XAFS of Pu and Hf LIII Edge in Lanthanide-Borosilicate Glass

2009 ◽  
Vol 1193 ◽  
Author(s):  
A.A. Shiryaev ◽  
Ya.V. Zubabichus ◽  
S.V. Stefanovsky ◽  
A.G. Ptashkin ◽  
J.C. Marra
Keyword(s):  
Solid Solution ◽  
Chemical Composition ◽  
Borosilicate Glass ◽  
Fluorite Structure ◽  
Exafs Spectrum ◽  
Vitreous Phase ◽  
Tetragonal Pyramid ◽  
R Factor ◽  
Prepared Glass ◽  
Exafs Spectra

AbstractLanthanide-Borosilicate (LaBS) glass capable to dissolve up to ∼10 wt.% PuO2 is designed for immobilization of plutonium-bearing wastes. The sample of LaBS glass with a target chemical composition (wt %): 9.0 Al2O3, 11.8 B2O3, 12.2 Gd2O3, 6.3 HfO2, 17.2 La2O3, 13.6 Nd2O3, 9.5 PuO2, 18.1 SiO2, 2.3 SrO was prepared from PuO2 powder and mechanically activated mixture of chemicals at 1500 °C. The obtained product was visually homogeneous. Xraydiffraction of the as-prepared glass showed that it mostly consists of a vitreous phase withsmall amounts of crystalline PuO2 (or PuO2-HfO2 solid solution with minor HfO2), britholite andan oxide with a fluorite structure and a composition close to GdHfO1.75. The crystalline fractionincreased after storage for ∼1 year. Magnitude of the FT of EXAFS spectrum at Pu LIII edgeshows that the peak due to first coordination sphere is much more intense than that of the secondshell. This indicates that though some Pu entered crystalline phases (mainly distorted PuO2), itsmajor fraction remained in the vitreous phase. Fit of the spectrum (R-factor = 0.02) gives thefollowing distances: R (Pu-O1)1 = 1.98 (σ = 0.04), R (Pu-O1)2 = 2.18 (σ = 0.04), R (Pu-O1)3= 2.35, R (Pu-Pu) = 3.72 (σ = 0.04), R (Pu-O2) = 4.4 (σ = 0.06). Oxygen environment ofthe Pu4+ ions in the vitreous phase resembles axially squeezed tetragonal pyramid with acoordination number ∼5. The distances ∼2.35 and ∼4.4 correspond to the pairs Pu-O in thefirst and the second shells in the crystalline PuO2. The distance ∼3.72 corresponds to the Pu-Pu and/or Pu-M (M = Ln, Hf) distances. EXAFS spectra of Hf show that Hf is present mostly in thevitreous phase with major neighbors at 2.17 and ∼3.2 A.

Plutonium Environment in Lanthanide Borosilicate Glass

2010 ◽  
Vol 1264 ◽  
Author(s):  
Sergey Stefanovsky ◽  
Andrey Shyriaev ◽  
Yan V. Zubavichus ◽  
James C. Marra
Keyword(s):  
Solid Solution ◽  
Absorption Spectra ◽  
Partial Oxidation ◽  
Borosilicate Glass ◽  
Vitreous Phase ◽  
X Ray ◽  
Oxygen Ions ◽  
Prepared Glass ◽  
Peak Energy ◽  
X Ray Absorption

AbstractTwo lanthanide borosilicate (LaBS) glasses containing 9.5 and 5.0 wt.% PuO2 prepared at 1500 °C consisted of a vitreous phase and minor crystalline PuO2 (or PuO2-HfO2 solid solution with minor HfO2) and britholite-type phases. X-ray absorption spectra of Pu LIII edge in the as-prepared and stored for various periods LaBS glasses were recorded, analyzed and compared with the spectra of crystalline PuO2. Pu in the as-prepared glass existed in predominantly tetravalent form (Pu4+ ions) but its storage in air results in partial oxidation as was seen from shift of peak energy values. In the structure of the as-prepared glass, Pu4+ ions had a co-ordination number (CN) close to 6 (˜6.3) and were located within the axially squeezed octahedra with five equidistant oxygen ions at a distance of 2.265±0.015 Å and one – at shorter distance (2.130±0.010 Å) from the Pu4+ ion. The Pu—Pu(M) distance (second co-ordination shell) was 3.675±0.015 Å. “Aging” of the LaBS glass with transformation of some fraction of Pu into penta- or/and hexavalent form was accompanied by a structural transformation.

