Study On The Preparation And Performance Of Carbon Nanotubes Modified Cement-based Phase Change Materials

With the rapid growth of the world population and the continuous development of economy,human's dependence on energy is increasing day by day,and the problem of energy shortage is becoming increasingly prominent while building energy consumption is one of the main components of energy consumption.Phase change material(PCM)is a kind of energy storage material,which can change at specific temperature to store and release energy.It's of great significance for building energy conservation to improve energy efficiency and reduce building energy consumption in building materials.However,the organic phase change energy storage material has the problem of poor thermal conductivity and liquid phase leakage,their incorporation will also cause some adverse effects on the performance of building materials,which not only restricts energy storage function,but also brings inconvenience to the application.Carbon nanotubes(CNTs)and attapulgite are excellent nanofibers and adsorbable minerals,In order to improve the thermal conductivity of paraffin,prevent phase transformation leakage,and make up for the deterioration of mechanical properties of cement-based materials after adding phase change material to cement matrix,this paper took SDBS as dispersant to disperse CNTs in melted paraffin wax to study the effect of dispersant dosage and CNTs content on the thermal conductivity of paraffin wax;By using attapulgite as carrier to prepare composite stereotyped attapulgite-based phase change material in a way of adsorbing CNTs / paraffin thermal conduction enhanced phase change materials under vacuum condition,the adsorption properties of attapulgite to phase change materials were characterized by diffusion exudation ring,FT-IR and SEM,and the thermal physical properties of the composite phase change materials were studied;Apply different content of composite stereotyped attapulgite-based phase change material to cement based materials to study the effect on performance of cementitious materials and make an attempt to improve the mechanical strength and thermal conductivity of cementitous materials.The following conclusions are obtained by testing the performances of lots of samples prepared during the preparation process: The thermal conductivity of composite paraffin phase change material increases with the increase of dispersant dosage at the same CNTs content.When the mass ratio of SDBS to CNTs was 2:1,the thermal conductivity enhancement effect of composite paraffin wax began to stabilize;The thermal conductivity and energy storage rate of paraffin wax can be significantly enhanced by CNTs,and when the content of CNTs was 3%,thermal conductivity of paraffin wax increased by 39%.The optimal mass ratio of attapulgite adsorbing paraffin ratio was 2.5:1 under vacuum condition,the optimal mass ratio of attapulgite adsorbing CNTs modified paraffin phase change material was 2.25:1;FT-IR test shows that the adsorption of attapulgite on paraffin belongs to physical adsorption without new substance produced;DSC test turns out that the peak temperature of composite stereotyped phase change material decreases and phase transition enthalpy reduces in a proportion of paraffin content.Attapulgite can improve the water requirement of cementitious materials;Under the premise of molding,the mechanical properties of cement-based materials first increase and then stabilize with the increase of the amount of attapulgite composite phase change material;The mechanical properties of cementitious materials improves with 0.1wt% MWNT,but little effect on thermal conductivity of cement-based materials;Finally,the compressive strength,flexural strength and thermal inertia of CNTs modified cement-based phase change materials were improved,the mechanical properties and energy storage capacity were enhanced together.