【作者】 范德松；

【导师】 宣益民； 李强；

【作者基本信息】 南京理工大学 ， 工程热物理， 2013， 博士

【摘要】 随着被控温系统与设备的散热功率密度和热负荷的迅速增加、内外热流变化程度的加剧以及控温精度的进一步提高,对基于热辐射表面的热控制与热管理技术提出了更新更高的要求。传统的热辐射表面因其热辐射特性不具备自动调节控制能力,无法根据系统与设备的发热量变化、外部热流变化去调节自身的热辐射特性,无法满足系统与设备的温度自主控制要求。基于热致变色原理的热辐射表面可根据系统与设备的温度水平、内外热流变化状况,自动调节自身辐射特性,从而可实现系统与设备温度的主动控制。因此开展基于热致变色原理的表面辐射特性转变机制与控制方法研究具有重要的现实意义和应用价值。本文以钙钛矿型锰氧化物La1-xAxMn03(A=Ca,Sr,K)为基础材料制作基于热致变色原理的热辐射表面,研究其热辐射特性,探索其辐射特性的控制方法,揭示其空间粒子辐照效应,对于研制基于热致变色原理的智能型热控器件、对提高系统与设备的热控技术水平有重大的科学意义。论文的主要研究内容包括以下几个方面：(1)热致变色功能材料制备与表征以稀土氧化镧,碳酸盐,二氧化锰为原料,拟用固相反应法制备块体热致变色功能材料,拟用等离子喷涂法制备热致变色涂层。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、原子力显微镜(AFM)、样品振动磁强计(VSM)和多功能物理量测试系统(PPMS)对热致变色功能材料的物相、微观形貌、表面粗糙度、磁性能、电输运性能进行表征和测量。分析了掺杂碱金属元素或碱土金属元素的种类、掺杂浓度、烧结温度对热致变色功能材料晶体结构、或致密度、或电磁输运特性、或相变温度的影响,为研制智能型热控器件提供技术支持。(2)基于热致变色原理的表面热辐射特性研究以热致变色器件和热致变色涂层为研究对象,用红外光谱仪和分光光度计测量其反射率光谱,根据反射计光学方法间接测量其红外发射率和太阳吸收率。分析掺杂元素种类、浓度以及表面状况对基于热致变色原理的表面热辐射特性的影响,揭示其发射率可调特性。结果表明：Ca和/或Sr掺杂的热致变色器件,反射率随温度升高而降低；在合适的Ca和/或Sr浓度下,热致变色器件出现金属-绝缘转变,从而引起热致变色器件发射率急剧转变,其中,仅有Ca掺杂时,发射率在相转变温度附近变化最剧烈,但转变温度较低；而仅有Sr掺杂时,发射率也发生急剧转变,但转变温度较高;同时掺杂Ca和Sr,可将热致变色器件的转变温度调节到所需的范围,并维持发射率的剧烈变化,发射率变化幅度超过0.5；不同掺杂情况下,热致变色器件的太阳吸收率都较高,达到0.78；通过优化等离子喷涂参数,获得发射率可调特性的热致变色涂层；由于受涂层表面粗糙度、喷涂工艺的影响,涂层的发射率变化幅度有所不同,其中最大可调幅度为0.33,而太阳吸收率高达0.85；以Ca, Sr, K三种元素为基础,采用不同的组合方式、掺杂浓度,都不能达到降低热致变色器件高太阳吸收率的目的。(3)热致变色器件辐射特性耦合控制方法研究针对热致变色器件太阳吸收率较大的问题,开展热致变色器件热辐射特性的控制方法研究,探索降低热致变色器件短波太阳吸收率、同时维持热致变色器件长波红外发射率可调的方法,实现热致变色器件热辐射特性在不同波段范围的耦合控制。将基于多层薄膜结构的选择性光谱控制用于实现热致变色器件表面热辐射特性控制,采用模拟退火遗传算法优化设计多层薄膜结构,建立多层薄膜结构内部热辐射传递理论模型,计算分析多层薄膜材料属性、膜层数、膜层厚度、以及膜层排列方式对多层薄膜结构热辐射特性的影响,研究由多层薄膜结构和原热致变色器件组成的复合型热致变色器件结构的热辐射特性。理论计算表明,增设多层薄膜结构后,太阳吸收率从原来的0.78降低到0.21,有效地削弱了到达热致变色器件表面的太阳辐射,并较好地透过红外热辐射。采用电子束蒸发沉积法将最优多层薄膜结构沉积到原热致变色器件表面以制备复合型热致变色器件,并测试其热辐射特性,结果发现,复合型热致变色器件不仅具有低太阳吸收率(αs=0.28)的特性,而且还维持了发射率的可调特性,其可调幅度与原热致变色器件相同,也验证了红外发射率与太阳吸收率的耦合控制方法。(4)热致变色器件空间粒子辐照效应研究热致变色器件用于卫星热控领域,会受到空间环境中诸多因素的影响,特别是来自于空间环境的粒子辐照影响。为了弄清楚热致变色器件是否能经受空间环境的考验,本文通过地面模拟空间粒子辐照实验,研究不同能量的电子和质子辐照对热致变色器件热辐射性能的影响,探索热致变色器件在空间环境中应用的稳定性。结果表明：空间粒子辐照诱导非复合型热致变色器件内部晶体结构氧缺陷,引起其太阳吸收率和红外发射率增大,造成其热辐射性能退化；而复合型热致变色器件在空间粒子辐照环境下具有非常好的稳定性,其太阳吸收率和红外发射率没有发生退化。更多还原

