Electrophoretic Deposition of Titanium Dioxide (TiO2) Nanoparticles on Ceramic Membrane

Noorsuhana Mohd Yusof1, a and Nurul Hidayah Abdul Aziz 2,b 1,2

Faculty of Chemical Engineering, Universiti Teknologi Mara

noorsuhana@salam.uitm.edu.my, anurulhidayahaziz89@gmail.comb

Keywords: Ceramic membrane, concentration, electrophoretic deposition, TiO2 nanoparticles, suspension, zeta potential.

Abstract: The purpose of this study is to understand the electrophoresis of Titanium dioxide (TiO2)

nanoparticles on ceramic membrane. The ceramic substrate was prepared using commercial ceramic

filter. The effect of different types of solvent used for suspension was studied. Then, the solvent that

give optimum formulation for deposited microstructure on ceramic electrode from the first stage

experiment is used to study the effect of concentration on the deposition behavior of TiO2

nanoparticles during EPD technique. All the TiO2 suspension were had been characterized using

Zetasizer Nano series. The EPD was performed at 20 V DC field for 10 minutes. The deposited of

TiO2 from both stage of experiment were then analyzed using ESEM. The suspension in organic

solvent was found to obtain more deposited particles on ceramic membrane compared to water-based

suspension. While, the concentration with 0.5 wt % TiO2 nanoparticles with zeta potential 53.6 mV

was found to get smaller size and uniform microstructure. The adhesion of the TiO2 deposited layer

from entire of the result on the ceramic electrode was fairly good.

Introduction

Titanium dioxide (TiO2) is important material for electrochemical, catalytic, electronic, paint and

biochemical application, and air purification [8-9]. Nowadays, TiO2 has been utilized to prepare

various type types of nanomaterials due its photocatalytic properties [3]. EPD is a colloidal process

which the motions of charged particles in a stable suspension move under the influence of electric

field toward an electrode of the opposite charge [7]. EPD technique offers many processing

advantages for the deposition of TiO2 films such as high deposition rate, low cost of equipment, short

formation time, and possibility to deposit on complex substrate [1]. In the EPD process, the deposited

microstructure is depending on process parameters such as applied voltage, deposition time,

suspension composition and surface modifying additives[2]. Among this parameter, suspension

formulation is regarded as a key parameter affecting the deposition quality [3].

Recently nonmetallic solid has been increasing interested to be use instead of metal substrate. Dor

et al. and Sadeghi et al. had been deposited TiO2 on glass substrate [4, 8]. On the other studies by

Kreethawate et al. was used porous ceramic tube to obtain polypyrrole (Ppy) coating [7]. The

different substrates give the different results on adhesion strength of particles to the substrate. Thus,

in order to control of film characteristics the deposition factor such as choose the suitable solvent

media and formulation of stable suspension is important to ensure high electrophoretic mobility and

to control porosity, thickness of film and control the defect on electrodeposition image [1]. The effect

between the used of aqueous and non aqueous for TiO2 suspension used for TiO2 nanoparticles

suspension is investigate for EPD application on ceramic electrode. Then, the second goal of this

study is to investigate the effect of concentration of the TiO2 suspension to the surface morphology on

the ceramic membrane surface by ESEM.

Methodology

The experimental work of this project consists of two stages. The first stage was to study the effect of

the different types of solvent used for preparation of TiO2 nanoparticles suspension. Two components

for TiO2 suspension was varied by using organic solvent and water, respectively. After that, the

Advanced Materials Research Vol. 974 (2014) pp 20-25 Submitted: 09.05.2014Online available since 2014/Jun/19 at www.scientific.net Accepted: 09.05.2014© (2014) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.974.20

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second stage of experimental work was run to investigate the effect of concentration of suspension to

the morphology and deposition yield on the ceramic membrane surface.

Preparation of 0.1 wt % TiO2 suspension. Aqueous suspension was prepared by mixing 0.15 g

TiO2 (Degusa 25) with 150 ml deionised water .0.4 ml acetylacetone were added as additive to

improve stability of suspension. Mixtures were then magnetically stirred for approximately 24 hour.

