【作者】 郭军；

【导师】 何飞；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2012， 硕士

【摘要】 Al-Si合金是一种具有高储能密度的高温相变材料。但其熔化状态下的高腐蚀性是制约该材料实际应用的主要原因。因此，对Al-Si合金进行有效地封装具有重要的研究与实用价值。本论文针对此问题，探索了一种Al-Si合金粒子微封装的有效方法，并对制备的Al-Si/Al₂O₃核壳结构粒子进行了分析与表征。研究中，基于溶胶—凝胶原理，分别采用直接包覆法、偶联剂改性溶胶法和偶联剂改性粉体法，在Al-Si合金粒子表面包覆Al₂O₃壳层，形成了Al-Si/Al₂O₃核壳结构。结果表明，直接包覆法制备的Al-Si/Al₂O₃核壳结构壳层致密性较差，粒子之间有着严重的粘连，粒径不均匀；偶联剂改性溶胶—凝胶法制备出的Al-Si/Al₂O₃核壳结构粒径相对均匀，粒子之间没有严重的粘连，但是其干燥阶段容易出现开裂；偶联剂改性粉体法制备出的Al-Si/Al₂O₃核壳结构粒子具有壳层致密、粒径均匀、粒子之间不粘连等优点。研究了制备工艺参数对偶联剂改性粉体法制备Al-Si/Al₂O₃核壳结构粒子的影响。结果发现，经过偶联剂改性之后，Al-Si合金表面形成一层致密的分子层，表面变光滑。在溶胶的固含量为仲丁醇铝与水的摩尔比为1:80时，壳层较为完整。30℃条件下的干燥，可将由干燥造成的壳层开裂降到最低。700℃与900℃烧结形成的壳层呈疏松多孔状态；1200℃烧结则形成致密光滑的壳层。XRD分析表明，1200℃烧结后，壳层的Al₂O₃完全转化为-Al₂O₃。SEM分析证实，包覆后的Al-Si合金粒子呈明显的核壳结构，壳层为致密完整的单壳层，没有裂纹与孔洞出现，厚度约为3μm。壳层的主要成分为Al₂O₃，主要源于Al₂O₃溶胶对Al-Si核心的包裹。Al-Si/Al₂O₃核壳结构粒子的储热能力分析表明，包覆之后，该材料的熔点为572℃，与包覆之前基本相同；相变潜热下降为307.2J/g；经15次热循环之后，表面壳层完整致密，无明显的裂纹与壳层剥落；20次热循环之后，氧化增重为3.75wt.%，相变潜热下降为215J/g。Al-Si合金粒子内核与Al₂O₃壳层间存在的气孔和缝隙，是壳层抵抗因固液相变造成体积膨胀导致其开裂的原因之一。以Al-Si/Al₂O₃核壳结构粒子为相变材料引入多层隔热结构模拟结果显示，当其位于位置参数d=0.4时，具有最明显的“削峰填谷”隔热效果。模拟结果证实相变材料在多层隔热结构中的合理设计是有效地发挥相变材料作用的关键。更多还原

【Abstract】 Al-Si eutectic alloy is an ideal high temperature phase change material （PCM）because of its high latent heat value. Molten Al-Si alloy, however, possesses highcorrosion, which is the main reason of its restriction application. It is valuable toexplore a new effective method to encapsulate Al-Si alloy particles. In this paper, amethod of micro-packing Al-Si particles was investigated. The structure and phaseproperties of Al-Si/Al₂O₃core-shell micro-particles were analyzed.Based on the theory of sol-gel method, Al-Si/Al₂O₃core-shell micro-particleswere synthesized by direct-packed sol-gel method, coupling agent modified sol-gelmethod and coupling agent modified Al-Si particles method. The results show thatthe shell prepared by the direct-packed method is not dense and there are someconnected dots among the core/shell particles. Those prepared by coupling agentmodified method show little connected dots, but the shell is easily broken duringthe drying course. Those synthesized by coupling agent modified particle methodexhibit the best core-shell structures, such as dense core-layer, intact and noconnected dots among particles.The influences of synthesis parameters were studied to prepare Al-Si/Al₂O₃core-shell micro-particles by coupling agent modified Al-Si particles method. Adense layer of coupling agent is found on the surface of the modified Al-Si particles.Compared with the rough surface of the raw Al-Si particles, the smooth surface isobtained. The integrated shell is formed when the mole radio of aluminum tri-sec-butoxide and water is1:80. The drying temperature at30℃is suitable to reducethe crack on the surface of the shell. The dense and smooth shell is obtained afterheating treatment at1200℃, while porous shell is formed at700℃and900℃. Thephase of shell layer is-Al₂O₃after the particles are sintered at1200℃. It isapparent that core-shell structure is formed by the means of SEM. The shell isdense, integral and possesses single layer without crack and pores. The componentof shell layer is Al₂O₃that mainly originates from alumina sol in the course of thesol-gel.The results of heat storage of Al-Si/Al₂O₃core-shell micro-particles show thattheir phase temperature is572℃that is consistent with the raw Al-Si alloy particles. The latent heat reduces to307.2J/g. High temperature recycling experimentexhibits that after15times thermal treatment circles, Al₂O₃shell is still dense,integrated and no obvious cracks. After20times thermal treatment circles, its latentheat decays to215J/g and the mass increases3.75wt.%because of the oxidation.The gap between Al-Si alloy core and Al₂O₃shell is one of the reasons preventingthe shell to be broken during the course of phase change from solid state to liquid.The results of thermal conductive simulation reveal that when d=0.4, themulti-layer structure shows the most obvious thermal insulation effect, after Al-Si/Al₂O₃core-shell particles are added into multi-layer insulation as PCM. Thereasonable design of PCM located in the multi-layer insulation is a key step forrealizing the action of PCM.更多还原