Production of films of uranium and americium compounds by thermal decomposition of volatile β-diketonates

Abstract

The production of films containing uranium and americium through thermal decomposition of diketonates and their adducts is described. It is demonstrated that for substrate temperatures in the range 300-400°C and at a residual reactor pressure of 1.3 Pa, stable uranium-containing layers up to several milligrams per square centimetre can be produced, with yields of up to 90%. A variety of metal backings were investigated, including aluminium and its alloys, stainless steel and titanium. Similar results were obtained for americium, but with a strong influence of backing material on the yield. X-ray diffraction identified the chemical form of the uranium deposits as dioxide, with crystal lattice parameters varying from 5.4338 to 5.4871 Å, while the density determined by X-rays lies within the range from 10920 to 11255 kg/m3. In the case of Am (Cm) hexafluoroacetyl acetonate decomposition, the deposit is most probably AmF3 (CmF3). The gases released from the pyrolytic uranium dioxide layers heated in vacuum to 470°C were studied. The volume of gas released varied between 10 and 40 cm3 per gram of UO2 depending on the initial β-diketonate preparation and reagent purity. The released gases were mainly hydrogen, carbon monoxide, carbon dioxide, water and a small amount of methane. The films of uranium and americium obtained by thermal decomposition show good adhesion to backings and are suitable for use in a number of fields, for example in nuclear physics research and instrument engineering. © 2001 Elsevier Science B.V. All rights reserved.