Effect of Synthesis Conditions on Phase Composition of Pyrochlore-Brannerite Ceramics

2000 ◽  
Vol 663 ◽  
Author(s):  
S.V. Stefanovsky ◽  
S.V. Yudintsev ◽  
B.S. Nikonov ◽  
M.I. Lapina ◽  
A.S. Aloy
Keyword(s):  
Solid Solution ◽  
Phase Composition ◽  
High Temperatures ◽  
Microwave Oven ◽  
Redox Conditions ◽  
Cold Crucible ◽  
Synthesis Conditions ◽  
The Third ◽  
Three Samples

ABSTRACTThree melted samples of pyrochlore-brannerite-based ceramics produced under different redox conditions were examined. Two of the samples were produced using cold crucible melting at ~1600 C. The third sample was obtained via melting in a microwave oven at 1700-1800 C. All the samples are composed of major pyrochlore and brannerite phases, and minor rutile and UO2-based solid solution or pseudobrookite phases. Pyrochlore-structured phases predominate in all three samples and account for 50-60% of the total bulk. Two pyrochlore varieties – Ca-pyrochlore (predominant) and Ba-pyrochlore have been found in these samples. The latter phase is more stable at high temperatures than the Ba-hollandite present in sintered pyrochlore-rich Synroc-F ceramics. Decomposition of the Ba-hollandite results in rutile formation in the melted samples.

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.

High temperatures (>1000 °C) monitoring during the sintering process in microwave oven using RFBGs

2016 ◽  
Vol 48 (5) ◽  
Author(s):  
Daniel Pereira ◽  
Tiago Santos ◽  
Rogério Nogueira ◽  
Luís C. Costa ◽  
Nélia Alberto
Keyword(s):  
High Temperatures ◽  
Microwave Oven ◽  
Sintering Process

Strain hardening of pre-fatigued Ag-5 at% Cu solid solution at high temperatures

1977 ◽  
Vol 44 (1) ◽  
pp. K53-K57 ◽  
Author(s):  
E. Kamel ◽  
E. Aziz ◽  
K. H. Georgy
Keyword(s):  
Solid Solution ◽  
Strain Hardening ◽  
High Temperatures

Selective Oxidation and the Third-Element Effect on the Oxidation of Mg-Y Alloys at High Temperatures

2009 ◽  
Vol 40 (9) ◽  
pp. 2184-2189 ◽  
Author(s):  
J.F. Fan ◽  
G.C. Yang ◽  
Y.H. Zhou ◽  
Y.H. Wei ◽  
B.S. Xu
Keyword(s):  
Selective Oxidation ◽  
High Temperatures ◽  
The Third

Changes in the structure of a thermal protective aluminum-nickel coating under the influence of a single thermal laser pulse

2021 ◽  
Vol 4 ◽  
pp. 25-30
Author(s):  
O. B. Berdnik ◽  
◽  
P. Yu. Kikin ◽  
V. N. Perevezentsev ◽  
E.N. Razov ◽  
...  
Keyword(s):  
Solid Solution ◽  
Heat Flux ◽  
Phase Composition ◽  
Nickel Coating ◽  
Microstructural Analysis ◽  
Radiation Energy ◽  
Heat Fluxes ◽  
Initial State ◽  
Nial Phase ◽  
Ni3al Phase

