Preparation And Thermal Properties Of N-dodecanol@SiO₂ Microencapsulated Phase Change Materials

Phase change materials?PCMs?absorb and release heat though the latent heat when materials occurs phase change.It can solve the energy imbalance in time and space,and improve energy utilization efficiency,especially in building energy conservation.However,PCMs is liable to cause leakage,volume change and react with the external environment because of its fluidity when the phase changes occur,which limits its application scope.Microencapsulated phase change materials?MEPCMs?can solve this problem though packaging technique.In this article,we choose n-dodecanol as the core material and SiO₂ as the shell material to prepared n-dodecanol@SiO₂ MEPCMs with different methods.We also characterized and tested their microstructure?chemical constitution and thermal properties.We chose tetraethyl orthosilicate?TEOS?as the silicon precursors and prepared a series of MEPCMs with sol-gel method.We studied that the mass of emulsifier?pH?mass ratios of n-dodecanol and TEOS influenced on the phase change properties and microstructure of MEPCMs.We concluded that when the mass of emulsifier was 1.5g,pH was 2.45 and n-dodecanol/TEOS was 2:3,the MEPCMs had a comparative better disperse structure and uniform size.The DSC result showed the melting enthalpies were 103.4J/g,solidifying enthalpies was 99.64J/g.The FTIR revealed that there was only physical combination between n-dodecanol and SiO₂.In this article,we also chose sodium silicate as the precursor of silica to prepare n-dodecanol@SiO₂ MEPCMs.We set different mass ratios of n-dodecanol/SiO₂.We tested the result of FTIR?DSC?TGA and SEM.The results indicated that when the mass ratio of n-dodecanol/SiO₂ was 4:1,the MEPCMs had a nearly spherical and compact surface structure.DSC result revealed that the MEPCMs exhibited similar phase change characteristics to pristine n-dodecanol,which melted at 21.03 °C with a latent heat of 116.7 J/g and solidified at 19.58 °C with a latent heat of 114.6 J/g.Compared with these two kinds of MEPCMs prepared by sol-gel method and chemical precipitation method,including microstructure,craft process,phase change properties and thermal stability,we concluded that the MEPCM prepared by chemical precipitation method had an advantage over sol-gel method.They advantaged in operation process,materials cost,thermal properties.So they have better practicability in building energy conservation.