The Preparation And Performance Study On Ni-Cr Spinel Radiation Coating Doped By Boride

High infrared emissivity coating possesses great value in practical application in both civil and military fields due to its excellent infrared radiation property.At present,the spinel structure infrared ceramic material has became the hotspot of research.Studies have shown that in order to further improve the whole emissivity,the emissivity of coating in short-wave band must be improved.In this paper,to enhance the emissivity of NiCr₂O₄ spinel coating in short infrared band,CoO and ZrB₂ were doped into original powder of spinel material respectively.The coatings were prepared and the property of coatings were researched.Air plasma spraying?APS?is one of important way to manufacture infrared radiation ceramic coating.The technological parameter of APS determines the quality of coating.In this paper,the spray current was adjusted to observe the influence of current on the quality of coating and to find the appropriate technological parameter for fabricating the infrared radiation coating.Results show that good quality coating can be obtained when spraying current is 500A and spraying voltage is 70V.Compositing is one of the most efficient method to improve the emissivity of coating.In this paper,the powder contains NiCr₂O₄ spinel and CoCr₂O₄ spinel was obtained by sintering the raw powder of CoO,NiO combined with Cr₂O₃.The spinel powder was used to fabricate infrared radiation coating by APS.The results show that the lattice distortion and infrared emissivity of material is increased by the replacement between Co²⁺and Ni²⁺.The infrared emissivity of NiCr₂O₄ spinel coating and CoO composite NiCr₂O₄ spinel coating is 0.851 and 0.880,respectively.With the increase of test temperature,the infrared radiation performance of the coatings gradually increased,and the infrared emissivity reached 0.868 and 0.896 at1000?,respectively.Boride is a kind of infrared radiation material with potential and research value.In this paper,ZrB₂,NiO and Cr₂O₃ agglomerated powder has been prepared by high temperature roasting,and a new material Ni₂CrO₂?BO₃?suitable for infrared radiation coating has been found.With the testing,it is found that Ni₂CrO₂?BO₃?can increase the infrared emissivity of NiCr₂O₄ spinel coating from 0.880 to 0.895.The reason for the increase of infrared radiation performance by Ni₂CrO₂?BO₃?is the asymmetry of the lattice vibration of the borosilicate structure and the transition of the electron.The roasting temperature of the powders were determined by the thermogravimetric analyzer,then the powders were roasted in muffle furnace.The infrared radiation coating were prepared by air plasma spraying.The phase of powders were analyzed by X-ray diffraction.The surface morphology of powders and coating,the cross-sectional morphology of coating were analyzed by scanning electron microscopy.The radiation properties of coatings were tested by Fourier infrared spectrometer and national infrared and industrial electric heating products quality supervision and inspection center.