THORIUM OXIDE-DIFFUSION OF OXYGEN, COMPATIBILITY WITH BORIDES, AND FEASIBILITY OF COATING BORIDES BY PYROHYDROLYSIS OF METAL HALIDES
Measurements of self-diffusion of oxygen in ThO/sub 2/ were complicated by slow exchange at the surface. The measured values of the diffusion coefficient, D, ranged from 1.8 x 10/sup -13/ cm/sup 2//sec at 800 deg C to 3.5 x 10/sup -8/ cm/sec at 1500 deg C. The rate constant of the surface reaction, K, ranged from 6.8 x 10/sup -10/ cm/sec at 800 deg C to 1.3 x 10/sup -4/ cm/sec at 1500 deg C. The results may be expressed by equations in the form of D = 4.4 exp (.-65,800/RT) cm/sup 2//sec and K = 7.6 x 103 exp (--83,800/RT) cm/sec. Attempts to deposit dense impervious layers of ThO/sub 2/ on selected solid borides by pyrohydrolysis of ThCl/sub 4/ were essentially unsuccessful. The main problem was attack of the borides by CO/sub 2/ in the coating gas. The pyrohydrolysis technique might prove to be an economical way to build up a coating of ThO/sub 2/ that was started by another method. The commercially available boride samples which were tested reacted with graphite in the temperature range of 2400 to 2700 deg C. Because of these reactions, a graphite-boridethoria system will be useful for only limited times at temperatures above 2400 deg C. While pure borides were not investigated, it is expected that their behavior would be similar to that of the commercial samples examined in this work. (auth)
- Research Organization:
- General Electric Co. Advanced Technology Services, Cincinnati
- DOE Contract Number:
- AF33(657)-8470
- NSA Number:
- NSA-17-032564
- OSTI ID:
- 4669831
- Report Number(s):
- ASD-TDR-63-635
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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