Ceramic manufacturing process optimization: behaviour of mineral suspensions

Suspensions of particles are ubiquitous in natural phenomena, such as mud and debris flows, and in industrial processes, including concrete casting, drilling muds, and clay slurries used in ceramic production. During the flow of granular suspension, phase separation of particles can be observed due to shear-migration and shear-sedimentation phenomena. Evaluation of the stability of the suspension is extremely important in the slip casting process for traditional ceramic product. Loss of homogeneity with a non-uniform spatial distribution of particles, promotes crack formation due to differential shrinkage and internal stresses. Internal inhomogeneity also contributes to a delayed thickness formation, surface defects and clogging of the gypsum mould. In this project, the flow behaviour of ceramic clay slurries is studied with rheological measurements, numerical simulations and electrical resistance tomography (ERT). Results show that the clay slurries, although stable at rest, are subject to phase separation during flow. Phase separation could be predicted and studied with a diffusive flux model. Particle resuspension with a static mixer could be used to homogenise the flow during the slip casting process. Despite its relatively low spatial resolution, ERT proved to be a useful tool for visualizing flow structures and identifying phase separation. Segregation within the green body could be related to surface defects, which are linked to the degradation mechanisms of refractory rollers in the firing kiln. A better understanding of these degradation mechanisms provides valuable insights for reducing defects, extending roller lifespan, and optimizing the entire ceramic production.