Experimental Determination of Dissolution Kinetics of Zr-Substituted Gd-Ti Pyrochlore Ceramics: Influence of Chemistry on Corrosion Resistance

2002 ◽  
Vol 757 ◽  
Author(s):  
Icenhower J.P. ◽  
Weber W.J. ◽  
Hess N.J. ◽  
Thevuthasen S. ◽  
Begg B.D. ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Dissolution Kinetics ◽  
Fluorite Structure ◽  
Annealed Specimen ◽  
Face Centered Cubic ◽  
Zirconium Content ◽  
The Face ◽  
Flow Through ◽  
Face Centered

ABSTRACTThe corrosion resistance of a series of zirconium-substituted gadolinium pyrochlore, Gd2(Ti1-x Zrx)2O7, where x = 0.0, 0.25, 0.50, 0.75, and 1.00, were evaluated using single-pass flow-through (SPFT) apparatus at 90°C and pH = 2. The zirconate end-member, Gd2Zr2O7, has a defect fluorite structure, which distinguishes it from the face-centered cubic structure of the true pyrochlore specimens. In addition to the chemical variation, the samples include annealed, un-annealed, and ion-bombarded monoliths. In the case of the titanate end-member, Gd2Ti2O7, the annealed specimen exhibited the least reactivity, followed by the un-annealed and ion-bombarded samples (2.39×10-3, 1.57×10-2, and 1.12×10-1 g m-2 d-1, respectively). With increasing zirconium content, the samples displayed less sensitivity to processing or surface modification with the zirconate end-member exhibiting no difference in reactivity between annealed, un-annealed, and ion-bombarded specimens (rate = 4.0×10-3 g m-2 d-1). In all cases, the dissolution rate decreased with increasing zirconium content to the Gd2(Ti0.25Zr0.75)2O7 composition (1.33x10-4 g m-2 d-1), but the zirconate end-member yielded rates nearly equal to that of the titanate end-member. These results demonstrate that to achieve the greatest radiation and corrosion resistance in this series, the Gd2(Ti0.25Zr0.75)2O7 composition should be considered.

The determination of solute atom displacements in mixed dumbbell interstitials for the face-centered-cubic lattice

1978 ◽  
Vol 56 (8) ◽  
pp. 1057-1070 ◽  
Author(s):  
N. Matsunami ◽  
M. L. Swanson ◽  
L. M. Howe
Keyword(s):  
Solute Atom ◽  
The Body ◽  
Continuum Approximation ◽  
Face Centered Cubic ◽  
Cubic Lattice ◽  
The Face ◽  
Solute Atoms ◽  
Face Centered ◽  
Small Solute

Interactions between irradiation-produced defects and solute atoms in metals have been investigated using the channeling technique. The interaction of interest in this investigation is the trapping of self interstitials by small solute atoms thus creating a [Formula: see text] mixed dumbbell, consisting of a host atom and a solute atom straddling a lattice site in the face-centered-cubic lattice. The displacement of solute atoms from lattice sites in the mixed dumbbell configuration was determined by comparing the experimentally observed normalized yields from solute atoms and from host atoms with the yields calculated analytically using the continuum approximation. The solute atoms in Al–Mn, Al–Cu, and Cu–Be mixed dumbbells were situated at 0.5 Å from the body-centered position, whereas the Ag atoms in Al–Ag dumbbells were 0.7 Å from this position. This result is consistent with the theoretical expectation that the smallest solute atoms are displaced the greatest amount in mixed dumbbells. In addition, experimentally obtained solute atom yields for [Formula: see text] and [Formula: see text] angular scans were compared with calculated scans. It was concluded that for large displacements of solute atoms into the flux peaking region, the analytical (continuum) calculation is a reliable method of determining solute atom displacements, either from the aligned yields or from the angular scans.

scholarly journals Analysis of luminescence of Eu3+ doped Lu2Ti2O7 powders with Judd-Ofelt theory

