Carbon nanotubes (CNTs) have attracted great attention because of their unique structural, electrical, mechanical and thermal properties. Then CNTs have potential application as electrode for batteries and supercapacitors, especially binder-free electrodes. The major challenge is to fabricate the large scale electrode with the uniform thickness, electrical property. The large scale CNTs buckypaper can be fabricated via vacuum filtration technique. The characteristics of CNT dispersion and buckypaper depend on variety of factor such as sonication power, sonication time, dispersant…. In this study, we investigate the multiwall carbon nanotubes (MW CNTs) in Isopropanol (IPA) solvent with different sonication conditions, membrane filter size for paper with areal density of 3 mg/cm2 with different sizes such as 4, 10, 20 cm in diameter and large scale of 30x30 cm2. It is observed that the dispersion of CNTs are good and the thickness, conductivity are uniform over whole sample for above sizes. We also can get the highest conductivity of buckypaper was 3.9x103 S/m in 30 mins. It is found that the higher sonication power and higher sonication time are better for buckypaper

Do, Quyet Huu

Ngo, Thanh Vo Ke

Nguyen, My Khanh

Nguyen, Tham Thi Hong

Tieu, Doanh Tu

Vietnam Academy of Science and Technology: Journals Online

Communications in Physics, Vol. 28, No. 3 (2018), pp. 217-224
DOI:10.15625/0868-3166/28/3/10758
STUDY TO FABRICATE THE LARGE SCALE BUCKYPAPER BASED ON
CARBON NANOTUBES
DOANH TU TIEU1, MY KHANH NGUYEN3, THAM THI HONG NGUYEN1,
THANH VO KE NGO1,2 AND QUYET HUU DO1,†
1Sai Gon Hi Tech Park Labs, Sai Gon Hi Tech Park, District 9, Ho Chi Minh City, Vietnam
2Institute for Computational Science and Technology,
SBI building, Quang Trung Software City, Tan Chanh Hiep ward, district 12, Ho Chi Minh city,
Vietnam
3University of Natural Science, 227 Nguyen Van Cu, District 5, Ho Chi Minh City, Vietnam
†E-mail: quyet.dohuu@shtplabs.org
Received 25 September 2017
Accepted for publication 20 July 2018
Published 31 August 2018
Abstract. Carbon nanotubes (CNTs) have attracted great attention because of their unique struc-
tural, electrical, mechanical and thermal properties. Then CNTs have potential application as
thermal pads, electrodes for batteries and supercapacitors, especially binder-free electrodes. The
major challenge is to fabricate the large scale electrode with the uniform thickness, electrical
property. The large scale CNTs buckypaper can be fabricated via vacuum filtration technique.
The characteristics of CNT dispersion and buckypaper depend on variety of factor such as son-
ication power, sonication time, dispersant. . . . In this study, we investigate the multiwall carbon
nanotubes (MW CNTs) in IsoPropanol (IPA) solvent with different sonication conditions, mem-
brane filter size for paper with areal density of 3 mg/cm2 with different sizes such as 4, 10, 20 cm
in diameter and large scale of 30× 30 cm2. It is observed that the dispersion of CNTs are good
and the thickness, conductivity are uniform over whole sample for above sizes. We also can get
the highest conductivity of buckypaper was 3.9×103 S/m in 30 minutes. It is found that the higher
sonication power and higher sonication time are better for buckypaper.
Keywords: carbon nanotubes, buckypaper, buckypaper electrode, membrane filtration, porous
structure.
Classification numbers: 61.48.De.
c©2018 Vietnam Academy of Science and Technology
218 STUDY TO FABRICATE THE LARGE SCALE BUCKYPAPER BASED ON CARBON NANOTUBES
I. INTRODUCTION
Carbon nanotubes have attracted great attention because of their unique structural, electri-
cal, mechanical and thermal properties [1, 2]. Buckypapers are thin films formed with dispersed
network of CNTs. Now, techniques for fabricating buckypaper can be classified into dry and wet
approaches. The dry approaches include the direct in situ chemical vapor deposition (CVD) grow-
ing, domino pushing [3] and shear pressing [4]. These approaches give structural perfection but
less degree of CNTs agglomeration. On the other hand, the wet approaches such as membrane
filtration [4–7], drop casting [8, 9], spin-coating [10] and electrophoresis deposition [11, 12] are
more attractive due to cost effectively scaled up. In this wet approach, membrane filtration tech-
nique is often used as 1) it is the easy and simple process, 2) it can control thickness of buckypaper
precisely 3) it can be mixed with carbon family such as graphene, graphite, carbon nano-fibers and
4) it can be scaled up. This technique involves dispersion solution and usually added the surfac-
tant as Triton X-100 or Sodium Lauryl Sufate in order to improve the dispersion ability. However,
