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Alumina Sol‐Assisted Sintering of SiC—Al 2 O 3 Composites
Author(s) -
Yang Quanzu,
Troczynski Tom
Publication year - 2000
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.1151-2916.2000.tb01304.x
Subject(s) - mullite , materials science , sintering , composite material , microstructure , ceramic , composite number , sol gel , phase (matter) , silicon carbide , indentation hardness , grain size , nanotechnology , chemistry , organic chemistry
The composite sol—gel (CSG) technology has been utilized to process SiC—Al 2 O 3 ceramic/ceramic particulate reinforced composites with a high content of SiC (up to 50 vol%). Alumina sol, resulting from hydrolysis of aluminum isopropoxide, has been utilized as a dispersant and sintering additive. Microstructures of the composites (investigated using TEM) show the sol‐originating phase present at grain boundaries, in particular at triple junctions, irrespective of the type of grain (i.e., SiC or Al 2 O 3 ). It is hypothesized that the alumina film originating from the alumina sol reacts with SiO 2 film on the surface of SiC grains to form mullite or alumina‐rich mullite‐glass mixed phase. Effectively, SiC particles interconnect through this phase, facilitating formation of a dense body even at very high SiC content. Comparative sinterability studies were performed on similar SiC—Al 2 O 3 compositions free of alumina sol. It appears that in these systems the large fraction of directly contacting SiC—SiC grains prevents full densification of the composite. The microhardness of SiC—Al 2 O 3 sol—gel composites has been measured as a function of the content of SiC and sintering temperature. The highest microhardness of 22.9 GPa has been obtained for the composition 50 vol% SiC—50 vol% Al 2 O 3 , sintered at 1850°C.