High‐temperature Bending Strength of Self‐Healing Ni/Al₂O₃ Nanocomposites

Abstract

Bending strength of 5 vol.% Ni/Al2O3 composites as a function of testing temperature is investigated at temperatures ranging from room temperature to 1200°C. Self‐healing performance at high temperatures of the composites is evaluated by conducting high‐temperature bending tests for as‐sintered, as‐cracked, and as‐healed specimens. Bending strength of as‐sintered specimens dramatically decreases from 995 MPa at room temperature to 205 MPa at 1200°C. Additionally, the plastic deformation of the as‐sintered specimens occurs when the testing temperature reaches to 1200°C. The values of high‐temperature bending strength of as‐healed specimens are comparable with those of as‐sintered specimens. Similar to that of as‐sintered specimens, bending strength of as‐healed specimens degrades when the testing temperature increases. Results of the present study indicate that the recovery of bending strength by the self‐healing function is able to achieve at temperatures as high as 1200°C. Unlike the mechanical behaviors at high temperatures of as‐sintered and as‐healed specimens, the bending strength of as‐cracked specimens slightly increases with the increase of testing temperature. This phenomenon is attributed to the effect of the self‐healing mechanism during high‐temperature bending tests.

Self-Healing of Ni/Mullite Hybrid Materials via High-Temperature Oxidation

“…The interface energy between SiC and Al 2 O 3 matrix is higher than the transgranular fracture energy that causes their fracture obeys the transgranular fracture mechanism. 32) Figure 9 shows the fraction of surface crack disappearance as a function of heat-treatment temperatures for 5Ni/mullite with the previously reported results on 5Ni/(10ZrO 2 + Al 2 O 3 ), 33) 5Ni/Al 2 O 3 , 34) and 5Co/Al 2 O 3 . 19) The Ni/mullite requires a lower heat-treatment temperature for surface crack-disappearance than the others nanocomposites based on Al 2 O 3 matrix.…”

“…In other words, self-healing performance in Ni/Al 2 O 3 system is greater than that of SiC/Al 2 O 3 . However, applications of Al 2 O 3 at high temperatures would be concerned on their bending strength 26) and creep properties. 27) Lessing et al reported the creep rate at 1450 C of dense mullite was approximately one order of magnitude less than that of monolithic Al 2 O 3 .…”

“…The fraction of surface crack-disappearance as a function of heat-treatment temperature for 5Ni/mullite, 5Ni/(ZrO 2 +Al 2 O 3 ),33) 5Ni/ Al 2 O 3 ,34) and 5Co/Al 2 O 3 19). …”

Role of CeAl11O18 in reinforcing Al2O3/Ti composites by adding CeO2

“…Cracks are easily introduced into brittle ceramics during subsequent machining processes and operations, resulting in dramatically degraded mechanical strength 1 . In order to eliminate these surface cracks, it is of great importance to improve fracture toughness to enhance crack resistance.…”

Electrochemically assisted room‐temperature crack healing of ceramic‐based composites

“…However, they are brittle by nature and, thus, surface cracks and/or defects are easily introduced during machining processes or when ceramics are used as structural components in practical applications. When cracks appear in a ceramic material, its fracture strength and reliability are considerably reduced because such cracks act as fracture initiation sites when stress is exerted at the crack edges. Introducing self‐healing‐ability into ceramic has been an effective approach to eliminate existing surface cracks and recover lost mechanical strength and reliability.…”