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SiC‐Whisker‐Reinforced Al 2 O 3 Composites by Free Sintering of Coated Powders
Author(s) -
Hu ChingLi,
Rahaman Mohamed N.
Publication year - 1993
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.1151-2916.1993.tb03980.x
Subject(s) - whiskers , whisker , materials science , sintering , composite material , composite number , hot isostatic pressing , calcination , relative density , monocrystalline whisker , coating , biochemistry , chemistry , catalysis
SiC whiskers were coated with a thick cladding of finegrained Al 2 O 3 powder by controlled heterogeneous precipitation in a concentrated suspension of whiskers. After calcination, the coated whiskers were compacted by cold isostatic pressing and sintered at a constant heating rate of 5°C/min in a helium atmosphere. The parameters which control the coating process and the sintering characteristics of the consolidated powders are reported. Starting with an initial matrix density of 40–45% of the theoretical, composites containing up to ≅20 vol% whiskers (aspect ratio ≅15) were sintered freely to nearly theoretical density below 1800°C. By comparison, a similar composite formed by mechanical mixing of the whiskers and the precipitated Al 2 O 3 powder reached a density of only 68% of the theoretical after sintering under identical conditions. For a fixed whisker content, the sinterability of the composites formed from the coated whiskers shows a fairly strong dependence on the whisker aspect ratio.