Laser ablation behavior of Cf/SiHfBCN ceramic matrix composites

The behavior of Cf/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 SiHfxOy-based layers, cover the ends of the carbon fibers which retain their original shape despite their corrosion. Sheets consisting of HfCxOy 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.