纤维气凝胶的分类、制备工艺及应用现状

Classification,Preparation Process and Application of Fibre Aerogel:a Review

气凝胶具有高孔隙率、低密度、高比表面积和低热导率等优异性能,广泛应用于隔热、隔音和吸附等领域,已经成为21世纪以来新型纳米多孔材料的研究热点。但是由于气凝胶的网络结构导致其缺点也十分突出,首先,气凝胶的力学性能较差、脆性大,使其加工、处理变得困难,且易产生粉尘污染;其次,由于原料和制备工艺等限制,气凝胶的价格昂贵;另外往往只能静态成型难以连续生产,形态多是与模具或反应相对应的块状或粉末状,不能满足更多的应用。因此提高气凝胶的力学性能、寻找更简单廉价的合成方式和拓宽气凝胶形态等成为亟待解决的问题。设计制备纤维态气凝胶和纤维复合气凝胶是解决上述不足的方法之一。可通过湿法纺丝、管中浇铸、纤维状基材自组装、静电纺丝、纤维热解碳化、原纤化堆积等成型方法和超临界、冷冻、常压等干燥工艺,制备无机纤维气凝胶、有机纤维气凝胶、有机/无机杂化纤维气凝胶和纤维复合气凝胶材料,实现气凝胶的骨架结构的增强、纤维态气凝胶的成型和连续生产,可避免附聚并方便回收处理,还可设计调控特殊的中空结构和分级孔结构,或利用嵌入纤维的独特物理、化学特性,在保持气凝胶原有优秀性能的基础上,赋予其新的性能。本文对近五年纤维气凝胶及纤维复合气凝胶材料的研究现状进行了概览,介绍了纤维气凝胶的类型、制备方法及原理,说明了纤维气凝胶在吸附、隔热、传感、能量存储、催化和微波屏蔽等传统及新兴领域的应用,并提出了未来可尝试的研究方向,对纤维气凝胶的改进提出一些建议。

Aerogel has excellent properties such as high porosity,low density,high specific surface area and low thermal conductivity. It is widely used in the fields of heat insulation,sound insulation and adsorption,which has become a research hotspot of new nanoporous materials since the 21 st century.However,the network structure of aerogel also causes very prominent disadvantages. First of all,its poor mechanical properties and brittleness makes it difficult to process and treat,and easy to produce dust pollution. Secondly,aerogels are expensive due to restrictions on raw materials and preparation techniques. In addition,the samples of aerogels are always formed statically rather than continuously,the shape of which is general block or powder according to the mold or reaction. Therefore,developing the high mechanical properties,finding a facile and cheap synthesis methods,and broadening the morphology of aerogel remains challenging.Designing and preparing fibrous aerogels and fiber composite aerogels is one of the methods to solve the aforementioned problems. For example,the inorganic fiber aerogels,organic aerogels,organic/inorganic hybrid fibers aerogels and fiber composite aerogels can be prepared by wetspinning,in-tube casting,fiber self-assembly,electrostatic-spinning,fiber pyrolysis and carbonization,fibrous deposition and other forming methods and drying process including supercritical pressure,freezing and atmospheric drying and so on. Therefore,the required performance of aerogels such as the skeleton structure enhancement of aerogels and fibers,the formation and continuous production of aerogels can be realized,which can avoid agglomeration and facilitate to recycle. Besides,the aerogels can be endowed with new properties on the basis of maintaining excellent original properties by designing special hollow structure and hierarchical pore structure,or using the unique physical/chemical characteristics of the embedded fibers.In general,we summarize the research status of fiber aerogels and fiber composite aerogel materials in the past five years,introduces the types,characteristics,preparation methods and principles of fiber aerogels,and explains the advantages of fiber aerogels in adsorption,heat insulation,applications in traditional and emerging fields such as sensing,energy storage,catalysis and microwave shielding. Furthermore,we also point the possible research directions in future,and propose some suggestions for the improvement of fiber aerogels.