A General Strategy to Fabricate Flexible Oxide Ceramic Nanofibers with Gradient Bending-Resilience Properties

Inorganic materials assembled with rigid elements such as crystals or graphitized carbon generally show brittleness and hardness. However, it is found that both TiO2 ceramic crystal nanofibers (NFs) and carbon NFs show superior flexibility, in which the former are surprisingly knottable and the latter exhibit excellent bending-resilience property. The different flexure mechanisms are revealed by fabricating composite NFs of these two constituents and find that the carbon NFs can be recovered to the original states after releasing the external force, while the bending-resilience is weakened and the softness of the composite NFs is enhanced upon increasing the TiO2 content. The graphitized carbon can store mechanical deformation energy that enables the NFs with bending-resilience, while both the homogeneous interfaces between TiO2 crystals and the heterogeneous interfaces between TiO2 and carbon can alleviate stress concentration, which reduce the flexural modulus of the composite NFs. By filling different contents of elastic carbon into TiO2 NFs, a series of flexible NFs that exhibit gradient bending-resilience properties are fabricated. This study provides a deeper understanding of the mechanical properties of inorganic materials.