Pb nanoclusters were deposited onto a suspended carbon nanowire (CNW), where in situ temperature variable observation was carried out by a transmission electron microscope. The heating temperature was up to 450 °C. Both the melting and evaporation of the Pb nanoparticles on the CNW were retarded when compared to the particles on the support frame. The obvious temperature difference of up to 10 K along the CNW of less than 1 μm was demonstrated. It was attributed to the irradiating dissipation-dependent on the surface area of the decorating Pb particle by calculation

A Boukai

A Stella

AJ Bullen

AS Arico

B Yoo

EA Hoffmann

EA Homann

F Banhart

Fengqi Song

G Joshi

GM Pastor

Guanghou Wang

J Hone

JG Snyder

Jianguo Wan

L Shi

Longbing He

MET Molares

Min Han

P Jensen

Y Dubi

Y Zhang

ZW Liu

English

PubMed

Abstract Pb nanoclusters were deposited onto a suspended carbon nanowire (CNW), where in situ temperature variable observation was carried out by a transmission electron microscope. The heating temperature was up to 450 &#176;C. Both the melting and evaporation of the Pb nanoparticles on the CNW were retarded when compared to the particles on the support frame. The obvious temperature difference of up to 10 K along the CNW of less than 1 &#956;m was demonstrated. It was attributed to the irradiating dissipation-dependent on the surface area of the decorating Pb particle by calculation. (See supplementary material 1)   Electronic supplementary material   The online version of this article (doi:10.1007/s11671-009-9455-y) contains supplementary material, which is available to authorized users.   Click here for file  </suppl

