Recovery of mechanical strength by surface crack disappearance via thermal oxidation for nano-Ni/Al2O3 hybrid materials

Daisuke Maruoka, Makoto Nanko

Research output: Contribution to journalArticlepeer-review

27 Citations (Scopus)


Recovery of mechanical strength as a function of heat-treatment temperature and time was investigated in α-Al2O3-based hybrid materials containing with 5 vol% dispersed Ni nanoparticles (nano-Ni/Al 2O3) via fraction of surface crack disappearance. Surface cracks introduced by Vickers indentation disappeared completely because of the oxidation product NiAl2O4. Bending strengths of as-sintered and as-cracked samples were 490±58 and 180±15 MPa, respectively. Heat-treatment at 1000 °C for 1 h resulted in recovery of bending strength up to 550±190 MPa with 10% fraction of crack disappearance. The bending strength of samples heat-treated at higher temperatures or for longer durations was comparable with that of the as-sintered samples. Bending strength reached and remained at approximately 604 MPa when the fraction of surface crack disappearance was over 55%. As-recovered samples did not fracture at the surface cracks during the three-point bending test. Thus, recovery of mechanical strength was achieved by partial disappearance of the surface cracks. This observed recovery of mechanical strength was caused by a reduction in stress concentration at crack-tips covered with NiAl 2O4 formed from Ni2- along grain boundaries of the Al2O3 matrix.

Original languageEnglish
Pages (from-to)3221-3229
Number of pages9
JournalCeramics International
Issue number3
Publication statusPublished - 2013 Apr
Externally publishedYes


  • AlO
  • Corrosion
  • Nanocomposites
  • Self-healing

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Process Chemistry and Technology
  • Surfaces, Coatings and Films
  • Materials Chemistry


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