Effects of clay and fireclay addition on the properties of magnesia–forsterite–spinel refractories synthesized at different firing temperatures

This study investigates the effects of adding clay and fireclay on the physical and mechanical properties of magnesia-based refractories such as contraction, bending strength, bulk density, and apparent porosity. Domestic raw materials were used for the preparation of samples fired at ۱۳۵۰, ۱۴۵۰, and ۱۵۵۰ °C for ۲ h. Adding clay exhibited no significant effect on the density and porosity, whereas adding fireclay had a remarkable influence on the shrinkage. Nevertheless, the effects of clay and fireclay on the strength of magnesia were unnoticeable. X-ray diffraction results showed that, after firing, the main phase compositions of the samples with clay addition were periclase and forsterite. Adding fireclay led to the synthesis of magnesite spinel, which can be attributed to the high alumina content. Based on scanning electron microscopy, no liquid phase was formed indicating that the sintering was a solid-state evolution with the synthesis of forsterite.

Keywords:

Magnesia , Firing , Clay , Fireclay , Refractories , Synthesis