Topic：Apatite, Hydroxyapatite and Carbonated Hydroxyapatite
Time：2014.5.27 14:30-16:00
Location：907-1445
Speaker：Yang LENG (冷扬)，The Hong Kong University of Science and Technology
Introduction：
Dr. Leng Yang graduated from Chongqing University in China with BS degree of Metallurgical engineering. He obtained MS degree of Metallurgical engineering at Michigan Technological University and PhD degree of Materials Science at The University of Virginia in US. He joined The Hong Kong University of Science and Technology (HKUST) as a faculty member in early 1992. Currently, he is professor in the Department of Mechanical and Aerospace engineering at HKUST. His research interests covered materials processing, mechanical behavior and materials characterization. Since 1996, he has focused on biomaterials research, mainly on bioceramics and surface modifications for implant materials. He has published extensively in international journals. His book, “Materials Characterization –Introduction to microscopic and spectroscopic methods” has been widely used for teaching in US, Europe and Asia. Currently, He is the Fellow, Biomaterials Science and Engineering of International Union of Societies for Biomaterials Science & Engineering.
Abstract:
Hydroxyapatite apatite (HA) is the most important ceramic material for biomedical applications because of its similarity to biominerals in bone and tooth. Ability of HA formation in physiological environments has been considered as a criterion to evaluate bioactivity of materials for dental and orthopedic applications. However, we should ask ourselves how much we know about hydroxyapatite in terms of its crystal structure, phase transformation, and formation in physiological conditions. In fact, another calcium phosphate phase, octacalcium phosphate (OCP) was often mistakenly identified as HA. Formation of biomineral phases may be far complicated than commonly believed. Ability of apatite formation as the bioactivity criterion is also questionable. Another related issue is to identify carbonated hydroxyapatite (CHA), the basic mineral component in human hard tissues and an important bioceramic material. Its atomic arrangements in apatite crystal structure and its experimental characterization are still not lack of debating. The HA structures with possible CO3 substituting OH (Type A) or PO4 (Type B) have been analyzed using the experimental and simulation methods. A comparative study of IR spectroscopy reveals the signature IR bands for each type of CHA and the ab-initio simulations of CHA atomic models confirm the experimental results.