Study Of Graphene Aerogel Flexibility And Sensing Properties

Graphene,composed of carbon atoms with sp~2 hybridization orbitals,is a unique two-dimensional carbon nanomaterial.Graphene aerogel with macroscopic three-dimensional structure formed by inter-lap between two-dimensional graphene sheets is one of the current research hotspots in the field of graphene.Due to the properties of graphene aerogel such as super compressibility,high electrical conductivity,large specific surface area,ultra-high porosity,lipophilic and fireproof,graphene aerogel has broad application prospects in supercapacitors,environmental remediation,high-performance sensors and other fields.However,due to the sparse and fragile connections within graphene aerogels,they tend to exhibit extremely low strength when subjected to tensile,bending,and torsional stresses,are almost non-deformable,and exhibit brittleness.In order to improve the mechanical properties of graphene aerogel,this paper innovatively proposes a method to enhance graphene aerogel using sandwich structure and successfully prepared sandwich aerogel using multi-walled carbon nanotube film as panel material,graphene aerogel as core material,and graphene oxide ethanol solution as binder.Graphene oxide aqueous solutions were prepared by a modified Hummers method and graphene oxide ethanol solutions were obtained by replacing the solvent.High-quality graphene aerogels were prepared by hydrothermal reduction and freeze-drying methods using graphene oxide aqueous solution as precursors.The multi-walled carbon nanotube sponge was prepared by floating catalytic method using o-dichlorobenzene as the carbon source and ferrocene as the catalyst,and the multi-walled carbon nanotube film was obtained by densification through capillary force.The morphology and chemical composition of the above prepared materials were also verified by a series of characterization.The mechanical properties of sandwich aerogel were investigated by Instron,and it was found that the sandwich structure composite reinforcement method effectively improved the mechanical properties of graphene aerogel.The maximum compression rate of sandwich aerogel reaches 99%,and the ultimate compressive stress reaches up to 3.35 MPa,which is 2.43 times higher than that of the same density graphene aerogel;the ultimate tensile strength of sandwich aerogel is 312 k Pa,which is 3000% of that of the same density graphene aerogel,and the ultimate tensile strain is increased to 2.2%;the aerogel can withstand bending and torsional deformation,which prevents the occurrence of brittle damage during the deformation and can store strain energy during the deformation process and spring back to the original state after the removal of external force.Revealing the source of the strong adhesive force of graphene oxide and the mechanism of surface confinement to enhance the flexibility and toughening,demonstrating the successful flexibility of graphene aerogel.Expanding the application of graphene aerogel in stress-strain sensors,thermal insulation and flame retardant materials,dampers,etc.An innovative piezoresistive sandwich aerogel flexible sensor was proposed and tested the sensing performance of flexible sensor.It is found that the device exhibits a fully recoverable resistive response under huge compression deformation,and the relative resistance varies linearly with the compression strain,with almost no sensing hysteresis and sensitivity up to 0.76;the sensor can stably sense 500 Pa microstress,and the minimum recognizable strain is 50 μm;the sensor also exhibits stable sensing during bending strain,with a linear change in relative resistance with bending angle similar to that of compression,and exhibits a high sensitivity of 0.208/°.The piezoresistive mechanism of graphene aerogel was revealed and the corresponding equations were derived.Based on the environmental stability of the carbon material,the sensing performance of flexible sensor was measured under liquid nitrogen and400℃.The relationship of relative resistance with compressive strain at high temperatures was found to be linear in consistency with room temperature,and slightly different at low temperatures,but both ensure continuous and stable sensing.The feasibility of the sensor for use in extreme ambient temperatures was verified,expanding the selection of sensor for extreme environmental detection in deep space,deep earth,and deep sea.