Rietveld Analysis of Ceramic Nuclear Waste Forms

1993 ◽  
Vol 333 ◽  
Author(s):  
T.J. White ◽  
H. Mitamura
Keyword(s):  
Rietveld Method ◽  
Amorphous Material ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Waste Forms ◽  
Simulated Waste ◽  
Diffraction Patterns ◽  
Nuclear Waste Forms ◽  
Selection Of

ABSTRACTPowder X-ray diffraction patterns were collected from three titanate waste forms - a calcine powder, a prototype ceramic without waste, and a ceramic containing 10 wt% JW-A simulated waste - and interpreted quantitatively using the Rietveld method. The calcine consisted of fluorite, pyrochlore, rutile, and amorphous material. The prototype waste form contained rutile, hollandite, zirconolite and perovskite. The phase constitution of the JW-A ceramic was freudenbergite, loveringite, hollandite, zirconolite, perovskite and baddeleyite. Procedures for the collection of X-ray data are described, as are assumptions inherent in the Rietveld approach. A selection of refined crystal data are presented.

scholarly journals Solidified Fillings of Nanopores

2005 ◽  
Vol 876 ◽  
Author(s):  
Patrick Huber ◽  
Klaus Knorr
Keyword(s):  
Pore Diameter ◽  
Stacking Faults ◽  
Pore Geometry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Medium Length ◽  
Close Packed Structure ◽  
Packed Structure ◽  
Diffraction Patterns ◽  
Selection Of

AbstractWe present a selection of x-ray diffraction patterns of spherical (He, Ar), dumbbell- (N2, CO), and chain-like molecules (n-C9H20, n-C19H40) solidified in nanopores of silica glass (mean pore diameter 7nm). These patterns allow us to demonstrate how key principles governing crystallization have to be adapted in order to accomplish solidification in restricted geometries. 4He, Ar, and the spherical close packed phases of CO and N2 adjust to the pore geometry by introducing a sizeable amount of stacking faults. For the pore solidified, medium-length chainlike n-C19H40 we observe a close packed structure without lamellar ordering, whereas for the short-chain C9H20 the layering principle survives, albeit in a modified fashion compared to the bulk phase.

Structure of Carbonated Hydroxyapatite Based on Rietveld Method

2008 ◽  
Vol 368-372 ◽  
pp. 1187-1189
Author(s):  
Xu Ran ◽  
Jun Guo Ran ◽  
Li Gou ◽  
Ji Yong Chen ◽  
Jiao Min Luo
Keyword(s):  
Crystal Structure ◽  
Sintering Temperature ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Structure Parameters ◽  
X Ray Diffraction ◽  
Carbonated Hydroxyapatite ◽  
X Ray ◽  
Quantitative Results ◽  
Distortion Index

The crystalline structures of B-type carbonated hydroxyapatite (CHA) powders sintered at 700, 900 and 1100°C, respectively, were studied by Rietveld analysis of powder X-ray diffraction (XRD) data. A series of structure parameters, including lattice parameters (a and c), bond length and the distortion index of PO4 tetrahedron (Dind) were calculated by Rietveld method to characterize the fine structure of CHA. The broadening effect of XRD reflections was separated to calculate the micro-strain and crystalline size. The results showed that CHA become more stable with the increase of sintering temperature, but the CO3 2- is almost lost at temperature of 1100°C. The quantitative results about crystal structure of CHA based on crystalline structure simulated by Rietveld method are obtained.

scholarly journals Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

Cerâmica ◽  
2016 ◽  
Vol 62 (361) ◽  
pp. 1-8 ◽  
Author(s):  
J. L. Alves ◽  
A. E. Zanini ◽  
M. E. de Souza ◽  
M. L. F. Nascimento
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Rietveld Method ◽  
Bentonite Clay ◽  
Rietveld Analysis ◽  
Industrial Applications ◽  
X Ray Diffraction ◽  
X Ray ◽  
Almost All ◽  
Scanning Electron

Abstract Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitória da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8) μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale.

