The reaction kinetics of rice husk based cordierite ceramics

In this study, rice husk ash (RHA) was used as a silica source for cordierite production. Two different groups of samples were prepared in order to achieve the synthesis of cordierite. In the first group (HS-0), kaolinite, alumina and talc were used as raw materials while in the second group (HS-1), active silica, obtained from rice husk, was added in powder composition instead of kaolinite. The rice husks were subjected to the chemical pretreatment with 2 M HCl, 5% solid at 25 °C before calcinations to increase silica contents of husk ash. The mixtures of raw materials were prepared in MgO:Al2O3:SiO2 molar ratio of 2:2:5 and ground in water media. The pressed samples were sintered in air at varying temperatures from 950 °C to 1350 °C and soaked for 1 h. It was found that the higher content of α-cordierite with a lower crystallization temperature could be obtained by using active silica instead of kaolinite in the mixture composition. The activation energy of transition μ → α-cordierite was calculated to be 205 kJ/mol for the active silica doped sample.