Control of diatomaceous earth insulating brick shrinkage when firing by addition of calcium sources

抄録

To stabilize the quality of insulating bricks made from Noto-diatomaceous earth (Noto-DE), control of the shrinkage during firing by the addition of calcium sources to the raw material was investigated. The shrinkage mechanism was elucidated from investigation of the phase change at 1000 °C and comparison of the component distributions of materials between Noto-DE and other diatomaceous earths (DEs) with different characteristics. In every DE, the effect of firing shrinkage control by the addition of calcium sources and the increase of wollastonite phase in the base materials with an increase of the firing times were confirmed. In addition, it can be concluded that the silica source of wollastonite is derived from amorphized clay minerals, due to the absence of Ca in amorphous diatom shells. It is suggested that the control of the firing shrinkage of insulating bricks made from DE with additional calcium sources is due to the crystallization of wollastonite originating from the silica source of amorphized clay minerals.