Core-shell nanoparticles of Fe and Cr prepared by inert gas condensation of plasma evaporated vapor have been investigated by high-resolution transmission electron microscopy (HRTEM). It is found that the thickness of passive oxide film on the surface of Fe and Cr nanoparticles at room temperature are about 4 nm and slightly less than 3 nm respectively. When they are exposed under intense electron beam inside TEM, the thickness of the oxide film increased rapidly to 6 nm for Fe and 4 nm for Cr, in about 30 minutes. It is considered that there is a temperature rise in the nanoparticles due to electron beam heating. The growth of oxide film on Fe and Cr nanoparticles under different electron beam intensity was studied. It showed a linear growth and no growth in oxide film in Fe and Cr nan...[ Read more ]

Core-shell nanoparticles of Fe and Cr prepared by inert gas condensation of plasma evaporated vapor have been investigated by high-resolution transmission electron microscopy (HRTEM). It is found that the thickness of passive oxide film on the surface of Fe and Cr nanoparticles at room temperature are about 4 nm and slightly less than 3 nm respectively. When they are exposed under intense electron beam inside TEM, the thickness of the oxide film increased rapidly to 6 nm for Fe and 4 nm for Cr, in about 30 minutes. It is considered that there is a temperature rise in the nanoparticles due to electron beam heating. The growth of oxide film on Fe and Cr nanoparticles under different electron beam intensity was studied. It showed a linear growth and no growth in oxide film in Fe and Cr nanoparticles when exposed under very strong and very weak electron beam. A logarithmic growth was found in Fe nanoparticles when it was irradiated under medium electron beam intensity. This agreed with Caberra-Mott theory of oxidation. The difference in temperature was investigated using HOLZ line by the technique of convergent beam electron diffraction (CEBD). And it showed that there is a 141°C difference when we using different objective aperture and spot size for exposing the nanoparticles.