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Hydrolysis-induced aqueous gelcasting of β-SiAlON-SiO2 ceramic composites: The effect of AlN additive
I. Ganesh,
Published in
Volume: 93
Issue: 10
Pages: 3180 - 3189
Dense β-SiAlON-SiO2 (SiO2520, 40, 50, 60, and 80 wt%)ceramic composites have been prepared from β-Si4Al 2O2N6 and fused silica by sintering at 15001-1750°C for 3-4 h. For comparison purposes, a powder mixture consisting 60 wt% β-Si4Al2O2N6 and 40 wt% fused silica has been consolidated following a new near-net shape technique based on hydrolysisinduced aqueous gelcasting (GCHAS) and sintered for 3 h at 1750°C. In the GCHAS process, consolidation of suspensions containing 50 vol% solids was achieved by adding a polymerization initiator, a catalyst, and AlN powder equivalent to 1-5 wt%Al2O3. Thin-wall radomes consolidated by GCHAS (using AlN equivalent to 5 wt% Al2O3 in the suspension) have exhibited green strengths 420 MPa. The sintered materials were characterized for various properties including hardness, fracture toughness, mass loss, shrinkage, coefficient of thermal expansion, and dielectric constant. The Si2N2O formed from a powder mixture of 60 wt% β-Si4Al2O2N6 and 40 wt% fused silica at 1750°C for 3 h exhibited a flexural strength of B140 MPa, Young's modulus of 214 GPa, coefficient of thermal expansion of 3.5×10 -6°C-1, hardness of 1390 kg/mm2, fracture toughness of 4.2MPa .m1/2, and a dielectric constant of 5.896 and tan δ of 0.002 at 17 GHz. © 2010 The American Ceramic Society.
About the journal
JournalJournal of the American Ceramic Society