In this study, CeO2 nanowires–reduced graphene oxide hybrids (CeO2 NWs–RGO) were synthesized by a green hydrothermal method using CeO2 NWs and graphene oxide (GO) as raw materials. During the process of reduction of GO, hydrothermal condition with supercritical water provides thermal and chemical factors to synthesize RGO. The photocatalytic experimental results show that the CeO2 NWs–RGO hybrids exhibit enhanced photocatalytic activity for degradation of Rhodamine B (RhB) under UV-light irradiation. It is found that the degree of photocatalytic activity enhancement strongly depends on the mass ratio of RGO in the hybrids, and the remarkable photocatalytic activity is 20 times that of pristine CeO2 NWs when the loading amount of RGO is 8.0 wt%. The enhancement of photocatalytic activity can be attributed to the excellently elevated absorption ability for the dye through π–π conjugation as well as the effective inhibition of the recombination of photogenerated electrons because of the electronic interaction between CeO2 NWs and RGO sheets.

Cognitive deficits are repeatedly described with Pb exposure, but little is known about the distribution of lead in brain. To determine the local distribution of lead (Pb) and other trace elements, X-ray fluorescence spectroscopy measurements have been performed, using a microbeam setup and highest flux synchrotron radiation. Experiments have been carried out at ID-22, ESRF, Grenoble, France. The installed microprobe setup provides a monochromatic beam (16 keV) from an undulator station focused by Kirkpatrick-Baez X-ray optics to a spot size of 5 μm×3 μm. Brain slices from frontal cortex, thalamus, and hippocampus have been investigated (20 μm thickness, imbedded in paraffin and mounted on kapton foils). In general no significant increase in fluorescence intensities could be detected in one of the investigated brain compartments. Pb and other (trace) elements such as S, Ca, Fe, Cu, Zn, and Br could be detected in all samples and showed strong inhomogeneities within the analysed areas. While S, Ca, Fe, Cu, Zn, and Br could be clearly assigned to brain vessel structures (blood vessels, plexus choroidei), Pb was very inhomogeneously distributed. The local distribution of the detected elements in various brain structures will be discussed.

The usefulness of a high X-ray flux instrument to improve the accuracy of a powder diffraction pattern is demonstrated. In this case, very weak reflections of a well-characterized and well-known natural mineral can be detected by an often-used X-ray rotating anode diffractometer. High purity natural dolomite, CaMg(CO3)2, for example, was used to produce a slightly more comprehensive indexed X-ray powder diffraction. The powder pattern obtained in this study was compared with that of the reported high quality PDF pattern (36-426, with “*” mark) and that of a calculated pattern derived from single crystal structure data. A very weak 003 reflection at low angle and many weak reflections at high angles, not reported in the PDF pattern, were successfully identified using this high-power X-ray instrument. Unit cell parameters were determined to be a=4.8090±0.0001 Å and c=16.0182±0.0003 Å, which were in good agreement with the extant PDF pattern. Accuracy of the relative intensities between the measured and calculated patterns was apparently somewhat improved in this study, probably also attained through less preferred orientation and the higher purity of the sample used.

Two XRD specimen holders we designed for use with highly radioactive specimens are described. An injection mold was fabricated to allow inexpensive production of one of the holders. These holders are suitable for single-time use. The ease of use and disposable nature of this holder resulted in a dramatic reduction in personnel exposure and an uncontaminated diffraction unit. A second holder, based on the design of the first, is used to obtain XRD patterns from powders where preferred orientation is an issue and from clays. Both holders result in negligible background, since the specimen is essentially levitated in the X-ray beam. This is a benefit over other methods, such as collodion, that introduce significant background to the XRD pattern.

Kesterite-type compound semiconductors, containing copper and zinc, have photovoltaic properties depending on cation distribution in the crystal structure. Anomalous diffraction allows discrimination of isoelectronic cations, in principle allowing a straightforward determination of site occupation factors from data collected at multiple energies close to the X-ray absorption edges of copper and zinc. However, extremely strong correlation between structural parameters precludes this. We present a recipe based on the direct dependency between refined occupation factors and atomic scattering power, which allows to lift the correlations and to detect issues of individual diffraction patterns or assumptions in the model, thereby allowing for reliable quantitative analysis of the Cu/Zn distribution.

The General Structure Analysis System (GSAS)-II software package is a fully developed, open source, crystallographic data analysis system written almost entirely in Python. For powder diffraction, it encompasses the entire data analysis process beginning with 2-dimensonal image integration, peak selection, fitting and indexing, followed by intensity extraction, structure solution and ultimately Rietveld refinement, all driven by an intuitive graphical interface. Significant functionality of GSAS-II also can be scripted to allow it to be integrated into workflows or other software. For protein studies, it includes restraints on bond distances, angles, torsions, chiral volumes and coupled torsions (e.g. Ramachandran Φ/Ψ angles) each with graphical displays allowing visual validation. Each amino acid residue (and any ligands) can be represented by flexible rigid bodies with refinable internal torsions and optionally fully described TLS thermal motion. The least-squares algorithm invokes a Levenberg-Marquart minimization of a normalized double precision full matrix via Singular Value Decomposition providing fast convergence and high stability even for a large number of parameters. This paper will focus on the description of the flexible rigid body model of the protein and the details of the refinement algorithm.

