Preparation of Dense Mullite Ceramics through Gelcasting of Alumina Slurry Dispersed in Silica Sol

• Published in: Advanced engineering materials Vol. 7; no. 8; pp. 746 - 750
• Main Authors: Kong, Deyu, Ying, Si'ai, Yang, Hui, Li, Hui, Wei, Su, Wang, Jiabang
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.08.2005; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deformation and plasticity (including yield, ductility, and superplasticity); Exact sciences and technology; gelcasting; Materials science; Materials synthesis; materials processing; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Mullite ceramics; Physics; sol gel technique; Viscosity; Casting; Scanning electron microscopy; Particle size; Inorganic compounds; Transmission electron microscopy; Gels; Flexural strength; Alumina; Silica; Bending test
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.200400142

A nano‐SiO2‐coated‐Al2O3 (NSCA) micro‐composite system has been derived from silica sol and alumina to prepare dense mullite ceramics by gelcasting technology. Concentrated NSCA suspension with high solid loading but low viscosity was successfully prepared, utilizing the stabilization mechanism of silica nanoparticle halos around alumina particles at pH 9.5. The defect‐free dried green body with bending strength of 5.85 MPa was obtained with only 7.7 wt.% of monomer and dense mullite ceramics was sintered at 1550°C for 2 h, through initial densification by transient viscous sintering, followed by a densification arrest and then a further densification by solid‐state diffusion at higher temperatures.