Research On The Nano-composite Modification And Properties Of Ba(OH)2·8H2O

The explosion of energy crisis and deterioration of the greenhouse effect have made people realized that energy saving and emission reduction are long–term and arduous missions.Phase change thermal energy storage material?PCTESM?is a kind of material,which is cheap and easy to be obtained.PCTESM can not only reduce the mismatch between supply and demand of energy to improve energy efficiency,but also play a very important role in terms of energy storage and conversion.Ba?OH?₂·8H₂O has a quite extensive prospect when it acts as the PCTESM due to its high enthalpy and low price.However,there are serious problems of Ba?OH?2·8H2O,such as large supercooling and phase separation.These problems severely impede the practical engineering application of Ba?OH?₂·8H₂O.This paper starts from the perspective of reducing supercooling temperature and phase separation of Ba?OH?2·8H2O.We get the best nucleation properties of modi-fied Ba?OH?₂·8H₂O through studying the adding methods and contents of nucleation agent nano Y2O3 and thickening agent HEC.Then the properties of modified Ba?OH?₂·8H₂O were characterized.This paper mainly includes the following aspects:The modified Ba?OH?₂·8H₂O was prepared by adding the dispersion of na-nometer Y₂O₃ and HEC,and the dispersion has been dispersed already by ultrasonic dispersion method.The result shows that the content of 0.9%Y₂O₃+0.7%HEC+2mL DW has the lowest supercooling temperature,the supercooling temperature is about0.5?.Both of the nanometer Y₂O₃ and the HEC have the abilities of efficiently re-ducing the supercooling temperature of Ba?OH?2·8H2O.We obtain the microscopic morphology through the method of scanning electron microscopy?SEM?,which helps us to point out the best crystallization properties comes from the content of 0.9%Y2O3+0.7%HEC+2mL DW.With the help of DSC and TG-DSC testing method,the thermophysical property data of both Ba?OH?₂·8H₂O and modified Ba?OH?₂·8H₂O was acquired.According to the thermophysical data,we find out that the phase change enthalpy of modified Ba?OH?₂·8H₂O has decreased 19.2J/g.This is the cause of the additives content.The dehydration process of modified Ba?OH?₂·8H₂O has changed compared with the pure Ba?OH?₂·8H₂O.The specific heat has increased compared with the pure Ba?OH?₂·8H₂O.By means of Zeta potential and Raman spectrum,we study the surface of na-nometer Y₂O₃ interact with water molecule to form the new structure of YOOH and Y?OH?₃,and we explore the dispersibility of nanometer Y₂O₃and HEC dispersion.Furthermore,by integrating the SEM,DSC and the cooling curve data,we propose a possible mechanism of how the additives of nanometer Y₂O₃ and HEC help with de-creasing the supercooling temperature of Ba?OH?₂·8H₂O,and how the additives pro-mote nucleation.