Electrosynthesis of a Novel Poly(3-amino-1,2,4-triazole) - American

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Electrosynthesis of a novel poly(3-amino-1, 2, 4-triazole) + TiO2 hybrid composite on copper and its corrosion protection Ganesan Rajkumar, and Mathur Gopalakrishnan Sethuraman Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie401444b • Publication Date (Web): 01 Oct 2013 Downloaded from http://pubs.acs.org on October 4, 2013

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Industrial & Engineering Chemistry Research

Electrosynthesis of a novel poly(3-amino-1, 2, 4-triazole) + TiO2 hybrid composite on copper and its corrosion protection

Ganesan Rajkumar and Mathur Gopalakrishnan Sethuraman*,

Department of Chemistry, Gandhigram Rural Institute – Deemed University Gandhigram – 624 302, Dindigul, Tamil Nadu, India * [email protected]

*Author for correspondence: e-mail: [email protected] Phone: 0451-2452371. Mobile: +91 94430 21565.

1

ACS Paragon Plus Environment


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Abstract:

Electropolymerization of 3-amino-1, 2, 4-triazole (ATA) on copper surface was carried out by cyclic voltammetry and the effect of addition of TiO2 on electropolymerization of ATA was investigated. The results of Fourier-Transform Infra-red spectroscopy (FT-IR), Energy Dispersive X-ray analysis (EDX) and X-Ray Diffraction (XRD) analysis of the polymeric composite revealed the presence of TiO2 in the polymeric matrix. Surface morphology of composites was investigated by scanning electron microscopy (SEM). The protection ability of polymeric composites on copper was evaluated by Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization measurements. The results showed that the addition of TiO2 at very low concentrations enhanced the protection ability of p-ATA on copper. This could be due to the synergism between organic polymer and inorganic particles. At higher concentrations of TiO2, the particles are agglomerated and not impregnated into the polymeric matrix of ATA.

Keywords: 3-amino-1, 2, 4-triazole; electropolymerization; TiO2; composite coatings; copper; corrosion protection

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1. Introduction Copper is a promising material used for various applications such as heat conductors, heat exchangers, domestic pipelines, etc., due to its high thermal and electrical conductivity.1 Corrosion of copper takes place significantly in neutral media. Since corrosion plays a dominant role in many industries, researchers have been working to reduce the metallic corrosion and wear costs.2 Generally compounds having heteroatoms such as S, N, O and P serve as good corrosion inhibitors for metals. 3 Especially compounds with nitrogen atoms function as effective corrosion inhibitors as they chelate with metals through the lone pair of electrons.4, 5 Benzotriazole is one of the most efficient corrosion inhibitors for copper and its alloys.6 1, 2, 4-Triazole and its derivatives offer significant corrosion resistance to metallic copper and mild steel.7-12 Electropolymerization is a very simple and efficient technique for the protection of metals such as copper and aluminium.13-15 The incorporation of inorganic particles into polymeric matrix is proved to offer higher protection efficiency to metallic substrates.16-21 Besides, the properties such as microhardness, wear resistance and corrosion resistance are enhanced for the electrodeposited composite coatings.22 The improved property is mainly due to the nature and distribution of the particles in metallic matrix.23 TiO2 is used for various applications such as metallic and organic coatings, as a catalyst and in photovoltaic cells. It is also used to improve the wear resistance, hardness and corrosion resistance properties.24, 25 The formation of insulating thin films through electropolymerization on electrode surface prevents the cathodic or anodic reactions and thereby protects the metallic surfaces from corrosion. Reports are available on the protection of copper by electropolymerized films of pyrrole 26-28 and substituted aniline.29, 30 There have been only a few reports available on the electropolymerization of triazole derivatives for the protection of copper. Electropolymerization of 3-amino-1, 2, 4-triazole (ATA) has been performed on various substrates such as copper, aluminium, brass and platinum.31-35 To the best of our knowledge, there are no reports on the effect of TiO2 on electropolymerization of ATA and its influence on protection of copper. In this work, we have electrosynthesized poly(3-amino-1,2,4-triazole)+TiO2 (p-ATA+TiO2) composite material and evaluated its corrosion protection ability. This work may pave way for the various applications such as photovoltaic cells, batteries, energy storage, electrode surface modification and electrocatalysis. 3



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2.

