Effect of Heating Mode on Thermal Stability of Nanocrystalline Hydroxyapatite

This study reports the effect of heating mode on the thermal stability of nanocrystalline hydroxyapatite (HA) by comparing conventional electric resistance heating and microwave heating of HA to 1100°C under the same experimental conditions. It was found that, compared with conventional heating, microwave heating of HA resulted in less hydroxyapatite decomposition and a higher Ca/P molar ratio of the product (1.42 versus 1.37) in association with a smaller lattice contraction of the phase probably caused by the selective thermal effect of microwave radiation. It also produced smaller grains (56.54 nm versus 64.32 nm) along with a higher specific surface area and larger total pore volume, featured by the differences of 36.80% and 79.29%, respectively. Moreover, it led to more homogeneous pore distribution. These physicochemical features are expected to contribute to superior mechanical and biologic properties of the final product.