Seemingly \”fragile\” hard skills, high strength carbon airgel
Recently, led by Professor Yushu Hong of China University of Science and Technology Task Force has both inspired by nature spider web of high strength and elasticity, by clever template method, a series of hard carbon airgel nano-fiber network structure was prepared. The series superelastic airgel, fatigue resistance and good stability. Research was selected as the back cover of papers published in the \”Advanced Materials.\” airgel translucent colors and its ultra-light weight, sometimes referred to as \”solid smoke\” or \”frozen smoke.\” Airgel seemingly \”fragile\”, in fact, very durable. It can withstand thousands of times corresponding to the pressure of its own mass, not melt until the temperature reaches 1200 degrees Celsius. In addition to its low thermal conductivity and the refractive index, but also the insulating capacity of 39 times stronger than the best glass fibers. Due to possess these characteristics, airgel space exploration has become irreplaceable material, the Russian \”Peace\” space station and the United States \”Mars Pathfinder\” probe will use it for thermal insulation. Carbon material may be hybrid orbitals of carbon atoms can be divided into different graphite carbon, hard carbon and soft carbon. Soft carbon and hard carbon, a carbon material mainly describe polymers prepared by pyrolysis, the pyrolysis process, some of the carbon atoms constituting the two-dimensional heavy aromatic graphene sheet, if the graphene sheet is substantially parallel to, at a high temperature is easily graphitization, it referred to as soft carbon such carbon; if random graphene sheets are stacked and cross-linking a carbon atom by an edge, not graphitized at a high temperature, carbon which is referred to as hard carbon. In general, carbon and graphite, soft carbon having high elasticity, easily deformed, but the lower intensity; since the hard carbon microscopically presence turbostratic \”house of cards\” structure, exhibit extremely hard carbon material in mechanical strength and structural stability big advantage, but the intrinsic nature brittle and fragile. How hard carbon material is prepared as a bulk material is a superelastic The challenge. Researchers resorcinol – formaldehyde (RF) resin as a hard carbon, a variety of one-dimensional fibrous structure as a template nanofibers RF aerogels prepared by high temperature carbonization can be obtained hard carbon aerogels superelastic gum. Such hard carbon airgel fine microstructure, constituted by a large number of welding points between the nanofibers and fibers. This method is simple and efficient, easy to scale production, by adjusting the amount of the template and the resin monomer can easily regulate the diameter of nanofiber airgel density, mechanical properties. Traditional hard and brittle and hard carbon material different blocks, such a hard carbon aerogels exhibit excellent elastomeric properties,The structural stability, after 50% compression, can still recover the microstructure; rebound velocity is higher than a number of resilient material graphitic carbon group; intermolecular energy loss factor low, typically graphite and soft carbon material present in the interior of the force, will cause adhesion and frictional forces to dissipate a lot of energy; fatigue resistance, after the test 104 cycles at 50% strain, carbon airgel displays only 2% of plastic deformation, and maintain 93% of the initial stress. The researchers also explored the use of such a hard carbon airgel in terms of elastic conductor, after multiple compression cycles at 50% strain, the resistance is almost constant, exhibits stable mechanical – electrical properties, while in harsh under conditions (e.g., in liquid nitrogen) remains superelastic and resistance stability. It is based on its excellent mechanical properties, it is expected to be applied to such a hard carbon airgel having a high stability, large range, stretchable or bendable stress sensor. In addition, this method can be extended to the preparation of other non-carbon-based composite nanofiber airgel, by providing a new way to design the microstructure of the nanofibers converted into an elastic or flexible material, a rigid material for the future.