Corrosion mechanism of H2O on Sm2Fe17 and nitrogenation process of corroded Sm2Fe17

Abstract

Abstract Sm2Fe17 prepared by reduction-diffusion method needs to be washed with water to remove calcium oxide. Electrochemical corrosion occurs when Sm2Fe17 powder is in contact with liquid water. Corrosion mechanism of H2O on Sm2Fe17 powder and nitrogenation process of corroded Sm2Fe17 were studied by analyzing the structure and morphology. It is indicated that the metallic hydroxide forms and deposits on the Sm2Fe17 powder surfaces during water corrosion. At the same time, oxygen and hydrogen enter the unit cell of Sm2Fe17, causing a slight increase in Curie temperature. In the subsequent nitriding process, the hydroxide is dehydrated and hydrogen is desorbed. The resulting oxide reacts with Sm2Fe17Nx to form α-Fe and Sm2O3. Thermodynamic calculations using the HSC Chemistry 6.0 software indicate that the reaction can occur spontaneously. The effect of water corrosion on the magnetic properties of the nitride can be eliminated by hydrogen reduction prior to nitriding.