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.

Effect of Al-Cu-Fe Quasicrystal Particles on the Reinforcement of a Polymer–Matrix Composite: From Surface to Mechanical Properties

“…Six crystal phases could be confirmed. The major phase corresponds to the quasicrystal icosahedral phase (i-phase, space group Fm35), as verified by a direct correlation of the PXRD pattern obtained from a reference sample with the highest purity of quasicrystalline icosahedral phase [23]. The other minor phases are the cubic β-AlCu(Fe) phase (space group Im-3m, 229), the orthorhombic ω-phase Al 60 Cu 30 Fe 10 phase (space group Immm, 71), the cubic phase λ-Al 13 Fe 4 (space group Fm-3m, 225), orthorhombic phase Θ-AlFe 3 (space group Bmmm, 65), and hexagonal phase AlB 2 (space group P6/mmm, 191).…”

“…This sample contained a majority of the Al 62 Cu 25 Fe 13 icosahedral quasicrystal phase (i-phase), with no apparent grain texturing and the average grain size of the matrix QC phase being 20-70 micrometres. Additionally, the sample contained small amounts of minor phases, less than 4%, such as AlFe 2 B 2 and β-AlCu(Fe) and borides AlB 12 [23].…”

“…We measured the contact angle and the surface energy (referred to as surfenergy) of pure PPA polymer and PPA mixed with different amounts of quasicrystalline pow-der. These measurements were carried out using the Theta Lite-Biolin Scientific instrument, (Biolin Scientific, Göteborg, Sweden) following the detailed methods outlined in [23]. The term surfenergy is used to describe the surface energy of a material that has a native oxide layer, which naturally forms on a quasicrystal when exposed to air.…”

“…In our previous study [23], we established that passivating the surface of QCs alters their surface energy, termed surfenergy. It is the surface energy of the oxidised QC's surface, typically in the range of a few tens of mJ/m 2 .…”