Effects Of Sio₂ On The Phase Composition And Biological Activity Of Calcium Phosphate Glass-ceramics

The composition of calcium phosphate glass-ceramics is similar to that of the main inorganic components of human bones and teeth, so it has good biocompatibility and biological activity.however, the crystallization of calcium phosphate glasses is easier, so it is difficult to form a glass. The silica is a good glass formation.In this thesis, a small amount of silica is into calcium phosphate matrix,investigating the effect of silica content on the properties. The powder material and bulk material of calcium phosphate glass-ceramics which is heat treatment process are studied. And mechanical properties and in vitro biological activity are tested.First of all, the precursor powders of calcium phosphate glass-ceramics were prepared by polyacrylamide gel method. The temperure of removing organic matter in dry gel is determined at 60℃0 by thermogravimetry-differential thermal analysis(TG-DTA)curve.Then, X-ray diffraction(XRD), transmission electron microscopy(SEM) were used to study the effects of nucleation temperature, crystallization temperature, crystallization time and the SiO₂ content on the phase composition and morphology of precursor powders. The heat treatment process to the powder was: 700℃nucleation for 2 hours, 900℃crystallization for 6 hours.Secondly, investigating the effect of SiO₂ content on the sintering properties. The results showed that bulk density from the 2.659g/m3 reduced gradually to 2.070 g/m3 with increasing silica content,; porosity increased gradually from 3.79% to 29.22%; Linear shrinkage rate first increased and then decreased, from 8.62% to 14.62%, then to 13.23%.The hardness and fracture toughness of calcium phosphate glass-ceramic were tested. The relationship between quantity of silica and mechanical properties was analysis. Founding to increase with silica content, the porosity was gradually larger and more,leading to hardness and fracture toughness of material gradually reduced. Hardness was from the 5.291GPa to 1.688GPa, fracture toughness was from 6.023 GPa·m1/2 to 1.463 GPa·m1/2.The results showed that the best mechanical properties was GC05, GC10 second.The in vitro biological activity of material was studied in simulated body fluid (SBF). Fourier transform infrared spectroscopy(FT-IR) and XRD were used to analysis of the phase composition of surface materials, SEM was used to character changes of surface morphology, The change of Ca, P, Si ion concentration with SiO₂ content and immersion time in the SBF was tested by inductively coupled plasma emission spectrometer(ICP).The results showed that the new apatite phase was out on the surface of calcium phosphate glass-ceramics. Deposition of crystalline phase grew up from the initial layer of spherical buds to leaf-shaped with the immersion time. On the same conditions that soaking time, concentration of calcium and phosphorus increased gradually with the increasing of silicon content, silicon concentration increased with the increasing silica content. GC10 calcium phosphate glass ceramics with good mechanical properties and biological activity, while its ratio of calcium to phosphate is 1.57 ,which is close to human bones and teeth, so it is suitable for repairing or replacement materias of human bone and teeth.