Synthesis of Silicon Substituted Hydroxyapatite Using Microwave Irradiation

Hydroxyapatite is commonly used as bone implant material due to its similarity to bone chemical composition. However, hydroxyapatite has low reactivity with existing bone (bioactivity). Ionic substitution to hydroxyapatite structure may improve its bioactivity. One of ionic substitutions can be conducted using silicon. The aim of this study is to obtain silicon substituted hydroxyapatite with variation concentration of silicon. The variation concentration are 0, 0.4, 0.8 and 1.2wt% silicon. Silicon substituted hydroxyapatite was prepared by precipitation method assisted microwave irradiation. Calcium source was obtained through calcination of duck eggshell, phosphor source from phosphate acid, and silicon from tetraethyl orthosilicate. Hydroxyapatite and silicon substituted hydroxyapatite were evaluated with XRD and SEM EDAX. XRD characterization showed that hydroxyapatite and silicon substituted hydroxyapatite has lattice parameters close enough to theory. Hydroxyapatite with 0.4% wt silicone substitution has lattice parameter close enough to lattice parameter in bone. Crystallite size in hkl (002) showed that silicon substitution to hydroxyapatite structure reduced crystallite size. SEM characterization showed that particle size of silicon substitution hydroxyapatite was 103 nm whereas hydroxyapatite without silicon was 209 nm. Silicon substitution to hydroxyapatite decreased particle size of hydroxyapatite. EDAX characterization showed that the molarity ratio of Ca/P hydroxyapatite sample was 1.68 and molarity ratio of Ca/(P+Si) silicon substituted hydroxyapatite sample was 1.33.