Effects of Milling Speed and Sintering on the Formation of Akermanite (Ca₂MgSi₂O₇) Bioceramics

The aim of the present work is to study the effect of different milling speeds on the preparation of akermanite ceramics. In this study, akermanite (Ca₂MgSi₂O₇) was synthesized by high speed planetary ball milling and mixing method. Calcium oxide (CaO), magnesium oxide (MgO) and silicon dioxide (SiO₂) were used as initial reactants. The starting materials were milled with molar ratio of 2:1:2, respectively, using ball-to-powder ratio 10:1 at different milling speeds of 300 rpm, 400 rpm and 500 rpm. After synthesis, the powders were pelletized to form pellets (13 mm) with 150 MPa by uniaxial pressing. The pellets were then sintered at 1250°C for 3h. Phase analysis by X-ray diffraction (XRD), surface morphology by Field Emission Scanning Electron Microscopy (FESEM), Brunauer-Emmet-Teller (BET) specific surface area analysis, linear shrinkage, porosity and density measurement were performed on the milled and sintered samples. It was found that milling at 500 rpm resulted in powder with largest surface area (108 m²/g), indicating the finest size of powder. FESEM observations showed that the sintered-akermanite ceramics from 500 rpm milling at 1250°C were the densest with microcrystalline appearance and clear grain boundaries, while milling at 300 rpm and 400 rpm showed some pores in the sintered samples.