Synthesis, characterization, and fabrication of silicon carbide structural ceramics. [SiC-TiC-BN]
Five processes of SiC powder synthesis were investigated: chemical vapor decomposition, high-temperature rotary-furnace reactions, gel synthesis of precursors followed by carbothermic reduction, pyrolysis of polymeric precursors, and the Acheson process. Exploratory powder synthesis experiments were conducted on the gel process involving gelation of colloidal silica and petroleum pitch in toluene, or polymerization of methyltrimethoxysilane and resin in alcohol. The ..beta..-SiC powders synthesized by these gel processes have specific surface areas (SSA) exceeding 20 m/sup 2//g and round or polyhedral particle shape. These materials have excellent pressure sintering capability. SiC powder made by the rotary-furnace process consists of fine ..beta..-SiC particles with a round morphology and about 10 m/sup 2//g SSA. The rotary-furnace SiC powders with BN dopants were hot pressed to 95% dense. A commercial polycarbosilane prepared from dechlorination and polymerization reactions of vinyl and chloromethyl silanes was pyrolyzed and hot pressed without BN to 79% dense. In terms of pressureless sintering, the best result (96+% dense) is obtained with the Starck-SiC powder by doping with 0.8 wt % B and 2 wt % phenolic resin and sintering under argon in a graphite furnace for 2 h at 2050/sup 0/C. An SiC-TiC-BN composite was hot pressed to 97+% dense with an indentation toughness nearly double that of sintered ..beta..-SiC. 10 figures, 6 tables.
- Research Organization:
- Oak Ridge National Lab., TN (USA)
- DOE Contract Number:
- W-7405-ENG-26
- OSTI ID:
- 6651072
- Report Number(s):
- CONF-821145-2; ON: DE83003281
- Resource Relation:
- Conference: 7. materials for coal conversion and utilization conference, Gaithersburg, MD, USA, 16 Nov 1982; Other Information: Mf only; illegibility does not permit PC reproduction
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
BORON NITRIDES
FABRICATION
SILICON CARBIDES
TITANIUM CARBIDES
COMPOSITE MATERIALS
ELECTRON MICROSCOPY
FLOWSHEETS
FRACTURE PROPERTIES
GELS
HOT PRESSING
MICROSTRUCTURE
POWDERS
SINTERING
SURFACE AREA
SYNTHESIS
BORON COMPOUNDS
CARBIDES
CARBON COMPOUNDS
COLLOIDS
CRYSTAL STRUCTURE
DIAGRAMS
DISPERSIONS
MATERIALS
MATERIALS WORKING
MECHANICAL PROPERTIES
MICROSCOPY
NITRIDES
NITROGEN COMPOUNDS
PNICTIDES
PRESSING
SILICON COMPOUNDS
SURFACE PROPERTIES
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360201* - Ceramics
Cermets
& Refractories- Preparation & Fabrication
360301 - Composite Materials- Preparation & Fabrication- (-1987)