A semi-empirical asymmetry function for X-ray diffraction peak profiles

1995 ◽  
Vol 10 (3) ◽  
pp. 204-206 ◽  
Author(s):  
P. Riello ◽  
P. Canton ◽  
G. Fagherazzi
Keyword(s):  
Goodness Of Fit ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Opening Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Asymmetry Function ◽  
The Asymmetry ◽  
Fit Index ◽  
Semi Empirical

A new semi-empirical approximation for the asymmetry function to be used in the X-ray Rietveld analysis has resulted in lower values of the so-called goodness-of-fit index, defined as S = Rwp/Rexp, where Rwp is the R-weighted pattern and Rexp is the R-expected [R. A. Young, The Rietveld Method (Oxford U.P., Oxford, 1993)], with respect to the corresponding values obtained with the classical approximation used by Rietveld in his fundamental paper. A comparing test of the two asymmetry functions was carried out for the cubic Y2O3 and for αAl2O3 using either pseudo-Voigt or Pearson VII symmetrical functions and two diffractometers. As in the case of the Rietveld approximation, the present one, which employs an exponential function, is optimized using only one fitting parameter. Experimentally, the asymmetry can be considerably diminished by using Soller slits with a small opening angle (≤2°).

X-ray powder diffraction analysis of the heteropoly-molybdate (MoO2)0.5PMo14O42

2003 ◽  
Vol 18 (3) ◽  
pp. 236-239 ◽  
Author(s):  
L. Marosi ◽  
J. Cifré ◽  
C. Otero Areán
Keyword(s):  
Catalytic Activity ◽  
Diffraction Analysis ◽  
Computer Modeling ◽  
Powder Diffraction ◽  
Rietveld Analysis ◽  
Nitrogen Atmosphere ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Patterns

The new heteropoly blue compound (MoO2)0.5PMo14O42, which is relevant in the context of catalytic activity of heteropoly-molybdates, was prepared by controlled thermolysis of (NH4)3PMo12O40 at 730 K in a nitrogen atmosphere. Powder X-ray diffraction analysis showed that this compound has a cubic unit cell, space group Pn3m (No. 224), with ao=11.795(2) Å, Z=2 and DXR=4.2466 g cm−3. Computer modeling and Rietveld analysis of powder diffraction patterns led to a proposed structure of the corresponding Keggin-cage unit PMo14O42.

A Rietveld-analysis program for X-ray powder spectro-diffractometry

1999 ◽  
Vol 14 (2) ◽  
pp. 106-110 ◽  
Author(s):  
Yanan Xiao ◽  
Shinjiro Hayakawa ◽  
Yohichi Gohshi ◽  
Masaharu Oshima ◽  
Fujio Izumi ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Absorption Edge ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Anomalous Scattering ◽  
Analysis Program ◽  
X Ray ◽  
Diffraction Patterns ◽  
X Ray Absorption

In order to exploit X-ray powder spectro-diffractometry, the program RIETAN-97ß for refining crystal structure and lattice parameters by the Rietveld method was modified extensively. The resulting software can be used to refine anomalous scattering factors, fr and fi, for specified crystallographic sites near the X-ray absorption edge of a particular element. The effectiveness of the modified software was tested by using powder diffraction patterns simulated by the original RIETAN-97ß software and a series of measured powder diffraction patterns of Fe3O4 with incident X-ray energies near the absorption edge of iron.

scholarly journals Bitumen Coating as a Tool for Improving the Porosity and Chemical Stability of Simulated Cement-Waste Forms

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
H. M. Saleh
Keyword(s):  
Experimental Tests ◽  
Waste Form ◽  
X Ray Diffraction ◽  
Microscope Examination ◽  
X Ray ◽  
Bitumen Emulsion ◽  
Waste Forms ◽  
Surrounding Environment ◽  
Simulated Waste ◽  
Physical And Chemical

Coating of simulated cement-based waste form was investigated by performing physical and chemical experimental tests. Moreover, X-ray diffraction, Fourier transform infrared spectroscopy, and electron microscope examination were applied on coated and noncoated simulated waste forms. Experimental results indicated that coating process improved the characterizations of cement-based waste form such as porosity and leachability. Diffusion coefficients and leach indecies of coated specimens were calculated and showed acceptable values. It could be stated that by coating cemented-waste form by bitumen emulsion, the radioactive contaminants were isolated, thus reducing the back release to surrounding environment during flooding by groundwater and consequently, saving the environment.

