Research Article The Microstructure and Capacitance ...downloads.hindawi.com/journals/jnm/2013/157494.pdf · The Microstructure and Capacitance Characterizations of Anodic Titanium

Hindawi Publishing CorporationJournal of NanomaterialsVolume 2013 Article ID 157494 9 pageshttpdxdoiorg1011552013157494

Research ArticleThe Microstructure and Capacitance Characterizations ofAnodic Titanium Based Alloy Oxide Nanotube

Po Chun Chen1 Sheng Jen Hsieh2 Chien Chon Chen3 and Jun Zou1

1 Department of Electrical Engineering Texas AampM University College Station TX 77843-3128 USA2Department of Engineering Technology Texas AampM University College Station TX 77843-3367 USA3Department of Energy Engineering National United University Miaoli 36003 Taiwan

Correspondence should be addressed to Chien Chon Chen chentexasgmailcom and Jun Zou junzouecetamuedu

Received 15 April 2013 Accepted 18 June 2013

Academic Editor Anukorn Phuruangrat

Copyright copy 2013 Po Chun Chen et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

This paper presents a simple anodization process to fabricate ordered nanotubes (NTs) of titanium and its alloys (Ti-Mo and Ti-Ta)TiO2 MoO

3 and Ta

2O5are high dielectric constant materials for ultracapacitor application The anodic titanium oxide contains a

compact layer on the NT film and a barrier layer under the NT film However the microstructure of oxide films formed by anodicTi-Mo and Ti-Ta alloys contains six layers including a continuous compact layer a continuous partial porous layer a porous layera net layer an ordering NT film and an ordering compact barrier layer There are extra layers which are a partial porous layer anda porous layer not presented on the TiO

2NT film In this paper we fabricated very high surface area ordered nanotubes from Ti

and its alloys Based on the differences of alloys elements and compositions we investigated and calculated the specific capacitanceof these alloys oxide nanotubes

1 Introduction

The demands for energy storage and energy generation areincreasing rapidly with the global energy crisis Ultracapac-itor is a technology for energy storage with advantages oflow cost and high efficiency Barium titanate (BaTiO

3) which

exhibits a very high dielectric constant is a good materialfor ultracapacitor fabrication [1ndash4] However the processesof producing BaTiO

3 such as hydrothermal treatment [5

6] metal-organic process [7] alkoxide hydrolysis [8 9] RFsputtering [10] and sol-gel process [11] have been reportedand they are very complex and costly Titanium dioxide(TiO2) can be formed nanotube by one-step anodizing

process compared with the complex processes fabricatingBaTiO

3 However the dielectric constant of TiO

2is not

as high as BaTiO3 but TiO

2nanotube could be an ideal

dielectric template due to its high surface area A typical TiO2

nanotube fabrication can be achieved by anodization[12]and the ordered channel array of anodic titanium oxidenanotubes is able to serve as multiple parallel dielectric layersfor the ultracapacitor

On the other hand metals (Al [13] Hf [14] Nb [15]Ta [16] W [17] and V [18]) and alloys (Ti-Mo [19] Ti-W[20] Ti-Nb [21] Ti-V [22] Ti-Zr [23] Ti-Ta [24] and Ti-Al [25]) have been reported that they can also be formedhigh surface area of nanoporous oxide filmWO

3 Ta2O5 and

TaTiO3 which have higher dielectric constants than TiO

2 of

1000 [26] 110 [27] and 200 [28] are the alternate dielectricmaterials for ultracapacitor Unfortunately they cannot formnanotubes structures as good as TiO

2nanotubesThus in this

paper we used a simple process of anodization to fabricateTiO2 TiO2-MoO

3 and TiO

2-Ta2O5nanotubes Their high

dielectric constants and large surface areas are very usefulmaterials to build ultracapacitors Based on the nanotubestructural properties such as diameter porosity and lengthwe also investigated the specific capacitances of the differenttitanium alloys

2 Experimental Procedure

An ordered channel array of anodic titanium and titaniumalloy oxides was fabricated by anodizing Ti Ti-10Ta (90wt

2 Journal of Nanomaterials

135120583m

(a)

135120583m

(b)

05 120583m

(c)

135120583m

(d)

05 120583m

(e)

05 120583m

(f)

Figure 1 SEM images of TiO2NT (a) an unwanted film cover onTiO

2NT (b) partial unwanted film removed (c) all unwanted films removed

and TiO2NT presented (d) TiO

2NT side view (e) TiO

2NT bottom view and (f) a barrier layer on the TiO

2NT bottom

Ti + 10wt Ta) Ti-20Ta (80wt Ti + 20wt Ta) andTi-10Mo (90wt Ti + 10wt Mo) alloys The metal sub-strates were first put through electropolishing (EP) The EPelectrolyte included 5 volperchloric acid (HClO

4) 53 vol

ethylene glycol monobutylether (HOCH2CH2OC4H9) and

42 vol methanol (CH3OH) EP processes of Ti and Ti

alloys were conducted at 15∘C under 52V for 1 minute and28V for 13 minutes with platinum as a counter electrodeat a constant stirring rate of 200 rpm After EP the sampleswere etched in 5 vol HF for 5min to form an additionalthin anodic film on the metal substrates TiO

2 TiO2-Ta2O5

and TiO2-MoO

3nanotubes were anodized in an electrolyte

of 05 wt ammonium fluoride (NH4F 999) and 2wt

H2O in ethylene glycol (C

2H4(OH)2) solvent at a constant

voltage of 60V for 2 hours After anodic films were formedby anodization the films were then annealed in an airfurnace at 450∘C for 1 hour for crystallization The surfacemorphologies of the anodic oxides were observed by usinga scanning electron microscope (SEM FEI Quanta 600)The alloy oxide nanotubes compositions can be analyzed byEnergy Dispersive Spectrometer (EDS) (Oxford)

Cyclic voltammetry (CV) performances were evaluatedby an electrochemical analyzer (CH Instruments Model600B USA) using a standard three-electrode cell systemwithplatinum as a counter electrode and silver-silver chlorideelectrode (AgAgCl) as a reference electrode in 05M H

2SO4

solution at room temperature The CV scan rate was set as20mVs in a potential range of 0V to 09V (AgAgCl)

