Reaction bonding of open cell SiC-Al2O3 composites

Based on the reaction-bonding aluminum oxide (RBAO) technology, open cell S iC-Al2O3 composites with high strength were fabricated from aqueous slurry by a replication process with polyurethane sponges as the substrates. TGA r eveals that about 18 wt% of the initial Al powder in the start compositions oxidized after 1 h stirring. Mixing procedure has a strong effect on the s lurry rheological behavior and macrostructure of ceramic foams. The slurry prepared by stirring I It has a high viscosity and thixotropic behavior, wh ich makes it uniformly coat the sponge substrate, resulting in the producti on of a ceramic with a uniform macrostructure. But, due to the emission of a lot of gas arising from the dramatic oxidation of the Al powder during mi lling, a large number of air bubbles are introduced in the slurry, and this is detrimental to the macrostructure of the ceramic foam. The phase compos itions of the samples consist of silicon carbide, alumina, cristobalite, an d mullite after sintering at 1350 degreesC with a 1-h hold. Compressive str ength increases as the Al powder content increases, and reaches 2.89 MPa wi th a 12 wt% Al powder for ceramic foams with a relative density of 0.30. (C ) 2001 Elsevier Science Ltd. All rights reserved.