A multidisciplinary study on magnesium

Abstract

During plasma electrolytic oxidation of a magnesium alloy (96 % Mg, 3 % Al and 1 % Zn), a luminescence spectrum in the wave number range between 19950 and 20400 cm-1 was obtained. The broad peak with a clearly pronounced structure was assigned to the v′-v″ = 0 sequence of the B 1Σ +→X1Σ + electronic transition of MgO. Quantum-mechanical perturbative approach was applied to extract the form of the potential energy curves for the electronic states involved in the observed spectrum, from the positions of the spectral bands. These potential curves, combined with the results of quantum-chemical calculations of the electric transition moment, were employed in subsequent variational calculations to obtain the Franck-Condon factors and transition moments for the observed vibrational transitions. Comparing the results of these calculations with the measured intensity distribution within the spectrum, the relative population of the upper electronic state vibration levels was derived. This enabled the plasma temperature to be estimated. Additionally, the temperature was determined by analysis of the recorded A2Σ +(v′ = 0) - X2∏ (v″ = 0) emission spectrum of OH. The composition of the plasma containing magnesium, oxygen, and hydrogen under the assumption of a local thermal equilibrium was calculated in the temperature range up to 12000 K and for pressures of 105, 10 6, 107, and 108 Pa, in order to explain the appearance of the observed spectral features and to contribute to the elucidation of processes occurring during the electrolytic oxidation of Mg. Copyright © 2012 (CC) SCS.