Bioactive materials such as bioactive glasses, bioactive glass-ceramics
and calcium phosphate bioactive glasses are widely used in medical applications [1]. They have been developed for repairing and reconstructing
diseased and damaged bones and/or tissues. Among these materials, the
most popular is bioactive glass and in particular 45S5 Bioglass® which
was developed by Hench [1] and has a chemical composition of SiO2–
Na2O–CaO–P2O5. When bioactive glass has been implanted in a human
body, biologically active carbonated hydroxyl apatite layers are formed
on its surfaces. Subsequently, integration of the bioactive glass with living
bone then occurred [2,3]. However, major disadvantages of bioactive glass
materials are their low mechanical strength and high cost of fabrication.
Rice husk, one of the by-products of rice milling processes, is rich in
silica, which can be extracted into silica powder. Sintering the rice husk
produces the rice husk ash (RHA) which is relatively cheap to produce
and mainly contains amorphous silica with some other minor metal
impurities [4]. Amorphous silica can also be extracted easily as sodium
silicate which is in soluble silicate forms as a major component in the