Preparation and characterization of coatings with anisotropic thermal conductivity

The temperature increase caused by a concentrated heat source can affect the performance of electronic components inside spacecraft. Therefore, the development of an advanced thermal control system is essential for maintaining them in a safe temperature range. For this purpose, anisotropic thermal conductive coatings consisting of phenolic formaldehyde resin (PF) and pyrolytic graphite sheets (PGS) have been prepared in this work. The area of the heat-affected zone produced by a high-energy continuous wave laser is calculated to estimate the thermal diffusivity along the horizontal direction of the coating, whereas the thermal insulating capacity in the vertical direction is determined by measuring the back-surface temperature of the aluminum substrate. The obtained results show that the introduction of PGS noticeably improves the thermal diffusivity of coating, leading to a decrease in its back-surface temperature. After irradiating the coating containing three pieces of PGS with laser at a power density of 1500 W/cm2 for 10 s, its back-surface temperature is only 29 °C, which is much lower than that of the coating fabricated from pure PF (190 °C). Hence, the prepared coatings exhibit excellent anisotropic thermal conductive properties and can be potentially used as protective shields for spacecraft electronics.