Coatings based on niobium oxides and phosphates formed on niobium alloy

Abstract

Coatings were formed by plasma electrolytic oxidation in electrolytes containing Ni(II) hexametaphosphate complexes. Depending on the n = [P6O 18 6− ]]/[Ni2+] molar ratio in the electrolyte, layers with specific niobium, phosphorus, and nickel contents and of a particular thickness were produced. Upon annealing in air at a temperature of 500 or 800°C, either Nb2O5, or Nb2O5 +NbO(PO4) + P2O5 · 9Nb2O5, or Nb2O5 + NbO(PO4), or Nb2O5 + Ni2P2O7 crystal phases are formed in the coatings depending on the electrolyte composition and temperature of annealing. These surface systems formed on niobium for 10 min at room temperature as a result of a one-stage process in ecologically safe electrolytes can be catalytically active.