He Longbing

Han Min

Song Fengqi

Wan Jianguo

Wang Guanghou

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Nanoscale Research Letters

Obvious Temperature Difference Along a Pb Cluster-Decorated Carbon Nanowire

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NANO EXPRESS
Obvious Temperature Difference Along a Pb Cluster-Decorated
Carbon Nanowire
Fengqi Song • Longbing He • Min Han •
Jianguo Wan • Guanghou Wang
Received: 22 July 2009 / Accepted: 25 September 2009 / Published online: 10 October 2009
 to the authors 2009
Abstract Pb nanoclusters were deposited onto a sus-
pended carbon nanowire (CNW), where in situ temperature
variable observation was carried out by a transmission
electron microscope. The heating temperature was up to
450 C. Both the melting and evaporation of the Pb
nanoparticles on the CNW were retarded when compared
to the particles on the support frame. The obvious tem-
perature difference of up to 10 K along the CNW of less
than 1 lm was demonstrated. It was attributed to the
irradiating dissipation-dependent on the surface area of the
decorating Pb particle by calculation.
Keywords Temperature difference  Retarded melting 
Thermal transportation  Pb  Cluster  Carbon nanowire
Introduction
Much attention has been paid to the sub-micrometer scale
thermal transportation along a nanowire mainly due to the
scale-dependent carrier behavior upon nanoconfinement
and their potential application in the thermoelectric devices
and thermoresistive coating materials [1–7]. One of the key
problems is the temperature difference (TD) between two
ends of the nanowire [8–10]. However, the TD on the sub-
nanometer scale (or even on a few micrometers) keeps
rather small. It will diminish to a very small value in less
than 1 second, even if a highly thermal insulating material
is employed. It is because the power of thermal conduction
from the end of the high temperature to that of the low
temperature is much higher than the thermal dissipation if
there is a considerable TD. As the result, only the TD of
0.2 K was observed along a single wall carbon nanotube of
2 lm [10]. Even, the well-known thermoelectric candidate
of Bi nanowire produced a small TD of 4 K along the
length of 15 lm [2, 11, 12]. The measurement of these
small values of the TDs requires some deliberately
designed MEMS devices and complex procedures to make
precise calibration of local temperatures [7, 13, 14]. In this
work, carbon nanowires (CNWs) were suspended on a
holey support film, and then Pb nanoclusters were depos-
ited on the sample in situ temperature variable transmission
electron microscopic (TEM) observation demonstrated the
obvious TD of up to 10 K along the CNW of less than
1 lm.
On the other hand, the present TD permits the intuitivistic
visualization of the nanoscale thermal inhomogeneity.
Nanostructures of the low melting point nanoparticles (Pb,
Ga or even Zn) have long been featured for their thermal
effects, such as the freezing behavior [15, 16], phase oscil-
lation between liquid and solid [17] and the liquid nanojet
from the core expansion ([18], see the supplementary
materials also). In the normal heating carried out through
broad contacts, the earlier mentioned thermal effects
occurred abruptly ([16, 18], see the supplementary materials
also). The detailed explanation of the experiment desires
decomposed visualizations. However, it is only possible
Electronic supplementary material The online version of this
article (doi:10.1007/s11671-009-9455-y) contains supplementary
material, which is available to authorized users.
F. Song (&)  J. Wan  G. Wang
National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University,
210093 Nanjing, China
e-mail: songfengqi@nju.edu.cn
L. He  M. Han
National Laboratory of Solid State Microstructures
and Department of Materials Science and Engineering,
Nanjing University, 210093 Nanjing, China
123
Nanoscale Res Lett (2010) 5:138–142
DOI 10.1007/s11671-009-9455-y
during controlled heating. In our work, heat is expected to
input to the particle on CNW (POC) through the CNW,
which limits the thermal input by changing the 2-dimen-
sional (D) contact of the particle on the support (POS) to 1-D
transportation. The retardations of the POC’s melting and
evaporation were then decomposedly visualized.
Experimental Details
The CNW was prepared in a radiofrequency plasma sput-
tering chamber, where a small nozzle to the high-vacuum
chamber led the CNW onto the TEM copper meshes with
holey support films. Only enough long CNWs were sus-
pended on the microsized pores. TEM, High-resolution
TEM and electron energy loss spectra (EELS) proved their
amorphous structures (see the supplementary materials
also, [19]). The beam of Pb nanoclusters was generated by
a gas aggregation cluster source and deposited onto the
copper mesh [18]. A TEM of Jeol 200CX was employed
for the in situ observation, and the process was recorded by
a digital video system.
Figure 1a shows a TEM image from the region of
interest, where we can see the Pb particles are distributed
on the support film and on the CNW simultaneously. The
CNWs with the diameters of 10–20 nm are suspended on
the pore, on which a Pb nanoparticle with the size of about
130 nm sits. The system was heated through a heating
holder and the thermocouple sensor recorded the heating
temperatures in a temperature-fixing mode. The thermal
conduction between the heating source and the copper
mesh was enhanced by two pressed nickel grids. The holey
support film was attached to the copper mesh, and all the
region in the support film was within a few micrometers
from the copper grid. It guarantees the efficient heating of
the support film. Therefore, we regard the temperature
from the thermocouple meter as the temperature on the
amorphous support. POS was heated more effectively than
POC due to the 2-D transporting routes (see Fig. 1b). We
