Normal sintering of Al-doped ?-SiC

Aluminum-containing intergranular phases in hot-pressed silicon carbide

“…High temperatures, usually above 2000 o C, are required for the solid-phase sintering. Aluminum or Al-containing additives substantially lowered the sintering temperature by as much as 300 o C [1,3,4,[7][8][9][10][11][12][13], due to the formation of Alrich liquid phases that promote densification [7,[14][15][16]. In fact, a combination of Al, B…”

“…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]. In this paper, a statistical transmission electron microscopy (TEM) analysis is reported for the structural changes of at 1900°C, 50 MPa, for 1 hour in argon.…”

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

“…This assumption was confirmed by other groups in the following years. It has been recognized that at 1200-1600 o C, boron and carbon react with SiO 2 surface layers on SiC powders, reducing the grain boundary energy, and in turn increasing grain boundary diffusion [2,46,49,50]. This reaction could also prevent reaction between SiC and the surface SiO 2 at sintering temperature [50,51].…”

“…During the past decades, many efforts were made to improve the fracture toughness of SiC. In situ toughening was one of the promising approaches to improving the toughness of monolithic SiC [1][2][3][4]. A common feature of the in situ toughened SiC is a microstructure containing plate-like, elongated SiC grains with weak grain boundaries serving as preferred crack propagation paths [1,5].…”

“…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].…”