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Experimental details

2.1. Chemicals 3-amino-1,2,4-triazole (96%) was purchased from Alfa Aesar. TiO2 was purchased from CDH chemicals, Mumbai, India. All the chemicals used were of analytical grade. All the solutions were prepared using deionized water. 2.2. Pretreatment of electrode Cylindrical copper rod with the exposing area of 1 cm2 was used as the working electrode. The electrode was embedded with an epoxy resin. Saturated Calomel Electrode (SCE) and platinum

wire

served

as

reference

and

counter

electrodes

respectively.

Prior

to

electropolymerization, the working electrode was polished with various grades of emery paper and rinsed with acetone. Then the electrode was polished with 0.3 µm alumina/water slurries until a shiny mirror-like finish was obtained. Then it was sonicated in distilled water for 10 minutes to remove residual alumina particles and then introduced into the electrochemical cell. 2.3. Electropolymerization of 3-amino-1, 2, 4-triazole (ATA) Electropolymerization was carried out using 0.2 M ATA in 0.1 M NaOH/methanol solution by cyclic voltammetry (CHI electrochemical analyser model 760D instrument with CHI 760D operating software) and by scanning the potential between – 0.2 to 1.6 V vs SCE at a scan rate of 10 mV/s. Then the modified electrode was dried at 65o C for 30 minutes in air oven for further electrochemical studies. All the potentials reported in this paper were with respect to the SCE. 2.4. Electrosynthesis of p-ATA+TiO2 composite material The mixtures of 0.2 M ATA in NaOH/methanol solution with various concentrations of TiO2 (0.001 M, 0.01 M and 0.1 M) were sonicated for 10 minutes in order to disperse the TiO2 particles in the electrolyte. The composite materials were obtained by the following bath composition: ATA

: 0.2 M

NaOH

: 0.1 M

TiO2

: 0.001 M, 0.01 M and 0.1 M

Scan rate

: 10 mV/s

Potential range

: – 0.2 to 1.6 V

4


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2.5. Characterization of p-ATA+TiO2 composites The FT-IR spectrum of the polymer composite was recorded with JASCO FT-IR 460 plus model in KBr matrix at room temperature. The XRD pattern of the composite coatings was recorded using XRD Bruker D8 advanced with Cu, Kα radiation at the scan range of 0.05o 2Ө with continuous scan type with scan step time of 10.16s. Ni filtered radiation source was about 40 kV, 30 mA with divergence slit size of 0.47 Ao. The surface morphology of the composite material was analyzed by using SEM model VEGA3 TESCAN attached with EDX. 2.6.1

Electrochemical impedance studies The modified copper electrode with and without TiO2 was immersed for about 30 minutes

to attain steady state open circuit potential (OCP) and then evaluated for their corrosion resistance property in 1% NaCl solution by EIS and Tafel polarization measurements. EIS measurements were carried out with a frequency range of 100 KHz to 0.1 Hz with an ac amplitude of 5 mV at OCP. The impedance data were analyzed using EC-Lab SP300 software. From the Nyquist plots, the charge transfer resistance (Rct) and double layer capacitance (Cdl) values were calculated using the appropriate equivalent circuit. From the Rct values, the protection efficiency (PE) was calculated by the following relationship 36

R − Rct ° PE (% ) = ct × 100 Rct where, Rct is the charge transfer resistance in the presence of coating and Rcto is the charge transfer resistance for bare electrode. 2.6.2

Potentiodynamic polarization measurements The potentiodynamic polarization curves were recorded from cathodic to anodic (OCP ±

300 mV) potential with a scan rate of 1 mV/s. From the Tafel polarization curves, the corrosion current density values (icorr) and corrosion potential (Ecorr) were obtained. Using icorr values, the PE was obtained from the following relationship 36

