X射线衍射样品的处理方法

X射线衍射分析法用于晶态物质的物相定性分析时,某一物相衍射峰的强度和数量与它的含量和结构有关.当某些物相含量较少时,它的衍射峰强度低,衍射峰数量也较少,查索引和核对衍射卡片,不易准确地判断.利用它们不同的化学和物理性质,对物相含量较少的矿物进行富积,再作衍射图,能够得到物相较完整的衍射图,是准确地进行物相分析的有效方法.笔者在实际工作中,根据样品的具体情况,用不同的处理方法进行样品富积,效果很好,现介绍如下:     

利用Rietveld方法Y_2O_3稳定ZrO_2的定量相分析

利用多相混合物中某相的重量与它在Rietveld结构修正中求得的标度因子之间的关系，可以进行多相混合物的定量分析[1].本工作利用Rietveld修正和X射线步长扫描衍射数据对不同浓度Y2O3掺杂的ZrO2试样进行了相含量的定量分析，给出了各相含量的定量数据，同时还证实了由研磨引起四方相向单斜相转变的规律.     

多晶材料X射线衍射无标样定量方法

Ｘ射线物相定量的结果对多晶样品的结构和织构十分敏感．一般的Ｘ射线定量方法都需要在样品中添加标样并均匀混合研磨，因而容易引起很大的误差．近年来，无标样Ｘ射线定量方法得到了很大的发展．无标样定量方法克服了一般有标样Ｘ射线定量方法需要混合研磨和手续烦复的缺点．本文总结了三类ｘ射线衍射无标样定量方法：理论参数计算法、全谱图拟合法以及联立方程法．给出了提高各种无标样法定量精度和可靠性的方法．     

锌铝基镁铅合金块状固体的物相组成和质量分数标定

X射线衍射技术的应用范围非常广泛,现已渗透到物理、化学、材料科学以及各种工程技术科学中,成为一种重要的分析方法.通过对金属合金试样的X射线衍射实验,利用MDI Jade软件以及K值法、绝热法、RIR值等理论方法对试样中的各个物相进行了成分鉴定(物相定性分析),计算出了试样中各物相所含质量分数的近似值(物相定量分析),并对实验数据的误差进行了分析.     

利用Rietveld方法Y2O3稳定ZrO2的定量相分析

利用多相混合物中某相的重量与它在Ｒｉｅｔｖｅｌｄ结构修正中求犁标度因子之间的关系，可以进行多相混合物的定量分析，本工作利用Ｒｉｅｔｖｅｌｄ修正和Ｘ射线步长扫描衍射数据对不同浓度Ｙ２Ｏ３掺杂的ＺｒＯ２试样地相含量的定量分析，给出了各相含量的定量数据，同时还证实了由研磨引起主相向斜相转变的规律。     

Y_2SiO_5:Eu~(3+)纳米荧光粉的光谱特性研究

用凝胶燃烧法制备Y2SiO5:Eu3+纳米荧光粉.X射线衍射实验发现,在1 100℃以下烧结得到X1型物相,属单斜晶系,空间群为P21/c;在1 300℃以上烧结得到X2型物相,属单斜晶系,空间群为C2/c.研究了各样品的红外光谱,发现同物相的校正面积和校正高度随颗粒增大而增大,在物相转型时发生突变,X2型吸收峰位发生蓝移;研究了室温下样品在395 nm紫外光激发下得到的发射光谱,发现纳米荧光粉的5D0→7F0峰相比体材料发生蓝移,5D0→7F2峰相比于体材料中心位置变化不大,而谱带明显加宽.随着烧结温度降低,荧光粉颗粒减小,5D0→7F2的跃迁峰强度回落,但5D0→7F1与5D0→7F4的跃迁峰强度变化不大.Eu3+在Y2SiO5基质中占有两个不同的格位,不同的能级产生两套光谱致使峰数比退简并的峰数多.     

X射线衍射全谱拟合法测定矿物药朱砂中硫化汞和二氧化硅的含量

为探索矿物药朱砂中硫化汞和二氧化硅含量快速准确的检测分析方法,利用X射线衍射全谱拟合法对3种朱砂样品进行定量分析,将所得结果与热分析法进行对比.结果表明X射线衍射全谱拟合法既能对朱砂真伪进行鉴别,又可快速准确地计算矿物药朱砂中的各物相成分.     

X射线衍射法测定MoO3在γ-Al2O3表面的最大单层分散量

对MoO3在γ-Al2O3表面的分散进行了测定。晶相MoO3与载体γ-Al2O3充分混合后，在低于MoO3熔点的适当温度下培烧。当MoO3的含量低于某一数值时，MoO3晶相的X射线衍射峰完全消失，MoO3的含量高于该数值时，晶相峰并不消失，但强度减弱。用X射线衍射可测定培烧后的残余晶相量，进而可得到MoO3在γ-Al2O3表面的最大分散度数值。此研究方法也可用于其它化合物在载体表面的最大分散量的测定。     

物相定量分析在铝工业中的应用

总结介绍了到目前为止在铝工业中应用的物相定量分析方法,分析了各种方法的应用范围以及优缺点,包括化学物相定量法、外标法、化学物相计算法、X射线衍射增量法、K值法、绝热法、Rietveld全谱拟合定量法、K值法和化学物相计算法结合以及Zevin无标定量法等.结果表明:每种物相定量分析方法都有各自的优点和缺点,需要根据样品的...     

