7. New Methods and Techniques Based on Gelation

The reliability and cost of the products, which are closely related to the preparation process, are the two major concerns in the industrial production of high-performance ceramics. The preparing, forming, and sintering processes of the ceramic powders are thus becoming increasing important in the recent decades in the ceramic research field. As a precondition of the materials design and realization of the high-performance ceramic products of the desired shapes, the ceramic-forming process usually plays a crucial role in determining the reliability and cost of the products. The traditional methods of producing ceramic products have been widely used in the field of fine ceramics, but they do not meet the requirements of high-performance ceramics. Therefore, numerous research efforts have been directed to devise new methods for the ceramic-forming process. In this chapter, some new methods and techniques based on gelation are introduced, such as solid freeform fabrication (SFF) of alumina ceramic parts; freeform fabrication of aqueous alumina–acrylamide gelcasting suspensions; ceramics with special porous structures fabricated by freeze-gelcasting; solidifying concentrated Si₃N₄ suspensions for gelcasting by ultrasonic effects; laser machining technique of alumina green ceramic; etc. Furthermore, the forming mechanism is analyzed and the characteristics of the green and sintered bodies of the ceramic parts using the new forming methods or new techniques are introduced.