Li, M.

Peng, H.

Zhang, Zhongyi

Zhao, W.

English

Portsmouth University Research Portal (Pure)

 14
TH
  EUROPEAN CONFERENCE ON COMPOSITE MATERIALS 
7-10 June 2010, Budapest, Hungary 
 
Paper ID: 545-ECCM14  
 
1 
 
CARBON NANOTUBE BASED COMPOSITES FILM HEATER  
FOR DE-ICING APPLICATION 
W. Zhao
1
, M. Li
2
, Z. Zhang
3
, H.X. Peng
1*
 
 1
Department of Aerospace Engineering, University of Bristol, BS8 1TR, UK 
 
2
School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK  
3
Mechanical & Design Engineering, University of Portsmouth, Portsmouth, Hants, PO1 3DJ 
                              * H.X.Peng@bristol.ac.uk 
 
Abstract 
Light weight, highly conductive (both electrically and thermally) multiwalled carbon 
nanotube (MWNTs) sheets can be used as an effective electric heating element. In this paper, 
silver nanoparticles were anchored onto carboxyl functionalized multiwalled carbon 
nanotubes (MWNTs) by photochemical reaction to enhance the transport properties of the 
resultant nanohybrid sheet. The nanohybrid sheet was then integrated into the Kevlar/epoxy 
sandwich structure by resin infusion method. When conducting a current through an area of 
24.6×20.7mm, the sample temperature reached the steady-state value (e.g. 110
o
C) within 13s 
by consuming a power density of 0.58W/in
2
. In addition, the laminate structure showed a 
stable reversibility after a number of heating cycles, which indicated it’s potential for thermal 
interface materials, sensors and de-icing applications. 
  
1 Introduction 
To fully explore the excellent properties of carbon nanotubes (CNTs), work in the past has 
been focused on generating CNTs networks, films and sheets (buckypaper) using spraying or 
vacuum infiltrating method [1, 2] onto solid substrates or integrating with polymers. 
Compared with single walled carbon nanotubes (SWNTs), multiwalled carbon nanotubes 
(MWNTs) are much cheaper and better suited to large scale industrial applications exception 
of their much lower conductivity than SWNTs. Dai [3] reported that chemical doping led to 
orders of magnitude reduction in the resistance of bulk SWNT materials due to the increase in 
the average of hole or electron carrier in the  nanotubes. For both SWNT and MWNT sheets, 
there are two predominant nanotube junctions that govern the electrical properties of a 
nanotube network, namely: (1) Y junction – ambipolar behavior and (2) crossed junction-- 
rectification characteristics [4]. Therefore, two approaches can be used to improve the 
electrical conductivity of MWNT sheets: (1) minimize the contact resistance between 
nanotubes by improving the alignment of nanotubes and by increasing the lengths of 
individual tubes; (2) improve the conductivity of individual nanotubes by post-synthesis 
treatments [5]. To achieve low-resistance ohmic contacts in these structures, metals can be 
deposited onto the nanotube surface by using techniques such as, impregnation [6], electroless 
plating [7], self-assembly [8],  electro-deposition [9], and physical vapour deposition [10], 
etc..  
From an engineering perspective, the highly conductive CNTs can be explored for many 
applications, among which one specific application to be addressed in the present work is to 
 14
TH
  EUROPEAN CONFERENCE ON COMPOSITE MATERIALS 
7-10 June 2010, Budapest, Hungary 
 
