低温固化热致变色涂层辐射特性

Total hemispherical emittance of low temperature curing thermochromic coatings

以溶胶凝胶法制备的高纯La_(1-x)Sr_xMnO_3(x=0.125,0.175,0.2)纳米粉末为填料,分别以热塑性丙烯酸树脂和松油醇@乙基纤维素为基料制备成涂层浆料,并涂覆于铝基底表面,再分别以低温120℃和180℃固化La_(1-x)Sr_xMnO_3热致变色涂层.实验表征了纳米粉末的物相,表面形貌,观察了涂层的微观形貌.并利用稳态卡计法测量了热致变色涂层在173~370 K温度范围内全半球发射率随温度的变化.研究结果表明:两种不同树脂为基料的涂层都表现出热致变色特性,其发射率增幅达0.45.由于低温固化涂层制备工艺简单,能够适用于复杂表面的涂覆应用,在航天热控中具有潜在的应用前景.

Thermal control device based on thermochromis plays an important role in spacecrafts thermal management by automatically adjusting its radiative properities in response to large temperature gradients. The thermal management ability was determined by the device surface radiation performance. During the sun shadow, it is required to dissipate heat as little as possible from spacecraft, which is a low emittance device. While, it desired the device emittance is large enough to meet the heat dissipation requirement facing with the direct sunlight. As a type thermochromic material, La1-xSrxMnO3（LSMO） has obtained broad attention because it showed a considerable superiority in saving energy consumption in space thermal management. It can hold the heat at low temperature due to its low emittance behavior, whereas dissipate the excess heat at high temperature for its high emittance properties. In this work, we prepared the La1-xSrxMnO3（x=0125, 0.175, and 0.2） nanoparticles by sol-gel method from the precursors such as lanthanum nitrate hexahydrate, strontium nitrate and manganese nitrate solution（50%）. LSMO nanoparticles were dispersed homogeneously in a solution of resins. The mixture then was spin-coated on the clean Al substrates. After standing for 10 h, the coating was cured at 120℃. The structure, morphology, and composition analysis of LSMO nanoparticles or coatings were investigated by X-ray diffraction technique, scanning electron microscopy, and the energy dispersive X-ray spectroscopy, respectively. The total hemispherical emittance of coating was measured by calortmetric method, which test sample was suspended in the center of a liquid nitrogen thermostat. According to the input power, sample temperature, and thermostat temperature, the emittance can be indirectly obtained. Two resins, which is the acrylic resin and the solution of terpineol and ethyl cellulose respectively, was considered to investigated the effect of reslin type on the emittance of coatings. The result of X-ray diffraction shows a single perovskite structure for LSMO nanoparticles at different Sr doped level. A fined LSMO nanoparticle with 50–300 nm, which is detected using scanning electron microscopy, can be obtained by control sol-gel process. The composition analysis results show a comparable stoichiometric ratio. The two resins coating show a different surface morphology, which is more compact in acrylic resin than in the terpineol. Experimental results show that the variation amplitude of coating emittance is 0.45 within the temperature range of 173–370 K. For the acrylic resin coating, the emittance changes from 0.42 at 173 K to 0.85 at 370 K, and it rises from 0.39 at 173 K to 0.83 at 370 K in terpineol resin coating.