Enhanced thermal shock resistance of low‐carbon Al <sub>2</sub> O <sub>3</sub> ‐C refractories via CNTs/MgAl <sub>2</sub> O <sub>4</sub> whiskers composite reinforcement
Chunzhuo Feng, Guoqing Xiao, Donghai Ding, Changkun Lei, Lihua Lv, Xiaochuan Chong, Yuan Feng, Chao Zou
Abstract
Abstract The CNTs/MgAl 2 O 4 whiskers composite reinforcement was prepared by catalytic carbon‐bed sintering and added to low‐carbon Al 2 O 3 ‐C refractories to enhance the thermal shock resistance of refractories. The effects of Ni(NO 3 ) 2 ·6H 2 O content on the phase and microstructure of CNTs/MgAl 2 O 4 were investigated. The nano‐indentation technology was used to quantitatively evaluate the effect of CNTs/MgAl 2 O 4 on the thermal shock resistance of low‐carbon Al 2 O 3 ‐C refractories, and the toughening mechanism of CNTs/MgAl 2 O 4 on refractories was further investigated. The results revealed that the inner and outer diameters of the CNTs were approximately 5.69 and 16.26 nm, respectively. The CNTs winded around interlocking structural MgAl 2 O 4 whiskers with a high aspect ratio (>100), which was beneficial to the dispersion of CNTs in the refractory matrix. The thermal shock resistance of low‐carbon Al 2 O 3 ‐C refractories was significantly improved by adding 3.0 wt.% of CNTs/MgAl 2 O 4 (named C3). The specific fracture energy of refractory matrix and residual strength ratio of C3 reached 141 N·m −1 and 39.2%, which were 29.4% and 97.0% higher than those of the blank sample (109 N·m −1 and 19.9%), respectively. This is because the refractory matrix was significantly reinforced by CNTs and MgAl 2 O 4 whiskers, promoting the occurrence of “bridging” and “crack deflection” and the generation of microcracks in the refractory matrix.