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Fabrication of complete titania nanoporous structures via electrochemical anodization of Ti.

Ali G, Chen C, Yoo SH, Kum JM, Cho SO - Nanoscale Res Lett (2011)

Bottom Line: However, a complete titania nano-porous (TNP) structures are obtained when the second anodization is conducted in a viscous electrolyte when compared to the first one.The average pore diameter is approximately 70 nm, while the average inter-pore distance is approximately 130 nm.These TNP structures are useful to fabricate other nanostructure materials and nanodevices.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong, Yuseong, Daejeon 305-701, Republic of Korea. socho@kaist.ac.kr.

ABSTRACT
We present a novel method to fabricate complete and highly oriented anodic titanium oxide (ATO) nano-porous structures with uniform and parallel nanochannels. ATO nano-porous structures are fabricated by anodizing a Ti-foil in two different organic viscous electrolytes at room temperature using a two-step anodizing method. TiO2 nanotubes covered with a few nanometer thin nano-porous layer is produced when the first and the second anodization are carried out in the same electrolyte. However, a complete titania nano-porous (TNP) structures are obtained when the second anodization is conducted in a viscous electrolyte when compared to the first one. TNP structure was attributed to the suppression of F-rich layer dissolution between the cell boundaries in the viscous electrolyte. The structural morphologies were examined by field emission scanning electron microscope. The average pore diameter is approximately 70 nm, while the average inter-pore distance is approximately 130 nm. These TNP structures are useful to fabricate other nanostructure materials and nanodevices.

No MeSH data available.


Related in: MedlinePlus

FESEM images of TNT fabricated in EG containing 0.5 wt% NH4F and 0.2 wt% H2O via single-step anodization for different times: (a) top surface view after 72 h of anodization, (b) top surface view after 11 h of anodization, (c) top surface view after ultrasonic agitation of 20 min in DI H2O, (d) magnified image of the marked area of (c), and (e) top surface view of TNP structure obtained after prolonged anodizing time (72 h) via second-step anodization in glycerol-based electrolyte.
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Figure 7: FESEM images of TNT fabricated in EG containing 0.5 wt% NH4F and 0.2 wt% H2O via single-step anodization for different times: (a) top surface view after 72 h of anodization, (b) top surface view after 11 h of anodization, (c) top surface view after ultrasonic agitation of 20 min in DI H2O, (d) magnified image of the marked area of (c), and (e) top surface view of TNP structure obtained after prolonged anodizing time (72 h) via second-step anodization in glycerol-based electrolyte.

Mentions: In order to study the effect of anodizing time on surface topologies of TNT and TNP structure after the first- and the second-step anodization, a set of experiments were carried at different anodizing times. We found that generally the top surface of TiO2 nanotubes is always covered with some kind of oxide flakes irrespective of the anodizing time. Figure 7a shows the top surface morphology of TNT obtained via the first-step anodization of 72 h in EG-based electrolyte. Formation of nanorods on the top surface of TNT is clearly evident from the image. It is well-known fact that extended anodization time led to the wall thinning of already formed nanotubes at the top surface due to the chemical dissolution. The nanotubes are collapsed and disintegrated at the surface, thus, covering the top of nanotubes. This kind of morphology has been reported in the literature for TNTs [36]. The nanotubes are also buried under the oxide flakes, when the anodization is carried out in the same electrolyte even for a short time (11 h) as shown in the Figure 7b. The oxide clumps (nanorods and flakes) on the surface can be removed with the help of ultrasonication with optimized time duration. It is worth mentioning that severe ultrasonic agitation led to the partial removal of TiO2 nanotubes from the underlying Ti-substrate, as shown in Figure 7c. The partial removal of TiO2 nanotubes might be attributed to the compressive stresses generated in the barrier layer between the nanotubes and the Ti-foil during ultrasonic agitation. The barrier layer has lower mechanical strength as compared to Ti; so compressive stresses in the barrier layer will lead to the partial removal of TiO2 nanotubes from the underlying Ti-substrate. Figure 7d represents the high-magnification image of the marked area in Figure 7c. It is clear that ultrasonic agitation may also produce bundling issues (marked area of Figure 7d). These results suggest that the second anodization is necessary to obtain open tube morphology with a uniform height throughout the entire sample without the bundling problem, which can be used as a template for easy deposition of secondary materials [37]. In order to see the effect of prolonged anodizing time on the pore morphology after the second-step anodization, another experiment on pre-patterned Ti-substrate was performed in glycerol-based electrolyte for 72 h. The top surface morphology of TNP structure obtained after 72 h anodization is shown in Figure 7e without further processing. It is clear from the image that TNP structure is retained even after a prolonged anodizing time and the nanopores are arranged more regularly when compared to a short anodizing time. Thus, prolonged anodizing time improves the pore ordering to a great extent [5]. However, the surface is not very much clean and some debris can be clearly seen in the image. The debris can be removed easily with the help of an optimized ultrasonic agitation.


