Phase Evolution in Doped Polymer Derived Silicon Oxycarbide Ceramics

Abstract

Polymer derived ceramics (PDC) is an important class of ceramics that are fabricated from the inert atmosphere pyrolysis of Si- containing precursors. Various Si- based ceramics including silicon oxycarbide (SiCO), silicon carbonitride (SiCN), silicon carbide (SiC), silicon borocarbonitride (SiBCN) etc. can be prepared from various Si- containing precursors. These ceramics are characterized by their high specific strength, oxidation resistance, enhanced creep resistance and other functional properties. One of the most important developments in the ceramic system is the possibility of using these materials as coatings for high temperature structural ceramics. Although oxidation resistance of PDCs are good, they need to be fabricated in the multilayer structures that includes phase stability with various other metal oxides and carbides. The present work focuses on transition metal modified Polymer derived ceramics (PDC). Poly (methyl) silsesquioxane was used as the preceramic polymer in the process. Various transition metal elements having similar atomic size and different valence such as Al and Ti were introduced in the SiCO structure to form modified PDC. The doping amount in the structure is varied to study effect of amount of transition metal doping at the molecular level on phase evolution at different temperatures Phase evolution and thermal behavior of the modified PDCs at different high temperatures are studied.