关键词: 梯度密度, 气凝胶, 空间探索, 功能材料, 合成, 应用

Abstract: Aerogel is a kind of key functional material for space exploration. In this paper, the classification, preparation methods, composite techniques, unique properties and space-exploration applications of homogenous aerogels and density-graded aerogels are systematically introduced. In particular, the composite technique of density-graded aerogels, which is regarded as a focus of international research, is classified into early method, multilayer-pasted method, layer-by-layer gelation method and gradient-sol co-gelation method. Also, the developing trends of the density-graded aerogels are summarized as the transitions from low gradient to high gradient, from graded density to gradient density, from low control accuracy to high control accuracy, and from homogeneous gradient to designed gradient, based on the previous studies of the authors. Furthermore, several functional designs on the distributions of composition and properties (density, refractive index and thermal conductivity) of the density-graded aerogels are provided, in order to meet the requirements of hyper-velocity particle capture, high-performance thermal insulation and high-resolution Cherenkov detection.

Key words: density-graded, aerogels, space exploration, functional materials, synthesis, applications