矩,能与磁性物质相互作用,产生磁的小角散射. 这里应当强调指出,所谓“小角”,是指小的散射矢量值,大小范围约为 其中da为样品中结构单元间…     

基于Kirkpatrick-Baez镜聚焦的X射线小角散射显微层析成像

X射线小角散射显微层析成像(SAXS-CT)是一种无损的结构表征技术,用于研究非均匀物质纳米结构信息及其空间分布;在上海同步辐射光源(SSRF)设计并搭建了基于Kirkpatrick-Baez(KB)镜聚焦的SAXS-CT成像系统,并选取毛竹和注塑聚乳酸样品进行实验验证。结果表明:该SAXS-CT成像系统的聚焦光斑尺寸可以达到20μm以下;对于毛竹样品,得到了其内部维管束和薄壁细胞的位置分布及散射差异,同时获取了内部纳米纤维的取向特点;对于注塑聚乳酸样品,发现其内部片晶结构具有分层分布特征,获取了片晶结构的分布图像以及长周期分布图像;实验结果验证了该SAXS-CT成像系统的可靠性及实用性。     

小角X射线散射实验数据的初步处理

介绍北京同步辐射装置(BSRF)小角X射线散射实验站实验数据的初步处理方法,即由成像板探测器检测到的散射信号转换成角度及其对应的强度数据的方法,并对数据转换过程中可能遇到的问题进行了详细的讨论.     

利用小角X射线散射技术研究组分对聚酰亚胺/Al2O3杂化薄膜界面特性与分形特征的影响

采用溶胶-凝胶方法制备无机纳米杂化聚酰亚胺(PI),应用同步辐射小角X射线散射(SAXS)方法研究不同组分杂化PI薄膜的界面特性与分形特征.研究结果表明:散射曲线不遵守Porod定理,形成负偏离,说明薄膜中有机相与Al₂O₃纳米颗粒间存在界面层,界面层厚度在0.54 nm到1.48 nm范围内;随无机纳米组分增加,界面层厚度增加,有机相与无机相作用变强;无机纳米颗粒同时具有质量分形和表面分形特征,其分布、集结是一种非线性动力学过程;随组分增加,其质量分形维数降低 关键词： 小角X射线散射 纳米杂化 聚酰亚胺 界面     

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.     

The application of hybrid pixel detectors for in‐house SAXS instrumentation with a view to combined chromatographic operation

This study analyses the potential for laboratory‐based size‐exclusion chromatography (SEC) integrated small‐angle X‐ray scattering (SAXS) instrumentation to characterize protein complexes. Using a high‐brilliance home source in conjunction with a hybrid pixel X‐ray detector, the efficacy of SAXS data collection at pertinent protein concentrations and exposure times has been assessed. Scattering data from SOD1 and from the complex of SOD1 with its copper chaperone, using 10 min exposures, provided data quality in the range 0.03 < q < 0.25 Å^?1 that was sufficient to accurately assign radius of gyration, maximum dimension and molecular mass. These data demonstrate that a home source with integrated SEC–SAXS technology is feasible and would enable structural biologists studying systems containing transient protein complexes, or proteins prone to aggregation, to make advanced preparations in‐house for more effective use of limited synchrotron beam time.     

On the Supermolecular Structure of Fullerene C60 Solutions

Small angle X‐ray scattering (SAXS) and wide angle X‐ray scattering (WAXS) techniques were used for investigation of fullerene C₆₀ solutions in toluene and p‐xylene. On all SAXS curves, intensity decreases to some constant value of I_C with increase of scattering angle. The value of I_C depends on concentration non‐monotonically: it first slightly increases, then drops sharply to some minimal value, and then increases again. A qualitative explanation of such dependence is offered. It is supposed that the presence of fullerene C₆₀ in solution suppresses thermal fluctuations of density in the solvent. In combination with the X‐ray data the results obtained for solutions of fullerene C₆₀ by various others techniques (calorimetry, densimetry, etc.) are discussed. Possible models of a supermolecular structure of fullerene C₆₀ solutions in good solvents are considered.     

One‐dimensional small‐angle X‐ray scattering tomography of dip‐coated polyamide 6 monofilaments

A synchrotron study is presented in which the concept of one‐dimensional tomographic reconstruction of small‐angle X‐ray scattering patterns is applied to investigate polyamide 6 monofilaments, dip‐coated with alumina particles. The filaments are scanned with a focused synchrotron beam and the resulting scattering patterns are recorded with a PILATUS 2M detector. The reconstructed sequence of SAXS images reflects the local nanostructure variation along the filament radius. In particular, the influence of coating process parameters on the polyamide 6 is investigated.     

