Issue 46, 2012
From the journal:

Journal of Materials Chemistry

Investigation of the stability of paraffin–exfoliated graphite nanoplatelet composites for latent heat thermal storage systems

Anne Mallow,a   Omar Abdelaziz,b   Kyriaki Kalaitzidouac  and  Samuel Graham*abc  

* Corresponding authors

a George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, 771 Ferst Dr., Atlanta, Georgia, USA
E-mail: sgraham@gatech.edu
Fax: +1-4048948496
Tel: +1-4048942264

b Energy and Transportation Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA

c School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA

Abstract

Organic materials, such as paraffin wax, are sought as stable and environmentally friendly phase change materials (PCM) for thermal energy storage, but they suffer from low thermal conductivity which limits the rate at which thermal energy flows into and out of the material. A common method to improve the PCM thermal behavior is through loading with high thermal conductivity particulate fillers. However, the stability of these composites in the molten state is a concern as settling of the fillers will change the effective thermal conductivity. In this work, we investigate the stability of wax loaded with exfoliated graphite nanoplatelets either of 1 μm (xGnP-1) or 15 μm (xGnP-15) diameter. The effect of dispersants, oxidation of the wax, viscosity of the wax, mixing time, and hydrocarbon chain length on stability is reported. It was found that the addition of octadecylphosphonic acid (ODPA) is an effective dispersant for xGnP in paraffin and microcrystalline wax. In addition, mixing time, viscosity, and oxidation of the wax influence stability in the molten state. Overall, it was found that a mixing time of 24 hours for xGnP-15 along with ODPA mixed in a high viscosity, oxidized microcrystalline wax results in composite PCM systems with the greatest stability determined at 80 °C in the molten state.

Graphical abstract: Investigation of the stability of paraffin–exfoliated graphite nanoplatelet composites for latent heat thermal storage systems

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Article information

DOI
https://doi.org/10.1039/C2JM35112A
Article type
Paper
Submitted
31 Jul 2012
Accepted
04 Oct 2012
First published
04 Oct 2012

J. Mater. Chem., 2012,22, 24469-24476

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Investigation of the stability of paraffin–exfoliated graphite nanoplatelet composites for latent heat thermal storage systems

A. Mallow, O. Abdelaziz, K. Kalaitzidou and S. Graham, J. Mater. Chem., 2012, 22, 24469 DOI: 10.1039/C2JM35112A

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