Preparation Of Aramid-based Nanofiber Aerogeland Study Of Its Carbonization Process

As one of the lightest solid materials in the world,polymer-based aerogel,has attracted widespread attention because of its excellent performance in the fields of dielectric,adsorption,thermal insulation and catalyst support.In addition,carbon aerogels prepared through carbonization of polymer-based aerogels have favorable performance as the adsorption materials.and supercapacitor electrode.In this paper,the aramid nanofiber aerogels(ANFAs)were prepared by using the aramid nanofibers formed by swelling and ultrasonication of aramid fibers.ANFA not only overcomes the disadvantage of poor toughness of inorganic aerogels,but also has ultra-low density(0.0101g/cm-3),ultra-high porosity(99.27%)and excellent thermal insulation.The nano-carbon fiber aerogel obtained after carbonization of ANFA has an ultra-high specific surface area and a nitrogen doping structure,leading to a good application prospect in the field of supercapacitor electrode materials.First of all,in this work,an acetonitrile-induced gelation experiment was designed through the mechanism.The correctness of the reaction mechanism was confirmed by comparison of different gelation reagents and the analysis of the reaction results.In order to determain the optimal condition for each step,the wet gel preparation process was changed.Subsequently,the influence of gelation reagents types,the gelation reagents mass fraction,the centrifugal defoaming rate,the aging process,and the replacement process were systematically analyzed and discussed.Secondly,the optimal process for preparing ANFA was explored.The optimal aerogel preparation process was determined by comparing different drying processes,displacement processes,supercritical drying conditions and the volume of the mold.Three different aerogels were prepared by changing the mass fraction of the acetonitrile gelation reagent.The structure was characterized by means of infrared spectroscopy,scanning electron microscopy and BET analysis.The performance was tested by infrared microscopy,fluorescence microscopy,and laser confocal microscopy.The results show that this aerogel has a low thermal conductivity(0.026 W·m-1 K-1)and fluorescence effect.Finally,according to the thermal gravimetric analysis of ANFA,the carbonation process was designed and verified,and aramid nano-carbon fiber aerogels were successfully prepared.The structure and composition of aerogels in different stages of the carbonation process were studied by scanning electron microscopy,infrared spectroscopy,Raman spectroscopy,XRD and XPS.The results show that amorphous carbon and graphite microcrystalline were gradually formed as the carbonizationtemperature increased.The specific surface area and pore size distribution of aramid nano-carbon fiber aerogels were studied by BET analysis.The results demonstrate that the surface of nano-carbon fibers contained a large number of micropores.The specific surface area of carbon aerogel was as high as 1490 m2g-1,which was much higher than that of similar carbon aerogels.