Initiation and Growth of Self-Organized TiO[sub 2] Nanotubes Anodically Formed in NH[sub 4]F∕(NH[sub 4])[sub 2]SO[sub 4] Electrolytes

Abstract

The anodic formation of self-organized porous TiO 2 on titanium was investigated in 1 M ͑NH 4 ͒ 2 SO 4 electrolytes containing 0.5 wt % NH 4 F by potential sweeps to 20 V SCE . By a combination of electrochemical, morphological, and compositional information we show that the sweep rate has a significant influence on the initiation and growth of the porous structures. In the first phase of the anodization process, a precursor barrier type of oxide film is formed; underneath this film pores then start growing first randomly and then self-organize. High-aspect-ratio TiO 2 nanostructures can be obtained under optimized electrochemical conditions. These nanotubular oxide layers have single-pore diameter ranging from 90 to 110 nm, average spacing of 150 nm, and porosity in the order of 37-42%. The current work indicates that the nature of the initial barrier-type layer has a strong influence on establishing optimized pore growth conditions.

The influence of surface roughness and high pressure torsion on the growth of anodic titania nanotubes on pure titanium

“…In Figure 5, the value of j from the lowest to the highest are on the CG30-4000, CG30-800 and CG30-14000 samples, respectively, therefore their δ b after Stage I will decrease in that order. The value of t c at the top of TNT layers after the anodization process, also supports this relation (Figure 9), because this capping oxide layer seen at this stage is the penetrated compact oxide layer formed in Stage I [24], therefore the value of t c shows the value of δ b when TNTs started nucleation.…”

“…electrochemical parameters such as potential [18], electrolyte types [19][20][21][22], water content [23] and sweep rates [24]. However, the influence of intrinsic factors, such as surface roughness, surface conditions and grain size and orientation of the titanium substrate are rarely studied [25][26][27][28] and the significant influence of sample preparation methods on TNT growth makes it difficult to study the effects of grain size separately [27,28].…”

The Electrochemical Behavior of Titanium Improved by Nanotubular Oxide Formed by Anodization for Biomaterial Applications: A Review

“…These layers have a limited thickness about 500-600 nm. By taking into account the importance of the pH gradient within the tube 7 , and using buffered neutral electrolytes that containing NaF or NH4F instead of HF, the thickness of the self-organized nanotube titanium oxide layers will increase more than 2 micrometer [61][62][63][64] . The third generation of the nanotubes were grown in (almost) water free electrolytes.…”

Photoelectrochemical properties of N-doped self-organized titania nanotube layers with different thicknesses

“…Recently, we have shown that the tubes can be grown to a length of several micrometers, giving an aspect ratio of a few hundreds. [15][16][17][18][19] This can be achieved by tailored anodization in neutral solutions containing NH 4 F 15-17 or NaF 18 or in glycerol/NH 4 F mixtures. 19 We have already used the nanotubular structures to dye-sensitize them in the visible light 4 or as a catalyst support for methanol electrochemical oxidation, 20 and we have shown how to use ion implantation 21,22 and thermal treatment to N-dope the tubes.…”