Low temperature synthesis, structure and bioactivity of xCaO· (1−x)SiO2 glasses

Glasses of composition expressed by the following general formula xCaO·(1?x)SiO₂ (0.30≤x≤0.50) can be prepared by means of the sol-gel route starting from tetramethylorthosilicate and calcium nitrate tetrahydrate They are all difficult to prepare by means of the traditional technique of quenching the melt, because of the high liquidus temperature,T ₁ t that in the case ofx=0.3 glass isT ₁ =1650°C. The DTA apparatus appears a valuable tool for defining the procedure necessary to obtain the glass through the sol-gel route. The glassx=0.3 is bioactive. The experimental results suggest that the gel structures, such as obtained at room temperature, are very similar; only at high temperature do the reactions of hydrolysis and polycondensation go to completion and the structural units characteristic of each glass are obtained.