Microstructure and mechanical properties of MgOC refractories containing graphite oxide nanosheets (GONs)

MgOC refractories containing graphite oxide nanosheets (GONs) and Al, Si additives were prepared in this work. Firstly the MgOGONs composite powders were fabricated by common ball milling of expanded graphite and magnesia powders, and then incorporated into MgOC refractories. The phase composition, microstructure, mechanical and thermo-mechanical properties of MgOC refractories treated at the different temperatures were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), three-point bending method and thermal shock test. The results showed that the GONs of different sizes and thicknesses were well distributed in magnesia powders. Addition of GONs had a positive influence on the mechanical properties of MgOC refractories. After firing at 1400 °C, much higher cold modulus of rupture (CMOR) and increased displacement were achieved for MgOC specimens with GONs added compared to that of the specimen contained only flaky graphite. Moreover, the thermal shock resistance of all the specimens containing GONs was better than that for the specimen containing no GONs. It was suggested that GONs and in-situ formed ceramic phases in the matrix strengthened and toughened MgOC refractories.