Modeling of the green body drying step to obtain large size transparent magnesium-aluminate spinel samples

Laboratory-scaled transparent samples have already been obtained, but upsizing the samples remains a technological challenge. Indeed, every step of the process can lead to defects that hinder optical properties. Among all of the processing steps, drying is one of the most critical, especially for large samples with complicated shapes. It can induce micro-cracks that enlarge during sintering. Optimizing this step has thus become a necessity to obtain valid samples for industrial applications. We developed a finite element method (FEM) simulation model from a simple drying profile performed on laboratory-scaled cylindrical samples. Then, we applied this model to larger industrial-scaled samples, to optimize their drying process. Finally, we obtained crack-free 75 mm diameter sintered samples, which become highly transparent after the appropriate hot isostatic pressing thermal treatment.