【作者】 胡晨；

【导师】 徐国跃；

【作者基本信息】 南京航空航天大学 ， 物理化学， 2010， 硕士

【摘要】 随着航空航天技术的发展,发动机作为飞行器的最高热源具有明显高辐射的特点,其工作温度一般在750K～900K,其热辐射的能量主要分布在红外3~5μm范围内,这就要求红外低发射率涂料在高温下具有优异的热稳定性,虽然有较多的高温保护涂料的研究,但是这些研究都不涉及红外低发射率方面。本课题的目的在于制备在3~5μm波段具有低发射率的涂料,此涂料能在750K~900K条件下正常使用。通过选择合适的无机以及有机耐高温基体,添加不同类别的颜填料,制备具有低发射率的耐热涂料。对涂料的制备工艺参数进行优化设计;对涂料表征分析,测试发射率性能,力学性能和耐高温性能;对涂料的低发射率性能进行深入的研究,分析涂料的热失效机理,采用添加耐热添加剂进行改善。主要的研究结果和结论如下:1.氧化铅磷酸盐涂料经过500℃固化形成涂层,其常温下3~5μm波段发射率为0.51。涂料在高温固化过程中的脱水缩合和晶型转变,形成了紧密的结构和降低了红外吸收率,使红外发射率降低。2.成功制备了耐热型低发射率涂料,对涂料的制备过程进行优化,其中,铝粉添加量在30%~40%时,经过400℃固化2小时后,3~5μm波段发射率最低可达0.16~0.19。分析了颜填料含量、粗糙度、涂层厚度的影响。耐热型低发射率涂料具备低红外吸收和形成致密的片层连续结构的特点。3.有机硅基红外低发射率耐热涂料的耐受温度为500-600℃,具有良好的耐热性能和一定力学性能,实测过程中明显降低了中心锥的热辐射。4.分析了耐热型低发射率涂料在热失效的原因,分为树脂基体的高温分解和颜填料的高温氧化.5.选用氧化锌作为耐热添加剂,对提高有机硅基体的耐热型低发射率涂料的耐热性能有一定的效果。更多还原

【Abstract】 In recent years, infrared guided weapons have become the main threats to aircrafts.As we know, the coating exterior surface of the aircraft with low emissivity materials can greatly decrease the probability of being detected by infrared detector. However, most of the low emissivity coatings present poor thermal resistance properties and can not be used at the high temperature components of aircraft, such as the exterior surface of the tailpipe, whose working temperature range is 450-700°C. Thus, the preparation of low emissivity coatings with good thermal resistance properties is of great importance for infrared stealth technology applications.In this paper, the thermal resistance coatings with low emissivity were prepared via a simple and convenient process. And the influence of chemical composition, surface structure, roughness and thickness on the emissivity was discussed. The experimental emissivity results are nearly consistent with optical theory analysis for the coatings. Furthermore, thermal ageing and thermal shock resistance of the coatings were also systematically investigated.1. The emissivity of the coating can reach to 0.51 in the 3~5μm and the coating can work at high temperature by solidification process. The condensation reaction and crystal phase change in the solidification process result in the tight structure and the decrease in infrared absorbance, which is the main factor of variable emissivity.2. Thermal resistance coatings with low infrared emissivity can reach to 0.16~0.19 in the 3~5μm. The influence of content of Al powders, roughness and thickness on the emissivity was systematically investigated. Reducing infrared absorption as well as the formation of dense continuous t laminar aluminium structure may account for the lower emissivity of coatings.3. Thermal resistance polysiloxane/Al coatings with low emissivity could be used at 500-600℃. The coatings exhibited favorable thermal ageing and excellent resistance to thermal shocking. The thermal radiation of center cone decreased to 40%.4. The emissivity property of low infrared emissivity coatings was studied during the thermal ageing and thermal shocking. This effect was explained by thermal oxidation of Al particles and polysiloxane degradation in the coatings.5. The thermal resistance property of low emissivity coatings can be enhanced by ZnO.更多还原