Green Synthesis of Calcium Magnesium Silicate (CMS-Akermanite) Using Natural Biowastes by Solid-State Sintering Route
Hossein Mohammadi, Boey Zhan Hei, Yanny Marliana Baba Ismail, Khairul Anuar Shariff and Ahmad-Fauzi Mohd Noor
The purpose of this study is to prepare dense bulk calcium magnesium silicate (CMS-akermanite, Ca2MgSi2O7) for biomedical applications, using solid-state reaction of a mixture of biowaste materials i.e. cockleshell (as Ca source), dolomite (Mg source) and rice husk (Si source) with the stoichiometric ratio of Ca:Mg: Si 2:1:2 and subsequent heat treatment at 1150°C and 1250°C. The raw biowaste resource (initially calcined separately) were mixed in the planetary ball mill, then pellets were prepared and sintered. The X-ray diffraction (XRD), as well as Field emission electron microscopy (FESEM), was used to characterize the phase composition and surface morphology/microstructure of the sintered product. The XRD analyses confirmed CMS-akermanite as the main phase of the final product. In addition, FESEM showed a porous microstructure for sintered pellets at 1150°C. However, the reduction in porosity resulting from high shrinkage produced dense final product when the sintering temperature was raised to the temperature of 1250°C (however overfiring occurred at temperature above 1250°C). The optimum sintering temperature was 1250°C, showing densified microstructure with a relative density of 93.50%. The flexural strength and tensile strength were found to be 22.16 MPa and 8.21 MPa, respectively. The use of natural biowastes such as cockleshell and rice husk would be beneficial for biowaste management, while they could be considered as alternative source materials to synthesize valuable biomaterials.