Porous media model with multiphase transport and solid mechanics bidirectional coupling for SiO2 soot preform sintering process

SiO 2 soot preform sintering is a critical step in the indirect chemical vapor deposition (CVD) method for synthesizing high-quality silica glass , which involves hydroxyl (OH) decomposition, heat and mass transfer, as well as densification . These phenomena are not fully coupled in the traditional models, which leads to inaccurate numerical predictions . To address this, a porous media model with multiphase transport and solid mechanics bidirectional coupling (MTM) is proposed for the soot preform sintering process in this paper. The model is validated by experimental results. Using this model, the densification behavior of soot preform during sintering process is predicted, and the effects of densification on heat and mass transfer are thoroughly examined. The OH decomposition rate and gas phase transport are intensified in the later sintering stage when densification occurs significantly. Consequently, the OH is concentrated, presenting a ringed-shape distribution. The temperature distribution is also affected, which transforms from a layered shape to a ringed shape, with the maximum temperature decreasing by approximately 20 °C. Furthermore, the effects of the temperature rise curve are explored. It is found that a higher preheating temperature and a longer holding time are preferable for the synthesis of high-quality silica glass .