An improved method to correct observed shift and asymmetric deformation of diffraction peak profile caused by the axial-divergence aberration in Bragg–Brentano geometry is proposed. The method is based on deconvolution–convolution treatment applying scale transform of abscissa, Fourier transform, and cumulant analysis of an analytical model for the axial-divergence aberration. The method has been applied to the powder diffraction data of a standard LaB6 powder (NIST SRM660a) sample, collected with a one-dimensional Si strip detector. The locations, widths and shape of the peaks in the deconvolved–convolved powder diffraction data have been analyzed. The finally obtained whole powder diffraction pattern ranging from 10° to 145° in diffraction angle has been simulated by the Pawley method applying a symmetric Pearson VII peak profile model to each peak with ten background, two peak-shift, three line-width, and two peak-shape parameters, and the Rp value of the best fit has been estimated at 4.4%.

As is well known from literature, the grinding process, which is an unavoidable step in sample preparation, may strongly modify the physical properties of chrysotile through amorphisation. The aim of this work is to establish the proper milling time to apply to the samples before an accurate X-ray powder diffraction quantitative analysis. We have used the RIR (reference intensity ratio) analytical method, based on the measurement of the ratio I/Is between the intensity of the strongest line of an analyte and the intensity of the analytical peak of a standard material, when they are thoroughly mixed 50:50 by weight. We have studied how the RIR value changes as a function of the milling time of the sample and how the accuracy of this quantitative method is affected.

The biaxial stress and thermal expansion of multilayer doped-aluminosilicate environmental barrier coatings were measured in situ during cooling using microfocused high-energy X-rays in transmission. Coating stresses during cooling from 1000 °C were measured for as-sprayed and thermally cycled samples. In the as-sprayed state, tensile stresses as high as 75 MPa were measured in the doped-aluminosilicate topcoat at 375 °C, after which a drop in the stress occurred accompanied by through-thickness cracking of the two outermost layers. After thermally cycling the samples, the stress in the topcoat was reduced to approximately 50 MPa, and there was no drop in stress upon cooling. This stress reduction was attributed to a crystallographic phase transformation of the topcoat and the accompanying change in thermal expansion coefficient. The addition of a doped aluminosilicate to the mullite layer did not lower the stress in the topcoat, but may offer increased durability due to an increased compressive stress.

In this work we report the synthesis and structural characterization of the elpasolite Cs2NaTbCl6, belonging to the space group Fm3m. The synthesis is by solid state reaction, in controlled atmosphere. By means of thermal analysis (DTA/TGA), the best crystallization temperatures were obtained: 772.2 °C for 2 hours. Structural studies are carried out by means of DRX-powder diffraction and application of the Rietveld profiles refinement method, for the 32 diffraction lines analyzed. The following crystallographic parameters are obtained: a0=10.7636 (Å), Z=4, M=660.44, V=1247.0 (Å)3, Dx=3.519, and Dexp=3.52±0.01.

A well-crystallized sample of powdered KCl has been distributed among several laboratories in order to test the reproducibility of the lattice parameter measurement on different X-ray powder diffraction instruments. The precision of the determined unit-cell dimension is in the 10−5 Å range, while the discrepancies among the results from different laboratories using the same numerical analysis are at least one order of magnitude higher. It is shown that if different numerical analyses, including full pattern refinement, are used, values differing in the third decimal digit are obtained for the same data set.

In this work we present results of X-ray diffraction using powder method, on natural alexandrite samples from Minas Gerais State (Brazil), as a function of a sequence of annealing. From these measurements we determine lattice parameters before (a=9.405 Å, b=5.471 Å, c=4.409 Å) and after annealing, and its structure is confirmed as orthorhombic. Measurements done after an annealing of 15 minutes at 700 °C and for 5 hours at 1000 °C indicate the migration of atoms present in the sample through different phases, which were also identified by Microprobe Analysis (WDS). However we have verified that such migration does not modify the structure. X-ray diffraction measurements have been carried out in conjunction with optical absorption in the UV–Vis as a function of annealing.

X-ray powder diffraction data are presented for nine new phases with the tetragonal tungsten bronze structure. By comparison with the structure of the M=Nb,RE=La analogue, these contain Ba in the large pentagonal sites with coordination number 15, a range of large rare-earth cations and Bi in the twelve coordinate sites, and the smaller cations, Ti and either Nb or Ta, in the octahedral framework sites. The a lattice parameter data of the tetragonal unit cell show an approximately linear variation with trivalent ion radius, apart from Dy, whose value appears to be anomalous; data for c show little variation with trivalent ion radius.

