Formation and structure of anodic films on beryllium

The present, as well as previous, work on the anodizing of Be confirms that most electrolytes yield films characterized by one or more of being porous, being subject to extensive dissolution, or being crystalline. This includes electrolytes based on the following: aqueous KOH, a CrO3-HNO3 mixture, aqueous Na2CO3, (C2H5)2HPO4, a (C2H5)2SO4-H2SO4 mixture, acetic acid. Significantly different results are obtained with ethylene glycol which is saturated with Na2HPO4 or KH2PO4 or both Na2HPO4 and Na2SO4. The films are then nonporous, as shown by scanning electron microscopy. They are formed with negligible dissolution, as follows by implanting the Be with 30-keV 85Kr before anodizing and noting the loss of activity during anodizing. They are nominally amorphous, as inferred by reflection electron diffraction, though crystallize to hexagonal BeO at a temperature lying somewhere below 3000C. (auth)