Ebadzadeh, T.

Fateminia, M.

Raissi, B.

Sadeghi, A.A.

Electronic Sumy State University Institutional Repository

46                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I              ELECTROPHORETIC DEPOSITION OF TiO2 NANO-PARTICLES: A COMPARISONBETWEEN THE  PATTERNS OBTAINED IN METHANOL AND PENTANOL T. Ebadzadeh1*, A. A. Sadeghi1, B. Raissi2, M. Fateminia1  1 Ceramic department, Material and EnergyResearchCenter, Karaj, Iran 2 Nanotechnology and Advanced material Department, Material and EnergyResearchCenter, Karaj, Iran  ABSTRACT In the present study, the effect of two organic solvents, metanol and pentanol, on the deposition pattern of electrophoretically deposited TiO2 nano-particles was investi-gated. Characterization of the obtained layer by scanning electron microscope (SEM) and optical microscope (OM) showed that a non-uniform porous layer was obtained when using methanol,  however, a deposition from the TiO2/pentanol cell resulted in the formation of a relatively uniform microstructure. The difference between deposited layers was attributed to considerably high deposition rate of TiO2 nano-particles in methanol as well as the formation of large aggregates within the medium over time.  Key words: electrophoretic deposition, uniform layer, methanol, pentanol  INTRODUCTION The electrophoretic deposition has recently become one of the most prom-ising techniques for producing thin and thick ceramic layers for both experi-mental and industrial applications. In EPD process, charged ceramic particles dispersed in a liquid medium migrate towards an electrode of the opposite charge and consequently get deposited there under the influence of a DC elec-tric field. The process has advantages such as simple apparatus, low process costs, uniformity of the deposited layer, short formation time and etc [1,2]. In general, non-aqueous liquids are preferred to water as the suspending medium, because it eliminates the electrode reaction and gas evolution commonly en-countered due to electrolysis of water on application of electric field [3]. How-ever, as previously reported by Panigrahi et al. [3], different deposition micro-structures are obtained from different organic media. In this paper, considering the numerous applications of TiO2 films in photocatalysis, gas sensors, organic light emitting diodes and dye sensitized solar cells, the effect of two organic solvents, methanol and pentanol, onthe microstructure of the electrophoretically deposited TiO2 films has been investigated.                                                  * e-mail: t-ebadzadeh@merc.ac.ir, Tel: (+98-912)1596944 Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I              47  METHODS OF SAMPLE MANUFACTURING AND ANALYSIS The organic solvents used in this study were purchased from Merck and used without further purification. Two suspensions of TiO2nano-particles (De-gussa P25) in methanol and pentanol with a concentration of  2 and 4 g/lit,repectivley,  were prepared. Each suspension was first magnetically stirred for 24 h at 25 °C at the rate of 400 rpm and then sonicated for 15 min. The EPD set-up consisted of two copper electrode ( 2.5 × 1.5 cm) positioned at a distance of about 1cm and connected to a DC power supply. In order to evaluate the rate of deposition in each medium, deposition was carried out in different time in-tervals of 30, 60, 90, 120, 150 and 180 s atconstant applied voltage of 50 V. In order to analyze the deposition pattern of the obtained layers, scanning electron microscope (Hitachi.S4160) was used. Also, the quantitative analysis of the thickness of the obtained deposit was explored using optical microscope (OM) BX61.  RESULTS AND DISCUSSION In order to investigate the kinetic of deposition within the two organic media, the variation of deposition yield as a function of time was studied.The obtained results which are illustrated in Fig.  1, basically support Hamaker's linear model of the EPD described by the following equation [4]:   M EtSC  (1)  The quantitative analysis over the thickness  was carried out by optical microscope (cross section). The deposition time needed to obtain a thickness of about 7 µm is 20 and 160 secondsin methanol and pentanol suspention , respec-tively. It indicates that the electrophoretic deposition rate in methanol suspen-tion is eight times higher than that in pentanol suspention.   