Amorphous Metallic Alloys Surface Changes
AMORPHOUS METALLIC ALLOYS SURFACE CHANGES
IN THE OXIDATION-REDUCTION
REACTIONS WITH NO
M. O. Kovbuz, O. M. Hertsyk, L. M. Bednarska,
M. M. Yatsyshyn, K. R. Gorbachevska
Ivan Franko National University of L`viv, L`viv, Ukraine
Taking into account that the rejection of a gaseous NO in atmosphere is extraordinarily toxic, we did an attempt to estimate the nitrogen monoxide action on the surface of the several amorphous metallic alloys (АМA). It could be used for prognostication of catalytic action of these alloys in processes of finally oxidation or NO reduction. The AMA surface structure heterogeneity and the element content both stipulate their active catalytic action in the different chemical processes.
The studying of surface activity of the next AMA Fe55.0Ni30.0Cr6.8Mo0.1W0.5V2.0Si2.5B3.1 (1), Fe66.5Ni17.0Cr8.0Mo0.1W1.9V0.4Si2.9B3.2 (2)
was carried out with the using of voltammetry and potentiometry methods. For the NO influence estimation on the alloy surface, the specimens were exposed from 10 till 240 minutes in environment of oxygen absence and in atmosphere of pure oxide, which was received from interaction of Cu and HNO3 solution.
On the base of potentiometric researches was deduced, that already over 10 minutes of NO contact with alloy surface the exact changes take place, that, evidently, are associated with blocking of surface by an interaction products. By such products may be the hard solutions of nitrogen in ferrum compound, that form a-phase. The concentration of the last at the room temperature may reaches to 0,05%, and at the cases of higher pressure of NO and the increasing of contact duration with AMA surface the nitrogen content may rise till 1~2%. Amorphous alloys catalyse the reduction of oxides of nitrogen to N2 or NH3, which are the active agents of nitration process. After 240 minutes on the curves of surface potential changes the small minimums and maximums were appeared that pointed on the activation of surface processes in view both the chemical and physical surface reactions.
Voltammetry characteristics of AMA-2, which was previously exposed in similar conditions, are essentially different. Corrosion potentials become more positive, which after long-term electrochemical potential cycling shifted in cathodic field that points on protection action of nitration process. Corrosion current and exchange currents increase. Specially this is observed in the case of four hours exposition of alloy in NO atmosphere.
So, it may be concluded that the presence of essential content of Ni, Cr, and possible also the content of V and W in complex cause the high reaction ability of AMA surface in oxididation-reduction processes, especially, with monooxide of nitrogen.
Related articles::