Paper ID: 545-ECCM14  
 
2 
 
use CNT sheets as a heating element for potential de-icing in aeronautical industry. The 
conventional de-icing heater uses metal foil as the heating element. One disadvantage for the 
metal foil as heating element is that it does not have a good, durable bond to the protecting 
layer. Another disadvantage is that heating may not be uniform, resulting in cold spots which 
hold ice on the airplane, and hot spots which cause the ice to melt and refreeze at different 
sites [11].  A composite-composite bonding in a composite material heater is more uniform 
and stronger than the composite-metal bonding found in conventional de-icers. Good bonding 
of CNT sheet/fabric matrix would result in a much more uniform heating. Due to the high 
electrical conductivity of CNT sheet, heating can be achieved in a relative thin layer (37 μm 
thick in the model heater) without need of high voltages. Therefore the amount of heat 
accumulated by the composite heater is minimized. In addition, electricity can penetrate 
through the heating element in the transverse direction despite the low transverse electrical 
conductivity.  
In the present work, Ag/MWNT hybrid sheets were prepared using silver nanoparticles 
decorated MWNTs and were then integrated into aerospace composites. The resulting 
composites showed a quick temperature response to input power and very stable thermal 
cycles, which could be ideal for de-icing applications.  
2 Experimental Details 
2.1 Silver decorated MWNTs and the MWNT sheets 
The pristine MWNTs (Sigma Aldrich, UK) were produced by chemical vapour deposition 
(CVD), with a purity of > 99 %, up to 20 μm in length and their diameters around 12 nm. 
Pristine MWNTs (4.32 g) were added into hot acid mixture H2SO4/HNO3 (3:1 by volume, 120 
ml) and the mixture was then sonicated in an ultrasonic bath (40 kHz) for 30 minutes before 
stirring for 4 h at a temperature of 100°C. The suspension was diluted with distilled water and 
no sediment was found after a whole night. The resulting solution was then filtered through a 
0.22 μm Millipore alumina membrane and subsequently washed with distilled water until the 
pH value of the filtrate was ca. 7. The filtered solid was dried under vacuum for 24 h at 40°C, 
yielding MWNT-COOH (2.588 g). 100 mg of acid-treated MWNTs were dispersed in 
distilled water in the presence of TX-100 surfactant, and a 250 ml silver nitrate solution (0.2 
wt%) was then added into the MWNTs suspension and stirred under UV light with a wave 
length of 365nm at 60°C. The densely packed MWNT sheets were fabricated by filtering the 
above suspension through Millipore alumina filters and subsequently washed with distilled 
water and ethanol.  
2.2 MWNT sheets integrated laminate composites 
In this study, commercially available Kevlar 129
TM
 fabric and HexPly 914 resin film were 
used in this study and the vacuum assisted resin transfer molding (VARTM) process was used 
to fabricate the laminates embedded with carbon nanotube sheets via the following three 
steps. In the first step, Kevlar fabric, HexPly 914 resin film and carbon nanotube sheets were 
placed on the bottom of an aluminum mold coated with release agent. After the lay-up 
operation was completed, a peel ply, release film, breather, and vacuum bag film were placed 
on the top of Kevlar fabric, see in Figure 1. The vacuum film bag was then sealed around the 
perimeter of the mold and a vacuum pump was used to draw a vacuum within the mold 
cavity. The next step was to put the bagging stuff into oven at 175°C for 75 minutes, during 
which the resin film was melted and sucked into the mold under atmospheric pressure. In the 
 14
TH
  EUROPEAN CONFERENCE ON COMPOSITE MATERIALS 
7-10 June 2010, Budapest, Hungary 
 
Paper ID: 545-ECCM14  
 
3 
 
final step, the composite part was post cured at 190°C for 4 hours (Figure 1). During the 
curing process, the carbon nanotubes sheet experienced the same temperature cycle as the 
baseline laminates. 
 
 
 
 
 
 
Figure 1  (a) Vacuum assisted resin transfer molding (VARTM) setup and (b) Kevlar/MWNT sheet laminate. 
 
Scanning electron microscopy (SEM) was used to characterize the interfacial morphologies of 
the MWNT sheets/Kevlar laminate. The morphologies of nanoparticles decorated MWNTs 
were observed by using transmission electron microscopy (TEM, JEOL 1200). To prepare the 
TEM samples, a tiny drop of well dispersed samples was placed onto the carbon coated TEM 
copper grid.  Copper electrode wires were attached to the MWNT sheet/Kevlar laminate by 
silver paste and the power source was directly connected to the electrode wire. An infrared 
thermal imager (NEC TH9100) was used to record the temperature distribution and evolution 
of the sample with inputting powers.  
3 Results and discussions 
3.1 Morphology of silver decorated MWNTs and their hybrid sheet  
While acid treated MWNTs can supply nucleating sites for Ag nanoparticles, the particle size 
could not be controlled effectively. TX-100 can not only act as surfactant but also help control 
the particle size, as well as acting as reducing agent at the same time. In this experiment, 
silver nanoparticles were synthesized by using the same amount of acid-treated MWNTs in 
the presence of 1vol% of TX-100, and the silver nanoparticles were stabilized onto the 
nanotubes and well dispersed with a narrow size distribution between 20 and 30 nm. This 
Carbon Nanotube Sheet 
Bagging film 
Laminate 
Peel ply 
Release Film 
Breather 
Vacuum gauge 
Release coated Mould 
Sealant 
Tape 
Vacuum Outlet (a) 
(b) 
 14
TH
  EUROPEAN CONFERENCE ON COMPOSITE MATERIALS 
7-10 June 2010, Budapest, Hungary 
 
