\”Matter\”: highly ordered graphene film thermally densified
Graphene film highly oriented in the portable electronic products may be used as a thermal interface material, but for most of the graphene film is obtained by the preparation of graphene oxide precursors, the decomposition of surface functional groups of graphene oxide in the pyrolysis process will so that the graphene film apparent expansion, affect the performance and application. Recently, Korea Institute of Basic Science Rodney S. Ruoff et al found that the small size of the reduced graphene oxide (rGO) was added to the graphene oxide (GO) in 3000 ℃ material after the heat treatment will have a less expansion and a higher density, then the mechanical compression may increase the density, but will introduce defects, again at 3000 ℃ heat treatment quality can be obtained highly oriented graphite alkenyl film , a graphene film density was 2.1g / cm3, cross section of a thermal conductivity of 5.65W / mK, thermal conductivity of the plane 2025 ± 25W / mK. Work related to \”Highly Ordered and Dense Thermally Conductive Graphitic Films from a Graphene Oxide / Reduced Graphene Oxide Mixture\” in the title, published in \” Matter \”. 
Researchers first high viscosity gel and a small size rGO GO dispersion prepared by grinding the latter two way precursors uniformly mixed to prepare a film by a doctor blade orientation GO, HI reduced and heat-treated in a solution , then the resultant film is pressed to remove the expansion caused by the heat treatment, and finally again to a heat treatment to reduce its lattice defect at 3000 deg.] C, to obtain graphene film of high thermal conductivity.
degree of graphitization graphene film will affect its thermal conductivity, the use of XRD, Raman and other means for this multistep Researchers graphite indicators treated samples were characterized. The results show that the addition of small size rGO 15wt% in the first heat treatment sample still improve the degree of graphitization of the material, and the secondary heat treatment subsequent thermocompression help to further enhance the degree of ordering of the graphitized film,While introducing a small size and multi-step treatment rGO also help to improve the mechanical properties and electrical conductivity of the material.
GO compared to the original film, the film after the heat treatment to reduce the surface functional groups, volume expansion occurs simultaneously, and therefore the density decreased, and again after compression after the heat treatment graphene film density increased. Compared to a single heat-treated graphene film, multi-step process after the graphene film with graphenes denser structure alignment, while the graphene sheet thinner.
Considering the sample is too thin, the researchers used photothermal laser-induced Raman techniques and finite element analysis of the heat flow measurement combining materials when the thermal conductivity of the surface, the measured thermal conductivity of the film surface was 2025 ± 25 W / mK, the film is adhered to the heating element, the film samples show a multi-step heat treatment better lateral heat transfer.
Summary
Researchers prepared GO complexed with a small size rGO sheet a highly oriented graphene film, Placement blade – heat treatment – compression – the secondary heat treatment method of multi-step treatment can significantly improve the thermal properties of the material, this method only common industrial processing technology using a doctor blade, rolling and heat treatment, it is expected to achieve large-scale preparation. Related links: https: //www.sciencedirect.com/science/article/pii/S259023852030076X
