Research On Doping Modification Of MgO Natrix Phase Change Thermal Storage Materials

Phase change thermal storage materials play an important role in relieving energy pressure.They have the advantages of large heat storage density per unit weight(volume)and heat absorption and heat release within a small temperature range near the phase transition point.In this study,a phase change thermal storage material based on magnesium oxide was studied.MgO has a high melting point,good thermal conductivity,and a porous structure which is capable of making the phase change material distribute in the pores of the magnesium oxide matrix.In this paper,the preparation technology of Na2CO3/MgO and(K2CO3-Na2CO3)/MgO composite phase change thermal storage material was studied.After the dopants were added to the mixture,the structure and properties of the composite phase change materials were analyzed by using balance,vernier caliper,XRD,Tg-DSC and thermal conductivity meter.Moreover,the changes of density,thermal conductivity and heat storage density of the samples were investigated.After adding minor SiC to the Na2CO3/MgO composite phase change thermal storage material,the heat storage density of the material is obviously improve,reaching 1017J/g in the temperature range of 30-800?.After adding minor Bi2O3,its density,thermal conductivity and latent heat of phase change are also improved to different extents.The thermal conductivity is up to 3.6 W/mK,and the heat storage density is 850-910 J/g depending on the amount of addition.By testing the properties of the samples at different sintering temperatures,we can obtain the best properties when the cerium oxide-added samples are sintered at 840?.However,after adding Al2O3 and Fe2O3 to the(K2CO3-Na2CO3)/MgO composite phase change thermal storage material,the properties are reduced.After adding minor Bi2O3,its density and thermal conductivity increase,and the highest thermal conductivity can reach 2.4W/mK,but the latent heat of phase change materials is slightly reduced.The metal powders(Al,Fe and Cu)were separately added to the Na2CO3/MgO composite phase change thermal storage material and we divided them into two groups(sintered in air and vacuum).Results shows that the thermal conductivity and latent heat of phase change are decreased at the group sintered in air.The heat storage density of the sample added with Fe powder could reach 1086J/g.For the other group sintered in vacuum,the thermal conductivity of the phase change thermal storage material added with Cu powder increases,the latent heat of phase change decreases slightly,and the heat storage density is 1079J/g in the temperature range of 30-800?.Furthermore,the Al powder can make the thermal conductivity and heat storage density increase,but the metal Al powder will undergo a phase change at 670?.Thus,further research is needed.The addition of minor Bi2O3 and Fe powder can effectively improve the properties of the magnesium oxide-based composite phase change thermal storage material.