Paper ID: 545-ECCM14  
 
4 
 
indicated that the TX-100 is necessary in controlling the nanoparticle size, size distribution 
and preventing agglomeration. Although the TEM samples were prepared by dispersing the 
resulting nanohybrids in water using strong sonication, the nanotubes were still tightly 
connected by the nanoparticles to form a conductive path, which is expected to enhance the 
transport properties of the future nanotube sheets, as shown in Figure 2a The silver 
nanoparticles decorated nanotube sheets were prepared using a vacuum infiltration procedure. 
For relatively short carbon nanotube, there is a minimum thickness to keep a free standing 
nanotube sheet, which is 20 µm for MWNTs in this experiment. As shown in Figure 2b, the 
thickness of the MWNT sheet is 37 µm, and it can be tailored depending on the specific 
requirements.  
 
 
   
 
Figure 2 (a) TEM images of Ag/CNT-COOH in the presence of TX100, and (b) silver decorated MWNTs sheets 
37μm. 
 
3.2 Interfacial microstructure investigations 
The nanotube sheets made by silver nanoparticle decorated MWNTs had good strength and 
flexibility to allow for handling like traditional aerospace fabric. The sheet is free standing 
due to the inter-nanotube van der Waals forces and mechanical interlocking within the 
nanotube sheet. Figure 3a showed the SEM image of MWNT sheet embedded in Kevlar 
matrices, indicating a sound interface between Kevlar and MWNT sheets by quite rough 
surface. Also it can be clearly seen that resin had completely penetrated the carbon nanotube 
sheet through the entire thickness direction during the VARTM process and wet well with 
nanotubes (Figure 3b). 
 
(a) (b) 
50mm 50mm 
 14
TH
  EUROPEAN CONFERENCE ON COMPOSITE MATERIALS 
7-10 June 2010, Budapest, Hungary 
 
Paper ID: 545-ECCM14  
 
5 
 
   
 
Figure 3 SEM images of (a) Kevlar laminate with infused MWNT sheet and (b) fracture surface the infused 
sheet area, as indicated by white frame and arrow. 
3.3 Electrical conductive properties 
Knowing that the MWNT heat element in Kevlar was 37 μm thick and 2.10 cm wide, the 
distance between the foil in the middle section of the heater was 2.05 cm, and the voltmeter 
reading was 5v when the resistance was 62.7 Ω, the conductivity of this particular composite 
was calculated to be 430 S/m. The VI characteristics of the MWNT sheet and its 
composites showed linear characteristics, which means they are good conductors even when 
the nanotubes were infused with insulating matrix materials (Figure 4). It is worth mentioning 
that carbon nanotubes are robust under most weather conditions, and show very little change 
in conductivity either at temperature ranging from -20 to 80
o
C [12], or repetitive bending of 
the composite, indicating that it is fairly durable under mechanical distortions. 
 
y = 0.0981x - 0.0184
y = 0.0147x + 0.0009
0
0.1
0.2
0.3
0.4
0.5
0 2 4 6 8
Voltage (V)
C
u
rr
e
n
t 
(A
)
MWNT sheet
Kevlar/MWNT sheet 
 
 
Figure 4 I-V data and fitting curves of MWNT sheets and its composites. 
 
(a) (b) 
 14
TH
  EUROPEAN CONFERENCE ON COMPOSITE MATERIALS 
7-10 June 2010, Budapest, Hungary 
 
Paper ID: 545-ECCM14  
 
6 
 
3.4 Joule-heating behavior of MWNT laminates for de-icing application 
The heater was heated at room environment with varying input voltages. The temperature 
history was monitored by a noncontact IR thermocamera. Temperature as a function of 
heating time was recorded, including ramping up, steady-state and cooling down. As seen in 
Figure 5, the highest temperatures increased consistently with the heating current. 
Consequently, the ramp-up time decreases with increasing highest temperature while the 
cooling down time increases with the highest temperature. Similar phenomenon was also 
found in Ref. [13]. The fast ramp-up and cool-down rate is very promising for de-icing 
application.  
 
 
  
Figure 5  Thermal cycles with 5, 6, 7V of input voltages: stage I, ramping up, stage II: stable-state and stage III: 
cooling down.   
 
