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Fabrication of Si 3 N 4 /SiC Composite by Reaction‐Bonding and Gas‐Pressure Sintering
Author(s) -
Lee Soo Young
Publication year - 1998
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1998.tb02477.x
Subject(s) - sintering , microstructure , materials science , flexural strength , composite number , fabrication , composite material , reaction mechanism , catalysis , chemistry , medicine , biochemistry , alternative medicine , pathology
Si 3 N 4 /SiC composite materials have been fabricated by reaction‐sintering and postsintering steps. The green body containing Si metal and SiC particles was reaction‐sintered at 1370°C in a flowing N 2 /H 2 gas mixture. The initial reaction product was dominated by alpha‐Si 3 N 4 . However, as the reaction processed there was a gradual increase in the proportion of β‐Si 3 N 4 . The reaction‐bonded composite consisting of alpha‐Si 3 N 4 , β‐Si 3 N 4 , and SiC was heat‐treated again at 2000°C for 150 min under 7‐MPa N 2 gas pressure. The addition of SiC enhanced the reaction‐sintering process and resulted in a fine microstructure, which in turn improved fracture strength to as high as 1220 MPa. The high value in flexural strength is attributed to the formation of uniformly elongated β‐Si 3 N 4 grains as well as small size of the grains (length = 2 μm, thickness = 0.5 μm). The reaction mechanism of the reaction sintering and the mechanical properties of the composite are discussed in terms of the development of microstructures.