Anodic oxidization of Ti–Ni–Si amorphous alloy ribbons and their capacitive and resistive properties

• Amorphous alloys were anodically polarized using 10 kinds of electrolyte solutions.
• All surfaces of anodically oxidized specimens were amorphous of titanium oxide.
• Usage of F ions in solutions accelerates formation of nanometer-sized pores.
• We report capacitances C and resistances R as a function of pore size.
• We evaluate RC for realization of superior electric storage capacitor.

Amorphous titanium oxide film on Ti–Ni–Si amorphous alloy ribbons was prepared by anodic polarization process in ten kinds of electrolyte solutions. Addition of NH4F in (NH4)2SO4 solution accelerates an increase in current, i.e. formation of soluble Ti-fluoride complexes, resulting in the amorphous titanium oxide layers with nanometer-sized pores. Pore size decreases down to 12 nm with decreasing of applied voltage from 30 to 5 V. However, parallel capacitance Cp, series capacitance Cs, and RCs constant increase with decrease of pore size from 23 to 18 nm and then decrease in pore size region from 18 to 12 nm by formation of penetrating tunnels in the layer. It needs further enhancement of RCs for realization of superior electric storage capacitor.