(i ° − icorr ) PE (%) = corr × 100 i corr ° where, icorr is the corrosion current in the presence of coating and icorro is the corrosion current for bare electrode. 5



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3. Results and discussion 3.1 Electropolymerization of ATA in methanol Fig. 1 shows the electropolymerization of 0.2 M ATA in 0.1 M NaOH/methanol solution. The first oxidation peak of monomer appeared at 1.17 V. The second oxidation peak appeared at 0.67 V (Fig. 1 insert). The second oxidation peak was shifted to lower potential than the first one (kinetically easier).37 When the number of scanning cycles was increased, the peak current (ip) values got decreased. The peak current for first oxidation peak was 1.30 mA cm-2, but for the second oxidation peak, the value was decreased to 0.05 mA cm-2. The decrease in peak current, suggested the formation of poly-3-amino-1,2,4-triazole (p-ATA) film over the electrode surface. 31 The polymer formed on the surface protects the anodic dissolution of copper. The peak current tending to zero after three cycles suggested the complete polymerization of ATA as well as the non-conductive nature of the polymer film. 31 Electropolymerization of monomer free 0.1 M NaOH solution is also shown in Fig. 2. This confirmed that the oxidation peak at 1.17 V was mainly due to the ATA. Electropolymerization mechanism of 3-amino-1, 2, 4-triazole was already discussed by Kertit et al., 33 which was shown in Fig. 3. Fig. 1

Fig. 2

Fig. 3

3.2 Electrosynthesis of p-ATA+TiO2 composite material Fig. 4 shows the cyclic voltammograms of 0.2 M ATA in 0.1 M NaOH/methanol solution containing different concentrations of TiO2 (0.001 M, 0.01 M and 0.1 M) at a scan rate of 10 mV/s, by scanning the potential between – 0.2 to 1.6 V vs SCE. On increasing the concentrations of TiO2 from 10-3 M to 10-1 M, the peak current also increased from 1.41 Acm-2 to 1.48 Acm-2. This trend has been reported by earlier researchers’ also.38 The increase in peak current could be attributed to the enhancement of electron transfer in the presence of TiO2. Addition of TiO2 caused the shift of oxidation potential to more positive values. The peak current (ip) value was maximum for the higher concentration of TiO2 (10-1 M). The formation of homogeneous films on copper surface depends on the amount of TiO2 incorporated into polymeric matrix. It is likely that at low concentrations, the TiO2 particles get impregnated into the porous structure of p-ATA. At high concentrations, the particles are agglomerated and are not impregnated into the polymeric matrix of p-ATA. Fig. 4

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3.3 FT-IR studies Fig. 5 shows the FT-IR spectrum of p-ATA, bare TiO2 and p-ATA+TiO2 composites. The characteristic bands of p-ATA were assigned as follows: 3432 and 2857 cm-1 were due to N-H stretching and C-H stretching respectively. The band at 1021 cm-1 was due to C=N stretching vibration. The bands at 1315 and 1112 cm-1 were due to C-H stretching vibration and C-N stretching vibrations respectively.39 These characteristic bands also appeared for p-ATa+TiO2 composites but were slightly shifted due to the interaction of TiO2 with p-ATA. For bare TiO2, the strong absorption at 686 cm-1 could be obtained due to Ti-O stretching.40 This band appeared weak in the IR spectrum of the composite. Fig. 5 3.4 XRD studies Fig. 6 (a) shows the XRD pattern of p-ATA. A broad peak around 25o could be due to the polymer. Fig. 6 (b) shows the XRD pattern of p-ATA+TiO2 composites. The 2Ө values at 37o, 47o and 55o showed the presence of Ti in the polymeric matrix

