Preparation Of Spinel Copper Ferrites With High Infrared Radiation Performance

Nowadays,reasonable and effective utilization of renewable resources and exploration of innovative energy-saving materials has become an urgent priority for sustainability.High infrared radiation materials with excellent radiation power,high temperature oxidation resistance,and high infrared emissivity can be applied in high-temperature industrial furnaces,infrared heaters,aerospace,and electronic devices to achieve efficient energy use and reduce energy consumption.However,the relatively expensive cost and poor performance of existing high-infrared radiating materials do not fully meet the needs of practical applications.Among various high infrared radiation materials,spinel copper ferrite（Cu Fe₂O₄）exhibits considerable applied potential within the field of high infrared emission owing to the abundance and cheapness of copper and iron elements as well as the advantages of spinel structure easily subjected to lattice distortion and transient dipole moment changes.Consequently,the thesis concentrates on the design and synthesis of spinel copper ferrite materials possessing low-cost and outstanding high temperature infrared radiation properties.The emphasis is on the optimization of the fabrication process,the structural design,and the heterogeneous element doping in order to obtain superior high temperature infrared radiation characteristics in the 3?5μm wavelength band,and further investigate the conformational relationships and the intrinsic radiation mechanism.Detailed researches include the following:（1）A solid-phase synthetic route and the introduction of polyvinylpyrrolidone（PVP）as a burning aid enabled the synthesis of spinel Cu Fe₂O₄ at a lower temperature（800°C）.Firstly,single-crystal nanoparticles contain carriers that are less likely to be scattered than non-polycrystalline ones,resulting in a higher carrier concentration in Cu Fe₂O₄ spinel,which is beneficial for the enhancement of infrared radiation properties.And the addition of PVP can promote grain growth,decrease the synthesis temperature of tetragonal Cu Fe₂O₄ and reduce energy consumption to some extent.In addition,the effects of various experimental parameters,such as sintering temperature,ramping rate,and PVP mass,on the infrared radiation behavior of the ultimate product were thoroughly researched.Eventually,the infrared emissivity of the Cu Fe₂O₄ samples prepared under the optimum experimental conditions could reach～0.986 at the test temperature of 800°C.（2）A two-step strategy of solvent heat and subsequent calcination was adopted to design and synthesize the Cu Fe₂O₄ micro-nano spherical structures assembled by single crystal nanoparticles.From a structural design aspect,the small overlap area between two spherical particles facilitates enhanced infrared absorption,thus improving the infrared radiation performance.As for the internal bulk phase structure,the existence of single-crystal nanoparticles can offer a higher carrier concentration,and a series of phase/structure characterizations revealed that the Cu Fe₂O₄ microspheres（CFO-800）prepared at a calcination temperature of 800°C have the narrowest band gap and the most abundant oxygen vacancies.Benefiting from this unique microstructure assembled by single crystal nanoparticles and the excellent intrinsic properties,the CFO-800 specimen exhibits extremely high infrared emissivity value in the band of 3?5μm at a test temperature of 800°C.（3）The solution-gel method was used to successfully construct porous honeycomb-shaped nickel-doped Cu Fe₂O₄ spinel materials.On the one hand,the porous honeycomb structure provides substantial porosity to not only promote the infrared absorption of the Cu Fe₂O₄ filler but also to effectively mitigate the interfacial stress between the coating and the stainless steel substrate.On the other hand,a suitable proportion of Ni²⁺was introduced resulting in a range of favorable variations in the internal bulk phase structure of Cu Fe₂O₄,such as the largest lattice strain,the wealthiest oxygen vacancies,and the narrowest band gap.As a consequence of the synergistic interaction for these features,the 15%Ni-doped Cu Fe₂O₄ products（i.e.,CNFO-15）present outstanding infrared radiation performance over the wavelength range of 3?5μm.Moreover,the CNFO-15 based coating was prepared by air spray technique using CNFO-15 as the filler.Microstructural and emissivity investigations revealed that the coatings exhibited excellent high temperature high infrared radiation properties（～0.978）and remarkable thermal shock resistance.