As a three-dimensional nanoporous material with low density and high porosity, silica aerogel exhibits a low thermal conductivity at room temperature and becomes an ideal nanoporous super thermal insulating material. However, the poor mechanic property and fragment occurred during ambient pressure drying have greatly limited the practical applications of silica aerogel. The apparent enhancements in integrity, strength and flexibility are achieved with the new-type of silica aerogels prepared by compositing or crosslinking, which makes it possible to be applied alone in the form of monolith as thermal insulating materials. In this paper, the porous structures, basic properties and thermal insulation principles of silica aerogels are briefly introduced. The research progress of newly developed fiber reinforced composite silica aerogels, polymer crosslinked silica aerogels, and the other combined silica aerogels as monolithic thermal insulation materials are focused. Finally, the key problems in the field of silica aerogels are summarized and the future research trends are highlighted.

Contents
1 Introduction
2 Basic properties of silica aerogels
3 Principles of thermal insulation of silica aerogel
4 Silica aerogels as thermal insulating materials
5 New-type silica aerogels as thermal insulating materials
5.1 Fiber reinforced composite silica aerogels
5.2 Polymer crosslinked silica aerogels
5.3 Combined silica aerogels
6 Conclusion and outlook