6. Applications of New Colloidal-Forming Processes

The colloidal-forming process based on gelcasting was applied for preparing microbeads of ceramics, improving the breakdown strength of the rutile capacitor, developing the thin-wall rutile tube for ozone generator, and producing the refractory nozzle of zirconia (ZrO₂) and lead zirconate titanate (PZT). The microbeads of ceramics were used as the grinding media, gel-pen ball, and healthcare product with far-infrared function for the human body. Owing to the low-cost associated with the production of the gel beads as well as because of its superior properties, they have been widely used and marketed. When compared with the extrusion formation, the breakdown strength of rutile capacitor prepared by gelcasting was significantly improved. Rutile ceramics with high dielectric constant and high breakdown strength have been used in the thin-wall tube of the ozone generator. The ZrO₂ refractory nozzle prepared by gelcasting has a high melting point above 2680 ℃ and a good thermal shock resistance to withstand the temperature rising from the room temperature to 2200 ℃ in several seconds. Hence, it is considered as a suitable material for making nozzles for precision casting of Cu–Cr molten alloy. When compared with die pressing, gelcasting can provide a more homogenous microstructure as well as more homogenous piezoelectric property of the PZT samples. By using the same sintering procedure, gelcast samples were observed to exhibit slightly stronger piezoelectric effects than the die-pressed ones, and this can be attributed to both density difference and pore size.