Surface diffusion of high temperature vapors in porous alumina
The purpose of this study was to determine whether surface diffusion contributed significantly to the transport of zinc vapor through porous aluminas of 0.6 ..mu..m and 0.07 ..mu..m average pore radii. Zinc and zinc sulfide solids were vaporized into vacuum from a boron nitride cell covered with a porous alumina barrier. Zinc vapor fluxes through the barrier were determined using a weight loss technique. The flux of helium through the alumina was also determined from the leak rate at room temperature. After correction for molecular weight differences, any flux of zinc greater than that of helium was attributed to surface diffusion. In all experiments, Knudsen flow was operative in the gas phase. The ratio of surface flux to Knudsen flux for Zn/sub (g)/ from Zn/sub (s)/ in alumina of 0.6 ..mu..m average pore size at 647/sup 0/K was 2.5. It was found that using alumina of 0.07 ..mu..m average pore radius under the same experimental conditions increased the surface to Knudsen flux ratio to 17. This increase was proportional to the inverse of the average pore radius as predicted. The flux of zinc vapor from Zn/sub (s)/ at 592/sup 0/K and ZnS/sub (s)/ at 1092/sup 0/K was measured where P/sub Zn/ was nearly equal using alumina of 0.6. ..mu..m average pore radius. In both cases, the amount of zinc vapor transmitted and the ratio of surface to Knudsen flux for zinc was the same. It was concluded that the presence of S/sub 2//sub (g)/ had no observable effect on the diffusion of zinc vapor in porous alumina.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6597423
- Report Number(s):
- LBL-16735; ON: DE84015968
- Resource Relation:
- Other Information: Portions are illegible in microfiche products. Thesis
- Country of Publication:
- United States
- Language:
- English
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Surface diffusion of high temperature vapors in porous alumina
Related Subjects
ALUMINIUM OXIDES
PERMEABILITY
ZINC
DIFFUSION
HIGH TEMPERATURE
POROUS MATERIALS
SULFUR
VAPORS
VERY HIGH TEMPERATURE
ZINC SULFIDES
ALUMINIUM COMPOUNDS
CHALCOGENIDES
ELEMENTS
FLUIDS
GASES
INORGANIC PHOSPHORS
MATERIALS
METALS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHOSPHORS
SULFIDES
SULFUR COMPOUNDS
ZINC COMPOUNDS
360202* - Ceramics
Cermets
& Refractories- Structure & Phase Studies