The use of an electric field as a processing parameter in the combustion synthesis of ceramics and composites
- Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science
The use of electric field to activate the process of self-propagating high-temperature (SHS) is demonstrated. Experimental observations show that for several systems, combustion synthesis is only possible with the presence of a field. Modeling studies on the synthesis of {beta}-SiC have shown the effect of field is localized in the combustion zone and that the magnitude of this effect is related to {delta}E{sup 2} where {delta} is the electric conductivity and E is the field. The modeling studies showed a linear dependence between the combustion wave velocity and the applied voltage. Experimental results show a similar relationship between velocity and voltage with a dependence on the initial relative density of the reactant compacts. Investigations on the mechanism in field-activated synthesis were also made. The results confirm a model in which the rate of heat release from the field in the combustion zone is enhanced by the presence of a molten phase, Si in the case of synthesis of silicon carbide. The effect of field on the SHS reactions was also investigated for the synthesis of composite materials. Composites of MoSi{sub 2}-SiC, MoSi{sub 2}-ZrO{sub 2}, MoSi{sub 2}-Nb and B{sub 4}C-TiB{sub 2} were formed by field-activated combustion synthesis. In the case of MoSi{sub 2}-SiC, composites with molar ratios of SiC/MoSi{sub 2}(=x) ranging from zero to one have been prepared by this method. In the absence of a field no SHS reaction is possible for x > 0. Similarly, in the case of B{sub 4}C-TiB{sub 2}, composites with B{sub 4}C/TiB{sub 2}(=y) ratios of one or larger can only be synthesized in the SHS mode in the presence of a field.
- OSTI ID:
- 77975
- Report Number(s):
- CONF-950201-; ISBN 0-87339-283-3; TRN: IM9531%%25
- Resource Relation:
- Conference: Annual meeting and exhibition of the Minerals, Metals and Materials Society (TMS), Las Vegas, NV (United States), 12-16 Feb 1995; Other Information: PBD: 1995; Related Information: Is Part Of In situ reactions for synthesis of composites, ceramics, and intermetallics; Barrera, E.V.; Marquis, F.D.S.; Frazier, W.E.; Fishman, S.G.; Thadhani, N.N.; Munir, Z.A.; PB: 226 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Properties of in situ TiAl- and MoSi{sub 2}-base composites produced by reactive processing
Extending the compositional limit of combustion-synthesized B{sub 4}C-TiB{sub 2} composites by field activation