Diffusion of chromium, manganese, and iron in MnCr2O4 spinel
Tóm tắt
As a result of the oxidation of chromium (Cr)-manganese (Mn) steels, a multilayer scale is formed. The intermediate layer of this scale is composed of MnCr2O4 spinel, and the outer layer is composed of MnO. The aim of the current study is to examine self-diffusion processes in MnCr2O4 spinel by a tracer method. In experiments, the radioisotopes 54Mn, 51Cr, and 59Fe were used. The serial sectioning method was applied for the simultaneous evaluation of diffusion rates of Cr, Mn, and iron (Fe) in MnCr2O4 spinel at 1173 K under a pressure of 105 Pa in SO2 containing 10 Pa O2. This spinel was obtained by a modified sol-gel method from metal nitrates (R. Gajerski and Z. Zurek, personal communication, 14.04.2004). It was found that the dominant mechanism of Mn transport in the studied samples is a volume diffusion, while Cr and Fe are transported mainly through the high-diffusivity paths.
Tài liệu tham khảo
R. Gajerski and Z. Żurek, private communication, 14.04.2004
Z. Żurek, J. Gilewicz-Wolter, M. Hetmańczyk, J. Dudała, and A. Stawiarski, High Temperature Corrosion of Chromium-Manganese Steels in Sulfur Dioxide, Oxid. Metals, in press
S.H. Song and Z.X. Yuan, Electrical Properties of MnCr2O4 Spinel, J. Mater. Sci. Lett., Vol 22, 2003, p 755–757
P. Papaicovou, H.J. Grabke, M. Danielewski, and H.P. Schmidt, Conversion of Manganese-Chromium Spinel to Sulphides in H2-H2O-H2S Atmospheres, React. Solids, Vol 8, 1990, p 147–158
S.J. Rothman, The Measurements of Tracer Diffusion Coefficients in Solids, Diffusion in Crystalline Solids, G.E. Murch and A.S. Nowicki, Ed., Academic Press, New York, 1984
J. Gilewicz-Wolter and M. Wolter, Tracer Diffusion of Iron in α-Mn1+yS Polycrystals, Solid State Commun., Vol 117, 2001, p 719–722
I. Kaur and W. Gust, Fundamentals of Grain and Interphase Boundary Diffusion, Ziegler Press, Stuttgart, 1988
N.L. Peterson and W.K. Chen, Cation Self-Diffusion and the Isotope Effect in Mn1-δO, J. Phys. Chem. Solids, Vol 43, 1982, p 29–38
P. Kofstad, High Temperature Corrosion, Elsevier Applied Science, London and New York, 1988