In Situ Determination of Speciation and Local Structure of NaCl- SrCl2 and LiF-ZrF4 Molten Salts

• 全文链接
• 请求原文

作   者：

Lynch, Timothy J.;  Birkner, Nancy R.;  Christian, Matthew S.;  Wrubel, Jacob A.;  Schorne-Pinto, Juliano;  Van Veelen, Arjen;  Bargar, John R.;  Besmann, Theodore M.;  Brinkman, Kyle S.;  Chiu, Wilson K. S.; 

作者机构：

Clemson Univ;  Univ Connecticut;  SLAC Natl Accelerator Lab;  Univ South Carolina; 

关键词：

RAMAN-SPECTRA;  FLUOROZIRCONATE GLASSES;  TEMPERATURE EXAFS MEASUREMENTS;  SPECTROSCOPY;  RARE-EARTH;  X-RAY;  CRYSTAL-STRUCTURES;  SYSTEMS;  THERMODYNAMIC ASSESSMENT;  FLUORIDES; 

期刊名称：

The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical

i s s n：

1520-6106

年卷期：

2022 年 126 卷 7 期

页   码：

1539-1550

页   码：

摘   要：

Understanding the local environment of the metal atoms in salt melts is important for modeling the properties of melts and predicting their behavior and thus helping enable the development of technologies such as molten salt reactors and solar-thermal power systems and new approaches to recycling rare-earth metals. Toward that end, we have developed an in situ approach for measuring the coordination of metals in molten salt coupling X-ray absorption spectroscopy (XAS) and Raman spectroscopy. Our approach was demonstrated for two salt mixtures (1.9 and 5 mol % SrCl2 in NaCl, 0.8 and 5 mol % ZrF4 in LiF) at up to 1100 degrees C. Near-edge (X-ray absorption near-edge structure, XANES) and extended X-ray absorption fine structure (EXAFS) spectra were measured. The EXAFS response was modeled using ab initio FEFF calculations. Strontium's first shell is observed to be coordinated with chlorine (Sr2+-Cl-) and zirconium's first shell is coordinated by fluorine (Zr4+-F-), both having coordination numbers that decrease with increasing temperature. Multiple zirconium complexes are believed to be present in the melt, which may interfere and distort the EXAFS spectra and result in an anomalously low zirconium first shell coordination number. The use of boron nitride (BN) powder as a salt diluent for XAFS measurements was found to not interfere with measurements and thus can be used for investigations of such systems.