when the buckypaper was successfully fabricated, we need to remove the residual surfactant from
it. This way can break or even destroy the buckypaper. Besides, the surfactant linked into CNTs
matrix will reduce buckypaper properties such as decrease the electrical, thermal conductivity.
In this work, we use the membrane filtration method to fabricate the buckypaper without
adding the surfactant into solution in order to avoid the above problems [13] . We will study the
the affecting factors such as sonication (power and time), membrane filter size to get the highest
quality of the buckypaper.
II. EXPERIMENT
II.1. Buckypaper fabrication
A buckypaper is a network of CNTs in the form of thin film, fabricated by dispersion and
filtration. The CNTs were purchased from Cheaptube, Inc (USA) and poured into the IPA solution.
Then the mixture was dispensed by high power sonicator UIP 1000HD (Germany) with different
power and time. We also fabricate the buckypaper with different size 4, 10, 20 cm diameter and
30×30 cm2 square with area density 3 mg/cm2. After the solution filtration, the buckypaper was
dried at room temperature in few hours to evaporate the IPA and brought to characterization.
II.2. Characterization
Morphologies of the raw CNTs and Buckypaper were investigated using the Field Emisson
Scanning Electron Microscope (FE SEM S4800, Hitachi) with an accelerating voltage of 10kV.
With FE SEM images, we can see how the agglomerative level of CNTs net-work. The thickness of
buckypaper was measured by Micrometer Mitutoyo. Electrical conductivity of the buckypaper was
obtained by Four - point probe method (Jandel Model MWP-8). The Quantachrome Instruments
Nova 1000 e (USA) is used to analyze the surface area of the sample.
III. RESULTS AND DISCUSSION
The raw CNTs were characterized by FE SEM to characterize before they were used to
fabricate the Buckypaper. We saw that the CNTs were uniform in the length about 20 um, diameter
about 10-20 nm and high purity in Fig. 1. The pictures of buckypaper samples with small diameter
of 4 cm and larger size of 30×30 cm2 were shown in Fig. 2.
DOANH TU TIEU et al. 219
Fig. 1. The FE SEM images of the raw CNTs purchasing from manufacturer.
(a) (b)
Fig. 2. The pictures of Buckypaper samples with different sizes a) 4 cm diameter; b)
30×30 cm2 square.
III.1. Micro-mophologies of the Buckypaper
In the sonication process, the CNTs were not be shortened or destroyed although the time
sonication increased from 10, 20 to 30 minutes or the power sonication was 500, 700, 900 and
highest power 1000 W, respectively. This showed that these sonication time and power do not
affect to the CNTs quality and Buckypaper as well in Figs. 3-4. It means with these sonication
time less than or equal 30 minutes and power 1000 W do not affect to the CNTs quality and
Buckypaper. If the sonication time is more than 30 minutes, the CNTs will be shortend in Figs.
5-6, which will degrade the both CNTs quality and Buckypaper.
220 STUDY TO FABRICATE THE LARGE SCALE BUCKYPAPER BASED ON CARBON NANOTUBES
(a)
(b)
(c)
Fig. 3. The FE SEM images of Buckypaper samples fabricated by vacuum filtration tech-
nique with varied sonication time a) 10 minutes; b) 20 minutes; and c) 30 minutes.
DOANH TU TIEU et al. 221
(a) (b)
(c) (d)
Fig. 4. The FE SEM images of Bukypaper samples fabricated by vacuum filtration tech-
nique with varied sonication power (a) 500 W; (b) 700 W; (c) 900 W; and (d) 1000 W.
5 
 
 
 
 
 
 
 
 
 
Figure 5: The FE SEM images of  shortened CNTs with the sonication time 45 minutes. 
 
 
 
 
 
 
 
 
Figure 6: The FE SEM images of  shortened CNTs with the sonication time 60 minutes. 
 
3.2 Effect of sonication time and power on the properties of Buckypaper 
The Buckypaper’s properties such as the thickness, electrical conductivity and 
surface area are important for battery and supercapacitor electrodes. We investigated the 
different sonication time and power affecting them.  
 We also see that solution of carbon nanotubes is more dispersion with the higher 
time and power sonication. This led the greater de-aggregation of carbon nanotubes and 
we can get smoother surface in Fig. 3 as well as the buckypaper thickness shown in 
Figure 7.  The sonication time 30 minutes is best dispersion ability and agreed with the 
[14]. 
Shortened CNTs 
Shortened CNTs 
Shortened CNTs 
Shortened CNTs 
Fig. 5. The FE SEM images of shortened CNTs with the sonication time 45 minutes.
222 STUDY TO FABRICATE THE LARGE SCALE BUCKYPAPER BASED ON CARBON NANOTUBES
5 
 
 
 
 
 
 
 
 
 
Figure 5: The E SEM images of  shortened CNTs with the sonication time 45 minutes. 
 
