Ultralight and resilient porous nanostructures have been fabricated in various material forms, including carbon, polymers, and metals. However, the development of ultralight and high-temperature resilient structures still remains extremely challenging. Ceramics exhibit good mechanical and chemical stability at high temperatures, but their brittleness and sensitivity to flaws significantly complicate the fabrication of resilient porous ceramic nanostructures.
We report the manufacturing of large-scale, lightweight, high-temperature resilient, three-dimensional sponges based on a variety of oxide ceramic (for example, TiO2, ZrO2, yttria-stabilized ZrO2, andBaTiO3) nanofibers through an efficient solution blow-spinning process. The ceramic sponges consist of numerous tangled ceramic nanofibers, with densities varying from 8 to 40 mg/cm3. In situ uniaxial compression in a scanning electron microscope showed that the TiO2 nanofiber sponge exhibits high energy absorption (for example, dissipation of up to 29.6mJ/cm3 in energy density at 50% strain) and recovers rapidly after compression in excess of 20% strain at both room temperature and 400°C. The sponge exhibits excellent resilience with residual strains of only ~1%at 800°C after 10 cycles of 10%compression strain and maintains good recoverability after compression at ~1300°C. We show that ceramic nanofiber sponges can serve multiple functions, such as elasticity-dependent electrical resistance, photocatalytic activity, and thermal insulation.
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Atomistic simulations of superplasticity and amorphization of nanocrystalline anatase TiO2
As an important type of functional material, nanocrystalline TiO2 with anatase phase has been used for solar energy conversion and photocatalysis. However, there have been only a few limited studies on the mechanical behaviors of nanocrystalline anatase. We performed a series of large-scale atomistic simulations to investigate the deformation of nanocrystalline anatase with mean grain sizes varying from 2 nm to 6 nm and amorphous TiO2 under uniaxial tension and compression at room temperature. The simulation results showed that for uniaxial tension, the fracture strains of simulated samples increase as the mean grain size decreases, and a superplastic deformation occurred in the nanocrystalline sample with a grain size of 2 nm. Such superplasticity of nanocrystalline anatase is attributed to the dominance of grain boundary sliding and nanoscale cavitation during deformation. The simulation results also showed that during uniaxial compression, the amorphization induced by high local compressive stress is the controlling plastic deformation mechanism, resulting in a good compressibility of nanocrystalline TiO2. During both tension and compression, nanocrystalline TiO2 exhibited good deformability, which is attributed to the fact that the grain boundaries with high volume fractions and disordered structures accommodated large plastic strains. Our present study provides a fundamental understanding of the plastic deformation of nanocrystalline anatase TiO2, as well as a route for enhancing the tensile and compressive deformability of nanostructured ceramics.
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- Award ID(s):
- 1709318
- NSF-PAR ID:
- 10094788
- Date Published:
- Journal Name:
- Extreme mechanics letters
- Volume:
- 22
- ISSN:
- 2352-4316
- Page Range / eLocation ID:
- 131-137
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/DOI:10.1016/j.eml.2018.05.009
