Ordered nano-scale dimple pattern formation on a titanium alloy (Ti-6Al-4V)

Abstract

Due to the many applications of nanostructured surfaces – including in biomaterials – there is a strong interest in cost- and time-efficient methods for their fabrication. Previously, our group established a simple electrochemical method generating nanoscale patterns on large areas of a number of different metal surfaces. They consist of dimples that are around 6-10 nm deep and hexagonally closed packed with a tunable periodicity of around 50 nm. Ordering requires careful tuning of the surface chemistry, which makes the translation of these findings to multi-component alloys non-obvious. Here, we demonstrate for the first time that such a pattern can also be achieved on the surface of an alloy, namely Ti-6Al-4V. This alloy is of particular interest for biomedical implants. While dimple formation on the main component metals titanium and aluminum has previously been reported (albeit under conditions that differ from each other), we now also report dimple formation on pure vanadium surfaces to occur under very different conditions. Dimple formation occurs preferentially on the (dominant) α-phase grains of the alloy. The size of dimples of the alloy material is subject to the electropolishing potential, electrolyte concentration and surface chemical composition, which gives us the opportunity to control the surface features. Since a main application of this alloy are biomedical implants, this level of control will be an important tool for accommodating cell growth

Crystallographic Orientation Dependence of Nanopattern Morphology and Size in Electropolished Polycrystalline and Monocrystalline Aluminum: An EBSD and SEM Study

“…1,2 Electropolishing has also been extensively employed to create surface nanopatterns-ordered or quasi-ordered nanostructures such as hexagons and stripes-in various metals such as Zn, 3 Al, [4][5][6] Ti, 7 Ta, 8 and some alloys. 9 Nanopatterned metals have been used for fabrication of high precision diffraction gratings, 10 preparation of ordered anodized oxide films or nanotubes, [11][12][13][14][15] and fabrication of implanted parts with enhanced interfacial adhesion strength. [16][17][18] Nanopatterned aluminum (Al) has been used for preparing ordered anodized aluminum oxide films with controlled morphology; [11][12][13] there were studies demonstrating the potential of nanopatterned Al for quantum-dot based nano-electronic devices.…”

Sponge-Like Porous Metal Surfaces from Anodization in Very Concentrated Acids

“…As the acid concentration is increased, the surface nanostructure becomes rougher, even though at the micrometer scale and above the surface still appears nicely polished. In contrast to some other systems, 24,25 the nanostructures are largely disordered, but appear to have a characteristic lengthscale as a function of voltage and concentration. Even in 97% phosphoric acid, these structures are largely two-dimensional, meaning that they do not protrude further than a few nanometers from the electrode (Fig.…”

“…36 Instability of double layer species ordering in an electric field during electropolishing has been previously considered. 37 An important difference between the porous layer considered in this work and the porous gold layers described recently 26 on one side, and previously described shallow features 24,25,37 on the other side is the height of the features (i.e. the surface corrugation).…”

“…However, it has recently been proven that liquid flow and mass transport do occur parz E-mail: pkruse@mcmaster.ca allel to the surface. 23 Such processes are likely at the root of nanoscale pattern formation during electropolishing, 24,25 although a role of anodic carbon deposits was proposed in the formation of porous gold using oxalic acid. 26 Little to no attention has been paid to the effect of extremely low water concentrations on the surface topography of electropolished copper or other metals.…”

Voltage Dependence of Nanopattern Morphology and Size in Electropolished Monocrystalline Aluminum: An Experimental Study

“…Electropolishing, an electrochemical method for realizing smooth metal surface, 1,2 has been widely used to create ordered or quasiordered surface nanostructures in various metals [3][4][5][6][7][8] or alloys. 9 Studies on formation of nanopatterns on the electropolished polycrystalline Al surface can date back to 1940s. 10 Since then, the effects of electropolishing parameters and material properties (voltage, [11][12][13] temperature, 12,14 time 12 and electrolyte's concentration, 15,16 material impurities, 17,18 annealing 18 ) on nanopattern morphology and size have been studied.…”