Journal of Nanomaterials 3

16

06

2 146 10Ti

pH

TiO

minus2

minus04

minus14

minus24

TiO3+3

TiO2+

Ti3+

Ti2+ Ti(OH)3

HTiOminus3

HTiOminus4

Ti(OH)4

E(V

)

TiO3middot2H2O

(a)

pH

0

1

2

0 4 8 12

Ta

TaO+2 Ta2O5

E(V

)

minus1

minus2

(b)

pH

02

07

12

0 3 6 9 12

Mo

H2MoO4

MoO3

MoO2minus4

MoO2

E(V

)

minus08

minus03 Mo3+

(c)

Figure 2 Pourbaix diagrams of (a) Ti (b) Ta and (c) Mo

3 Results and Discussion

Figure 1 presents the SEM images of long-range orderednanochannel TiO

2NT structures formed by anodizing pure

Ti foil (a) an unwanted film covered on TiO2NT (b) partial

unwanted film removed (c) all unwanted films removed andthe top view of TiO

2NT (d) side view of TiO

2NT (e) bottom

view of TiO2NT and (f) a barrier layer under the TiO

2NT

TiO2NT feature a pore diameter sim120 nm pore density sim8

times 109 porescm2 and wall thickness sim25 nm the length ofthe NT can be controlled from several 120583ms to hundred 120583mswith different types of the electrolytes (eg NH

4F) and the

anodization times at a constant applied voltage (eg 60V)Immersing titanium in electrolyte causes complex reac-

tions with 16 forms of Ti ions and oxides [29] The Pourbaixdiagram is useful to simplify the complex reactions [30]Based on the Pourbaix diagram of Ti (Figure 2(a)) TiO2+ion is a favorite formation when pH value is lower than 23and voltage is higher than minus02 V (SHE) at 25∘C TiO2+ canfurther react with H

2O to from Ti(OH)

4which is anodic

titanium oxide Similarly Ta Pourbaix diagram (Figure 2(b))shows that TiO2+ is formed and converted to Ta

2O5under the

condition of pH lt 51 and applying voltage gtminus12 V (SHE) atroom temperature Also Mo Pourbaix diagram (Figure 2(c))implies that Mo3+ can be produced and form MoO

3in the

condition of pH being below 42 and voltage being higherthan minus035V (SHE) at 25∘C However anodic TiO

2 MoO

3

and Ta2O5can be formed in the neutral pH value electrolyte

when it contains halogen element in it

Anodization of titanium forms close-packed and vertical-aligned nanotubes in a nonaqueous organic polar electrolytewith Fminus ions and minimizing water content These electro-chemical processes can be described as follows [31ndash34]

Ti 997888rarr Ti4+ + 4eminus (1)

H2O 997888rarr 2H++O2minus (2)

Ti4+ + 2O2minus997888rarr TiO2 (3)

Ti4+ + 2H2O 997888rarr 4H++ TiO2 (4)

6Fminus + TiO2 + 4H+997888rarr [TiF6]

2minus+ 2H2O (5)

[TiF6]2minus+ 119899H2O 997888rarr [TiF6minus119899(OH)

119899]2minus + 119899H+

+ 119899Fminus (6)

[TiF6minus119899(OH)119899]

2minus+ (6 minus 119899)H2O

997888rarr [Ti(OH)6]

2minus+ (6 minus 119899)H+ + (6 minus 119899) Fminus

(7)

[Ti(OH)6]

2minus+ 2H+ 997888rarr TiO

2+ 4H2O (8)

During anodization there are oxidation reactions at theinterface between metal and electrolyte Ti4+ is formed andthe water in the electrolyte is decomposed reactions (1) and(2) TiO

2is then formed between themetal and the electrolyte

through ion migration reactions (3) and (4) Fminus ions etch theTiO2forming [TiF

6]2minus and then combine with the H

2O to

form [TiF6minus119899(OH)119899]

2minus reactions (5) and (6) Because the Fminusions are doped in the TiO

2but do not form a compound

reaction (6) can be rewritten as (7) Finally [Ti(OH)6]

2minus

reacts with 2H+ to form TiO2nanotubes reaction (8)


10120583m

(a)

1120583m

(b)

125 120583m

(c)

125 120583m

(d)

05 120583m

(e)

Figure 3 SEM images of Ti-Ta NT film structure (a) compact layer (b) partial porous film (c) porous film (d) net film and (e) Ti-Ta NT

Based on reactions (1)ndash(8) anodization of Ta can bedescribed as

Ta 997888rarr Ta5+ + 5eminus (9)


2Ta5+ + 5O2minus 997888rarr Ta2O5 (11)

2Ta5+ + 5H2O 997888rarr 10H+ + Ta

2O5

(12)

12Fminus + 2Ta2O5+ 10H+ 997888rarr 2[TaF

6]

minus+ 5H2O (13)

2[TaF6]

minus+ 2119899H

2O 997888rarr 2[TaF

6minus2119899(OH)2119899]

minus+ 2119899H+ + 2119899Fminus

(14)

2[TaF6minus2119899(OH)2119899]

minus+ (6 minus 2119899)H2O

997888rarr [Ta(OH)6]

minus+ (6 minus 2119899)H+ + (6 minus 2119899) Fminus

(15)

2[Ta(OH)6]

minus+ 2H+ 997888rarr Ta

2O5+ 7H2O (16)


1120583m

(a)

1120583m

(b)

1120583m

(c)

1120583m

(d)

Figure 4 SEM images of TiO2-Ta2O5nanotubes film by anodizing Ti-20Ta alloy (a) a net film on the NT top (b) without a net film on the

NT top (c) a barrier layer on the NT bottom and (d) partial barrier layer on the NT bottom

Also anodization of Mo can be described as

Mo 997888rarr Mo3+ + 3eminus (17)


Mo3+ + 3O2minus 997888rarr MoO3

(19)

Mo3+ + 3H2O 997888rarr 6H++MoO

3(20)

6Fminus +MoO3+ 6H+ 997888rarr [MoF

6]

3minus+ 3H2O (21)

[MoF6]

3minus+ 119899H2O 997888rarr [MoF

6minus119899(OH)119899]

3minus+ 119899H+ + 119899Fminus

(22)

[MoF6minus119899(OH)119899]


997888rarr [Mo(OH)6]


(23)

[Mo(OH)6]

3minus+ 3H+ 997888rarr MoO

3+ 3H2O (24)

