Drying Process of Particle Suspension by OCT Operando Observation

Abstract

The particle aggregate structure formed during drying is desired strongly to control elaborately and flexibly in products and manufacturing processes using particle suspensions, because it is critical to the final performances. However, a direct understanding of the phenomenon under the actual environment is difficult due to the complexity of various factors that affect each other. To solve this issue, an operando observation system that can simultaneously measure the drying characteristics curves, which is the standard-scale of materials, and observe the internal structural changes was constructed in this study. The system consists of a swept-source optical coherence tomography (SS-OCT) for observation, an electronic balance for measuring weight change, and a probe for measuring environmental temperature and humidity change. The drying behavior of coffee droplets and Al₂O₃ slurry was observed using this system, and it was found that the internal structural changes during drying could be directly correlated with the drying characteristics and evaluated quantitatively. Furthermore, the influences of solid concentration and particle dispersion/agglomeration in Al₂O₃ slurry on the internal structure change and drying characteristics were also clarified.