The Rietveld method based on X-ray diffraction (XRD) technology has been commonly applied for the quantitative analysis of crystalline minerals in organic-rich rocks. The presence of organic matter, however, has interference in varying degree to the quantitative result. In this work, the mixed samples of organic matter and crystalline minerals at given proportions were prepared to investigate the effect of organic matter on the Rietveld quantitative analysis of crystalline minerals in coal gangue. The relative standard deviation (RSD) and absolute error (AE) were used to evaluate the precision and accuracy of the quantitative result. The results showed that the presence of organic matter led to a reduction in the precision and accuracy. It was attributed in part to the presence of organic matter, which can produce a background noise in the XRD pattern, especially in the region of 5–30° (2θ). Further results showed that the interference in this region increased with the increase in the organic matter content. The RSD and AE were within the range of 10% and 2%, respectively, when the organic matter content is <30 wt%. Based on this, an approximate method for the Rietveld quantitative analysis of crystalline minerals in coal gangue was established.

The structure transitions and phase relationships of DyFe3−xAlx compounds have been investigated by X-ray powder diffraction. Our XRD results show that each of the compounds with x≤0.45 crystallizes in the rhombohedral PuNi3-type structure with space group R3¯m and Z=9; for the 0.8≤x<1.0 compounds, each has a hexagonal structure of the CeNi3 type with space group P63/mmc and Z=6; and each of the samples with 0.45<x<0.8 is a two-phase mixture of the PuNi3- and CeNi3-type structures. The calculated XRD intensities of the DyFe3−xAlx compounds with x=0.2, 0.33, 0.4, and 0.45 indicate that Dy occupies the 3a and 6c sites, Fe and Al distribute randomly on the 18h site, and the 3b and 6c sites are exclusively occupied by Fe, which agrees well with those of our experimental XRD patterns. The XRD intensities of the DyFe3−xAlx compounds with x=0.8 and 1.0 have also been calculated and found to agree with the experimental results with Dy on the 2c and 4f sites, Fe and Al at the 12k site, and Fe at the 2a, 2b, and 2d sites. In the two-phase region with x=0.45–0.8, the values of unit-cell parameters and phase compositions are linearly dependent on the value of x, indicating that the two phases are constituted by the same composition x with different stacking arrangements. This abnormal two-phase equilibrium is further confirmed by the structural analysis of the DyFe2.33Al0.67 (or x=0.67) sample. The samples with x=1.1 and 1.2 were also analyzed, and each found to be a mixture of more than two phases.

Algorithms are presented to correct intensities affected by divergence slit attenuation in the low 2θ region of Bragg–Brentano powder diffractometers with rectangular sample holders. The intensity loss below a limiting angle 2θ1 occurs when the X-ray beam cross section exceeds the sample surface at decreasing angles. For identification purposes, the observed intensities can be scaled up to values comparable with intensities unaffected by divergence slit effects.

A new single-phase copper chromate compound was successfully synthesized by a hydrothermal method and characterized by XRD, SEM, TGA, and XRF analysis. The experimental XRD pattern was analyzed by automatic indexing and the compound was found to be monoclinic with space group P21/a and unit-cell parameters of a=10.1829(11) Å, b=4.9516(6) Å, c=7.2899(7) Å, and β=103.64(1)°. The chemical formula of the copper chromate compound determined by XRF and TGA was determined to be (NH4)1.5Cu2Cr2O8(OH)1.5⋅H2O. XRD results also showed that the synthesized compound decomposed into CuCr2O4 and CuO after being calcined at 600 °C.

The reflection shift δ2Θ caused by a radial shift δr of the sample away from its tangential position at the focusing circle is examined for grazing incidence diffraction and grazing excidence diffraction. Experimental results for residual strain/stress evaluation on thin films using a Bragg–Brentano diffractometer with a grazing incidence equipment are presented. Grazing excidence diffraction is less sensitive to δr than grazing incidence diffraction.

Although forensic science is regarded with a certain amount of fascination and admiration by the general public, to the practising forensic scientist it is often associated with painstaking and frustrating examinations.

This is particularly so in the most traditional area of forensic science, namely that of contact evidence where the identification and comparison of minute samples may provide an important clue for the investigator and assist in the conviction or exoneration of an accused person.

Contact evidence may include hairs and other fibres, paint samples, glass fragments, stains, soils and other deposits. Modern instrumentation such as infra-red spectrophotometry, gas chromatography, atomic absorption spectroscopy and energy dispersive X-ray analysis now allows a relatively simple identification of the composition of these materials. However, these techniques are not necessarily directed towards the absolute determination of structure of materials and this is particularly so in the case of crystalline materials of forensic interest such as soil, mortar, brick dust and paint fillers. Although the techniques previously mentioned provide the basis of an elemental analysis this may not be of much assistance in a forensic approach where chemical structure is the basis of a scentific comparison.

Line profiles of a powder diffraction pattern and the aberrations which affect the centroid and the variances of the peaks have been analyzed using the visualization in scientific computing (ViSC) systems. The constrained optimization of those aberrations has been derived from the theory developed by Wilson (1963). It allows the determination of systematic instrumental effects and gives indication of other diffraction effects related to the samples. The CuKβ radiation was used to process the experimental data directly as it is comprised of only one single wavelength.