Figure 3 shows SEM images of TiO2-Ta2O5nanotubes

structure from anodizing Ti-10Ta alloy There was a compactlayer on the top of nanotubes in Figure 3(a) A continuousporous layer and grain boundary under the compact layer

are observed in Figure 3(b) Figure 3(c) shows a porous filmis covering the compact layer and following a net structure(Figure 3(d)) is covering the gap between ordered TiO

2-

Ta2O5nanotubes (Figure 3(e)) There were extra continuous

porous layers and net structures which were not presented onpure TiO

2nanotubes The compact layer continuous porous

layer andnet structurewere removed by 5wtof 1120583mAl2O3

powders in ethanol solvent assisted by ultrasonic vibrationSimilar to Ti-10Ta alloy Figure 4 shows SEM images ofTiO2-Ta2O5nanotube by anodizingTi-20Ta alloy Figure 4(a)

shows a net film on the NT top Figure 4(b) without a net filmon the NT top Figure 4(c) a barrier layer on the NT bottomand Figure 4(d) partial barrier layer under the NT

For the Ti-10Mo alloy Figure 5(a) shows partially re-moved continuous porous layer on the net structure largerpores on the top of TiO

2-MoO

3nanotubes (Figure 5(b))

smaller pores (Figure 5(c)) and barrier layer (Figure 5(d))on the bottom side According to Figures 3ndash5 Figure 6 is aschematic diagram of anodic Ti alloy oxide structure withcompact layer continuous porous layer net structure andordered nanotubes on the alloys surfaces

Figure 7 shows a schematic structure and geometry ofthe Ti alloy oxide nanotube Larger open pores are on the


125 120583m

(a)

05 120583m

(b)

1120583m

(c)

125 120583m

(d)

Figure 5 SEM images of TiO2-MoO

3nanotubes film by anodizing Ti-10Mo alloy (a) a porous film and a net film on theNT top (b) a cleaned

NT top (c) small pores on the NT bottom and (d) a barrier layer on the NT bottom

Table 1 EDS results of Ti alloys oxide nanotubes

TiO2 () Ta2O5 () MoO3 ()Ti-20Ta 839 161 0Ti-10Ta 913 87 0Ti-10Mo 928 0 72

top (Figure 7(a)) smaller closed pores and a barrier layerin a hexagonal pattern are on the bottom side (Figure 7(b))tube inner surface area (Figure 7(c)) and outer surfacearea (Figure 7(d)) Denoting 119877

1and 119877

2 and 119879

1and 119879

2are

the radius and pores width of the top and bottom poresrespective119882 is the thickness of the outer barrier layer and119867 and 119871 is the inner height and total length of the nanotubeWe have 119877

1+ 1198791= 1198772+ 1198792= 1198773 and total length of nanotube

is 119871 = 119867+119882 Thus the volume of a single alloy oxide can becalculated by119881 = 119881outer minus119881inner where119881outer and119881inner can beobtained by

119881outer = 1205871198772

3times 119871

119881inner =1

3

120587 times

119867

119877

1minus 119877

2

times (119877

3

1minus 119877

3

2)

(25)

Based on the SEM images in Figures 3 4 and 5119877111987721198773

and 119882 were 60 nm 25 nm 80 nm and 40 nm respectivelyFor two hours anodization process 20120583m length of Ti alloyoxide nanotubes (119871) could be formed on the Ti alloy surfaceThus 119881outer was 04120583m

3 and 119881inner was 012 120583m3 and the

volume of a single alloy oxide nanotube (119881) was 028120583m3The TiO

2nanotubes density has been recently reported by

Chen et al [29] such that there are 4510548978 nanotubesper cm2 Therefore the total volume of Ti alloy nanotubeswas 126 times 10minus3 cm3 in 1 cm2 sample area Moreover it hasalso been reported that nanotube surface area is greatlyincreased when 119871 = 10 120583m 119878inner = 1205 cm

2 119878outer =2402 cm2 and 119871 = 100 120583m 119878inner = 1205 cm

2 119878outer =2402 cm2 Figure 8 furthermore accumulated anodic Ti andTi alloy NT inner and outer surface areas increased withfilm thickness increased based on 1 cm2 substrate Hence theextremely high surface area is able to provide more chancesfor electrochemical reactions

According to the Pourbaix diagrams in Figure 2 anodiz-ing Ti Ti-20Ta Ti-10Ta and Ti-10Mo can form anodic oxidefilms of these Ti alloys Therefore the following alloy anodicoxide films densities are able to be calculated based on theTiO2 Ta2O5 andMoO

3densities of 42 gcm3 82 gcm3 and


Table 2 Specific capacitance based on TiO2 NT Ti-10Ta NT Ti-20Ta NT and Ti-10Mo NT films

Sample size (1 cm2times 20 120583m) TiO2 NT Ti-10Ta NT Ti-20Ta NT Ti-10Mo NT

Density (gcm2) 309 319 365 307Mass of unit area (mgcm2) 618 638 730 614119889119876 (mC) 6558 12002 14330 10292119889119864 (V) 09 09 09 09Specific capacitance (Fg) 118 209 218 186

(a)

(b)

(c)

(d)

Ti-Ta or Ti-Mo alloy

Barrier layer

TiO2-Ta2O5NT or TiO2-MoO3 NT

(e)

Figure 6The schematic diagram of TiO2-Ta2O5NT or TiO

2-MoO

3

NT film structure (a) compact layer (b) partial porous film (c)porous film (d) net film and (e) TiO

2-Ta2O5NT or TiO

2-MoO

3

NT and barrier layer on the Ti-Ta or Ti-Mo alloy

47 gcm3 respectively According to EDS results in Table 1Ti Ti-20Ta Ti-10Ta and Ti-10Mo formed 100 TiO

2 839

TiO2+ 161 Ta

2O5 913 TiO

2+ 87 Ta

2O5 and 928

TiO2+ 72MoO

3The densities of 100TiO

2 839TiO

2+

161 Ta2O5 913 TiO

2+ 87 Ta

2O5 and 928 TiO

2+

72 MoO3were 423 gcm3 484 gcm3 454 gcm3 and

424 gcm3 respectively Therefore the mass of nanotubesfilms 1 cm2 sample for each alloy was listed in Table 2 being532mgcm2 609mgcm2 572mgcm2 and 534mgcm2

