Structure and growth of beryllium oxide on single crystal of beryllium

Abstract

The nature of the structure and growth of BeO films formed by heating single crystals of beryllium in air over a wide range of temperatures was studied in detail using electron diffraction, and electron microscopy.The epitaxial nature of the oxide formed in the temperature range 300 °C. to 400 °C. on a Be (001) cleavage face was established.In the case of electropolished (001) surfaces of beryllium, it was found that the epitaxial BeO overgrowth was less well-defined. It was suggested that this disorientation was due to the foITnation, during the electropolishing procedure, of surface elements other than (001) upon which the oxide could grow.One-degree (103)-oriented BeO was observed on (100) and (ll0) faces of Be.The oxidation rate increased with increase in temperature, resulting in a corresponding increase in the proportion of randomly-oriented BeO until, above 600 °C., only random growth was observed in the upper regions of the layer. At about 800 °C., a pronounced (001) habit of the randomlyoriented BeO crystals was developed. The diameter of the oxide crystals was estimated from the diffraction patterns to be some tens of ~ngstrSms below 300 °C., and in the order of thousands of _~ngstrSms at about 800 °C.The non-protective nature of the oxide layer formed at 600 °C. and above, is evident from the electron micrographs which showed the development of projecting needles of BeO up to 5/~ in length and several hundred .£mgstrSms in thickness. The needles possessed a ( 110> axis, and possibly grew around screw dislocations. Thin BeO flakes up to several ~ in diameter were also observed in this temperature range, the diffraction pattern indicating considerable distortion of the flake.

Molecular dynamics study of hydrogen isotopes at the Be/BeO interface

“…Both materials have lattices with hexagonal symmetry (hcp for Be and wurtzite for BeO). The experimental study of the growth of BeO on top of Be(0 0 0 1) with electron diffraction and electron microscopy suggests that the first stage of BeO growth is in the ⟨0 0 0 1⟩ direction with ⟨1 0 0 0⟩ of Be and BeO being parallel [30]. Thus, in our study we will first build interfaces between Be(0 0 0 1) and BeO(0 0 0 1) that satisfy these conditions.…”

“…Experiments of BeO growth on Be suggest that at the Be(0 0 0 1)/BeO(0 0 0 1) interface, ⟨1 0 0 0⟩ directions of Be and BeO are parallel [30]. However, there is a mismatch between both lattice constants in this direction: a Be = 2.25-2.32 Å [31] and a BeO = 2.698-2.766 Å [32].…”

Tritium permeation, retention and release properties of beryllium pebbles

“…The growth and properties of whiskers of a great number of metals (including beryllium) have been studied [7,8]. The mechanism of whisker formation on beryllium is still unknown but it is clear that the threads (without the balls) start to grow under oxidation of beryllium in air [8] meaning that the whisker thread growth is a way to form beryllium oxide on the beryllium surface. The typical Table 1 Thickness of beryllium oxide surface layer on beryllium pebbles as a result of the evaluation of the oxygen spectra from Fig.…”

Growth of beryllium oxide nano-structures during thermal treatment of neutron irradiated beryllium

“…Beryllium oxidation below ~1000 °C is believed to follow parabolic rate law, whereas at the temperature beyond this -linear rate law [5]. In early studies of V. D. Scott on beryllium oxidation mechanism few beryllium oxide nano-rods grown around disorders of beryllium lattice were observed [6]. Author suggested that these disorders may take the form of screw dislocations parallel to the axis of the rod.…”