Dry media reaction-based anti-hydration coating on magnesium oxide microspheres for thermal interfacial applications

[Display omitted] •Developed MgO surface modification with CVD and PECVD techniques.•PECVD achieves rapid 20-minute anti-hydration coating via plasma activation.•The coating ensures MgO stability over 24 h at 85 °C and 85 % relative humidity.•Coating increases adhesion and thermal conductivity by ∼1.5 times in thermal paste. Magnesium oxide (MgO) is gaining attention as a next-generation thermal management material due to its better thermal conductivity compared to other oxides and excellent insulating properties. However, its susceptibility to hydration when exposed to atmosphere, which alters its material properties, necessitates the application of anti-hydration coatings for its use in thermal management. This study explores the use of Chemical Vapor Deposition (CVD) and Plasma-Enhanced Chemical Vapor Deposition (PECVD) as alternatives to the traditional sol–gel method to form anti-hydration coatings on MgO microspheres. The surface modification process was completed within 20 min for both processes, and the water contact angles of the spheres increased from ∼33° to ∼98° with CVD and ∼125° with PECVD. Compared to CVD, PECVD was found to be more effective in applying anti-hydration coatings, thanks to the plasma activation of the MgO surface and reactants, thereby better maintaining the physical and chemical properties under conditions of 85 °C and 85 % relative humidity. Furthermore, when used as a filler in thermal interface material composites, MgO modified with PECVD exhibited adhesion strength and thermal conductivity about 1.5 times higher than bare MgO, due to the increased affinity for the hydrophobic binder.