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Silsesquioxanes as precursors to ceramic compositesSilsesquioxanes having the general structure RSiO sub 1.5, where R = methyl, propyl, or phenyl, melt flow at 70 to 100 C. Above 100 C, free -OH groups condense. At 225 C further crosslinking occurs, and the materials form thermosets. Pyrolysis, with accompanying loss of volatiles, takes place at nominally 525 C. At higher temperatures, the R group serves as an internal carbon soruce for carbo-thermal reduction to SiC accompanied by the evolution of CO. By blending silsesquioxanes with varying R groups, both the melt rheology and composition of the fired ceramic can be controlled. Fibers can be spun from the melt which are stable in argon in 1400 C. The silsesquioxanes also were used as matrix precursors for Nicalon and alpha-SiC platelet reinforced composites.
Document ID
19870015999
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Hurwitz, Frances I. (NASA Lewis Research Center Cleveland, OH, United States)
Hyatt, Lizbeth H. (NASA Lewis Research Center Cleveland, OH, United States)
Gorecki, Joy (NASA Lewis Research Center Cleveland, OH, United States)
Damore, Lisa (NASA Lewis Research Center Cleveland, OH, United States)
Date Acquired
September 5, 2013
Publication Date
January 1, 1987
Subject Category
Composite Materials
Report/Patent Number
E-3581
NASA-TM-89893
NAS 1.15:89893
Accession Number
87N25432
Funding Number(s)
PROJECT: RTOP 506-43-11
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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