Preparation And Improved Properties Of Ferrites-based Infrared Radiation Ceramics And Energy-saving Coatings

Infrared radiation materials can effectively enhance radiation heat transfer, improvetemperature distribution and reduce heat loss, which have been widely applied in areassuch as industrial furnaces energy-saving, infrared heating, and spacecraft thermalcontrolling because of the high energy-saving efficiency.In the past few decades, great advances have been achieved that the emissivity in8~20μm band for the infrared radiation materials has been over0.9. However, theemissivity in1~8μm band at high temperature was about0.5. The application andenergy-saving efficiency were restricted due to the poor infrared radiation performancein short wave band at high temperature. In order to solve this problem, the article wascarried out based on theory analysis and materials structure controlling and designing.Starting from Fe2O3, MnO2, Co2O3, CuO, NiO, SiC and Mg2Al4Si5O18, microwaveheating was used to prepare the infrared materials, the effect of heating process andchemical components on the structure and infrared radiation performance wasinvestigated systematically. In addition, plasma spraying technology and hypersonicflame spraying technology were selected to prepare amorphous and crystallized infraredradiation coatings respectively, and the influence of amorphous and crystalline structureon infrared emissivity was discussed. Finally, the research of the application of infraredradiation coatings in high temperature furnaces and civilian areas was conducted.The results show that the cordierite-ferrites based infrared radiation materials can besynthesized by microwave heating at low temperature or for short holding time (900°Cfor1h or1200°C for10min). The grain size of the obtained materials is small, andimproving temperature along with shortening holding time was benefit to decrease grainsize. With prolonging the holding time at1200°C, the infrared emissivity can beimproved, and the value in6~8μm band at800°C can be reached0.9by microwaveheating holding for1h, which is higher than that by conventional heating at1200°C for2h. The chemical component range of Fe2O3and MnO2has little effect on the infrared radiation performance, and the emissivity can be improved as the increase of cubicferrites contents, while playing finite contribution on the emissivity in short wave band.The amorphous coatings prepared by plasma spraying exhibit high bonding strength andexcellent thermal shock resistance. The infrared radiation in short wave band at hightemperature can be effectively improved for the amorphous structure that the emissivityin3~6μm band at800°C is over0.8, and the value in8~14μm is up to0.94. Theferrites-based infrared radiation coating prepared by hypersonic flame sprayingtechnology exihibtes high bonding strength of30.7MPa with the carbon substrate,which is much higher than that of the coating by brushing process (5.9MPa). Thecoating presents a typical laminate structure and particles among500nm~1μm in sizeare distributed on the coating surface. The emissivity value of the coating in detectedband at800°C is about0.75~0.83, which plays high energy-saving effect when sprayedon household kettle and the efficiency can reach30.5%, showing an attractiveapplication prospect.