Cylindrical TiO2nanotubes and hexagonal TiO2nanotubes were obtained in the anodizing process of titanium in fluoride-containing electrolyte. Based on the experimental findings and viscous flow model, a mechanism of self-ordering process of hexagonal cells arrangement for porous anodic TiO2nanotubes (PATNT) is proposed in this paper. The analysis results show that oxygen evolution in the pore bottoms plays an important role in the self-ordering process. Oxide grows around the oxygen bubbles in the pore bottoms, which results in the formation of cylindrical TiO2nanotubes. Volume expansion of TiO2takes place during the anodizing process. Plastic deformation and repulsive force caused by volume expansion are responsible for self-ordering process of PATNT hexagonal cells.

To overcome the risk of electrolyte leakage and the shortcoming of higher impedance at high frequencies for the conventional aluminum electrolytic capacitor impregnated with electrolyte solutions, solid aluminum electrolytic capacitor employing conducting polyaniline (PANI) as a counter electrode was developed. The as-fabricated solid capacitors have very low impedances at high frequencies and excellent thermal stability. The superior performances can be ascribed to high conductivity and good thermal stability of the camphorsulfonic acid (CSA)-dodecylbenzenesulfonic acid (DBSA) co-doped PANI.

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A convincing interpretation to hexagonal prism ordered-arrangement and self-ordering cell in porous anodic alumina (PAA) is absent up to now. Based on the growth model of oxygen bubble mould effect (OBME) for PAA, a satisfactory explanation for the growth process of hexagonal cells is proposed. The columnar pores and hexagonal cells result from the oxide growth embracing oxygen bubbles. The avalanche electron multiplication at critical thickness dc leads to electronic current which gives rise to the evolution of oxygen gas under anion-contaminated alumina (ACA) layer. The holes on the surface are usually irregular whereas the pores under the surface layer (ACA layer) are big and regular. The thickness of the barrier oxide layer remains constant due to continuous releasing of the oxygen bubbles at the critical thickness. The self-ordering of cell arrangement and the ordered morphology are related to the dissolving process of the ACA layer on PAA surface.

The electrochemical performance of polyaniline (PANI)/stainless steel electrodes prepared in H2SO4 and p-toluene sulfonic acid (p-TSA) using potentiodynamic method were investigated in corresponding acids and three kinds of sodium salts, respectively, by cyclic voltammetry, galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy (EIS). It is concluded that the counter anion of acid employed in the electropolymerization plays a key role in the free volume of PANI. The kinetic parameters of PANI are strongly influenced by the free volume both in acid and in salt solutions. In addition, the utilizing of salt solution is beneficial to the kinetic analysis of the energy-storage process of PANI, although the capacitance of PANI in salt solution decays on cycling due to the lack of protons.