【Abstract】 With the power density of heat dissipation and the heat load in a system increas-ing, there is a growing demand for a better performance of thermal radiative surface because these with constant emissivity cannot meet the demand any more. For ex-ample, thermal radiative surface, such as ZnO coating and OSR reflector, are usually used to dissipate heat from the satellite surface. However, these traditional thermal radiative surface have a constant emissivity, they don’t adjust their thermal radiative properties alone in response to the violent fluctuation of exterior heat flux. Therefore, there is a serious need for developing novel thermal radiative surface with its radia-tive properties automatically adjusting in response to a variation temperature for the next generation thermal control system applications. In this dissertation, perovskite-type manganese oxides La1-xAxMn03(A=Ca, Sr, K) were selected as a basic material to prepare a novel thermal radiative surface, and investigation on thermal radiative properties of surface and its control method based on thermochromic phenomenon was performed. The contents of this thesis mainly include the following parts.(1) Preparation of thermochromic functional materialSolid stated reaction is used to prepare the bulk thermochromic functional ma-terial, and the plasma spray method is used to prepare the thermochromic coating. XRD, SEM, AFM, VSM, and PPMS are used to detect the phase structure, surface to-pography, RMS roughness, magnetic properties and electronic properties, respectively. These effects of doping element, doping level, or sintering temperature on the phase structure, densification, or phase transition temperature of thermochromic functional material are analyzed.(2) Thermal radiative properties of thermochromic functional materialReflectivity spectra of thermochromic device or coating are measured using the FT-IR spectrometer and spectrophotometer. The emissivity and solar absorptivity are deduced from the experimental reflectivity data. The mainly factors to affect the ra-diation properties of surface are presented. Experimental investigations are reported as follow:For the Ca and/or Sr doped samples, their reflectivity spectra increase with temperature decreasing. In an appropriate doping level of Ca and/or Sr, ther- mochromic functional surface shows a transition from metallic state to insulator, as a result, its emissivity is increases with temperature. If only the Ca element was doped in A site, the emissivity of sample changed dramatically in the vicinity of transition temperature, but the transition temperature is low. If only the Sr element was doped in A site, the emissivity of sample shows a sudden change near the transition temper-ature, and the transition temperature is high. So, it is possible that the the transition temperature can be adjust according to application needs and the emissivity variation can be maintained. Thermochromic coating with tunable emissivity properties is ob-tained by adjusting the plasma spraying parameters. The variation range of emissivity of thermochromic coatings are relation to the surface condition, and spray parameter. The largest increment of emissivity is0.33at present. A limitation of application was found in the thermal radiative surface due to its large solar absorptivity, which is difficult to be reduced only changing the doping level or element, such as Ca, Sr, or K.(3) Coupling control method of radiation properties of surface based on ther-mochromic phenomenonThe optical control method based on the multi-layer thin films is introduced to investigate the control of radiation properties of surface. A multi-layer thin films structure is designed onto the surface based on thermochromic phenomenon using sim-ulated annealing genetic algorithm. The effect factors on the thermal radiative prop-erties of complex functional surface, which consists of surface based on thermochromic phenomenon and multi-layer thin films, are shown in this thesis. The calculated re-sults reveal that multi-layer thin films can effectively reduce the solar radiation, which arrives to the surface of thermal radiative surface, and transmit infrared radiation simultaneously.According to the calculated results, the multi-layer thin films are deposited onto the thermochromic functional surface using the electron beam evaporation. The ther-mal radiative properties of complex functional surface are experimental studied. The experimental results show that complex functional surface is not only obtain a low solar absorptivity, but also maintain the temperature-dependent emissivity properties of thermochromic functional surface. Thus, the coupling control of solar absorptivity and infrared emissivity is confirmed.(4) Particles irradiation-induced degradation of radiation properties for the sur-face basing on thermochromic phenomenonInfluence of particles irradiation,60-1000KeV electrons and100KeV protons in energy, on the thermal radiative behaviors of surface basing on thermochromic phe-nomenon (i.e., thermochromic functional surface and complex functional surface) have been investigated. To evaluate thermal radiative degradation, their solar absorptivity, temperature-dependent reflectivity, and thermal emissivity are studied before and after particles irradiation. The thermal radiative degradation behavior in thermochromic functional surface is reported, and the degradation mechanism is discussed. In addi-tion, it is revealed that the thermal radiative properties of complex functional surface shows a excellent stability without degradation in simulation environment.更多还原