Passive radiative cooling ZrO2/graphene composite coating with high emissivity and enhanced thermal conductivity for heat dissipation

The heat flow density of electronic power devices is increasing, raising concerns about their safe operation, which necessitates high-performance radiative cooling coatings to improve thermal management. This paper presents the preparation of ZrO 2 /graphene composite powders with an encapsulated structure via the combustion reaction of Mg with CO 2 and ZrO 2 using as a diluent. A passive radiative cooling coating with an emissivity of 0.97 was developed using ZrO 2 /graphenet composite powders and silicon fluoride (SiF) resin. At 50 wt% filler content, the thermal conductivity of the coating reached 4.6 W m −1  K −1 , an increase of 27.8% compared to the coating prepared with mechanically mixed ‘ZrO 2 +graphene’ powders. This improvement could be attributed to the ZrO 2 /graphene powders with encapsulated structure forming a phonon transport network in the coating. Heat dissipation tests of coated Al heat sinks demonstrated that the cooling efficiency increased from 8.2% to 15.0% as the thermal conductivity of the coating increased from 3.6 W m −1  K −1 –4.6 W m −1  K −1 . This result indicates that simultaneously achieving high thermal conductivity and high emissivity of the coating could significantly enhance the heat dissipation of the heat sink.