Anodizing

About: Anodizing is a research topic. Over the lifetime, 7484 publications have been published within this topic receiving 129577 citations. The topic is also known as: anodized aluminum & anodized.

Titanium oxide nanotube arrays prepared by anodic oxidation

Abstract: Titanium oxide nanotubes were fabricated by anodic oxidation of a pure titanium sheet in an aqueous solution containing 0.5 to 3.5 wt% hydrofluoric acid. These tubes are well aligned and organized into high-density uniform arrays. While the tops of the tubes are open, the bottoms of the tubes are closed, forming a barrier layer structure similar to that of porous alumina. The average tube diameter, ranging in size from 25 to 65 nm, was found to increase with increasing anodizing voltage, while the length of the tube was found independent of anodization time. A possible growth mechanism is presented.

Hexagonal pore arrays with a 50-420 nm interpore distance formed by self-organization in anodic alumina

Abstract: Self-organized hexagonal pore arrays with a 50–420 nm interpore distance in anodic alumina have been obtained by anodizing aluminum in oxalic, sulfuric, and phosphoric acid solutions. Hexagonally ordered pore arrays with distances as large as 420 nm were obtained under a constant anodic potential in phosphoric acid. By comparison of the ordered pore formation in the three types of electrolyte, it was found that the ordered pore arrays show a polycrystalline structure of a few micrometers in size. The interpore distance increases linearly with anodic potential, and the relationship obtained from disordered porous anodic alumina also fits for periodic pore arrangements. The best ordered periodic arrangements are observed when the volume expansion of the aluminum during oxidation is about 1.4 which is independent of the electrolyte. The formation mechanism of ordered arrays is consistent with a previously proposed mechanical stress model, i.e., the repulsive forces between neighboring pores at the metal/oxide interface promote the formation of hexagonally ordered pores during the oxidation process.

Self-organized formation of hexagonal pore arrays in anodic alumina

Abstract: The conditions for the self-organized formation of ordered hexagonal structures in anodic alumina were investigated for both oxalic and sulfuric acid as an electrolyte. Highly ordered pore arrays were obtained for oxidation in both acids. The size of the ordered domains depends strongly on the anodizing voltage. This effect is correlated with a voltage dependence of the volume expansion of the aluminum during oxidation and the current efficiency for oxide formation. The resulting mechanical stress at the metal/oxide interface is proposed to cause repulsive forces between the neighboring pores which promote the formation of ordered hexagonal pore arrays.

Titanium and Titanium Alloys

Abstract: The chapter discusses various methods used to treat titanium and titanium alloys for adhesive bonding. It is reported that both alkaline cleaning and phosphate-fluoride prebond treatments produce surfaces of good wettability, equal thickness and similar composition. Stabilized phosphate-fluoride process retards the conversion of anatase to rutile. It is also reported that the anodic process produces a porous oxide structure and is superior to the surface formed by the phosphate-fluoride process. Specific treatments for aluminum and aluminum alloys are presented in a process specification format including anodize process, Turco 5578, liquid hone/Pasa-Jell 107 process, dry hone/Pasa-Jell 107 process, alkaline peroxide process and stabilized phosphate-fluoride process. A study of the morphology and decomposition of the various surfaces revealed that different surface morphologies are obtained with the different treatments. The treatments were classified into three different groups. The Group I processes were characterized as producing surfaces which have thin oxide layers with little macro-roughness while Group II processes resulted in surfaces which had a high degree of macro-roughness. The Group III processes produced surfaces which were characterized by a primarily micro-rough porous oxide.

Structure and physicochemistry of anodic oxide films on titanium and TA6V alloy

Abstract: Anodization of titanium and its alloys is an important surface treatment, especially for adhesion applications, but is not as well studied as for aluminium alloys. This paper deals with the morphological, structural and physicochemical characterization of anodic oxide films grown on titanium and Ti–6Al–4V (TA6V) in chromic acid solution without (CA) or with (CA/HF) hydrofluoric acid addition. Several investigations methods are used: high-resolution scanning electron microscopy (HR-SEM), reflection high-energy electron diffraction (RHEED), x-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), nuclear reaction analysis (NRA) and wetting angle measurements. The occurrence and morphology of the nanoporous structure for CA/HF anodization are described. The compact films grown in CA solution are amorphous and the porous films grown in the CA/HF solution are partially crystalline. The thickness and morphology of the films are described and discussed as a function of the anodizing conditions and of the composition of the underlying substrate. The composition of the film appears to be TiO2+Al2O3 (with Ti/Al atomic ratio ∽5), with incorporation of fluorine from the solution in the porous films and of small quantities of vanadium in the films that are grown. The specific role played by the Cr(VI) and F species on the film growth-and-dissolution formation process is discussed and a growth mechanism is proposed. Copyright © 1999 John Wiley & Sons, Ltd.