Synthesis and Characterization of Brannerite Compositions for MOX Residue Disposal

MRS Advances ◽  
2016 ◽  
Vol 2 (10) ◽  
pp. 557-562 ◽  
Author(s):  
D.J. Bailey ◽  
M.C. Stennett ◽  
N.C. Hyatt
Keyword(s):  
Powder Diffraction ◽  
Microstructural Analysis ◽  
Charge Compensation ◽  
Phase Assemblage ◽  
Secondary Phases ◽  
Host Matrix ◽  
Neutron Absorber ◽  
X Ray ◽  
Valence States ◽  
Trivalent Cations

ABSTRACTDue to their high actinide content MOX residues require immobilization within a robust host matrix. Although it is possible to immobilize actinides in vitreous wasteforms; ceramic phases, such as brannerite (UTi2O6), are attractive due to their high waste loading capacity and relative insolubility. Brannerites Gd0.1U0.9Ti2O6, Ce0.1U0.9Ti2O6and Gd0.1U0.81Ce0.09Ti2O6were prepared using an oxide route. Charge compensation of trivalent cations was expected to occur via the oxidation of U (IV) to higher valence states (U (V) or U (VI)). Gd was added to act as a neutron absorber in the final Pu bearing wasteform and Ce was used as a structural surrogate for Pu. X-ray absorption spectroscopy showed that Ce (IV) was reduced to Ce (III) in all cases. X-ray powder diffraction of synthesized specimens found that the final phase assemblage was strongly affected by processing atmosphere (air or argon). Prototypical brannerite was formed in all compositions, secondary phases observed were found to vary according to processing atmosphere and stoichiometry. Microstructural analysis (SEM) of the sintered samples confirmed the results of the X-ray powder diffraction.

scholarly journals Crystal structures and X-ray powder diffraction data for Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6 synthetic leucite analogues

2021 ◽  
pp. 1-9
Author(s):  
Anthony M. T. Bell ◽  
Alex H. Stone
Keyword(s):  
Alkali Metal ◽  
Powder Diffraction ◽  
Divalent Cation ◽  
Alkali Metal Cation ◽  
Trivalent Cation ◽  
Powder Diffraction Data ◽  
Rietveld Refinements ◽  
X Ray ◽  
Trivalent Cations ◽  
Silicate Framework

Leucites are tetrahedrally coordinated silicate framework structures with some of the silicon framework cations partially replaced by divalent or trivalent cations. These structures have general formulae A2BSi5O12 and ACSi2O6; where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation. In this paper, we report the Rietveld refinements of three more synthetic leucite analogues with stoichiometries of Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6. Cs2NiSi5O12 is Ia $\bar{3}$ d cubic and is isostructural with Cs2CuSi5O12. RbGaSi2O6 is I41/a tetragonal and is isostructural with KGaSi2O6. CsGaSi2O6 is $I\bar{4}3d$ cubic and is isostructural with RbBSi2O6.

The crystal chemistry and paragenesis of honessite and hydrohonessite: the sulphate analogues of reevesite

1981 ◽  
Vol 44 (335) ◽  
pp. 339-343 ◽  
Author(s):  
D. L. Bish ◽  
A. Livingstone
Keyword(s):  
Powder Diffraction ◽  
Molecular Geometry ◽  
Structural Formula ◽  
Basal Spacing ◽  
Nickel Sulphate ◽  
X Ray ◽  
Infra Red ◽  
Trivalent Cations ◽  
The Difference ◽  
Mixed Nature

AbstractHonessite and hydrohonessite from Unst, Shetland, and Linden, Wisconsin, are sulphate-containing members of the pyroaurite group and are analogous to reevesite. The structural formula can be written (Ni5.55Mg0.10Fe2.353+)(OH)16(SO4)1.18.xH2O for the Unst material, with sulphate groups replacing the interlayer carbonate groups in reevesite. Microprobe analyses of the Unst material show amounts of SO3 in excess of that required to balance all trivalent cations and this may be due to the presence of an amorphous nickel sulphate material. We find no evidence for the presence of trivalent nickel in honessite.The Unst material occurs in both 8.8 (honessite) and 11.1 Å (hydrohonessite) forms, depending on composition, humidity, and temperature, similar to carrboydite, motukoreaite, and SO4-exchanged takovite. The Wisconsin material occurs only with an 8.8 A basal spacing. The increase from the 7.7 Å basal spacing of reevesite is due to the difference in molecular geometry of carbonate and sulphate groups. The presence of the sulphate molecule is unambiguously shown by the infra-red spectra, and the observed bands are consistent with the sulphate groups lying in the interlayer with their trigonal axes parallel to c. The Unst material is found intimately mixed in variable proportions with reevesite, distributed in patches on chromite, and the mixed nature is revealed by X-ray powder diffraction, by variations in total SO3 content, and by the presence of absorptions due to both SO2-4 and CO2-3 in the infra-red spectra.

