Degree Type
Dissertation
Date of Award
1984
Degree Name
Doctor of Philosophy
Department
Chemistry
Abstract
Experiments have been performed to help elucidate the high temperature phase diagram features and thermodynamic properties of the zirconium-aluminum system. The principal methods used were combinations of high temperature Knudsen effusion, heat treatment, and X-ray powder diffraction experiments performed with zirconium-aluminum samples in the composition range 0 < X(,Al) < 0.75. The results of these experiments confirmed in some respects the phase diagram features of Potschke and Schubert,('1) two previous investigators. In particular, X-ray powder diffraction experiments performed on samples in the composition range 0.50 < X(,Al) < 0.60 quenched from 800-1400(DEGREES)C indicate that ZrAl is stable below 1250(DEGREES)C, Zr(,4)Al(,3) below 1000(DEGREES)C, and Zr(,5)Al(,4) above about 1100(DEGREES)C;Aluminum vapor pressures were measured over compositions corresponding to mixtures of two solid phases between the com- positions ZrAl(,3) and Zr(,5)Al(,3), and as a function of composition over the solid solution of aluminum in bcc zirconium using a combined mass-loss-mass-spectrometric Knudsen effusion technique. In order to successfully measure the low aluminum pressures (less than (TURN)10('-8) atm) over the more zirconium-rich samples it was necessary to use a small computer to signal average the mass-spectrometer signal. Data collected over 7 two-phase regions and the solid solutions were used to calculate enthalpies of formation at 298 K of seven zirconium-aluminum compounds. The heat of formation values (kcal/mole) obtained were: ZrAl(,3) = -38.96, ZrAl(,2) = -32.86, Zr(,2)Al(,3) = -56.12, ZrAl = -21.36, Zr(,5)Al(,4) = -93.76, Zr(,3)Al(,2) = -48.78, and Zr(,5)Al(,3) = -74.57;A nonrelativistic, nonself-consistent band structure calculation for the compound Zr(,2)Al was performed in an attempt to provide insight;into the type of chemical bonding occurring in zirconium-aluminum compounds; *DOE Report IS-T-1148. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Oil, Gas, and Energy;('1)Potschke, M; Schubert, K. Z. Metallkde 1962, 53, 548.
DOI
https://doi.org/10.31274/rtd-180813-12535
Publisher
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Copyright Owner
Robert Joseph Kematick
Copyright Date
1984
Language
en
Proquest ID
AAI8505833
File Format
application/pdf
File Size
137 pages
Recommended Citation
Kematick, Robert Joseph, "High temperature thermodynamics of the zirconium-aluminum system " (1984). Retrospective Theses and Dissertations. 8179.
https://lib.dr.iastate.edu/rtd/8179