Crystallization processes in organic systems of eutectic type

Abstract

There is a considerable uncertainty as to the nature of phases which form in the early stages of the precipitation of calcium phosphates, usually referred to as hydroxyapatite (Ca5(P04>30H, HAP) (Montel et al., J. Crystal Growth (1981) 53, 74). In this work the pOSSibility of the direct growth of hydroxyapatite in gel medium has been investigated. Calcium phosphate crystals were grown in silica and tetramethoxysilane (TMS) gels employing double diffusion system with CaC1 2 or Ca(N0 3 )2 and KH 2 PO 4 or K 2 HPO 4 aqueous solutions. For the preparation of silica gel pure silicic acid prepared from sodium metasilicate with strongly acid cation exchanger in H form (Karniewicz, Wiktorowska, Kristall u. Technik (1980) 1. §,. 1227) was used. TMS gel was obtained from 2 -5 % aqueous solution of tetramethoxysilane.