SYNTHESIS OF HYDROXYAPATITE-BASED POWDERS BY MECHANOCHEMICAL METHOD AND THEIR SINTERING

Ceramic hydroxyapatite (HA) is on the way to one of the most promising and diversified materials for employment in surgery, thanks to its go od characteristics of biocompatibility and bioadaptability. The main a nd probably unique deficiency of these materials obtained by tradition al methods consists in its weak mechanical resistance, that does not a llow their use when even low loading is involved To improve the mechan ical properties of HA-based ceramic bodies additions are normally nece ssary. In this paper the authors propose a method to prepare powders a nd composite ceramic bodies with a matrix comprising HA. The powders a re produced by the utilization of a simple and economic mechano-chemic al method. The composite ceramic bodies are easily obtained by simple firing of the powders at a suitable temperature (1250 degrees C). The powders, after sintering, give products that show a flexural strength of more than 100 MPa in standard samples. This value is significantly higher than that usually attainable with present commercially availabl e powders (60 MPa). The transformation in the components (HA and beta- tricalcium phosphate) of the composite ceramic arises from the nature of the powders, consisting of highly defective HA. The mechano-chemica l process is described together with the employed procedures specifica lly followed for reactive milling of starting powders. The preparation conditions of defective HA powders and properties acquired through su ch a method are reported. By this method an intimate mixing of beta-tr icalcium phosphate (beta-TCP) inside the HA matrix is obtained that ea sily allows the preparation of ceramic bodies with reproducible proper ties, with no necessity for additions and mixing procedures, that coul d lead to inhomogeneity.