Nanosize β-tantalum coatings: Formation, structure, and properties

Using the methods of ion-plasma sputtering and the coprecipitation of ultradispersed Ta and Cu particles, Ta-Cu film coatings have been obtained in the whole range of concentrations. The structural analysis supports the existence of copper solid solutions in -tantalum in the range of 1.5–82.4 at % Cu. The dynamics of the variation of the β-tantalum lattice parameters with increasing copper concentration is described. A computer simulation model for constructing the unit cell of copper solution in -tantalum is proposed. The resistivity of the samples of Ta-Cu alloys at room and liquid-helium temperatures is measured. The alloy obtained is established to possess a chemical resistance to a full-strength nitric acid up to 66.6 at % Cu. The dependence of the electrochemical potential of Ta-Cu coatings on copper concentration is studied. It is shown that the presence of minima at 73.7 at % Cu fairly well corresponds to acid-resistance threshold and is related to the binding-energy changes and to Cu atoms arrangement in β-Ta lattice upon transition from the tantalum-based solid solutions to the copper-based solutions.