Prepared Method And Radiative Properties Of Thrmochromic Emittance Variable Coating

Thermal control device based on thermochromic phoneomenon plays an important role in spacecrafts and satellites thermal management by automatically adjusting its radiative properities in response to a large temperature gradients.Over the past decades, two kinds of thermal control device based on thermochromic phoneomenon have been studied, ceramic wafer prepared by solid stated reaction and thin-film obtained through magnetron DC sputtering techniques. However, the production of traditional ceramic wafer is complicated and low yield. Considering the high production cost and the limitation of batch manufacturing, magnetron DC sputtering technique has advantage on laboratory preparation. Compared with the two methods mentioned above, thermochromic coating by spin-coating is easy prepared and can meet the severe weight and complex surface limit of spacecraft. In this dissertation,we have prepared thermochromic coating and investigated their thermal radiative properties. The content of this thesis include the following three parts:(1) Preparation of theromochromic emittance variable coatingDifferent Sr/Ca and K-doped ratio perovskite-structure manganese oxide La1-xSrxMnO3 (x= 0.125,0.175, and 0.2) and La0.7Ca0.3-xKxMnO3(x=0.05,0.1,0.15) nanoparticles are successfully synthesized by sol-gel route are dispersed homogeneously in organic resin. Thin coating was deposited on substrate. The prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and vibrating sample magnetometry (VSM)(2) Calorimetric Measurements of the Total Hemispherical EmittanceAn apparatus is presented for measuring the hemispherical emittanc of thermochromic coating. It is designed especially for samples with rough surface.The error margin lies under 2% of the measured value.(3)Thermal radiative properties of theromochromic emittance variable coatingReflectivity spectra of high-tempertature sintering theromochromic coating are measured using the FT-IR spectrometer, the emittance of low-temperature solidifying coating are measured using the calorimetric measurements apparatus, respectively. These effects of Sr/Ca and K doping level、 organic resin、proportion of pigment on the thermal radiative properties of thermochromic coating are investigated.Experimental investigations are reported as follow:Within the temperature range of 173K-373 K, the variation amplitude of emittance is 0.26 and 0.42 for high-tempertature sintering LSMO coating and low-temperature solidifying coating, respectively. When the proportion of pigment is 40wt%, the variation amplitude of emittance is 0.39, and it will get maximun value with increasing proportion of pigment to 60wt%. However,when the proportion of pigment increas to 70wt%, the variation amplitude of emittance on the decrease.The emittance exhibits an abrupt rise around 253K for high-tempertature sintering LCKMO coating, and the variation amplitude of emittance is 0.48 for low-temperature solidifying coating.