Powder diffraction study of LiCu2O2 crystals

2001 ◽  
Vol 16 (1) ◽  
pp. 30-36 ◽  
Author(s):  
W. Paszkowicz ◽  
M. Marczak ◽  
A. M. Vorotynov ◽  
K. A. Sablina ◽  
G. A. Petrakovskii
Keyword(s):  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Growth Conditions ◽  
Secondary Phases ◽  
Orthorhombic Space Group ◽  
Two Phase ◽  
Spontaneous Crystallization ◽  
Slow Increase ◽  
X Ray ◽  
Phase Compound

LiCu2O2 crystals grown by spontaneous crystallization from the fluxed melt were studied by powder X-ray diffraction. The phase analysis shows that the applied growth conditions are suitable for preparation of a single-phase compound. The as-grown crystals contain only traces of foreign phases (Li2CuO2, CuO, Cu2O) typical for preparation of the LiCu2O2 compound. Attempts to anneal or quench the as-grown crystals led to two-phase samples containing LiCu2O2 and LiCu3O3. X-ray powder diffraction pattern of a LiCu2O2 crystal is reported and compared with literature data. The crystal structure is orthorhombic, space group Pnma, in agreement with literature data. Lattice parameters of the studied sample are a=5.7286(2) Å, b=2.8588(1) Å, and c=12.4143(3) Å. Time evolution of a diffraction pattern illustrates a slow increase of the secondary-phases contribution assumed to be due to interaction of the powdered crystal with humid air. A brief summary of compounds known in the Li–Cu–O system is included

X-Ray Powder Diffraction Study of NBS Fly Ash Standard Reference Materials

1988 ◽  
Vol 3 (3) ◽  
pp. 156-161 ◽  
Author(s):  
Gregory J. McCarthy ◽  
Diane M. Johansen
Keyword(s):  
Fly Ash ◽  
Powder Diffraction ◽  
Reference Materials ◽  
Diffuse Scattering ◽  
Standard Reference Materials ◽  
Phase Assemblage ◽  
National Bureau ◽  
X Ray ◽  
Tricalcium Aluminate ◽  
Ferrite Spinel

AbstractThe fly ash Standard Reference Materials (SRMs) issued by the U.S. National Bureau of Standards have been studied by X-ray powder diffraction (XRD). Based on observations of large diffuse scattering maxima in their X-ray diffractograms, it was evident that all of the ashes had a high glass content. SRM 1633a and 2689, derived from the combustion of bituminous coal, contained different amounts of quartz, mullite, hematite and ferrite spinel (magnetite). SRM 2891, derived from subbituminous coal had quite a different chemical composition and a more complex crystalline phase assemblage, that included these four phases plus anhydrite, tricalcium aluminate, lime, periclase and minor phases. SRM 2690, also derived from subbituminous coal, had only quartz, mullite and ferrite spinel as detectable phases in its diffractogram. Analytical CaO is an important factor in determining the phase assemblage; SRM 2691 had 25.8 wt%, SRM-2690 had 8.0%, and the ash derived from bituminous coals had only 1.6-3.0%. The changing composition of the glass phases in the SRMs is detected in a shift in the position and shape of the diffuse scattering maximum in the diffractograms. Use of an internal intensity standard permitted quantitative comparisons of the relative amounts of crystalline phases among the four fly ash SRMs.