scholarly journals Formation of Intermediate Phases and Supersaturated Solid Solution in Al-Cu System during Diffusion

2018 ◽  
Vol 383 ◽  
pp. 31-35 ◽  
Author(s):  
Alexey Rodin ◽  
Nataliya Goreslavets
Keyword(s):  
Phase Diagram ◽  
Solid Solution ◽  
High Temperature ◽  
Chemical Composition ◽  
Low Temperature ◽  
Supersaturated Solid Solution ◽  
Diffusion Processes ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Intermediate Phases

The study of diffusion processes in the aluminum - copper system was carried out at the temperature 350 and 520 °C. Special attention was paid on the chemical composition of the system near Al/Cu interface. It was determined that the intermediate phases in the system, corresponding to the equilibrium phase diagram, were not formed at low temperature. At high temperature the intermediate phases forms starting with Cu - rich phases. In both cases supersaturated solid solution of copper in aluminum could be observed near the interface.

scholarly journals On solid solution in minerals; II, The chemical composition of analcite

1912 ◽  
Vol s4-33 (197) ◽  
pp. 433-439
Author(s):  
H. W. Foote ◽  
W. M. Bradley
Keyword(s):  
Solid Solution ◽  
Chemical Composition

Effect of Synthesis Conditions and Actinide Contents on Phase Composition of Actinide Bearing Ceramics

2003 ◽  
Vol 807 ◽  
Author(s):  
A. G. Ptashkin ◽  
S. V. Stefanovsky ◽  
S. V. Yudintsev ◽  
S. A. Perevalov
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
Phase Composition ◽  
Fluorite Structure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Synthesis Conditions ◽  
Reducing Conditions ◽  
Dispersive System ◽  
Scanning Electron

ABSTRACTPu-bearing zirconolite and pyrochlore based ceramics were prepared by melting under oxidizing and reducing conditions at 1550 °C. 239Pu content in the samples ranged between ∼10 and ∼50 wt.%. Phase composition of the ceramics and Pu partitioning were studied using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive system (SEM/EDS). Major phases in the samples were found to be the target zirconolite and pyrochlore as well as a cubic fluorite structure oxide. Normally the Pu content in the Pu host phases was 10–12 wt.%. This corresponds to the Pu content recommended for matrices for immobilization of excess weapons plutonium. At higher Pu content (up to 50 wt.%) additional phases, such as a PuO2-based cubic fluorite-structured solid solution, perovskite, and rutile were found.

scholarly journals Epitaxy of (GaN)1−x(ZnO)x Solid-Solution Thin Films with Widely Tunable Chemical Composition and Strong Visible Absorption

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Chang Yang ◽  
Yasushi Hirose ◽  
Takuto Wakasugi ◽  
Naoki Kashiwa ◽  
Hiroki Kawai ◽  
...  
Keyword(s):  
Thin Films ◽  
Solid Solution ◽  
Chemical Composition ◽  
Visible Absorption

scholarly journals Elasticity of Phases in Fe-Al-Ti Superalloys: Impact of Atomic Order and Anti-Phase Boundaries

Crystals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 299 ◽  
Author(s):  
Martin Friák ◽  
Vilma Buršíková ◽  
Naděžda Pizúrová ◽  
Jana Pavlů ◽  
Yvonna Jirásková ◽  
...  
Keyword(s):  
Solid Solution ◽  
Chemical Composition ◽  
Elastic Properties ◽  
Formation Energy ◽  
Chemical Species ◽  
Two Phase ◽  
Nano Structure ◽  
The Matrix ◽  
Free Material ◽  
Excess Fe

