Solid freeform fabrication of functional silicon nitride ceramics using laminated object manufacturing

A novel concept for the fabrication of functional structural ceramic components was investigated using rapid prototyping technology. The technology used was based on the Laminated Object Manufacturing (LOM) process for creating solid prototypes by sequentially laminating and cutting constituent cross-section layers of sheet material. In this study, the LOM process has been adapted to use green tape preforms to prepare ceramic shapes directly from Computer Aided Design (CAD) generated images.;The host material in this study, silicon nitride (Si3N 4), is an important structural ceramic due to its desirable mechanical, thermal and chemical properties. Tape preforms of Si3N4 tailored for the LOM process were fabricated using standard tape casting techniques.;Two material systems were investigated; (a) monolithic Si3 N4, and (b) a preceramic polymer infiltrated Si 3N4.;The physical and mechanical property data obtained for both monolithic and infiltrated LOM Si3N4 ceramics showed that both materials had high densities (monolithic Si3N4, average theoretical density = 97%, infiltrated Si3N4, average theoretical density = 94%) and high Young's moduli (monolithic Si3N 4 = 307 GPa, infiltrated Si3N4 = 301 GPa. Both materials also had high strengths and fracture toughnesses.;Using a preceramic polymer infiltration process reduced the inherent shrinkage that occurs during sintering of conventional ceramics. Volume shrinkage for the infiltrated LOM Si3N4 ceramics was 25% compared to 40% for the monolithic Si3N4 ceramics;The results obtained in this research demonstrated that the LOM technique is a viable method for preparing Si3N4 ceramics with good physical and mechanical properties. (Abstract shortened by UMI.)...