Synthesis of sustainable binary calcium monosilicate ceramics from bio-waste: effect of sintering temperature on microstructure and electrical properties
View/ Open
Date
2023-01Author
N. H., Jakfar
B., Johar
N. M., S. Adzali
S. N. H., Mohd. Yunus
Cheng, E. M.
E. Z., M. Tarmizi
Khor, S. F.
Z., A. Talib
Metadata
Show full item recordAbstract
This study was conducted to synthesise calcium monosilicate ceramics using rice husks and
raw eggshells and investigated the effect of sintering temperature on the physical,
microstructure and electrical properties of the final product. The high content of calcium
and silicon in eggshells and rice husks, respectively promote the use of waste materials in
the production of calcium monosilicates by mixing in a molar ratio 1CaO:1SiO2 and fired at
different sintering temperatures for 2 hours with a heating rate of 10°C/min. A good
correlation between sintering temperature, structural, microstructure, and electrical
properties of calcium silicate was observed. The structural and morphological evolutions
were characterised by X-ray diffraction (XRD) and scanning electron microscopy (SEM)
equipped with electron dispersive X-ray analysis (EDX). XRD analysis showed that the main
crystalline phases of synthesised calcium monosilicate are pseudowollastonite (ICSD 98-
005-2598) at 1250°C, and the phases of SiO2 also exist in different types of minerals. Besides,
a small amount of larnite, Ca2SiO4 was traced at 1100°C and 1200°C. Fourier Transforms
Infrared (FTIR) spectra showed the presence of characteristic functional groups in the
precursor powder. In Nyquist plots, the summit frequency of the dominant arc decreases
with increasing sintering temperatures. It may be attributed to the co-effect of the grain size
and pore. A larger value of impedance at a lower frequency suggests an essential role of
boundaries in governing the electrical properties of the sintered ceramics. As the sintering
temperature increases, the microstructure of the sintered samples becomes denser while
conductivity performance decreases. This is due to the reduction of particle interfaces and
charge transfer.