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Title: Melting Temperature Depression and Phase Transitions of Nitrate-Based Molten Salts in Nanoconfinement
Authors: Yazlak, Mustafa Goekturk
Khan, Qaiser Ali
Steinhart, Martin
Duran, Hatice
Keywords: Thermal-Conductivity
Thermophysical Properties
Porous Alumina
Issue Date: 2022
Publisher: Amer Chemical Soc
Abstract: Hybrids of nitrate-based molten salts (KNO3, NaNO3, and Solar Salt) and anodic aluminum oxide (AAO) with various pore sizes (between 25 and 380 nm) were designed for concentrated solar power (CSP) plants to achieve low melting point (< 200 degrees C) and high thermal conductivity (> 1 W m(-1) K-1). AAO pore surfaces were passivated with octadecyl phosphonic acid (ODPA), and the results were compared with as-anodized AAO. The change in phase transition temperatures and melting temperatures of salts was investigated as a function of pore diameter. Melting temperatures decreased for all salts inside AAO with different pore sizes while the highest melting temperature decrease (delta T = 173 +/- 2 degrees C) was observed for KNO3 filled in AAO with a pore diameter of 380 nm. Another nanoconfinement effect was observed in the crystal phases of the salts. The ferroelectric phase of KNO3 (gamma-phase) formed at room temperature for KNO3/ AAO hybrids with pore size larger than 35 nm. Thermal conductivity values of molten salt (MS)/AAO hybrids were obtained by thermal property analysis (TPS) at room temperature and above melting temperatures of the salts. The highest increase in thermal conductivity was observed as 73% for KNO3/AAO-35 nm. For NaNO3/AAO-380 nm hybrids, the thermal conductivity coefficient was 1.224 +/- 0.019 at room temperature. To determine the capacity and efficiency of MS/AAO hybrids during the heat transfer process, the energy storage density per unit volume (J m(-3)) was calculated. The highest energy storage capacity was calculated as 2390 MJ m(-3) for KNO3/AAO with a pore diameter of 400 nm. This value is approximately five times higher than that of bulk salt.
Description: Article; Early Access
ISSN: 2470-1343
Appears in Collections:Malzeme Bilimi ve Nanoteknoloji Mühendisliği Bölümü / Department of Material Science & Nanotechnology Engineering
PubMed İndeksli Yayınlar Koleksiyonu / PubMed Indexed Publications Collection
Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection

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