Fig. 1 – Deposition weight as a function of deposition time 48                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I               Fig. 2 – SEM images of nanocrystalline TiO2 films formed in methanol (left)  &  pentanol (right).       Fig. 3 – Optical microscope images ( cross section) of TiO2 films in methanol suspention (left, 7.9 Pm thickness) and pentanol suspention (right, 7.05 Pm thickness) According to the Smoluchowski’s equation [2], the electrophoretic mobili-ty of the suspended particles depends linearly on the dielectric constant of the fluid and the zeta potential and is inversely proportional to the fluid viscosity. According to the presented data in Table 1, methanol is a less viscous medium with relatively higher dissociation power than pentanol, hence, the particles mobility in methanol is expected to be greatert than in pentanol which would result in a higher deposition rate.   Table 1 –Properties of the organic solvents [6]. Property Methanol Pentanol Dielectric constant 32.6 13.9 Viscosity (mPa.s) o.6 4 Conductivity (ȝS/cm) 3.4 0.2  From Fig. 1, the average deposition rates for methanol and pentanol were derived to be 78 and 12 micrograms per second, respectively. Although the effect of electrophoresis parameters such as voltage on dep-osition pattern has been studied by many researchers, few papers have focused Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I              49  on different microstructures and deposition rates obtained at different organic media. In present study, we did not measure the mobility, however, the signifi-cant difference observed in deposition rates and suspension conductivities ob-viously indicate a higher electrophoretic mobility for TiO2nano-particles in methanol. At high deposition rates and low viscosities, the rapid attraction of suspended particles towards the oppositely charged electrode gives them little chance to be assembled in a close-packed structure. Panigrahi et al.reported high deposition rate and an uneven microstructure for doped ceria micro-powder deposits formed in ethanol. In contrast, the deposition rate in butanol was small and smooth deposits were obtained. High rates of particles deposi-tion result in the random assembly and consequently the formation of nonuni-form films. However, at lower deposition rates, which is a result of lower elec-trophoretic mobility and high viscosity, the particles have enough time to de-posit on uncovered areas next to previously deposited particles to form a uni-form structure. In addition, at low viscosities, large aggregates are formed over time due to frequent particles collisions and the inherent tendency of nano-particles to reduce their surface energy through agglomeration. Thus, it is diffi-cult for large aggregates to deposit in a closepacked structure and a non-uniform microstructure would be obtained. CONCLUSIONS Electrophoretic deposition of TiO2nano-particles from methanol and pen-tanol-based suspensionsresulted in the formation of different patterns. The layer obtained in methanol was characterized to be porous and non-uniform, howev-er, deposition from the TiO2/pentanol cell resulted in the formation of arelative-ly uniform microstructure. The difference is attributed to much higher deposi-tion rate of TiO2nanoparticles in methanol as well as the formation of large aggregates within the medium over time. REFERENCES [1] I. Corni, M.P.  Ryan & A.R. Boccaccini: J. Eur. Ceram.Soc, 2008,Vol 28, Issue 7,P. 1353-1367 [2] L. Besra & M. Liu: Prog. Mater. Sci,2007,Vol 52, Issue 1, P. 1-61. [3] S. Panigrahi, S. Bhattacharjee, L. Besra, B.P. Singh & S.P. Sinha: J. Eur. Ceram. Soc, 2010, vol 30, Issue 5, P. 1097-1103 [4] F. Sun, X. Pang & I. Zhitomirsky: J. Mater. Process. Tech, 2009, vol.209, Issue 3,P. 1597-1606. [5] S. Dor, S. Rühle, A. Ofir, M. Adler, L. Grinis & A. Zaban: Colloid. Surface. Physi-cochem. Eng. Aspect.,Vol 342, Issue 1-3, 2009, P. 70. [6] Handbook of organic solvent properties ,Ian M. Smallwood, 1996. P. 1097-1103.    

