快速制备纳米SiO2粉末基隔热复合材料的研究进展及展望

Research Progress and Prospect on Rapid Preparation of Nano-silica Powder-based Thermal Insulation Composites

纳米气凝胶隔热复合材料是一种隔热性能优异的纳米复合材料,广泛应用于航空宇航、石油化工、建筑保温隔热领域,但是较高的成本和复杂的超临界或常压干燥技术限制了其在隔热领域的应用。纳米SiO2粉末基复合材料采用纳米SiO2粉末为基体,陶瓷纤维作增强材料,加入粘接剂、表面活性剂等添加剂,通过干法或者湿法成型实现快速制备,制备过程不需要复杂的干燥技术,相比纳米气凝胶隔热材料具有更低的成本,是一种极具发展潜力的纳米隔热复合材料。然而,由于纳米SiO2粉末基复合材料采用纳米SiO2粉末为基体,导致材料力学性能明显低于纳米气凝胶隔热复合材料;添加增强纤维和粘接剂可以提高材料的力学性能,但是其隔热性能明显下降。因此,近年来研究者们主要从优化制备工艺方面不断尝试,在充分发挥纳米SiO2粉末基复合材料低热导率优势的同时提高其力学性能。目前,纳米SiO2粉末基隔热复合材料的快速制备方法主要包括干法成型工艺和湿法成型工艺两类。其中,干法模压成型工艺应用较早,工艺成熟,制备的SiO2粉末基隔热复合材料具有较低的热导率,但成型压力较大,生产复杂形状产品的难度较大。湿法成型工艺主要有模压成型和浇筑成型两种方法,湿法模压成型相比干法模压成型具有更好的分散效果,但增加了工艺的复杂性;浇筑成型工艺简单,可成型复杂异性产品,为纳米SiO2粉末基隔热复合材料的快速制备提供了更多选择。本文综述了纳米SiO2粉末基隔热复合材料的快速制备方法及其研究进展,分别对干法成型工艺和湿法成型工艺进行介绍,分析了纳米SiO2粉末基复合材料面临的问题,对其未来发展趋势进行了展望,以期为快速制备高性能、低成本的新型纳米SiO2粉末基隔热复合材料提供参考。

Aerogel composites have been widely used in aerospace,petrochemical,construction and other thermal insulation fields due to their excellent thermal insulation properties.However,high manufacturing cost and complicated preparation process restrict the commercial exploitations of aerogel composites.Using nano-silica powder,ceramic fiber and other additives as raw materials,dry forming process or wet forming process can be used to realize the rapid preparation of nano-silica powder-based thermal insulation composites.Compared with aerogel thermal insulation composites,the preparation process of nano-silica powder-based thermal insulation composites does not require complicated supercritical drying technology,and is a kind of thermal insulation material with great development potential.However,since the nano-silica powder-based thermal insulation composites are based on fumed silica,its mechanical properties are significantly lower than aerogel thermal insulation composites.The addition of reinforcing fibers and binders can improve the mechanical properties of nano-silica powder-based thermal insulation composites,but their thermal insulation properties are significantly reduced.In recent years,researchers have been trying to optimize the preparation process,and have gave full play to the advantages of low thermal conductivity of nano-silica powder-based thermal insulation composites while improving their mechanical properties.At present,the rapid preparation methods of nano-silica powder-based thermal insulation composites,which mainly study more,mainly include dry forming process and wet forming process.Among them,the dry compression molding is applied earlier and the process is mature.The prepared nano-silica powder-based thermal insulation composites has lower thermal conductivity,but the molding pressure is larger,and it is more difficult to produce complex shape products.The wet forming process mainly has two methods of compression molding and casting molding.The wet compression molding has better dispersion effect than the dry compression molding,but the complexity of the process is increased;the casting molding is convenient and can be used for irregular shapes.It provides more options for the rapid preparation of nano-silica powder-based thermal insulation composites.In this paper,the rapid preparation method and research progress of nano-silica powder-based thermal insulation composites are reviewed,and the dry forming process and the wet forming process are introduced respectively.The problems faced by nano-silica powder-based thermal insulation composites are analyzed,and the future development trend is prospected.It provides a reference for the rapid preparation of high perfor-mance,low cost new nano-silica powder-based thermal insulation composites.