Preparation And Characterization Of Thermally Enhanced Wood-based Phase Change Materials

In this thesis,in order to solve the problem of leakage and huge volume change,the form-stable phase change materials(PCM)were fabricated by impregnating PCM into wood.Moreover,the thermal conductivity of composite PCM was effectively enhanced by introducing the enhanced heat transfer network of graphene aerogel and copper inside wood through one-step hydrothermal method and in-situ chemical deposition.The specific research content are as follows:(1)Mechanism study in wood-based PCM fabricated by impregnating graphene aerogel-encapsulated polyethylene glycol(PEG)into wood.The specific porous structure of graphene aerogel inside wood not only improves the thermal conductivity,but also helps to solve the problem of liquid leakage.The SEM result showed that after impregnation,PEG was encapsulated by graphene aerogel and filled into wood lumen successfully.The DSC exhibited that composite PCM had a large latent heat of 107 J/g without evident liquid leakage after 100 thermal-cooling cycles,indicating composite had great thermal energy storage capacity and thermal cycle stability.In addition,the thermal conductivity of composite PCM was improved to 0.53 W/(m*K)by introducing graphene aerogel into wood,which was 654% higher than that of pure wood.(2)Mechanism study in wood-based composite PCM prepared by impregnating phase change microcapsules and subsequent in-situ chemical deposition of copper inside wood lumen.PCM was encapsulated into microcapsules to form a stable core-shell polymer,which could solve the leakage problem effectively.After impregnation and reduction,wood lumen has been filled with copper prepared by reducing copper ions,developing a continuous metal-scaffold along wood transport tissues,which improved the thermal conductivity effectively.The SEM showed that,microcapsules coated with copper and filled into wood lumen,and there was no obvious interface transition between wood,microcapsule and copper.The DSC and LFA test exhibited that,composite had a great enthalpy(94.6 J/g),thermal cycles stability(approximately 4%),thermal conductivity(0.53 W/(m*K)).(3)Mechanism study in graphene/ hyperbranched polyurethane phase change wood.In previous study,we prepared the form-stable liquid-solid composite PCMs which were able to thwart the leakage problem.However,this was a partial solution to this leakage problem due to the liquid-solid phase change property.Therefore,in order to completely solve the leakage problem,the solid-solid wood-based PCM was prepared by using solid-solid polyurethane fabricated by grafting PEG onto triethanolamine as PCM,graphene as a thermal conductivity promoter and wood as supporting materials.The DSC and TG test indicated that composite had a high thermal energy storage capacity of 70.3 J/g,thermal stability and thermal-cycle stability.The thermal conductivity of composite was improved to 0.417 W/(m*K)which was 414% higher than that of wood after adding graphene.