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

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.