14

and these values proved that the

crystalline behaviour of TiO2 particles was not affected during impregnation into polymeric matrix. Fig. 6 3.5 EIS Studies Electrochemical impedance spectroscopy is one of the simple and reliable techniques for corrosion measurements. Reports are available on the use of EIS for the characterization of organic coatings.41 EIS techniques can provide valuable mechanistic and kinetic information on electrode surface.42 The Nyquist diagram was fitted with the appropriate equivalent circuit shown in Fig. 7 using a simplex method, where Rs is the solution resistance between the working and reference electrode. C1 is the double layer capacitance (Cdl) at the working electrode/electrolyte interface. R1 is the charge transfer resistance (Rct). R2 is the resistance of CuCl2 complex formed on copper surface. Q1 is the constant phase element of metal/solution interface. The polarization resistance (Rp) can be calculated from the following relationship Rp = R1+R2.43 The Nyquist diagrams for p-ATA and p-ATA+TiO2 composites on copper electrode in 1% NaCl solution are shown in Fig. 8. The fitted Nyquist diagram for p-ATA+TiO2 is shown in Fig. 9. 7



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The quality of fitting to the suggested equivalent circuit was evaluated by the chi-square (χ2) value. The obtained χ2 values are listed in Table 1. It is observed that there is a good agreement between experimental results and the values obtained from the suggested equivalent circuit model.44 The ‘n’ value is associated with the roughness of the electrode. Lower value of n indicates the roughness of the electrode surface. Fig. 7

Fig. 8

As can be seen from the Table 1, the Rct value for bare copper was 525 Ω cm-2. It increased very much when coated with p-ATA. On the addition of TiO2, the charge transfer resistance values were further increased. For p-ATA+10-3 M TiO2 composite, the charge transfer resistance values increased to 45243 Ω cm-2. At low concentration of TiO2, the composites showed higher protection ability in 1% NaCl solution due to the ease of impregnation of TiO2 into the polymeric matrix. The formation of protective layer on copper surface was confirmed by the decrease in double layer capacitance (Cdl) values. The impedance diagram showed a semi-circle in the high frequency region, which is the characteristic of a charge transfer process.45 The diameter of semi-circle increased with the decrease of TiO2 concentration and this supports the decrease in conduction and increase in charge transfer resistance. From these results, it is clear that at low concentrations of TiO2; the dispersion of TiO2 into the polymeric matrix was enhanced thereby protecting the electrode surface more efficiently. The impedance parameters derived from Nyquist plots are shown in Table 1. Polarization resistance values were also increased for p-ATA+10-3 M TiO2 composite. Table 1 Results of the Nyquist plot reveal that the addition of TiO2 to p-ATA caused notable changes in the electrochemical behavior of p-ATA. It could be noted from Fig. 8 that, the nature of the impedance response obtained for various concentrations of TiO2 did not affect the kinetic process of the electropolymerization. This may be due to the non-electroactivity and insolubility of TiO2 in the electrolyte. Conversely, the increase of peak current in the cyclic voltammogram was due to the capacitive effect of the specific surface which becomes more significant and more permeable.38 Fig. 9

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It is known that the corrosion of copper in the presence of chloride ions increases with time due to the dissolution of copper ions. 46, 47 Cu Cu +

Fast

Cu +

Slow

+ e

Cu 2+ + e

The cuprous chloride (CuCl) is formed readily on copper surface by the reaction of Cu2+ ion with Cl- ion in the solution. 48 Cu + + Cl

CuCl

The formed CuCl layer on copper surface does not provide enough protection and it is

-

converted into soluble copper chloride complex, CuCl2 . 46, 47 CuCl + Cl

CuCl2

-

The formed CuCl2 complex is liable for copper corrosion due to its solubility in the bulk solution 49 or its further oxidation to cupric ions. 48, 50 CuCl2

(Surface)

CuCl2

CuCl2

(Solution)

