| From the automobile in daily life to the large aircraft in the field of aerospace,the lightweight of materials is very important,which is the trend of the development of science and technology in the 21 st century.It is a challenge to realize lightweight and high function in the development of lightweight materials.It is an effective way to realize lightweight and high function by constructing and controlling the microstructure of materials by different methods.Based on this,the porous polystyrene(PS)aerogels and the derived hypercrosslinked PS aerogels,the MWCNT carbon foams,and the MWCNT/MXene composite carbon foams were successfully fabricated through the physical gelation of syndiotactic PS by high internal phase emulsion(HIPE)template method and freeze drying method respectively.The porous morphologies,the oil absorption and electromagnetic shielding(EMI)properties were studied.The main results are divided into the following three parts:Porous PS aerogels were successfully prepared from the HIPE method with the1,2,4-trichlorobenzene(TCB)solution of syndiotactic PS(sPS)as the continuous phase,glycerol solution of NaCl as the dispersed phase and sulfonated atactic PS(SaPS)as stabilizer.The derived hypercrosslinked PS aerogels were obtained by Friedel-Crafts alkylation reaction.The microstructure and oil absorption properties of aerogels were studied.The aerogels exhibit interconnected macropores and nanofibrous pore walls.Moreover,these aerogels show high absorption capacity for both surface oil and underwater oil.The maximum oil absorption capacity of toluene can reach 39 mL/g,which is due to the high hydrophobicity and the existence of interconnected macroporous structure and nano-fibrous structure.The supercrosslinked polystyrene-based composite carbon aerogels were successfully prepared by the high internal phase emulsion template method combined with the supercrosslinking reaction and the carbonization process.The microstructure and electromagnetic shielding properties of the composite carbon aerogel were studied.The results show that after the carbonization process,the composite carbon aerogel still preserves the interconnected macropores endowed by the high internal phase emulsion template method and the nanofibrous structure produced by sPS crystals.The electromagnetic shielding effectiveness of these carbon aerogels is excellent and increases with the increase of the content of highly conductive MWCNT due to the formation of the graphitized structure.The average electromagnetic shielding effectiveness of the CsPS/MWCNT-15 composite carbon aerogel with a thickness of 5mm in the X-band is 65 d B.Furthermore,the electromagnetic shielding effectiveness of composite carbon aerogel filled with MWCNT and Ni@CNT was studied.It was found that the average electromagnetic shielding effectiveness of Cs PS/MWCNT-2.5/Ni@CNT-7.5 composite carbon aerogel with thickness of 5mm reached 74 d B in Xband because the high conductivity of MWCNT and the high magnetic conductivity of Ni@CNT enhance the electromagnetic shielding effectiveness of the composite carbon aerogels.MWCNT and MXene composite frameworks were prepared by freeze-drying.Then sPS in TCB solution was poured into the composite frameworks by solution casting and the MWCNT/MXene carbon foams with dual conductive networks were successfully prepared by hypercrosslinking and the following carbonization.The influence of MWCNT/MXene content ratio on electromagnetic shielding performance of the carbon foams was studied.The results show that the EMI SE of the MWCNT/MXene carbon foams increases firstly and then decreases with the increasing of MWCNT and MXene content ratio.The average EMI SE of 4-MWCNT/6-MXene carbon foams with a thickness of 2 mm in the X band is maximum at 40 dB.The one-dimensional MWCNT and two-dimensional structure MXene together form a three-dimensional conductive network and provides multiple interfaces for the reflection and absorption of electromagnetic waves. |
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