Preparation And Performance Investigation Of Carbide Slag Shape-Stable Phase Change Composites

Thermal energy storage（TES）is a key technology for achieving large-scale,low-cost utilisation of renewable energy,grid-valley electricity and industrial waste heat.Among them,the shape-stable phase-change composites（SSPCCs）combined sensible heat storage and phase change heat storage has the advantages of high heat storage density,strong corrosion resistance,high thermal conductivity,difficult phase separation,and unsuitable for supercooling.However,the skeleton materials of SSPCCs are mainly natural mineral resources,and large-scale mining of these materials has damaged the surrounding natural environment.Their mining and processing process consume a large amount of fossil energy,emitting a large amount of greenhouse gases,toxic and harmful gases such as carbon dioxide and sulfur dioxide.To make full use of industrial solid waste,this paper uses industrial solid waste carbide slag to replace the traditional skeleton materials,and uses Na NO₃ and Na₂CO₃ as phase change materials（PCM）,respectively,to fabricate SSPCCs by cold-compression&hot-sintering（CCHS）method.To obtain the optimum sample performance parameters,the key properties of the samples such as TES performance,thermal conductivity,compressive strength and thermal cycle stability were investigated using a synchronous thermal analyzer,laser flash meter,electronic universal material testing machine and a self-made cold and hot cycle test bench and so on.To improve the compressive properties of SSPCCs,silica sol,high temperature sealing AB glue and aluminium dihydrogen phosphate(Al H₆P₃O₁₂)were used as binders to study the variation of compressive strength of SSPCCs.The research results show that:（1）For carbide slag/Na NO₃ SSPCCs,when the mass ratio of carbide slag to Na NO₃ was5:5,the comprehensive performance of sample CC6 reached the best,with a compressive strength of 73.6 MPa,excellent compatibility between the components,and micromorphology showing a uniform distribution of carbide slag and Na NO₃ particles;In the temperature range of 100 to 400°C,the TES density of sample CC6 reached 447 J/g,with a melting point of282.5°C,latent heat of 59.61 J/g and thermal conductivity of 0.93 W/（m·K）,which has good TES and heat transfer performance;After 3700 heating/cooling cycles,the micro-flow of PCMs in the matrix was accelerated,which eventually led to the fracture of the sample;The slight change in the liquid specific heat of sample CC6 resulted in a slight increase in its TES density and thermal conductivity,but it still maintained excellent TES performance,heat transfer performance and component compatibility.（2）Carbide slag component is well compatible with Na₂CO₃ and can replace traditional natural skeleton materials to fabricate Na₂CO₃/carbide slag SSPCCs;When the mass ratio of carbide slag to Na₂CO₃ was 52.5:47.5,sample NC5 achieved the best comprehensive performance,with a TES density of 993 J/g in the range of 100 to 900°C,a compressive strength of 22.02 MPa and a thermal conductivity of 0.62 W/（m·K）;After 100 heating/cooling cycles,the TES performance of sample NC5 remained stable,while the thermal conductivity increased by 25.8%,which was due to the infiltration and adsorption of PCM in the pore structure of the skeleton material particles to improve the thermal conductivity of the skeleton material particles;The thickness of PCM“bonded bridge”between the skeleton material particles determines the compressive strength of SSPCCs;The compressive strength of fabricated SSPCCs is highest under the optimal PCM mass fraction;The cost analysis and carbon emission analysis show that the fabricated carbide slag/Na₂CO₃ SSPCCs have good economic and environmental benefits due to their low manufacturing cost and carbon emission.（3）When Al H₆P₃O₁₂ solution was used as the binder,the prepared SSPCCs had no leakage and deformation,and the compressive strength of sample AH200 series was up to 85.6 MPa,which was 16.3%higher than that of sample CC6;The compressive strength of sample AH300series was up to 98.9 MPa,an increase of 34.8%compared to that of sample CC6,which significantly improved the compressive performance of the SSPCCs;X-ray diffraction spectroscopy and Fourier transform infrared absorption spectroscopy confirmed good compatibility between the components and no new material components were produced;The micromorphology showed an overall reduction in the pore structure and a change in the internal morphology from an overall loose structure to a densified structure,with increased inter-particle bonding,thus improving the compressive performance of the SSPPCs.（4）The use of carbide slag as skeleton material to fabricate SSPCCs avoids its large-scale accumulation or landfill causing damage to the environment.The fabricated SSPCCs have advantages such as low cost,low carbon emissions,strong corrosion resistance,excellent TES performance,and stable thermal cycling performance.