Impact of Tuned Oxidation on the Surface Energy of Sintered Samples Produced from Atomised B-Doped Al-Cu-Fe Quasicrystalline Powders

Abstract

Super-hydrophobic surfaces and coatings have stimulated a great deal of research, with the aim being to achieve better wetting properties. Factors such as surface chemistry and roughness play an important role in changing the surface energy, which in turn leads to changes in the wettability. Here, we have analysed the time dependence of the oxide layer and possible surface adsorbates on the surface topography of an Al59Cu25Fe13B3 quasicrystalline material in relation to changes in the wettability. The quasicrystalline matrix phase was 94% of the sample volume, and it was covered by a very smooth, amorphous oxide layer. The AlB12 and AlFe2B2 boron-rich phases were embedded in the quasicrystalline material as a result of the 3 at.% boron addition, which made atomisation of the material a simpler process. Under ambient conditions, the sample was naturally covered by an oxide layer; therefore, it is referred to as “surfenergy” to distinguish it from the conventional surface energy of a bare quasicrystal surface. The growth of the oxide layer with atmospheric ageing and annealing at 500 °C in air for various times was investigated for both cases. The phase most prone to oxidation was the boron-rich AlFe2B2, which influenced the topography of the surface and accordingly the wetting behaviour of the specimen. We demonstrated that the surfenergy depends on the polar component, which is the most sensitive to the operating conditions. A correlation between the surfenergy components and the surface roughness was found. In addition, theoretical models to determine the wettability were included.

Keywords

• contact angle
• surface energy
• XPS
• microstructure
• SEM
• TEM