Cuttlebone-inspired Structures for Mechanical DampingPart of:
Ceramics typically feature excellent thermal, chemical and mechanical stability, making them widely applicable in today's technologies. However, the hard and stiff nature of ceramics makes them prone to brittle fracturing, when being exposed to mechanical shock or vibrations. Such mechanical failure then negatively affects the lifetime of the ceramics' technical applications. One well-established approach to enhance the fracture toughness of ceramics is to combine them with a soft and ductile component, which serves as shock absorber. Even though the mechanical performance is drastically improved in this way, the presence of a second component could shield the functionality of the ceramics, reducing their technical performance.
Here we report an alternative concept to generate a vibration resistant functional all-ceramic material, using V2O5 scaffolds as model system. Hydrated V2O5 nanofibers were synthesised by a well-established sol-gel method. Owing to their nanosize and high aspect ratio the synthesized V2O5 building blocks exhibit a pronounced mechanical flexibility – a property, which is unusual for ceramics. This flexibility could be transferred to the macroscopic level by their filigree assembly, using ice-templating of aqueous nanofiber solutions. Subsequent freeze drying yielded highly porous (up to 99.8 %) scaffolds, which mimic the structure of natural cuttlebone. Finally, annealing the scaffolds at 350 °C removed the residual water, but simultaneously preserves the identity of the nanofibers, thus preserved the filigree microstructure. The resulting scaffolds featured a macroscopic elastic deformation of 3 %, which is exceptional among other all-ceramic materials. Moreover, this elasticity enabled the investigation of the scaffolds’ dynamic mechanical performance. Compression- and frequency dependent damping tests revealed ultrahigh damping capacities with a loss factor tanδ of up to 0.47, which outperforms conventional polyurethane foams (tanδ ~ 0.14) by up to 300 %.
This concept could be transferred to other fiber-shaped ceramic nanomaterials, enabling to generate numerous shock and vibration resistant functional materials for various applications, including catalysis, sensing and energy storage.
1. Knöller, A., Runčevski, T., Dinnebier, R. E., Bill, J. & Burghard, Z. Cuttlebone-like V2O5 Nanofibre Scaffolds – Advances in Structuring Cellular Solids. Sci. Rep. 7, 42951 (2017).