Multiwalled carbon nanotube films as temperature nano …...Typical dimension of the bucky paper...
Transcript of Multiwalled carbon nanotube films as temperature nano …...Typical dimension of the bucky paper...
Multiwalled carbon nanotube films as temperature nano-sensorsP. Ciambelli2,3 , A. Di Bartolomeo1, 3,, M. Sarno2,3, F. Giubileo1,4, C. Altavilla2,3, D. Sannino2,3, L. Iemmo1,S. Piano1, F. Bobba1, 3, A. M. Cucolo1, 3
1 Department of Physics "E.R. Caianiello", University of Salerno, via S. Allende, 84081 Baronissi (SA), Italy. 2 Department of Chemical and Food Engineering, University of Salerno, via Ponte Don Melillo, 84084 Fisciano (SA), Italy3 NANO_MATES, Research Centre for NANOMAterials and nanoTEchnology at University of Salerno, c/o Department of Physics "E.R. Caianiello", University of Salerno, 84081
Baronissi (SA), Italy 4 CNR-INFM Laboratorio Regionale SUPERMAT, via s. Allende, 84081 Baronissi (SA), Italy
CNT synthesis, film preparation and characterization
MWCNT film as temperature sensor
R(T) measurements
Multiwalled carbon nanotubes (MWNTs) Synthesis
MWNTs (length 100-200 µm, external diameter 10-25 nm, internal diameter 5-10
nm) were synthesized by ethylene catalytic chemical vapour deposition (CCVD) on
Co/Fe-Al2O3 catalyst. After HF treatment high purity multiwalled carbon
nanotubes (>97%) were obtained.
BuckyPaper free-standing film preparation
0.5 g of MWNTs were suspended in 100 g of H2O in presence of 0.1 mg of sodium
dodecyl sulfate, sonicated and then vacuum filtered through a membrane support.
After drying, a quite rigid paper was removed from the support.
SEM and Raman Spectroscopy characterisation
Films with bundle organization, of different thickness (300-500 µm) and density,
were produced.
A 4-probe method was used to measure the CNT film
resistance. Pt and Ge/Si sensors, close to the CNT film, were
added to monitor the temperature.
R(T) had usually a non-metallic (with negative dR/dT)
behaviour over a wide range of temperatures (4 to 420 K).
A transition from non-metallic to metallic behavior occurring
at a crossover temperature of few tens degrees around 0°C
was sometimes observed. A heterogeneous model (see Kaiser
A. B., Dusberg G., Roth S., Phys. Rev. B, 57, 3, 1998, 1814-
1821) involving regions of highly anisotropic metallic
conduction separated by tunneling barrier regions can explain
such mixed behavior by means of the competing mechanisms
of the metallic resistance rise and the barrier resistance
lowering for increasing temperature.
)]TT/(Texp[R)T/Texp(R)T(Rsctmm
++−=
The monotonic behaviour (either non-metallic or
metallic) suggests that multiwalled carbon nanotube
films can be used as miniaturized temperature sensors
with a temperature coefficient of resistance (TCR) of
the order of 10-3/°C, comparable with the ones for
other temperature sensors (with Pt, Si, Ge).
However, the nano-size of CNTs results in a very high
sensitivity to the environmental temperature change
and in an excellent time response, which is highly
desirable for local measurements in systems with very
rapid temperature variations and where the
perturbation introduced by the thermometer has to be
reduced as much as possible.
The CNT sensor shows a faster response than the Ge, Si and
PT ones. A long term stability (less than 1%) and a good
behavioural accordance with the measurements of traditional
thermistors have been observed in continuous, few days long,
operating cycles. An ideal sensor reaches the same
maximum/minimum resistance for the same
maximum/minimum temperature. This applies to our CNT
film for temperature swinging for several hours.
Nanotech 2008 – Boston June 1-5 2008
0 50 100 150 200 250 300
0,6
0,8
1,0
1,2
1,4
Temperature (K)
Resis
tan
ce
(O
hm
)
220 240 260 280 300 320 340 360 380 400 420 440
0,92
0,94
0,96
0,98
1,00
1,02
1,04
1,06
1,08
1,10
Resis
tance
(O
hm
)
Temperature (K)
T down T up
T down
T down T up
220 240 260 280 300 320 340 360 380 400 420
0,74
0,75
0,76
0,77
0,78
0,79
0,80
0,81
Re
sis
tance
(O
hm
)
Temperature (K)
Typical dimension of the bucky paper samples: 8 mm x 3 mm x 0,3 mm
As prepared MWNTs (TEM image)
CNT film (High magnification SEM image)
Raman spectra
University of SalernoCentre NANO_MATES
Transition from non-metallic
to metallic behaviour
Non-metallic behaviour Non-metallic behaviour
400 600 800 1000 1200 1400 1600 1800 2000
1,35
1,40
1,45
1,50
1,55
1,60
1,65
1,70
Tem
pera
ture
(K)
1/R
esis
tan
ce
CN
T
(1/O
hm
)
Time (s)
400 600 800 1000 1200 1400 1600 1800 2000
50
100
150
200
250
Ge Thermometer
1/R-CNT
0,0 0,5 1,0 1,5 2,0 2,5 3,0
0,7
0,8
0,9
1,0
1,1
1,2
Termometer
1/R-CNT
Te
mp
era
ture
(K)
Time (h)
0,0 0,5 1,0 1,5 2,0 2,5 3,0
0
5
10
15
20
25
30
35
1/R
esis
tan
ce
CN
T
(1/O
hm
)
Ge Thermometer
0 4 8 12 16 20 24
1,06
1,07
1,08
1,09
1,10
1,11
1,12
1,130 4 8 12 16 20 24
292
293
294
295
296
297
298
Tem
pe
ratu
re (K
)
Time (h)
Co
nd
ucta
nce (
1/O
hm
)
Pt Thermometer
Si Thermometer
Typical dimension of the bucky paper samples: 8 mm x 3 mm x 0,3 mm
220 240 260 280 300 320 340 360 380 400 420 440
0,92
0,94
0,96
0,98
1,00
1,02
1,04
1,06
1,08
1,10
Resis
tance
(O
hm
)
Temperature (K)
T down
T up
T down
T down
T up
CNT film (SEM image)
In addition, the working range for the CNT sensor is larger and its small size
implies a lower power consumption (< 1 µW).
Raman spectra confirm that the treatment
did not introduce defects into CNTs.