Preparation and Characterization of Microporous Layers on Titanium

Abstract

Microporous layers on titanium (Ti) are formed by chemical treatment in highly concentrated alkaline media, and their properties and growth mechanism are examined using electrochemical techniques, in situ resistometry, scanning electron microscopy (SEM), grazing-incident X-ray diffraction (GIXRD), and glow discharge optical emission spectroscopy (GD-OES). Chemical treatment in a 5 M aqueous KOH solution yields results superior to those from the same treatment in a 5 M aqueous NaOH solution, while a 3 M aqueous LiOH solution does not produce porous layers. The cation constituting the solution plays a vital role in the process. An SEM analysis reveals that the KOH solution is the most effective in forming microporosity and that the longer the treatment time, the more porous the near-surface layer. The results of GIXRD analysis show the presence of Na(2)Ti(5)O(11) and K(2)Ti(6)O(13) in the layers formed in the NaOH and KOH solutions, respectively; in the case of the LiOH solution, TiO(2) is formed. Chemical treatment in the NaOH and KOH solutions resembles a general corrosion process with the existence of local cathodic and anodic sites. The reduction reaction produces H(2), some of which becomes absorbed in the near-surface region of Ti, while the oxidation reaction produces the above-mentioned compounds and/or an oxide layer. The presence of hydrogen (H) within the solid is detected using GD-OES. The H-containing near-surface layer partially dissolves, yielding a microporous structure. The development and dissolution of the H-containing near-surface layer of Ti upon chemical treatment in the NaOH and KOH solutions are confirmed by resistometry measurements. They point to the formation of a compact passive layer on Ti upon exposure to the LiOH solution.

Alkali Metal Cation Incorporation in Conductive TiO2 Nanoflakes with Improved Photoelectrochemical H2 Generation

“…Additionally, similar results on the effect of ionic radius in hydrothermal reactions using NaOH and KOH were reported. Moreover, Tanaka et al., compared the electrochemical properties of Ti wires which were chemically treated by immersion in highly concentrated alkaline media . The authors showed that chemical treatment in NaOH and KOH solutions resembles a general corrosion process.…”

“…There are a vast number of reports on the preparation of TiO 2 ‐based nanostructures with controllable morphologies that can be produced by the hydrothermal method . Generally, the reported works on hydrothermal growth of TiO 2 on Ti foil have focused on the morphology and electrochemical properties of TiO 2 nanostructured films, but there are only a few studies on the influence of different hydrothermal alkaline solutions on the TiO 2 photoelectrochemical properties. For instance, Sikhwivhilu et al .…”

Comparison of titanium soaked in 5M NaOH or 5M KOH solutions

“…Tanaka et al . [29] only compared the surface topography of Ti specimens after their immersion in 5 M NaOH and 5 M KOH solutions at 80°C for 1, 6, 12 and 20 h. However, wettability (by using contact angle goniometry) of NaOH- or KOH-treated titanium surfaces has never been reported.…”

Alkaline phosphatase levels of murine pre-osteoblastic cells on anodized and annealed titanium surfaces

“…Tas and Bhaduri (26) were the first to soak Ti sheets in a 5 M KOH solution at 60°C for 24 h and 600°C heating for 1 h in air, followed by coating these alkali-modified surfaces with an apatitic calcium phosphate layer by using a supersaturated SBF. The microporous layer formed in the 5 M KOH solution were found to develop faster and thicker under anodization with superior to the analogous layer prepared in the 5 M NaOH solution by Tanaka et al (27). Cai et al (21) applied alkali treatment with immersion of cpTi discs into KOH solutions at concentrations of 4, 6, 8, and 10 M at 600°C for 24h followed by heat treatment at 600°C for 1h.…”