Preparation And Performances Of Cellulose/Graphene Oxide Carbon Aerogels

Ultralight and resilient carbon aerogels with high compressibility and fatigue resistance are of great interest in various applications,such as wearable pressure-sensing electronics,flexible energy storage systems,and electromagnetic shielding.However,owing to irrational structural design and uncontrollable carbonization process,fabricating carbon aerogels with both high mechanical performances and linear sensitivity from green and sustainable biomass remains a great challenge.Herein,by engineering an ordered lamellar texture and stabilizing the structure during carbonization,ultralight carbon aerogels with superior mechanical performances and high linear sensitivity were successfully fabricated from water-soluble cellulose ethers?sodium carboxymethyl cellulose and hydroxypropyl methyl cellulose?.The excellent mechanical properties,electrical properties,and the ability to accurately capture tiny changes in biological signals ensure the carbon aerogels with broad application prospects in the field of wearable electronic devices.The main research contents are summarized as follow:?1?With a modified Hummers method,graphene oxide?GO?with good sheet-peeling effect was successfully prepared,and transmission electron microscopy?TEM?,Infrared spectroscopy?FTIR?,Raman spectroscopy?Raman?,and X-ray diffraction?XRD?were used for characterization and analysis of GO.CMC/r GO composite carbon aerogels were prepared by directional freezing casting using sodium carboxymethyl cellulose?CMC?as raw material.It was found that pristine CMC aerogels showed a selectively high carbon yield?32.3%?,however,the carbonized CMC aerogels exhibited poor mechanical properties due to the large and irregular microstructure.Owing to the lamellar inducing effect of GO,CMC/r GO aerogels showed parallel and continues lamellar structure and excellent elasticity.Proper solid content and mass ratio of CMC to GO were important to the fabrication of ordered structure in carbon aerogels and among all the samples,C-CMC/r GO-4 with a solid content of 1.4 wt%exhibited ordered microstructure and excellent mechanical properties.The stress retention rate is 93.6%?50%of compression strain,after 1000 cycles?.It can withstand high compression strain of 80%,and the stress retention rate is 90.4%,height retention rate is 91.3%after 100cycles at 80%strain.C-CMC/r GO-4 can identify a wide range of compression strain?10%-80%?and exhibit good current stability in 1000 cycles of 50%strain.The linear sensitivity is 7.3 k Pa^-1 in the pressure range of 0-10 k Pa?approximately equivalent to 50%of the compression strain?.The wearable sensor based on C-CMC/r GO-4 can accurately capture human biological signals including facial expressions,fingers,elbows,and wrist bending.?2?Ultra-light and flexible carbon aerogel C-HPMC/r GO-6 was prepared using hydroxypropyl methyl cellulose?HPMC?as carbon source,GO as lamellar structure-oriented material with a combination of directional freeze-drying and pre-oxidation methods.The parallel and continuous lamellar structure was attributed to directional freezing and pre-oxidation treatment,and the structure was well preserved after carbonization.The pre-oxidation treatment is of significant importance to the heat stability and microstructure stability of the aerogels.C-HPMC/r GO-6 exhibits excellent mechanical properties,the stress retention was high up to 96.33%after 1000 compression cycles at 50%strain.Moreover,the aerogel shows an extremely high compression strain of 99%,and there is no geometry deformation after 300 compression cycles at 99%strain.C-HPMC/r GO-6 also shows excellent electrical properties,regular and different current signals were record when subjected to 10%-90%of compression strain.Meanwhile,the aerogel can identify a wide range of compressive strain,exhibiting excellent current stability in 1000 cycles of 50%strain.The linear sensitivity of C-HPMC/r GO-6 was up to 15.8 k Pa^-1 in a wide pressure range?0-18k Pa?and the wearable sensor based on C-HPMC/r GO-6 was able to accurately capture human biological signals.