离子束外延制备GaAs:Gd薄膜

室温条件下,用低能离子束外延制备了GaAs：Gd薄膜,X射线衍射(XRD)结果表明除了GaAs衬底峰没有发现其它新相的衍射峰,并借助于高分辨X射线衍射(HR-XRD)进一步分析了晶格常数的变化特点。俄歇电子能谱(AES)分析了样品表面的成分,及元素随深度的分布规律,在60nm深处元素的相对含量发生明显改变,运用原子力显微镜(AFM)揭示了样品表面的形貌特点。     

有限混合体模型上的自动模型选择:一种崭新的数据建模方式

在数据建模和分析中,有限混合体模型被广泛地使用着。然而,如何仅仅针对一组来自于某个有限混合体模型的数据选择出分量或聚类的个数则依然是一个非常困难的问题。由于分量个数是混合体模型的规模度量,其选择问题被称为有限混合体的模型选择问题。最近,针对有限混合体模型,特别是高斯混合模型,一种自动模型选择学习机制逐步发展成熟起来。这种新的机制能够在学习参数的过程中自动地完成模型选择,为数据的建模与分析提供了一种新的思路与途径。本文将对于高斯混合模型或一般有限混合体模型的自动模型选择学习算法及其典型应用进行综述与总结。首先,我们综述了基于贝叶斯阴阳机和谐学习原则的自动模型选择学习算法。然后,我们描述了另一种基于熵惩罚的自动模型选择学习算法。最后,我们给出了自动模型选择学习算法的一些典型的应用。     

The determination of the second and third virial coefficients frompVT-X data of binary systems

The compressibility factor of multicomponent systems can be obtained in terms of virial coefficients of the pure components and their binary mixtures. This paper concerns a method with which, for that purpose, the second and third virial coefficients for these binaries have been determined from experimental data. From useful data, second and third virial coefficients are obtained as a quadratic function of the temperature. The density domain for which these results are applicable is discussed. When ample data are available, results for a sample mixture can be obtained in a straightforward manner. Nevertheless, it is shown that under much less favorable conditions—sometimes even when pure-component data are lacking—fairly good results can still be obtained. In that case, the choice for an appropriate combining rule has to be considered carefully. Finally, the involvement of ternary mixture data, both obtained experimentally and predicted by the equation, is considered.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Pool boiling of ammonia/water and its pure components: Comparison of experimental data in the literature with the predictions of standard correlations

Although ammonia/water has been used for decades as a working pair in absorption cycles for industrial refrigeration, very limited data are available on boiling heat transfer of this mixture. The intention of this work is to carry out a bibliographic revision of the information available in the open literature about nucleate pool boiling of the ammonia/water mixture and its pure components. The experimental data have been compared with existing prediction correlations for the pure components and also for their mixtures.For water, all the pure component pool boiling correlations gave similar predictions and were in good agreement with experimental data. For ammonia the prediction of the correlation and the experimental data showed more differences.At a given heat flux, the experimental data show that the mixture pool boiling heat transfer coefficient is lower than that obtained with pure components. Three of the well-known correlations for mixtures were compared against the experimental data. None of these correlations provided a good prediction of the mixture pool boiling heat transfer coefficient over a wide range of mass fraction. Furthermore, a new correlation has been proposed.     

质谱定量分析方法的探讨及应用研究

建立了一套在气样室内气样压强低于700Pa时均可满足“分子流进样”条件的质谱校准与定量分析系统。通过大量的实验，确定了四极质谱计的工作参数；测定了常用被分析气体的定量系数；并采用实时校准的办法，利用标准气样标定了本装置的系统误差；对各类荧光灯中混合型填充气体的配比和国内外成品荧光灯中的杂质气体含量进行了质谱定量分析；测定了生产中未充入填充气体的灯管内的残气压强。取得了一批对指导生产、改进工艺有用的数据。本系统同样也适用于其他类似场合。     

钴玻璃熔片-X射线荧光光谱法测定铁矿石中各组分

使用混合熔剂、三氧化二钴与试样在高温中熔融制得钴玻璃熔片,以x荧光内标法分析铁矿石中各组分,并采用理论α系数法进行机体校正,得到了准确度较高的定量分析结果.应用于我单位铁矿石常规分析检测,效果理想.     