Cu 2+ + 2 Cl

(Solution) + e

3.6 Potentiodynamic polarization studies Fig. 10 shows the Tafel polarization curves for p-ATA+TiO2 (various concentrations) in 1% NaCl solution. The corrosion parameters such as corrosion potential (Ecorr), corrosion current density (icorr), anodic Tafel slope (ba) and cathodic Tafel slope (bc) which are derived from these curves are shown in Table 2. The icorr value for bare copper electrode in 1% NaCl solution was 97.94 µA cm-2, while it got decreased to 18.4 µA cm-2, when coated with p-ATA. The icorr value was decreased further for p-ATA+10-3 M TiO2 when compared to the other two concentrations of TiO2 (10-2 M and 10-1M). The decreased values of corrosion current suggested the formation of protective layer on electrode surface thereby preventing the electron transfer from solution to metal.51 The Ecorr values were shifted to more negative values for composite materials when compared to bare copper electrode. It suggests that the polymeric composites predominantly prevent cathodic reactions. From the variations in ba and bc values, it can be concluded that the coatings prevent both the anodic and cathodic reactions. The improved efficiency of composite coatings was due to the synergism between the organic polymer and inorganic particles.52 9



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Fig. 10

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Table 2

3.7 Surface morphology and elemental analysis The surface morphology of p-ATA and p-ATA+TiO2 composites were characterized by SEM analysis. Fig. 11(a) shows the SEM images of bare copper electrode. There are some scratches in the bare electrode, this may happen during the cleaning process of electrode. As can be seen from the Fig. 11(b), the surface was protected due to the polymer film of p-ATA. Fig. 11(c) shows the SEM images of p-ATA+TiO2 composites. This strongly suggests the incorporation of TiO2 particles in the polymeric matrix. The average particle size of TiO2 is 0.67 µm. As evident from SEM images, the surface morphology was significantly changed after the incorporation of TiO2 particles into the polymeric matrix. EDX spectra of bare copper electrode are shown in Fig. 12(a). The incorporation of TiO2 particles into the polymeric matrix was also confirmed by EDX analysis. The intense peak at 0.40 KeV (Fig. 12(b)) confirms the presence of Ti. The other peaks at 0.4 KeV and 0.25 KeV are related to N and C respectively.38 The incorporation of TiO2 particles into the polymeric matrix during the electropolymerization of ATA was thus confirmed. Fig. 11

Fig. 12

Conclusions The p-ATA+TiO2 composites have been prepared and studied by cyclic voltammetric method on copper electrode. The peak current was increased with the increase of TiO2 concentration. The addition of TiO2 into p-ATA has increased the rate of electron transfer as evident from the increase of peak current (ip) values. The presence of TiO2 in the polymeric matrix was confirmed by FT-IR, XRD, SEM and EDX. The protection efficiency of polymeric composites was evaluated by EIS and Tafel polarization studies in 1% NaCl solution. The study revealed that incorporation of TiO2 into the polymeric matrix of ATA had significantly increased the protection efficiency of copper upto a specific concentration. The study assumes significance in the context of possible use of p-ATA+TiO2 hybrid composites in applications like solar cells, batteries, photovoltaic cells, etc.,

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Acknowledgement: One of the authors (G.Rajkumar) is thankful to UGC-RFSMS (Research Fellowships in Sciences for Meritorious Students), New Delhi, for the financial assistance and both the authors thank UGC -SAP and authorities of GRI for their help and support.

