LIU Xiaoyu ¹, SU Lifen ¹, MIAO Lei ², ZHOU Jianhua ², YANG Bin ¹, WU Bin ¹, XIA Ru ¹, CAO Ming ¹, QIAN Jiasheng ¹
(1. Anhui Province Key Laboratory of Environment-Friendly Polymer Materials, School of Chemistry and Chemical Engineering, Anhui University, Hefei 230601, Anhui, China; 2. Guangxi Key Laboratory of Information Materials, Guilin University of Electronic Science and Technology, Guilin 541004, Guangxi, China)

Abstract:  Aerogels have attracted more and more attentions in thermal insulating applications, due to their outstanding advantages, such as ultra-low density, large specific surface area and high porosity. Alumina (Al₂O₃) aerogel is a kind of porous material with three-dimensional (3D) network and low thermal conductivity. However, the Al₂O₃aerogel would undergo phase transformation, resulting in severe structural shrinkage, during cooling from high temperatures. In addition, the high transmittance of infrared radiation led to decrease in thermal insulation at high temperatures. In this work, Al₂O₃-SiO₂ nano aerogel with excellent thermal stability were prepared by using a sol-gel method through co-prepolymerization, followed by freeze-drying and high temperature treatment. Structure, morphology and infrared reflection of the composites, as a function of molar ratio of Al/Si, were characterized by using XRD, N₂ adsorption-desorption, SEM and infrared reflection measurement. It was found that the Al₂O₃-SiO₂ composites with Al/Si molar ratio of 5:1 exhibited a high specific surface area of 185 m²/g and uniform mesopore structure with pore sizes of 6-8 nm, after annealing at 950 ℃, while the infrared reflectivity was 40% in the wavelength range of 3-6 μm. Combined with SEM morphology and pore structures, the (Al₂O₃-SiO₂ composites with Al/Si molar ratio of 5:1 could be used to effectively reduce the heat loss caused by infrared radiation at high temperatures.

Key words:  thermal insulation; infrared reflection; porous