The role of the Ti surface roughness in the self-ordering of TiO<sub>2</sub> nanotubes: a detailed study of the growth mechanism

Apolinário, Arlete; Sousa, C. T.; Ventura, J.; Costa, J. D.; Leitao, Diana C.; Moreira, J. Agostinho; Sousa, J. B.; Andrade, Luísa; Mendes, Adélio; Araújo, João P.

doi:10.1039/c4ta00871e

Cited by 57 publications

(70 citation statements)

References 56 publications

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“…1 x 1 µm 2 topographic images of Ti surfaces were obtained for each sample and then analyzed in terms of surface roughness (Rq), defined as the root-mean-square value of the images pixel height. Additionally, the Ti surface after EP revealed a periodic dimple-pattern structure whenever VEP was no smaller than 10 V. This shallow ripple-like structure is an EP characteristic of metals [33,41] and can be used as a pre-pattern prior to the anodization to obtain highly ordered oxide nanostructures, as profusely shown in the case of Al [27,[33][34][35][36]40]. In fact, studies in Al foils demonstrated that, by combining adequate EP voltage and time, dimple-patterns from striped to hexagonal arrangements can be obtained [27,[33][34][35][36]40].…”

Section: Afm Imaging Analyses: Surface Topography and Roughness Charamentioning

confidence: 96%

“…After applying the anodization potential (60 V), a continuous TiO2 layer is rapidly formed increasing the resistance (rapid j decrease). The following slight j-decrease marks the onset of NT nucleation, likely on the surface valley-type irregularities where the higher electric field enhances oxide dissolution and hole formation (dissolution promoted by F -ions in favourable spots of the TiO2 surface) [41]. Consequently, the TiO2 layer thickness starts to decrease, while the pores (tubes) formation accelerates.…”

Section: Anodization Curves 121 Typical Growth Mechanismmentioning

confidence: 99%

“…Prior to the anodization, the pieces of the as-rolled Ti foil were pre-treated by an EP in a H2SO4/HF (8:3) solution, under applied potentials (VEP) between the Ti foil and an inert Pt mesh (at a distance of 2.5 cm) for 4 min. Several samples were fabricated with different VEP of 5, 10, 15, 18 and 20 V; the solution was mechanically stirred (300 rpm) and kept at room temperature [33,41]. The Ti surfaces of all electropolished samples, as well as an as-rolled Ti sample, were analyzed using a Nanoscope Multimode Atomic Force Microscope from Veeco Instruments.…”

Section: Methodsmentioning

confidence: 99%

“…However, EP of Ti is usually performed in sulphuric acid-based electrolytes that leads to smooth and plane surfaces [31]. Nonetheless, EP with HF-electrolytes can also result in organized dimple patterns under certain conditions (time, temperature, voltage) [33,41].…”

Section: Afm Imaging Analyses: Surface Topography and Roughness Charamentioning

confidence: 99%

“…The evaluation of the mechanisms that lead to the formation and growth of the NTs can be studied using current density (j) curves [41]. For the samples AR, 5 V and 10 V, these curves present the typical behaviour for Ti anodization and the successful formation of TiO2 nanotubes (Fig.…”

Section: Anodization Curves 121 Typical Growth Mechanismmentioning

confidence: 99%

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Tailoring the Ti surface via electropolishing nanopatterning as a route to obtain highly ordered TiO₂nanotubes

