Characterization of molten salt doped with different size nanoparticles of Al ₂ O ₃

Abstract

Summary This paper aims to study the effect on the characteristics of molten salt because of the dispersion of different size nanoparticles of Al2O3. The eutectic mixture of 54 wt% KNO3 and 46 wt% NaNO3 was selected as the base salt. Five different size nanoparticles of Al2O3, 80, 135, 200, 300, and 1000 nm, were dispersed into the base salt at a mass concentration of 1% to make the nanomaterials by a two‐step method, respectively. Thermal properties of the base salt and the samples with Al2O3 nanoparticles, including the melting point temperature, fusion heat, specific heat capacity, and thermal diffusivity, were measured with differential scanning calorimeter (DSC) and Xenon Flash Apparatus (XFA). On the basis of the measured specific heat capacities and thermal diffusivities, their thermal conductivities in the solid state were calculated at discrete specified temperatures. The results showed that the dispersions of 200‐ and 135‐nm Al2O3 nanoparticles could enhance the average solid and liquid specific heat capacities by up to 17.2% and 19.7%, respectively. The research on thermal diffusivity and thermal conductivity also verified that the influences of different size nanoparticles were different. Although no new strong intensity peaks or peak position variations were found in the diffraction patterns of the two samples with 80‐ and 1000‐nm nanoparticles of Al2O3, the larger deviations in the lower wavenumber region still meant possible crystalline structure variation because of the dispersion of Al2O3 nanoparticles. Scanning electronic microscope (SEM) images showed the inhomogeneity and the agglomeration of dispersed nanoparticles in the base salt, and the formation of a nanolayer around the nanoparticles could be a possible explanation to the thermal‐physical property variation.

Study on the microstructures and thermal properties of SiO 2 @ NaNO 3 microcapsule thermal storage materials

“…It was worth mentioning that the T peak of SiO 2 @NaNO 3 microcapsules in the decomposition decreased slightly with the increase of the silica addition, which was due to the increase of thermal conductivity. Furthermore, the residual amount of sodium nitrate was 28%, and the residual amount of the M‐1 sample was up to 45% after the second decomposition, which was due to the protection of silica shell in preventing decomposition of NaNO 3 42,43 . During the preparation process of pure SiO 2 , the incomplete condensation reaction results in a large amount of precursor remaining in the reaction system.…”

“…Furthermore, the residual amount of sodium nitrate was 28%, and the residual amount of the M-1 sample was up to 45% after the second decomposition, which was due to the protection of silica shell in preventing decomposition of NaNO 3 . 42,43 During the preparation process of pure SiO 2 , the incomplete condensation reaction results in a large amount of precursor remaining in the reaction system. Therefore, the pure silica has a gradual mass loss for the decomposition of raw materials during the thermal decomposition process.…”

Medium- and high-temperature latent and thermochemical heat storage using metals and metallic compounds as heat storage media: A technical review

“…Saranprabhu et al [58] added MgO nanoparticles to Solar Salt and obtained the highest thermal conductivity enhancement of 17.5% with 0.25 wt% MgO, which might be resulted from the reduced thermal resistance caused by the clustered nature of MgO nanoparticles. Han et al [59] studied the effect of Al2O3 nanoparticle sizes on the thermophysical properties of Solar Salt. Thermal conductivity increased for all nanoparticles sizes at 413 K and 433 K, but increased only for 300-nm and 1000-nm nanoparticles at 453 K. Zhang et al [60] measured the thermal conductivities of a ternary carbonate improved by three nano-Al2O3 samples at 298 K and found thermal conductivity was improved by 23.3%, 28.5% and 30.9%, respectively.…”

Thermophysical investigation of metallic nanocomposite phase change materials for indoor thermal management

“…But sodium salts showed maximum improvement in decomposition temperature. A eutectic mixture consisting of KNO 3 and NaNO 3 with 1 wt% of Al 2 O 3 nanoparticles at different sizes such as 80, 135, 200, 300, and 1000 nm were characterized by Han et al 22 From their results, it was evidenced that 300 nm Al 2 O 3 was optimal for liquid specific heat improvement at 235°C to 300°C. Santosh et al 23 compared surface roughened PCM and Al 2 O 3 nano‐dispersed PCM by analyzing their thermal performance and presented their results.…”