After that, the suspension of TiO2 was homogenized by ultrasonicater in water bath for 30 minutes at

room temperature. For non- aqueous suspension, TiO2 suspension was prepared by mixing 0.21 g of

TiO2 with 150 ml ethanol and 0.4 ml acetylacetone and covered with aluminium foil to avoid

suspension from evaporated [4]. Mixtures were then magnetically stirred for approximately 24 hour

before added with charging solution. Charging solution been prepared by mixing 4 ml of acetone

with 2ml of de-ionised water and 27 mg of iodine powder dissolved in 100 ml of ethanol [5]. The

suspension then was homogenized for 30 minutes by ultrasonicater in water bath model Elmasonic S

180H. Suspension parameters of particle size in suspension and the surface charge condition on the

surface of the suspended particles was analyzed using Nano Zetasizer Series Instrument.

Electrophoretic deposition (EPD) of TiO2 suspension. The ceramic electrode were prepared using

commercial ceramic filter. Ceramic substrate were prepared by cutting with a standard dimension of

1.5 mm width, 5mm length and 25 mm height. Then, its been treated in a pretreatment stage by using

acetone and mild soap. Prior before EPD, prepared ceramic substrates were been weighted. At the

end, the treated substrates were then submerged into the prepared media by a distance of 25 mm

distance. EPD set-up with a constant DC voltage of 20V was applied for 10 minutes of deposition

time using an in-house built circuit. The applied voltage was maintained during the slow extraction of

the working electrode from the suspension to minimize coating removal. Electrical contact to the

electrodes was made according to experimental set-up shown in Figure 1. After EPD, the deposited

substrates were dried using Venticell dryer at 60°C for 24 hours. The morphology of dried deposit

particles for each substrate was characterized by using Environmental Scanning Electron Microscopy

(ESEM).

Fig 1: EPD set-up

Preparation of 0.1, 0.5 and 1.0 wt % TiO2 in ethanol suspension

0.1 wt%, 0.5 wt% and 1.0 wt% of the TiO2 powder in the ethanol solution were prepared by followed

non-aquoues preparation procedures. EPD with a constant DC voltage of 20V was applied for 10 min

of deposition time using an in-house built circuit. The morphology of deposite microstructure was

characterized by using ESEM. The results from ESEM were compared.

Result and Discussion

The effects of different types of solvent. The zeta potential and average particles size obtained from

the analysis was summarizing in Table 1 is based on result obtained for different types of solvent in

Fig 2. The zeta potential value is -21.2 mV for water suspension. The negatively charged of TiO2

suspensions will migrate toward the electrode of opposite charge which is at anode [4]. Therefore, the

anodic depositions tend to occurred. From Table 3, the deposition of electrode in water suspension

25 mm

TiO2

suspension

Advanced Materials Research Vol. 974 21

has a significant increased in weight in anode electrode. The increasing of weight is too slightly at

electrode cathode which almost zero.

While, the zeta potential value in ethanol suspension as shown in Fig.2(c) is 23.7 mV. The positive

value indicates that the sample is in acidic. This suspension condition will contribute to the adsorption

of the H+ ions onto the particle surfaces which improves the electrostatic repulsion force [5]. The

weight of deposited TiO2 at electrode cathode is more significant. As comparing result in Table 3, the

deposition yield is higher in organic suspension. But the increasing of weight for both suspensions is

too slightly. From Fig.2 (b) and 2(d), there are only slightly different in size for both suspensions.

However, in comparison, the organic suspension result in smaller size compared to water suspension.

The obvious different effect both suspensions is the direction potential at different electrode which

water suspension tends to deposit at anode electrode since obtained negative zeta potential value and

cathode deposition for ethanol suspension.

(a)

(c)

(b)

(d)

Fig 2: Zeta potential and average size distribution graph for TiO2 particles at different solvent ;(a)

zeta potential ,(b) particle size distribution in water-based suspension , (c) zeta potential ,(d) particle

size distribution in ethanol suspension

Table 1: Summary of suspension parameters measured at different solvents based on Fig 2

Suspension Zeta potential [mV] Size distribution [nm]

Water suspension -21.2 381.1

Organic suspension 23.7 326.7

Fig.3 shows the E-SEM images for deposited TiO2 particles on the ceramic electrode for different

types of suspension. Both surface shown the poor deposition quality since the deposited particles on

ceramic surface is not uniform and do not fully covered to surface of electrode. However, as

comparing in Fig.3, the amount particle that deposited on the surface morphology for ethanol

suspension was seen more deposited particles as compared to the surface in water suspension. This

might occur because of instability of water suspension during the EPD experiment. The unstable

particles in water tend to settling by gravity during conducting EPD [6]. In addition, the charging

solution did not added in water-based suspension formulation. Charging agent is one of the factors

affect the stability of the suspension. According to Grinis et al, charging agent is important parameter

for high quality of suspension due to the addition of charging agent leads to formation of free H+ [5].

