Crack Disappearance by High-Temperature Oxidation of Alumina Toughened by Ni Nano-Particles

Abstract

Crack disappearance by high-temperature oxidation was studied in alumina (Al2O3) composites toughened by Ni nanoparticles. This process is performed in air at temperature ranging from 1000 to 1300°C for 1 to 48 h. The results showed that crack disappearance depends on both annealing temperature and time. Complete crack disappearance in this composite was confirmed at lower temperatures for long oxidation period, 1100oC for 48 h, and higher temperature for shorter time, 1300oC for 1 h in air. The crack disappearance mechanism was explained on the basis of the formation of NiAl2O4 spinel on sample surfaces produced by the oxidation reaction during the heat treatment.

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

“…The crack depth was approximately 90 μm. As the surface cracks can be completely healed by heat treatment in the air at 1200°C for 6 h, as‐healed specimens were prepared by heat treatment of as‐cracked specimens at this condition. The heat treatment temperature was monitored by using an R‐type thermocouple located near the specimens.…”

“…In order to overcome this disadvantage, there have been numerous studies attempting to provide ceramic matrix composites incorporating second‐phase dispersions such as platelets, fibers or whiskers, and particulates . In addition, dispersion of the secondary phases in the ceramic matrix composites contributes to its matrix self‐healing function when they are applied at high temperatures in the air …”

“…The authors' group has studied the self‐healing mechanism of nano‐Ni/Al 2 O 3 over the past decade . Oxidation of nano‐Ni particles in the matrix at high temperatures induced the formation of an internal oxidized zone and an external layer of oxidation product .…”

The effect of the TiC particle size on the preferred oxidation temperature for self-healing of oxide ceramic matrix materials

“…Of course, the required minimal temperature to trigger the healing reaction depends primarily on the chemical stability of the healing material in an oxygen-containing environment. This dependence has already been demonstrated (but apparently not been appreciated) in the combined first-generation studies on self-healing of Al 2 O 3 or Si 3 N 4 filled with SiC or Ni particles [3][4][5][6][7]. In these studies, the crack healing ability was studied as a function of both temperature (from 900 to 1400°C) and time (between 1 and 300 h) and widely different values were obtained for different particle sizes.…”

Recovery of Mechanical Property on Nano-Co Particles Dispersed Al₂O₃ via High-Temperature Oxidation

“…Since Ni/Al 2 O 3 contains metallic Ni particles, it is expected to have useful properties such as magnetism. 4) Our group has previously reported 20,21) that bending strength in Ni/Al 2 O 3 was decreased by Vickers indentation, and that the strength was recovered by heat treatment, for example, at 1200°C for 6 h in air. Surface cracks filled with oxidation product, NiAl 2 O 4 .…”