 
The equation relating the input power and the heater's resistivity and dimensions is:  
 
WtLIIEPLW /
2      (1) 
 
where, I is the current conducted through the heater, E  is the voltage drop across the heater, 
P is the power per unit area of the heater, , L , W and t  are the resistivity, length, width, 
and thickness of the heater, respectively. It is found that the steady-state temperatures 
increased with more power inputting. It only needed an input power of 0.58W to improve the 
temperature from starting heating to 110°C (Figure 6).  According to the thermal radiation 
images shown from bottom to up, the temperatures are 65 °C, 95°C and 110°C, respectively. 
 
5V 
6V 
7V 
Time/s 
T
e
m
p
e
ra
tu
re
 /
°C
 
Stage II 
Stage III Stage I 
 14
TH
  EUROPEAN CONFERENCE ON COMPOSITE MATERIALS 
7-10 June 2010, Budapest, Hungary 
 
Paper ID: 545-ECCM14  
 
7 
 
 
  
Figure 6 Ultimate temperatures of MWNT sheet/Kevlar laminate with different input powers. 
 
3.5 Thermal conductivity 
For the CNT sheets/Kevlar composites, the values of thermal conductivity are much lower 
than that of the pristine CNT sheets, because the matrix has a much lower thermal 
conductivity (0.2 W/mK) [14]. The thermal conductivities of the composites can be obtained 
from theoretical models, including the rule of mixture and Nan’s model [15]: 
 
fffmc VkVkk )1(      (2) 
)23/()3( fffmc VVkkk      (3) 
 
where ck , mk and fk are the thermal conductivities of composite, epoxy matrix and CNTs, 
respectively. The measured values of mk  and sheetk  are 0.2 W/mK and 200 W/mK, 
respectively [16]. The volume fraction of MWNTs in the composites is 33.0fV  (33 vol.%), 
and the thermal conductivity of the Kevlar/MWNT composite should be between 66.13 and 
28.46 W/mK, according to equation (2) and (3). Aliev reported that the thermal conductivity 
along the aligned CVD-grown MWNT sheet is 50W/mK while the value is 2.1W/mK along 
the transverse alignment direction [17, 18]. Considering the random distribution of nanotubes 
in this study, Nan’s model (28.46 W/mK) gave a better approximation to the true value of the 
conductivity.  
4 Conclusions 
A hybrid laminate consisting of Ag decorated MWNT sheets was prepared by vacuum 
assistant resin transfer method. The presence of Ag nanoparticles has been confirmed by TEM 
and EDX by showing that the narrow particle size distribution silver nanoparticles have 
anchored onto nanotubes to bridge individual nanotube. The SEM characterization shows a 
perfect interface of the laminate and a dense resin infused microstructure. A consistent 
Temperature response of the input voltage
0
20
40
60
80
100
120
0 5 10 15 20 25 30 35 40 45
Time (s)
T
e
m
p
e
r
a
tu
r
e
 (
o
C
)
5V
6V
7V
0.30W/in
2
 