 
 
 
 
 
 
 
Figure 6: The FE SEM images of  shortened CNTs with the sonication time 60 minutes. 
 
3.2 Effect of sonication time and power on the properties of Buckypaper 
The Buckypaper’s properties such as the thickness, electrical conductivity and 
surface area are important for battery and supercapacitor electrodes. We investigated the 
different sonication time and power affecting them.  
 We also see that solution of carbon nanotubes is more dispersion with the higher 
time and power sonication. This led the greater de-aggregation of carbon nanotubes and 
we can get smoother surface in Fig. 3 as well as the buckypaper thickness shown in 
Figure 7.  The sonication time 30 minutes is best dispersion ability and agreed with the 
[14]. 
Shortened CNTs 
Shortened CNTs 
Shortened CNTs 
Shortened CNTs 
Fig. 6. The FE SEM images of shortened CNTs with the sonication time 60 minutes.
III.2. Effect of sonication ti er on the properties of Bucky aper
The Buckypaper’s properties such as the thickness, electrical conductivity and surface area
are important for battery and supercapacitor electrodes. We investigated the different sonication
time and power affecting them.
We also see that solution of carbon nanotubes is more dispersion with the higher time
and power sonication. This led the greater de-aggregation of carbon nanotubes and we can get
smoother surface in Fig. 3 as well as the buckypaper thickness shown in Fig. 7. The sonication
time 30 minutes is best dispersion ability and agreed with the [14].
Fig. 7. The plot showed the effect of the sonication time and power on the Buckypaper thickness.
Besides, the sonication time and power effect on the electrical property of Buckypaper. The
conductivity of Buckypaper is better with the higher time and power sonication. This explained
that the carbon nanotube solution is more dispersion ability and leads the good de-aggregation
and uniform distribution. This confirms again that the time sonication 30 minutes was for best
DOANH TU TIEU et al. 223
solution dispersion and gave the saturation electrical conductivity 3.9×103 S/m for 700, 900 and
1000 W power sonication for both small and large scale Buckypaper shown in Fig. 8. The Table 1
summarizes the fabrication conditions and results for Buckypaper.
Fig. 8. The plot showed the effect of the sonication time and power on the Buckypapers
electrical conductivity.
Table 1. The FE SEM images of the raw CNTs purchasing from manufacturer.
Sonication Sonication Thickness Electrical
Sample Power Time (µm) Conductivity
S(W) (minutes) (103 S/m)
1 500
10
220 1
2 700 140 1.7
3 900 96 3.0
4 1000 100 3.6
5 500
20
198 1.2
6 700 84 3.7
7 900 88 3.6
8 1000 85 3.7
9 500
30
152 1.8
10 700 85 3.9
11 900 85 3.9
12 1000 70 3.9
As buckypaper is used for electrode for supercapacitor so the surface are is important fac-
tor, showing the ability to store energy. Three samples no. 10, 11 and 12 in Table 1 showing
the highest conductivity are brought to characterize. The surface area results are 200, 208 and
224 STUDY TO FABRICATE THE LARGE SCALE BUCKYPAPER BASED ON CARBON NANOTUBES
210 m2/g, respectively. Again this explains that the higher sonication time and power make the
carbon nanotube solution more dispersion ability and leads the good de-aggregation so the surface
area is higher.
IV. CONCLUSION
In summary, the MWNT Buckypaper was successfully fabricated by membrane filtration
technique and evaluated. The sonication time is less than or equal 30 mintues and sonication power
is 1000 W do not affect the carbon nanotubes quality. The sonication time 30 minutes gives the best
solution dispersion, electrical conductivity and surface area as well. Additionally, the sonication
power also affects those properties, higher power will result in higher conductivity. With these
properties, Buckypapers can be applied for many potential applications including thermal pads,
battery and supercapacitor electrodes...
ACKNOWLEDMENTS
Thanks the financial support from Ministry of Science and Technology Viet Nam for pro-
posal “Study to fabricate the thin film thermal pad based on buckypaper for applications in the
electrical and electronic devices” with code number D- M.17.NC/16 and the contract No.01/2016/HD- -
CTD- MCN.
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Study to Fabricate the Large Scale Buckypaper Based on Carbon Nanotubes

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