Cyclic voltammograms (CV) are used to characterize thecapacitors behavior of the alloy oxide nanotubes Figure 9shows capacitance performance evaluations for the Ti alloyanodic oxide nanotubes by cyclic voltammograms It is clearthat Ti alloy oxide nanotubes had larger area of CV curvethan pure TiO

2nanotube did It means that Ti alloys oxide

nanotubes had larger capacitances than pure TiO2nanotubes

Besides more Ta2O5content can significantly enhance the

capacitor performance by comparing two Ti-Ta alloys curveswith different compositions Moreover Ti-10Mo alloy oxidenanotubes CV curve shows a symmetrical shape whichindicates that the revisable redox reaction of Mo2+Mo3+ washelpful to improve the capacitor performance The specificcapacitance (119862) can bemeasured by voltage step current stepor voltage ramp methods and evaluated by the equations of119862 = 119876119881 and 119862 = 119889119876119889119881 [35] where 119881 is applied voltageand 119876 is the quantity of charge on the electrode (whichcan be evaluated from the area of the CV curve) Table 2shows the specific capacitance based on 1 cm2 sample areaand 20120583m film thickness of pure Ti Ti-20Ta Ti-10Ta andTi-10Mo oxide nanotubes films which are 137 Fg 261 Fg233 Fg and 214 Fg respectively The specific capacitancesof Ti alloys oxide nanotubes films were higher than thatof TiO

2-B nanowiresMWCNTs hybrid supercapacitor with

specific capacitance of 177 Fg [36]

4 Conclusions

In summary we fabricated ultracapacitors based on thework-ing electrode made of highly ordered anodic TiO

2 Ta2O5

and MoO3nanotubes directly formed on pure Ti Ti-20Ta

Ti-10Ta and Ti-10Mo substrates The ordered alloys oxidenanotubes structure has a volume of 126 times 10minus3 cm3 in 1 cm2sample area with nanotube density of 45 times 109 tubescm2The mass of pure Ti and Ti alloys oxide nanotubes films with1 cm2 sample size and 20120583m film thickness can be calcu-lated as 532mg (TiO

2nanotubes) 609mg (Ti-20Ta oxide

nanotubes) 572mg (Ti-10Ta oxide nanotubes) and 534mg


H

W

R1

R2

R3

(a)

Top

Bottom

R1

R2

T1

T2

(b)

L

Inne

r sur

face

2120587R1

2120587R2

(c)

Out

er su

rface

H+W

4radic3(R1 + T1)

(d)

Figure 7 Estimation of TiO2NT surface (a) cone structure of inner

tube with radius of 1198773 and 119877

1 and 119877

2on the tube top and bottom

tube length with 119867 (b) pore wall thickness with 1198791and 119879

2on the

tube top and bottom (c) tube inner surface area and (d) outersurface area

0

500

1000

1500

2000

2500

0 25 50 75 100

Outer surface area

Inner surface area

Length (120583m)

Surfa

ce ar

ea (c

m2)

Figure 8 Accumulated anodic Ti and Ti alloy NT inner and outersurface areas based on 1 cm2 substrate

0

2

4

01SEC (V)

minus11minus6

minus4

minus2

minus08 minus05 minus02

Curr

ent d

ensit

y (m

Ac

m2)

TiO2

Ti-10MoO3

TiO2-10Ta2O5TiO2-20Ta2O5

Figure 9 Capacitance performance evaluations for TiO2NT TiO

2-

10 Ta2O5NT TiO

2-20 Ta

2O5NT and TiO

2-10 MoO

3NT by cyclic

voltammograms

(Ti-10Mo oxide nanotubes) respectively Furthermore Tialloy anodic oxide nanotubes films with 1 cm2 surface and20120583m thickness have an inner surface area of 2410 cm2 andouter surface area of 4804 cm2 Thus such large surface areaof dielectric oxides caused very high specific capacitancesThe specific capacitance can further be enhanced by (1)reacting with barium nitrate (Ba(NO

3)2) [37] or barium

hydroxide (Ba(OH)2) [38] to form a very high dielectric

constant BaTiO3film (2) increasing nanotubes length by

longer anodization process and (3) increasing nanotubessurface area by coating TiO

2nanoparticles on the nanotubes

surface [39]

Acknowledgment

This study was partially supported by a Grant from theNational Science Council Taiwan (102-3113-P-042A-005-)

References

[1] L E Cross ldquoFerroelectric materials for electromechanicaltransducer applicationsrdquo Materials Chemistry and Physics vol43 no 2 pp 108ndash115 1996

[2] A D Hilton and R Frost ldquoRecent developments in the manu-facture of barium titanate powdersrdquo Key Engineering Materialsvol 66 pp 145ndash184 1992

[3] L E Cross ldquoDielectric piezoelectric and ferroelectric compo-nentsrdquo American Ceramic Society Bulletin vol 63 no 4 pp586ndash590 1984

[4] D Pandey A P Singh and V S Tiwari ldquoDevelopments inferroelectric ceramics for capacitor applicationsrdquo Bulletin ofMaterials Science vol 15 no 5 pp 391ndash402 1992

[5] K Kajiyoshi N Ishizawa and M Yoshimura ldquoPreparation oftetragonal barium titanate thin film on titaniummetal substrateby hydrothermal methodrdquo Journal of the American CeramicSociety vol 74 no 2 pp 369ndash374 1991

[6] T Horikawa N Mikami T Makita et al ldquoDielectric propertiesof (Ba Sr)TiO

3thin films deposited by RF sputteringrdquo Japanese

Journal of Applied Physics vol 32 no 9 pp 4126ndash4130 1993


[7] A S Shaikh and G M Vest ldquoKinetics of BaTiO3and PbTiO

3

formation from metallo-organic precursorsrdquo Journal of theAmerican Ceramic Society vol 69 no 9 pp 682ndash688 1986

[8] H Okamura andH K Bowen ldquoPreparation of alkoxides for thesynthesis of ceramicsrdquo Ceramics International vol 12 no 3 pp161ndash171 1986

[9] K W Kirby ldquoAlkoxide synthesis techniques for BaTiO3rdquoMate-

rials Research Bulletin vol 23 no 6 pp 881ndash890 1988[10] P Bhattacharya T Komeda K-H Park and Y Nishioka

ldquoComparative study of amorphous and crystalline (Ba Sr)TiO3

thin films deposited by laser ablationrdquo Japanese Journal ofApplied Physics vol 32 no 9 pp 4103ndash4106 1993

