Continuous Carbon Nanotube-Ultrathin Graphite Hybrid Foams for Increased Thermal Conductivity and Suppressed Subcooling in Composite Phase Change Materials

Year: 2015

Authors: Kholmanov I., Kim J., Ou E., Ruoff RS., Shi L.

Autors Affiliation: Univ Texas Austin, Texas Mat Inst, Austin, TX 78712 USA; Univ Texas Austin, Dept Mech Engn, Austin, TX 78712 USA; Univ Brescia, CNR INO, Sensor Lab, I-25123 Brescia, Italy; Inst Basic Sci, Ctr Multidimens Carbon Mat, Ulsan 689798, South Korea; Ulsan Natl Inst Sci & Technol, Dept Chem, Ulsan 689798, South Korea.

Abstract: Continuous ultrathin graphite foams (UGFs) have been actively researched recently to obtain composite materials with increased thermal conductivities. However, the large pore size of these graphitic foams has resulted in large thermal resistance values for heat conduction from inside the pore to the high thermal conductivity graphitic struts. Here, we demonstrate that the effective thermal conductivity of these UGF composites can be increased further by growing long CNT networks directly from the graphite struts of UGFs into the pore space. When erythritol, a phase change material for thermal energy storage, is used to fill the pores of UGF-CNT hybrids, the thermal conductivity of the UGF-CNT/erythritol composite was found to increase by as much as a factor of 1.8 compared to that of a UGF/erythritol composite, whereas breaking the UGF-CNT bonding in the hybrid composite resulted in a drop in the effective room-temperature thermal conductivity from about 4.1 +/- 0.3W m(-1) K-1 to about 2.9 +/- 0.2 W m(-1) K-1 for the same UGF and CNT loadings of about 1.8 and 0.8 wt %, respectively. Moreover, we discovered that the hybrid structure strongly suppresses subcooling of erythritol due to the heterogeneous nucleation of erythritol at interfaces with the graphitic structures.

Journal/Review: ACS NANO

Volume: 9 (12)      Pages from: 11699  to: 11707

More Information: We thank Dr. R. Piner for atomic force microscopy imaging of the nanotube bundle, G. Coloyan for her help in transferring nanotube bundle samples, and Prof. Peter Thrower for helpful discussions. This work was primarily supported by the ARPA-E HEATs program (Contract No. DE-AR0000178). J.H.K. and E.O. were supported by the Office of Naval Research (Grant No. N00014-14-1-0258) and Department of Energy Office of Basic Science (Grant No. DE-FG02-07ER46377), respectively. R.S.R. was supported by IBS-R019-D1.
KeyWords: ultrathin graphite foam; carbon nanotubes; phase change materials; composites; thermal conductivity
DOI: 10.1021/acsnano.5b02917

Citations: 286
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