【作者】 许二超；

【导师】 王周福；

【作者基本信息】 武汉科技大学 ， 材料物理与化学， 2010， 硕士

【摘要】 本文综述了相变储热材料的特点及研究现状,讨论了高温相变储热材料的结构、性能及制备方法。对原位反应烧结法制备高温复合相变储热材料的影响因素进行了研究,研究了熔盐含量、熔盐配比以及石墨加入量对材料结构和性能的影响。以镁砂和刚玉为形成镁铝尖晶石陶瓷基体的原料,熔盐作为反应介质,同时作为相变材料,通过原位反应烧结法制备了熔盐/尖晶石基高温复合相变储热材料。研究了烧结温度、不同氧化镁/氧化铝配比、熔盐种类对熔盐/尖晶石基高温复合相变储热材料性能的影响,通过XRD、SEM等分析测试技术对材料进行表征。结果表明,适宜的烧结温度为1000℃,氧化镁/氧化铝配比为理论尖晶石配比,相变材料为KCl-KF复合盐,制备的高温复合相变储热材料性能较好。研究了熔盐含量对熔盐/尖晶石基高温复合相变储热材料性能的影响,通过DSC分析测定了材料的相变潜热,激光脉冲法测定了导热系数,并研究了材料在升温过程中的抗折强度。结果表明,熔盐含量为40%时,所制备的储热材料的相变潜热为70.98kJ/kg,蓄热密度为240kJ/kg(ΔT=100℃),储热性能较好;随着熔盐含量的增加,导热系数下降;材料的抗折强度随着测试温度的升高而变化,在600℃时出现最大值。改变复合熔盐的配比可以制备出适合不同使用温度的熔盐/尖晶石基高温复合相变储热材料,KF含量的增大,材料的耐压强度和抗折强度下降,导热系数减小。研究了熔盐浸出后陶瓷基体的性能,并对材料的封装进行了初步研究。结果表明,熔盐浸出后陶瓷基体具有一定的强度,其耐压强度随着材料制备过程中熔盐加入量的变化而变化;材料经过封装后减少了在循环使用中熔盐的蒸发流失。研究了添加石墨对熔盐/尖晶石基高温复合相变储热材料性能的影响,使用ANSYS对材料的放热过程进行了模拟。结果表明,添加石墨显著提高了材料的导热系数,但石墨含量增多不利于镁铝尖晶石的形成;材料的导热系数决定了材料的放热过程,导热系数越大,材料内部热量传递越快,温度差别越小,石墨添加量为10%的试样在600s时达到相变温度,而未加石墨的材料在1000s时才能达到该温度。更多还原

【Abstract】 The properties and the current research status of phase change heat storage materials are introduced. Moreover, the preparation and properties of high-temperature composite phase change heat storage materials are also discussed. The factors of molten salt/spinel high-temperature composite phase change heat storage materials by in-situ sintering process are discussed. The influences of molten salt content, mixture ratio of molten salt and different additive graphite on the performance of molten salt/spinel high-temperature composite phase change heat storage materials are studied.Molten salt/MgAl2O4 spinel high-temperature composite phase change heat storage materials are prepared by in-situ sintering process, which is based on spinle ceramic substrate raw materials of magnesia and corundum powder, and molten salt as reaction medium. The influences of sintering temperature, different magnesia/alumina proportion and kinds of molten salt on the performance of molten salt/spinel phase change heat storage material are investigated. The materials are characterized by XRD and SEM. The result show that, the preparative materials show the better performance using KCl-KF complex salt as phase change materials at theoretical ratio when the appropriate sintering temperature is 1000℃.The influences of molten salt content on the performance of molten salt/spinel high-temperature composite phase change heat storage materials are studied. The materials’latent heat is measured by DSC thermal analysis, thermal conductivity is detected by laser flash method,and the flexural strength of the materials is also studied in the heating process. The results show that prepared materials show better heat storage performance, with phase change latent heat of 70.98kJ/kg, heat-storage density of 240 kJ/kg (ΔT = 100℃) under the condition of sintering temperature 1000℃, molten salt content 40%; Thermal conductivity decrease with the molten salt content increase. The flexural strength of samples reaches the maximum at 600℃, which increas with temperature raise.Molten salt/spinel high-temperature composite phase change heat storage materials are prepared by changing the mixture ratio of molten salt, which suit for different melting temperatures. KF content increase, compressive strength and flexural strength of samples decrease, thermal conductivity decrease, respectively.The properties of ceramic substrate are studied after molten salt leaching, and the properties of the encapsulated samples are discussed initially. Results show that ceramic substrate has certain strength after molten salt leaching, and its compressive strength change with content of additive molten salt. Otherwise, evaporation loss of molten salt reduces during cycle using process after coating. The effects of additive graphite on the molten salt/spinel high-temperature composite phase change heat storage materials are studied. The exothermic processes of samples are simulated by input experimental data using ANSYS. The results showed that thermal conductivity of samples is effectively improved by adding graphite, but the increase of graphite content is not helpful for the formation of spinel. Thermal conductivity of samples dominates their exothermic process. The greater thermal conductivity, the faster samples heat transfer, and the smaller temperature difference. Materials with 10% graphite additive reached phase change temperature at 600s, while the materials with no graphite additive need 1000s reach that temperature.更多还原