Rietveld-based quantitative X-ray diffraction (QXRD) has been extensively used for mineralogical characterization in order to understand the reaction chemistry, and kinetics of minerals leaching and formation. This work presents examples where QXRD has been applied to understanding fundamental aspects of these two processes. Firstly, the co-processing of nickel laterites and sulphidic materials has the potential to offer several advantages that include the use of lower grade (including non-smeltable) concentrates, improvement in the rheological behaviour of the blends, and reduction in the use of sulphuric acid. The leaching kinetics and chemistry of mixed nickel laterite ore and sulphide concentrate were explored by the QXRD analysis of feed materials and, intermediates and final leach residues produced using controlled oxidation rates. Under high temperature (250 °C) and pressure oxidation (~40 to 45 atm.) conditions, sulphide minerals in the nickel concentrate underwent several oxidative hydrothermal transformations, and ferrous iron was oxidized and precipitated primarily as hematite. High recovery of nickel can be achieved with low acid consumption under these conditions. Secondly, iron precipitation/removal is an important down-stream process in hydrometallurgy. Moderate concentrations of ferrous iron can be oxidized using micro-organisms with oxidation rates several orders of magnitude faster compared with abiotic oxidation at ambient temperature and pressure. QXRD and chemical analysis have indicated that after oxidation, iron at pH ~2 mostly precipitates as jarosite with various amounts of K+, Na+, NH4+, and H3O+ incorporated into the structure. Bio-catalysed iron removal can be achieved with minimum copper and nickel losses at relatively low pH conditions.

The crystal structure of Na(NH4)Mo3O10·H2O has been solved by parallel tempering using the FOX software package with synchrotron powder diffraction data obtained from beamline 08B1-1 at the Canadian Light Source. Rietveld refinement, performed with the software package GSAS, yielded orthorhombic lattice parameters of a = 13.549 82(10), b = 7.618 50(6), and c = 9.302 74(7) Å (Z = 4, space group Pnma). The structure is composed of molybdate chains running parallel to the b-axis. The Rietveld refinement results were compared with density functional theory calculations performed with CRYSTAL14, and show excellent agreement with the calculated structure.

Experimental X-ray powder diffraction data, unit-cell parameters, and space group for levetiracetam, C8H14N2O2, are reported [a = 9.197(5) Å, b = 8.006(0) Å, c = 6.289(3) Å, β = 108.457(3)°, unit-cell volume V = 439.261 Å3, Z = 2, and space group P21]. All measured lines were indexed and are consistent with the P21 space group. No detectable impurity was observed.

A method has been derived and is currently being used to plot normalized pole figures by computer techniques. As the pole distribution traces, i.e., intensity of the diffracted X-ray beam, versus angular position of the specimen are not an acceptable input for the computer, the data required from such traces are entered onto IBM punch cards. Corrections for defocusing effects may be readily made as the data are transferred from the Brown recorder traces to IBM punch cards. It is possible to program other correction factors into the computer operations providing that these correction factors or curves can be established accurately. The computer translates angular position of the specimen into reactiiinear coordinates which are an identical representation of stereographic coordinates. This computer method has been used in conjunction with the Schulz reflection technique, but modification of the computer program permits its use with other quantitative X-ray techniques for determining preferred orientation.

The feasibility of using computer techniques to plot inverse pole figures has been considered.

The development of deformation textures of both initially disordered and ordered Cu3Au has been studied and discussed in terms of the stacking fault energies and twinning probabilities. No differences in the deforir.ation textures of the ordered and disordered materials were detected at deformations up to 40% reduction. However, at reductions of approximately 42% a marked difference was observed. This difference is attributed both to the degree of order and to the stacking fault energy of the ordered sample being conducive to deformation twinning at this stage of the rolling schedule. For samples which were reordered below the racrystallization temperature at intermediate stages of deformation (every 10% in total reduction) no differences between the ordered and initially disordered samples were observed up to 90% total reduction in thickness.

Six computer synthesized data sets, each representing a mixture, and one physical mixture were prepared and widely distributed in order to study the various search/match methods and factors which affect their success. A total of 67 returns were received representing eight countries and three search methods. The participants were primarily from industrial laboratories. The average score exceeded 90%. The Hanawalt search method yielded the best overall score. Use of the Frequently Encountered Phases subfile decreased the search time by about 40% and marginally increased the success rate. For the physical mixture the Δd/d and ΔI/I values were measured to about 2/1000 and 40% respectively. Use of an internal standard improved the d-values by a factor of 2 and resulted in better search/match performance.