[11] D M Tahan A Safari and L C Klein ldquoPreparation and char-acterization of Ba

119909Sr1minus119909

TiO3thin films by a Sol-Gel techniquerdquo

Journal of the American Ceramic Society vol 79 no 6 pp 1593ndash1598 1996

[12] C-C Chen J-H Chen C-G Chao and W C Say ldquoElectro-chemical characteristics of surface of titanium formed by elec-trolytic polishing and anodizingrdquo Journal of Materials Sciencevol 40 no 15 pp 4053ndash4059 2005

[13] C-C Chen Y Bisrat Z P Luo R E Schaak C-G Chao andD C Lagoudas ldquoFabrication of single-crystal tin nanowires byhydraulic pressure injectionrdquo Nanotechnology vol 17 no 2 pp367ndash374 2006

[14] H Tsuchiya and P Schmuki ldquoSelf-organized high aspect ratioporous hafnium oxide prepared by electrochemical anodiza-tionrdquo Electrochemistry Communications vol 7 no 1 pp 49ndash522005

[15] I Sieber H Hildebrand A Friedrich and P Schmuki ldquoForma-tion of self-organized niobium porous oxide on niobiumrdquo Elec-trochemistry Communications vol 7 no 1 pp 97ndash100 2005

[16] I Sieber B Kannan and P Schmuki ldquoSelf-assembled poroustantalum oxide prepared in H

2SO4HF electrolytesrdquo Electro-

chemical and Solid-State Letters vol 8 no 3 pp J10ndashJ12 2005[17] N Mukherjee M Paulose O K Varghese G K Mor and

C A Grimes ldquoFabrication of nanoporous tungsten oxide bygalvanostatic anodizationrdquo Journal ofMaterials Research vol 18no 10 pp 2296ndash2299 2003

[18] G B Stefanovich A L Pergament A A Velichko and L AStefanovich ldquoAnodic oxidation of vanadium and properties ofvanadium oxide filmsrdquo Journal of Physics Condensed Mattervol 16 no 23 pp 4013ndash4024 2004

[19] N K Shrestha Y-C Nah H Tsuchiya and P SchmukildquoSelf-organized nano-tubes of TiO

2-MoO

3with enhanced elec-

trochromic propertiesrdquo Chemical Communications no 15 pp2008ndash2010 2009

[20] I Paramasivam Y-C Nah C Das N K Shrestha and PSchmuki ldquoWO

3TiO2nanotubes with strongly enhanced pho-

tocatalytic activityrdquoChemistrymdashA European Journal vol 16 no30 pp 8993ndash8997 2010

[21] A Ghicov S Aldabergenova H Tsuchyia and P SchmukildquoTiO2-Nb2O5nanotubes with electrochemically tunable mor-

phologiesrdquo Angewandte ChemiemdashInternational Edition vol 45no 42 pp 6993ndash6996 2006

[22] Y Yang D Kim M Yang and P Schmuki ldquoVertically alignedmixed V

2O5-TiO2nanotube arrays for supercapacitor applica-

tionsrdquoChemical Communications vol 47 no 27 pp 7746ndash77482011

[23] H Jha R Hahn and P Schmuki ldquoUltrafast oxide nanotube for-mation on TiNb TiZr and TiTa alloys by rapid breakdown an-odizationrdquo Electrochimica Acta vol 55 no 28 pp 8883ndash88872010

[24] WWei S Berger N Shrestha and P Schmuki ldquoIdeal hexagonalorder formation of self-organized anodic oxide nanotubes andnanopores on a Ti-35Ta alloyrdquo Journal of the ElectrochemicalSociety vol 157 no 12 pp C409ndashC413 2010

[25] H Tsuchiya S Berger J M Macak A Ghicov and P SchmukildquoSelf-organized porous and tubular oxide layers on TiAl alloysrdquoElectrochemistry Communications vol 9 no 9 pp 2397ndash24022007

[26] R J D Tilley ldquoCorrelation between dielectric constant anddefect structure of non-stoichiometric solidsrdquo Nature vol 269no 5625 pp 229ndash231 1977

[27] J Lin N Masaaki A Tsukune and M Yamada ldquoTa2O5thin

films with exceptionally high dielectric constantrdquo Applied Phys-ics Letters vol 74 no 16 pp 2370ndash2372 1999

[28] H Segawa K Mori M Itagati K Sakurki and T Ishiwta ldquoIm-age sensing devicerdquo US patent no 4499384 1985

[29] C C Chen D Fang and Z Luo ldquoFabrication and characteriza-tion of highly-ordered valve-metal oxide nanotubes and theirderivative nanostructuresrdquo Reviews in Nanoscience and Nan-otechnology vol 1 no 4 pp 1ndash28 2012

[30] M Pourbaix Atlas of Electrochemical Equilibria in AqueousSolutions NACE Houston Tex USA 1974

[31] C W Lai and S Sreekantan ldquoEffect of applied potential onthe formation of self-organized TiO

2nanotube arrays and its

photoelectrochemical responserdquo Journal of Nanomaterials vol2011 Article ID 142463 7 pages 2011

[32] J H Lim and J Choi ldquoTitanium oxide nanowires originat-ing from anodically grown nanotubes the bamboo-splittingmodelrdquo Small vol 3 no 9 pp 1504ndash1507 2007

[33] J Tao J Zhao X Wang Y Kang and Y Li ldquoFabrication oftitania nanotube arrays on curved surfacerdquo ElectrochemistryCommunications vol 10 no 8 pp 1161ndash1163 2008

[34] D Kim F Schmidt-Stein R Hahn and P Schmuki ldquoGravityassisted growth of self-organized anodic oxide nanotubes ontitaniumrdquo Electrochemistry Communications vol 10 no 7 pp1082ndash1086 2008

[35] A J Bard and L R Faulkner Electrochemical Methods Funda-mentals and Applications John Wiley amp Sons Singapore 1980

[36] G Wang Z Y Liu J N Wu and Q Lu ldquoPreparation and elec-trochemical capacitance behavior of TiO

2-B nanotubes for hy-

brid supercapacitorrdquoMaterials Letters vol 71 pp 120ndash122 2012[37] L Zhang Y Shi S Peng J Liang Z Tao and J Chen ldquoDye-

sensitized solar cells made from BaTiO3-coated TiO

2nano-

porous electrodesrdquo Journal of Photochemistry and PhotobiologyA vol 197 no 2-3 pp 260ndash265 2008

