晶体X射线衍射实验的数据分析模式

针对粉末X射线衍射谱分析软件CSM的特点,利用CSM软件附带的用户程序库功能,实现了固溶体的物相分析和固溶度的定量计算,扩展了CSM软件的使用范围,提高了物相分析的准确程度.     

X-ray diffraction analysis for quasi-crystals under pressure

Abstract

X-ray diffration analysis under high pressure was performed on the icosahedral phase (I-phase) of an Al₈₀Mn₂₀ alloy and Al₆Li₃Cu alloy. The I-phase of an Al-Mn alloy was stable and there was no indication of phase transformations. In an Al-Li-Cu alloy, the I-phase underwent irreversible transformation successively to the amorphous state and the long-range ordered state. This is the first observation of the pressure-induced amorphization.     

劳厄对晶体衍射的发现

介绍了劳厄提出晶体衍射思想的科学背景及当时的实验过程,并探讨在劳厄发现晶体衍射的过程中其科学思想的形成及X射线晶体衍射的发现带给我们的启示及影响．     

X射线衍射的发现

简单介绍了埃瓦尔德(Ewald P P)、劳厄(von Laue M)和布拉格父子(Bragg W H及Bragg W L)在1912年发现X射线衍射方面的贡献．1911年埃瓦尔德在索末菲的指导下在慕尼黑大学从事博士论文研究，劳厄在与他的讨论中了解到晶格的平移周期与X射线的波长属于同一量级，因此想到在二维光栅的两个衍射方程组中再加一个类似的方程，就可以描述X射线在三维晶体中的衍射．在此假设的指导下，Friedrieh W和Knipping P在1912年4月开始用CuSO4后来用闪锌矿(立方ZnS)进行实验，很快就得到X射线衍射的证据．这不但证明了X射线的波动性，还确定了晶体的三维周期性．老布拉格在1912年夏得知这个消息，与他儿子小布拉格一道尝试用X射线的粒子性解释它，并由小布拉格在剑桥大学重复这个实验．根据衍射斑点的椭圆形状和从Pope与Below那里学到的晶格理论(由此得知ZnS具有面心立方晶格)，小布拉格将X射线在晶体中的衍射看作是X射线从一些晶格平面的反射，从而推导出著名的布拉格方程．布拉格父子开拓了X射线晶体结构分析这门新兴学科，从简单的无机化合物和矿物，逐渐发展到有机化合物和生物大分子．劳厄和布拉格父子分别强调慕尼黑和剑桥的优良科学环境对发现X射线衍射的重要性．鉴于埃瓦尔德在发现X射线衍射的作用及他后来在倒易格子及动力学衍射理论方面的贡献，不少晶体学家认为他也应获得诺贝尔物理奖．     

德拜对多晶X射线衍射的研究

简述了德拜的生平,回顾了他在多晶X射线衍射研究过程中所作的工作,并分析了他取得成功的因素,展现了他独特的人格魅力.     

推导圆孔夫琅禾费衍射光强分布的一种简便方法

由一维单缝衍射的振幅分布公式简便推导求得了圆孔夫琅禾费衍射的振幅及光强分布,并利用Mathematica通用数学软件对光强分布进行亮度模拟,从而得到相应的计算机衍射模拟图像.     

X光衍射实验的改进与校正

用X射线衍射仪做定量分析衍射实验，会出现因盖革计数器存在分辨时间而漏计的现象．为了简便地测定分辨时间，本文利用单层膜二次照射技术，导出了用来校正积分强度的近似公式，并与逐点校正法作了对比分析，二者符合很好．     

纪念劳厄发现晶体X射线衍射100周年

文章从劳厄发现晶体X射线衍射的前因后果谈起.劳厄的这个发现产生了两个新学科,即X射线晶体学和X射线光谱学.文章中还回顾了布拉格父子对开展这两个新学科研究所作出的卓越贡献,并略述了X射线晶体学所产生的深远影响.     

A system for doing low temperature-high pressure single crystal X-ray diffraction with a synchrotron source

Abstract

A new diamond anvil cell and a helium flow cryostat have been developed for X-ray diffraction on single crystals at low temperatures and high pressures using white radiation of a synchrotron beam. This novel instrument especially enables continuous change of temperature and pressure of the sample without any adjustment of alignment. Automatic search for diffraction peaks can be performed since less than 30 pm eccentricity can be maintained during the rotation of the cell in the cryostat and the rotation of the cryostat on the goniometer head. The minimum temperature reached is 46 K. Measurements of solid 4He at 11.8 GPa are presented which confirm the stability of the hcp phase on this isobar.     

基于XRD的晶体温度计的设计及其应用

在XRD衍射仪上搭建控温测温装置,扫描不同温度下的晶体衍射图谱,得到晶面间距随温度的变化关系,设计了基于XRD的晶体温度计.使用该温度计获得了VO2的相变温度.     

Temperature dependence of the stress transfer for thermal resistance polymer composites by X-ray diffraction

Temperature dependence of the stress transfer from the matrix resin to the incorporated fiber has been measured for poly(p-phenylene benzobisoxazole) (PBO) fiber/bismaleimide (BMI) resin composite by a novel X-ray diffraction method. At 120°C, stress transfer and tensile strength of the PBO/BMI composite are superior to that of the PBO/epoxy composite, due to the excellent thermal resistance and good mechanical property of BMI resins. The PBO/BMI composite possesses good adhesion and excellent mechanical properties at high temperature, which are suitable for thermal resistance applications.     

