Dielectric properties of anodic films on sputter-deposited Ti–Si porous columnar films

Abstract

For electrolytic capacitor application of the single-phase Ti alloys containing supersaturated silicon, which form anodic oxide films with superior dielectric properties, porous Ti-7 at% Si columnar films, as well as Ti columnar films, have been prepared by oblique angle magnetron sputtering on to aluminum substrate with a concave cell structure to enhance the surface area and hence capacitance. The deposited films of both Ti and Ti-7at% Si have isolated columnar morphology with each column revealing nanogranular texture. The distances between columns are ~500 nm, corresponding to the cell size of the textured substrate and the gaps between columns are 100 -200 nm. When the porous Ti-7 at% Si film is anodized at a constant current density in ammonium pentaborate electrolyte, the growth of a uniform amorphous oxide film continues to ~35 V, while it is limited to less than 6 V on the porous Ti film. The maximum voltage of the growth of uniform amorphous oxide films on the Ti-7 at% Si films is similar for 2 both the flat and porous columnar films, suggesting little influence of surface roughness on the amorphous-to-crystalline transition of growing anodic oxide under the high electric field. Due to the suppression of crystallization to sufficiently high voltages, the anodic oxide films formed on the porous Ti-7 at% Si film shows markedly improved dielectric properties, in comparison with those on the porous Ti film.

Effects of Fe doping on preparation of Ti-Si porous membrane via in-situ reactive process

“…Cao Yingwen [27] successfully assembled a novel loop heat pipe (LHP) with the bi-porous quaternary Ti3(Al, Si)C2 wick synthesized by vacuum sintering, and a better strength and lower thermal conductivity were obtained than that of conventional nickel wicks. Via oblique angle magnetron sputtering, H. Habazaki [28] have prepared porous Ti-7 at.% Si columnar film on the aluminum substrate with a concave cell structure to enhance the surface area and hence capacitance, which markedly improved dielectric properties in comparison with those on the porous Ti film. Cheng Jiaxu [29] synthesized TiSi2/Si nanocomposite by the aid of electrolyzing SiO2/TiO2 in molten salts, and proved it exhibiting an excellent lithiation stability and enhancing the lithium-storage electrochemical performance.…”