The fate and role of in situ formed carbon in polymer-derived ceramics

Polymer-derived ceramics (PDCs) have been intensively studied for nearly 50 years due to their unique advantages to producing ceramic fibers, coatings, foams, nanocomposites and for additive manufacturing. A phenomenon associated with the polymer-to-ceramic transformation process using organo-substituted silicon polymers as the starting material has been widely reported, namely, in situ formation of carbon within the generated silicon-based ceramic matrix. Interestingly, the precipitation of carbon depends to a great extent on the molecular structure of the preceramic polymer and significantly affects the composition, crystallization and decomposition behavior, microstructural evolution as well as the related structural and functional properties of PDCs. Thus, this review article highlights the recent progress in the PDC field with the focus on the fate and role of the in situ formed carbon. Firstly, a brief summary of the synthesis and processing of PDCs is provided, followed by the microstructural characterization of the formed ceramics. The in situ formation of carbon, precursor-carbon-morphology relation and high-temperature evolution of the carbon will be summarized. Secondly, the influence of the segregated carbon on the microstructure and its associated properties of the PDCs will be comprehensively highlighted. Finally, potential advanced structural and functional applications of the PDCs related to the carbon are evaluated.