Synthesis And Properties Of Clay-based Phase Change Materials

As the energy crisis deepened, sustainable use of energy and renewable research hadbecome hotspots at home and abroad. Thermal storage technology using latent heat ofphase transformation of materials for energy storage and conversion, the technologycould resolving the mismatching of energy supplying and demanding between thetime and space, renewable and sustainable the usage of energy. Phase changematerials (PCMs), refers to materials which could be used for energy storage by phasechange, had been widely used in industrial waste heat recycling, solar energy storage,and other fields.Single phase change materials always hard to storage and transportation; thesolid-liquid separation will emerge after phase change and any other defects in phasechange process. Phase change material composites could solve these defects. As far aswe know, there are three kinds of PCMs which is polymer sizing composites PCMs,microencapsule PCMs, and clay-based PCMs. The clay-based PCMs have advantagesof low cost, high thermal stability and thermal conductivity higher. In this paper, threekinds of PCMs had been prepared, to research the influence to the structures andproperties of the preparation methods of PCMs and clay modification.In this paper, the stearic acid (Stearic Acid, SA) had been employed as atransformation matrix, Na-Montmorillonite clay (Na+-montmorillonoid, MMT) hadbeen employed as a carrier, two different methed which called hot melt vacuuminjection and Solution dissolve immersion had been used to prepare two kinds ofPCMs, the samples named M-SA/MMT and S-SA/MMT respectively. Themorphology, structure and property were characterized by SEM, FT-IR, XRD andDSC. The results shows that two kinds of PCMs prepared by different method possesssame structures, there is not any chemical reaction between SA and MMT, theycombined only by physical bonds; accelerate thermal cycle (ATC) test shows thatM-SA/MMT performed better than S-SA/MMT.The thermal activation had been employed to conduct the MMT, and the PCMshad been prepared by melt vacuum injection which had been considerer as the betterone, the sample had been named M-SA/a-MMT. The morphology, structure andproperty also studied, the results showed that none chemical change have taken placebetween SA and activated MMT; ATC test shows that M-SA/a-MMT is a goodform-stable PCMs. Compare with M-SA/MMT, the results shows that thermalactivation can raise the property of PCMs.The attapulgite (ATP) had been employed as the carrier of PCMs.The attapulgite come from Linze, Gansu and had been activated by thermal activation.The PCMsnamed M-SA/a-ATP had prepared by melt vacuum injection as well. Studies ofmorphology, structure and property shows that SA had wrapped in the rhabdolith ofATP uniformly; and the SA also frozen in the montmorillonite flake layer inside theATP; the SA and ATP combine only with physical bonds, and ATC test shows that thestability of M-SA/a-ATP is good.The properties of M-SA/MMT, M-SA/a-MMT and M-SA/ATP had beenprepared with other PCMs from literatures. The results demonstrate that the propertyinproves markedly. The properties of M-SA/a-ATP and M-SA/a-MMT had beencompared, the results show that the adsorbability of MMT is better than ATP; the heatconductivity of M-SA/a-MMT is better than M-SA/a-ATP; the stability ofM-SA/a-ATP is better than M-SA/a-MMT.