Crystallization Behavior of Polycarbosilane Derived SiC Ceramics with Ultra-Fast Joule Thermal Shock

Polymer-derived ceramics (PDCs) technology provides a versatile approach to fabricating ceramics with tailored compositions, microstructures, and properties, wherein pyrolysis methods critically influence the crystallization behavior and microstructure of the derived ceramics. Herein, an ultrafast Joule thermal shock technique was employed for the pyrolysis of a SiC polymeric precursor. This approach enables the accomplishment of ceramization within one second. Compared with conventional tube furnace pyrolysis, Joule thermal shock reduces the free carbon content while increasing the defective carbon content in the resulting ceramics and weakens the limiting effect of free carbon on the growth of ceramic grains, thereby enhancing crystallinity. The crystallite size of the sample treated by Joule thermal shock at 1400 °C reaches 6.6 nm, much larger than the 4.1 nm of the sample pyrolyzed at the same temperature in tube furnace. In addition, the localized hot spot effect during Joule thermal shock leads to a nonuniform grain size distribution in the pyrolysis products, with the presence of a small number of large-sized SiC crystals in the resulting samples. This study reveals the impact of Joule thermal shock technology on the crystallization behavior of SiC ceramics fabricated via PDCs, and further confirms its effectiveness in enhancing the efficiency of PDCs process.