Aerogels are thin materials with numerous tiny pores that have potential applications in flexible electronics, energy devices, aerospace structures, and thermal insulation. Traditional ceramic-based aerogels, however, have a tendency to be brittle, which reduces their effectiveness in load-bearing structures. Due to the limitations of their building blocks, recent classes of polymeric aerogels can only get a high mechanical strength by giving up their porosity or lightness.
A research team led by Drs. Lizhi Xu and Yuan Lin from the Department of Mechanical Engineering at the Faculty of Engineering at the University of Hong Kong (HKU) has made a new class of polymer aerogel materials that could be used in a wide range of functional devices.
In this study, aramids, or Kevlar, a polymer material used in bullet-proof vests and helmets, were used to successfully create a new type of aerogel using a self-assembled nanofiber network. The research team used a solution-processing technique to disperse the aramids into nanoscale fibrils rather than millimeter-scale Kevlar fibers. A 3D fibrillar network with high nodal connectivity and strong bonding between the nanofibers was produced by the interactions between the nanofibers and polyvinyl alcohol, another soft and “gluey” polymer. The material is extremely strong and tough, and it outperforms other aerogel materials. “It’s like a microscopic 3D truss network, and we managed to weld the trusses firmly together,” said Dr. Xu.
The team has also used theoretical simulations to further explain the outstanding mechanical performance of the created aerogels. Dr. Lin, who oversaw the theoretical simulations of the research, said: “We constructed a variety of 3D network models in computers, which captured the essential characteristics of nanofibrillar aerogels.” The overall mechanical behavior of fibrillar networks depends on nodal mechanics. “Our simulations showed that even with the same solid content, the nodal connectivity and bonding strength between the fibers had a large impact on the network’s mechanical strength,” added Dr. Lin.
“The results are very interesting.” The easy fabrication processes for these aerogels also allow them to be used in various functional devices, such as wearable electronics, thermal stealth, filtration membranes, and other systems, said Dr. Xu. “We not only developed a new type of polymer aerogel with excellent mechanical properties but also provided insights for the design of various nanofibrous materials.”
