Preparation And Characterization Of Salt/xonotlite Composite Phase Change Energy Storage Materials

One of the main directions of preparing a high temperature phase change material is to make PCM complex in a common matrix with the feature of good corrosion resistance. Many studies present that inorganic salt/ceramic phase change materials will be a hopeful way to prepare a energy material for high temperature workplace(>600℃),but at present the main results show that the disadvantage is the low content of salt in composite phase change materials.Ultra-light xonotlite-calcium silicate was synthesized via hydrothermal processing, by novelly using carbide slag and silica fume as the raw materials, and the microstructure, parameters of pore structure of synthesized xonotlite were studied in this thesis, the possibility and superiority of xonotlite being used as the basic body of composited phase change energy storage materials were also discussed at the same time. The results indicated that the process parameters of hydrothermal synthesis did not need to adjust even though carbide slag and silica fume containing a small amount of impurities. The shape-stabilize xonotlite body was produced by vacuum forming technology, which has advantages of simple equipment and easy shape controls, and cylindrical xonotlite body and globular xonotlite body were produced in this thesis.Through infiltrating experiment, Na2SO4/Xonotlite composite phase change energy storage material, NaCl/Xonotlite composite phase change energy storage material, KCl/Xonotlite composite phase change energy storage material were fabricated successfully, and the infiltration percentage is 90%. The mechanism and influence factors of infiltrating process are studied in this thesis, the infiltration technology was ascertained after discussing the correlation of infiltration temperature, infiltration percentage. The practical combination of phase change material with xonotlite body was studied using XRD and SEM measurements, and the results showed that high temperature chemical compatibility and wetting between molten salt and xonotlite body, no new substance appeared, xonotlite body and molten salt were combined very well with wetting and mechanical inserting.The thermo-physical properties including latent heat, heat storage density, conductivity, specific heat, thermal diffusivity, thermal expansion coefficient and thermal cycle were studied by using Differential Scanning Calorimetry (DSC), laser thermal constant instrument and dilatometer. The results showed that the contents and the properties of PCM were major determinants of the thermodynamic properties of composite phase change energy storage materials, the latent heat, heat storage density and thermal expansion coefficient were proportional to PCM contents. The values of thermal expansion coefficient that all three prepared composite phase change energy storage materials showed were higher than common ceramics, and the thermal conductivities of composite materials were all higher than the value of common ceramics.Three new composite phase change energy storage materials with the advantage of high infiltration percentage and high temperature recycle scope were prepared successfully, it is also a good method to prevent pollution and make use of waste by synthesizing environmental friendliness xonotlite-calcium silicate via hydrothermal processing, by novelly using carbide slag and silica fume as the raw materials, and provided a new application for xonotlite at the same time. This work set a new direction for preparation of composite phase change energy storage materials,and laid the groundwork for practical applications in the future.