Laser ablation behavior of C_f/SiHfBCN ceramic matrix composites

The behavior of C_f/SiHfBCN composites upon laser ablation was investigated. The evolution of microstructure and phase composition of the composite was studied by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It is found that the ablation mechanism and the microstructure evolution are mainly dependent on the local temperature which directly relies on the distance from the laser spot and the thermal conduction of the carbon fibers. Three regions with different ablation behavior are identified. In the center region, bubble-like structures consisting of HfO₂, and SiHf_xO_y-based layers, cover the ends of the carbon fibers which retain their original shape despite their corrosion. Sheets consisting of HfC_xO_y and SiO₂ as well as porous HfO₂ and liquid SiO₂ are generated in the transition region. The carbon fibers are well protected from oxidation in the two regions. SiO₂ is produced and suppresses the further oxidation of the matrix in the fringe region.