Characterization and in vitro bioactivity study of a new glass ceramic from mica/apatite glass mixtures

Abstract

Feldspar, kaolin, steatite and quartz sand were the main constituent in preparing sintered machinable bioactive glass-ceramic. Mixture of flourmica and flourapatite glasses in the ratio 100/0, 90/10, 80/20, 70/30. 60/30, 50/50 and 0/100 ratios were prepared respectively. Flourphlogopite (Na,K)Mg3(AlSi3O10)F2 with cordierite were developed in the apatite-free glass sample (100/0) whereas apatite with little mullite were developed in free mica glass (0/100). The microstructure shows nano leaves of flourmica in cabbage like texture in apatite-free or admixed with apatite, however, apatite alone was spread as rounded to sub rounded nano size crystals. The coefficients of thermal expansion CTE was between 53.57 and 67.4×10−7°C−1 for the glasses and between 70 and 81.5×10−7°C−1 (20–300°C) for their corresponding glass-ceramics since it increases by the progressive increase of fluorapatite content. Values of Vickers microhardness, fracture toughness, Young's modulus and flexural strength of mica-apatite glass-ceramic samples are found to be in the range (4.6–6.2GPa), (0.76–1.27)MPa.m1/2, (29.33–189.56MPa) and (22.1–51.6GPa) respectively. Immersion of the glass-ceramic samples in SBF solution enriched sample surface by Ca, P which reflects the increase in the probability of formation of some calcium-phosphate compounds which are necessary for bioactivity and bone-bonding. The present glass-ceramics enjoyed machinability and bioactivity as the medically used machinable bioactive glass-ceramics (Bioviert I).