Electrophoretic deposition of Ti02 nano-particles: a comparisonbetween the patterns obtained in methanol and pentanol

SocioEconomic Challenges Journal (Sumy State University)

46                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I             
 
ELECTROPHORETIC DEPOSITION OF TiO2 NANO-
PARTICLES: A COMPARISONBETWEEN THE  
PATTERNS OBTAINED IN METHANOL AND PENTANOL 
T. Ebadzadeh1*, A. A. Sadeghi1, B. Raissi2, M. Fateminia1 
 
1 Ceramic department, Material and EnergyResearchCenter, Karaj, Iran 
2 Nanotechnology and Advanced material Department, Material and EnergyResearchCenter, 
Karaj, Iran 
 
ABSTRACT 
In the present study, the effect of two organic solvents, metanol and pentanol, on 
the deposition pattern of electrophoretically deposited TiO2 nano-particles was investi-
gated. Characterization of the obtained layer by scanning electron microscope (SEM) 
and optical microscope (OM) showed that a non-uniform porous layer was obtained 
when using methanol,  however, a deposition from the TiO2/pentanol cell resulted in the 
formation of a relatively uniform microstructure. The difference between deposited 
layers was attributed to considerably high deposition rate of TiO2 nano-particles in 
methanol as well as the formation of large aggregates within the medium over time. 
 
Key words: electrophoretic deposition, uniform layer, methanol, pentanol 
 
INTRODUCTION 
The electrophoretic deposition has recently become one of the most prom-
ising techniques for producing thin and thick ceramic layers for both experi-
mental and industrial applications. In EPD process, charged ceramic particles 
dispersed in a liquid medium migrate towards an electrode of the opposite 
charge and consequently get deposited there under the influence of a DC elec-
tric field. The process has advantages such as simple apparatus, low process 
costs, uniformity of the deposited layer, short formation time and etc [1,2]. In 
general, non-aqueous liquids are preferred to water as the suspending medium, 
because it eliminates the electrode reaction and gas evolution commonly en-
countered due to electrolysis of water on application of electric field [3]. How-
ever, as previously reported by Panigrahi et al. [3], different deposition micro-
structures are obtained from different organic media. In this paper, considering 
the numerous applications of TiO2 films in photocatalysis, gas sensors, organic 
light emitting diodes and dye sensitized solar cells, the effect of two organic 
solvents, methanol and pentanol, onthe microstructure of the electrophoretically 
deposited TiO2 films has been investigated.  
 
                                               
* e-mail: t-ebadzadeh@merc.ac.ir, Tel: (+98-912)1596944 
Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I              47 
 
METHODS OF SAMPLE MANUFACTURING AND ANALYSIS 
The organic solvents used in this study were purchased from Merck and 
used without further purification. Two suspensions of TiO2nano-particles (De-
gussa P25) in methanol and pentanol with a concentration of  2 and 4 
g/lit,repectivley,  were prepared. Each suspension was first magnetically stirred 
for 24 h at 25 °C at the rate of 400 rpm and then sonicated for 15 min. The EPD 
set-up consisted of two copper electrode ( 2.5 × 1.5 cm) positioned at a distance 
of about 1cm and connected to a DC power supply. In order to evaluate the rate 
of deposition in each medium, deposition was carried out in different time in-
tervals of 30, 60, 90, 120, 150 and 180 s atconstant applied voltage of 50 V. 
In order to analyze the deposition pattern of the obtained layers, scanning 
electron microscope (Hitachi.S4160) was used. Also, the quantitative analysis 
of the thickness of the obtained deposit was explored using optical microscope 
(OM) BX61.  
RESULTS AND DISCUSSION 
In order to investigate the kinetic of deposition within the two organic 
media, the variation of deposition yield as a function of time was studied.The 
obtained results which are illustrated in Fig.  1, basically support Hamaker's 
linear model of the EPD described by the following equation [4]: 
 
 M EtSC  (1) 
 
The quantitative analysis over the thickness  was carried out by optical 
microscope (cross section). The deposition time needed to obtain a thickness of 
about 7 µm is 20 and 160 secondsin methanol and pentanol suspention , respec-
tively. It indicates that the electrophoretic deposition rate in methanol suspen-
tion is eight times higher than that in pentanol suspention. 
 
 
Fig. 1 – Deposition weight as a function of deposition time 
48                  Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I             
 
 
Fig. 2 – SEM images of nanocrystalline TiO2 films formed in methanol (left)  &  
pentanol (right). 
 
