X-ray Tomographic Study of Chemical Vapor Infiltration Processing of Ceramic Composites

• Published in: Science (American Association for the Advancement of Science) 1993-05, Vol.260 (5109), p.789-792
• Main Authors: Kinney, J. H., Breunig, T. M., Starr, T. L., Haupt, D., Nichols, M. C., Stock, S. R., Butts, M. D., Saroyan, R. A.
• Format: Article
• Language: English
• Subjects: 360201 - Ceramics, Cermets, & Refractories- Preparation & Fabrication; 360202 - Ceramics, Cermets, & Refractories- Structure & Phase Studies; Applied sciences; Architectural models; Architecture; Building materials. Ceramics. Glasses; CARBIDES; CARBON COMPOUNDS; Ceramic composites; Ceramic industries; CERAMICS; CHEMICAL COATING; Chemical industry and chemicals; CHEMICAL VAPOR DEPOSITION; COMPOSITE MATERIALS; CRYSTAL GROWTH; Density; DEPOSITION; DIAGNOSTIC TECHNIQUES; ELECTROMAGNETIC RADIATION; Exact sciences and technology; Fiber reinforced composites; Fiber-reinforced ceramics; Fibrous composites; IONIZING RADIATIONS; Macropores; Material concentration; MATERIALS; MATERIALS SCIENCE; MATHEMATICAL MODELS; Micropores; MICROSCOPY; MICROSTRUCTURE; POROSITY; PRODUCTION; RADIATIONS; SILICON CARBIDES; SILICON COMPOUNDS; Spatial resolution; Structural ceramics; SURFACE AREA; Surface areas; SURFACE COATING; SURFACE PROPERTIES; Technical ceramics; TOMOGRAPHY; Vapors; X RADIATION
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.260.5109.789

The fabrication of improved ceramic-matrix composites will require a better understanding of processing variables and how they control the development of the composite microstructure. Noninvasive, high-resolution methods of x-ray tomography have been used to measure the growth of silicon carbide in a woven Nicalon-fiber composite during chemical vapor infiltration. The high spatial resolution allows one to measure the densification within individual fiber tows and to follow the closure of macroscopic pores in situ. The experiments provide a direct test of a recently proposed model that describes how the surface area available for matrix deposition changes during infiltration. The measurements indicate that this surface area is independent of the fiber architecture and location within the preform and is dominated by large-scale macroporosity during the final stages of composite consolidation. The measured surface areas are in good agreement with the theoretical model.