[38] XWei ldquoHydrothermal synthesis of BaTiO3thin films on nano-

porous TiO2covered Ti substratesrdquo Journal of Crystal Growth

vol 286 no 2 pp 371ndash375 2006[39] C-C Chen H-W Chung C-H Chen et al ldquoFabrication and

characterization of anodic titanium oxide nanotube arrays ofcontrolled length for highly efficient dye-sensitized solar cellsrdquoJournal of Physical Chemistry C vol 112 no 48 pp 19151ndash191572008

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


135120583m

(a)

135120583m

(b)

05 120583m

(c)

135120583m

(d)

05 120583m

(e)

05 120583m

(f)

Figure 1 SEM images of TiO2NT (a) an unwanted film cover onTiO

2NT (b) partial unwanted film removed (c) all unwanted films removed

and TiO2NT presented (d) TiO

2NT side view (e) TiO

2NT bottom view and (f) a barrier layer on the TiO

2NT bottom

Ti + 10wt Ta) Ti-20Ta (80wt Ti + 20wt Ta) andTi-10Mo (90wt Ti + 10wt Mo) alloys The metal sub-strates were first put through electropolishing (EP) The EPelectrolyte included 5 volperchloric acid (HClO

4) 53 vol

ethylene glycol monobutylether (HOCH2CH2OC4H9) and

42 vol methanol (CH3OH) EP processes of Ti and Ti

alloys were conducted at 15∘C under 52V for 1 minute and28V for 13 minutes with platinum as a counter electrodeat a constant stirring rate of 200 rpm After EP the sampleswere etched in 5 vol HF for 5min to form an additionalthin anodic film on the metal substrates TiO

2 TiO2-Ta2O5

and TiO2-MoO

3nanotubes were anodized in an electrolyte

of 05 wt ammonium fluoride (NH4F 999) and 2wt

H2O in ethylene glycol (C

2H4(OH)2) solvent at a constant

voltage of 60V for 2 hours After anodic films were formedby anodization the films were then annealed in an airfurnace at 450∘C for 1 hour for crystallization The surfacemorphologies of the anodic oxides were observed by usinga scanning electron microscope (SEM FEI Quanta 600)The alloy oxide nanotubes compositions can be analyzed byEnergy Dispersive Spectrometer (EDS) (Oxford)

Cyclic voltammetry (CV) performances were evaluatedby an electrochemical analyzer (CH Instruments Model600B USA) using a standard three-electrode cell systemwithplatinum as a counter electrode and silver-silver chlorideelectrode (AgAgCl) as a reference electrode in 05M H

2SO4

solution at room temperature The CV scan rate was set as20mVs in a potential range of 0V to 09V (AgAgCl)


16

06

2 146 10Ti

pH

TiO

minus2

minus04

minus14

minus24

TiO3+3

TiO2+

Ti3+

Ti2+ Ti(OH)3

HTiOminus3

HTiOminus4

Ti(OH)4

E(V

)

TiO3middot2H2O

(a)

pH

0

1

2

0 4 8 12

Ta

TaO+2 Ta2O5

E(V

)

minus1

minus2

(b)

pH

02

07

12

0 3 6 9 12

Mo

H2MoO4

MoO3

MoO2minus4

MoO2

E(V

)

minus08

minus03 Mo3+

(c)








2NT (e) bottom


2NT



4F) and the



2O to from Ti(OH)

4which is anodic


2O5under the


3in the


2 MoO

3







Ti4+ + 2H2O 997888rarr 4H++ TiO2 (4)


2minus+ 2H2O (5)


119899]2minus + 119899H+

+ 119899Fminus (6)

[TiF6minus119899(OH)119899]




(7)

[Ti(OH)6]


2+ 4H2O (8)





2O to





2minus



10120583m

(a)

1120583m

(b)

125 120583m

(c)

125 120583m

(d)

05 120583m

(e)






2Ta5+ + 5H2O 997888rarr 10H+ + Ta

2O5

(12)


6]

minus+ 5H2O (13)

2[TaF6]

minus+ 2119899H

2O 997888rarr 2[TaF

6minus2119899(OH)2119899]

minus+ 2119899H+ + 2119899Fminus

(14)

2[TaF6minus2119899(OH)2119899]




(15)

2[Ta(OH)6]


2O5+ 7H2O (16)


1120583m

(a)

1120583m

(b)

1120583m

(c)

1120583m

(d)







(19)


3(20)


6]

3minus+ 3H2O (21)

[MoF6]


6minus119899(OH)119899]

3minus+ 119899H+ + 119899Fminus

(22)

[MoF6minus119899(OH)119899]




(23)

[Mo(OH)6]


3+ 3H2O (24)




2-








2-MoO





125 120583m

(a)

05 120583m

(b)

1120583m

(c)

125 120583m

(d)







1and 119877

2 and 119879

1and 119879

2are




119881outer = 1205871198772

3times 119871

119881inner =1

3

120587 times

119867

119877

1minus 119877

2

times (119877

3

1minus 119877

3

2)

(25)















(a)

(b)

(c)

(d)


Barrier layer


(e)


2-MoO

3


2-Ta2O5NT or TiO

2-MoO

3



2 839

TiO2+ 161 Ta

2O5 913 TiO

2+ 87 Ta

2O5 and 928

TiO2+ 72MoO


2 839TiO

2+

161 Ta2O5 913 TiO

2+ 87 Ta

2O5 and 928 TiO

2+










4 Conclusions


2 Ta2O5






H

W

R1

R2

R3

(a)

Top

Bottom

R1

R2

T1

T2

(b)

L

Inne

r sur

face

2120587R1

2120587R2

(c)

Out

er su

rface

H+W

4radic3(R1 + T1)

(d)



1 and 119877



2on the


0

500

1000

1500

2000

2500

0 25 50 75 100

Outer surface area

Inner surface area

Length (120583m)

Surfa

ce ar

ea (c

m2)


0

2

4

01SEC (V)

minus11minus6

minus4

minus2


Curr

ent d

ensit

y (m

Ac

m2)

TiO2

Ti-10MoO3



2-

10 Ta2O5NT TiO

2-20 Ta

2O5NT and TiO

2-10 MoO

3NT by cyclic

voltammograms


3)2) [37] or barium





surface [39]

