X射线多重衍射效应

本文介绍Ｘ射线多重衍射效应的起因，多重衍射图谱的指标化，给出了用普通Ｘ射线粉末衍射仪观测多重衍射效应的方法，并简要说明了多重衍射效应的应用。     

硫化锌纳米粒子的X射线衍射研究

利用X射线衍射技术对硫化锌纳米粒子进行了测试分析,详细研究了X射线衍射过程中扫描狭缝、接收狭缝、电压、电流、扫描速度及步长等参数对产物衍射峰的影响,优化出适合硫化锌纳米粒子的最佳测试参数,并利用最佳的X射线衍射曲线对产物进一步深入分析,获得硫化锌纳米粒子的粒径和晶格参数等信息,为X射线衍射技术在纳米材料领域的应用提供了实例。     

EDXRD安检系统衍射谱数据库的仿真研究

能量色散X射线衍射(EDXRD)系统在安检领域具有重要的应用前景。基于能量色散X射线衍射原理,以ICDD-JCPDS数据作为初始能谱信息,分析了X射线光源、系统结构、探测器分辨率及物质衰减效应对衍射能谱的影响,建立了与系统特性相对应的衍射谱仿真模型。利用该模型,仿真了不同结构参数EDXRD系统的衍射谱,仿真谱和实际测量结果吻合。在此基础上,仿真了海洛因和NH_4NO_3在不同晶体结构下的衍射能谱,为EDXRD安检系统的识别数据库提供了一种有效的构建方法。     

X射线衍射技术在材料分析中的应用

X射线衍射分析技术是一种十分有效的材料分析方法,在众多领域的研究和生产中被广泛应用。介绍了X射线衍射的基本原理,从物相鉴定、点阵参数测定、微观应力测定等几方面概述了X射线衍射技术在材料分析中的应用进展。     

利用晶体多重衍射进行同步辐射光子能量标定

介绍了多重衍射的基本原理,包括多重衍射的指标化、衍射光强度的计算和入射光方向的确定,并根据晶体多重衍射现象提出了入射X光能量的标定方法.从理论上讲,使用该标定方法在角度扫描精度为1"时,光子能量标定精度可达到1 eV.在上海光源14B衍射光束线上对提出的标定方法进行了实验验证,在10 keV处用Si(111)为主衍射收...     

小角度X射线衍射法研究夹层复合材料和长程有机大分子材料

对具有大层间距的累托石-尼龙夹层复合材料和具有长周期有序排列的脂质材料等进行了小角度X射线衍射分析。结果表明,通过调整X射线衍射仪的光路系统,适当控制入射X射线和散射线的强度,即使在极小的角度区域范围内,仍可清晰地分辨X射线衍射峰。对于日本理学D Max -rB型转靶X射线衍射仪,使用如下的光路系统:DS =1 2°,SS =1 6°,RS =0 .15mm ,可获得清晰结果。     

粉末衍射分析在石油化工领域中的应用

简要介绍了X射线衍射分析在石油化工领域中的应用，包括未知物物相鉴定，催化研究和聚合物结构参数测定等。     

水泥熟料X射线定量物相分析方法的对比研究

对水泥熟料物相定量分析的常规X射线衍射法（外标法和重叠峰自清洗法）与X射线全谱拟合法的分析结果进行了对比分析,结果表明,虽然外标法的重叠峰自清洗法对于水泥熟料的物相定量分析是可行的,但其结果的准确性往往不够理想;全谱拟合法由于最大限度地克服了常规X射线衍射存在的纯标样制备难,以及微吸收、择优取向、衍射峰重叠等问题,操作更为简便,分析结果具有更高的准确性。     

