Development of a Commercial Process for the Production of Silicon Carbide Fibrils
A patent was issued on ''VLS'' silicon carbide fibrils to North American Phillips Corporation in 1975. Various laboratories and companies have been attempting to improve this process and scale it to larger quantities since that time. All of these efforts met with minimal success because they were using the original technology while attempting to improve the equipment. The principal impediments have been: (1) Slow crystal growth during fibril production; (2) Sensitive stoichiometry factors in the crystal growth chamber; and (3) Precise control of a high temperature process. The principal investigator has scaled silicon carbide whisker production at American Matrix and the SiC fiber process at Advanced Composite Materials Corporation from grams in the laboratory to tons per year production. This project is a proof-of-concept effort to apply some of the recent technology to the problems listed above in the fibril growth process. Two different technology approaches were investigated. A major problem with fibril growth has been generating a consistent supply of the required SiO gas reactant, which is a product of reducing SiO{sub 2}. The first approach, in this project addresses the SiO gas production, involved mixing silica and carbon fibrous raw materials in the immediate proximity of the graphite fibril growth plates to generate SiO nearer to individual sites of fibril growth. Iron bearing catalyst was painted on the graphite plates and the SiO generator mix was placed above the plate. This system was then heated to 1600/1650 C in a graphite resistance furnace. Some fibrils were started but the growth rate and fibril quality were unacceptably low. A second approach, which uses MTS + H{sub 2} gases to address stoichiometry control, was investigated to improve fibril growth rates while reducing the previous high temperature requirements for the process. A partial vacuum chamber was construct inside a commercial microwave furnace. The fibril growth container was coated with an iron catalyst and brought to 1200 C by the microwave field. A mixture of hydrogen and methyl trichlorosilane gases were fed to the fibril reaction container. Excellent silicon carbide fibrils were produced at a growth rate that was over four times greater than previously reported processes. The next phase of the development will be an optimization of operating parameters to improve fibril yield in the microwave growth process. The development activities will then move to the construction and testing of a pilot unit.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Fossil Energy (FE) (US)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 7914
- Report Number(s):
- ORNL/SUB/86X-SZ337V; TRN: AH200116%%128
- Resource Relation:
- Other Information: PBD: 1 Apr 1999
- Country of Publication:
- United States
- Language:
- English
Similar Records
Development of a Commercial Process for the Production of Silicon Carbide Fibrils - Draft Phase II Final Report
New concepts and designs for blast furnace linings and cooling systems