**Part 2**

**Bio-Ceramics** 

176 Sintering of Ceramics – New Emerging Techniques

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1156 to 1162

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**9** 

*Portugal* 

**New Challenges in the** 

Cristina Vasconcelos\*

**Sintering of HA/ZrO2 Composites** 

*University of Azores/Department of Technological Sciences and Development Physics Department of FCT-UNL/ Centre of Physics and Technological Research* 

The search for improved the human living standards and longevity in recent decades has led to a strong development of areas related to life sciences. With increasing life expectancy of the population, the constant appeal for the development of materials to be used clinically in the replacement and regeneration of damaged tissues or organs has also allowed the growth of the multidisciplinary field of biomaterials, which is based on the combination of

Bioceramics, used initially as alternatives to metals in order to increase the biocompatibility of implants, have become a diverse class of biomaterials, presently including three basic types: bioinert high-strength ceramics, bioactive (or surface reactive) and bioresorbable ones. These are the ceramics, which can be used inside the human body without rejection to replace various diseased or damaged parts of the musculoskeletal system. In the last 50 years, several advances in many specialty bioceramics such as alumina, zirconia (ZrO2), calcium phosphates and bioactive glasses have made significant contributions to the development of the present health care industry, improving the quality of human life. Recent developments in bioceramics research are, however, focused on bioactive and bioresorbable ceramics, i.e. hydroxyapatite [HA, Ca10(PO4)6(OH)2] and calcium phosphates as they exhibit superior biological properties over other materials. However, the great challenge is the reproduction of structures, properties and functionalities of parts of the human skeleton that result from thousands of years of evolution. The major constituent of bone is HA so it attracts major interest for employing in prosthetic applications due to the similarity of its chemical composition and crystallography to those of mineralized bone of human tissues. In addition the formation of chemical bond with the host tissue offers HA a greater advantage in clinical applications over most other bone substitutes. However, in spite of chemical similarities, mechanical performance of synthetic HA is very poor compared to bone. In fact, its poor mechanical strength makes it unsuitable for load-bearing. In most applications of biomedical materials the mechanical properties are especially important, as well as the chemical reactivity of their surfaces. To overcome these limitations and to meet the requirements for the self-load bearing, HA has been incorporated with other compounds such as mullite (Clifford et al., 2001), ZrO2 (Y.M. Kong et al., 2005; Sung & D.H.

**1. Introduction** 

 \*

Corresponding Author

life sciences with materials science and engineering.
