Enhanced mechanical properties of lightweight Al 2 O 3 ‐C refractories reinforced by combined one‐dimensional ceramic phases

Abstract We prepared a new lightweight Al 2 O 3 ‐C refractory material with a higher strength by using microporous corundum aggregates instead of dense tabular corundum aggregates, which was reinforced by in situ formed SiC whiskers, multi‐walled carbon nanotubes (MWCNTs), and mullite rods. A comparative study of the microstructure, mechanical properties, and fracture behavior was carried out for dense and lightweight Al 2 O 3 ‐C refractories coked at 1200°C and 1400°C, respectively. By using the microporous corundum aggregates, a better aggregate/matrix interface bonding and an optimized distribution of SiC whiskers were obtained. The SiC whiskers formed inside the microporous corundum aggregates and simultaneously in the matrix by a vapor‐solid reaction mechanism, resulting in an enhancement at the microporous aggregate/matrix interface. Furthermore, the in situ formed MWCNTs and well‐developed mullite rods at 1200°C in the matrix also contributed to the better interface structure. Thus, due to the improved microporous aggregate/matrix interface, the crack propagation along the aggregate/matrix interface was suppressed, resulting in an increased crack propagation within the aggregates. Consequently, the synergy between microporous corundum aggregates and combined one‐dimensional ceramic phases caused a lower bulk density but a markedly higher strength, a higher fracture energy, and a higher toughness of lightweight Al 2 O 3 ‐C refractories compared to the dense ones. Overall, our study allows to overcome the traditional concept that a higher strength of refractories is reached by a higher density.