粉末X射线衍射用多功能附件的功用及其原理

标题所示附件是迎合粉末X射线衍射用多功能XMF数学模型的需要而研制的,故而得名,该多功能附件是与主机二维广角X射线衍射仪配套使用的。适合于粉末及固体薄膜等多晶材料的定性、定量、剖面、取向/织构分析,多晶及单晶体取向测定等;同时兼顾表面反射和透过反射等多种方式。这套附件具有构造简单、功能多样、分析结果直观等优点,可以作为“附件”完善现有衍射设备使其升级并具有多种新功能,也适合厂家生产构造合理、功能多样的三维(圆)X射线衍射设备。本文概要介绍其结构、原理及其功用。     

同步辐射高分辨率衍射光束线的设计

介绍了第三代同步辐射高分辨率X射线衍射光束线的总体设计。给出了高分辨率衍射的基本原理并描述了获得确定光子能量的近平行高强度X射线光束线所必需的光学元件。特别是用X射线动力学理论,解释了双晶及四次反射晶体单色器。作为一个实例,介绍了将于2009年开始在德国汉堡运行的一个新的同步辐射源PETRAⅢ的高分辨率衍射(HighRes)光束线的设置情况。通过优化光学部件,对微米尺寸光束,q空间的分辨减小到Δq=10^-5 nm^-1,光通量大于10¹¹ cts/s。     

论晶体或粉末的物相分析

介绍一种用先进的X射线衍射仪对晶体或粉末样品进行物相分析的方法，对科研及常规鉴别试验工作具有较高的推广价值。     

Electron crystal structure analysis of small organic molecules

Electron crystallography of small organic molecules, i.e., electron diffraction crystal structure analysis, has been long recognized to possess definite advantages over neutron and x-ray diffraction techniques for the investigation of microcrystalline preparations. Quantitative application of the technique to real structural problems, on the other hand, had been hindered initially by an inadequate theoretical model. Yet, as demonstrated in this review of the methodology, the adequate recognition of limiting factors due to n-beam dynamical scattering and crystal deformation permits design of optimal diffraction experiments which yield intensity data suitable for ab initio structure analysis. Representative crystallographic analyses discussed here underscore the utility of this technique as a probe of organic molecular structure at atomic resolution.     

Rapid qualitative phase analysis in highly textured thin films by x-ray diffraction

Phase analysis of highly out-of-plane textured specimens using x-ray diffraction is usually complicated due to the disappearance of most of the x-ray peaks in a common theta/2 theta diffraction geometry. In this paper, we propose a technique, where powderlike spectra of textured samples are obtained by multiaxial x-ray diffraction scans. This technique is a simple, yet powerful method which allows for significant improvement in thin film characterization and provides several types of information about the samples, such as the rapid qualitative identification of phases using common powder x-ray diffraction spectra databases, texture distribution, and quantitative residual stress analysis.     

用于太空望远镜的大口径薄膜菲涅尔衍射元件

为了满足空间衍射成像系统对大口径、轻量化衍射元件的需求,设计制作了直径为400mm的聚酰亚胺(PI)薄膜菲涅尔衍射元件。通过紫外光刻、离子束刻蚀等微细加工方法在石英基底上制作衍射图形,然后将衍射图形复制到PI薄膜上得到菲涅尔衍射型薄膜元件。结合有限元法探究了薄膜复制过程中热应力的变化规律及降低热应力的方法,分析了影响薄膜衍射效率的因素及薄膜制作误差、温度变化对薄膜成像的影响,最终实现了大面积薄膜与基底的分离,并通过局部氧气等离子体轰击提高了薄膜衍射效率的均匀性。经测试,薄膜菲涅尔衍射元件的厚度约为20μm,在波长633nm处的实际衍射效率平均值为33.14%,达到了理论效率的81.83%,衍射效率的均方根值RMS=0.01。实验结果表明,通过紫外光刻、离子束刻蚀和薄膜复制的方法可以得到大口径、高衍射效率的薄膜菲涅尔衍射元件。     

Beyond the crystallization paradigm: structure determination from diffraction patterns from ensembles of randomly oriented particles

We amplify on the principles of the method we have recently proposed for recovering an oversampled diffraction pattern of a single particle from measured diffraction patterns from multiple particles in orientations related by rotation about an axis parallel to the incident radiation. We propose an alternative method of phasing a reference resolution ring by means of a non-negativity constraint on the diffraction intensities, point out the need for caution about enantiomeric ambiguities in the reconstruction of a diffraction pattern from its angular correlations, and show that converged correlations may be deduced by appropriate averaging of even very noisy data.     

