Mechanical properties of a fully dense polymer derived ceramic made by a novel pressure casting process

A new process has been developed for obtaining fully dense samples of silicon carbonitride (SiCN) from polymers. The process consists of two simple steps: cross-linking the liquid organic precursor under pressure, followed by controlled pyrolysis. Net shape processing is possible by casting the liquid into a mold before polymerization. The entire process is completed below 1000 degreesC. Basic mechanical properties of pore free SiCN made by this process were measured. The Youngs modulus is 155+/-10 GPa. The Vickers hardness increases from 15 GPa at an applied load of I N to 26 GPa at 3 N. Thus, the hardness to modulus ratio of these materials is two to three times higher than for crystalline silicon nitride or silicon carbide. The fracture strength of up to 1.1 GPa was measured. Pressure cast samples have a typical thickness of 0.3-0.5 mm, and are therefore suitable for obtaining a full range of fundamental properties of polymer derived ceramics. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.