Hot-stage Transmission Electron Microscopy Research Articles

Oxide growth in a AlAl 2O 3 SAP-type alloy by hot stage transmission electron microscopy

The oxidation of an Al-2% A1 2O 3 SAP-type alloy was observed by hot stage transmission electron microscopy, electron diffraction and motion picture micrography. Cold rolled and thinned polycrystalline foils were heated in situ and direct observations of oxide formation, types of oxides formed, modes of growth at different temperatures, growth rates and dynamic interaction with second phase particles were made. As the foil was heated, oxidation occurred at several foil regions. The temperature at which oxidation commenced was sensitive to the amount of cold work introduced in the foil. The oxide formed was not a surface layer but one which extended throughout the entire foil thickness. The Al-oxide interface movement was found to vary as a function of growth geometry, temperature change and second phase particle interaction. The oxidation reaction occurred close to equilibrium conditions and was reversible. Electron diffraction analysis showed the presence of two new types of oxides. Both these oxides could grow as an oriented layer in a (110)〈221〉 fashion. At temperatures approaching the melting point of the matrix aluminum, oxidation occurred on the surface by a spontaneous and irreversible process. At temperatures beyond the melting point of aluminum, there was neither a drastic change in the micro-structure nor any sign of a continuous honeycomb network formation by alumina.

Gas Reactor for Hot Stage Transmission Electron Microscopy

An apparatus is described by which in-microscope gas-specimen reactions are possible without recourse to gas containment or aid of an auxiliary vacuum system. The existing hot stage for the JEM-6A electron microscope in combination with the liquid nitrogen trap normally used with the cooling attachment is converted into a heated stage gas specimen reactor for transmission electron microscopy. The apparatus is described and preliminary results on the controlled oxidation of copper, iron, and nickel metal and the reduction of their oxides are discussed.