Study On Thermal Properties Of Adipic Acid Phase Change Materials Doped With Rare Earth Oxides For Heat Storage

Adipic acid(AA)is a kind of phase change thermal energy storage material for middle temperature field,which has the advantages of high phase change latent heat and low degree of cooling.But there are also shortcomings,such as easy to aging,latent heat easy to decay after long-term use.The adipic acid was modified to improve its thermal performance which is of great significance to expand the application of organic phase change materials.The rare earth can improve the comprehensive performance of materials significantly,which has been widely used in the field of organic materials.And our country is rich in rare earth resources.As a modifier,rare earth has a very good development prospect.Therefore,this research focuses on the modification of adipic acid,selecting rare earth oxides as modifiers,obtaining rare earth doped phase change materials by melting and mechanical mixing process.On the basis of detailed characterization of phase structure and microstructure of phase change materials,the effects of different rare earth oxides doping on the structure of the materials have been discussed.At the same time after thermal cycles,the thermal properties of materials have been characterized to explore the influence law of different rare earth oxides on the thermal properties of adipic acid phase change materials.Then,for rare earth oxides which can effectively improve the thermal performance,further study the influence of its content on the thermal performance of materials and the thermal performance after repeated cycles,to provide the theoretical basis for the modification of adipic acid or other phase change materials.Adipic acid phase change materials for heat storage were prepared by doping with three kinds of rare earth oxides(erbium oxide,praseodymium oxide,dysprosium oxide).By test characterization of XRD,FT-IR and DSC,between rare earth oxides and adipic acid combined with the physical way,maintaining their own characteristics and good compatibility.After thermal cycling,chemical reaction did not occur between rare earth oxides and adipic acid.The material remains complete crystal structure.Adipic acid as the heat storage characteristics of phase change materials did not change.As modifiers,three kinds of rare earth oxides can keep the performance of adipic acid in the short-term use.After 1000 thermal cycles,the thermal stability of adipic acid decreased after adding erbium oxide and praseodymium oxide.Only the adipic acid doping of dysprosium oxide has good thermal stability.A series of adipic acid phase change materials were prepared by selecting different amounts of dysprosium oxides.The optimal amount of dysprosium oxide is 0.5wt%.And the melting enthalpy and the enthalpy of solidification were the highest,which were 259.6J/g and 250.4J/g,respectively.The melting and freezing phase transition temperatures were 151.2? and 146.7?,respectively.During the process of multiple thermal cycles,the change of the phase transition temperature of the material was not regular.When the content of dysprosium oxide exceeded 1wt%,the melting enthalpy and the enthalpy of solidification of the material decayed greatly.When the content of dysprosium oxide was 0.5wt%,the latent heat of the material decayed the least.After 1000 thermal cycles,the melting enthalpy and enthalpy of solidification decayed 11.8% and 8.8% respectively.The melting enthalpy and solidification enthalpy of pure adipic acid attenuated up to 16.1% and 13.7%.This shows that the addition of 0.5wt% dysprosium oxide can effectively improve the thermal stability of adipic acid phase change material.The microstructure of the material is complete.There is almost no change in the phase structure.The chemical environment of each element in the material remains stable.