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

By adding 0 % to 50 % Cr2O3 ceramic particles, the enamel composite coating is produced on the surface of TC4 titanium alloys. The detection analysis indicates that with the increase of the amount of Cr2O3 particles added, the density of enamel coating increases as well, and the amount of the pore holes decreases at the same time, but the enamel coating becomes porous with more than 30 % of the amount of Cr2O3 particles added. The main crystalline phases of enamel coating are NaAlSi3O8 and Ca2SiO4, whereas the Cr2O3 ceramic particles added are mainly presented as an independent phase, and part of the particles are in the form of Ca5Cr3O12 phase after the reaction. The enamel coating with 30 % Cr2O3 ceramic particles added has the best high-temperature oxidation resistance, mainly because the main crystalline phase of NaAlSi3O8 is changed into Na2Si2O5 during the high-temperature oxidation, which is beneficial to the self-healing of the coating.

Download Full-text

High-Temperature Oxidation Resistance and Crack-Healing Function of Ni/Al2O3 Nano-Hybrid Materials

Materials Science Forum ◽

10.4028/www.scientific.net/msf.638-642.2148 ◽

2010 ◽

Vol 638-642 ◽

pp. 2148-2153 ◽

Cited By ~ 2

Author(s):

Makoto Nanko

Keyword(s):

High Temperature ◽

Oxidation Resistance ◽

High Temperatures ◽

Hybrid Materials ◽

High Temperature Oxidation ◽

The Other ◽

High Temperature Annealing ◽

Crack Healing ◽

Temperature Oxidation ◽

Co Dispersion

High-temperature oxidation resistance of Ni/Al2O3 nano-hybrid materials was described in this paper. Y2O3 doping and SiC co-dispersion in Ni/Al2O3 nano-hybrid materials are useful techniques to improve high-temperature oxidation resistance. On the other hand, nano-Ni/Al2O3 has the crack healing function by high-temperature annealing in air. SiC-Ni/Al2O3 nano-hybrid materials have similar crack healing performance with better oxidation resistance at high temperatures than Ni/Al2O3 nano-hybrid materials.

Download Full-text

Crack Healing of Nano-Ni/Al2O3 Hybrid Materials via High-Temperature Oxidation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.696.378 ◽

2011 ◽

Vol 696 ◽

pp. 378-383 ◽

Cited By ~ 6

Author(s):

Daisuke Maruoka ◽

Makoto Nanko

Keyword(s):

High Temperature ◽

Hybrid Materials ◽

High Temperature Oxidation ◽

Bending Strength ◽

Crack Healing ◽

Temperature Oxidation ◽

Outward Diffusion ◽

Si Doping ◽

Si Doped ◽

Co Dispersion

Crack-healing effectiveness was investigated on 5 vol% nano-Ni dispersed Al2O3hybrid materials. Influence of the Y or Si doping or SiC co-dispersion was also studied on the crack healing behavior. Cracks were introduced by a Vickers indentation to be a crack length of approximately 60 μm. Cracks of nano-Ni/Al2O3were completely disappeared, for example, by oxidation at 1200°C for 6 h in air, Y/Si doped one and SiC co-dispersed one have similar performance of crack disappearance. Bending strength of crack-disappeared samples showed about 550 MPa and was comparable or improved with that of as-sintered one. Mechanism of crack healing was considered as filling up of cracks by NiAl2O4oxidation product which is developed by outward diffusion of cations at grain boundary of Al2O3matrix. Nano-Ni/Al2O3with Y or Si doping or SiC co-dispersion are realized to have crack-healing effectiveness with improved high-temperature oxidation resistance.

Download Full-text