The regularities of changes in the structure and phase composition of the thermal protective aluminide-nickel coating (Ni — 45 %; Al — 14 %; Co — 22 %; Cr — 18.9 %; Fe — 0.15 %; Nb — 0.14 %; Y — 0.09 %; Ca — 0.06 %; Mn — 0.01 %; C — 0.15 %; Si — 0.15 %; S — 0.006 %) after exposure to short-term pulsed heat fluxes of various power, created by the radiation of a pulse-periodic laser LRS-150A with a radiation wavelength λ = 1.06 µm and a pulse duration τ = 12·10–3 s. The radiation energy was E = 5, 10, and 15 J. Microstructural analysis and the elemental composition of the resulting coating were carried out as well as analysis of the phase composition. X-ray microanalysis of the coating was also carried out. In the initial state and after irradiation of the coating with a heat flux of power P = 7·103 W/cm2, light microregions are observed in the micrographs of the surface. These regions do not have clearly defined external boundaries and consist of the NiAl phase and a small amount of the Ni3Al phase with the presence of inclusions of particles containing a solid solution of Ni – Co – Cr. After irradiation of the coating with heat fluxes of higher power (P = 1.7·104 W/cm2 and P = 2.2·104 W/cm2), large convex formations appeared on its surface, consisting mainly of Ni3Al and NiAl phases. On micrographs of the surface, they appear as white areas with well-defined outer boundaries. The content of the Ni3Al phase in them in comparison with the initial state increased, and the content of the NiAl phase decreased, while the particles of inclusions of Ni, Co, and Cr disappeared. It can be assumed that an increase in the Ni3Al content is associated with the dissolution of particles of a solid solution of Ni – Co and Cr in the melt and the subsequent diffusion of nickel into the NiAl phase. When exposed to a heat flux of power P = 2.2·104 W/cm2, microcracks appear on the areas of the coating surface covered with aluminum oxide.

Performance Studies on In Situ Spinel Solid Solution Bonded Periclase Refractories

2014 ◽  
Vol 633 ◽  
pp. 245-248
Author(s):  
Xin Lin ◽  
Yong Li ◽  
Yan Jing Li ◽  
Jun Jie Zhang ◽  
Chang He Gao ◽  
...  
Keyword(s):  
Solid Solution ◽  
Phase Composition ◽  
Performance Studies ◽  
Magnesium Aluminate ◽  
Spinel Solid Solution ◽  
Magnesium Aluminate Spinel ◽  
Crushing Strength ◽  
Cold Crushing Strength ◽  
Shock Resistance

Specimens were prepared using iron-rich magnesia (3~1 mm、≤1 mm) and high purity magnesia (≤0.088 mm) as the main starting materials, adding tabular alumina at different size (3~2、2~1、≤1 mm) and content:3%、6%、9%、12%、15% to discover the influence of tabular alumina on sample performance. Phase composition and microstructure were also analyzed. The results show that specimen with content of 6% of corundum possessed the best comprehensive performance:apparent porosity 17%, bulk density 2.95 g·cm-3, cold crushing strength 74 MPa, refractoriness under load 1700 °C, heat shock resistance of up to 18 times. The formations of magnesium aluminate spinel and hercynite solid solution were enhanced by Fe ion at high temperatures in the iron-rich magnesia-corundum system at the presence of iron oxides, which are able to largely dissolved in periclase.

Effects of hydrogen on the microstructure and microchemistry of Ti3Al – Nb intermetallics at high temperatures and high pressures

1996 ◽  
Vol 11 (9) ◽  
pp. 2186-2197 ◽  
Author(s):  
H. Z. Xiao ◽  
I. M. Robertson ◽  
H. K. Birnbaum
Keyword(s):  
Solid Solution ◽  
High Temperatures ◽  
High Pressures ◽  
Chemical Potential ◽  
Substitutional Solid Solution ◽  
Hydrogen Gas ◽  
Solid Solution Phase ◽  
Face Centered Cubic ◽  
Fine Grained ◽  
Surrounding Matrix

The microstructural and microchemical changes produced in a Ti–25Al–10Nb–3V–1Mo alloy (at. %) by charging at high temperatures in high pressures of hydrogen gas have been studied using transmission electron microscopy (TEM) and x-ray methods. Hydrides incorporating all of the substitutional solutes that formed during charging have a face-centered cubic (fcc) structure and exhibit either a plate or fine-grained morphology. With increasing hydrogen content, the size of the hydrides decreases and their microchemistry changes as they approach the stable binary hydride, TiH2. Rejection of substitutional solute elements from the hydride produces changes in the microchemistry, and consequently in the crystal structure, of the surrounding matrix. In alloys containing 50 at. % H, this solute redistribution results in the formation of an orthohombic substitutional solid solution phase containing increased levels of Nb. The driving force of this redistribution of solutes is the reduction in the chemical potential of the system as the amount of the most stable hydride, TiH2, forms. The hydrides reverted to a solid solution on annealing in vacuum at 1073 K, and the original microchemistry of the alloy was restored. Reversion from the hydride structure to the original α2 ordered DO19 structure proceeds via a disordered HCP phase.

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