Preparation And Performance Study Of Multifunctional Cellulose-based Thermal Management Material

Along with the integrated and miniaturized development of advanced electronic devices,thermal management systems with high operating efficiency are ungently demanded.Thermal management materials（TMMs）,a core of thermal management systems,can realize the dispersion,storage and conversion of heat energy.However,traditional TMMs are hard to catch up with the rapid development of modern science and technology.Therefore,advanced TMMs are desired to be researched.Unfortunately,TMMs only equipped with the capability of managing heat-energy would limit their application scale.Multifunctional TMMs urgently need to be prepared so as to further promote their application value.The research work of this paper includes the following three parts:（1）The NFC/BN&MXene（BN/MX）"sandwich"structure of composite film was fabricated by vacuum-assisted filtration.The NFC/BN thermally conductive layer provided the composite film with excellent thermal conductivity（TC）,and the MXene conductive layer provided the composite film with electromagnetic interference shielding performance.The highest in-plane and through-plane TC of the BN60/MX100 composite film reaches 33.1 W m^-1 K^-1 and 1.07 W m^-1 K^-1 which are increased by 2269%and 664%compared with pure NFC film,respectively.The highest EMI SE_T of the BN40/MX150 composite film reaches 44 d B.The composite films designed in this work could be used as thermal interface material with high thermal conductivity,electromagnetic interference（EMI）shielding performance and surface electrical insulation in the thermal management system.（2）Nanofibrillated cellulose/aminoated multiwalled carbon nanotube（NFC/NMWCNT）aerogels were prepared by sol-gel method and ice template method,and then MXene/PEG hybrid melt was encapsulated into NFC/NMWCNT aerogel framework by vacuum impregnation method to acquire the MXene@PCMs.The hydrogen bonds formed between the amino groups of NMWCNT surface and the hydroxyl groups of NFC molecular chains endowed the supporting framework with ideal strength.Furthermore,the introduction of NMWCNT and MXene endowed the high TC and enhanced photo-thermal conversion capability of the MXene@PCMs phase change composite.The TC of 1.8 wt%MXene@PCM is 0.5 W m^-1 K^-1,which is85%higher than that of pure PEG;the phase transition enthalpy is 162.3 J/g,and the enthalpy retention rate is 91.3%;the photo-thermal conversion efficiency is 91.8%.The MXene@PCM composite materials designed in this work exhibit high energy storage density,enhanced thermal conductivity,and good shape stability,which can be applied to efficient light-to-heat conversion and storage as well as thermal management system.（3）Ni-plated melamine sponge（Ni@MS）was prepared by chemical deposition process,then Ni@MS/RCG hybrid aerogel was obtained by a simple sol-gel method,and MX/Ni@MS/RCG/PEG phase change materials（PCMs）was obtained by assembling hybrid aerogel and MXene films in molten PEG.MX/Ni@MS/RCG/PEG PCMs exhibit good shape stability capacity,excellent cycling stability,large latent heat,high TC and excellent EMI shielding performance.At the GNPs content of 0.39 wt%,the TC of MX/Ni@MS/RCG-5/PEG is 0.47 W m^-1 K^-1,which is 74%higher than that of pure PEG.Its molten enthalpy value is 154.3 J/g,showing a high latent heat retention rate of 98.1%.These properties are very compatible with thermal management applications,and the temperature change of MX/Ni@MS/RCG-5/PEG is much faster than that of pure PEG,indicating the excellent capability of heat storage and release of sample.Ni@MS framework（0.24 S/cm）and MXene film（329.85 S/cm）have ideal electrical conductivity,and the best EMI SE_T of MX/Ni@MS/RCG-5/PEG reaches 32.7d B,which is higher than commercial requirements for EMI shielding materials（SE_T>20 d B）.