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Identification of Superoxide O_2^- during Thermal Decomposition of Molten KNO3-NaNO2-NaNO3 Salt by EPR and UV-VIS Absorption Spectroscopy
liuhongtao
Author NameAffiliationE-mail
liuhongtao none liuhongtao@sinap.ac.cn 
Abstract:
On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in Concentrated Solar Power (CSP) system. The thermal stability study of molten nitrate/nitrite salt is of great importance for this system, and the decomposition mechanism is the most complicated part of it. The oxide species 〖 O〗_2^(2-) and O_2^- were considered as intermediates in molten KNO3-NaNO3 while hard to been detected in high temperature molten salt due to their trace concentration and low stability. In this work, the homemade in situ high temperature UV-VIS instrument and a commercial EPR were utilized to supply evidence for the formation of superoxide during a slowly decomposition process of HTS (53wt.% KNO3- 40wt.% NaNO2-7wt.% NaNO3). It is found that the superoxide is more easily generated from molten NaNO2 compared to NaNO3, and it has an absorption band at 420-440 nm in HTS which red shifts as temperature increases. The band is assigned to charge-transfer transition in NaO2 or KO2, responsible for the yellow color of the molten nitrate/nitrite salt. Furthermore, the UV absorption bands of molten NaNO2 and NaNO3 are also obtained and compared with that of HTS.
Key words:  Superoxide, Decomposition of HTS, High temperature UV-VIS, EPR
FundProject:
Identification of Superoxide O_2^- during Thermal Decomposition of Molten KNO3-NaNO2-NaNO3 Salt by EPR and UV-VIS Absorption Spectroscopy
liuhongtao
摘要:
On account of excellent thermal physical properties, molten nitrates/nitrites salt has been widely employed in heat transfer and thermal storage industry, especially in Concentrated Solar Power (CSP) system. The thermal stability study of molten nitrate/nitrite salt is of great importance for this system, and the decomposition mechanism is the most complicated part of it. The oxide species 〖 O〗_2^(2-) and O_2^- were considered as intermediates in molten KNO3-NaNO3 while hard to been detected in high temperature molten salt due to their trace concentration and low stability. In this work, the homemade in situ high temperature UV-VIS instrument and a commercial EPR were utilized to supply evidence for the formation of superoxide during a slowly decomposition process of HTS (53wt.% KNO3- 40wt.% NaNO2-7wt.% NaNO3). It is found that the superoxide is more easily generated from molten NaNO2 compared to NaNO3, and it has an absorption band at 420-440 nm in HTS which red shifts as temperature increases. The band is assigned to charge-transfer transition in NaO2 or KO2, responsible for the yellow color of the molten nitrate/nitrite salt. Furthermore, the UV absorption bands of molten NaNO2 and NaNO3 are also obtained and compared with that of HTS.
关键词:  Superoxide, Decomposition of HTS, High temperature UV-VIS, EPR
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