Comparative Crystallinity and Morphology of Enamel, Dentine, Bone and Amorphous Concretions

1970 ◽  
Vol 28 ◽  
pp. 152-153
Author(s):  
Racquel Z. LeGeros ◽  
John P. LeGeros ◽  
Otto R. Trautz ◽  
W. Paul Shirra
Keyword(s):  
Calcium Carbonate ◽  
Amorphous Material ◽  
Apatite Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Human Enamel ◽  
Diffraction Patterns ◽  
Calcified Tissues ◽  
Human Ear

The inorganic phase of calcified tissues of vertebrates he an apatite structure [Ca10(PO4)6(OH)2] while the inorganic phase of the invertebrates such as crustaceans is well crystallized calcium carbonate [CaCO3] in the form of either calcite, aragonite, and sometimes, vaterite. In rare cases, “amorphous” deposits are found such as in the concretions of tapeworm (Saginata Marginata), in the tendon of lobster claw, and in the statoconia of the human ear.Considerable differences in the “crystallinity” of human enamel, bone or dentine, and tapeworm concretions are demonstrated in the size and/or strain broadening of their x-ray diffraction patterns (Fig.1). The pattern of human enamel (1A) demonstrates that it is very well crystallized apatite; whereas the pattern of bone or dentine suggest that it is poorly crystallized (1B); and the pattern of tapeworm concretions (no discernible peaks) indicate an amorphous material (1C).

CRAFS: a model to analyze two-dimensional X-ray diffraction patterns of plant cellulose

2013 ◽  
Vol 46 (4) ◽  
pp. 1196-1210 ◽  
Author(s):  
Rafael P. Oliveira ◽  
Carlos Driemeier
Keyword(s):  
Fine Structure ◽  
Higher Plants ◽  
Rietveld Method ◽  
Renewable Resource ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Peak Broadening ◽  
Cellulose Iβ ◽  
Diffraction Patterns

Cellulose from higher plants is a vast renewable resource organized as crystals. Analysis of these crystals by X-ray diffraction poses very specific challenges, including ubiquitous crystallite texture and substantial overlapping of diffraction peaks. In this article, a tailor-made model named Cellulose Rietveld Analysis for Fine Structure (CRAFS) is developed to analyze two-dimensional X-ray diffraction patterns from raw and processed plant cellulose. One-dimensional powder diffractograms are analyzable as a particular case. The CRAFS model considers cellulose Iβ crystal structure, fibrillar crystal shape, paracrystalline peak broadening, pseudo-Voigt peak profiles, harmonic crystallite orientation distribution function and diffraction in fiber geometry. Formulated on the basis of the Rietveld method, CRAFS is presently written in the MATLAB computing language. A set of meaningful coefficients are output from each analyzed pattern. To exemplify model applicability, representative samples are analyzed, bringing some general insights and evidencing the model's potential for systematic parameterization of the fine structure of raw and processed plant celluloses.

Relationship of quantitative X-ray diffraction measurements of geologic materials to cesium sorption

2002 ◽  
Vol 90 (9-11) ◽  
Author(s):  
Timothy E. Payne ◽  
W. K. Bertram ◽  
T. Itakura ◽  
M. D. Raven
Keyword(s):  
Arid Zone ◽  
Rietveld Method ◽  
Distribution Coefficients ◽  
X Ray Diffraction ◽  
X Ray ◽  
Geologic Materials ◽  
Geologic Samples ◽  
Diffraction Patterns ◽  
Statistical Relationships ◽  
Relationship Of

SummaryThe amounts of clay minerals in geologic samples from the Australian arid zone were measured using the SIROQUANT program, which quantifies mineral abundances from X-ray diffraction patterns using the Rietveld method. The sorption of trace cesium on the same samples was investigated in batch experiments. The statistical relationships between the Cs distribution coefficients (K

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