Investigation Of Preparation,Characterization And Performance Of Microencapsulated Phase Change Materials Via Perforated Cenosphere

Reducing carbon dioxide emissions is an important way to achieve peak carbon emissions and achieve carbon neutrality around the world,and reducing energy consumption in buildings is one of the effective measures to reduce carbon dioxide emissions.The cement-based heat storage material can effectively reduce the energy consumption of buildings and realize the efficient use of clean energy.Thus,the cement-based heat storage material is of great significance in reducing the energy consumption of buildings.As the main component of cement-based heat storage materials,phase change material(PCM)has the disadvantage of poor compatibility with cement-based materials,which can be effectively eliminated by microcapsule technology.The intrinsic strength of commonly used phase change microcapsules is low,which can easily cause defects of cement-based heat storage materials such as reduced strength and loose structure.The perforated cenosphere phase change microcapsule(CenoPCM)has potential advantages in overcoming the above defects over conventional PCM,but there is a gap between surface coating researches of encapsulating CenoPCM and the performance control of cement-based materials.Thus,PCM energy storage technology and microcapsule technology were used to prepare microencapusulated PCM(MPCM)by functional transformation of perforated cenospheres in this paper based on the National Natural Science Foundation of China(51728201 and 52008003).Paraffin wax was used as the core material of MPCM.The preparation,microencapsulation and performance of CenoPCM were investigated.The design and performance control of cement-based heat storage materials using CenoPCM were systematically investigated.Ethyl cellulose coating(EC),silica coating(SC)and ethyl cellulose/silica hybrid coating(HC)were used to microencapsulate CenoPCM.The preparation parameters and performance characterization of ethyl cellulose coating-CenoPCM(EC-CenoPCM),silica coatingCenoPCM(SC-CenoPCM)and ethyl cellulose/silica hybrid coating-CenoPCM(HCCenoPCM)were investigated.The influence of four MPCM on mechanical and thermal properties of mortar was analyzed;the evolution of the microstructure and the hydration reaction process of four MPCM in cement-based materials were clarified;the mechanism of action and microstructure of four different MPCMs in cement-based materials were revealed;and the highly efficient method was developed based on four different MPCMs in cement-based materials.The main contents and results of the research are as follows:1.CenoPCM was prepared by vacuum saturation method,and its surface morphology,composition and thermal properties were systematically evaluated.The influence of the dosage of CenoPCM on the mechanical and thermal properties of the cement mortar was investigated,and the micromechanism of CenoPCM action in the cement hydration reaction was elucidated.CenoPCM reduced the compressive strength and thermal conductivity of the mortar.The phase change effect of paraffin wax in the core material reduced the peak value of internal temperature rise of mortar,delayed the onset time of the peak value of internal temperature rise,and decreased the exothermic peak intensity of C3S.But there is no obvious effect on the total heat release of the cement.Moreover,the hydration of cement containing CenoPCM was promoted by the nucleation effect of CenoPCM.2.The ethyl cellulose coating with well sealing was used to microencapslate the CenoPCM to prepare the EC-CenoPCM.The regulation mechanism of the morphology and thermal properties of EC-CenoPCM with different concentrations of ethyl cellulose solution were evaluated.And the optimal parameters of the ethyl cellulose coating were determined.The mechanical and thermal properties of cement-based materials containing EC-CenoPCM were systematically investigated.Corresponding relationships between the mechanism of the hydration reaction in cement-based heat storage materials containing EC-CenoPCM and the evolution of the microstructure were clarified.Leakage of paraffin wax from EC-CenoPCM was effectively alleviated and the interface between the cenosphere and cement matrix was strengthened,promoting the development of mechanical and thermal properties of mortar,increasing the thermal conductivity of mortar.Furthermore,the internal temperature rise of EC-CenoPCM mortar was reduced and the emergence time of the peak of internal temperature rise was delayed due to the phase change effect of paraffin wax.And the heat flow of C3S was reduced after adding EC-CenoPCM without significantly affecting the total heat of hydration.3.The silica coating with high thermal conductivity was used to microencapsulate the CenoPCM to prepare the SC-CenoPCM.The regulation mechanism of the morphology and thermal properties of SC-CenoPCM with different concentrations of sodium silicate solution was evaluated.And the optimal parameters of silica coating were determined.The mechanical and thermal properties of cement-based materials incorporated with SC-CenoPCM were systematically investigated.And the correspondence of hydration reaction and microstructure evolution were clarified.The hydration reaction of cement was accelerated and the CH content of cement paste was reduced due to the pozzolanic activity of the silica.In addition,the interfaces between the cenosphere and the cement matrix were strengthened by silica coating.Thus,the compressive strength and thermal conductivity of mortar were improved.The SiO2 coating did not change the phase change effect of paraffin wax,reducing the internal temperature rise of mortar and the hydration heat flow of C3S.4.HC-CenoPCM was microencapsulated by ethyl cellulose/silica hybrid coating with well sealing and high thermal conductivity.The morphological and thermal properties of HC-CenoPCM were regulated using tetraethyl orthosilicate with different content,and the optimal preparation parameters were obtained.The influence of HC-CenoPCM content on the mechanical and thermal properties of mortar was systematically explored.And the corresponding relationships between the mechanism of HC-CenoPCM in cement hydration reaction and the evolution of the internal microstructure were clarified.The volcanic activity of SiO2 in the hybrid coating accelerated the hydration of the cement.The synergistic effect of EC and SiO2 enhanced the interface between the cenospheres and the cement matrix,increased the mechanical properties and thermal conductivity of the mortar,and reduced the porosity.Moreover,the hybrid coating did not affect the phase change effect of paraffin wax.And HC-CenoPCM still had the ability to regulate the temperature rise in mortar,and reduced the hydration heat flow of C3S.The research results in this paper provide the theoretical basis for the design and evaluation of coating methods in MPCM,and provide key technical support for the application of coating technology and phase change microcapsule material in the building materials.It is of great significance to promote the development of thermal storage materials and cement-based heat storage materials,and reduce building energy consumption,which helps to realize the dual development strategic goal of carbon neutrality and peak carbon.Figure 103 Table 29 Reference 194...