Figure captions

Fig. 1 Cyclic voltammogram of 0.2 M ATA in 0.1 M NaOH/methanol solution with the scan rate of 10 mV/s, between – 0.2 to 1.6 V vs SCE, a) first cycle and b) after 3 cycles; insert: second oxidation peak Fig. 2 Cyclic voltammogram of monomer free 0.1 M NaOH/methanol solution with the scan rate of 10 mV/s, between – 0.2 to 1.6 V vs SCE Fig. 3 Schematic representation of electropolymerization of ATA on copper electrode Fig. 4 Cyclic voltammograms of 0.2 M ATA in 0.1 M NaOH/methanol solution obtained for different concentrations of TiO2 with the scan rate of 10 mV/s, between – 0.2 to 1.6 V vs SCE Fig. 5 FT-IR spectrum of a) pure TiO2, b) p-ATA and c) p-ATA+ TiO2 composite Fig. 6 XRD pattern of a) p-ATA and b) p-ATA+ 10-3 M TiO2 composite Fig. 7 Suggested equivalent circuit for p-ATA+TiO2 composites Fig. 8 Nyquist plots for p-ATA in the absence and presence of different concentrations of TiO2 in 1% NaCl solution; insert: Nyquist plot of bare copper electrode Fig. 9 Fitted Nyquist diagram for p-ATA+10-3 M TiO2 in 1% NaCl solution Fig.10 Tafel polarization curves for p-ATA in the absence and presence of different concentrations of TiO2 in 1% NaCl solution Fig. 11 SEM images of a) bare copper b) p-ATA and c) p-ATA+10-3 M TiO2 composite Fig. 12 EDX spectra of a) bare copper and b) p-ATA+10-3 M TiO2 composite

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15



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17



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 1

18


Page 18 of 31

Page 19 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 2

19



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

N

N

NH2

N N

Page 20 of 31

NH

N N

OH

-e

H N

N

NH2

N

NH

N N

N

N N

N

NH

N

NH

N

HN N

N

N

N ne

N

N

N

NH

N

NH

N

HN N

N

N

Fig. 3

20


N n

Polymer

Page 21 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 4

21



120

b

100

c

80

%T

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 31

a

60

40

20

0 4000

3 500

30 00

250 0

2000

Wavenumber cm

1 500 -1

Fig. 5

22


10 00

5 00

Page 23 of 31

50

(a) 2000

Intensity (a.u)

Intensity (a.u)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(b)

1500 1000 500 0

0 10

20

30

40

50

60

70

80

30

2 Theta (deg)

Fig. 6

23


40

50 2 Theta (deg) s

60


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 7

24


Page 24 of 31

Page 25 of 31

10,000

8,000 -Im (Z )/O h m

6,000 180 160

4,000

140 120 - I m (Z ) / O h m

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


100 80 60

2,000

40 20 100

200

300 Re(Z)/Ohm

5,000

10,000 Re(Z)/Ohm

Fig. 8

25


400


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Fig. 9

26


Page 26 of 31

Page 27 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Fig. 10

27



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(a)

(b)

(c)

Fig. 11

28


Page 28 of 31

Page 29 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(a)

Fig. 12

29



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 31

Table 1. Impedance parameters of p-ATA with and without TiO2 in 1 % NaCl medium

Material

Rs

Rp

Q1

(Ω

(Ω

(µF

cm-2) cm-2) Bare

n

R1

R2

(Ω cm- (Ω cm-2

cm-2)

2

C1

χ2

(µF

x10-2

)

)

cm-2)

PE (%)

14

660

12444

0.5651

525

--

98.0

0.0436

---

p- ATA

152

11169

42.18

0.4257

11246

77.56

1.53

3.625

95.3

p- ATA+10-1 M TiO2

178

16447

22.89

0.5448

16415

32.49

1.33

1.214

96.8

p- ATA+10-2 M TiO2

185

22443

12.72

0.5974

22362

81.97

0.95

1.177

97.6

p- ATA+10-3 M TiO2

194

45303

10.09

0.6228

45243

60.19

0.92

1.535

98.8

30


Page 31 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 2. Potentiodynamic polarization parameters of p-ATA with and without TiO2 in 1 % NaCl medium

- Ecorr

icorr

Material

ba (mV

bc (mV dec-1)

PE (%)

(mV)

(µAcm )

dec-1)

Bare

34.0

97.94

180.41

165.86

---

p- ATA

126.4

18.4

97.36

175.77

81.2

p- ATA+10-1 M TiO2

170.1

6.04

135.09

215.61

93.8

p- ATA+10-2 M TiO2

122.0

3.034

135.33

227.01

96.9

p- ATA+10-3 M TiO2

114.7

0.982

77.33

187.82

98.9

-2

31


Electrosynthesis of a Novel Poly(3-amino-1,2,4-triazole) - American

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