Su Lei, Wang Hongjie, Jia Shuhai, Dai Sheng, Niu Min, Ren Junqiang, Lu Xuefeng, Cai Zhixin, Lu De, Li Mingzhu, Xu Liang, Guo Sheng-Wu, Zhuang Lei, Peng Kang
State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
ACS Nano. 2021 Nov 23;15(11):18354-18362. doi: 10.1021/acsnano.1c07755. Epub 2021 Nov 12.
Ceramic aerogels are attractive candidates for high-temperature thermal insulation, catalysis support, and ultrafiltration materials, but their practical applications are usually limited by brittleness. Recently, reversible compressibility has been realized in flexible nanostructures-based ceramic aerogels. However, these modified aerogels still show fast and brittle fracture under tension. Herein, we demonstrate achieving reversible stretch and crack insensitivity in a highly compressible ceramic aerogel through engineering its microstructure by using curly SiC-SiO bicrystal nanowire as the building blocks. The aerogel exhibits large-strain reversible stretch (20%) and good resistance to high-speed tensile fatigue test. Even for a prenotched sample, a reversible stretch at 10% strain is achieved, indicating good crack resistance. The aerogel also displays reversible compressibility up to 80% strain, ultralow thermal conductivity of 28.4 mW m K, and excellent thermal stability even at temperatures as high as 1200 °C in butane blow torch or as low as -196 °C in liquid nitrogen. Our findings show that the attractive tensile properties arise from the deformation, interaction, and reorientation of the curly nanowires which could reduce stress concentration and suppress crack initiation and growth during tension. This study not only expands the applicability of ceramic aerogels to conditions involving complex dynamic stress under extreme temperature conditions but also benefits the design of other highly stretchable and crack-resistant porous ceramic materials for various applications.
陶瓷气凝胶是高温隔热、催化载体和超滤材料的理想候选者，但其实际应用通常受到脆性的限制。最近，基于柔性纳米结构的陶瓷气凝胶实现了可逆压缩性。然而，这些改性气凝胶在拉伸时仍表现出快速而脆性的断裂。在此，我们展示了通过使用卷曲的SiC-SiO双晶纳米线作为构建单元来设计其微观结构，从而在一种高度可压缩的陶瓷气凝胶中实现可逆拉伸和抗裂纹性能。该气凝胶表现出大应变可逆拉伸（20%）以及对高速拉伸疲劳试验的良好抗性。即使对于一个预制切口的样品，也能实现10%应变的可逆拉伸，表明其具有良好的抗裂纹性能。该气凝胶还显示出高达80%应变的可逆压缩性、28.4 mW m K的超低热导率，以及即使在丁烷喷枪高达1200°C或液氮低至 -196°C的温度下仍具有优异的热稳定性。我们的研究结果表明，其吸引人的拉伸性能源于卷曲纳米线的变形、相互作用和重新取向，这可以降低应力集中并抑制拉伸过程中的裂纹萌生和扩展。这项研究不仅将陶瓷气凝胶的适用性扩展到涉及极端温度条件下复杂动态应力的情况，而且有利于设计用于各种应用的其他高拉伸性和抗裂纹的多孔陶瓷材料。
