A review of the evolution of the nanostructure of SiCN and SiOC polymer derived ceramics and the impact on mechanical properties

Polymer-derived ceramics (PDCs) are fabricated through the controlled pyrolysis of silicon-based polymeric precursors. Their structure, and subsequent material responses, are highly dependent on the chemistry of the pre-ceramic polymer, the pyrolysis atmosphere, and the pyrolysis or annealing temperatures. Future development of PDCs and their integration into society will rely heavily on understanding the connection between these variables and their subsequent material performance. In this review, the nanostructural development of silicon carbonitride (SiCN) and silicon oxycarbide (SiOC) ceramics, along with a selection of their chemically or physically modified structures, is presented. The chemistry and processing parameters of these PDCs will be explored in relation to their amorphous and crystalline characteristics, including phase transitions and transition temperatures. The microstructure of these systems is also presented in conjunction with the nanostructure where necessary. The structural properties of SiCN and SiOC PDCs are related to the mechanical responses of these systems, which provides an overview of the design parameters needed to realize a PDC from theory to application.