Lightweight compressible materials with super-elasticity and fatigue resistance, especially those that adapt to a wide temperature range, are ideal materials for aerospace, mechanical buffering, energy damping, and soft robots. Many low-density polymer foams are highly compressible, but they tend to fatigue when reused, and superelastic degradation occurs near the glass transition and melting temperature of the polymer. Although researchers have developed various thermally stable lightweight metal and ceramic foam materials, they usually have only minimal reversible compressibility and show fatigue under cyclic deformation. Carbon nanotubes and graphene have been used as basic materials for the preparation of lightweight superelastic materials in recent years due to their inherent superelasticity and thermomechanical stability.
Although the related literature has reported the excellent performance of such materials, but the complex equipment and preparation process involved in these work can only prepare materials of millimeter size. On the other hand, complex hierarchical biomaterials that have evolved from hundreds of millions of years in nature have received much attention because of their excellent mechanical properties. However, because they are pure organic or organic / inorganic composite structures, they are usually only suitable for very narrow temperatures. Work within limits. Therefore, converting these non-thermally stable structural biological materials into thermally stable graphite materials with inherent hierarchical structure is expected to create thermodynamically stable materials.
Recently, the team of Yu Shuhong and the team of Liang Haiwei of the University of Science and Technology of China reported a method of thermally converting structural biomaterials (BC, bacterial cellulose) into graphite carbon nanofiber aerogels (CNFAs) through pyrolysis chemical control. The carbon aerogel prepared by it perfectly inherits the hierarchical structure of bacterial cellulose from macro to micro, and has remarkable thermomechanical properties. Especially after 2 × 106 compression cycles, it can still maintain superelasticity without plastic deformation. It has excellent superelasticity and fatigue resistance that does not change with temperature in a wide temperature range of at least -100 ~ 500 ℃. This aerogel has unique advantages over polymer foams, metal foams, and ceramic foams in terms of thermomechanical stability and fatigue resistance. It achieves large-scale synthesis and has the economic advantages of biological materials. Relevant achievements were published in the journal Adv. Mater. As Temperature-Invariant Superelastic and Fatigue Resistant Carbon Nanofiber Aerogels.
The team developed a method for chemically controlling the pyrolysis of bacterial cellulose (BC) using inorganic salts, and realized a large-scale synthesis and morphology-preserving new carbonization process. The developed carbon nanofiber aerogel inherited the bacteria better The hierarchical structure of cellulose from macro to micro, shows obvious super-elasticity and anti-fatigue performance which does not change with temperature in a wide temperature range. Since carbon nanofiber aerogels have excellent thermally stable mechanical properties and can be prepared in large quantities, they will have important application prospects in many fields, especially suitable for mechanical buffering, pressure sensing, energy damping and aerospace solar energy under extreme conditions.