[Retracted] A Comparative Study on Crack‐Healing Ability of Al2O3/SiC Structural Ceramic Composites Synthesized by Microwave Sintering and Conventional Electrical Sintering

Abstract

This study was conducted to assess and compare the crack‐healing ability of conventional electrical sintered and microwave sintered Al 2 O 3 / x wt. % SiC ( x = 5, 10, 15, and 20) structural ceramic composites. The crack‐healing ability of both conventional electrical sintered and microwave sintered specimens was studied by introducing a crack of ∼100 µ m length by Vickers’s indentation and conducting a heat treatment at 1200°C for dwell time of 1 h in air. The flexural or bending strength of sintered, cracked, and crack‐healed specimens was determined by three‐point bending test, and the phase variations by X‐ray diffraction and SEM micrographs before and after crack‐healing of both the sintering methods were studied and compared. The results show that almost all the specimens recovered their strength after crack‐healing, but the strength of microwave sintered Al 2 O 3 /SiC structural ceramic composites has been shown to be better than that of conventional electrical sintered Al 2 O 3 /SiC structural ceramic composites. The microwave sintered crack‐healed Al 2 O 3 /10 wt. % SiC specimen shows higher flexural strength of 794 MPa, which was 105% when compared with conventional electrical sintered Al 2 O 3 /10 wt. % SiC and crack‐healed Al 2 O 3 /10 wt. % SiC specimen. It was found by X‐ray diffractogram that before crack‐healing, all the conventional electrical sintered samples have SiO 2 phase which reduce the crack‐healing ability and microwave sintered samples with 15 and 20 wt. % SiC show lesser SiO 2 phase and 5 and 10 wt. % SiC samples have no SiO 2 phase before crack‐healing. However, after crack‐healing treatment, all the samples have distinct SiO 2 phase along with Al 2 O 3 and SiC phases. Microwave sintered Al 2 O 3 /10 wt. % SiC specimen cracks were fully healed which was evident in SEM micrographs.