Transport properties of ceramic composites
- Georgia Inst. of Technology, Atlanta, GA (United States)
This project involves experimental and modeling investigation of the transport properties of chemical vapor infiltration (CVI) preforms and densified composites, with particular emphasis on gas permeability and mass diffusivity. The results of this work will be useful both for on-going CVI process development and for evaluation and optimization of composite materials for fossil energy applications. With preforms made with 500 filaments/tow Nicalon at 40 vol% fiber loading, permeability values are similar for square-weave cloth layup and 3-D weave at low density. At greater densification the 3-D weave permeability is lower and approaches zero with significantly more closed porosity than the cloth layup. For filament wound preforms we were unable to make reliable measurements with the available materials. A model for gas transport in these materials utilizes percolation theory concepts. The ultimate achievable density is related to the closing of a continuous gas path through the preform. As the density approaches this limit the gas permeability and diffusivity vanish exponentially. The value of this limit is controlled primarily by the preform fiber architecture. The observed difference between the cloth layup and 3-D weave materials is due to the larger pores at tow crossing points found in the 3-D weave.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- OSTI ID:
- 416488
- Report Number(s):
- ORNL/FMP-95/1; CONF-9505204-; ON: DE96001412; TRN: 96:006558-0013
- Resource Relation:
- Conference: 9. annual conference on fossil energy materials, Oak Ridge, TN (United States), 16-18 May 1995; Other Information: PBD: Aug 1995; Related Information: Is Part Of Proceedings of the ninth annual conference on fossil energy materials; Cole, N.C.; Judkins, R.R. [comps.]; PB: 522 p.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Measurement of gas transport properties for chemical vapor infiltration
Structure and properties of braided sleeve preforms for chemical vapor infiltration