The microstructure evolution of nanohydroxapatite powder sintered for bone tissue engineering

Nanotechnology has been widely used to overcome the brittleness of coarse ceramics. Laser sintering is an effective approach for the preparation of nanoceramics due to the laser properties such as high energy density and rapid heating. In this study, the nanohydroxypatite (HAP) was used to prepare for artificial bone scaffold using a home-made selective laser sintering (SLS) system. The microstructure and the properties of the sintered nanoHAP are tested with scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. We found that the shape of nanoHAP particle changes from long needle-like to spherical or ellipsoidal after sintering, and the HAP particles grow up until they merge together with the increasing temperature. The tendency of preferred orientation reduces and the degree of crystallinity increases with the growth of nanoHAP. HAP dehydroxylation occurs during sintering. HAP decomposes to tetracalcium phosphate and β-calcium phosphate when the sintering temperature is over 1354°C (the laser power is 8.75 W). Sintered nanoHAP maintains a high degree of crystalline and nanometre scale when the laser power is 7.50 W, spot radius 2 mm, sintering time 4 s and thickness of the layer is 0.2 mm. This study presented the optimised technology parameters for the preparation of nanoceramics with a novel SLS system and demonstrated that the nanoceramics with nanosize scale can be obtained by this system.