Study On Preparation And Testing Of High Radiation Coating

Due to the high emissivity, stable crystal lattice in middle and hightemperature, minerals whose octahedral voids are occupied by Fe、Co、Ni asFeFe2O4、CoFe2O4、NiFe2O4and other trans-spinel have been widely used inhigh temperature field as high radiation coating.In this thesis, the trans-spinel NiFe2O4powder for high radiation coatingwas synthesized by high-temperature solid state method using iron oxide(Fe2O3) and nickel oxide (Ni2O3) as raw materials. The appropriate inorganicbinder was selected to mix with the powder to obtain a special kind ofdope.The high radiation coating was prepared on304stainless steel plate bygas spray method using as-prepared dope. The influences rule of thepreparation process of dope and coating on the performance of as-preparedhigh radiation coating has been systemly studied. According to therequirements of the study, two sets of emissivity testing apparatus wereestablished and developed based on the principles of steady-state calorimetricmethod and radiation energy method.Main research results are as follows：（1）A high emissivity pigment precusor-trans-spinel NiFe2O4could beprepared by high-temperature solid state method using iron oxide (Fe2O3) andnickel oxide (Ni2O3) as raw materials after more than900℃heat-treatment;（2）The binder performance had a great influence on the emissivity ofthe coating, the coating made of an aqueous solution of sodium silicatetogether with NiFe2O4powder has a higher emissivity. （3）NiFe2O4synthesis temperature makes a greate influence on theemissivity of infrared coating. When the synthesis temperature is1200℃, theobtained coatinghas a maximum infrared emissivity.The finer the particle sizeof filler, the higher the emissivity of as-prepared infrared coating.Theemittance of the coating first increased quickly with the increase of thethickness, and then declined slowly after reaching a peak value, finallyreaches a certain value.The results showed that it has the highest emissivitywhen the coating thickness is0.08mm.（4）The problem of high-temperature emissivity testing technique hasbeen resolved through developing two sets of emissivity testing apparatus.The apparatus based on the radiation energy method can be quickly and easilygive the emissivity value, which overcome the shortage of the previousdevicethat it must be configured with two blackbody source, and the testtemperature limit is1000K. The apparatus based on the Steady-statecalorimetric method is currently the only highest temperature domestic devicetest temperature up to the2200℃.