Investigation of Elongation and its Relationship to Residual Stresses in Boron Filaments.
Abstract
Measurements have been made to determine elongation on boron filaments while they are being produced by chemical vapor deposition. To date the primary variable that appears to influence the elongation is deposition temperature which verifies earlier results. Small amounts of additives of silicon and tungsten have been incorporated into the filaments via the gas phase to determine if this approach would minimize the elongation. No positive results were obtained. Structural and microstructural studies on the filaments using transmission electron microscopy and diffraction have shown an apparent difference in boron at the surface and that near the core. The surface material appears to grow in a column type structure approximately 1000 A in diameter. No evidence of microcrystals of one of the crystalline polymorphs has been obtained. The filaments were observed to contract by almost 2% after 10 minutes at 900 C. Examination of the cross section of these filaments show extensive void formation in the region adjacent to the core. The experiments suggest that boron is being removed by a surface reaction.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 01, 1978
- Accession Number
- ADA056528
Entities
People
- Franklin E. Wawner Jr.
Organizations
- University of Virginia