X-ray diffraction from shock-loaded polycrystals

X-ray diffraction was demonstrated from shock-compressed polycrystalline metals on nanosecond time scales. Laser ablation was used to induce shock waves in polycrystalline foils of Be, 25-125 microm thick. A second laser pulse was used to generate a plasma x-ray source by irradiation of a Ti foil. The x-ray source was collimated to produce a beam of controllable diameter, which was directed at the Be sample. X-rays were diffracted from the sample, and detected using films and x-ray streak cameras. The diffraction angle was observed to change with shock pressure. The diffraction angles were consistent with the uniaxial (elastic) and isotropic (plastic) compressions expected for the loading conditions used. Polycrystalline diffraction will be used to measure the response of the crystal lattice to high shock pressures and through phase changes.     

Diffraction effects and inelastic electron transport in angle‐resolved microscopic imaging applications

We analyse the signal formation process for scanning electron microscopic imaging applications on crystalline specimens. In accordance with previous investigations, we find nontrivial effects of incident beam diffraction on the backscattered electron distribution in energy and momentum. Specifically, incident beam diffraction causes angular changes of the backscattered electron distribution which we identify as the dominant mechanism underlying pseudocolour orientation imaging using multiple, angle‐resolving detectors. Consequently, diffraction effects of the incident beam and their impact on the subsequent coherent and incoherent electron transport need to be taken into account for an in‐depth theoretical modelling of the energy‐ and momentum distribution of electrons backscattered from crystalline sample regions. Our findings have implications for the level of theoretical detail that can be necessary for the interpretation of complex imaging modalities such as electron channelling contrast imaging (ECCI) of defects in crystals. If the solid angle of detection is limited to specific regions of the backscattered electron momentum distribution, the image contrast that is observed in ECCI and similar applications can be strongly affected by incident beam diffraction and topographic effects from the sample surface. As an application, we demonstrate characteristic changes in the resulting images if different properties of the backscattered electron distribution are used for the analysis of a GaN thin film sample containing dislocations.     

A systematic procedure for determining the chiral indices of multi-walled carbon nanotubes using electron diffraction--each and every shell

Electron diffraction technique has been developed and refined to establish a systematic procedure to determine the chirality (chiral indices) of each and every shell in a carbon nanotube. We have introduced a zoning scheme to sort the reflection layer lines from the multiple shells of a carbon nanotube. An application of the procedure is demonstrated as an example for an eleven-shell carbon nanotube whose chiral indices of each and every shell were determined unambiguously. The revealed structure of the carbon nanotube suggests that there is no strong correlation among the shells as the nanotube was formed. The limitations of the current method are also discussed.     

利用菲涅尔衍射测量微小尺寸

在科研工程实际中,对细丝、狭缝等微小尺寸的测量通常采用夫琅和费衍射法,因为衍射暗斑间距与被测尺寸之间具有很简单的函数关系:s=λL/d。理论上,夫琅和费衍射条件是相当苛刻的,即要求L>d~2/λ,在实际应用中,考虑到光源、传感器以及被测对象尺寸之间的匹配关系,往往很难实现。本文通过理论分析与实验数据充分证明,对于菲涅尔衍射,前述函数关系也能保持极为良好的近似,为仪器结构设计提供了极大方便,同时也为提高测量精度,扩展测量范围创造了有利条件。     

有机化合物X射线粉末衍射实验谱图和计算谱图的比较

对有机化合物的X射线衍射谱图和计算谱图之间的关系做观察和分析。得到的一些规律性认识,有助于有机化合物的物相鉴定和谱图质量的判断。