Interfacial studies of chemical vapor infiltrated (CVI) ceramic-matrix composites. Annual report, 1 August 1987-31 July 1988

Technical Report · Sat Oct 01 04:00:00 EDT 1988

OSTI ID:6366942

Brennan, J J

The objective of this program is to investigate the fiber/matrix interfacial chemistry in Chemical Vapor Infiltrated Silicon Carbide matrix composites utilizing Nicalon SiC and Nextel 440 mullite fibers and how this interface influences composite properties such as strength, toughness, and environmental stability. The SiC matrix was deposited using three different reactants; methyldichlorosilane (MDS), methyltrichlorosilane (MTS), and dimethyldichlorosilane (DMDS). It was found that by varying the reactant gas flow rates, the ratio of carrier gas to reactant gas, the type of carrier gas (hydrogen or argon), the flushing gas used in the reactor prior to deposition (hydrogen or argon), or the type of silane reactant gas used, the composition of the deposited SiC could be varied from very silicon rich (75 at %) to carbon rich (60%) to almost pure carbon. Stoichiometric SiC was found to bond very strongly to both Nicalon and Nextel fibers, resulting in a weak and brittle composite. A thin carbon interfacial layer deposited either deliberately by the decomposition of methane or inadvertently by the introduction of argon into the reactor prior to silane flow, resulted in a weakly bonded fiber/matrix interface and strong and tough composites. However, composites with this type of interface were not oxidatively stable. Preliminary results point to the use of a carbon-rich SiC interfacial zone to achieve a relatively weak, crack-deflecting fiber/matrix bond but also exhibiting oxidative stability.

• Research Organization: United Technologies Research Center, East Hartford, CT (USA)
• OSTI ID: 6366942
• Report Number(s): AD-A-202225/9/XAB; R-88-917779-2
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201 -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360601 -- Other Materials-- Preparation & Manufacture
360603* -- Materials-- Properties
ALKANES
ALKYL RADICALS
ARGON
BRITTLENESS
CARBIDES
CARBON
CARBON COMPOUNDS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COMPOSITE MATERIALS
DECOMPOSITION
DEPOSITION
DOCUMENT TYPES
ELEMENTS
FIBERS
FLOW RATE
FLUID FLOW
FLUIDS
GAS FLOW
GASES
HYDRIDES
HYDROCARBONS
HYDROGEN
HYDROGEN COMPOUNDS
INTERFACES
LAYERS
MATERIALS
MATRIX MATERIALS
MECHANICAL PROPERTIES
METHANE
METHYL RADICALS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
OXIDATION
PROGRESS REPORT
RADICALS
RARE GASES
SILANES
SILICON CARBIDES
SILICON COMPOUNDS
STABILITY
SYNTHESIS
VAPORS