Journal of Sol-Gel Science and Technology 26, 1203–1208, 2003 c  2003 Kluwer Academic Publishers. Manufactured in The Netherlands. Crystallization Processes in Composite Biomaterials B. SAMUNEVA, E. KASHCHIEVA, Y. IVANOVA AND E. KADIYSKA University of Chemical Technology and Metallurgy, Sofia, Bulgaria R. HILL Imperial College of Science, Technology and Medicine, London, UK Abstract. The crystallization processes in composite biomaterials containing fluorapatite (FA) and gel glasses (GG) have been investigated. Using the sol-gel method three gel-glasses have been synthesized: ZnO·SiO 2 , ZnO·Al 2 O 3 ·2SiO 2 and ZnO·CaO·2SiO 2 . The composites have been prepared from GG and FA in different mole ratios and each of them treated at 950 ◦ C, 1050 ◦ C, 1150 ◦ C and 1250 ◦ C. From the XRD analysis of the composites it has been established that fluorapatite is present as a major crystalline phase. The XRD patterns and the IR spectra of the pure GG systems have been studied at 200 ◦ C, 600 ◦ C and 800 ◦ C. The surface of the samples has been analyzed before and after the in vitro experiments using SEM. An amorphous layer has been observed on the surface of each of the treated samples. The element concentration and the solubility of the samples have been analyzed after the in vitro experiments by Atomic Absorption Spectroscopy (AAS). Keywords: sol-gel synthesis, Zn-based gel glasses, fluorapitite composites, bioglass-ceramics Introduction Bioglass-ceramics are special type of composite ma- terials with high bioactive, biocompatible, osteocon- ductive and even osteoproductive properties used for repair and reconstruction of diseased or damaged parts of the muscle-skeletal system. A wide range of materi- als for biomedical applications prepared by the sol-gel technology have been obtained and investigated [1–3]. Composite bioglass-ceramics in the system FA-GG with compositions corresponding to the mullite, anor- thite and gehlenite have been successfully synthesized by the sol-gel method and studied in detail. FA is used instead of apatite, as it is thermally and chemically more stable and the fluoride ions stimulate bone growth and have an antimicrobial action. It is known that the introduction of ZnO stimulates the crystallization pro- cesses in glasses at lower temperatures and leads to the formation of glass-ceramics with fine dispersed crys- tals in the structure [4–6]. Zn-containing biomaterials have been synthesized and investigated [7, 8]. Porous bioactive glass-ceramic materials in the system CaO- Al 2 O 3 -P 2 O 5 -ZnO have been synthesized by the sol-gel method [7]. The purpose of the present work is investigation of the crystallization processes in Zn-containing GG and in GG-FA composites as well as in vitro testing the obtained materials for biocompatibility. Experimental Using the sol-gel method the following three GG sys- tems have been synthesized: ZnO·SiO 2 , ZnO·Al 2 O 3 · 2SiO 2 and ZnO·CaO·2SiO 2 . As precursors have been used TEOS, Zn(NO 3 ) 3 ·6H 2 O, Al(NO 3 ) 3 ·9H 2 O and Ca(NO 3 ) 2 ·4H 2 O. The gels have been dried at 100 ◦ C for 24 hours and treated at 600 ◦ C for 2 hours. Fluo- rapatite has been synthesized from hydroxiapatite and ammonium fluoride by thermal treatment at 650 ◦ C for 2 hours. Composites in the systems FA-ZnO·SiO 2 , FA- ZnO·Al 2 O 3 ·2SiO 2 and FA-ZnO·CaO·2SiO 2 in differ- ent mole ratios of GG (20, 40, 60 and 80 mol%) have been studied.