超临界干燥技术制备气凝胶的研究进展

Research Progress of Aerogels Prepared by Supercritical Drying Technology

摘要: 气凝胶作为一种具有高孔隙率、高比表面积和超低密度的固体材料，在隔热隔音、能量存储、环境净化、生物医学等领域展现出广阔的应用前景。超临界干燥是制备高性能气凝胶的关键步骤，其通过消除气–液相界面的表面张力，能够完美保留湿凝胶的纳米多孔结构。本文系统综述了超临界干燥技术的基本原理、工艺方法、参数优化策略及其在不同类型气凝胶制备中的应用。文章首先阐述了超临界干燥的热力学基础和传质机理，随后详细介绍了高温超临界干燥和低温超临界二氧化碳干燥两种主要工艺路线，重点分析了温度、压力、流速和卸压速率等工艺参数对干燥效果的影响。在此基础上，比较了超临界干燥与冷冻干燥、常压干燥的优缺点，并探讨了该技术在二氧化硅气凝胶、有机聚合物气凝胶、生物基气凝胶及复合气凝胶制备中的适用性。最后，针对当前超临界干燥工艺成本高、效率低等挑战，提出了过程强化、连续化生产和绿色化发展的未来方向，以期为高性能气凝胶的产业化制备提供理论参考。

Abstract: As a solid material with high porosity, high specific surface area and ultra-low density, aerogels have shown broad application prospects in the fields of thermal insulation, sound insulation, energy storage, environmental purification, and biomedicine. Supercritical drying is a key step in the preparation of high-performance aerogels. By eliminating the surface tension of the gas-liquid interface, it can perfectly retain the nanoporous structure of the wet gel. This paper systematically reviews the basic principles, process methods, parameter optimization strategies of supercritical drying technology and its application in the preparation of different types of aerogels. Firstly, the thermodynamic basis and mass transfer mechanism of supercritical drying are expounded. Then, two main process routes of high temperature supercritical drying and low temperature supercritical carbon dioxide drying are introduced in detail. The effects of process parameters such as temperature, pressure, flow rate and pressure relief rate on drying effect are analyzed emphatically. On this basis, the advantages and disadvantages of supercritical drying, freeze drying and atmospheric pressure drying were compared, and the applicability of this technology in the preparation of silica aerogels, organic polymer aerogels, bio-based aerogels and composite aerogels was discussed. Finally, in view of the challenges of high cost and low efficiency of the current supercritical drying process, the future directions of process intensification, continuous production and green development are proposed, in order to provide a theoretical reference for the industrial preparation of high-performance aerogels.