track the melting of the Pb particles to show the thermal
effect.
Result and Discussion
Here two phenomena are identified as the signatures of the
particles’ melting. One of them is the abrupt change of
the contrast, which can be seen in Fig. 1a. The exposure to
the air coated an oxide shell on the Pb particles before
transferring to the TEM. After the particle is melted in the
TEM, the original crystalline Pb core turns to liquid
abruptly. The change of the diffraction contrast results in
the visualization of the oxide shell [15]. It may be not clear
enough for POS since the amorphous support film con-
tributes to a noisy background sometimes. The other is the
cavity from the evaporation. It can be seen in the points
marked by the arrows in Fig. 2d, where some material
from the melted core is evaporated soon due to the low
heat of evaporation of Pb. The abruptly enhanced evapo-
ration is subject to the transition to liquid, which shows the
melting point has passed then. Appearance of the cavities
also eliminates the influence of superheating due to close
oxide coating [16].
Figure 2 shows the evidence of melting retardation.
Here, we trace the change of two particles, one of which is
POC and the other is POS (Fig. 2b–c). Three tiny dots on
the film demonstrate that the particles are well tracked.
Figure 2a is the original image of the system at the tem-
perature of 200 C. All the particles were stable until the
temperature reached 300 C. A tiny cavity appeared inside
Fig. 1 The experimental configuration and schematic show of heat
flow. a is the TEM image of the whole device, where we can see the
nanowire is suspended on the hole of a porous carbon film. It was
directly taken from the phosphorus screen by a digital video machine
when the system was heated to 350 C. b shows the schematic heat
flow marked by the arrows
Nanoscale Res Lett (2010) 5:138–142 139
123
the POS as shown in Fig. 2b at 300 C and kept growing
during further heating, demonstrating its melting. Some
POS even collapsed. No obvious signature of melting
occurred in POC after 7 min of heating at 300 C. With
increasing the heating temperature, the POC melted as
shown by Fig. 2c, where a clear oxide shell can be seen.
The earliest appearance of the oxide shell was at 310 C
(Fig. 2d). It was read from the thermocouple meter, and it
was the temperature of the support film, when the POC was
just beginning to melt. The melting of POS occurred before
300 C. Assuming the equivalence of the melting points of
all the Pb particles, the evidence with a TD of more than
10 K is present along the CNW. One may argue that the
melting retardation is due to the size effect of Pb nano-
particles. But the size effect makes little influence on the
melting points of the nanoparticles larger than 10 nm [19,
20], while the Pb particles in the experiment are larger than
50 nm. Furthermore, we can observe the evaporation of a
very large POS (Fig. 2d). It occurs simultaneously with the
evaporation of other POSs. It eliminates the influence of
the size-dependent melting point and consolidates the
presence of the earlier mentioned TD.
As stated earlier, the TD of up to 10 K between the two
ends of less than 1 lm has been demonstrated. Such a TD
is unexpectedly high since it turns out a thermal insulting
performance of 104 K/mm. It could not be the result from
the dominance of thermal transportation along CNW, as
shown by the top calculation curve in Fig. 3a [19, 21].1 If
only the thermal transportation due to the TD contributes to
the heat flow of the POC, the TD can cease to almost zero
shortly. For example, if we increase the heating tempera-
ture from 573 to 623 K from one end of the CNW, the TD
reduces to 0.1 K in ten milliseconds. The heavier mass of
the POC contributes little to the TD. After considering the
overall sources of thermal input and thermal dissipation of
the POC, the irradiation is found to be an effective thermal
dissipation route. Firstly, the convection through the air is
excluded due to the high-vacuum environment. Secondly,
thermal conduction through the CNW is the heat source.
Final dissipation source of the irradiation can be described
by the Stefan-Boltzmann Law P ¼ Ser  T4, where S is the
area of POC, e of 0.43 is the emission coefficient of
the grey body (oxided Pb) and r is the constant. Although
the irradiation effect is often omitted in the thermal mea-
surement at a few hundred Celsius degrees [13], it is
actually related to the surface area. In the experiment, a
huge Pb particle is attached on the CNW, leading to a much
larger surface than the original CNW and a larger irradia-
tion thermal dissipation. It could be a reasonable expla-
nation as shown by the calculation in Fig. 3b. The
calculation considers the CNW thermal input, the irradia-
tion dissipation and the temperature increase from heating.
One can find the TD increases with increasing the size of
POC. During heating from 673 to 723 K, the stable TD is
still smaller than 0.5 K when the diameter is equal to that
of CNW. It is consistent to the omittance in normal thermal
measurement [13]. While POC becomes a ball with the
radius of 65 nm, the TD of 4.5 K can be expected. The
particle with the radius of 100 nm leads to a TD of nearly
10 K. The calculation validates the presence of the obvious
TD in the experiment. It provides the TD of more than 1 K
Fig. 2 The evidence for retardation of particle melting. a, b and c are
the TEM images taken at the time of 9’, 23’40’’ and 31’52’’,
respectively. As recorded by the thermocouple, the corresponding
heating temperatures are 200, 300 and 325 C. The irregular edges of
the insets are due to the cut of the frames from the DV. The sample
kept shrinking when it was heated. The arrows point to the light
vacancies due to the evaporation of the cores. (d) was taken at the
heating temperature of 310 C. It shares the same scales bar as (a)
1 DT ¼ TDxsl  SerT4  Q0eEv=KT
 
