Preparation And Thermal Insulation Application Of Carbon Nanotube-reinforced Aerogel Composites

In recent years,energy saving and emission reduction has been more and more widely concerned by the government and the public,building energy saving accounts for about 30%～40%in the field of energy saving,the use of good insulation building materials plays a vital role in energy-saving buildings.Aerogel material is recognized as the best thermal insulation effect and the lightest density thermal insulation material,but it cannot be well applied due to the complicated preparation method,long preparation period and fragile of three-dimensional structure.Therefore,the development of bulk aerogel materials with excellent performance has become a hot topic of research,and the addition of reinforcing phases such as fibers and nanotubes to aerogel to improve the mechanical properties of composite materials or give new properties to aerogel is also an important research direction.In this paper,we focus on the effects of carbon nanotube reinforcement on the microstructure and thermal insulation properties of organic aerogels（chitosan aerogels and phenolic resin aerogels）and inorganic aerogels（silica aerogels）.Firstly,the carboxylated carbon nanotubes were adsorbed and bonded to the three-dimensional structure of the chitosan molecule to form a composite aerogel.The microstructure and thermal insulation performance of the composite aerogel were analyzed by SEM,FTIR,BET and thermal conductivity tests.The results show that:carboxylated carbon nanotubes can evenly dispersed in chitosan solution by amidation reaction with chitosan molecules together,the addition of carbon nanotubes increases the specific surface area and the mechanical properties of composite materials,the specific surface area of 171.7 m²/g,density of 0.03 g/cm³,at the same time,when the addition ratio of carbon nanotubes as the chitosan content of 1/2,The composite aerogel has the best thermal insulation performance.Compared with pure chitosan aerogel,the thermal conductivity of the composite aerogel is reduced to0.0375W·（m·K）^-1.The phenolic resin composite aerogel was prepared by freeze-drying using carbon nanotubes as the reinforcing phase,and the microstructure and pore structure of the phenolic resin-based composite aerogel were analyzed by SEM,FTIR and BET characterization.The results show that phenolic resin can be used as a“binder”to connect the dispersed carbon nanotubes network into a whole.However,due to the hard and brittle nature of phenolic resin,the volume of the composite aerogel shrinks severely after freeze-drying,and the specific surface area is only 70 m²/g.The carbon/silica composite aerogel was prepared by using chitosan as a three-dimensional soft template for the attachment of carbon nanotubes and silica aerogel.The characterization analysis using SEM,XRD,FTIR and BET obtained that the addition of silica aerogel significantly reduced the thermal conductivity of the composite,and the lowest thermal conductivity of the composite aerogel was 0.0312W·（m·K）^-1,while the pyrolysis rate of the composite was reduced due to the excellent thermal stability of silica,and the final residual mass was increased to 42.6%.