耐高温氧化铝气凝胶隔热复合材料研究进展

Research Progress on Alumina Aerogel Composites for High-temperature Thermal Insulation

氧化铝气凝胶是一种高孔隙率、低密度、高比表面积、耐高温和低热导的纳米多孔材料,在高温隔热领域(如航天飞行器热防护系统、工业窑炉保温材料等)具有广阔的应用前景。但是,纯氧化铝气凝胶因耐温性(1000℃以上)、力学性能和高温隔热性能相对较差难以直接应用,需要引入增强相和遮光组分制备成气凝胶复合材料以进行改善。本文对耐高温氧化铝气凝胶的制备、氧化铝气凝胶隔热复合材料的制备及性能等方面的最新研究进展进行了综述。研究人员通过原位掺杂改性、沉积改性、有机链和炭涂层改性等方法提高了氧化铝气凝胶的热稳定性。在氧化铝气凝胶中引入晶须、颗粒、多孔骨架和纤维等增强相,能够大幅提高其力学性能;纤维和遮光剂的协同作用,能够提高氧化铝气凝胶抑制红外辐射的能力,显著降低高温热导率。本文还提出了后续的研究方向:对氧化铝气凝胶的密度、微观结构进行精细调控,再引入合适的异质元素和遮光剂,以进一步提高气凝胶的热稳定性和复合材料的隔热性能;深入研究复合材料在高温下结构和性能的演化,以及氧化铝气凝胶和增强相之间的相互作用。作为一种新型的隔热材料,氧化铝气凝胶复合材料将在高温隔热领域发挥其优势并逐步实现广泛应用。

As a nano-porous material with high porosity,low density,high specific surface area,excellent heat-resistance,and low thermal conductivity,the alumina aerogel shows broad application prospect in high-temperature thermal insulating areas such as the thermal protective system for space vehicles and the thermal insulation for industrial kilns.However,pristine alumina aerogels cannot be directly used because of their relatively poor thermal resistance above 1000℃,mechanical strengths and high-temperature thermal insulating performance.They need to be improved by introducing reinforcements and opacifiers(namely the alumina aerogel composite).This paper summarizes the latest research progress of synthesis of heat-resistant alumina aerogels,and preparation and properties of alumina aerogel composites.Researchers improved the thermal stability of alumina aerogels by modifications such as in-situ doping,deposition,organic chains or carbon coatings.The introduction of whiskers,particles,porous skeletons or fibers into alumina aerogels contributes to considerable improvement of mechanical performance.The cooperation of fibers and opacifiers helps to increase the inhibition of infrared radiation and lower the high-temperature thermal conductivity of alumina aerogels.The future of alumina aerogel composites is also proposed:a)finely tailoring the bulk density,micro structures,and introducing proper foreign elements and opacifiers,are supposed to further optimize the thermal stability of alumina aerogels and thermal insulating performance of their composites;b)deeper attention should also be paid on the evolution of structure and properties of composites at elevated temperatures,and on the interaction between alumina aerogel and reinforcement.As a novel thermal insulation,alumina aerogel composites are expected to take their advantages and be widely applied in the future.