=cm, in which c, m and S are
the specific heat, the mass and the surface area of the POC
respectively. s, l and x are the cross section, the length and the
thermal conduction coefficient of the CNW. T is the temperature and
Td is the TD between the two ends of the CNW. The first item is the
thermal input from the CNW conduction; the second item is the
irradiation of the grey body, e = 0.43 is the emission coefficient of
the oxided Pb; The third item describes the evaporation dissipation,
where Ev = 2.9 eV stands for the heat of evaporation of lead. (from
engieeringbox.com). The formula is employed for the calculation of
Figs. 3 and 4. The time step of 1 ms is used. The thermal conductivity
of 0.2 W/k m is used according to the previous measurement and the
sp3 ratio (less than 10%) of the current CNW.
140 Nanoscale Res Lett (2010) 5:138–142
123
at room temperature, which can be compared with the
previous study [8, 10, 11].
Effective thermal dissipation in the cold end generates
the obvious TD. Some other approaches of thermal dissi-
pation are also considered. The absorption of the heat of
melting makes much less contribution than the thermal
input from TD driven thermal conduction. The fixed
melting point of the POC during heat absorption increases
its temperature abruptly, which ceases by the enhanced
input immediately. The thermal evaporation is also con-
sidered. As shown in Fig. 4a–d, the evaporation of the Pb
core increases with increasing the heating temperature.
Here, we found that the evaporation is readily controlled
when compared to POS. The evaporation of the POC
becomes as obvious as that of POS after the heating tem-
perature of 350 C. Considering the heat dissipation from
the evaporation, it gives the curves in Fig. 4e. From the
curves, the little influence of the TD from the evaporation
is concluded.
Conclusion
The obvious TD has been demonstrated along an amor-
phous CNW of less than 1lm decorated by the Pb nano-
particles. The irradiation effect enhanced by the larger
surface of POC drives the obvious TD. The melting and the
evaporation of the on CNW-Pb particle are retarded by the
confined thermal transportation along the CNW. Such a
phenomenon could give the hint of the future fabrication of
thermoresistive materials.
Acknowledgments This work was financially supported by the
National Natural Science Foundation of China (Grant No. 90606002,
10674056 and 10904065), the National Key Projects for Basic
Research of China (Grant No. 2009CB930501, 2010CB923401). The
authors acknowledge Mr. Jianming Hong (Nanjing University) for the
technical assistance and Dr. Xuefeng Wang (Suzhou University) for
thoughtful discussions.
Fig. 3 The influence of the irradiation on the TDs. a assuming the
heating temperature of 623 K at one end of the CNW and particle radius
of 65 nm, we calculated the temperature at the other end. The
calculation gives the result without considering the irradiation by the
smooth line and shows the result considering the irradiation by the red
triangular-dot curve. TD is the box-dot curve. b describes the influence
of the radius of the Pb particle on its temperature and the TD along the
nanowire. The decreasing curve plots the temperature of the Pb particle
