Anisotropic thermal property of magnetically oriented carbon nanotube/graphene polymer composites

A method was developed to magnetically align multi-walled carbon nanotubes (MWCNTs) as well as graphene nanoplates (GNPs) within a poly (dimethylsiloxane) (PDMS) matrix. The MWCNTs and GNPs polymer composites treated with magnetic field forming chain structures would be expected to produce anisotropic thermal conductivity. Firstly, the MWCNTs and GNPs were functionalized by γ-methacryloxy propyl trimethoxyl silane (KH570) in order to improve their compatibility with polymer matrix, and then different contents of the MWCNTs and GNPs were incorporated into PDMS and cured under a magnetic field up to 10 T to generate anisotropic MWCNTs/PDMS and GNPs/PDMS composites. The polarized Raman spectra and scanning electron microscopy (SEM) were applied to investigate the structures of MWCNTs and GNPs dispersion in the composites. The thermal conductivity of all samples was measured by using hot wire method. The results showed that the magnetically aligned MWCNTs/GNPs polymer composites feature high anisotropy in thermal conductivity. Thermal conductivity in the aligned direction of 10.0 T-treated PDMS composites with 3wt% GNPs content showed enhancements of 174% and 49%, compared to pure PDMS and non-magnetically treated GNP/PDMS composites, respectively. Compared with the MWCNTs fillers, the GNPs showed better performance in improvement of the thermal conductivity of the polymer composites.