Investigation of flow properties of powders by means of a uniaxial tester, in relation to direct tablet compression

Unexpected poor flowability during commercial production of a direct compression tablet formulation initiated an investigation of the flow properties of the powder mixture and its components by means of a uniaxial tester. The failure function—a curve describing the strength of the powder bed as a function of the maximum main stress that has consolidated the bed—of the powder mixture and its components was determined. The drug was more cohesive than the filler, which was somewhat more cohesive than the powder mixture. Three excipients—a binder, a glidant and a lubricant—constituting 3.5 w/w% of the formulation improved the flowability of the mixture of active ingredient and filler. The failure function discriminated powder mixtures with poor flow from mixtures with medium or good flow. However, it was not possible to discriminate medium from good flow by means of the failure function. Attempts to correlate univariately the flow property parameters of the powder mixtures with particle size data or flow property data of included active ingredient and filler batches failed. Therefore a multivariate approach was tested. Principal component analysis (PCA) and projection to latent structures by means of partial least squares (PLS) were employed. An excellent PCA model was obtained with the flow properties of the powder mixture. A good PCA model of tableting performance—based on tablet weight variation and tablet machine speed—was obtained.     

Quantitative analysis of low-field NMR signals in the time domain

Two novel methods are described for direct quantitative analysis of NMR free induction decay (FID) signals. The methods use adaptations of the generalized rank annihilation method (GRAM) and the direct exponential curve resolution algorithm (DECRA). With FID-GRAM, the Hankel matrix of the sample signal is compared with that of a reference mixture to obtain quantitative data about the components. With FID-DECRA, a single-sample FID matrix is split into two matrices, allowing quantitative recovery of decay constants and the individual signals in the FID. Inaccurate results were obtained with FID-GRAM when there were differences between the frequency or transverse relaxation time of signals for the reference and test samples. This problem does not arise with FID-DECRA, because comparison with a reference signal is unnecessary. Application of FID-DECRA to 19F NMR data, which contained overlapping signals from three components, gave concentrations comparable to those derived from partial least squares (PLS) analysis of the Fourier transformed spectra. However, the main advantage of FID-DECRA was that accurate (<5% error) and precise (2.3% RSD) results were obtained using only one calibration sample, whereas with PLS, a training set of 10 standard mixtures was used to give comparable accuracy and precision.     

Structural,spectroscopic and biological investigation of copper oxides nanoparticles with various capping agents

Powder composed of copper oxides nanoparticles with various capping agents has been synthesized and characterized with the use of X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Polyvinyl alcohol (PVA), glycol propylene, glycerin and glycerin plus ammonia were used as capping agents. The scanning electron microscopy (SEM) studies showed that nanoparticles form agglomerates with the size from 80 to 120 nm while particles size determined from the XRD experiment was in the range from 7 to 21 nm. XPS and XRD experiments revealed that depending on capping and reducing agents used in the synthesis nanoparticles are composed of Cu₂O, CuO or a mixture of them. The biological activity test performed for a selected sample where the capping agent was glycerin plus ammonia has shown promising killing/inhibiting behavior, very effective especially for Gram negatives bacteria.     

Quantitative spectroscopic analysis of heterogeneous mixtures: the correction of multiplicative effects caused by variations in physical properties of samples

Spectral measurements of complex heterogeneous types of mixture samples are often affected by significant multiplicative effects resulting from light scattering, due to physical variations (e.g., particle size and shape, sample packing, and sample surface, etc.) inherent within the individual samples. Therefore, the separation of the spectral contributions due to variations in chemical compositions from those caused by physical variations is crucial to accurate quantitative spectroscopic analysis of heterogeneous samples. In this work, an improved strategy has been proposed to estimate the multiplicative parameters accounting for multiplicative effects in each measured spectrum and, hence, mitigate the detrimental influence of multiplicative effects on the quantitative spectroscopic analysis of heterogeneous samples. The basic assumption of the proposed method is that light scattering due to physical variations has the same effects on the spectral contributions of each of the spectroscopically active chemical components in the same sample mixture. On the basis of this underlying assumption, the proposed method realizes the efficient estimation of the multiplicative parameters by solving a simple quadratic programming problem. The performance of the proposed method has been tested on two publicly available benchmark data sets (i.e., near-infrared total diffuse transmittance spectra of four-component suspension samples and near-infrared spectral data of meat samples) and compared with some empirical approaches designed for the same purpose. It was found that the proposed method provided appreciable improvement in quantitative spectroscopic analysis of heterogeneous mixture samples. The study indicates that accurate quantitative spectroscopic analysis of heterogeneous mixture samples can be achieved through the combination of spectroscopic techniques with smart modeling methodology.     

Crystal structure of CaNi5H using x-ray diffraction with in situ hydriding

The crystal structure of the lowest hydrogen content hydride in the CaNi₅ + H₂ system, with the approximate composition CaNi₅ H, has been determined from X-ray powder diffraction data obtained using an insitu hydriding process. The metal atom positions in the body centred orthorhombic cell were determined using integrated intensity data and a block-diagonal least squares refinement.