2 - Fabrication processes for bioceramics

Abstract

The term “bioceramics” refers to biocompatible ceramic materials, applicable for biomedical or clinical uses. Clinical applications require various shapes of bioceramics from thin films and nano-sized powders to porous or dense bodies. Bone substitutes use massive porous Hydroxyapatite (HA) and β-Tricalcium Phosphate (β-TCP) and their mixture: defective bones that are not always exposed to high stress can be replaced by porous HA or β-TCP. Commercial porous products of HA with a porosity of 70–80% are already distributed to clinics and hospitals. Highly dense ceramics of Yttria-Stabilized Zirconia (Y-TZP) and alumina are applied to hip joint balls and cups, while thin films of HA are coated on hard metals for artificial teeth and hip joints. To satisfy these demands, an appropriate fabrication method and process must be chosen for each clinical device. For fine fabrication of tough Y-TZP cups and balls, fine-grained ceramics of Y-TZP must be sintered with pure and fine powders under a controlled sintering program. In general, tough and strong ceramics consist of fine-grained microstructure, whose average grain diameter is less than 1 μm. It is important to eliminate impurities from bioceramics; even minor impurities bring harm to a body or provoke critical defect in the mechanical properties of bioceramics during long implantation in vivo. To undertake advantageous sintering, it is essential to control chemical and ceramic powder processing. The preparation of pure, fine powders enables the microstructure of bioceramics to be controlled. This chapter presents an overview of the general principles and methods of conventional fabrications, introduces prevailing techniques with some examples from commercial products, and provides a summary of recent advances in potential methods.