Influences of Al2O3 grain size on high-temperature oxidation of nano-Ni/Al2O3 composites

Pham, Hai Vu; Maruoka, Daisuke; Nanko, Makoto

doi:10.1016/j.jascer.2016.01.003

Cited by 19 publications

(18 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As for the as‐sintered specimens, oxidation of Ni particles also took place during the high‐temperature bending tests. However, the thickness of oxidized zone of as‐sintered specimens in such conditions would be approximately 3 μm or less, according to a study reported by the authors . The formation of oxidized zone on as‐sintered specimens is therefore negligible, compared with the as‐healed ones.…”

Section: Discussionmentioning

confidence: 94%

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

Pham

Nanko

Nakao

2016

Int J Applied Ceramic Tech

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 94%

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

Pham

Nanko

Nakao

2016

Int J Applied Ceramic Tech

Self Cite

View full text Add to dashboard Cite

show abstract

“…The Ti 2 AlC particles within this layer do not have the stoichiometry of the starting material due to the diffusion and subsequent oxidation of Ti, Al, and/or C at the surface. Beyond this depth, XMA confirms that the MAX phase particles retain their original stoichiometry of 2:1:1 for Ti:Al:C. Although undoped fine grained alumina favors inward diffusion of oxygen, oxidation of the MAX‐Phase particles proceeds by an outward diffusion of the cations (Al 3+ and Ti 4+ ), which is not influenced by the grain size of the matrix . The depleted region is limited to about 20 μm (same as the maximum particle size), and hence alumina acts as a strong barrier against oxidation of particles embedded in the depth of the composite.…”

Section: Resultsmentioning

confidence: 82%

“…Beyond this depth, XMA confirms that the MAX phase particles retain their original stoichiometry of 2:1:1 for Ti:Al:C. Although undoped fine grained alumina favors inward diffusion of oxygen, 42,43 oxidation of the MAX-Phase particles proceeds by an outward diffusion of the cations (Al 3+ and Ti 4+ ), which is not influenced by the grain size of the matrix. 44 The depleted region is limited to about 20 lm (same as the maximum particle size), and hence alumina acts as a strong barrier against oxidation of particles embedded in the depth of the composite. The orientation of the basal planes of a particle to the surface may also influence the rate at which Al and Ti diffuse out.…”

Section: Stability Of the Dispersed Ti 2 Alc Particles In The Al 2 mentioning

confidence: 99%

Autonomous high‐temperature healing of surface cracks in Al₂O₃ containing Ti₂AlC particles

et al. 2018

View full text Add to dashboard Cite

In this work, the oxidation-induced crack healing of Al 2 O 3 containing 20 vol.% of Ti 2 AlC MAX phase inclusions as healing particles was studied. The oxidation kinetics of the Ti 2 AlC particles having an average diameter of about 10 lm was studied via thermogravimetry and/or differential thermal analysis. Surface cracks of about 80 lm long and 0.5 lm wide were introduced into the composite by Vickers indentation. After annealing in air at high temperatures, the cracks were filled with stable oxides of Ti and Al as a result of the decomposition of the Ti 2 AlC particles. Crack healing was studied at 800, 900, and 1000°C for 0.25, 1, 4, and 16 hours, and the strength recovery was measured by 4-point bending. Upon indentation, the bending strength of the samples dropped by about 50% from 402 AE 35 to 229 AE 14 MPa. This bending strength increased to about 90% of the undamaged material after annealing at 1000°C for just 15 minutes, while full strength was recovered after annealing for 1 hour. As the healing temperature was reduced to 900 and 800°C, the time required for full-strength recovery increased to 4 and 16 hours, respectively. The initial bending strength and the fracture toughness of the composite material were found to be about 19% lower and 20% higher than monolithic alumina, respectively, making this material an attractive substitute for monolithic alumina used in high-temperature applications. K E Y W O R D Salumina, MAX phase, oxidation kinetics, self-healing, Ti 2 AlC | INTRODUCTIONSintered alumina is an attractive material for high-temperature applications due to its heat, corrosion, and wear resistance. 1,2The strength and hardness of this material is maintained up to high temperatures.3 However, the brittle nature of Al 2 O 3 results in a poor damage tolerance and hence limits its use. 4Small cracks or defects can readily lead to abrupt fracture; however, autonomous repair of small crack damage may postpone or even mitigate failure. It has been reported that crack damage in alumina can be healed by high-temperature oxidation of dispersed SiC particles. [5][6][7][8][9][10] Recently, it has also been shown that dispersed TiC particles can effectively heal cracks in alumina 11,12 by the formation of TiO 2 and even require much lower oxidation temperatures than SiC particles. Ideally, in an Al 2 O 3 , matrix cracks should be healed by Al 2 O 3 forming healing particles such as Al, but this is not feasible due to its low-melting temperature of 660°C. 13 Hence, thisThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

show abstract

“…NiO does not coexist with Al 2 O 3 , which has been discussed elsewhere. 5,8,12,14) This fact obviously indicates that the top surface layer is the NiAl 2 O 4 layer. Noticeably, the thickness of the top surface layer observed on an undoped sample was slightly higher than that of a Sr-doped one.…”

Section: Oxidation Testsmentioning

confidence: 96%

Strontium Doping Effect on High-Temperature Oxidation of Nano-Ni Dispersed Alumina Composites

Pham

Nanko

2018

Mater. Trans.

Self Cite

View full text Add to dashboard Cite

Two sets of 0.1 mol% Sr-doped 5 vol% Ni/Al 2 O 3 and undoped 5 vol% Ni/Al 2 O 3 samples were fabricated by the pulsed electric current sintering technique to investigate the influence of Sr-doping effects on the high-temperature oxidation. Oxidation tests were conducted in air at temperature ranges of 12001400°C for 110 d. Oxidation of Ni within the matrix at high temperatures induced formations of the top surface layer and the oxidized zone. The top surface layer was composed of the oxidation product-NiAl 2 O 4 , while the oxidized zone consisted of Al 2 O 3 matrix and NiAl 2 O 4. Formation of the oxidized zone of undoped and Sr-doped samples followed the parabolic law. The parabolic rate constant of Sr-doped samples was approximately two times smaller than that of undoped samples. The apparent activation energies on the growth of the oxidized zone were determined to be 479 and 476 kJ/mol for undoped and Sr-doped 5Ni/Al 2 O 3 , respectively. Sr-doping reduced oxygen transport along Al 2 O 3 grain boundaries and enhanced the high-temperature oxidation resistance of Ni/Al 2 O 3 .

show abstract

Influences of Al₂O₃ grain size on high-temperature oxidation of nano-Ni/Al₂O₃ composites

Cited by 19 publications

References 19 publications

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

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

Autonomous high‐temperature healing of surface cracks in Al₂O₃ containing Ti₂AlC particles

Strontium Doping Effect on High-Temperature Oxidation of Nano-Ni Dispersed Alumina Composites

Contact Info

Product

Resources

About

Influences of Al2O3 grain size on high-temperature oxidation of nano-Ni/Al2O3 composites

Cited by 19 publications

References 19 publications

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

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

Autonomous high‐temperature healing of surface cracks in Al2O3 containing Ti2AlC particles

Strontium Doping Effect on High-Temperature Oxidation of Nano-Ni Dispersed Alumina Composites

Contact Info

Product

Resources

About

Influences of Al₂O₃ grain size on high-temperature oxidation of nano-Ni/Al₂O₃ composites

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

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

Autonomous high‐temperature healing of surface cracks in Al₂O₃ containing Ti₂AlC particles