Preparation And Properties Of Form-stable Phase Change Materials With Enhanced Thermal Conductivity

The temperature of phase change material(PCM) changes little when happening in the phase transition. At this time, a large number of heat would release and absorb along with the phase changing. Using this principle, the air or solar energy and the other renewable energy can be stored in the PCM. However, it occurs flowing when the PCM at solid-liquid phase transition. Moreover, it gives much inconvenience at the actual use as the low thermal conductivity of PCM. To solve these problems, the form-stabled and thermally conducted of the PCM is an effective solution.In this thesis, ethylene-vinyl acetate co-polymer(EVA) and paraffin is the supporting material and PCM, respectively. The effects of different processing methods to the impact of leakage rate have been studied. The research shows that the melting method is the best preparation process. The from-stable phase change materials(FSPCMs) have the optimal properties when paraffin is 70 wt%. Expanded graphite(EG) as conductive filler was added into FSPCMs, the effects of EG content to the impact of composites properties have been studied. The research indicates that the FSPCM composites have the best properties when EG is 8 wt%. Carbon fiber(CF) as another conductive filler was added into EG-FSPCMs, part of EG was substituted by CF, the effects of CF content to the impact of composites properties have been studied. The research reveals that the PSPCM composites possessed superior properties when CF is 20 wt% in conductive fillers. At this time, Thermal conductive network has been built in the orientation.The carbon aerogels were directly prepared by modified hydrothermal method and cryodesiccation from the aqueous, fluid solutions of carbon nano tubes(CNTs) and graphene oxide(GO). GO was prepared from flake graphite by modified Hummers' method. The CNT dispersions were mixed by ten times of Na DDBS(C12H25C6H4SO3Na)and then the dispersions are sonicated for 12 h. The paraffin and paraffin/EVA wasadded into different carbon aerogels at 70 ? and 130 ? for 1 hour to prepare FSPCMs,respectively. The results demonstrate that CNTs can further prove the thermal conductivity, the properties of composites was further proved with the adding of EVA.