Initial oxidation of quasicrystals – an investigation by high-resolution RBS and ERDA

Surfaces of icosahedral AlPdMn with 5-fold orientation can be prepared either to be fully icosahedral or to form a cubic overlayer. When decagonal AlNiCo is cut perpendicular to the 10-fold axis, a fully quasicrystalline surface is obtained, however a ‘mixed-type’ (quasicrystalline-periodic) surface is obtained, when cut parallel to this axis. A comparison of the oxidation behavior of these different surfaces should therefore shed light on the suggestion by Rivier [N. Rivier, New Horizons in Quasicrystals: Research and Applications, in: A.I. Goldman, D.J. Sordelet, P.A. Thiel, and J.M. Dubois (Eds.), World Scientific, Singapore, 1997, p. 188] that quasicrystals are more corrosion resistant than their crystalline counterparts. The initial oxidation of the surfaces was studied by measuring oxygen depth profiles with high-resolution ERDA. The paper also reports about the preparation of the surfaces and the measurement of highly resolved depth profiles of the metallic components by RBS during the preparation. In both cases a high-resolution electrostatic spectrometer was used for the energy analysis. The results are in favor of an enhanced oxidation resistance of quasicrystalline surfaces.