Abstract
Carbon materials as versatile fillers have drawn increasing attention in thermal conductive polymer composites, however, the thermal conductivity (TC) regulation of them remains challenging. Herein, the tunable lattice thermal conductivity is reported for glucose derived graphitic carbon nanoparticles (GCPs) and their polymer composites. Both the in-plane (La) and out-of-plane (Lc) coherence lengths of GCPs increase with carbonization temperature in the range of 700 °C to 1300 °C. The intrinsic TC of GCPs film is directly extracted from the dependence of the Raman G peak frequency on the excitation laser power and the first order temperature coefficient. It is found that the in-plane lattice TC increases exponentially with both of the increasing La and decreasing defect concentration. The GCPs are then used as highly processible fillers to fabricate thermoset composites based on reactive benzoxazine (BA-a). The total TC of the poly(BA-a)/GCPs are found increase monotonically from 0.27 W·m-1·K-1 to 0.34 W·m-1·K-1 with the increasing graphitization levels of GCPs, and a clear signature of thermal percolation threshold at 6 vol% GCPs loadings is also observed.
Highlights
Thermal conductivity (TC) of carbon allotropes span an extraordinary large range — of over five orders of magnitude — from ∼0.01 W·m-1·K-1 in amorphous carbon to above 5,000 W·m-1·K-1 at room temperature in carbon nanotubes (CNTs) or graphene.[1,2,3,4] Theoretical calculations and experimental results show that dimensionality, grain size, internal anharmonicities, defect, disorder, quantum coherence and contact resistance are factors that combine to determine the performance, functionality and mechanism, of heat conduction at the nanoscale.[5,6,7] In particular, the thermal conductivity regulation of carbon nanomaterials, as the macroscopic control of heat transfer, remains challenging
Both the in-plane and out-of-plane coherence lengths of graphitic carbon nanoparticles (GCPs) are considered as the results of increased carbonization temperature, or graphitization level
The intrinsic thermal conductivity of GCPs film related to the G-peaks
Summary
Thermal conductivity (TC) of carbon allotropes span an extraordinary large range — of over five orders of magnitude — from ∼0.01 W·m-1·K-1 in amorphous carbon to above 5,000 W·m-1·K-1 at room temperature in carbon nanotubes (CNTs) or graphene.[1,2,3,4] Theoretical calculations and experimental results show that dimensionality, grain size, internal anharmonicities, defect, disorder, quantum coherence and contact resistance are factors that combine to determine the performance, functionality (linear/nonlinear) and mechanism (diffusive/ballistic), of heat conduction at the nanoscale.[5,6,7] In particular, the thermal conductivity regulation of carbon nanomaterials, as the macroscopic control of heat transfer, remains challenging. The potential applications of carbon nanomaterials in polymer composites for thermal management and TC enhancement have been developed rapidly.[17,18,19,20] Despite the recordbreaking TC values of CNTs/graphene, the total TC enhancement is restricted by the large interfacial thermal resistance between the polymer mediated CNTs/graphene boundaries Another problem is that CNTs/graphene always induce sharp rise on the viscosity of either thermoset or thermoplastic polymers due to the fast development of 1D/2D gel network at low filler loadings, which result in poor workability limit in polymer processing.[21,22,23]
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