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Fabrication of Ni-Ti-O nanotube arrays by anodization of NiTi alloy and their potential applications.

Hang R, Liu Y, Zhao L, Gao A, Bai L, Huang X, Zhang X, Tang B, Chu PK - Sci Rep (2014)

Bottom Line: In the present work, we systemically investigated the influence of various anodization parameters on the formation and structure of Ni-Ti-O NTAs and their potential applications.Our results show that well controlled NTAs can be fabricated during relatively wide ranges of the anodization voltage (5-90 V), electrolyte temperature (10-50°C) and electrolyte NH4F content (0.025-0.8 wt%) but within a narrow window of the electrolyte H2O content (0.0-1.0 vol%).Through modulating these parameters, the Ni-Ti-O NTAs with different diameter (15-70 nm) and length (45-1320 nm) can be produced in a controlled manner.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Surface Engineering, Taiyuan University of Technology No. 79 Yingze West Road, Taiyuan 030024, China.

ABSTRACT
Nickel-titanium-oxide (Ni-Ti-O) nanotube arrays (NTAs) prepared on nearly equiatomic NiTi alloy shall have broad application potential such as for energy storage and biomedicine, but their precise structure control is a great challenge because of the high content of alloying element of Ni, a non-valve metal that cannot form a compact electronic insulating passive layer when anodized. In the present work, we systemically investigated the influence of various anodization parameters on the formation and structure of Ni-Ti-O NTAs and their potential applications. Our results show that well controlled NTAs can be fabricated during relatively wide ranges of the anodization voltage (5-90 V), electrolyte temperature (10-50°C) and electrolyte NH4F content (0.025-0.8 wt%) but within a narrow window of the electrolyte H2O content (0.0-1.0 vol%). Through modulating these parameters, the Ni-Ti-O NTAs with different diameter (15-70 nm) and length (45-1320 nm) can be produced in a controlled manner. Regarding potential applications, the Ni-Ti-O NTAs may be used as electrodes for electrochemical energy storage and non-enzymic glucose detection, and may constitute nanoscaled biofunctional coating to improve the biological performance of NiTi based biomedical implants.

No MeSH data available.


Related in: MedlinePlus

Surface FE-SEM images of the Ni-Ti-O NTAs formed in ethylene glycol containing 0.2 wt% NH4F and 1.0 vol% H2O at 30°C at different anodization voltages.(a) 5 V, (b) 10 V, (c) 15 V, (d) 20 V, (e) 25 V, (f) 30 V, (g) 40 V, (h) 60 V, and (i) 90 V. The anodization durations at different voltages are 12, 6, 6, 4, 1, 0.5, 0.5, 0.25, and 0.25 h, respectively, to reach their balanced (maximum) nanotube length. Variation in the diameter and length of the NTs as a function of anodization voltage (j).
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f1: Surface FE-SEM images of the Ni-Ti-O NTAs formed in ethylene glycol containing 0.2 wt% NH4F and 1.0 vol% H2O at 30°C at different anodization voltages.(a) 5 V, (b) 10 V, (c) 15 V, (d) 20 V, (e) 25 V, (f) 30 V, (g) 40 V, (h) 60 V, and (i) 90 V. The anodization durations at different voltages are 12, 6, 6, 4, 1, 0.5, 0.5, 0.25, and 0.25 h, respectively, to reach their balanced (maximum) nanotube length. Variation in the diameter and length of the NTs as a function of anodization voltage (j).

Mentions: The effect of the anodization voltage on the structure of Ni-Ti-O NTAs is shown in Figure 1. The samples are fabricated by anodization in an ethylene glycol solution containing 0.2 wt% NH4F and 1.0 vol% H2O at 30°C. At a low voltage of 5 V, nanotubes (NTs) with a small diameter of about 15 nm are observed. Increasing the voltage from 10 to 25 V results in a linear increase in the NT diameter to 70 nm at 25 V. The NT diameter remains the same in the voltage range of 25-40 V and further voltage increase leads to a slight decrease in the NT diameter to 65 and 60 nm at 60 and 90 V, respectively. The variation in the NT length versus anodization voltage shows a similar trend as that of the diameter, with the largest length of about 1100 nm generated at 25 V. When the voltage exceeds 25 V, evenly distributed micropits occur (Figure S1f-i). The entire surface of micropits is covered by NTAs, but the diameter and length are smaller than those outside the micropits (Figure S2). The elemental composition inside and outside the micropits shows no obvious difference as evidenced by Energy dispersive spectroscopy (EDS) elemental mapping (Figure S3). The variation of current during anodization is similar to that of pure Ti, but its steady-state value is higher. When the voltage exceeds 25 V, current fluctuation in the steady-state phase during the anodization process can be observed (Figure S4a). It is generally accepted that a larger voltage leads to increased NT diameter and length in anodization of pure Ti29, but in case of NiTi alloy, this rule no longer applies when the voltage exceeds 25 V. The deviation may be explained by runaway anodization at an elevated voltage, namely current self-amplification resulting from the resistance heating effect. The resistance heating effect elevates the temperature, which on the one hand accelerates oxide dissolution reducing the NT diameter and length, but on the other hand promotes the formation of electrochemical active sites on the sample surface causing local thinning, breakdown of the oxide film, and formation of micropits30. The micropits act as short-circuit channels to increase the current further heating the sample. After initiation, the micropits will proliferate in both depth and width (Figure S5). At the same time, hydrolysis of metal cations such as Ti4+ and Ni2+ enriched in the micropits reduces the local pH thus accelerating oxide dissolution and decreasing the NT length and diameter in the micropits.


