Study On The Application Of Green And Sustainable Carbon Aerogels In The Field Of Flexible Electronics

Sustainable structural materials with light-weight,superior thermal dimensional stability and strong mechanical properties are extremely important in engineering applications,however,the inherent contradiction between material performance makes it challenging to achieve these performance targets simultaneously over a wide range of use.Ultralight carbonaceous aerogels have been extremely widely studied in electronics,biomedical,environmental and energy applications due to their low density,good electrical conductivity,large surface area,high porosity and chemical inertness.Currently,the application of carbon aerogel in the field of flexible electronics is mainly constrained by the following factors:(1)Complex preparation process,high cost and difficulty in scale-up production.(2)Long production cycle.(3)High hysteresis rate and sharp decline in mechanical properties after long time testing.(4)Reduced stability under long-term operation.To address the above problems,the thesis focuses on the following research routes:firstly,to optimize the preparation process of traditional carbon aerogel,so that the preparation path is green and sustainable and the cost is significantly reduced.secondly,to select biomass materials and their derivatives from a wide range of sources as the basic raw materials for the preparation of carbon aerogels,and the whole process only uses water as the solvent.The key problems that restrict the scale-up production and practical application of carbon aerogel will be solved,and its applications in flexible electronics such as pressure sensing,supercapacitors and triboelectric nanogenerators(TENG)have been substantively explored finally.Details of the research are as follows:1.PVDF/PU/MWCNTs(PPMs)hierarchical framework structure aerogel is prepared by thermal-assembly method,and a pressure and strain sensing platform is built.The optimized PPMs aerogel pressure sensing platform achieves a sensitivity of 62.4 kPa-1 with a response time of 35 ms,and can detect weak static pressure of 3 Pa.It also enables the monitoring of human activities,medical health,human-computer interaction and some non-contact behaviors.2.A strategy for the in situ preparation of flexible MXene/biomass/chitosan aerogel(MBC)pseudo-capacitive electrode by hydrothermal methods is designed by electro-static self-assembly between the positively charged radish flakes infiltrated with salt solution and the negatively charged MXene nanosheets,and by driving according to the principle of concentration difference infiltration(CDA)between MXene nanosheets and radish cells.Under both driving forces,the MXene nanosheets are embedded inside the radish cells.The MBC pseudocapacitive electrode doping 6%(MBC-6)by lyophilization annealing exhibits a volumetric specific capacitance of 1801.4 mF/cm~3 at a scan rate of 2 mV/s.In addition,the assembled binder-free asymmetrical supercapacitor shows an ultra-high volume energy density of 33.4 Wh/L,a capacitance retention rate of 82%and a long cycle life of 50000 times at a high current density of 10 mA/cm~3.3.Water chestnut-based carbon aerogel(WCA)is prepared directly in situ by a simple one-step hydrothermal method.WCA shows excellent electrochemical performance as a binder less double electric layer(EDL)electrode.Using 3 M KOH as the electrolyte,the area specific capacitance of WCA is 343.4 F/g at 0.5 A/g.It also demonstrates ultra-high capacitance retention,which was close to 100%after 20000 cycles and still exceeds 98.3%after 40000 cycles.In addition,the green and sustainable WCA presents an ultra-high sensitivity(42.8 kPa’1)and recoverable performance,which also has potential applications in flexible pressure sensors.4.Based on a novel bacterial cellulose composite hydrogel(BCP),a superelastic carbon aerogel CBCP with infinite macroscopic scale is obtained by a simple wet-compress assembly strategy.That is,the BCP is assembled together in an orderly manner by splicing and compression molding to form a strong combined assembly"wall" after freeze-drying for scale-up production.The CBCP-based TENG energy harvester is characterized by high voltage output(>40 V)and high friction durability,and can be applied to varieties of energy harvesting and self-powered sensing systems.5.A novel pressure sensor based on hypromellose composite carbon aerogel(C-HCC)is constructed and used in a wearable human-machine interface.The multistage layered structure of the C-HCC enables the pressure sensor to have high sensitivity(15.78 kPa-1)and an ultra-wide detection range(10 Pa-900 kPa),and also exhibits high stability to compression and bending deformation.Thanks to its excellent sensing characteristics,the human-machine interface of the C-HCC-based array pressure sensor and signal processing system can effectively control the brightness of the LED array and effectively capture finger movements to control the movement of the UAV in multiple directions.