Therefore, the water suspension gives poor deposition yield at ceramic electrode as compared to

22 Material and Manufacturing Technology V

organic suspension. Although the use of water-based suspensions has economical and environmental

advantages over the use of organic solvent, but the quality the deposited surface is affected [10].

Fig.3: The microstructure of the deposited TiO2 in different type of suspension: (a) water, and (b)

ethanol suspension

The effects of TiO2 concentration. From the Table 2, all positive zeta potential values obtained

indicate that the samples will be deposited at cathode cell. The higher positive zeta potential is at

concentration 0.5 wt % and increasing the concentration tends to increase the particle size. The

suspension with 1.0 wt % has the smallest zeta potential. The attraction exceeds repulsion for low zeta

potential suspension. Therefore, the dispersion will break and flocculate to form bigger particles

which are 1837 nm. In other words, the suspension in higher concentration was not stable due to

higher tendency for flocculation [3].

Table 2: Summary of suspension parameters measured at different concentration based on Fig.2

Concentration Zeta potential [mV] Size distribution [nm]

0.1 wt% 23.7 326.7

0.5 wt% 53.6 562.5

1.0 wt % 7.92 1837

From Fig. 4(a), the deposited microstructure shows the lot of uncovered space and deposited

particle were observed in huge size. The deposition seems to be agglomerate at the certain part of

ceramic surface. This might occur because of instability of suspension during the EPD experiment.

From table 4, the suspension in 0.1 wt%, the positively charged of suspensions are not strong enough

to deposit to the cathode is one of the reason to the slightly increased to the electrode cathode weight.

Fig.4(b) shows a more homogeneous and uniform microstructure on the ceramic substrate 0.5 wt %

concentration. The size of particles is smaller. At higher concentration, the formation of nonuniform

particle in the deposited TiO2 is shown in Fig.4(c). At higher concentration, the microstructure was

seen bigger and non uniform in size. The particles were aggregated to produce bigger particles as the

concentration of particles is increased [6]. Analysis from fig.4 shows that the best deposited

microstructure to occur is at 0.5 wt %.

The results indicate that the suspension is in stable condition. Increasing the concentration was

increased the amount of TiO2 deposited and formation of agglomerates. Particle tends to agglomerate

at higher concentration. Therefore, the concentration is important consideration for improved the

stability of suspension for EPD as it will give a significant result.

Advanced Materials Research Vol. 974 23

(a)

Fig. 4 : The microstructure of the deposited TiO2 at different concentration : (a) 0.1 wt % ,( b) 0.5 wt

% , and (c) 1.0 wt % in ethanol suspension.

The types of solvent give a significant effect towards the deposition of TiO2 particles on ceramic

substrate. The potential for deposition electrode varies with types of solvent used. For water-based

suspension, the anodic EPD tend to occur while for suspension in ethanol shows the deposition at

cathode electrode. Positive and negative zeta potential values give the initial indicator for the

deposition types. The suspension in organic solvent was found to obtain more deposited particles on

ceramic membrane compared to water-based suspension. Future works was recommend to improved

the stability of TiO2 suspension by using poly(acrylic) acid (PAA) in aqueous suspension for better

deposition in aqueous suspension [8].For the effect of concentration, higher concentration tends to

produce bigger particles and agglomerates [4]. Too lower zeta potential value tends to contribute to

unstable suspension where the suspensions easily flocculate. 0.5 wt% can be conclude as optimum

concentration for deposition of TiO2 on ceramic electrode which obtained more uniform

microstructure surface.

Acknowledgements

The authors would like to acknowledge Universiti Teknologi MARA for Research Intensive Faculty

(RIF) Project number 600-RMI/DANA 5/3/RIF (317/2012) for the financial support to carry out this

research. Authors also, thankful to the staff of Faculty of Pharmacy, Universiti Teknologi MARA,

Puncak Alam for their help in FESEM-EDS and TEM analysis.

(c)

(c)

(b)

24 Material and Manufacturing Technology V

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Material and Manufacturing Technology V 10.4028/www.scientific.net/AMR.974 Electrophoretic Deposition of Titanium Dioxide (TiO2) Nanoparticles on Ceramic Membrane 10.4028/www.scientific.net/AMR.974.20

DOI References

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http://dx.doi.org/10.1016/j.ceramint.2013.02.087