| Due to some problems such as poisonous reaction systems,low wet green strength,and long coagulation times in the processing of other colloidal formings of ceramics,a novel direct coagulation casting(DCC)method for silicon carbide suspension using dispersant crosslink reaction was developed in this work,A well disperse silicon carbide suspension with solid content of 50 vol% and a viscosity of 0.87 Pa s could be obtained when 0.2 wt% polyethyleneimine as dispersant at pH=5-6.Carboxymethyl cellulose(CMC)were used as coagulant,the effects of coagulant on the viscosity and zeta potential of silicon carbide suspension were systematically studied at different temperatures.It was found that siilicon carbide suspension was coagulated at a high temperature of 70oC because the viscosity of the silicon carbide suspension with 0.2wt% of carboxymethylcellulose was increased to 25 Pa s within 30 min.The coagulation principle can be due to the crosslink reaction between polyethyleneimine and carboxymethyl cellulose at high temperatures,dispersant on the silicon carbide powder particles was not able to disperse well.Destabilization of the suspension led to coagulate because the isoelectric point of the suspension was changed and the zeta potential of suspension was decreased..A three-dimensional network structure in the green body by dispersant crosslink reaction improves the strength of green bodies.The strength of green body with 1.99 MPa is better than that made by traditional direct coagulation casting.The silicon carbide ceramics with relative density above 98.8% and 99.3% were prepared by pressureless sintering and hot pressure sintering,respectively.Flexural strengths of silicon carbide ceramics with 720.34±71.42 MPa and 753.93±67.89 MPa were prepared by pressureless sintering and hot pressure sintering,respectively.High-performance silicon carbide ceramics can be prepared successfully by dispersant crosslink reaction which providing a new idea for advanced ceramic colloidal molding process. |
PDF Full Text Request