0.426W/in
2
 
0.58W/in
2
 
 14
TH
  EUROPEAN CONFERENCE ON COMPOSITE MATERIALS 
7-10 June 2010, Budapest, Hungary 
 
Paper ID: 545-ECCM14  
 
8 
 
electrical conductivity of 430S/m is obtained and the relatively higher resistance promises a 
fast temperature response to low input powers. The analytical analyses showed that Nan’s 
mode (e.g. 28.46 W/mK) gave a better approximation to the experimental value of the thermal 
conductivity of the hybrid sheets. All these indicate that the MWNT sheets can be used as 
heating elements in de-icing application in aerospace industry. 
Acknowledgement 
WMZ acknowledges the support from Overseas Research Scholarship Award Scheme and the 
University of Bristol Postgraduate Scholarship.  
References 
[1]    Xu, H., et al., Frequency-and electric-field-dependent conductivity of single-walled  
carbon nanotube networks of varying density. Physical Review B, 2008. 77(7): p. 
75418. 
[2] Wu, Z., et al., Transparent, conductive carbon nanotube films. Science. 2004. 
305(5688): p. 1273-1276. 
[3] Dai, H., Carbon nanotubes: opportunities and challenges. Frontiers in surface and 
interface science, 2002. 500: p. 218-241. 
[4] Lee, H.C., et al., Selective metal pattern formation and its EMI shielding efficiency. 
Applied Surface Science, 2006. 252(8): p. 2665-2672. 
[5] Dangelewicz, A.M., et al., Structure-Dependent Electrical Properties of Carbon 
Nanotube Fibers. Adv. Mater, 2007. 19: p. 3358-3363. 
[6] Planeix, J.M., et al., Application of carbon nanotubes as supports in heterogeneous 
catalysis. Journal of the American Chemical Society, 1994. 116(17): p. 7935-7936. 
[7] Wang, F., S. Arai, and M. Endo, Metallization of multi-walled carbon nanotubes with 
copper by an electroless deposition process. Electrochemistry communications, 2004. 
6(10): p. 1042-1044. 
[8] Ellis, A.V., et al., Hydrophobic anchoring of monolayer-protected gold nanoclusters to 
carbon nanotubes. Nano Letters, 2003. 3(3): p. 279-282. 
[9]   Quinn, B.M., C. Dekker, and S.G. Lemay, Electrodeposition of noble metal 
nanoparticles on carbon nanotubes. J. Am. Chem. Soc, 2005. 127(17): p. 6146-6147. 
[10] Zhang, Y., et al., Metal coating on suspended carbon nanotubes and its implication to 
metal–tube interaction. Chemical Physics Letters, 2000. 331(1): p. 35-41. 
[11] Hung, C.C., M.E. Dillehay, and M. Stahl, A heater made from graphite composite 
material for potential deicing application. J. Aircr., 1987. 24(10): p. 725-730. 
[12] Hecht, D.S., L. Hu, and G. Grüner, Electronic properties of carbon nanotube/fabric 
composites. Current Applied Physics, 2007. 7(1): p. 60-63. 
[13] Liu, P., et al., Fast High-Temperature Response of Carbon Nanotube Film and Its 
Application as an Incandescent Display. Advanced Materials, 2009. 21(35): p. 3563-
3566. 
[14] Biercuk, M.J., et al., Carbon nanotube composites for thermal management. Applied 
Physics Letters, 2002. 80(15): p. 2767-2769. 
[15] Nan, C.W., Z. Shi, and Y. Lin, A simple model for thermal conductivity of carbon 
nanotube-based composites. Chemical Physics Letters, 2003. 375(5-6): p. 666-669. 
[16] Yang, D.J., et al., Thermal conductivity of multiwalled carbon nanotubes. Physical 
Review B, 2002. 66(16): p. 165440. 
[17] Aliev, A.E., et al., Thermal conductivity of multi-walled carbon nanotube sheets: 
radiation losses and quenching of phonon modes. Nanotechnology. 2010. 21: p. 
035709. 
[18] Aliev, A.E., et al., Thermal transport in MWCNT sheets and yarns. Carbon, 2007. 
45(15): p. 2880-2888. 
 


A heater made from graphite composite material for potential deicing application.

A simple model for thermal conductivity of carbon nanotube-based composites. Chemical Physics Letters,

Application of carbon nanotubes as supports in heterogeneous catalysis.

Carbon nanotube composites for thermal management.

Carbon nanotubes: opportunities and challenges. Frontiers in surface and interface science,

Electrodeposition of noble metal nanoparticles on carbon nanotubes.

Electronic properties of carbon nanotube/fabric composites. Current Applied Physics,

Fast High-Temperature Response of Carbon Nanotube Film and Its Application as an Incandescent Display. Advanced Materials,

Frequency-and electric-field-dependent conductivity of single-walled carbon nanotube networks of varying density. Physical Review B,

Hydrophobic anchoring of monolayer-protected gold nanoclusters to carbon nanotubes. Nano Letters,

Metal coating on suspended carbon nanotubes and its implication to metal–tube interaction. Chemical Physics Letters,

Metallization of multi-walled carbon nanotubes with copper by an electroless deposition process. Electrochemistry communications,

Selective metal pattern formation and its EMI shielding efficiency. Applied Surface Science,

Thermal conductivity of multi-walled carbon nanotube sheets: radiation losses and quenching of phonon modes.

Thermal conductivity of multiwalled carbon nanotubes. Physical Review B,

Thermal transport in MWCNT sheets and yarns. Carbon,

Transparent, conductive carbon nanotube films.

Carbon nanotube based composites film heater for de-icing application

Name not available

https://researchportal.port.ac.uk/portal/services/downloadRegister/159403/ECCM14_Proceeding.pdf

Carbon nanotube based composites film heater for de-icing application

Abstract

Similar works

Full text

Available Versions

Portsmouth University Research Portal (Pure)

Name not available