Thermal decomposition of carbon-rich polymer-derived silicon carbonitrides leading to ceramics with high specific surface area and tunable micro- and mesoporosity

Herein we report on the thermal decomposition of SiCN polymer-derived ceramics leading to materials with high specific surface area and defined pore sizes. The ceramics were obtained by means of pyrolysis of a carbon-rich poly(diphenylsilylcarbodiimide) precursor and by varying the thermolysis parameters, namely temperature, annealing time and using additional annealing steps. The thermal decomposition of SiCN ceramics is correlated with the carbothermal reaction of amorphous silicon nitride phase with excess carbon and this detrimental event leads to high specific surface area up to 568 m² g⁻¹ and micro- and mesopores formation in these materials. High-resolution TEM investigations have confirmed that the pores are embedded only in the carbon phase. Moreover, the relationship between the pore sizes and the organization of free carbon phase is discussed.