Introducing graphene (reduced graphene oxide) into Al matrix composites for enhanced high-temperature strength

Lamellar amorphous Al2O3 (am-Al2O3) in Al2O3/Al composites exhibits extreme strengthening effect on high-temperature strength, but suffers from efficacy loss because of crystallizing into granular gamma-Al2O3 at temperatures over 450 degrees C. Here, based on the existing solution-mixing process, reduced graphene oxide (rGO) sheets were introduced into Al2O3/Al composite to enhance its high-temperature strength for the first time. It was shown that rGO sheets within the am-Al2O3 films could prevent them from transforming into gamma-Al2O3 in the high-temperature hot-pressing processes. As a result, by addition of a very small number of rGO sheets, the composites were strengthened significantly at both room and high temperatures. Strengthening mechanisms at room and high temperatures were discussed. Furthermore, enhanced thermal stability of am-Al2O3 was explained by thermodynamics and kinetics factors. This work provides a novel application of graphene in structural materials.