The reduction of the background in x-ray fluorescent spectra is achieved by total reflection of the primary x-rays at a plane, smooth surface of a suitable reflector material. This effect essentially reduces the background caused by scattering of the primary photons from the substrate, thus improving the lower limits of detection in x-ray fluorescence analysis (XRF). Introducing additional to the reflector-substrate another reflector in the primary beam, this affects the spectral distribution of the exciting radiation (“high energy cutoff”). The result is an improved background, where detection limits of picogram amounts or concentrations in the ppb range are attainable for medium Z elements with energy dispersive detectors.

The purpose of this investigation was to develop a rapid, accurate method of analysis for small amounts of calcium in wolframite concentrates. This analysis is necessary to determine if wolframite concentrates meet the U. S. National Stockpile Specification P-57R2, which limits the calcium content to 0.2 per cent.

Because of the small depth of sample analyzed in fluorescent x-ray spectrography the calcium Kα line intensity was found to be a function of the chemical composition of the calcium-bearing particle as well as the matrix composition. This particle-conn position effect was particularly important in this analysis because the calcium may be present as a carbonate, tungstate, phosphate, etc. Three methods of sample preparation were found to eliminate the variation of calcium Kα intensity with mineralogical occurrences: (1) Reduction in particle size by extensive grinding, (2) chemical fusion wtli sodium carbonate, and (3) solution of the calcium by an add.

Determinations by all three procedures are believed to be accurate to within ± 5 per cent for more than 0.30 per cent calcium and ± 10 per cent at the 0.1-per cent level. The lower limit of detectability is in the order of 0.005-0.01 per cent.

The operating characteristics of a gas-flow proportional counter used in conjunction with a pulse-height analyzer were studied in detail. This detector was found to have a high counting efficiency for calcium Ka radiation, to have a low counting efficiency for overlapping higher order radiation and to have counting stability equivalent to Geiger tubes.

The automation of analytical equipment is proceeding at a rapid pace, particularly since the introduction of inexpensive microcomputer systems. Most of this equipment has one characteristic in common, that is, they produce digital spectral data. The usual method of recording spectral data has been the strip chart recorder. Strip charts require the hand encoding of position and intensities of the spectral lines. This requires that all of the lines be on scale or that the sample be run several times in order to amplify weaker lines. This problem is eliminated by recording the data digitally. Digital data can then be rapidly plotted on a cathode ray terminal to any desired scale. The user of digital data has access to a great variety of automatic data reduction programs.

In the conventional pole figure, an accurate representation can be attained by correcting the observed X-ray diffraction intensity for any change in diffraction geometry and by comparing this with the correctly established standard intensity. For the intensity corrections, ASTM has prescribed the method of Decker et al. In practice, however, the validity of the correction formula is uncertain, since the prerequisite is difficult to attain for parallelism of an incident beam of sufficient intensity. For the standard intensity, it is desirable to take the intensity obtained with the randomly oriented material of the same composition. However, in most cases an arbitrary unit has been taken because of the difficulty in getting a truly random and uniform sample. Under these circumstances, it is first necessary for an accurate representation of pole figures to make a random sample of uniform thickness for the standard. The authors have obtained satisfactory standard samples by sintering the randomly oriented iron powder made from iron chloride and made use of them to check the method of intensity correction. Satisfactory results are obtained in the randomness tests, such as the comparison of the relative intensity diffracted from the crystal planes parallel to the sample surface and the fluctuation of diffraction intensity during α rotation.

In the reflection case by the Schulz method, the (110) reflection intensity of a random sample, by Co Kα radiation, is independent of the tilting angle up to 50°. The other reflections do not give a constant intensity for the wide range of the tilting angles because of dispersion of the diffracted beam due to the wider separation of Kα doublet in the higher reflection angle and the wider irradiated area at the lower angles. In the transmission case Schulz's correction formula is in good agreement with the observed values for the various diffraction lines and the samples of various µt, while the Decker-Harker formula does not give the absorption change with α-rotation even by an incident beam of ⅙° divergence. In both cases, an accurate determination of pole densities is made by comparing the diffraction intensity of the standard sample substituted in place of the test specimen and by correcting the absorption change due to the difference of µt between the standard and test sample, which affords good coincidence in the overlapped region. The pole figure obtained by the above method furnishes an accurate prediction of plastic and elastic anisotropy in sheet metals.

This paper examines the relationship between the lattice defects and crystallization process of synthetic diamonds. Diamonds synthesized by high pressure, high temperature methods as well as diamonds vapor deposited under metastable conditions are considered. High pressure crystals precipitated from Ni or Co solutions contain inclusions of metastable carbides and metal atoms distributed throughout a small fraction of the octahedral holes in the diamond lattice.

Diamonds are grown metastabily by a chemical vapor deposition process in which CH4 and H2 are excited by a microwave plasma. Such diamonds are deposited as individual micro-monocrystals or as solid poly crystalline films. The defects in such crystals are related to impurities such as Si and H which produce point defects and tend to nucleate graphite, which can generate planar defects. Nucleation of a diamond phase on β-SiC is also considered, because of the lattice matching between them.

