Controlled atmosphere pyrolysis of polyureasilazane for tailored volume fraction Si3N4/SiC nanocomposites powders

A controlled atmosphere pyrolysis process is used to develop processing protocols for controlled volume fraction Si3N4/SiC composites from a polyureasilazane. Various processing protocols are explored such as gas composition (Argon, NH3 and a 10%NH3/Argon mix) and a gas switching process where gas is switched from NH3 to Argon at specified temperatures and specified times to quench the reaction. Results showed an accurate control of the volume fraction of SiC in 0–30 volume% range in a Si3N4 matrix. FTIR spectroscopic results confirmed that a substitution reaction occurs between NH3 and the polyureasilazane. Raman spectroscopy shows a free carbon phase present up until 1850 °C and carbon present in specimens that do not show observable XRD peaks of SiC.