et al. 2014

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Abstract. Highly-ordered TiO2 nanotubes (NTs) were synthesized by the electrochemical anodization of Ti foils subjected to electropolishing (EP) pre-treatment. We found that the Ti surface roughness plays an important role in the onset of pore nucleation in enhancing the local focusing effect of the electrical field. Additionally, EP induces the formation of dimple structures on the metal surface, which can work as a pre-pattern prior to the anodization. These shallow ripples lead to a preferential ordered pore nucleation, offering an organization improvement of the anodic oxide NTs. We found that, depending on the EP applied potential, the roughness and the spacial period of the ripple-like structures varies from 8 to 2 nm and from 122 to 30 nm, respectively. Such tuning allowed us to focus on the influence of the initial Ti pre-surface topography features on the NTs length, organization and hexagonal arrangement quality, NTs diameter and density. Our results show that an EP under 10 V is the most suitable to obtain a small Ti surface roughness, the largest NT length (40% enhancement) and the effective improvement of the ordered hexagonal NTs arrays over larger areas. Furthermore, the NTs dimensions (pore diameters and density) were found to also depend on the initial Ti surface topography. The use of optimized EP allows to obtain highly hexagonal self-ordered samples at a reduced time and cost. IntroductionThe electrochemical anodization of Ti to obtain highly-ordered nanotube (NT) arrays of TiO2 continues to gain an increasing importance for a large number of applications, such as photoelectrochemical cells for H2 production (water splitting) [1,2] and particularly for dye-sensitized solar cells (DSCs) [2]. TiO2 NTs have received great attention due to their one dimensional structure which provides a direct and efficient path for electrons [1].TiO2 NTs can be obtained by the electrochemical anodization of Ti in fluoride-based electrolytes. The addition of ethylene glycol was later found to lead to longer (hundreds of microns) and more ordered arrays of TiO2 NTs [3][4][5][6][7][8][9]. Differently from the well-known case of Al anodization, the Ti anodization presents a non-steady state, due to the out of equilibrium dissolution and oxidation processes on the NT bottom and to the additional chemical dissolution process at the NTs top [5,[10][11][12][13][14]. This unbalanced anodization leads to a maximum TiO2 NTs length, after a given anodizing time. Besides the length, other NT parameters are influenced by factors such as the electrolyte type (e.g. electrolyte concentration and pH), anodization temperature and applied potential [3][4][5][6][7][8][9][10][15][16][17][18].Aiming a degree of order comparable to that of anodic alumina oxide (AAO) at 10 % porosity [19], intense research has been performed on the organization and final ordering of TiO2 NTs in a closed-

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Section: Afm Imaging Analyses: Surface Topography and Roughness Charamentioning

confidence: 96%

Section: Anodization Curves 121 Typical Growth Mechanismmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Afm Imaging Analyses: Surface Topography and Roughness Charamentioning

confidence: 99%

Section: Anodization Curves 121 Typical Growth Mechanismmentioning

confidence: 99%

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Tailoring the Ti surface via electropolishing nanopatterning as a route to obtain highly ordered TiO₂nanotubes

et al. 2014

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Homogeneous Anodic TiO₂ Nanotube Layers on Ti–6Al–4V Alloy with Improved Adhesion Strength and Corrosion Resistance

Gao

et al. 2019

Adv Materials Inter

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and superior properties, which are cost-effective [1] and found many applications in photocatalytic devices, [2,3] electronic devices, [4] solar cells, [5] sensors, [6] as well as biomedical implants. [7,8] As coatings on biomedical implants, TNT layers have been reported to affect the cellular behavior such as adhesion, [9] migration, [7] proliferation, [7,10] and differentiation. [11] Nevertheless, TNT coatings are normally deposited on pure titanium substrates rather than Ti alloys because TNT layers fabricated on Ti alloys are usually inhomogeneous. Most Ti alloys used in biomedical applications have a binary-phase α/β microstructure, [12] of which the α phase has a hexagonal close-packed crystallographic structure containing α-stabilizing elements like Al, O, and N, whereas the β phase with a body-centered cubic structure is enriched with β-stabilizing elements such as Nb, V, Mo, Ta, and Zr. [13] It is difficult to produce uniform nanotube arrays on multiple-phase substrates due to the diverse chemical reactivities of different phases. For example, one phase can be oxidized or etched preferentially by the electrolyte, [14] and hence the nanotube layers formed on Hexagonal TiO 2 nanotubes (TNTs) arrays are generally fabricated on Ti-based substrates for some biomedical purposes, but the TNT layers constructed on conventionally processed Ti alloys are usually inhomogeneous because the substrates typically contain both the α and β phases. In this work, high-pressure torsion (HPT) is applied to obtain a saturated single α-phase microstructure in Ti-6Al-4V alloys via strain-induced β phase dissolution. Homogeneous anodic TNT layers with three different morphologies, one-step nanoporous, one-step nanotubular, and two-step nanoporous structures, are electrochemically fabricated on the ultrafine-grained (UFG) Ti-6Al-4V alloy substrates after HPT processing, whereas the TNT layers prepared on coarsegrained substrates are normally inhomogeneous. More notably, the TNT layers show significantly improved adhesion strength to the UFG substrate as well as better corrosion resistance compared to those on the conventionally processed Ti-6Al-4V substrates. X-ray diffraction analysis, scanning electron microscopy in combination with electron backscatter diffraction, and transmission electron microscopy indicate that the improvement is due to a larger dislocation density in the UFG substrate as well as strain-induced β phase dissolution.

