Aqueous gelcasting process for β-Si4Al2O2N6 ceramics

Ganesh, Ibram ; Thiyagarajan, Natarajan ; Jana, Dulal C. ; Mahajan, Yashwant R. ; Sundararajan, Govindan (2008) Aqueous gelcasting process for β-Si4Al2O2N6 ceramics Journal of the American Ceramic Society, 91 (9). pp. 3121-3124. ISSN 0002-7820

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Official URL: http://onlinelibrary.wiley.com/doi/10.1111/j.1551-...

Related URL: http://dx.doi.org/10.1111/j.1551-2916.2008.02588.x

Abstract

Dense β-Si4Al2O2N6 ceramics were obtained from α-Si3N4, α-Al2O3, AlN, and Y2O3 upon sintering (for 4 h at 1675°C) green bodies consolidated by an aqueous gelcasting and a conventional dry-powder processing route. The as-purchased AlN powder was treated with H3PO4 and Al(H2PO4)3 and dispersed in aqueous-organic premix solution along with α-Si3N4, α-Al2O3, and Y2O3 powder with the help of a commercial amino alcohol-based cationic (Dolapix A88) dispersing agent to obtain suspensions with 45-50 vol% solids loading for gelcasting purpose. The gelcat β-Si4Al2O2N6 exhibited superior hardness (1423±6 Hv), fracture toughness (3.95±0.3 MPa·m1/2), and coefficient of thermal expansion (3.798 × 10−6/°C between 30° and 1000°C) in comparison with the ceramic consolidated by conventional dry-powder pressing route, which exhibited only 1317±5 Hv, 3.30±0.2 MPa·m1/2 and 3.532 × 10−6/°C between 30° and 700°C.

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