粉晶X射线衍射在矿物岩石学研究中的应用

文章简单介绍了粉晶X射线衍射在岩石矿物学研究中的主要应用.指出粉晶X射线衍射不仅在矿物的定性/定量分析、晶胞参数测定、类质同像研究、多型研究、有序/无序结构研究、岩组学研究等传统领域继续发挥着重要作用,在矿物结晶过程和相转变研究、矿物表面物相研究、矿物缺陷研究和矿物晶体结构测定等新领域也展现出广阔的应用前景.     

软X光谱学光子筛衍射特性的实验表征

 概述了谱学光子筛的设计原理,计算了其透射率,并对设计的软X光谱学光子筛的衍射模式在光学波段进行了模拟计算和实验表征。结果表明,这种新型色散元件具有良好的、与设计预期一致的单级衍射特性,3级及以上的高级衍射能被有效抑制。与传统的透射光栅和以前设计的单级衍射光栅相比,新设计的软X光谱学光子筛更易于实现自支撑,可望在极紫外和软X光谱测量过程中得到广泛应用。     

Fractal analysis of powder X-ray diffraction patterns

X-ray diffraction (XRD) patterns with broad background are commonly found in the characterization of materials with a certain degree of amorphicity, so the sharp intensity peaks associated with material phases are not well defined. This work used rescaled range (denoted by R/S) analysis, a method intended for fractal analysis of noisy signals, to characterize XRD patterns with broad background. It is found that XRD patterns with broad background are not random at all, but contain information on regularities expressed as autocorrelations of the intensity signal. Sol-gel alumina fired at different temperatures was used as an example to illustrate the applicability of the method. It is shown that fractal R/S analysis is able to locate angular regions that can be associated to ideal International Centre for Diffraction Data Powder Diffraction File (ICDD PDF) lines of diverse alumina phases.     

用X射线衍射仪验证康普顿效应的实验研究

充分利用多晶X射线衍射仪的衍射、单转、定时计数、叠扫等功能测量数据,采用3种实验测量方法验证了康普顿散射波长的位移公式,分析了不同测量方法对实验结果的影响.     

Precipitation in silicon wafers after high temperature preanneal studied by X-ray diffraction methods

We have investigated oxygen precipitation in Czochralski silicon wafers focusing on influence of nucleation temperature and high temperature pre-anneal during common three step treatment. Thick Si wafers were studied mainly by x-ray diffraction in Laue transmission geometry using Mo x-ray tube, but were also compared to reciprocal space maps obtained in Bragg reflection geometry. The analysis of measured diffraction scans in Laue geometry was performed by means of Takagi equations and statistical dynamical theory of diffraction. From the simulated Laue diffraction curves we find the size of the individual defect area and the fraction of strain area volume in the wafer. The results obtained from x-ray diffraction were compared to loss of interstitial oxygen according to infrared absorption spectroscopy and the size of SiO₂ precipitate core was estimated. These techniques are in agreement with transmission electron microscopy images.     

Thickness measurement of GaN epilayer using high resolution X-ray diffraction technique

In this paper we propose a new method for measuring the thickness of the GaN epilayer, by using the ratio of the integrated intensity of the GaN epilayer X-ray diffraction peaks to that of the sapphire substrate ones. This ratio shows a linear dependence on the GaN epilayer thickness up to 2 μm. The new method is more accurate and convenient than those of using the relationship between the integrated intensity of GaN epilayer diffraction peaks and the GaN thickness. Besides, it can eliminate the absorption effect of the GaN epilayer.     

In-situ high pressure X-ray diffraction studies of orthoferrite SmFeO_3

The high-pressure behaviors of SmFeO3 are investigated by angle-dispersive synchrotron X-ray powder diffraction under a pressure of up to 40.3 GPa at room temperature. The crystal structure of SmFeO3 remains stable at up to the highest pressure. The different pressure coefficients of the normalized axial compressibility are obtained to be βa = 0.60 × 10-3 GPa-1,βb = 0.79 × 10-3 GPa-1, βc = 1.28 × 10-3 GPa- 1, and the bulk modulus （B0） is determined to be 293（3） GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. Furthermore, the larger compressibility of the FeO6 octahedra suggests the evolution of the orthorhombic structure towards higher symmetry configuration at high pressures.     

Residual stress/strain analysis in thin films by X-ray diffraction

Residual stresses are found in the majority of multilayer thin film structures used in modem technology. The measurement and modeling of such stress fields and the elucidation of their effects on structural reliability and device operation have been a “growth area” in the literature, with contributions from authors in various scientific and engineering disciplines.

In this article the measurement of the residual stresses in thin film structures with X-ray diffraction techniques is reviewed and the interpretation of such data and their relationship to mechanical reliability concerns are discussed.     

Surface X-ray diffraction study of boron-nitride nanomesh in air

The hexagonal boron-nitride ‘nanomesh’ surface reconstruction on Rh(1 1 1) [Corso et al., Science 303 (2004) 217-220] has been investigated using surface X-ray diffraction utilizing synchrotron radiation. This unique structure has been found to be stable under ambient atmosphere which provides an important basis for technological applications like templating and coating. The previously suggested (12 × 12) periodicity of this reconstruction has been unambiguously confirmed and structural features are discussed in the light of the X-ray diffraction results.