Increased chemical stabilities of well-dispersed hydroxyapatite (HAp) powders prepared by calcination of HAp-β-cyclodextrin-methylene blue@carbon

Biocompatible hydroxyapatite (HAp) powders have thermodynamically driven tendencies to lower their surface areas due to the formation of irreversible aggregations. To address this challenge, HAp hybrid powders are herein prepared by a traditional wet-precipitation method with subsequent hydrothermal carbonization for surface modification. The crystallite size, crystallite degree and area ratio of the infrared peak assigned to bonding water versus that of free water are determined to investigate the variation of HAp crystallization with processing parameters. The crystallization of HAp is facilitated by enriched water in a stealth layer with water molecules evolved by citrate, N-contained methylene blue (MB), hydrogen groups-rich β-cyclodextrin (CD) and oxygen-contained organic carbon shells. The low surface areas result in fabrication of nano-sized HAp powders with uniform size distribution, well-dispersed morphologies and smooth surfaces through calcination of HAp-CD-MB@C. The pH values of acidic buffers increase slowly during incubation of HAp-CD-MB@C powders with chemical stability and large grain size after calcination at 550°C for 2 h. The present study will shed light on the preparation of nano-sized inorganic powders with uniform size distribution, well-dispersed morphologies and modulated chemical stabilities for their potential applications as carries of small molecular substances and fillers in composite materials.