Enhanced plasticity of spontaneous coagulation cast oxide ceramic green bodies

In the preparation of large-sized ceramics, the use of a green body with relatively high plasticity is crucial to minimize the risk of cracking during processing. To achieve this goal, glycerol and polyethylene glycol (PEG) were utilized as plasticizers in the shaping of green bodies of oxide ceramics through spontaneous coagulation casting (SCC). This study investigated the effects of plasticizers and particle sizes ranging from the submicron to nanoscale on the slurry viscosity, drying shrinkage of wet gels, and mechanical properties of green bodies. The plasticity of the green bodies was assessed by measuring the impact toughness and flexural stress‒strain curves. By incorporating an appropriate plasticizer, the peak width of the flexural stress‒strain curve for dried green bodies from particles of different sizes was nearly twice that without plasticizers, and the impact toughness was enhanced by approximately 71%, 34%, and 41% when the particle size decreased from the submicron scale to the nanoscale (0.45 μm, 0.18 μm, and 50 nm, respectively). The drilling test revealed that there was nearly no cracking around the holes in the green bodies with plasticizers. The plasticity mechanism of the green bodies was examined based on ultraviolet–visible (UV–Vis) spectroscopy and scanning electron microscopy (SEM). It was discovered that plasticizers might mitigate the brittleness of green bodies by adjusting the interactions between molecules and modifying the gel network properly.