Effect of Leaching on Surface Microstructure and Chemical Composition of Al-Based Quasicrystals
We have studied the effect of leaching treatments on the surface microstructure and chemical composition of Al-based quasicrystals. The high symmetry surfaces of single grain icosahedral (i-) Al–Cu–Fe and decagonal (d-) Al–Ni–Co quasicrystals and a polygrain i-Al–Pd–Re quasicrystal with random surface orientation were leached with NaOH solution at varying times and the resulting surfaces were characterized by scanning electron microscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy. The leaching treatments preferentially remove Al producing nanoparticles of the transition metals and their oxides. The leached fivefold surface of i-Al–Cu–Fe exhibits micron sized dodecahedral cavities on which the nanoparticles are precipitated. However, no specific microstructure has been observed on the tenfold surface of d-Al–Ni–Co and the polygrain i-Al–Pd–Re. The quasicrystalline surface can be regained after polishing the leached layer, indicating that leaching occurs only in a limited depth from the surface. This was revealed by low energy electron diffraction after the surface was prepared under ultra high vacuum conditions. These results provide important information for preparation of model catalysts of nanoparticles of catalytically active metals on quasicrystal surfaces.
KeywordsSpark Plasma Sinter Ultra High Vacuum Model Catalyst Show Scanning Electron Microscopy Image Icosahedral Quasicrystal
H.R.S. is grateful to Engineering and Physical Sciences Research Council (EPSRC) for funding (Grants No. EP/D071828/1). T.P.Y. thanks the Department of Science and Technology (DST)-India for BOYACAST fellowship for this work. M.L. is grateful to EPSRC for support through Doctoral Training Grant. The authors would like to thank Dr. T. Joyce in the University of Liverpool for SEM facility. The quasicrystal samples were grown by T.A. Lograsso and A.R. Ross in Ames Laboratory, Iowa State University, USA. We thank A.P. Tsai in Tohoku University and V. Fournée and J. Ledieu at CNRS Nancy for fruitful discussions and J. Smerdon for critical reading of the manuscript.
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