Cellulose-based composite films with high through-plane thermal conductivity and low interface thermal resistance
To realize efficient heat dissipation of advanced electronics,it is urgent to develop high-performance thermally conductive composites.Great progresses have been achieved in thermally conductive composite films with high in-plane thermal conductivity in recent years,but the unsatisfactory through-plane thermal conductivity limits their applications.In practical applica-tions,thermally conductive composite films with high in-plane and through-plane thermal conductivities exhibit uniform heat dissi-pation performance,making them ideal thermal management materials for advanced electronics.Based on the"densest packing model",flexible bacterial cellulose based thermally conductive composite films with high through-plane thermal conductivity were prepared by adopting a vacuum assisted self-assembly strategy with the design of stereoscopic ordered structure of fillers and optimi-zation of interface structures,in which spherical Al2O3 particles and graphene nanoplatelets(GNPs)were employed as thermally conductive templates and enhancement components,respectively.A primary heat transfer network was constructed using large-sized Al2O3 particles,and a small number of small-sized Al2O3 particles were filled into the gaps between the large-sized particles.GNPs were arranged in an orderly manner using spherical Al2O3 particles as templates.The regulation of the ratio of Al2O3 particles with different geometries and the polydopamine(PDA)modification of thermally conductive fillers were carried out to form a synergisti-cally stereoscopic heat transfer network with a low interface thermal resistance,endowing the resulting composite films with high through-plane thermal conductivity of 5.42 W/(m·K)and in-plane thermal conductivity of 7.06 W/(m·K).PDA surface modifica-tion of thermally conductive fillers enhance the interaction between fillers and matrix,simultaneously improving the thermal conduc-tivity and the mechanical properties of the final composites with an increase in their fracture strength and elongation at break.
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