Direct Coagulation Casting of Silicon Carbide Components

• Published in: Journal of the American Ceramic Society 1999-05, Vol.82 (5), p.1129-1136
• Main Authors: Si, Wenjie, Graule, Thomas J., Baader, Felix H., Gauckler, Ludwig J.
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Exact sciences and technology; Structural ceramics; Technical ceramics
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/j.1151-2916.1999.tb01886.x

Direct coagulation casting is a novel near‐net‐shape method for forming ceramic green bodies from homogenous high‐solids‐loaded particle suspensions. It is based on the principle of the in situcoagulation of a powder suspension via a reaction‐rate‐controlled internal‐enzyme(urease)‐catalyzed reaction after casting. Low‐viscosity (62 vol%) of SiC, boron, and carbon powder mixtures with a high surface area (>7‐10 m2/g) have been prepared at pH = 10. Salt ions (up to 1‐2 mol/L) are created by the urease‐catalyzed decomposition of urea, to destabilize the suspensions. The coagulation kinetics and the strength of the wet green bodies have been investigated. The reaction rate is strongly dependent on the temperature (in the range of 5°‐30°C) and the enzyme concentration (for the range of 4‐16 units/g SiC) and is independent of the substrate (urea) concentration for urea concentrations of