Chinese researchers have developed super-elastic hard carbon nanofiber aerogels
Inspired by the flexibility and rigidity of natural spider webs, a research team led by professor yu shuhong of the university of science and technology of China has developed a simple and general method for making super-elastic and fatigue resistant hard carbon aerogels from nanofibers.The network structure was constructed by using resorcine-formaldehyde resin as a hard carbon source.
In recent decades, carbon aerogels have been extensively studied using graphite carbon and soft carbon, showing the advantages of super elasticity.These elastic aerogels usually have fine microstructure, good fatigue resistance but ultra-low strength.Hard carbon shows great advantages in mechanical strength and structural stability due to the chaotic "card structure" structure caused by sp3c.However, stiffness and brittleness clearly prevent the use of hard carbon to achieve hyperelasticity.Making super-elastic hard carbon-based aerogels remains a challenge.
Polymerization of resin monomers is initiated in the presence of nanofibers as structural templates to prepare hydrogels with nanofiber networks, which are then dried and pyrolyzed to obtain hard carbon aerogels.During polymerization, monomers are deposited on the template and fibre-fibre joints are welded, leaving a random network structure with a large number of robust joints.In addition, physical properties (such as nanofiber diameter, aerogel density, and mechanical properties) can be controlled by simply adjusting the amount of template and material.
Due to the hard carbon nanofibers in the nanofibers and the abundant welded joints, the hard carbon aerogels show strong and stable mechanical properties, including super elasticity, high strength, extremely fast recovery rate (860 mm s-1) and low energy loss coefficient (<0.16).After 104 cycles of testing under 50% strain, the carbon aerogel showed only 2% plastic deformation and retained 93% of the original stress.
Hard carbon aerogels can be super-elastic under harsh conditions, such as in liquid nitrogen.Based on its fascinating mechanical properties, this hard carbon aerogel has potential applications for stress sensors with high stability and a wide detection range (50 KPa), as well as strethable or flexible conductors.This method is expected to be extended to manufacture other non-carbon-based composite nanofibers and provides a promising way to convert rigid materials into elastic or flexible materials by designing nanofiber microstructures.
