Study On Preparation And Thermal Shock Resistance Properties Of High Emissivity Coatings For High Temperature

High emissivity coatings for high temperature were widely used in many cases such asenergy-saving of the industrial furnace, improving the thermal efficiency of infrared heaters, thermalcontrol of the spacecraft and so on because they have the effect of enhancing the radiation and thecooling. Due to the low value of the infrared emissivity and poor thermal shock resistance at hightemperature environment become a constraint on engineering application. So how to prepare coatingswith high infrared emissivity in the3~5μm wave band with a good thermal shock resistance hasbecome the key technology of praparation of high emissivity coatings. In this thesis, the relationshipbetween the thermal resistance and ahesive structure as well as the relationship between the infraredemissivity and the filler structure were systematically studied. Meanwhile, the mechanism of thermalshock resistance of the coating was studied, too. The inherent relationship and physical naturebetween the preparation of filler and the infrared emissivity of the coatings were systematicallystudied by experimental research. By adjusting process parameters, high emissivity coatings with highinfrared emissivity near to0.92at600℃were prepared. The role and mechanism of a variety ofcoating additives in improving the thermal shock resistance of high infrared emissivity coatings forhigh temperature, were obtained. Then the thermal shock resitance of coatings was improved.The main findings and conclusions were as follows:1. By studied the desigh principle of high temperature coating, the qualifications of hightemperature adhesives were obtained. The results indicated that a strong bond and spatial networkstructure were contributed to thermal resistance. Meanwhile, the inherent relationship and physicalnature between the infrared emissivity and the coating microstructure were obtained through studyingthe desigh principle of high emissivity coating. The results indicated that high infrared emissivityfillers must have the spinel structure of which the emissvity in the3~5μm band had a increase due tothe presence of chemical doping and the intensified of the electronic transitions.2. Acording to the desigh principle, effect of adhesive structure and modified adhesive propertieson thermal resistance of adhesive were examined. Meanwhile, the filler composition, heat treatmenttemperature and heat treatment time were examined. It found that copper oxide play an important rolein preparation of spinel structure.3. By studied the preparation and optimization techniques of high emissivity coating, thecoatings with high infrared emissivity in the3~5μm band near to0.9at600℃. And there was a positive temperature coefficient effect between the infrared emissivity and the temperature.4. The dynamic thermal environment performance such as thermal shock resistance of thecoatings was studied. The thermal shock resistance was improed through the adhesive modified, fillermodified and substrate pre-modified, respectly.