Study On Membrane Material Of Infrared High-emissive Metal Oxides Modified By POSS

When spacecrafts fly at high speeds, severe high temperature flight environmentwill occur by its intense friction with the atmosphere, which will have a great impact tothe spacecraft internal control system. Therefore, the study of thermal protection systemhas caused wide research attention. The high emissivity coating on the surface ofspacecrafts is one of the methods to solve this problem. The emissivity of materials isclosely related with its radiation performance, so that the infrared radiation coating withexcellent performance should have high emissivity. The current main research directionof high emissivity coating is to raise its emissivity.The main topic of our research is to improve the film-forming ability of the coating,and use the sol-gel method to synthesize different structural POSS systems as the binderagent. In addition, Na2B4O7·10H2O, ZnO, CaO are used as the main components, addedwith some other metal oxides, such as Al2O3, BaO and MgO to prepare the lowtemperature glaze materials. Emissive coatings are mainly made by molybdenum,silicon and aluminum oxides, added with cobalt, nickel, zirconium, transition metaloxide as secondary components. With the brushing method, coatings are made on thesubstrate layer by layer. The thickness of coating is controlled by the mass per unit areaon the substrate. Samples are formed after80oC,100oC,120oC by gradual heatingmethod. According to the experimental designs, differences of properties are studiesafter different sintering temperatures.The structures of original coatings are characterized by FT-IR, TEM and XRD test.Surface morphology was analyzed by SEM tests. In addition, the energy spectrum of thecoating, the coating insulation and emissivity is tested.According to the data of XRD, the coating materials formed CoAl2O4spinelstructure, NiAl2O4spinel structure after800oC sintering, which greatly increased theemissivity and thermal shock resistance of the coatings. Thermal shock resistance of thecoatings is especially excellent when NiAl2O4spinel was formed. The low temperatureglaze is helpful to improve the thermal shock resistance, and thermal shock resistancedecreased with the temperature increased.The emissivity of Mo-Si-Al-Co-Ni and Mo-Si-Al-Co-Zr series changes mostslowly as the temperature changes, and the final balance temperature is the lowest,which indicated the radiation effect of the coatings. Insulation performance ofMo-Si-Al-Co-Ni and Mo-Si-Al-Co-Zr series coatings are more prominent, After heattreatment at450oC, is higher emissivity the Mo-Si-Al-Co-Ni coating is relatively highat whole waveband. Between2.5~5m its emissivity is almost1. The trend of othersystems is almost the same. After comparisons of comprehensive properties, POSS has increased the film forming ability of coating after added. But the dosage will have animpact on the thermal resistance ability and film forming temperature of the lowtemperature glaze materials. The results showed, the ratio of1:2of POSS50andPOSS60added into the material will have the best the thermal resistance ability andfilm forming temperature.