PROCESSING BEHAVIOR OF HYDROXYAPATITE POWDERS WITH CONTRASTING MORPHOLOGY

Three synthetic hydroxyapatite powders (designated A, B and C), supplied by British Charcoals and MacDonalds and Merck GmbH were chemically and physically characterized with X-ray diffraction (XRD), infrared spectroscopy (IRS), gravimetric analysis (GA), inductively coupled plasma spectroscopy (ICPS), surface area analysis (BET), particle size analysis and scanning electron microscopy (SEM). The powders were pressed at 80 MPa and fired at a range of sintering temperatures between 1190-degrees-C and 1300-degrees-C for 12 h. The sintering characteristics of the four powders were assessed by density measurement, hardness testing and scanning electron microscopy. Infrared spectroscopy and X-ray diffraction results indicated that the powders showed no evidence of decomposition into tricalcium phosphate after sintering at any of the temperatures tested. However, the marked differences in morphology between the three powders led to contrasting sintering characteristics. While two of the powders sintered to near full density, the other showed very little change in density over that of the green compact even after sintering at 1300-degrees-C. Measurement of the hardness versus sintering temperature indicated that the mechanical properties of only the two samples which sintered to full density would make them suitable for any load-bearing applications.