Preparation And Thermal Insulation Characterization Of Carbon Aerogel Through Self-sacrificial Salt Templaing Routine And Solvothermal Method

Carbon aerogels have broad application prospects in the fields of adsorption,energy storage and ultra-high thermal insulation.Especially,the application of ultra-high thermal insulation puts forward an urgent demand for carbon aerogels.However,the practical application of carbon aerogels is restricted by the long preparation cycle,expensive cost and low intrinsic strength of carbon aerogels.Based on the theoretical basis that micropores can help to reduce the thermal conductivity of carbon aerogels,this paper firstly proposed the self-sacrificial salt templating routine assisted with solvothermal method to prepare carbon aerogels with high mechanical strength and low thermal conductivity at a low cost and high efficiency.Resorcinol and furfual were used as carbon precursors,methonal as solvent,hexamethylenetetramine as base catalyst,nitric acid as acid catalyst and annonium thiocyanate as self-sacrificial salt templates.Initially,the solvothermal treatment process was studied and an acid-base two-step catalysis process was put forward.The influence of process parameters of the solvothermal method on the characters of carbon aerogels was studied.Then,on the basis of researching solvothermal method,the self-sacrificial salt templating routine assisted with the solvothermal method was used to prepare the carbon aerogels with high microporous content and improve their thermal insulation performance.Finally,ultra-high thermal insulation materials,carbon aerogels with excellent mechanical strength and low thermal conductivity,were obtained.?1?According to the principle of single variate,the influence of process parameters during the acid-base two-step catalysis process and solvothermal method on the characters of carbon aerogels was studied.When the molar ratio of A/R was 0.05,H/R=0.01,M/R=45,pyrolysis temperature was 900? and the time of solvothermal treatment was 24h,the shrinkage rate during ambient drying was approximately 4%,the density of the prepared carbon aerogels was 0.26g/cm³,BET specific surface area and pore volume were up to 828m²/g and 1.322cm³/g,respectively.The carbon aerogels with low shrinkage rate,low density and high specific surface area established a basis for the research of next self-sacrificial salt templating routine.?2?In order to improve the microporous specific surface area for preparing carbon aerogels with low thermal conductivity,the self-sacrificial salt templating routine assisted with solvothermal method was proposed.The characteristic of thermal decomposition and the mechanism of forming nanopores through self-sacrificial salt templates,as well as the influence of process parameters on the properties of carbon aerogels were studied.The selected NH₄SCN salt could be removed completely through its own volatilizing and decomposing during the carbonization pyrolysis process and so it was self-sacrificial.The self-sacrificial salt mainly became small salt template molecules embedded and filled in the organic 3D nano network skeleton and thus played the role of salt template to increase the content of micropores in carbon aerogels.When the content of self-sacrificial salt template S/R was 1 and stirring time was 1.5 h,the shrinkage rate during ambient drying was only 2%,the density of carbon aerogels was 0.22g/cm³,the BET specific surface area was 1131m²/g and the microporous specific surface area was 771m²/g.?3?The compression property and thermal insulation performance of carbon aerogels were studied,and the influence mechanism of microstructure on strength and thermal insulation mechanism of carbon aerogels were analyzed.When the density of carbon aerogels was higher than 0.21 g/cm³,the compressive strength of carbon aerogels was not less than 4.5MPa and the compressive modulus was not less than80MPa.The high mechanical strength of carbon aerogels was due to the formation of highly cross-linked 3D nanometer network framework and thick joint neck structure.For carbon aerogels prepared at S/R=1 and t=1.5h,the solid thermal conductivity and gaseous thermal conductivity at room temperature were 0.0279W·m^-1·K^-1 and0.0187W·m^-1·K^-1,respectively.At 1800?,the thermal conductivity at ambient pressure was 0.3721W·m^-1·K^-1,in which gaseous thermal conductivity accounted for only about11%.This indicated that micropores significantly inhibited gaseous thermal conduction.In this paper,carbon aerogels prepared through the self-sacrificial salt templating routine assisted with solvothermal method have good thermal insulation performance and excellent mechanical properties.Moreover,the preparation period is short,the cost is low and the nanopores of carbon aerogels can be precisely adjusted.Through improving the content of micropores to reduce thermal conductivity,the obtained carbon aerogels have great potential applications in the field of ultra-high thermal insulation.