Strengthening mechanism of graphene oxide nanosheets for Al2O3–C refractories

Al2O3–C refractories containing graphene oxide nanosheets (GONs) and additives of Al, Si and SiO2 were prepared. The GONs/α-Al2O3 composite powders were prepared by ball milling expanded graphite (EG) with micron sized α-Al2O3, and then used to make the Al2O3–C refractory specimens. The results showed that GONs were distributed well in α-Al2O3 powder by ball milling, and the size and thickness of GONs depended on the amount of expanded graphite added. The GONs enhanced the formation of ceramic whiskers in the specimens at lower temperature owing to their higher reactivity than graphite flake. The mechanical properties such as cold modulus of rupture (CMOR), flexural modulus (E), force and displacement curves of Al2O3–C refractories with GONs were improved compared with those without GONs. This improvement was attributed to the strengthening effects of GONs at 800 °C and the synergetic strengthening effects with graphite flake and the in-situ formed whiskers at 1000–1400 °C.