Direct coagulation casting of silicon carbide ceramics via dispersant reaction

Abstract:

Direct coagulation casting via dispersant reaction is a novel colloidal forming method for ceramics. The well disperse silicon carbide suspension can be coagulated in-situ by DCC via dispersant reaction. Silicon carbide suspension was prepared using surface chemical treatment powder. Ammonium carbonate ((NH₄)₂CO₃) was used to leach the silicon carbide powder. Tetramethyl ammonium hydroxide (TMAH) with content of 0.2 wt% was used as dispersant. 2 vol% glycerol diacetate (GDA) was added as coagulation agent. Tetramethyl ammonium hydroxide reacted with acetic acid which hydrolyzed from glycerol diacetate at elevated temperature, and then desorbed from silicon carbide particles. Zeta potential of suspension decreased due to desorption of dispersant, and the suspension coagulated in-suit from the instability of the silicon carbide particle. The silicon carbide green body with compressive strength of 1.13 MPa was coagulated at 70°C. The silicon carbide ceramic with fracture strength of 697 MPa was pressureless sintered at 1950°C for 2h under 0.1MPa argon atmosphere.

Key words:Silicon carbide; Chemical treatment; Direct coagulation casting; Dispersant reaction