Electron beam irradiation and its use in the fabrication of transition aluminas

Young-Min Kim

Metastable transition aluminas such as χ- and γ-Al₂O₃ of α-alumina have been widely investigated with the viewpoints of materials processing and structure evolution because they are promisingly used as an industry catalysts and precursors for the fabrication of alumina ceramics. By virtue of such studies, efficient processing conditions to synthesis transition phases of α-Al₂O₃ have been well known in a large scale based on thermal processes. Recently, many researchers have devoted themselves to finding a solution for the size control at nanoscale and the desirable polymorph formation among aluminas. New synthetic processes using microwave plasma, electron, and ion beam irradiation techniques as well as thermal decomposition have been proposed for such purposes. As is well known, electron beam induced phenomena are of manifold interests related to radiation damage, crystallization and growth, and deposition because electron beams can be controlled by electromagnetic lenses and are also important in the fabrication of position and size controlled nanomaterials possible as well as to investigate their structures and chemistries. Therefore, among the methods to synthesize transition aluminas, satisfying the current research demands as mentioned above, electron beam irradiation may be a promising technique to fabricate desirable transition alumina at nanoscale. In this study, we focused on quantitative radiation characterization of transition aluminas from gibbsite induced by electron beam irradiation. In doing so, we quantitatively investigated variations of diffraction intensities according to structural changes with imaging plate technique. Furthermore, high-resolution electron microscopy (HREM) was involved in order to comprehend nanocrystallization of transition alumina at atomic level. In particular, our present study may first suggest practical approaches to the selective synthesis of transition alumina from aluminum hydroxide at interested region with electron beam irradiation techniques.