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relation of CNT in PEG-1000. It can be seen that the thermal
resistance decreases gradually with increasing dispersing time.
Fig. 6 shows the Rth-mixing time for embedding CNT into
tetradecanol. The R th decreases slowly within the first 20
minutes. Afterward R th drops from 0.03K/W to 0.022K/W in
next 10min, and it decreases further to 0.021K/W after 1h
dispersion. The reduction of R th directly reflects the
distribution of CNTs in the PCM matrix. The longer the
dispersing time is, the more uniform the CNTs distribute,
which was also approved by SEM (see Figs. 3 and 4).
Fig.8: R th comparison of CNT enhanced PCM
Fig. 5: R th Change with dispersing time for CNT-PEG1000
IV. CONCLUSIONS
The present study indicates that the thermal resistance of
organic phase change materials can be greatly reduced by
incorporating multi-walled carbon nanotube into matrix. The
uniform distribution of carbon nanotubes is realized by
optimizing the dispersion parameters like temperature, shear
strength, rolling speed and gap of rollers. Carbon nanotube
enhanced thermally conductive phase change materials have
been developed. The further study including physical and
mechanical properties and application in heat dissipation is
being undertaken.
ACKNOWLEDGMENT
This work was partly financially supported by the 7 th
Framework Program of EU Nanopack (Project No. 216176,
Nano Packaging Technology for Interconnect and Heat
Dissipation).
Fig. 6: R th Change with dispersing time for CNT-Tetradecanol
3. R th comparison of CNT in different PCM
Figs. 7 and 8 give R th comparison before and after
embedding CNT into matrices. Only slight decrease in R th
can be achieved after dispersing CNT into PEG-1000, PEG-
1500 and PEG-2000, while an obvious reduction in R th is
realized by dispersing CNT into PEG-600 (see Fig. 7). From
Fig. 8 it can be seen that lowest R th (0.018K/W) is achieved by
embedding CNT in lauric acid. More than 40% reduction in R th
has been obtained for matrices lauric acid and 1-tetradecanol
respectively. The reduction as high as 50% has even been
realized for undecylenic acid.
Fig.7: Rth comparison (CNT-PEG system)
REFERENCES
[1] P. Kim et al., “Thermal transport measurements of
individual multiwalled nanotubes”, Phys. Rev. Lett.
87, 215502 (2001)
[2] X. Tang, E. Hammel et al, “Study of Carbon
Nanofiber Dispersion for Application of Advanced
Thermal Interface Materials”, Proceedings of 1 st
Vienna International Conference Micro-and Nano-
Technology, 395-400, March 9-11, 2005, Vienna,
Austria
[3] E. Hammel, X. Tang et al, “Performance of Carbon
Nanofiber Based Thermal Grease”, IMAPS Advanced
Technology Workshop on Thermal Management for
High-Performance Computing and Wireless
Application, Palo Alto, CA, USA, Oct.24-26, 2005
[4] Xu et al, “Enhancement of thermal interface materials
with carbon nanotube arrays”, International Journal
of Heat and Mass Transfer , Vol. 49, N o 9-10, (2006),
pp. 1658-1666
BRIEF BIOGRAPHY
The principal author, Dr. Xinhe Tang has joined Electrovac
AG since 2000. He focuses currently his work on the research
and development of new products such as thermal interface
materials and bonded copper/ceramic substrates. He
participates in the EU project “Nanopack” and leads the second
work package “Development of materials”.
©EDA Publishing/THERMINIC 2009 218
ISBN: 978-2-35500-010-2