Sol–gel derived bioglass as a coating material for porous alumina scaffolds

Bioglasses are important bioactive materials and have been used for the repair and reconstruction of diseased bone tissues, as they exhibit direct bonding with human bone tissues. However, bioglasses have low mechanical properties and thus are usually used as coatings on strong substrates. A sol–gel method was used in this study to produce the 58S bioglass powder with the composition of 58 mol% SiO2–38 mol% CaO–4 mol% P2O5. The bioglass powder was then pressed into discs and sintered at 500, 800, 1000, and 1200 °C, respectively. The apparent density and the Vicker’s hardness of the sintered bioglass were tested using a densometer and a Vicker’s hardness tester. The thermal properties of the bioglass were also studied using differential scanning calorimetry (DSC) and dilatometry. The crystallization of the bioglass was examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The sintered bioglass discs were then immersed in the simulated body fluid (SBF) solution. The bioglass surface after the immersion was examined using field emission scanning electron microscopy (FE-SEM). The formation of apatite layer was confirmed using Fourier transform infrared spectroscopy (FTIR). The apparent density and the hardness of the bioglass reached 3.12 g/cm3 at 1000 °C and 1.05 GPa at 1200 °C, respectively. The formation of hydroxyl-carbonate apatite layer confirmed the bioactivity of the bioglass. It was also found that at sintering temperatures above 800 °C, crystalline phase CaSiO3 was formed. With the formation of CaSiO3, the bioactivity of the bioglass started to decrease.