Preparation And Property Of Lightweight Carbon Foam-based Phase Change Composites

As a result of the ever-growing consumption of non-regenerated energy,efficient thermal energy storage and significant energy transition are receiving widespread attention.Owing to the inherent superiority such as large phase change latent heat,good thermal cycling stability,chemical durability and environment-friendly properties,phase change materials?PCM?,especially solid-liquid PCM,have been extensively investigated as ideal energy storage media for thermal energy storage?TES?systems.Nevertheless,inherent problems of solid-liquid PCM?including easy leaking in melted state and low thermal conductivity?greatly restrict their widespread utilization in various fields.In this study,we prepared a phase change composite employing carbon foam?CF?as the support material and n-icosane as the heat storage element,combing high-temperature carbonization,nanocomposite and physical adsorption technologies and principles.The novel phase change composite had multifunctional functions such as large heat storage capacity,temperature and heat insulation,infrared stealth and photothermal conversion.Firstly,the content of this work was carbonization of melamine foam?MF?to obtain a lightweight and flexible porous carbon foam matrix?CF?.Then the CF was used to adsorb n-eicosane to prepare a phase change composite CF-PCMx.Structure and properties of the prepared materials were tested and analyzed by means of various characterizations.Results indicated that CF skeleton derived from MF through stabilization in air followed by carbonization in nitrogen at 400°C was flexible and highly porous,which ensured excellent mechanical support and large storage capacity of PCM.It could effectively adsorb PCM up to84%,and the phase change enthalpy of melting/crystallization reached 193.0/193.7 kJ/kg;Results of temperature regulation performance test showed the prepared phase change composite had the function of heat insulation and heat preservation in the processes of temperature rising/cooling,corresponding to the storage and release of thermal energy,respectively;Besides,there was significant difference in temperature and infrared thermography between CF-PCMx and the comparative samples as well as the ambient under the same heating conditions due to the heat storage and release of PCM.These all indicated that the prepared phase change composite can play an important role in thermal insulation and temperature regulation.Secondly,a novel phase change composite Ti₂O₃/PDA@CF-PCMx was fabricated by encapsulating n-eicosane into CF skeleton that had been pre-coated with titanium?III?oxide?Ti₂O₃?nanoparticles?NPs?employing a one-pot method,with the assistance of polydopamine?PDA?which possesses excellent adhesion.Morphological structures,as well as the properties of leakage-proof,thermal energy storage,temperature regulation and photo-thermal conversion of the fabricated phase change composite were investigated.Results indicated that due to the deposition of Ti₂O₃ NPs on the surface of CF skeleton,the surface roughness is improved and thus the adsorption stability of PCM on the matrix is enhanced,which endowed the fabricated phase change composite with enhanced leakage-proof property,the mass loss of the sample after being put on heating platform for 1 h at 80°C was only 2.96%.Photo-thermal conversion performance test showed that Ti₂O₃/PDA@CF-PCMx has a certain light-to-heat conversion capability due to the introduction of Ti₂O₃ NPs,which has excellent photothermal conversion property attributing to its intrinsic narrow bandgap.Finally,to regulate the pore structure of foam substrate from the structural level,bacterial cellulose?BC?aerogel was firstly introduced into the micron-sized porous structure of MF with the help of chitosan solution?CS?,following with carbonization to form a composite foam?CBCx-CS@CF?with a hierarchical porous structure.Then phase change composite CBCx-CS@CF-PCMy was obtained by asorbing PCM with CBCx-CS@CF.Results showed that,this method could effectively increase the specific surface area?BET?of composite foam,and when the concentration of BC was 5 mg/m L,the maximum BET value of composite foam was 16.3 m²/g,and it could stably adsorb the phase change material up to87%;The corresponding phase change composite had better leakage-proof performance compared with CF,and the mass loss of the sample after being put on heating platform for 1 h at 80°C was only 2.17%.In addition,electronic component protection test showed that,phase change composite CBCx-CS@CF-PCMy could effectively suppress the heating rate of the heatd element due to the existence of PCM,so as to control the temperature of the heated electronic element.