Diamond structure is a prototype of a family of related phases such as cubic BN (sphalerite structure) and solid solutions of diamond and cubic BN, Cubic BN-diamond solid solutions (BN)x(C2)1-x,0<x<l are, in turn, a prototype of AIIIBV-CIV phases, of which (GaP)x(Si2)1-x,0<x<l is an example. Substitution of B-N (or Ga-P) by C-C (or Si-Si) atom pairs at lattice sites is characteristic of these solid solutions.

The quality and interpretation of diffraction topographic images are strongly dependent on. the detailed laboratory techniques that are used in making them. In this paper practical instructions are given for the preparation of Berg-Barrett and Lang topographs. It is hoped that these suggestions will enable the novice in the field of X-ray topography to produce high quality images and to interpret them with a minimum of learning time. The topics treated include adjustment of the critical conditions for attaining highest resolution, choice of radiation and the specific hkl planes to be used, conditions limiting the size of the image, cause and avoidance of image distortion, choice of photographic emulsions, plate processing for best contrast and resolution, photomicrographs of the original image, and plate preservation.

Accurate measurement of the lattice misfit between the γ and γ phases in Ni-base single crystal superalloys at high temperatures has successfully been achieved using a parallel beam mode X-ray diffractometer with a high temperature specimen stage. The superalloys have γ' precipitates, an ordered FCC structure based on Ni3Al, in a γ-matrix having a disordered FCC structure (LI2). The parallel beam mode, the optics of which is made from a Ge (111) channel cut crystal, generates a superior monochromatic and parallel CuKα1 beam, which makes it possible to resolve a cluster peak in Ni-base superalloys into individual γ and γ ‘ peaks. This peak separation was almost impossible using the CuKα1+2 doublet beam from the standard type para-focusing mode, due to the very small difference in lattice parameters between the two phases.

Double crystal diffractometer measurements on silicon bombarded to a fluence >1016 ions/cm2 with 1 MeV deuterium and 2 MeV nitrogen are reported. Such measurements provide insight into radiation damage in silicon through the observation of Bragg case pendelloesung fringes and double peak rocking curves. Bragg case pendelloesung fringes are used to determine nondestructively the projected range of ions in silicon. Double peak rocking curves are used to measure changes in lattice parameter with the ion dose. Finally, a model of radiation damage in silicon is presented.

The temperature dependence of the cell parameters is given for Bi2Mo3O12, Bi2Mo2O9, γ-Bi2MoO6 and γ'-Bi2MoO6, and the volume expansion coefficient is derived. A description is given of a high-temperature diffractometer (HTD) for temperatures up to about 1600°C in controlled atmospheres.

A polycrystalline sample of YbCoO3 was prepared using a water-soluble complex method at relatively low temperatures. Common chelating ligands such as citric acid were employed for the synthesis of complex-based precursors, followed by thermal decomposition of the precursors at high temperatures. X-ray diffraction data were collected and the crystal structure was refined by the Rietveld method. The structure of YbCoO3 can be described as a sesquioxide C-M2O3-like structure with space group Ia-3 and unit-cell parameter a=10.4470 (2). The Yb3+ and the Co3+ cations are found to preferentially occupy the two nonequivalent 8d and 24d sites, respectively. The two independent atoms Yb/Co have octahedral coordination; however, the degrees of distortion of their coordination polyhedron are different. The relationship between the title compound and the orthorhombic Perovskite structure of YbCoO3 reported in the literature is established.

The structure of Ba7Cl2F12 has been determined ab initio from conventional X-ray powder diffraction data by the “heavy atom” method. The cell is hexagonal (space group P6¯, Z=1), with a=10.6373(2) Å and c=4.1724(2) Å. Refinement of 38 parameters by the Rietveld method, using 278 reflections, leads to cRwp=0.173, cRp=0.135, and RB=0.054. The structure has common characteristics with that of the other BaF2-rich fluorochloride, Ba12Cl5F19. In both phases Ba2+ ions lie in tricapped trigonal prisms formed by nine halide ions, and Cl− ions occupy the center of trigonal prisms of Ba2+ ions. F− ions are located in cationic tetrahedra or square pyramids.

DISVAR93 is a collection of programs devised to process XRPD patterns with the aim of determining the parameters of systematic instrumentation and sample effects. These effects have an influence on data uncertainty and also accuracy of the adopted models describing diffraction phenomena. Such modeling is carried out through the mathematical X-ray powder-diffraction theory, while parameter optimization is achieved by using the additive property of X2 and constraining the models to converge simultaneously to the same minimum in a restrained Hilbert's space. The package has been designed to allow both user interaction as well as automatic linking of programs managed by one main menu and offer several options to satisfy individual user requirements.