Gradual mechanochemical reaction to produce carbonate doped fluorapatite–titania composite nanopowder

Carbonated fluorapatite–titania composite nanopowders were successfully synthesized by a facile room-temperature mechanochemical process. Mixtures of calcium carbonate, phosphorous pentoxide and calcium fluoride with different amounts of titania (0, 3, 6, and 9 wt%) were milled using a high-energy planetary ball mill for 10 h. Results showed that a gradual transformation occurred during the mechanical activation. In the absence of titania, nanosized B-type carbonated fluorapatite with crystallite size of 6973 nm was formed. In the presence of 3–9 wt% titania, mechanochemical reaction caused the formation of carbonated fluorapatite–titania composite nanopowders. The crystallite size declined drastically and reached 1271 nm when the titania content was increased to 9 wt%. In contrast, the lattice strain and volume fraction of grain boundary increased notably from 0.004570.0002 to 0.008470.0004 and from 470.21% to 2171.07%, respectively, while the titania content rose from 0 to 9 wt%. From the data obtained, the unit cell volume of carbonated fluorapatite was influenced strongly by the titania content, whereby the sharp increase in unit cell volume from 524.42 to 530.40 A 3 was due to the increase of the titania content from 0 to 9 wt%, respectively. Microscopic observations indicated that the product had a cluster-like structure with an average particle size of about 75 nm. & 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.