Fabrication of Ni-Ti-O nanotube arrays by anodization of NiTi alloy and their potential applications.

Hang R, Liu Y, Zhao L, Gao A, Bai L, Huang X, Zhang X, Tang B, Chu PK - Sci Rep (2014)

Surface FE-SEM images of the Ni-Ti-O NTAs formed in ethylene glycol containing 0.2 wt% NH4F and 1.0 vol% H2O at 30°C at different anodization voltages.(a) 5 V, (b) 10 V, (c) 15 V, (d) 20 V, (e) 25 V, (f) 30 V, (g) 40 V, (h) 60 V, and (i) 90 V. The anodization durations at different voltages are 12, 6, 6, 4, 1, 0.5, 0.5, 0.25, and 0.25 h, respectively, to reach their balanced (maximum) nanotube length. Variation in the diameter and length of the NTs as a function of anodization voltage (j).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4269879&req=5

f1: Surface FE-SEM images of the Ni-Ti-O NTAs formed in ethylene glycol containing 0.2 wt% NH4F and 1.0 vol% H2O at 30°C at different anodization voltages.(a) 5 V, (b) 10 V, (c) 15 V, (d) 20 V, (e) 25 V, (f) 30 V, (g) 40 V, (h) 60 V, and (i) 90 V. The anodization durations at different voltages are 12, 6, 6, 4, 1, 0.5, 0.5, 0.25, and 0.25 h, respectively, to reach their balanced (maximum) nanotube length. Variation in the diameter and length of the NTs as a function of anodization voltage (j).
Mentions: The effect of the anodization voltage on the structure of Ni-Ti-O NTAs is shown in Figure 1. The samples are fabricated by anodization in an ethylene glycol solution containing 0.2 wt% NH4F and 1.0 vol% H2O at 30°C. At a low voltage of 5 V, nanotubes (NTs) with a small diameter of about 15 nm are observed. Increasing the voltage from 10 to 25 V results in a linear increase in the NT diameter to 70 nm at 25 V. The NT diameter remains the same in the voltage range of 25-40 V and further voltage increase leads to a slight decrease in the NT diameter to 65 and 60 nm at 60 and 90 V, respectively. The variation in the NT length versus anodization voltage shows a similar trend as that of the diameter, with the largest length of about 1100 nm generated at 25 V. When the voltage exceeds 25 V, evenly distributed micropits occur (Figure S1f-i). The entire surface of micropits is covered by NTAs, but the diameter and length are smaller than those outside the micropits (Figure S2). The elemental composition inside and outside the micropits shows no obvious difference as evidenced by Energy dispersive spectroscopy (EDS) elemental mapping (Figure S3). The variation of current during anodization is similar to that of pure Ti, but its steady-state value is higher. When the voltage exceeds 25 V, current fluctuation in the steady-state phase during the anodization process can be observed (Figure S4a). It is generally accepted that a larger voltage leads to increased NT diameter and length in anodization of pure Ti29, but in case of NiTi alloy, this rule no longer applies when the voltage exceeds 25 V. The deviation may be explained by runaway anodization at an elevated voltage, namely current self-amplification resulting from the resistance heating effect. The resistance heating effect elevates the temperature, which on the one hand accelerates oxide dissolution reducing the NT diameter and length, but on the other hand promotes the formation of electrochemical active sites on the sample surface causing local thinning, breakdown of the oxide film, and formation of micropits30. The micropits act as short-circuit channels to increase the current further heating the sample. After initiation, the micropits will proliferate in both depth and width (Figure S5). At the same time, hydrolysis of metal cations such as Ti4+ and Ni2+ enriched in the micropits reduces the local pH thus accelerating oxide dissolution and decreasing the NT length and diameter in the micropits.

Bottom Line: In the present work, we systemically investigated the influence of various anodization parameters on the formation and structure of Ni-Ti-O NTAs and their potential applications.Our results show that well controlled NTAs can be fabricated during relatively wide ranges of the anodization voltage (5-90 V), electrolyte temperature (10-50°C) and electrolyte NH4F content (0.025-0.8 wt%) but within a narrow window of the electrolyte H2O content (0.0-1.0 vol%).Through modulating these parameters, the Ni-Ti-O NTAs with different diameter (15-70 nm) and length (45-1320 nm) can be produced in a controlled manner.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Surface Engineering, Taiyuan University of Technology No. 79 Yingze West Road, Taiyuan 030024, China.

ABSTRACT
Nickel-titanium-oxide (Ni-Ti-O) nanotube arrays (NTAs) prepared on nearly equiatomic NiTi alloy shall have broad application potential such as for energy storage and biomedicine, but their precise structure control is a great challenge because of the high content of alloying element of Ni, a non-valve metal that cannot form a compact electronic insulating passive layer when anodized. In the present work, we systemically investigated the influence of various anodization parameters on the formation and structure of Ni-Ti-O NTAs and their potential applications. Our results show that well controlled NTAs can be fabricated during relatively wide ranges of the anodization voltage (5-90 V), electrolyte temperature (10-50°C) and electrolyte NH4F content (0.025-0.8 wt%) but within a narrow window of the electrolyte H2O content (0.0-1.0 vol%). Through modulating these parameters, the Ni-Ti-O NTAs with different diameter (15-70 nm) and length (45-1320 nm) can be produced in a controlled manner. Regarding potential applications, the Ni-Ti-O NTAs may be used as electrodes for electrochemical energy storage and non-enzymic glucose detection, and may constitute nanoscaled biofunctional coating to improve the biological performance of NiTi based biomedical implants.

No MeSH data available.


Related in: MedlinePlus