Investigation of the effects of graphite flake alignment on thermal emissivity by applying a magnetic field during coating of an aluminum sheet

초록

In this study we investigated the effects of graphite flake alignment on thermal emissivity by applying a magnetic field during coating of aluminum sheets with graphite. The coating paste was prepared by ball milling graphite flakes with an organic binder. The graphite flake content was 9.1, 13.0, 16.7, 20.0, or 23.1 wt.%. After coating of aluminum sheets with the paste by dipping, a magnetic field was applied vertically to the coated aluminum sheet by use of neodymium magnets. It was observed that the graphite flakes were aligned at an angle to the surface by application of the magnetic field. In contrast, in the absence of the magnetic field the graphite flakes were aligned horizontally on the aluminum sheets. The surface roughness of specimens prepared by use of a magnetic field (MF; R (a) = 10.172-14.654 mu m) was more than twofold that of specimens for which no magnetic field was applied (NMF; R (a) = 4.564 mu m). The thermal emissivity of MF9 (9.1 wt.% graphite; epsilon = 0.80) was higher than that of NMF9 (9.1 wt.% graphite; epsilon = 0.77). The thermal emissivity of MF20 (20.0 wt.% graphite) was 0.91, the highest in this study. It was shown that flakes aligned at an angle to the surface contribute to enhanced thermal emissivity. Well aligned graphite flakes are therefore expected to enable high thermal dissipation from electronic components.

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