【作者】 马杰；

【导师】 叶枫；

【作者基本信息】 哈尔滨工业大学 ， 材料工程， 2013， 硕士

【摘要】 相变材料在相变过程中会伴随较大的热量变化，且自身温度不发生明显变化，因此可用于储能或控温领域，将其引入高速飞行器的热防护系统中，可获得具有高效隔热控温性能的热防护系统。本文选用石蜡、硬脂酸、赤藓糖醇和甘露醇四种高潜热相变材料，以高孔隙率的氮化硅多孔陶瓷为基体支撑材料，利用熔融浸渗法制备了定形复合相变材料。研究了浸渗过程中的时间、温度参数对浸渗率的影响，并对复合相变材料微观形貌、相变材料与基体的相容性、热稳定性及热控隔热性能进行了分析研究。利用压汞法、SEM和DSC等测试手段对多孔氮化硅和相变材料进行了表征，结果表明多孔氮化硅基体具有高的孔隙率，相互连通的三维网络孔结构，且选用的石蜡、硬脂酸、赤藓糖醇和甘露醇四种相变材料具有高的相变潜热。研究了浸渗过程中时间t和浸渗温度T对浸渗率的影响，结果表明石蜡、硬脂酸、赤藓糖醇、甘露醇分别在浸渗温度为：70℃，80℃，150℃，200℃；浸渗时间为30min的条件下，浸渗进行完全，获得了浸渗率分别为41.46%、43.55%、50.32%、53.14%的高浸渗率复合相变材料，表明多孔基体对相变熔体具有很强的吸附能力和较好的润湿性。通过FTIR、XRD和DSC分析得出，相变材料和多孔氮化硅具有良好的化学相容性，融渗过程中没有新物质生成；四种复合相变材料的相变温度和相变焓分别为：53.17℃，54.12J/g；48.66℃，77.29J/g；118.08℃，191.13J/g；165.21℃，213.15J/g；另外，石蜡和硬脂酸复合相变材料的介电常数分别约为2.8和3.2，损耗角正切值范围分别在1.04~3.5110-2和1.12~1.4310-2范围内，基本满足透波材料的要求。对硬脂酸、赤藓糖醇和甘露醇三种复合相变材料的热控测试表明：三种复合相变材料的温度-时间曲线上均在其对应的相变温度附近出现明显的温度平台，温度平台持续的时间分别为：80s，360s，600s，其大小与相变复合材料的的相变潜热呈正相关，表明了相变材料在升温过程中起到了减缓温度快速升高的作用。对四种复合相变材料热稳定分析得出：石蜡、硬脂酸、赤藓糖醇和甘露醇四种复合相变材料的分解温度范围分别为：180℃~350℃；140℃~260℃；170℃~291℃；250℃~360℃；四种复合相变材料均具有良好的热循环性，经过5次冷热循环，相变材料失重很少，其中硬脂酸失重率最高为2.1%，石蜡、赤藓糖醇、甘露醇复合相变材料的失重率分别为0.66%，0.15%，0.20%。更多还原

【Abstract】 Phase change materials (PCMs) have the function of energy storage andtemperature control, because it can absorb a large amount of heat in an approximateisothermal process. Thus PCMs can be introduced into the high-speed aircraftthermal protection system (TPS) to improve the performanee of TPS. This workadopt paraffin wax, stearic acid, erythritol, mannitol as phase change materials andporous silicon nitride ceramic serves as the framework, and prepare form-stablephase change materials by the technology of spontaneous molten infiltration. theeffect of the parameters in infiltration process including infiltration temperature andtime on the mass fraction of PCMs in the composite, then the microstructure ofcomposite, the compatibility of phase change materials and the matrix, thermalstability and thermal control properties of the composites were characterized.The properties of porous silicon nitride and the phase change materialsarecharacterized by a series of test means, such as mercury intrusion porosimetry,SEM and DSC etc. The results indicate that the porous silicon nitride have athree-dimensional network of interconnected pore structure, and the phase changematerials of paraffin, stearic acid, erythritol and mannitol has a high latent heatstorage capacit。The infiltration process is researched by considering infiltration temperatureand time, the result shows that under the best infiltrating conditions which are70℃,80℃,150℃,200℃for paraffin wax, stearic acid, erythritol, mannitol,30min,PCMs reach infiltrating saturation. the mass fraction of the PCMs in the compositeis respectively41.46%、43.55%、50.32%、53.14%, it indicates that the porous matrixhas a strong adsorption capacity and good wetting to the liquid.of PCMs.There is noreaction among the PCM-porous silicon nitride ceramic composite according thechemical and phase analysis with FTIR,XRD, and no produce new substance. Thematerial phase change temperature and enthalpy of the four kinds of phase changecomposite are:53.17℃,54.12J/g;48.66℃,77.29J/g;118.08℃,191.13J/g;165.21℃,213.15J/g. In addition,the dielectric constant of paraffin and stearic acid compositephase change material are approximately2.8and3.2, the values of their loss tangentare in the range1.04~3.51×10-2and1.12~1.43×10-2range, basically meet therequirements of wave-transparent materials.The experiment are proposed to investigate the thermal absorb characteristicsof porous silicon nitride infiltrated with PCMs for thermal protectionapplications.,the result shows that there is a significant temperature platform in the temperature-time curves of three kinds of stearic acid,erythritol,mannitolcomposite phase change materials, the duration of the temperature platform are:80s,360s,600s.having a positive correlation with the phase change latent heat. Itindicates that PCMs acts as thermal absorb material limiting the temperatureabruptly rising.The result of thermal stability test shows that the decompositiontemperature ranges of paraffin wax, stearic acid, erythritol and mannitol are:180℃~350℃;140℃~260℃;170℃~291℃;250℃~360℃; The result of thermal cycleexperiment shows that phase change composites have little weight loss, of whichthe stearic acid composite has the highest weightlessness rate which is2.1%, theweightlessness rate of paraffin, erythritol, mannitol composite phase changematerial are0.66%,0.15%,0.20%.更多还原