Chemical vapor deposited fiber coatings and chemical vapor infiltrated ceramic matrix composites
Conventional Chemical Vapor Deposition (CVD) and Organometallic Chemical Vapor Deposition (MOCVD) were employed to deposit a series of interfacial coatings on SiC and carbon yarn. Molybdenum, tungsten and chromium hexacarbonyls were utilized as precursors in a low temperature (350[degrees]C) MOCVD process to coat SiC yarn with Mo, W and Cr oxycarbides. Annealing studies performed on the MoOC and WOC coated SiC yarns in N[sub 2] to 1,000[degrees]C establish that further decomposition of the oxycarbides occurred, culminating in the formation of the metals. These metals were then found to react with Si to form Mo and W disilicide coatings. In the Cr system, heating in N[sub 2] above 800[degrees]C resulted in the formation of a mixture of carbides and oxides. Convention CVD was also employed to coat SiC and carbon yarn with C, Bn and a new interface designated BC (a carbon-boron alloy). The coated tows were then infiltrated with SiC, TiO[sub 2], SiO[sub 2] and B[sub 4]C by a chemical vapor infiltration process. The B-C coatings were found to provide advantageous interfacial properties over carbon and BN coatings in several different composite systems. The effectiveness of these different coatings to act as a chemically inert barrier layer and their relationship to the degree of interfacial debonding on the mechanical properties of the composites were examined. The effects of thermal stability and strength of the coated fibers and composites were also determined for several difference atmospheres. In addition, a new method for determining the tensile strength of the as-received and coated yarns was also developed. The coated fibers and composites were further characterized by AES, SEM, XPS, IR and X-ray diffraction analysis.
- Research Organization:
- Connecticut Univ., Storrs, CT (United States)
- OSTI ID:
- 5519890
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COATINGS
MECHANICAL PROPERTIES
STRUCTURAL CHEMICAL ANALYSIS
ORGANOMETALLIC COMPOUNDS
CHEMICAL VAPOR DEPOSITION
CARBON
CERAMICS
CHROMIUM COMPOUNDS
COMPOSITE MATERIALS
FIBERS
INTERFACES
MATRIX MATERIALS
MOLYBDENUM COMPOUNDS
OXYCARBIDES
SILICON CARBIDES
TUNGSTEN COMPOUNDS
CARBIDES
CARBON COMPOUNDS
CHEMICAL COATING
DEPOSITION
ELEMENTS
MATERIALS
NONMETALS
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
REFRACTORY METAL COMPOUNDS
SILICON COMPOUNDS
SURFACE COATING
TRANSITION ELEMENT COMPOUNDS
360601* - Other Materials- Preparation & Manufacture
360603 - Materials- Properties
360602 - Other Materials- Structure & Phase Studies