Thorough small‐angle X‐ray scattering analysis of the instability of liquid micro‐jets in air

Liquid jets are of interest, both for their industrial relevance and for scientific applications (more important, in particular for X‐rays, after the advent of free‐electron lasers that require liquid jets as sample carrier). Instability mechanisms have been described theoretically and by numerical simulation, but confirmed by few experimental techniques. In fact, these are mainly based on cameras, which is limited by the imaging resolution, and on light scattering, which is hindered by absorption, reflection, Mie scattering and multiple scattering due to complex air/liquid interfaces during jet break‐up. In this communication it is demonstrated that synchrotron small‐angle X‐ray scattering (SAXS) can give quantitative information on liquid jet dynamics at the nanoscale, by detecting time‐dependent morphology and break‐up length. Jets ejected from circular tubes of different diameters (100–450 µm) and speeds (0.7–21 m s^?1) have been explored to cover the Rayleigh and first wind‐induced regimes. Various solvents (water, ethanol, 2‐propanol) and their mixtures have been examined. The determination of the liquid jet behaviour becomes essential, as it provides background data in subsequent studies of chemical and biological reactions using SAXS or X‐ray diffraction based on synchrotron radiation and free‐electron lasers.     

New agitated and thermostatized cell for in situ monitoring of fast reactions by synchrotron SAXS

A thermostatized and agitated sample cell for synchrotron small‐angle X‐ray scattering (SAXS) measurements of liquid samples (homogeneous or heterogeneous) has been developed. The cell is composed of a compact main body with inlet and outlet windows for the beams of light. The volume of the cell is approximately 0.8 ml and the distance between the windows is 5 mm to allow accurate SAXS measurements. The cell is thermostatized by means of a jacket that surrounds the sample holder and it is connected to a thermostatic bath. In addition, the cell has a top and a bottom lid that allow easy cleaning and maintenance without demounting the optical windows. The cell has been used to run SAXS measurements of liquid samples and, for the first time, a mini‐emulsion polymerization reaction has been monitored by SAXS.     

The stopped‐drop method: a novel setup for containment‐free and time‐resolved measurements

A novel setup for containment‐free time‐resolved experiments at a free‐hanging drop is reported. Within a dead‐time of 100 ms a drop of mixed reactant solutions is formed and the time evolution of a reaction can be followed from thereon by various techniques. As an example, a small‐angle X‐ray scattering study on the formation mechanism of EDTA‐stabilized CdS both at a synchrotron and a laboratory X‐ray source is presented here. While the evolution can be followed with one drop only at a synchrotron source, a stroboscopic mode with many drops is preferable for the laboratory source.     

X光高分辨探测用CsI(Tl)晶体的蒙特卡罗模拟研究

提出了一种基于CsI(Tl)闪烁晶体和面阵CCD器件、采用光纤和光纤面板进行光耦合及传输、以扇形束线阵扫描方式实现对X光高分辨探测的方案。CsI(Tl)晶体的尺寸大小将直接影响到晶体的发光效率及X光的高分辨探测,据此开展了蒙特卡罗模拟研究。模拟研究了X射线能量、X射线源到探测晶体的距离(源距)、CsI(Tl)晶体的厚度与X射线能量分布、全能峰效率与CsI(Tl)闪烁晶体转换效率之间的关系。结果表明,当X射线能量为120~450 keV,CsI(Tl)晶体尺寸厚度为0~1.5 cm变化时,全能峰效率的变化范围为31.34~96.74%,CsI(Tl)闪烁晶体的转换效率的变化范围为12.8~97.43%。可见,X射线的能量及CsI(Tl)闪烁晶体尺寸的厚度,是决定X光高分辨探测的重要参量,这对优化X光高分辨探测用CsI(Tl)晶体的尺寸设计具有一定的参考价值。     

Synchrotron radiation refraction topography for characterization of lightweight materials

The employment of synchrotron radiation for refraction topography of materials has considerable advantages over standard x‐ray sources. The much higher beam intensity and the parallel and monochromatic radiation provide faster measurements and better angular and spatial resolution. X‐ray refraction techniques image the inner surface and interface concentration of micro‐structured materials. This effect of x‐ray optics is additional to small‐angle scattering by diffraction, when the scattering objects reach micrometre dimensions. We have developed x‐ray refraction techniques within the last decade in order to meet the growing demands for improved non‐destructive characterization of high‐performance composites, ceramics and other low‐density materials. Sub‐micron particle dimensions, the pore size of ceramics, the crack density distribution and single fibre debonding within damaged composites can be measured and visualized by computer‐generated interface topographs. For this purpose investigations are now being performed at the new hard x‐ray beamline of the Federal Institute for Materials Research and Testing (BAM) at BESSY, Berlin. This BAMline provides monochromatic radiation of photon energies from 5 to 60 keV from a double multilayer and/or a double‐crystal monochromator. A separate instrument is dedicated to the further development and application of synchrotron radiation refraction (SRR) topography. Different from conventional small‐angle scattering cameras with collimating slits and pinholes, scattering angles down to a few seconds of arc are selected by a single‐crystal analyser, similar to a Bonse–Hart diffractometer. A 20 µm spatial resolution of the scattering micro‐structures is achieved by a CCD camera with a fluorescent converter. First SRR topographs of aircraft composites [carbon fibre‐reinforced plastics (CFRP), carbon fibre‐reinforced ceramics (C/C), metal matrix ceramics (MMC)] will be reported. Copyright © 2004 John Wiley & Sons, Ltd.