Preparation And Study Of Sol-Gel Derived Coatings For Heat Dissipation And Insulation Applications

This paper mainly studies the preparation and testing of heat dissipation and thermal insulation coatings.Rapid growth in the field of electronics has led to development of equipment with high emission of heat,which has to be dissipated away very fast to avoid damage to vital components.Coatings with high thermal transfer coefficient and high emissivity in the infra-red range can dissipate away heat fast from the equipment.Thermal insulation coatings on the other hand are desired for energy savings and thermal protection.Coatings with a low thermal transfer coefficient are thus desired for thermal insulation.The traditional methods for deposition of coatings for thermal applications include Chemical Vapor Deposition(CVD),Physical Vapor Deposition(PVD),Electron Beam PVD(EB-PVD),plasma spray,and magnetron sputtering.However,these methods require high processing temperature and may produce too thin coatings.Sol gel technology therefore provides a versatile method for producing coatings with tunable microstructures at low temperatures.Heat dissipation coatings were prepared by sol gel composite process by dispersing nano particles in colloidal sol prepared by hydrolysis and condensation of alkoxides precursors.Taguchi Design of Experiments method was used and results analyzed using Statistica Analysis software for Signal to Noise ratio(S/N)and Analysis of Variance(ANOVA).Heat insulation coatings were prepared by dispersing hollow glass microspheres(HGM)and superfine silica nanoparticles in a hybrid silane/epoxy resin binder prepared through the Sol-gel process.The HGMs and silica were first treated with a silane coupling agent to improve its bonding with the polymer.The coatings are characterized by infrared emissivity testing,thermal imaging,Scanning Electron Microscope(SEM)and Fourier Transform Infrared(FTIR)Spectroscopy.Heat dissipation coatings showed excellent thermal transfer properties and high emissivity of 0.915-0.941 was achieved.Thermal imaging proved the high rate of heat dissipation from the surface.Coatings showed high cooling efficiencies of 7.3-14%.Thermal insulation coatings showed low thermal transfer rates with low temperature difference and good physical properties,making it suitable for reduction of losses in pipes and refrigeration applications.