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Hydrogen-Induced Phase Separation of Palladium-Rhodium Alloys Using an Environmental Cell TEM

Published online by Cambridge University Press:  02 July 2020

D.F. Teter
Affiliation:
Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM, 87545
R.D. Field
Affiliation:
Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM, 87545
D.J. Thoma
Affiliation:
Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM, 87545
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The palladium-rhodium system has been extensively studied for its hydrogen absorption characteristics. However, the phase diagram of the palladium-rhodium system has not been conclusively determined below 800 K. Shield and Williams have experimentally determined the incoherent miscibility gap in Pd-Rh alloys using electrical resistivity studies, however the coherent miscibility gap and spinodal have not been determined. Recently work by Noh and Flanagan has suggested that hydrogen enhances metal atom mobility and may increase the kinetics of phase separation in Pd-Rh alloys. Field and Thoma found that hydrogen causes a Pd-10%Rh alloy to decompose during an in situhydrogen charging experiment in an environmental cell TEM. According to the calculations by Gonis et al. of the miscibility gap for the palladium-rhodium system, the Pd-10%Rh alloy may be within the chemical spinodal at room temperature.

In this work, two palladium-rhodium compositions were investigated. The first was a Pd-10 at.% Rh alloy produced by melt-spinning, and the second was a Pd-30at.

%Rh alloy which had been arc-melted and cold rolled followed by an annealing treatment to homogenize the material. TEM specimens were prepared by punching 3 mm disks from the material.

Type
In Situ Studies in Microscopy
Copyright
Copyright © Microscopy Society of America 1997

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References

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