Effect of Solids Loadings, Sintering Temperatures and Sintering Periods on Microstructure of Hydroxyapatite

2017 ◽  
Vol 751 ◽  
pp. 629-635 ◽  
Author(s):  
Oratai Jongprateep ◽  
Chonthicha Nueangjumnong ◽  
Jednupong Palomas
Keyword(s):  
Microstructural Analysis ◽  
Calcium Nitrate ◽  
Primary Phase ◽  
Synthesis Process ◽  
Secondary Phases ◽  
X Ray Diffraction ◽  
Solution Combustion ◽  
X Ray ◽  
Orthopedic Applications ◽  
Combustion Technique

Attributed to its biocompatibility and osteoconductivity, hydroxyapatite (HAp, Ca10(PO4)6(OH)2) has been extensively utilized as a bioactive material. As the implant material, HAp is required to be fabricated into a porous form. The present study was therefore aimed at synthesizing HAp powder by solution combustion technique and at fabricating porous HAp specimens. Calcium nitrate and ammonium dihydrogenphosphate (NH4H2PO4), with Ca/P ratio equal to 2.3, were used as initial reagents in the HAp synthesis process. X-ray diffraction analysis confirmed that HAp was present as the primary phase, while minor secondary phases, Tri-calcium phosphaste (TCP) and CaO, were also observed. To prepare porous specimens, HAp slip with solids loadings ranging from 15 to 25 vol% was cast into acrylic molds and sintered. The sintering temperatures were 1350°C and 1450°C, and sintering periods ranged from 2 to 4 hours. Results from microstructural analysis revealed that high solids loadings, sintering temperatures and sintering periods resulted in decreasing of porosity. Porosity in the range between 30 and 90%, which was in an acceptable range for orthopedic applications, was observed.

Effect of Cr doping on the structure of (Pr0.55Ca0.45)(Mn1−yCry)O3: A Rietveld refinement study

2004 ◽  
Vol 19 (2) ◽  
pp. 137-140
Author(s):  
A. Martinelli ◽  
M. Ferretti ◽  
C. Castellano
Keyword(s):  
Powder Diffraction ◽  
Rietveld Method ◽  
Structural Data ◽  
Secondary Phases ◽  
X Ray ◽  
Binary Oxides ◽  
Orthorhombic Cell ◽  
Bond Valence Sum ◽  
Perovskite Type ◽  
Cr Doping

(Pr0.55Ca0.45)(Mn1−yCry)O3 (with y=0.00, 0.03, and 0.06) have been prepared by means of a solid state reaction from stoichiometric powder mixtures of binary oxides. X-ray powder diffraction analysis reveals the formation of the perovskite-type compound for the whole considered compositions; no evidence for secondary phases may be detected. The structural refinements have been carried out using X-ray powder diffraction data applying the Rietveld method; the lattice parameters of the orthorhombic cell faintly change with composition. On the contrary the tilting of the octahedra results are strongly dependent on the concentration of Cr in the 4b site. Bond valence sum method has been applied in order to evaluate the possible presence of lattice-induced strains and the amount of Mn4+. Structural data are also reported.

scholarly journals (Cu0.4Al0.3)TaSe2: PREPARATION AND CRYSTAL STRUCTURE ANALYSIS FROM X-RAY POWDER DIFFRACTION

2020 ◽  
Vol 28 (29) ◽  
pp. 01-06
Author(s):  
Pedro GRIMA-GALLARDO ◽  
Sonia DURÁN ◽  
Marcos MUÑOZ ◽  
Dibya P RAI ◽  
Gerzon E. DELGADO
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Alloy System ◽  
Crystal Structure Analysis ◽  
Partial Ordering ◽  
Secondary Phases ◽  
X Ray ◽  
Cell Parameters ◽  
New Phase

A new phase of the (CuAlSe2)1-x(TaSe)x alloy system was synthesized by the melt and annealing technique and studied by SEM, DTA, and XRPD techniques. Its structure has been refined by the Rietveld method using X-ray powder diffraction data. The new alloy corresponds with the stoichiometry Cu0.4Al0.3TaSe2. This compound crystallizes in the hexagonal space group 𝑃6ത𝑚2 (Nº 187) with a MoS2-type structure, and unit cell parameters a = 3.455(2) Å, c = 13.423(4) Å, V = 138.7(1) Å3, Z =2. The crystal structure is based on the MoS2- type of stacking of TaSe2 layers with a partial ordering of Cu and Al cations over the tetrahedral sites. The powder pattern was composed of 63.1% of the principal phase Cu0.4Al0.3TaSe2 and 29.9% of CuAlSe2, 7.0% of TaSe3, as the secondary phases.

New horizons for the structural characterization of stainless steel slags by X-ray powder diffraction

2007 ◽  
Vol 2007 (suppl_26) ◽  
pp. 61-66 ◽  
Author(s):  
B. Peplinski ◽  
B. Adamczyk ◽  
G. Kley ◽  
K. Adam ◽  
F. Emmerling ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Powder Diffraction ◽  
Structural Characterization ◽  
X Ray ◽  
New Horizons
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