Rheology of concentrated SiC particles in silicon alkoxide sols

• Published in: Ceramics international Vol. 32; no. 2; pp. 133 - 136
• Main Authors: Fu, D.Y., Tseng, Wenjea J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 2006; Elsevier Science
• Subjects: Aggregation; Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Ceramic matrix composite; Cermets, ceramic and refractory composites; Chemical industry and chemicals; Cross-disciplinary physics: materials science; rheology; D. SiC; Exact sciences and technology; Heterogeneous liquids: suspensions, dispersions, emulsions, pastes, slurries, foams, block copolymers, etc; Material form; Materials science; Miscellaneous; Other materials; Physics; Rheology; Sol–gel; Specific materials; Technical ceramics; Aggregation; Ceramic matrix composite; Sol–gel; Rheology; D. SiC; Silicon Organic compounds; Dispersion reinforced material; Particle suspension; Experimental study; Precursor; Oxide ceramics; Composite material; Silicon carbide; Sol gel process; Silicon oxides; Technical ceramics; Organic silicate
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2005.01.017

Silicon carbide (SiC) particles were mixed with silicon alkoxide precursors at the sol level, and their rheological behaviors were examined under various solids concentrations ( ϕ = 0.10–0.22 in volumetric ratios) and shear rates ( γ ˙ = 1 – 1000 s −1). The alkoxide precursors were mixtures of tetraethyl orthosilicate (TEOS, Si(OC 2H 5) 4), ethyl alcohol (C 2H 5OH), H 2O and HCl in a constant [H 2O]/[TEOS] ratio of 11. The powdered mixtures all exhibited a shear-thinning flow behavior over most of the shear-rate range examined. This indicates that the concentrated suspensions were flocculated in character. Relative viscosity of the suspensions increased markedly as ϕ increased, suggesting that the particle interaction becomes more pronounced with the increased ϕ. No evidence was seen found for possible particle–precursor interactions at the sol level that might catalyze gelation of the sols. A theoretical maximum solids concentration ( ϕ m) of the suspensions was determined as ϕ m = 0.26–0.28 over a shear-rate range γ ˙ = 10 – 100 s −1. This reduced ϕ m value partially confirmed the dominance of attractive interparticle van der Waals forces in the particle–precursor mixtures.