We combine theoretical and experimental tools to study elastic properties of Fe-Al-Ti superalloys. Focusing on samples with chemical composition Fe71Al22Ti7, we use transmission electron microscopy (TEM) to detect their two-phase superalloy nano-structure (consisting of cuboids embedded into a matrix). The chemical composition of both phases, Fe66.2Al23.3Ti10.5 for cuboids and Fe81Al19 (with about 1% or less of Ti) for the matrix, was determined from an Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The phase of cuboids is found to be a rather strongly off-stoichiometric (Fe-rich and Ti-poor) variant of Heusler Fe2TiAl intermetallic compound with the L21 structure. The phase of the matrix is a solid solution of Al atoms in a ferromagnetic body-centered cubic (bcc) Fe. Quantum-mechanical calculations were employed to obtain an insight into elastic properties of the two phases. Three distributions of chemical species were simulated for the phase of cuboids (A2, B2 and L21) in order to determine a sublattice preference of the excess Fe atoms. The lowest formation energy was obtained when the excess Fe atoms form a solid solution with the Ti atoms at the Ti-sublattice within the Heusler L21 phase (L21 variant). Similarly, three configurations of Al atoms in the phase of the matrix with different level of order (A2, B2 and D03) were simulated. The computed formation energy is the lowest when all the 1st and 2nd nearest-neighbor Al-Al pairs are eliminated (the D03 variant). Next, the elastic tensors of all phases were calculated. The maximum Young’s modulus is found to increase with increasing chemical order. Further we simulated an anti-phase boundary (APB) in the L21 phase of cuboids and observed an elastic softening (as another effect of the APB, we also predict a significant increase of the total magnetic moment by 140% when compared with the APB-free material). Finally, to validate these predicted trends, a nano-scale dynamical mechanical analysis (nanoDMA) was used to probe elasticity of phases. Consistent with the prediction, the cuboids were found stiffer.

A neutron diffraction study on a typical highly defective ceria–yttria solid solution

2002 ◽  
Vol 17 (4) ◽  
pp. 278-280 ◽  
Author(s):  
Keka R. Chakraborty ◽  
S. V. Chavan ◽  
A. K. Tyagi
Keyword(s):  
Solid Solution ◽  
Diffraction Study ◽  
Room Temperature ◽  
Fluorite Structure ◽  
Neutron Diffraction Study ◽  
Neutron Powder Diffraction ◽  
Face Centered Cubic ◽  
Aliovalent Substitution ◽  
Face Centered ◽  
The Ideal

It was seen during the phase relation studies on the CeO2–YO1.5 system that the ceria is able to accommodate a large anion deficiency caused by aliovalent substitution. A neutron powder diffraction study has been carried out at room temperature for the titled solid solution, Ce1−xYxO2−x/2 with x=0.32, which is an anion-deficient variant of the ideal fluorite structure. The structure has been found to be face centered cubic. No superlattice reflections have been observed indicating that the vacancies occupy the random positions in this highly defective solid solution. The bond distances and angles are also being reported.

Ganophyllite from Franklin, New Jersey; Pajsberg, Sweden; and Wales new chemical data

1983 ◽  
Vol 47 (345) ◽  
pp. 563-566 ◽  
Author(s):  
Pete J. Dunn ◽  
Donald R. Peacor ◽  
Joseph E. Nelen ◽  
Robert A. Ramik
Keyword(s):  
Solid Solution ◽  
New Jersey ◽  
Chemical Composition ◽  
Water Content ◽  
General Structure ◽  
Chemical Data ◽  
Upper Limit ◽  
Octahedral Cations

AbstractGanophyllite from Franklin, New Jersey, Pajsberg, Sweden, and the Benallt Mine, Wales, has been chemically reinvestigated. Twelve new analyses confirm the general structure of Kato (1980) and yield the tentative formula (K,Na,Ca)2Mn8(Si,Al)12(O,OH)32(OH)4·8H2O. There is little solid solution among octahedral cations, and the Si:Al ratio is nearly constant at 10:2. Ca and (Na + K) are apparently differentiated, but all examined ganophyllites are K-rich. Much of the water content is loosely bound and the upper limit of water content is not well defined. Ganophyllite is relatively invariant in chemical composition from locality to locality.

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