Continuous regulation from fully dense to high porosity within polymer-derived SiCN ceramics

Porosity-controllable SiCN ceramics were prepared using a simple partial crosslinking method, which is promising for preparing bulk polymer-derived ceramics with different dimensions. Continuous regulation from fully dense to high porosity within polymer-derived SiCN ceramics was realized via secondary crosslinking of partially crosslinked polysilazane (PSN). A fully dense SiCN ceramic was obtained by shaping the single partially crosslinked PSN (PC-PSN) followed by pyrolysis. PC-PSN was obtained by controlling the crosslinking reaction, and it retained a strong ability to cross link further. SiCN ceramics with different porosities were prepared by mixing PC-PSN and completely crosslinked PSN (CC-PSN) at different proportions. The size and density of the pores can be controlled via the proportion of CC-PSN in a mixed powder. The resultant SiCN ceramic has a porosity that ranges from 0% to 21.32%, which is validated to ensure the component integrity of SiCN ceramics with different dimensions due to the release of residual stress during pyrolysis.