A method of carbon bonding of nanofibers was proposed, and ultra-light rGO/CNF carbon aerogels was prepared by bubble template method.
Introduction to achievements
Ultra-light, high compression and super-elastic carbon materials have great application prospects in wearable and flexible electronics devices, but due to the brittleness of carbon materials, its preparation is still a challenge. Professor Liu Chuanfu from South China University of Technology published a paper entitled "Mechanical properties of reduced graphene oxide aerogels reinforced with cellulose nanofibers" in CHEMNANOMAT magazine. Carbon aerogels with ultra-low density and high mechanical properties was successfully prepared by enhancing graphene oxide (GO) liquid crystal stabilized bubble cellulose nanofibers (CNF).
After CNF was introduced into reduced graphene oxide (rGO) nanosheets, the interaction between rGO nanosheets was enhanced by welding effect, which limited the slippage of rGO nanosheets and the peeling between microspheres, thus significantly improving the mechanical properties of the materials. The prepared carbon aerogels has super high compressibility (up to 99% strain) and elasticity (stress retention rate of 90. 1% and high retention rate of 99.0% after 50% strain 10000 cycles). The carbon aerogels prepared by various methods are superior to the existing bubble template carbon aerogels and many other carbon materials. This structural feature leads to fast and stable current response and high sensitivity to external strain and pressure, which enables carbon aerogels to detect very small pressure and various human movements from finger bending to pulse. These advantages make carbon aerogels have a broad application prospect in flexible electronics devices.
Graphic reading guide
Figure 1. Schematic diagram of preparation of rGO/CNF carbon aerogels (A) and schematic diagram of interaction between CNFs and between CNF and GO (B). POM image of GO/CNF bubble emulsion without (c) and (d) cross polarizers. SEM image of CAG (e). Photo of ultra-light CAG standing on petals (F).
Figure 2. AFM images and corresponding height images of GO (a) and CNF (b). SEM images of GO(c and d) and GO/CNF(e and f) show the distribution of CNF in folded GO nanosheets. TEM images of rGO (g) and rGO/C-CNF (h) reveal the uniform distribution of C-CNF in rGO nanosheets.
Figure 3. Macroscopic visualization shows the superelasticity of rGO/CNF carbon aerogels (A). Density of carbon aerogels with different CNF content (b). Stress-strain curves of AG and CAG-X at 50% strain (C). Stress retention and height retention (D) of AG and CAG-X after 1000 compression cycles at 50% strain. SEM images of ag, CAG-5, CAG- 10, CAG-20, CAG-30 and CAG-50 (e).
Fig. 4 is a schematic diagram illustrating the compressibility and elastic mechanism of AG (a) and CAG (b). CNF carbon nanofibers weld rGO nanosheets together, which limits the sliding of rGO nanosheets, thus improving the mechanical strength and fatigue resistance. Finite element simulation of rGO/CNF nanosheets (C).
Figure 5. CAG-20 has excellent compressibility, elasticity and fatigue resistance. Stress-strain curves of CAG-20 under different compressive strains (A). Stress-strain curves of 1, 1000, 10000 and 20000 cycles at 50% strain (b). Stress-strain curve (c) when the ultimate strain is 99%. Stress-strain curve of 200 cycles at 90% strain (D). SEM image of CAG-20 before compression (e). SEM image of CAG-20 after 20,000 compression cycles at 50% strain (F). Comparison of stress/density index (G), stress retention rate (H) and height retention rate (I) of various carbon materials.
Figure 6. The strain/stress-current response of CAG-20 and the current intensity (A) when the sensitivity strain is 10% to 70%. At 50% strain and constant voltage of 1 V, the current output is 1000 cycles (b). Linear sensitivity at 0- 100 Pa (sensitivity at insertion: 0. 1-7 kPa) (c). Assemble sensor (d) according to CAG-20. Current signals from soft pressing (e), finger bending (f), elbow bending (g) and facial expression (h). Pulse signal detection (1).
summary
To sum up, rGO/CNF carbon aerogels with low density, high mechanical properties and sensing properties were prepared by GO liquid crystal bubble template method. Carbonized CNF plays an important role in improving the mechanical strength and structural stability of carbon aerogels by enhancing the interaction between rGO nanosheets. Carbon aerogels has high compressibility, elasticity and fatigue resistance. High mechanical properties and stable microstructure endow carbon aerogels with fast and stable current response and high sensitivity. Therefore, it has great application potential in wearable devices for detecting biological signals.
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