Effect Of Additives On Phase Change Properties Of Sugar Alcohol And Their Nanocapsules

Sugar alcohol with high latent heat is a kind of phase change material used for heat storage.However,its high supercooling degree hinders its application.As two kinds of sugar alcohols,D-mannitol（DM）and inositol（IN）have broad application prospects IN heat storage at medium temperature.Mixing the two sugar alcohols yields many benefits,such as the melting point of binary sugar alcohols is lower than that of its component sugar alcohols,and thus the temperature at which it is applied is lower than that of monosaccharides.In order to solve this problem,nucleating agent alumina,silicon carbide and thickener sodium alginate were added to D-mannitol and binary sugar alcohols to reduce the supercooling degree of sugar alcohols.In order to solve the problems of leakage and oxidation during the phase transformation of sugar alcohol,the inorganic shell is used to encapsulate sugar alcohol.The effects of different types and concentrations of nucleating agents and thickening agents on the supercooling degree and other phase transformation characteristics of sugar alcohols were studied.It was found that the addition of nucleating agent alumina,silicon carbide or thickener sodium alginate could promote the nucleating crystallization of sugar alcohols and reduce the supercooling degree of sugar alcohols.The supercooling degree of mannitol and binary sugar alcohols decreased by 17.0 ℃ or more,but the influence degree of different concentrations on the supercooling degree of sugar alcohols varied greatly.While the addition of nucleating agent and thickening agent can further promote the nucleation crystallization of sugar alcohols,and the supercooling degree of mannitol and binary sugar alcohols decreased by 19.0 ℃ and 22.0 ℃ respectively.SEM of sugar alcohols with nanoparticle addition showed that the nucleating agent had better dispersion when combined compared with the nucleating agent and thickener alone.The DSC data of sugar alcohol samples were analyzed,and it was found that when the nucleating agent and thickening agent were added together,the supercooling of sugar alcohol samples decreased greatly and was relatively stable under the influence of thickening agent.Binary sugar alcohol nanocapsules were prepared using silica as shell at neutral p H.The phase transformation characteristics and thermal stability of the nanocapses were studied by DSC,SEM,THERMOgravimetric analyzer（TGA）and thermal cycling test.The supercooling degree of the two sugar alcohols decreased by 12.3 ℃ after encapsulation.In binary sugar alcohol capsule doping on the basis of the nano silicon carbide silicon carbide binary sugar alcohol nano capsule was prepared,the results show that after adding silicon carbide,capsule could improve the thermal performance,and super-cooling degree is further improved,reduced 17.3 ℃.And after 60 times thermal cycling,sugar alcohol crystal shape change,the supercooling degree was reduced by 32.2 ℃.