Energy and Tangential Momentum Accommodation on Different Flashed Tungsten and Gas Covered Tungsten Surfaces.
Abstract
The acoustical method has been used to determine energy and tangential momentum accommodation coefficients on three different polycrystalline tungsten surfaces. To obtain the second surface, the first was highly oxidized and then cleaned by vacuum flashing at 2150 K. The third surface, manufactured by the same chemical deposition process as the first, was specified as having 1/2 the microscopic roughness of the first. Photographs made with the scanning electron microscope indicate that though the oxidation dramatically increased the roughness of the surface, this roughness was removed in the flashing process. The electron micrographs also showed that flashing dramatically increased the grain size in the third surface. This third surface, though supposedly smoother, was found to have larger AC values than the first. This has been attributed to a shorter accumulated flashing time at the time the measurements were made and, therefore, smaller grain size. The microscopic roughness does not appear to be an important factor in determining AC values after the surface is flashed. The problem of simultaneously determining energy and tangential momentum accommodation coefficients is discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 29, 1981
- Accession Number
- ADA107495
Entities
People
- F. Douglas Shields
Organizations
- University of Mississippi