Performance Regulation And Functional Design Of Attapulgite-Based Composite Phase Change Thermal Energy Storage Materials

Energy shortage and environmental pollution remain severe global challenges.Solar energy is a clean and renewable energy.Efficient solar energy is an effective measure to alleviate energy conflicts and environmental problems.However,the application of solar energy is vulnerable to natural disadvantages such as intermittence,randomness,and volatility,resulting in a mismatch between supply and demand in terms of time,space,and intensity.Thermal energy storage technology is the most attractive strategy for utilizing solar energy and improving energy efficiency.Phase change material paraffin（P）is widely used because of its ultra-high volume power density and narrow temperature distribution in energy conversion and utilization.However,the application of mineral-based composite phase change materials in thermal storage and thermal management systems remains seriously restricted by the problems of phase change material leakage,low thermal conductivity,low photothermal conversion efficiency,and preliminary functional design.This paper fully explores the morphological structure and physical and chemical properties of attapulgite（ATP）minerals,and the advantages of mineral properties are integrated.The functional design of minerals fully utilizes the synergistic effect of material properties,and the defects of mineral-based composite phase change materials are solved.The application of minerals in new heat storage and wave absorption integrated materials for simultaneous microwave absorption and thermal energy regulation is expanded.To improve indoor thermal comfort and reduce building energy consumption.Attapulgite was combined with expanded perlite（EP）and graphite（GP）to construct mineral microspheres（AEG）.AEG can encapsulate paraffin（P）in its rigid structure（P-AEG）to effectively prevent leakage.The loading of P by AEG increased from 33.5 wt.%of P-ATP to57.8 wt.%of P-AEG.The solidification enthalpy of P-AEG increased from77.3 J/g of P-ATP to 118.4 J/g of P-AEG.The thermal conductivity of P-AEG reached 0.58 W/（m·K）,which was 44.4%higher than that of ATP.The new building material（P-AEG-C）prepared by compounding P-AEG with building materials such as cement indicates excellent photothermal conversion characteristics and thermal energy storage capacity.At the peak position of the heating stage and the bottom position of the cooling stage,the temperature of P-AEG-C is 3.9℃lower and 7.5℃higher than that of concrete,respectively.In addition,P-AEG-C indicates good mechanical properties,and the compressive strength reached 14.8 MPa.The constructed AEG makes full use of the excellent compatibility of ATP with building materials,the high loading rate of EP,and the high thermal conductivity of GP.Therefore,P-AEG shows broad application prospects in photothermal conversion and energy-saving buildings and provides a strong theoretical basis and technical support for applying mineral-based composite phase change materials in buildings.To further optimize the thermal management ability of energy-saving buildings.Attapulgite and cellulose nanocrystals were configured into a suspension in a particular proportion.Spherical hierarchical porous microspheres（ACN）were constructed for encapsulating phase change materials by spray drying,calcination,and acid activation.ACN can encapsulate paraffin in its rigid structure（P-ACN）to prevent paraffin leakage.P-ACN indicates excellent shape stability,photothermal conversion characteristics,and latent heat storage capacity.P-ACN indicates significant advantages in the thermal management of energy-saving buildings,and the melting enthalpy is increased to 130.2 J/g.The holding time of P-ACN from 35℃to 30℃is about twice that of attapulgite-based composite phase change material（P-ATP）.The carbon material in ACN enhances the visible light absorption of P-ACN,which makes P-ACN have better photothermal response characteristics.The new building material（P-ACN-B）prepared by compounding P-ACN and building aggregate in a specific proportion indicates efficient photothermal conversion characteristics,excellent thermal management ability,and cycle stability.After multiple thermal cycles,it maintains exceptional photothermal conversion ability and heats storage ability.In addition,P-ACN-B indicates excellent mechanical properties,with a compressive strength of 14.2 MPa,and also has significant advantages in flame retardancy.The difficulty in synergistically improving the photothermal conversion ability and heat storage performance of mineral-based composite phase change materials remains an obstacle.Attapulgite was compounded with cellulose nanocrystals and graphite to construct composite mineral microspheres（ACG）as the core.A layer of urchin-like Ti O₂（ACGT）was coated on the surface of ACG by solvothermal method to encapsulate paraffin（P-ACGT）.In addition,to expand the adaptability of attapulgite microsphere morphology control.The composition,structure,and physicochemical properties of attapulgite are very similar to those of sepiolite,so we make an analogy study.The results show that the composite mineral microspheres prepared by attapulgite and sepiolite can effectively encapsulate phase change materials.The composite microspheres constructed by sepiolite（SCGT）have more significant advantages in encapsulating paraffin（P-SCGT）,which is related to the degree of mineral dissociation,mineral size,and mineral surface properties.The synergistic effect of the core-shell structure enables P-SCGT to achieve 94%photothermal conversion efficiency and 137.4 J/g melting enthalpy.The new building material（P-SCGT-M）prepared by mixing P-SCGT and building aggregate in a specific proportion indicates excellent thermal management ability,which can slow down the temperature fluctuation between day and night.After multiple heating and cooling cycles,it still has good cycle stability.To solve the influence of electromagnetic interference and significant heating on high-end electronic equipment.Attapulgite was used as the matrix material to adjust the dielectric constant,carbon nanotubes（CNT）as the dielectric loss material,Ni Co alloy as the magnetic loss material,and composite microspheres（ACNC）were constructed as the core.Urchin-like Ti O₂ coated microsphere core（ACNCT）encapsulates paraffin to prepare urchin-like heat energy storage and wave absorption integrated material（P-ACNCT）with core-shell structure.The results show that the urchin-like Ti O₂ morphology has unique advantages in encapsulating phase change materials.The melting enthalpy of P-ACNCT reaches 111.6J/g,which shows superior thermal energy storage capacity.Combining the dielectric Ti O₂ shell and the magnetic composite microsphere core,the core-shell microsphere structure mechanism can generate adjustable reflection loss and promote the impedance matching of complex permittivity and complex permeability.In the 2-18 GHz range,the effective absorbing bandwidth of P-ACNCT can reach 5.76 GHz when the thickness is only 1.6 mm,indicating that the composite has excellent absorbing properties.Based on the structural design of sea urchin-like core-shell microspheres,it is beneficial to synergistically improve the microwave absorption performance and thermal management ability of composite materials,which is of great significance for the simultaneous realization of electromagnetic interference shielding and thermal energy regulation of advanced electronic equipment.