SURFACE-STRUCTURE AND PROPERTIES OF CALCIUM HYDROXYAPATITE MODIFIED BY HEXAMETHYLDISILAZANE

The surface of synthetic calcium hydroxyapatite Ca-10(PO4)(6)(OH)(2) ( CaHAP) particles was treated by repeated modification with hexamethyld isilazane [(CH3)(3)Si](2)NH (HMDS) in hexane and thermal treatment and the surface of the modified CaHAP was characterized by various means, No remarkable change in XRD patterns or in particle shape by the modi fication was observed. The width of the CaHAP particles gradually incr eased with repeating the modification. FTIR results indicated that HMD S reacted with surface P-OH groups of CaHAP to yield surface Si-(CH3)( 3) groups. The surface of the modified CaHAP was hydrophobic. The surf ace Si-(CH3)(3) groups turned to three kinds of surface Si-OH groups b y treating the modified materials at 500 degrees C in air. These forme d surface Si-OH groups and the remaining surface P-OH groups reacted w ith HMDS by repeating the modification, resulted in the increase of th e surface Si atoms. The modified material having surface Si-(CH3)(3) o r Si-OH groups adsorbed much less CO2 than the unmodified one, (C) 199 8 Academic Press.