Study on the evolutionary behavior of three-dimensional morphology of SiO₂/Al₂O₃ hybrid fiber sintered body considering surface diffusion

Ceramic fiber porous materials, which are widely utilized in thermal protection applications, are produced through the sintering of fibers. To investigate the surface diffusion occurring during the solid-state sintering of SiO₂/Al₂O₃ fibers, a simulation model considering the kinetic equations of surface morphology has been developed, which can be used to simulate the three-dimensional surface morphology evolution process of the sintered body of SiO₂/Al₂O₃ hybrid fibers and the validity of the model has been validated through comparisons with actual experimental results. The results of the simulation show that both the maximum sintering temperature and the holding time during the sintering process have a significant effect on the fiber sintering morphology. In contrast, the heating rate appears to exert a negligible effect on this phenomenon. The surface morphology of hybrid fibers after sintering displays distinct geometric features; therefore, a method has been proposed to quantitatively assess the degree of sintering of hybrid fibers. It can be assumed that when the fiber feature axis length ratio (FALR) exceeds 0.5, the hybrid fibers reach a fully sintered state and are ideally bonded. Based on FALR, the sintering degree and morphological characteristics between SiO₂/Al₂O₃ hybrid fibers can be evaluated.