M.S. (Master of Science)
Department of Mechanical Engineering
In this investigation, a nanocapsule composed of a sodium nitrate core and a silicon dioxide shell is synthesized, characterized, and analyzed utilizing a mixture of analytical and computational tools. The sol-gel method was selected as the process of nanoencapsulation. Analytical characterization techniques employed in this investigation include differential scanning calorimetry (DSC) to measure melting temperatures and enthalpies of fusion, dynamic light scattering (DLS) to calculate particle size distributions, scanning electron microscopy (SEM) to analyze surface characteristics, transmission electron microscopy (TEM) to perform shell characterization, and energy dispersive X-ray spectroscopy (EDS) to determine chemical composition. Preliminary results indicated a decrease in both the enthalpies of fusion and crystallization for the encapsulated sodium nitrate when compared to its non-encapsulated form. While these results indicate the possibility of the encapsulation, corresponding SEM and TEM results indicate otherwise. To further investigate this contradiction, molecular dynamics simulations on the LAMMPS software package is used to evaluate the thermal energy storage characteristics of this nano encapsulated phase change material. The NaNO3 structure was validated using Buckingham potential, the SiO2 structure was validated using BKS potential, and LJ potential was used to represent the interaction between these two materials. The melting point, latent heat of fusion, and radial distribution function of sodium nitrate encapsulated by silicon dioxide are simulated using the above three different force field models. These computational results are analyzed and compared with experimental observations of the laboratory synthesized nano encapsulated sodium nitrate nanostructures. These analytical and computational analyses will then be related to increasing the energy density of the thermal energy storage fluid for concentrated solar power plant applications.
Hashimoto, Wataru, "Experimental and Computational Characterization of Sodium Nitrate @ Silica Nano Capsules For Thermal Energy Storage Applications" (2020). Graduate Research Theses & Dissertations. 7097.
Northern Illinois University
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