Hydroxyapatite Coatings with Enhanced Proton Conductivity
Abstract
Hydroxyapatite (HA) is a crystalline calcium phosphate with the stoichiometric formula Ca5(PO4)3(OH) that has a disordered hexagonal crystal structure. The hydroxyl (OH) groups in HA form columns lining the crystallographic c-axis. At high temperatures (>200 °C), protons can move along the c-axis by a hopping mechanism through the hydroxyl columns. This talk describes a novel method to produce HA membranes and coatings in which the crystal domains are nearly perfectly aligned with the c-axis oriented normal to the coating surface, and the c-axis length passes through the entire membrane thickness. The unique aligned microstructure of the membrane provides proton conducting pathways through the membrane and eliminates interfaces that act as barriers to proton transport. As a result, proton conductivity is enhanced by orders of magnitude, opening up new potential applications of HA as a fuel cell membrane or electrochemical sensor. In addition, the electrical properties of the aligned membrane structure shows promise for enhancing bioactivity when HA is used as a coating on orthopedic or dental implants in order to enhance bone repair after implant surgery.
About the speaker
Prof. Matthew Yates received his PhD in Chemical Engineering from the University of Texas in 1999. He was postdoctoral fellow at the Los Alamos National Laboratory from 1999 to 2001. He joined the University of Rochester in 2001, and is currently a scientist of the Laboratory for Laser Energetics, and the Chair and Professor of Chemical Engineering.
Prof. Yates’ research interests focus on colloids and interfaces, fuel cell membranes, crystallization, microencapsulation, particle synthesis and colloidal stabilization. His research group creates advanced materials through the control of surface and interfacial properties. They are particularly interested in the production of fine particles, thin films, and membranes. In collaboration with the Laboratory for Laser Energetics, they have created hollow particles for laser fusion targets. Bioconjugation to particle surfaces and microencapsulation of pharmaceuticals has been explored in collaborations with the School of Medicine to create particles for controlled and targeted release. They use particle assembly into thin films to create optically reflective coatings and free standing membranes with enhanced transport properties. Crystal growth onto surfaces has been used to form proton conducting ceramic membranes with enhanced transport properties that can be used in fuel cells and other electrochemical devices.
