Preparation And Properties Of Lanthanum Aluminate Based Infrared Radiation Coating

Infrared radiation coatings can effectively improve the emissivity of the coating substrate,which strengthen the radiation heat transfer to the substrate,so as to achieve the purpose of energy-saving or thermal protection.The performance of infrared radiation coatings depends on the high emissivity infrared radiation powder.At present,the high emissivity powder mainly composed of carbides,silicides and borides.However,there are two serious defects in these materials:The infrared emissivity is relatively low in the 3⁵?m band;Poor oxidation resistance,which infrared emissivity attenuation serious.Therefore,it is necessary to develop a high emissivity coating on 3⁵?m for energy-saving applications at high temperature thermal field.Ni ion doped La Al O₃ based infrared radiation material was synthesized by solid state high temperature synthesis.The effect of Ni ion doping on the infrared radiation properties of the samples was studied.The research shows that 40 mol%Ni doped La Al O3 has an infrared emissivity as high as 0.93 and 0.91 in 0.76².5?m and 3⁵?m respectively.Ni ion doped La Al O₃ ceramic with a high infrared emissivity was synthesized via a sol-gel process.The results show that Ni ion doping can improve the performance of infrared absorption of La Al O₃ ceramic.The synthesized La Al_0.6Ni_0.4O_2.89 powder has the superior absorption properties when the Ni ion doping amount is 40 mol%.Thereafter,the precursor La Al_0.6Ni_0.4O_2.89 powders were calcined with different heat treatment temperatures,and the average grain diameter of La Al_0.6Ni_0.4O_2.89nanocrystals was found to be about 9 to 54.3 nm.Effect of calcination temperature on the crystal size of the nanoparticles and the mechanism of nanocrystallite growth was investigated.The results showed that due to the surface plasmonic effect of nanoparticles,the infrared emission of La Al_0.6Ni_0.4O_2.89 nanoparticles in 0.76².5?m and 3⁵?m band reached the maximum value,0.98 and 0.95 respectively at 750?.when aluminum hydroxide,aluminum sol,silica sol and sodium silicate glass are used as binder,the emissivity is 0.93 in the spectral region of 3⁵?m.Thermal shock resistance of La Al_0.6Ni_0.4O_2.89 coating was tested.After 50 thermal shocks,thermal shock resistance was superior.The improvement of infrared emissivity is due to Ni levels in the band gap,and producing the activation energy of only 0.03 e V performance of La Al O₃-based ceramic materials.La Al_0.6Ni_0.4O_2.89 as basic material was prepared by infrared radiation of high emissivity of the infrared radiation coating,in order to test that the energy-saving effect of the prepared infrared radiation coating.The results indicated that the energy-saving effect of the coatings is significant in both constant power and constant temperature condition,and the heating rate was increased.The infrared radiation heating performance of La Al_0.6Ni_0.4O_2.89 coating was investigated via the crucible heating.The result shows that the coating has a significant effect of enhanced radiation heat transfer,and the energy saving rate can reach 28.8%.This novel material with a high infrared emissivity shows promising applications for energy-saving in the field of thermal processing equipment.