Effects of CaO and Fe2O3 on the microstructure and mechanical properties of SiO2-CaO-MgO-Fe2O3 ceramics from steel slag

Abstract

A new SiO2-CaO-MgO-Fe2O3 system ceramics, namely pyroxene ceramics in this paper, was put forward for efficiently utilizing the steel slag. The prepared ceramic with 30 wt% of steel slag has excellent properties with flexural strength of 107 MPa and water absorption rate of 0.045%. Microstructure evolution in the new system ceramics was studied by X-ray diffractometry and scanning electron microscopy. High content CaO in this system contributes to crystallization in low temperature. Diopside (CaMgSi2O6) formed at temperature below 800°C, and was predominant at approximately 1 000°C before densification. The main phases of pyroxene have not changed except the solution of ions of Fe2+/Fe3+, Al3+, Mn2+, Ti4+ and so on. Melting of iron-rich andradite, Fe2O3 and RO (solution of FeO, MgO, MnO etc.) phases at temperature between 1 100°C to 1 180°C promoted liquid sintering and densification process. The crystallization process at temperature between 700°C to 1 100°C is prior to the densification process at temperature between 1 150°C to 1 220°C, and the formed crystals played an important role of framework during the densification process. Sole interlocking pyroxene phases and less glass phase in the final ceramic are contributed to its excellent mechanical performances.