Su Lei, Wang Hongjie, Niu Min, Dai Sheng, Cai Zhixin, Yang Biguo, Huyan Huaixun, Pan Xiaoqing
State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, P. R. China.
Department of Materials Science and Engineering, University of California, Irvine, Irvine, CA 92697, USA.
Sci Adv. 2020 Jun 24;6(26):eaay6689. doi: 10.1126/sciadv.aay6689. eCollection 2020 Jun.
Ceramic aerogels are promising lightweight and high-efficient thermal insulators for applications in buildings, industry, and aerospace vehicles but are usually limited by their brittleness and structural collapse at high temperatures. In recent years, fabricating nanostructure-based ultralight materials has been proved to be an effective way to realize the resilience of ceramic aerogels. However, the randomly distributed macroscale pores in these architectures usually lead to low stiffness and reduced thermal insulation performance. Here, to overcome these obstacles, a SiC@SiO nanowire aerogel with a nanowire-assembled anisotropic and hierarchical microstructure was prepared by using directional freeze casting and subsequent heat treatment. The aerogel exhibits an ultralow thermal conductivity of ~14 mW/m·K, an exceptional high stiffness (a specific modulus of ~24.7 kN·m/kg), and excellent thermal and chemical stabilities even under heating at 1200°C by a butane blow torch, which makes it an ideal thermally superinsulating material for applications under extreme conditions.
陶瓷气凝胶是一种很有前景的轻质高效隔热材料，可应用于建筑、工业和航空航天器，但通常受限于其脆性以及在高温下的结构坍塌。近年来，制造基于纳米结构的超轻材料已被证明是实现陶瓷气凝胶韧性的有效方法。然而，这些结构中随机分布的宏观孔隙通常会导致低刚度和隔热性能下降。在此，为克服这些障碍，通过定向冷冻铸造和后续热处理制备了具有纳米线组装的各向异性和分级微观结构的SiC@SiO纳米线气凝胶。该气凝胶具有约14 mW/m·K的超低热导率、极高的刚度（比模量约为24.7 kN·m/kg），甚至在丁烷喷枪1200°C加热下仍具有出色的热稳定性和化学稳定性，这使其成为极端条件下应用的理想热超绝缘材料。