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Combined Infection Control and Enhanced Osteogenic Differentiation Capacity on Additive Manufactured Ti‐6Al‐4V are Mediated via Titania Nanotube Delivery of Novel Biofilm Inhibitors

Mutreja

Hooper

et al. 2020

Adv Materials Inter

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Additive manufacturing (AM) of titanium alloys offers the capacity to fabricate patient-specific implants with defined porous architecture to enhance bone-implant fixation. However, clinical challenges associated with orthopedic implants include inconsistent osseointegration and biofilm-associated peri-implant infection, leading to implant failure. Here, a strategy is developed to reduce infection and promote osteogenesis simultaneously on AM Ti-6Al-4V implants by delivering biofilm inhibitor molecules via titania nanotube surface modification. Electrochemical anodization is performed on polished and as-manufactured Ti-6Al-4V to generate nanotubes, which are utilized for delivery of a novel methylthioadenosine nucleosidase inhibitor (MTANi) that targets MTAN-a key enzyme in bacterial metabolism involved in biofilm formation-thereby offering biofilm inhibition capacity combined with surface nano-topography for promoting osteogenesis. Clinical isolates of staphylococcus cohnii formed firm biofilms on polished and AM Ti-6Al-4V controls whereas modified implants loaded with MTANi inhibit biofilm formation. Anodized AM Ti-6Al-4V nanotube substrates enhance alkaline phosphatase production, bone-specific protein expression (osteocalcin, collagen I) and mineral deposition of human mesenchymal stromal cells (hMSCs), compared to as-manufactured controls. Importantly, no detrimental effects on hMSC proliferation and osteogenic differentiation are observed for MTANi-loaded substrates. Application of novel MTANi and electrochemical anodization offers a promising strategy for titanium alloy implant surface modification.

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The role of the Ti surface roughness in the self-ordering of TiO₂ nanotubes: a detailed study of the growth mechanism

Cited by 57 publications

References 56 publications

Tailoring the Ti surface via electropolishing nanopatterning as a route to obtain highly ordered TiO₂nanotubes

Tailoring the Ti surface via electropolishing nanopatterning as a route to obtain highly ordered TiO₂nanotubes

Homogeneous Anodic TiO₂ Nanotube Layers on Ti–6Al–4V Alloy with Improved Adhesion Strength and Corrosion Resistance

Combined Infection Control and Enhanced Osteogenic Differentiation Capacity on Additive Manufactured Ti‐6Al‐4V are Mediated via Titania Nanotube Delivery of Novel Biofilm Inhibitors

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The role of the Ti surface roughness in the self-ordering of TiO2 nanotubes: a detailed study of the growth mechanism

Cited by 57 publications

References 56 publications

Tailoring the Ti surface via electropolishing nanopatterning as a route to obtain highly ordered TiO2nanotubes

Tailoring the Ti surface via electropolishing nanopatterning as a route to obtain highly ordered TiO2nanotubes

Homogeneous Anodic TiO2 Nanotube Layers on Ti–6Al–4V Alloy with Improved Adhesion Strength and Corrosion Resistance

Combined Infection Control and Enhanced Osteogenic Differentiation Capacity on Additive Manufactured Ti‐6Al‐4V are Mediated via Titania Nanotube Delivery of Novel Biofilm Inhibitors

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Resources

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The role of the Ti surface roughness in the self-ordering of TiO₂ nanotubes: a detailed study of the growth mechanism

Tailoring the Ti surface via electropolishing nanopatterning as a route to obtain highly ordered TiO₂nanotubes

Tailoring the Ti surface via electropolishing nanopatterning as a route to obtain highly ordered TiO₂nanotubes

Homogeneous Anodic TiO₂ Nanotube Layers on Ti–6Al–4V Alloy with Improved Adhesion Strength and Corrosion Resistance