| Graphene is the name given to a flat monolayer of carbon atoms tightly packed into a two-dimensional (2D) honeycomb lattice with sp2 hybrid orbitals. Long-range ?-conjugation in graphene yields extraordinary thermal, mechanical, and electrical properties. Graphene also have high radius to thickness ratio and high specific surface area. This paper focuses on these advantages of graphene, graphene films are prepared, the electric heating characteristics of graphene film is investigated. Meanwhile, using a unique structure and high thermal conductivity of graphene, the silicone rubber composites were prepared using graphene and Al2O3 as fillers, the thermal conductivity effect was studied for grapheme/Al2O3/silicone rubber composites.In this paper,the graphene films and carbon nanotube films are prepared by vacuum filtration method and characterized by scanning electron microscopy(SEM).The electrothermal performance, resistance-temperature performance and thermal stability of graphene films, carbon fiber felts and carbon nanotube films were studied. It is found that the surface of graphene films are smooth and compact, forming a tight overlapping between the graphene sheets. Their electrothermal performance are studied in terms of applied voltage and input power. Time-dependent temperature profiles and heat distribution analyses show that the performance of graphene-based heaters is superior to that of conventional heaters based on carbon fiber. Infrared thermal image analysis showed that the heat generating of graphene films are more uniformity and stable. The graphene film-1(15g/m2) and graphene film-2(30g/m2) can exhibit high steady-state temperature of up to 96.0? and 118.5? when 4V is applied with a rapied heating rate. While the carbon fiber felt-1(15g/m2) and carbon fiber felt-2(30g/m2)reach saturated temperature to 39.0? and 60.5? when 4V is applied. For these carbon materials,when the temperature is below 100?, the input power is proportional to the stability temperature, when the temperature is higher than 100?,the temperature stability is no longer proportional to the input power. The temperature-resistance performance tests show that with increasing of temperature,the resistance are reduced. Thermal gravimetric analysis showed that graphene is more stable than the carbon fiber felt. Below 600?, graphene is not decomposed. These excellent result indicate that graphene-based electrothermal elements hold great promise for many practical applecations in the field of electric heating.In addition, in order to improve the thermal conductivity of silicone rubber (SR),we prepared hybrid composites by blending graphene and alumina (Al2O3) particles with silicone rubber and hot-pressing techniques. Microstructures, thermal conductivity, mechanical properties and thermal stability of the graphene/Al2O3/SR composites were investigated in this paper. Interface microscopic structure showed that graphene can form a uniform continuous heat transfer network structure in the silicon rubber matrix. The results showed that the thermal conductivity of the silicone rubber can be greatly improved by adding graphene, and the thermal conductivity of the graphene/Al2O3/SR hybrid composites reached to 1.49W/m·K, increasing by 831% in comparison with 0.16W/m·K for the neat silicon rubber, which is attributed to the extremely high thermal conductivity of graphene and its excellent network construction characteristics. Moreover, the silicone rubber-based composites with high thermal conductivity and high mechanical strengthcan be obtained by optimizing the loadings of graphene and Al2O3 particles. Thermal stability analysis showed that addition of graphene can significantly improve the thermal stability of silicone rubber composite. In view of its high thermal conductivity, the graphene/Al2O3/SR compositeshave great potential to be used as high-performance heat dissipation materials in many fields such as electronic devices, thermal interface materials, radiator,and so on. |
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