Effect of modified carbon and silicon carbide nanoparticles on light absorption and transmittance properties of Glauber's salt phase change materials
Objective The carbon nanoparticles and the silicon carbide nanoparticles are chemically and physically modified,respectively.These modified hydrophilic nanoparticles are incorporated into mirabilite-based phase transition materials to create composite phase-change materials.A systematic design is adopted to vary the concentration of these modified nanoparticles within traditional mirabilite-based phase change materials.The objective is to enhance the absorbance properties of the resulting composite materials across different wavelength bands.This strategic improvement in absorbance is anticipated to play a crucial role in enhancing the efficiency of solar energy photothermal conversion for mirabilite-based phase change energy storage materials.Methods In this paper,a multi-step approach was undertaken to modify nanoparticles for subsequent integration into phase-change materials.Firstly,a mixed acid solution was created by combining concentrated sulfuric acid and concentrated nitric acid.This acid was then mixed with the nanocarbon powder,and the mixture was centrifuged and dried several times after heating and reaction to produce the modified nanocarbon powder.Secondly,silicon carbide nanoparticles,along with polyvinylpyrrolidone and tetramethylammonium hydroxide were mixed and ball-milled.Subsequently,the modified silicon carbide nanoparticles were obtained by centrifugal drying.Thirdly,a mixture of Na2 SO4·10H2 O and Na2 HPO4·12H2 O in a mass ratio of 2:8 was dissolved in a water bath at 50℃for 45 min,then the modified carbon and silicon carbide nanoparticles were added with different mass fractions and homogeneously dispersed in the phase-change material by ultrasonication.Finally,absorbance and transmittance characteristics were assessed using a UH4150 spectrophotometer.Results and Discussion The dispersion stability of these nanoparticles is meticulously examined using the sheath flow method image instrument.Notably,the modified carbon and silicon carbide nanoparticles exhibit no significant alterations in their mor-phology or structure.Importantly,no signs of agglomeration is detected,which indicates their excellent dispersion characteristics in both water and mirabilite-based phase change materials.Moreover,static observations conducted over a 7 d period at both 50℃and room temperature demonstrate that these modified nanoparticles maintain their stability within the mirabilite-based phase change material.No instances of nanoparticle delamination or agglomeration are observed,underscoring the robust stability of the modified nanoparticles within the composite material.The absorbance and transmittance properties of the phase change materials are analysed by integral reflectometry.The results reveal that the addition of modified carbon powder(at concentrations of 0.1％,0.5％,and 1.0％),leading to a notable increase in average absorbance in the UV light spectrum,ranging from 20％to 35％.Conversely,there is a reduction in average transmittance for visible light,which decreases by 26％to 35％.Additionally,transmittance in the infrared light range(from 800 to 1 500 nm)decrease by 10％to 42％.Similarly,the incorporation of modi-fied silicon carbide nanoparticles(at concentrations of 0.1％,0.5％,and 1.0％)lead to an increase in average absorbance in the UV light spectrum by 22％to 26.6％.Conversely,average transmittance for visible light decreased by 20％to 29％.Further-more,there is an increase in transmittance in the infrared light range(from 1 500 to 2 700 nm)by 8％to 29％.These findings collectively demonstrate that the addition of modified carbon and silicon carbide nanoparticles results in significant alterations in the absorbance and transmittance properties of the mirabilite-based phase change materials,particularly across different wave-length ranges.Conclusion 1)The morphology and structure of the modified nanocarbon powder and nanosilicon carbide remain unchanged,with approximately 95％of the particles in both aqueous and mirabilite-based composite salt systems falling within size range of 0.2 to 4 nm.This observation indicates that the modified nanocarbon powder and nano silicon carbide exhibit excellent dispersibility.2)Under static observation and in comparison with unmodified nanoparticles,the modified nanocarbon powder and nano silicon carbide within the solid-liquid system of the mirabilite-based phase change material displays no significant signs of agglomeration.Additionally,the crystalline mirabilite composite phase change material does not exhibit pronounced delamination.3)The intro-duction of carbon nanoparticles results in an improvement in the average absorbance of the mirabilite phase change composites in the ultraviolet light range(from 200 to 400 nm),simultaneously reducing transmittance in the visible light range(from 400 to 780 nm)and the infrared light range(from 800 to 1 500 nm).This suggests that the inclusion of carbon nanoparticles enhances the light absorption efficiency of the manganese phase change material.4)The average absorbance of mirabilite phase change composites incorporating silicon carbide nanoparticles notably increases by 22％to 26.6％within the ultraviolet light spectrum(from 200 to 400 nm).Conversely,the average transmittance in the visible light range(from 400 to 780 nm)decreases,while transmittance within the infrared light range(from 1 500 to 2 700 nm)increases.
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