Synthesis of calcium sulphate as biomaterial

Abstract

Calcium sulphate (CaSO4), one of biomaterial with high potential for dental and orthopedic applications due to its similarity to the mineral constituents of bone in the human body. Three polymorphic forms of anhydrous CaSO4 exist, namely III-CaSO4, II-CaSO4 and I-CaSO4, which existed in ascending order of temperatures. II-CaSO4 is known as the most stable anhydrite under ordinary atmospheric conditions. In this research, the effects of different calcination temperatures on the purity and properties of II-CaSO4 powder were studied. Powder of anhydrous calcium sulphate (CaSO4) was successfully synthesized via aqueous precipitation method at room temperature. Calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and sodium sulphate anhydrous (Na2SO4) (precursors) was mixed, filtered, dried and calcined to form II-CaSO4. The as-synthesized CaSO4 powder had been characterized via Thermogravimetry-Differential Thermal Analysis (TG-DTA), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM) and Particle Size Analysis (PSA). The as-synthesized CaSO4 powder was then calcined at four different temperature (300 °C, 500 °C, 800 °C and 1200 °C). The calcined CaSO4 powder had been characterized by XRD (phase), FTIR, FESEM (microstructure) and PSA. The XRD result shows that 500 °C was the optimum calcination temperature required for 100 % product gain of anhydrous II-CaSO4 powder. Furthermore, the FTIR result shows that structured water and impurities have been removed after CaSO4 powder were being calcined at 500 °C and higher. Also, the FESEM observation shows that increasing calcination temperatures will contribute to the change of morphology of the CaSO4 powder as well as its particle size due to necking effect. Therefore, the most optimum processing parameters for pure II-CaSO4 powder formation is calcined at 500 °C.