Thermal stability and nanostructure evolution of amorphous SiCN ceramics during laser ablation in an argon atmosphere

The thermal stability and nanostructure evolution of amorphous SiCN ceramics during laser ablation in an argon atmosphere were investigated. Laser irradiation experiments were performed by using a continuous wave CO₂ laser, and a finite element simulation was conducted to quantify the non-uniform temperature field during the laser irradiation. Three regions with different ablation behaviours were identified based on the radial temperature gradient. Cracks extended through these three regions because of the large thermal stress. In the reaction zone, the SiCN ceramic surface was covered by only porous SiC because of the carbothermic reaction. In the transition zone, a weak carbothermic reaction occurred at the surface of the SiCN particles, but the graphitisation of the carbon nanostructure was enhanced dramatically. The heat affected zone showed no change in the microstructure morphology. However, the carbon nanostructure also exhibited higher graphitization.