Functionally graded ceramics for biomedical application: Concept, manufacturing, and properties

Functionally Graded Materials (FGMs) represent a novel approach for the realization of innovative properties and/or functions that conventional homogeneous materials cannot accomplish. In conventional materials, in fact, the composition or the structure is uniform over the volume; on the opposite, in FGMs such features gradually change from layer to layer, with the aim of realizing a gradation of properties over the volume and performing a set of specified functions. Among FGMs, special attention is given today to Functionally Graded Ceramics (FGCs), designed and developed to withstand a variety of severe operative conditions, including high temperatures, corrosive environments, abrasion, mechanical, and thermal induced stresses. An important application field of FGCs is for medical prosthetic devices and artificial tissues, taking inspiration from the several examples of living tissues with graded structures. After an introduction on the rationale for using FGCs in the biomedical field, the 3 main types of graded materials developed today (eg, composition, porosity and microstructural graded ceramics) are here reviewed, highlighting the most innovative technologies used to develop them, their potentials and challenging features in comparison with the monolithic counterparts.