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Hallstahammar, Sweden

Pang W.K.,Curtin University Australia | Low I.M.,Curtin University Australia | Hanna J.V.,University of Warwick | Palmquist J.P.,Kanthal AB
Ceramic Engineering and Science Proceedings | Year: 2010

This paper describes the use of secondary-ion mass spectrometry (SIMS), nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM) to identify the amorphous silica in Ti3SiC2 oxidised at 500-1000°C The formation of an amorphous SiO2 layer and its growth in thickness with temperature was monitored using dynamic SIMS. Results of NMR and TEM verify for the first time the direct evidence of amorphous silica formation during the oxidation of Ti3SiC2 at 1000°C.


Pang W.K.,Curtin University Australia | Low I.M.,Curtin University Australia | O'Connor B.H.,Curtin University Australia | Peterson V.K.,Australian Nuclear Science and Technology Organisation | And 2 more authors.
Journal of Alloys and Compounds | Year: 2011

The thermal stability of Ti2AlC at elevated temperature (1000-1550 °C) in vacuum has been investigated using in situ neutron diffraction. At temperatures above 1400 °C, Ti2AlC became unstable and began to decompose via sublimation of Al, resulting in a porous surface layer of TiCx being formed. The apparent activation energy for Ti2AlC decomposition was determined to be 85.7 ± 2.6 kJ mol-1. The kinetics of isothermal phase decomposition was modelled using least-squares linear regression fitting and the Avrami equation. The corresponding least-squares regression exponent (R2) and Avrami constants (k and n) for isothermal decomposition were determined to be 0.89, 0.268 min-n and 0.1, respectively. © 2010 Elsevier B.V. All rights reserved.


Pang W.K.,Curtin University Australia | Low I.M.,Curtin University Australia | O'Connor B.H.,Curtin University Australia | Studer A.J.,Australian Nuclear Science and Technology Organization | And 3 more authors.
Journal of Physics: Conference Series | Year: 2010

The susceptibility of four MAX phases (Ti2AlC, Cr 2AlC, Ti3AlC2, and Ti3SiC 2) to high-temperature thermal dissociation in vacuum has been investigated using in-situ neutron diffraction. In high vacuum, these phases decomposed above 1400°C through the sublimation of M and A elements, forming a surface coating of MC. The apparent activation energies for the decomposition of sintered Ti3SiC2, Ti3AlC2, and Ti2AlC were determined to be 179.3, -71.9, and 85.7 kJ mol -1, respectively. The spontaneous release of Ti2AlC and TiC from de-intercalation during decomposition of Ti3AlC2 resulted in a negative activation energy. © 2010 IOP Publishing Ltd.


Sonestedt M.,Chalmers University of Technology | Frodelius J.,Linkoping University | Sundberg M.,Kanthal AB | Hultman L.,Linkoping University | Stiller K.,Chalmers University of Technology
Corrosion Science | Year: 2010

The oxidation behaviour of Ti2AlC bulk and high velocity oxy-fuel spray deposited coatings has been investigated for temperatures up to 1200°C. X-ray diffraction and electron microscopy show that bulk Ti2AlC forms a continuous layer of α-Al2O3 below a layer of TiO2 at temperatures as low as 700°C. Oxidation of the Ti2AlC coatings is more complex, and also involves the phases Ti3AlC2, TiC, and TixAly, formed during the spraying process. α-Al2O3 is observed, however, it is unevenly distributed deep into the material, and does not form a continuous layer essential for good oxidation resistance. © 2010 Elsevier Ltd.


Sonestedt M.,Chalmers University of Technology | Frodelius J.,Linkoping University | Palmquist J.-P.,Kanthal AB | Hogberg H.,Linkoping University | And 2 more authors.
Journal of Materials Science | Year: 2010

The microstructure formation and phase transformations in Ti 2AlC-rich coatings deposited by High Velocity Oxy-fuel spraying of Maxthal 211® powders is presented. High resolution electron microscopy analysis, using both scanning and transmission electron microscopy with energy dispersive spectrometry and energy filtering, combined with X-ray diffraction reveals that the coatings consist of Ti2AlC grains surrounded by regions of very small TiC grains embedded in Ti x Al y . The composition of the Ti x Al y depends on its surrounding and varies with size and distribution of the adjacent TiC grains. Impact of spray parameters on coating microstructure is also discussed. Two spray parameters were varied; powder size distribution and flame power. They were found to greatly affect the coating microstructure. Increasing powder size and decreasing flame power increase the amount of Ti2AlC, but produces thinner coatings with lower cohesion. Larger powder size will also decrease oxygen incorporation. © 2010 Springer Science+Business Media, LLC.

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