Abstract
We report a single-step anodic dissolution route for the template-free patterning of pure titanium (Ti) surfaces into a microscale, dimpled topography using non-aqueous ethylene glycol-TiCl4 electrolytes. Anodic dissolution of Ti metal (i.e. 0.04 M Ti4+) into a 40 EG:1 TiCl4 electrolyte was found to induce a predominant change in the anodic dissolution reaction of Ti metal, converting its surface morphology from a slightly-pitted, bright finish into a dimple-patterned surface. The dimple pattern, ca. 4.5 μm in size and 1 μm in cusp height, was found self-organised with no apparent relation to underlying metal grain structure and independent of the applied potential within the anodic current plateau. The origin of the dimple pattern is surmised to arise from a dynamic self-organisation of the anode film, resulting in a Turing structure.
Highlights
The surface patterning of titanium (Ti) metal and its alloys has received increased attention driven by a need for tailoring surface topographical characteristics to suit specific application requirements [1,2]
To reach the concentration of anodically dissolved Ti4+ ions in the electrolyte which triggered the formation of dimple pattern, a number of individual potentiostatic trials were conducted at 30 V at 20 ◦C for 300 s on the Ti substrates, instead of a continuous, prolonged anodic dissolution trial which otherwise would cause excessive Joule heating and electrodereaction-induced thermal explosion
A single-step, template-free and low-cost anodic dissolution route for the patterning of pure titanium surfaces to create microscale dimpled morphology has been developed from non-aqueous ethylene glycolTiCl4 electrolytes
Summary
The surface patterning of titanium (Ti) metal and its alloys has received increased attention driven by a need for tailoring surface topographical characteristics to suit specific application requirements [1,2]. Various surface texture patterning and functionalisation strategies that have been reported for Ti and its alloys exploit physical and/or wet chemistry routes to modify the substrate surface, in either an additive or subtractive manner, to manipulate the patterns through varying feature size, shape, and roughness profile: e.g. reactive ion etching [9], nanoimprint lithography [9] electrochemical micromachining [10], block copolymer template [11] and direct laser patterning [8,12] These patterning methods entail the application of a resolution-limiting template and/or necessitate line of sight, often in multiple steps of treatment, or require an inert atmo sphere during processing given the high affinity of Ti to oxygen [8,9,12]. The effect of electrolysis conditions, including the nonaqueous EG-TiCl4 electrolyte chemistry, electrolysis potential and time, Ti substrate microstructure and subsequent pattern obtained were examined (using SEM/EDX, Plasma-FIB, EBSD, XPS, white light inter ferometry tools) to determine the mechanism by which the dimple pattern is achieved
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