3 - Ceramics

Abstract

Ceramics are solid materials composed of inorganic, non-metallic substances. Ceramics exist as both crystalline and non-crystalline (amorphous) compounds. Ceramics used for implants and in the repair and reconstruction of diseased or damaged body parts are called “bioceramics”. Depending on the type of response in the body, bioceramics can be broadly classified as bioinert, bioactive, and resorbable. The three factors that influence the choice of ceramics and glasses as biomaterials are: (i) physical and mechanical properties, (ii) degradation of the material in the body, and (iii) biocompatibility. The microstructure of the ceramic material, its properties and the processing routes used are all very strongly interrelated. This chapter describes the general principles that explain some of the mechanisms behind these factors. These can be applied to a wide variety of ceramics and glasses, but there will be a specific emphasis on ceramics with properties and processes relevant to biomedical applications. The chapter describes some of their distinguishing properties due to the nature of the atomic bonds and, in the case of polycrystalline ceramics, their crystalline structure. It discusses the concept of a microstructure within a ceramic material, focusing on grain size, porosity, and flaws existing in all the ceramics used in practical applications. It also describes the definition and measurement of several mechanical properties, including elastic modulus, fracture strength, fracture toughness, subcritical crack growth, hardness, and wear, emphasizing on the brittle and flaw-sensitive nature of the ceramic fracture mode. The chapter discusses processing methods for ceramics, the influence of processing conditions on the microstructure, and the properties of ceramic materials and also highlights general clinical requirements and examples of ceramics used in biomedical applications.