In situ investigation of aluminum oxide under irradiation by electron beam at atomic-scale

Abstract

It has yet to be experimentally proven whether the native aluminum oxide layer can still effectively protect pure aluminum from further degradation under an irradiation environment. Here, we directly investigate the microstructure evolution of amorphous Al2O3 in real time by using an electron beam as an irradiation source with in-situ transmission electron microscopy (TEM). At the atomic scale, crystalline Al2O3 grains were found to nucleate and grow along amorphous substrate. With continuous irradiation, both amorphous and newly formed crystalline Al2O3 were removed completely, and then the internal fresh aluminum was exposed. By regulating electrons, new oxides quickly formed on the fresh metal surface and merged with adjacent old oxides, finally leaving a uniform amorphous oxide protection layer. Our work provides experimental evidence for understanding the protection mechanism for the oxide layer on its internal metal under a special service environment.