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

2011 ◽  
Vol 696 ◽  
pp. 378-383 ◽  
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.

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

2010 ◽  
Vol 638-642 ◽  
pp. 2148-2153 ◽  
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.

Crack-Healing Effectiveness of Nano Ni + SiC Co-Dispersed Alumina Hybrid Materials

2010 ◽  
Vol 89-91 ◽  
pp. 365-370 ◽  
Author(s):  
Daisuke Maruoka ◽  
Yoku Sato ◽  
Makoto Nanko
Keyword(s):  
Heat Treatment ◽  
Hybrid Materials ◽  
Powder Mixture ◽  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Bending Strength ◽  
Distilled Water ◽  
Crack Healing ◽  
Temperature Oxidation ◽  
Pulsed Electric Current

Crack-healing effectiveness of nano-Ni+SiC co-dispersed Al2O3 hybrid materials by heat treatment was studied as well as oxidation behavior. The starting powder mixture was prepared by drying slurry consisting of distilled water, Al2O3, SiC powder and nickel nitrate. After reduction, the powder mixture was densified by pulsed electric current sintering. Cracks were introduced by a Vickers indenter. Specimens were exposed into air at temperature ranging from 1000 and 1300°C for 1 and 48 h. Thickness of oxidized zone in SiC+nano-Ni/Al2O3 thinner than nano-Ni/Al2O3. Cracks of SiC+nano-Ni/Al2O3 disappeared completely, for example, by oxidation at 1200°C for 6 h, as same as nano-Ni/Al2O3. Bending strength of crack-disappeared SiC+nano-Ni/Al2O3 showed 519 MPa and was comparable with that of as-sintered one. SiC+nano-Ni/Al2O3 pocesses crack-healing effectiveness with improved high-temperature oxidation resistance.

High Temperature Oxidation of Ti45.4Al4.8Nb and Ti46Al2Mo2Nb Alloys

2005 ◽  
Vol 475-479 ◽  
pp. 801-804
Author(s):  
J.W. Kim ◽  
Dong Bok Lee
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Middle Layer ◽  
Tio2 Layer ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Oxidation Characteristics ◽  
Dissolved Ions

The Ti46Al2Nb2Mo and Ti45.4Al4.8Nb alloys were oxidized isothermally and cyclically in air between 800 and 1000oC, and their oxidation characteristics were investigated. Nb and Mo were beneficial to oxidation resistance. The initially formed thin TiO2-rich scale changed to an outer, superficial TiO2 layer, a thick Al2O3-rich middle layer, and an inner (TiO2-rich, Al2O3-deficient) layer, as the extent of oxidation progressed. The dissolved ions of Mo and Nb had a tendency to be expelled from the outer TiO2 layer, which was formed by the outward diffusion of Ti ions, to the inner (TiO2-rich, Al2O3-deficient) layer, which was formed by the inward transport of oxygen, owing to the nobility of Mo and Nb when compared to Ti and Al.

Effects of Aluminizing on the High Temperature Oxidation Behavior of High Silicon Cast Iron

2009 ◽  
Vol 79-82 ◽  
pp. 2151-2154
Author(s):  
Meng Bin Lin ◽  
Chaur Jeng Wang
Keyword(s):  
Cast Iron ◽  
High Temperature ◽  
High Temperature Oxidation ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
X Ray ◽  
Oxygen Penetration ◽  
Coating Layers ◽  
High Silicon ◽  
High Temperature Oxidation Behavior

In this study, the aluminizing of high silicon cast iron by hot-dipping in pure Al melt was performed and their high temperature oxidation behaviour was tested at 750 °C for virous exposure time. After high temperature oxidation tests, the microstructure analysis of all samples were investigated by means of metallographical examination, scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectrometer (EDS) and X-ray diffractometry (XRD).The results showed that the coating layers consisted of three layer, in the sequence of Al, Fe-Al and Si-rich layers from external topcoat to substrate. Nodules graphite had a blocking effect to retard the outward diffusion of Fe atoms and impeded the growth of Fe2Al5 in C-axis. Eventually, the cast iron substrate was oxidized directly by oxygen penetration via the greater cracks and pores to form Fe oxide nodules after 750 °C oxidation for 48h.

High temperature oxidation of ion-plated CrN films

1994 ◽  
Vol 9 (1) ◽  
pp. 151-155 ◽  
Author(s):  
Hiroshi Ichimura ◽  
Atsuo Kawana
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Mass Gain ◽  
The Self ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Ion Plating ◽  
Self Diffusion ◽  
Steel Substrates ◽  
Self Diffusion Coefficient

The high-temperature oxidation of CrN films which were deposited onto stainless steel substrates using an arc ion plating apparatus was studied at temperatures ranging from 1023 to 1173 K for 0.6 to 480 ks in air. The oxidation rate obtained from mass gain as a function of time was found to fit well to a parabolic time dependence. Formed oxide layers were analyzed by XRD, SEM, and SAM. An activation energy of the oxidation of CrN was slightly lower than that of the self-diffusion coefficient of Cr ion in Cr2O3. It is concluded that the oxidation of CrN is controlled by the outward diffusion of Cr ions through the Cr2O3 layer formed on each CrN grain.

scholarly journals High Temperature Oxidation Behaviors of BaO/TiO2 Binary Oxide-Enhanced NiAl-Based Composites

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6510
Author(s):  
Bo Li ◽  
Ruipeng Gao ◽  
Hongjian Guo ◽  
Congmin Fan
Keyword(s):  
High Temperature ◽  
Oxidation Resistance ◽  
High Temperature Oxidation ◽  
Oxidation Mechanism ◽  
High Tech ◽  
Slight Reduction ◽  
Application Process ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Resistance Performance

High temperature lubricating composites have been widely used in aerospace and other high-tech industries. In the actual application process, high temperature oxidation resistance is a very importance parameter. In this paper, BaO/TiO2-enhanced NiAl-based composites were prepared by vacuum hot-press sintering. The oxidation resistance performance of the composites at 800 °C was investigated. The composites exhibited very good sintered compactness and only a few pores were present. Meanwhile, the composite had excellent oxidation resistance properties due to the formation of a dense Al2O3 layer which could prevent further oxidation of the internal substrate; its oxidation mechanism was mainly decided by the outward diffusion of Al and the inward diffusion of O. The addition of BaO/TiO2 introduced more boundaries and made the Kp value increase from 1.2 × 10−14 g2/cm4 s to 3.3 × 10−14 g2/cm4 s, leading to a slight reduction in the oxidation resistance performance of the composites—although it was still excellent.

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