摘要
气凝胶极高的孔隙率有效降低了材料的固相热传导,孔径主要分布在介孔范围内（2~50nm）,有效抑制了气相传热,而遮光剂的引入可起到很好的反射、吸收和再散射作用,进一步降低气凝胶的辐射热传导,从而使得气凝胶材料具备极低的热导率,是一种优质的高效隔热材料。根据组分的不同,气凝胶主要可分为氧化物气凝胶、炭气凝胶和碳化物气凝胶。氧化物气凝胶材料在高温区（〉1000℃）容易发生晶型转变及颗粒的烧结,其耐温性相对较差,但是其在中高温区（〈1000℃）具备较低的热导率。炭气凝胶材料在真空或惰性氛围下耐温性最高可达3000℃,2000℃下热导率低至0.601W·m-1·K-1,密度可调,但是该材料在有氧氛围下容易发生烧蚀,这需要通过涂覆某些抗氧化性涂层来加以有效解决。碳化物气凝胶材料目前研究较为匮乏,报道最多的是碳化硅气凝胶,但是也仅限于对该材料的制备与表征,而对于其热学性能方面的研究仍然较少。主要介绍了这三大类耐高温气凝胶隔热材料的研究进展,并对其未来的发展方向进行了展望。
Heat transfer via the solid backbone is low for aerogel due to its ultrahigh porosity,and heat transfer via gaseous phase is inhibited due to its network structure consisting of mesopores（2-50nm）and nanoparticles.The incorporation of so-called infrared opacifiers decreases the radiative heat transfer through reflecting,absorption and scattering processes.Thus,aerogel possesses a quite low thermal conductivity,thus can be used as efficient thermal insulation.Aerogels can be classified into three different categories,i.e.oxide aerogels,carbon aerogels and carbide aerogels,according to their constituents.Oxide aerogels possess relatively low thermal resistance due to their phase changes and particles sintering,but they obtain rather low thermal conductivity.Carbon aerogels have controllable densities and rather high thermal resistance（3000℃）under vacuum or inert atmosphere.The thermal conductivity at2000 ℃ under argon atmosphere is only 0.601W·m-1·K-1,however carbon combustion easily happens in oxidizing atmosphere.This can be solved by coating with some oxidation resistance coatings on the surface of carbon aerogels.There are insufficient studies for carbide aerogels,which mainly concern over SiC aerogel and concentrate on their preparation methods and characterizations,while little attention is paid to their thermal properties of carbide aerogels.Herein,the advances in research of the three different kinds of aerogels are presented,followed by outlook of these high temperature resistant aerogel insulations.
出处
《材料导报》
EI
CAS
CSCD
北大核心
2015年第9期102-108,共7页
Materials Reports
基金
长江学者和创新团队发展计划(IRT1146)
江苏高校优势学科建设工程
江苏先进无机功能复合材料协同创新中心
江苏省科技支撑计划(工业)项目(BE2014128)
江苏省"333工程"培养资金资助项目(BRA2012138)
材料化学工程国家重点实验室开放课题基金(KL11-09)
宿迁市科技基础设施项目(2013-39)