Acknowledgment


References











3








119909Sr1minus119909













2-MoO































2nano-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




16

06

2 146 10Ti

pH

TiO

minus2

minus04

minus14

minus24

TiO3+3

TiO2+

Ti3+

Ti2+ Ti(OH)3

HTiOminus3

HTiOminus4

Ti(OH)4

E(V

)

TiO3middot2H2O

(a)

pH

0

1

2

0 4 8 12

Ta

TaO+2 Ta2O5

E(V

)

minus1

minus2

(b)

pH

02

07

12

0 3 6 9 12

Mo

H2MoO4

MoO3

MoO2minus4

MoO2

E(V

)

minus08

minus03 Mo3+

(c)








2NT (e) bottom


2NT



4F) and the



2O to from Ti(OH)

4which is anodic


2O5under the


3in the


2 MoO

3







Ti4+ + 2H2O 997888rarr 4H++ TiO2 (4)


2minus+ 2H2O (5)


119899]2minus + 119899H+

+ 119899Fminus (6)

[TiF6minus119899(OH)119899]




(7)

[Ti(OH)6]


2+ 4H2O (8)





2O to





2minus



10120583m

(a)

1120583m

(b)

125 120583m

(c)

125 120583m

(d)

05 120583m

(e)






2Ta5+ + 5H2O 997888rarr 10H+ + Ta

2O5

(12)


6]

minus+ 5H2O (13)

2[TaF6]

minus+ 2119899H

2O 997888rarr 2[TaF

6minus2119899(OH)2119899]

minus+ 2119899H+ + 2119899Fminus

(14)

2[TaF6minus2119899(OH)2119899]




(15)

2[Ta(OH)6]


2O5+ 7H2O (16)


1120583m

(a)

1120583m

(b)

1120583m

(c)

1120583m

(d)







(19)


3(20)


6]

3minus+ 3H2O (21)

[MoF6]


6minus119899(OH)119899]

3minus+ 119899H+ + 119899Fminus

(22)

[MoF6minus119899(OH)119899]




(23)

[Mo(OH)6]


3+ 3H2O (24)




2-








2-MoO





125 120583m

(a)

05 120583m

(b)

1120583m

(c)

125 120583m

(d)







1and 119877

2 and 119879

1and 119879

2are




119881outer = 1205871198772

3times 119871

119881inner =1

3

120587 times

119867

119877

1minus 119877

2

times (119877

3

1minus 119877

3

2)

(25)















(a)

(b)

(c)

(d)


Barrier layer


(e)


2-MoO

3


2-Ta2O5NT or TiO

2-MoO

3



2 839

TiO2+ 161 Ta

2O5 913 TiO

2+ 87 Ta

2O5 and 928

TiO2+ 72MoO


2 839TiO

2+

161 Ta2O5 913 TiO

2+ 87 Ta

2O5 and 928 TiO

2+










4 Conclusions


2 Ta2O5






H

W

R1

R2

R3

(a)

Top

Bottom

R1

R2

T1

T2

(b)

L

Inne

r sur

face

2120587R1

2120587R2

(c)

Out

er su

rface

H+W

4radic3(R1 + T1)

(d)



1 and 119877



2on the


0

500

1000

1500

2000

2500

0 25 50 75 100

Outer surface area

Inner surface area

Length (120583m)

Surfa

ce ar

ea (c

m2)


0

2

4

01SEC (V)

minus11minus6

minus4

minus2


Curr

ent d

ensit

y (m

Ac

m2)

TiO2

Ti-10MoO3



2-

10 Ta2O5NT TiO

2-20 Ta

2O5NT and TiO

2-10 MoO

3NT by cyclic

voltammograms


3)2) [37] or barium





surface [39]

Acknowledgment


References











3








119909Sr1minus119909













2-MoO































2nano-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




10120583m

(a)

1120583m

(b)

125 120583m

(c)

125 120583m

(d)

05 120583m

(e)






2Ta5+ + 5H2O 997888rarr 10H+ + Ta

2O5

(12)


6]

minus+ 5H2O (13)

2[TaF6]

minus+ 2119899H

2O 997888rarr 2[TaF

6minus2119899(OH)2119899]

minus+ 2119899H+ + 2119899Fminus

(14)

2[TaF6minus2119899(OH)2119899]




(15)

2[Ta(OH)6]


2O5+ 7H2O (16)


1120583m

(a)

1120583m

(b)

1120583m

(c)

1120583m

(d)







(19)


3(20)


6]

3minus+ 3H2O (21)

[MoF6]


6minus119899(OH)119899]

3minus+ 119899H+ + 119899Fminus

(22)

[MoF6minus119899(OH)119899]




(23)

[Mo(OH)6]


3+ 3H2O (24)




2-








2-MoO





125 120583m

(a)

05 120583m

(b)

1120583m

(c)

125 120583m

(d)







1and 119877

2 and 119879

1and 119879

2are




119881outer = 1205871198772

3times 119871

119881inner =1

3

120587 times

119867

119877

1minus 119877

2

times (119877

3

1minus 119877

3

2)

(25)















(a)

(b)

(c)

(d)


Barrier layer


(e)


2-MoO

3


2-Ta2O5NT or TiO

2-MoO

3



2 839

TiO2+ 161 Ta

2O5 913 TiO

2+ 87 Ta

2O5 and 928

TiO2+ 72MoO


2 839TiO

2+

161 Ta2O5 913 TiO

2+ 87 Ta

2O5 and 928 TiO

2+










4 Conclusions


2 Ta2O5






H

W

R1

R2

R3

(a)

Top

Bottom

R1

R2

T1

T2

(b)

L

Inne

r sur

face

2120587R1

2120587R2

(c)

Out

er su

rface

H+W

4radic3(R1 + T1)

(d)



1 and 119877



2on the


0

500

1000

1500

2000

2500

0 25 50 75 100

Outer surface area

Inner surface area

Length (120583m)

Surfa

ce ar

ea (c

m2)


0

2

4

01SEC (V)

minus11minus6

minus4

minus2


Curr

ent d

ensit

y (m

Ac

m2)

TiO2

Ti-10MoO3



2-

10 Ta2O5NT TiO

2-20 Ta

2O5NT and TiO

2-10 MoO

3NT by cyclic

voltammograms


3)2) [37] or barium





surface [39]