2015 ◽  
Vol 38-39 (1) ◽  
pp. 23-32 ◽  
Author(s):  
Katarina Vuković ◽  
Sanja Ćulubrk ◽  
Milica Sekulić ◽  
Miroslav D. Dramićanin
Keyword(s):  
Emission Spectra ◽  
Quantum Yields ◽  
Optical Parameters ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Ofelt Theory ◽  
The Face ◽  
Face Centered ◽  
The Eu

Abstract Eu3+ doped Lu2Ti2O7 particles of 6 to 10 nm in diameter are prepared by Pechini-type polymerized complex route based on polyesterification between citric acid (CA) and ethylene glycol. X-ray diffraction measurements confirmed that Eu3+ doped Lu2Ti2O7 powders crystallized in the face-centered cubic lattice (Fd3m). Emission spectra displayed characteristic 5D0 →7 FJ (J = 0, 1, 2, 3 and 4) spin forbidden f-f electronic transitions of the Eu3+ ions with the most pronounced emission coming from 5D0 →7 F2 and with the emission decays varying between 0.75 and 0.60 ms for samples doped with different concentration of Eu3+. The Judd-Ofelt theory was applied to the experimental data for the quantitative determination of optical parameters such as Ω2, Ω4 Judd-Ofelt parameters, radiative and nonradiative transition rates and emission quantum efficiency. It was observed that, for all the samples, Ω2 >> Ω4. The luminescence quantum yields were calculated by means of the Judd-Ofelt theory and the highest value 60.83 % is obtained for particles doped with concentration of 3 % Eu3+.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

NICROFER 5923 HMo-ALLOY 59

Alloy Digest ◽  
1993 ◽  
Vol 42 (5) ◽  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Heat Treating ◽  
Face Centered Cubic ◽  
Low Carbon ◽  
High Alloy ◽  
Temperature Performance ◽  
Cubic Structure ◽  
Face Centered

Abstract NICROFER 5923 hMo, often called Alloy 59, was developed with extra low carbon and silicon contents and with a high alloy level of molybdenum to optimize its corrosion resistance. Nicrofer 5923hMo has a face-centered cubic structure. This datasheet provides information on composition, physical properties, elasticity, and tensile properties. It also includes information on high temperature performance as well as forming, heat treating, and joining. Filing Code: Ni-430. Producer or source: VDM Technologies Corporation.

MINIMAL KNOTTING NUMBERS

2009 ◽  
Vol 18 (08) ◽  
pp. 1159-1173 ◽  
Author(s):  
CASEY MANN ◽  
JENNIFER MCLOUD-MANN ◽  
RAMONA RANALLI ◽  
NATHAN SMITH ◽  
BENJAMIN MCCARTY
Keyword(s):  
The Body ◽  
Computer Algorithm ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Lattice ◽  
The Face ◽  
Face Centered ◽  
Body Centered Cubic Lattice

This article concerns the minimal knotting number for several types of lattices, including the face-centered cubic lattice (fcc), two variations of the body-centered cubic lattice (bcc-14 and bcc-8), and simple-hexagonal lattices (sh). We find, through the use of a computer algorithm, that the minimal knotting number in sh is 20, in fcc is 15, in bcc-14 is 13, and bcc-8 is 18.

Poisson's Ratio for Central-Force Polycrystals

1976 ◽  
Vol 31 (12) ◽  
pp. 1539-1542 ◽  
Author(s):  
H. M. Ledbetter
Keyword(s):  
Electron Energy ◽  
Poisson Ratio ◽  
The Body ◽  
Central Force ◽  
Face Centered Cubic ◽  
Polycrystalline Aggregate ◽  
Body Centered Cubic ◽  
The Face ◽  
Predicted Values ◽  
Face Centered

Abstract The Poisson ratio υ of a polycrystalline aggregate was calculated for both the face-centered cubic and the body-centered cubic cases. A general two-body central-force interatomatic potential was used. Deviations of υ from 0.25 were verified. A lower value of υ is predicted for the f.c.c. case than for the b.c.c. case. Observed values of υ for twenty-three cubic elements are discussed in terms of the predicted values. Effects of including volume-dependent electron-energy terms in the inter-atomic potential are discussed.

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