     
Fig. 3 – Optical microscope images ( cross section) of TiO2 films in methanol 
suspention (left, 7.9 Pm thickness) and pentanol suspention (right, 7.05 Pm thickness) 
According to the Smoluchowski’s equation [2], the electrophoretic mobili-
ty of the suspended particles depends linearly on the dielectric constant of the 
fluid and the zeta potential and is inversely proportional to the fluid viscosity. 
According to the presented data in Table 1, methanol is a less viscous medium 
with relatively higher dissociation power than pentanol, hence, the particles 
mobility in methanol is expected to be greatert than in pentanol which would 
result in a higher deposition rate.  
 
Table 1 –Properties of the organic solvents [6]. 
Property Methanol Pentanol 
Dielectric constant 32.6 13.9 
Viscosity (mPa.s) o.6 4 
Conductivity (ȝS/cm) 3.4 0.2 
 
From Fig. 1, the average deposition rates for methanol and pentanol were 
derived to be 78 and 12 micrograms per second, respectively. 
Although the effect of electrophoresis parameters such as voltage on dep-
osition pattern has been studied by many researchers, few papers have focused 
Nanomaterials: Applications and Properties (NAP-2011). Vol. 1, Part I              49 
 
on different microstructures and deposition rates obtained at different organic 
media. In present study, we did not measure the mobility, however, the signifi-
cant difference observed in deposition rates and suspension conductivities ob-
viously indicate a higher electrophoretic mobility for TiO2nano-particles in 
methanol. At high deposition rates and low viscosities, the rapid attraction of 
suspended particles towards the oppositely charged electrode gives them little 
chance to be assembled in a close-packed structure. Panigrahi et al.reported 
high deposition rate and an uneven microstructure for doped ceria micro-
powder deposits formed in ethanol. In contrast, the deposition rate in butanol 
was small and smooth deposits were obtained. High rates of particles deposi-
tion result in the random assembly and consequently the formation of nonuni-
form films. However, at lower deposition rates, which is a result of lower elec-
trophoretic mobility and high viscosity, the particles have enough time to de-
posit on uncovered areas next to previously deposited particles to form a uni-
form structure. In addition, at low viscosities, large aggregates are formed over 
time due to frequent particles collisions and the inherent tendency of nano-
particles to reduce their surface energy through agglomeration. Thus, it is diffi-
cult for large aggregates to deposit in a closepacked structure and a non-
uniform microstructure would be obtained. 
CONCLUSIONS 
Electrophoretic deposition of TiO2nano-particles from methanol and pen-
tanol-based suspensionsresulted in the formation of different patterns. The layer 
obtained in methanol was characterized to be porous and non-uniform, howev-
er, deposition from the TiO2/pentanol cell resulted in the formation of arelative-
ly uniform microstructure. The difference is attributed to much higher deposi-
tion rate of TiO2nanoparticles in methanol as well as the formation of large 
aggregates within the medium over time. 
REFERENCES 
[1] I. Corni, M.P.  Ryan & A.R. Boccaccini: J. Eur. Ceram.Soc, 2008,Vol 28, Issue 
7,P. 1353-1367 
[2] L. Besra & M. Liu: Prog. Mater. Sci,2007,Vol 52, Issue 1, P. 1-61. 
[3] S. Panigrahi, S. Bhattacharjee, L. Besra, B.P. Singh & S.P. Sinha: J. Eur. Ceram. 
Soc, 2010, vol 30, Issue 5, P. 1097-1103 
[4] F. Sun, X. Pang & I. Zhitomirsky: J. Mater. Process. Tech, 2009, vol.209, Issue 
3,P. 1597-1606. 
[5] S. Dor, S. Rühle, A. Ofir, M. Adler, L. Grinis & A. Zaban: Colloid. Surface. Physi-
cochem. Eng. Aspect.,Vol 342, Issue 1-3, 2009, P. 70. 
[6] Handbook of organic solvent properties ,Ian M. Smallwood, 1996. P. 1097-1103. 
 
  


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Electrophoretic deposition of Ti02 nano-particles: a comparisonbetween the patterns obtained in methanol and pentanol

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