Acknowledgment


References











3








119909Sr1minus119909













2-MoO































2nano-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




1120583m

(a)

1120583m

(b)

1120583m

(c)

1120583m

(d)







(19)


3(20)


6]

3minus+ 3H2O (21)

[MoF6]


6minus119899(OH)119899]

3minus+ 119899H+ + 119899Fminus

(22)

[MoF6minus119899(OH)119899]




(23)

[Mo(OH)6]


3+ 3H2O (24)




2-








2-MoO





125 120583m

(a)

05 120583m

(b)

1120583m

(c)

125 120583m

(d)







1and 119877

2 and 119879

1and 119879

2are




119881outer = 1205871198772

3times 119871

119881inner =1

3

120587 times

119867

119877

1minus 119877

2

times (119877

3

1minus 119877

3

2)

(25)















(a)

(b)

(c)

(d)


Barrier layer


(e)


2-MoO

3


2-Ta2O5NT or TiO

2-MoO

3



2 839

TiO2+ 161 Ta

2O5 913 TiO

2+ 87 Ta

2O5 and 928

TiO2+ 72MoO


2 839TiO

2+

161 Ta2O5 913 TiO

2+ 87 Ta

2O5 and 928 TiO

2+










4 Conclusions


2 Ta2O5






H

W

R1

R2

R3

(a)

Top

Bottom

R1

R2

T1

T2

(b)

L

Inne

r sur

face

2120587R1

2120587R2

(c)

Out

er su

rface

H+W

4radic3(R1 + T1)

(d)



1 and 119877



2on the


0

500

1000

1500

2000

2500

0 25 50 75 100

Outer surface area

Inner surface area

Length (120583m)

Surfa

ce ar

ea (c

m2)


0

2

4

01SEC (V)

minus11minus6

minus4

minus2


Curr

ent d

ensit

y (m

Ac

m2)

TiO2

Ti-10MoO3



2-

10 Ta2O5NT TiO

2-20 Ta

2O5NT and TiO

2-10 MoO

3NT by cyclic

voltammograms


3)2) [37] or barium





surface [39]

Acknowledgment


References











3








119909Sr1minus119909













2-MoO































2nano-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




125 120583m

(a)

05 120583m

(b)

1120583m

(c)

125 120583m

(d)







1and 119877

2 and 119879

1and 119879

2are




119881outer = 1205871198772

3times 119871

119881inner =1

3

120587 times

119867

119877

1minus 119877

2

times (119877

3

1minus 119877

3

2)

(25)















(a)

(b)

(c)

(d)


Barrier layer


(e)


2-MoO

3


2-Ta2O5NT or TiO

2-MoO

3



2 839

TiO2+ 161 Ta

2O5 913 TiO

2+ 87 Ta

2O5 and 928

TiO2+ 72MoO


2 839TiO

2+

161 Ta2O5 913 TiO

2+ 87 Ta

2O5 and 928 TiO

2+










4 Conclusions


2 Ta2O5






H

W

R1

R2

R3

(a)

Top

Bottom

R1

R2

T1

T2

(b)

L

Inne

r sur

face

2120587R1

2120587R2

(c)

Out

er su

rface

H+W

4radic3(R1 + T1)

(d)



1 and 119877



2on the


0

500

1000

1500

2000

2500

0 25 50 75 100

Outer surface area

Inner surface area

Length (120583m)

Surfa

ce ar

ea (c

m2)


0

2

4

01SEC (V)

minus11minus6

minus4

minus2


Curr

ent d

ensit

y (m

Ac

m2)

TiO2

Ti-10MoO3



2-

10 Ta2O5NT TiO

2-20 Ta

2O5NT and TiO

2-10 MoO

3NT by cyclic

voltammograms


3)2) [37] or barium





surface [39]

Acknowledgment


References











3








119909Sr1minus119909













2-MoO































2nano-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







(a)

(b)

(c)

(d)


Barrier layer


(e)


2-MoO

3


2-Ta2O5NT or TiO

2-MoO

3



2 839

TiO2+ 161 Ta

2O5 913 TiO

2+ 87 Ta

2O5 and 928

TiO2+ 72MoO


2 839TiO

2+

161 Ta2O5 913 TiO

2+ 87 Ta

2O5 and 928 TiO

2+










4 Conclusions


2 Ta2O5






H

W

R1

R2

R3

(a)

Top

Bottom

R1

R2

T1

T2

(b)

L

Inne

r sur

face

2120587R1

2120587R2

(c)

Out

er su

rface

H+W

4radic3(R1 + T1)

(d)



1 and 119877



2on the


0

500

1000

1500

2000

2500

0 25 50 75 100

Outer surface area

Inner surface area

Length (120583m)

Surfa

ce ar

ea (c

m2)


0

2

4

01SEC (V)

minus11minus6

minus4

minus2


Curr

ent d

ensit

y (m

Ac

m2)

TiO2

Ti-10MoO3



2-

10 Ta2O5NT TiO

2-20 Ta

2O5NT and TiO

2-10 MoO

3NT by cyclic

voltammograms


3)2) [37] or barium





surface [39]

Acknowledgment


References











3








119909Sr1minus119909













2-MoO































2nano-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




H

W

R1

R2

R3

(a)

Top

Bottom

R1

R2

T1

T2

(b)

L

Inne

r sur

face

2120587R1

2120587R2

(c)

Out

er su

rface

H+W

4radic3(R1 + T1)

(d)



1 and 119877



2on the


0

500

1000

1500

2000

2500

0 25 50 75 100

Outer surface area

Inner surface area

Length (120583m)

Surfa

ce ar

ea (c

m2)


0

2

4

01SEC (V)

minus11minus6

minus4

minus2


Curr

ent d

ensit

y (m

Ac

m2)

TiO2

Ti-10MoO3



2-

10 Ta2O5NT TiO

2-20 Ta

2O5NT and TiO

2-10 MoO

3NT by cyclic

voltammograms


3)2) [37] or barium





surface [39]

Acknowledgment


References











3








119909Sr1minus119909













2-MoO































2nano-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





3








119909Sr1minus119909













2-MoO































2nano-













CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article The Microstructure and Capacitance ...downloads.hindawi.com/journals/jnm/2013/157494.pdf · The Microstructure and Capacitance Characterizations of Anodic Titanium