| Carbon-based electro-thermal coatings with benefits of high electric conductivity,light weight,stability,and low cost show great superiority in the application of indoor heating facilities,such as electro-thermal films,as well as anti-static coating and electromagnetic/radio frequency interference shielding.In the field of indoor heat supply,the eco-friendly electro?thermal films based on conductive coating have been gradually applied to indoor heat supply in cold areas.However,the air-gap between the floor substrate and electro-thermal films causes thermal dissipation.In addition,the installation of the electro-thermal films is also a complicated procedure.In order to solve the air-gap problem and develop a new individual with high reliability and electro-thermal property at low voltages,we aimed at preparing a laminated ceramic with high thermal efficiency,aesthetics,and integrality.In this thesis,we designed a novel laminated ceramic,which was composed of thermal conduction substrate,electro-thermal component,electric-insulation,and thermal insulation.The carbon-based electro-thermal layers were the composites of conductive fillers and water-based acrylic resin matrix.Based on the successful preparation of the electro-thermal layers with high electrical conductivity,the electro-thermal laminated ceramics consisted of ceramic tile substrate,carbon-based electro-thermal layer,silicone sealant layer,and foaming ceramic layer successively were prepared.With safety,thermal stability,reliability,aesthetic surface decoration,and good electro-thermal property at low voltages,the electro-thermal laminated ceramics are highly expected to be applied to indoor heat supply.To prepare the electro-thermal layer,the carbon-based suspension was spread on the ceramic tile by tape casting.The effects of kinds and contents of conductive fillers on the electro-thermal property of electro-thermal layer were investigated and then the optimal mass ratio of graphite,carbon-black and nickel powder was obtained,which was 45.5 wt%:43.5 wt%:11.0 wt%.After that,the effects of dispersant,ball-milling parameters,and filler content on the electro-thermal property of electro-thermal layer were studied.We found that when the carbon-based suspension was mixed by ball-milling at 400 r/min for Ih and the suspension thickness was 400 μm,the surface temperature of electro-thermal layer(20.5 cm lengthX 2 cm width),in which the content of conductive filler and dispersant was 55 wt%and 0.2 wt%respectively,was up to 119.0℃ achieved at an applied voltage of 36 V for 30 min.The effects of applied voltage and carbon-based suspension thickness on the electro-thermal property of the electro-thermal laminated ceramics were studied.Additionally,the effect of carbon-based suspension thickness on the interfacial adhesive strength between the ceramic tile and electro-thermal layer was characterized and analyzed.It indicated that at an applied voltage of 10 V for 30 min,the surface temperature of the electro-thermal laminated ceramics with the carbon-based suspension of 1.0 mm was 40.3 °C,which was available for indoor heat supply.Furthermore,the temperature distribution on the surface of laminated ceramics was quite uniform.The adhesion strength of the electro-thermal layer with the carbon-based suspension thickness of 1.0 mm was 1.02 MPa with the failure mode of cohesive failure.A comparative study of adhesive strength and volume resistivity during thermal aging at 100℃was conducted to analyzed the thermal stability of the laminated ceramics.It can be found that the adhesive strength of electro-thermal layer decreased slightly and the volume resistivity showed little increase,indicating that the electro-thermal laminated possessed good thermal stability and reliability. |
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