Sol–gel derived calcium silicate ceramics

The calcium silicate systems were prepared by sol–gel methods—varying the synthesis conditions (precursor solutions, chemical compositions, catalysts, temperature and time of aging and heat treatment). The precursors of sol–gel procedures were calcium nitrate and tetraetoxysilane. Acetic acid, water, ammonia and nitric acid were applied as catalysts. The atomic and supramolecular structures of calcium silicate products have been varied from amorphous to crystalline phases depending strongly on the preparation conditions. The structures were investigated in atomic range with Fourier transform infrared (FTIR), X-ray diffraction (XRD) and in supramolecular ranges with small angle X-ray scattering (SAXS), ultra small angel X-ray scattering (USAXS) measurements. The mechanical properties could be most efficiently improved by heat treatments (min. 600 °C) and a post-treatment with tetraetoxysilane (TEOS). The mechanical strength of bulk biomaterials has been controlled by Brinell hardness test.