Microanalytical investigation of sintered SiC

Microstructure development in hot-pressed silicon carbide: effects of aluminum, boron, and carbon additives

“…6 shows high-resolution micrographs obtained from 4ABC-, 5ABC-, and 7ABC-SiC, respectively. Similar to 3ABC-SiC [25], and to other SiC samples studied by other groups [5,22,23], amorphous IGFs were observed in 4ABC-SiC. However, in contrast to the finding that more than 85% of the examined IGFs were amorphous in 3ABC-SiC, the fraction of the amorphous IGFs in 4ABC-SiC was only about 40%, while the remaining 60% of the IGFs were crystalline.…”

“…Additions of aluminum metal or aluminum compounds as sintering additives have been known to facilitate liquid phase sintering of SiC [1,3,[11][12][13], lower the densification temperature [1,2,4,11,[14][15][16][17][18][19][20], induce the phase transformations among SiC polytypes, promote anisotropic growth of SiC grains [13,15,21], form amorphous grain boundary films, and produce various secondary phases in triple junction pockets [1,5,18,[22][23][24][25][26]. Cao et al hot-pressed SiC in the presence of aluminum, boron, and carbon, (ABC-SiC), demonstrating excellent flexural strength, high fracture toughness, fatigue resistance, improved creep resistance, and enhanced wear resistance at ambient and elevated temperatures [18,[27][28][29][30][31].…”

Aluminum-containing intergranular phases in hot-pressed silicon carbide

“…Al-based oxycarbide grain boundary film between SiC grains were observed [2,7,[17][18][19][20][21][22], as well as other secondary phases at triple junctions [21][22][23]. The best of these SiC materials yet investigated exhibited unprecedented combinations of strength, fracture toughness, fatigue, high temperature creep resistance, and wear resistance [9,14,17,18,[24][25][26][27][28][29][30][31], resulting from the presence of favorable grain boundary structures [22].…”

Thermal Modification of Microstructures and Grain Boundaries in Silicon Carbide

“…4 In the latter, liquid phases were formed at processing temperatures, leading to the formation of residual intergranular films (IGFs). 4,[6][7][8][9][10][11] The nature of these amorphous intergranular films was shown to consist mainly of Al-O-Si-C 11 or Al-O-C, 12,13 and to provide a path for intergranular crack propagation. Elastic bridging and pullout of the interlocked SiC grains 4,5,14 contributed to the toughening, 2,[15][16][17] leading to fracture toughness of as high as 9…”