against its radius and the rising curve plots the TD. The left axes of both
the insets are the Pb particle’s temperature and the right axes are the TD.
The heating temperature is assumed 723 K. (Color figure online)
Fig. 4 The evidence of the retarded evaporation. a, b, c and d are the
TEM images taken at the heating temperatures of 310, 350,400 and
450 C, respectively. One can find the growth of the cavity inside the
particle. The evaporation rate estimated from the images agrees to the
estimation from the bulk value of heat of vaporization. Assuming
the particle radius of 65 nm and the evaporation rate of eEv=kT , the
influence of the evaporation on the TD is assessed, resulting in the
round-dot curve (irradiation ? evaporation) and the box curve (only
irradiation) in (e). The x axis of test temperature means the heating
temperature
Nanoscale Res Lett (2010) 5:138–142 141
123
References
1. G. Joshi, H. Lee, Y. Lan, X. Wang, G. Zhu, D. Wang,
R.W. Gould, D.C. Cuff, M.Y. Tang, M.S. Dresselhaus, G. Chen,
Z. Ren, Nano Lett. 8(12), 4670 (2008)
2. B. Yoo, F. Xiao, K.N. Bozhilov, J. Herman, M.A. Ryan, N.V.
Myung, Adv. Mater. 19, 296 (2007)
3. A.S. Arico, P. Bruce, B. Scrosati, J.M. Tarascon, W. Van
Schalkwijk, Nature Mater. 4, 366 (2005)
4. J.G. Snyder, J.R. Lim, C.-K. Huang, J.P. Fleurial, Nature Mater.
2, 528 (2003)
5. Y. Dubi, M. Di Ventra, Nano Lett. 9(1), 97 (2009)
6. A. Boukai, K. Xu, J.R. Heath, Adv. Mater. 18, 864 (2006)
7. E.A. Homann, J.E. Matthews, N. Nakpathomkun, A.I. Persson,
H. Linke, Nano Lett. 9(2), 779 (2009)
8. Y. Zhang, J. Christofferson, A. Shakouri, D. Li, A. Majumdar,
Y. Wu, R. Fan, P. Yang, IEEE Trans. Nanotech. 5(1), 67 (2006)
9. H.-L. Zhang, J.-F. Li, B.-P. Zhang, K.-F. Yao, W.-S. Liu,
H. Wang, Phys. Rev. B 75(1), 205407 (2007)
10. J. Hone, I. Ellwood, M. Muno, A. Mizel, M.L. Cohen, A. Zettl,
A.G. Rinzler, A.E. Smalley, Phys. Rev. Lett. 80(5), 1042 (1998)
11. M.E.T. Molares, N. Chtanko, T.W.C. Cornelius, D. Dobrev, I.
Enculescu, R.H. Blick, R. Neumann, Nanotechnology 15, S201
(2004)
12. T.W.C. Cornelius, F. Volklein, M.E. Toimil Molares, S. Karim,
R. Neumann, presented at the proceedings of European confer-
ence on thermalelectrics (Cardiff, 2006; unpublished)
13. L. Shi, D. Li, C. Yu, W. Jang, D. Kim, Z. Yao, P. Kim,
A. Majumdar, J. Heat Transfer 125(5), 881 (2003)
14. E.A. Hoffmann, N. Nakpathomkun, A.I. Persson, H. Linke,
H.A. Nilsson, L. Samuelson, Appl. Phys. Lett. 91, 252114 (2007)
15. Z.W. Liu, Y. Bando, M. Mitome, J. Zhan, Phys. Rev. Lett. 93,
095504 (2004)
16. F. Banhart, E. Hernandez, M. Terrone, Phys. Rev. Lett. 90,
185502 (2003)
17. A. Stella, A. Migliori, P. Cheyssac, R. Kofman, Europhysics.
Lett. 26, 265 (1994)
18. F.Q. Song, M. Han, M.D. Liu, B. Chen, J.G. Wan, G.H. Wang,
Phys. Rev. Lett. 94, 093401 (2005)
19. P. Jensen, Rev. Mod. Phys. 71(5), 1695 (1999)
20. G.M. Pastor, J. Dorantes-Davila, K.H. Bennemann, Chem. Phys.
Lett. 148, 459 (1988)
21. A.J. Bullen, K.E. O’Hara, D.G. Cahill, O. Monteiro, A. von
Keudell, J. Appl. Phys. 88, 6317 (2000)
142 Nanoscale Res Lett (2010) 5:138–142
123


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Obvious Temperature Difference Along a Pb Cluster-Decorated Carbon Nanowire

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