Fabrication of complete titania nanoporous structures via electrochemical anodization of Ti.

Ali G, Chen C, Yoo SH, Kum JM, Cho SO - Nanoscale Res Lett (2011)

FESEM images of TNT fabricated in EG containing 0.5 wt% NH4F and 0.2 wt% H2O via single-step anodization for different times: (a) top surface view after 72 h of anodization, (b) top surface view after 11 h of anodization, (c) top surface view after ultrasonic agitation of 20 min in DI H2O, (d) magnified image of the marked area of (c), and (e) top surface view of TNP structure obtained after prolonged anodizing time (72 h) via second-step anodization in glycerol-based electrolyte.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211420&req=5

Figure 7: FESEM images of TNT fabricated in EG containing 0.5 wt% NH4F and 0.2 wt% H2O via single-step anodization for different times: (a) top surface view after 72 h of anodization, (b) top surface view after 11 h of anodization, (c) top surface view after ultrasonic agitation of 20 min in DI H2O, (d) magnified image of the marked area of (c), and (e) top surface view of TNP structure obtained after prolonged anodizing time (72 h) via second-step anodization in glycerol-based electrolyte.
Mentions: In order to study the effect of anodizing time on surface topologies of TNT and TNP structure after the first- and the second-step anodization, a set of experiments were carried at different anodizing times. We found that generally the top surface of TiO2 nanotubes is always covered with some kind of oxide flakes irrespective of the anodizing time. Figure 7a shows the top surface morphology of TNT obtained via the first-step anodization of 72 h in EG-based electrolyte. Formation of nanorods on the top surface of TNT is clearly evident from the image. It is well-known fact that extended anodization time led to the wall thinning of already formed nanotubes at the top surface due to the chemical dissolution. The nanotubes are collapsed and disintegrated at the surface, thus, covering the top of nanotubes. This kind of morphology has been reported in the literature for TNTs [36]. The nanotubes are also buried under the oxide flakes, when the anodization is carried out in the same electrolyte even for a short time (11 h) as shown in the Figure 7b. The oxide clumps (nanorods and flakes) on the surface can be removed with the help of ultrasonication with optimized time duration. It is worth mentioning that severe ultrasonic agitation led to the partial removal of TiO2 nanotubes from the underlying Ti-substrate, as shown in Figure 7c. The partial removal of TiO2 nanotubes might be attributed to the compressive stresses generated in the barrier layer between the nanotubes and the Ti-foil during ultrasonic agitation. The barrier layer has lower mechanical strength as compared to Ti; so compressive stresses in the barrier layer will lead to the partial removal of TiO2 nanotubes from the underlying Ti-substrate. Figure 7d represents the high-magnification image of the marked area in Figure 7c. It is clear that ultrasonic agitation may also produce bundling issues (marked area of Figure 7d). These results suggest that the second anodization is necessary to obtain open tube morphology with a uniform height throughout the entire sample without the bundling problem, which can be used as a template for easy deposition of secondary materials [37]. In order to see the effect of prolonged anodizing time on the pore morphology after the second-step anodization, another experiment on pre-patterned Ti-substrate was performed in glycerol-based electrolyte for 72 h. The top surface morphology of TNP structure obtained after 72 h anodization is shown in Figure 7e without further processing. It is clear from the image that TNP structure is retained even after a prolonged anodizing time and the nanopores are arranged more regularly when compared to a short anodizing time. Thus, prolonged anodizing time improves the pore ordering to a great extent [5]. However, the surface is not very much clean and some debris can be clearly seen in the image. The debris can be removed easily with the help of an optimized ultrasonic agitation.

Bottom Line: However, a complete titania nano-porous (TNP) structures are obtained when the second anodization is conducted in a viscous electrolyte when compared to the first one.The average pore diameter is approximately 70 nm, while the average inter-pore distance is approximately 130 nm.These TNP structures are useful to fabricate other nanostructure materials and nanodevices.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology (KAIST), 373-1 Guseong, Yuseong, Daejeon 305-701, Republic of Korea. socho@kaist.ac.kr.

ABSTRACT
We present a novel method to fabricate complete and highly oriented anodic titanium oxide (ATO) nano-porous structures with uniform and parallel nanochannels. ATO nano-porous structures are fabricated by anodizing a Ti-foil in two different organic viscous electrolytes at room temperature using a two-step anodizing method. TiO2 nanotubes covered with a few nanometer thin nano-porous layer is produced when the first and the second anodization are carried out in the same electrolyte. However, a complete titania nano-porous (TNP) structures are obtained when the second anodization is conducted in a viscous electrolyte when compared to the first one. TNP structure was attributed to the suppression of F-rich layer dissolution between the cell boundaries in the viscous electrolyte. The structural morphologies were examined by field emission scanning electron microscope. The average pore diameter is approximately 70 nm, while the average inter-pore distance is approximately 130 nm. These TNP structures are useful to fabricate other nanostructure materials and nanodevices.

No MeSH data available.


Related in: MedlinePlus