Polarized Raman spectroscopy for viscosity effect on the orientation degree and thermal conductivity of graphene nanoplatelet based composites

In this work, we fabricated the graphite nanoplatelets (GNPs)-based thermal conductive materials (TCMs) via the gap-coating method. Remarkably, the TCMs have a prominent heat conduction coefficient of 36.44 W/mK, which is attributed to the aligned graphite nanoplatelets. Viscosity is a key factor for the alignment of the fabricated composite. Polarized Raman spectroscopy was performed on the transverse sections of the composite to detect the orientation degree, and the intensity of the 2D Raman peak is sensitive to these anisotropic properties. Furthermore, Polarized Raman spectroscopy is initially employed for calculating interfacial thermal resistance (ITR) in samples with different viscosities. The orientation factors were 0.35 and 0.23, while the ITR values were 5.20 × 10⁻⁶ m² K W⁻¹ and 5.91 × 10⁻⁶ m² K W⁻¹ respectively. These values correspond to an increase in viscosity from 223 mPa·s to 559 mPa·s, confirming the effect of viscosity on both orientation degree and interfacial thermal resistance. This approach also provides a promising new method for detailed ITR determination in well-dispersed thermal conductive materials.