Infrared Radiation Properties Of Doped MgFe₂O₄/Hollow Calcium Phosphate Composite Phosphate Composite

In this thesis,Mg_1-xMn_xFe₂O₄ material was first synthesized by sol-gel-microwave sintering method.The infrared emissivity of Mg_0.5M_n0.5Fe₂O₄ was the largest,and the emissivity at 3–8?m and 8–14?m bands was 0.82 and 0.86,respectively.Due to the low mid-infrared emissivity of samples prepared by sol-gel-microwave sintering method,Mg_1-xMn_xFe₂O₄powders were synthesized by coprecipitation method.The results show that the emissivity of samples prepared by direct coprecipitation method is higher than that of samples prepared by sol-gel-microwave sintering method.Finally,Mg_0.5Mn_0.5Fe₂O₄ was coated on the self-made calcium phosphate hollow sphere surface by direct co-precipitation method to obtain Mg_1-xMn_xFe₂O₄/calcium phosphate core-shell composite.On the one hand,the calcium phosphate hollow sphere improves the far-infrared radiation performance of Mg_0.5Mn_0.5Fe₂O₄;on the other hand,Mg_0.5Mn_0.5Fe₂O₄ reduces the near-infrared reflection of calcium phosphate.Therefore,Mg_0.5Mn_0.5Fe₂O₄/calcium phosphate core-shell composites can be used to prepare far infrared textile materials,which can effectively absorb sunlight into heat and return heat to human body by thermal radiation.The structures and properties of the samples synthesized by sol-gel-microwave sintering method,co-precipitation method were compared.The results showed that different doping concentrations and processes had a great influence on the chemical composition,crystal structure,grain size,element valence and band structure of the samples,thus affecting the near-infrared reflectance and the infrared emissivity of the samples.XRD results show that the grain size and crystallinity of the sample prepared by direct coprecipitation method are the smallest,so it has a large emissivity.The emissivity of Mg_0.5Mn_0.5Fe₂O₄ in 2.5–8?m band and 8–14?m band are 0.86 and 0.88,respectively.For the near-infrared reflectance of the sample,the main mechanisms affecting it are free carrier absorption and particle scattering.The enhancement of free carrier absorption will decrease the reflectance,and the enhancement of particle scattering will increase the reflectance.The near infrared reflectance of Mg_0.5Mn_0.5Fe₂O₄ prepared by direct coprecipitation method is the lowest,and the average reflectance in the range of 800–2500 nm is only 17.54%.The influence of each layer of Mg_1-xMn_xFe₂O₄/calcium phosphate/calcium carbonate core-shell composite on its emissivity was analyzed,and the relationship of???₁+(1-?)(1-?₁)(?₂-?₁)was obtained.