Raman salt melts

Raman spectroscopy has also developed into a powerful tool for investigating high-temperature solutions with the aid of this technique, many salt melts were studied. The species AFCl F, AICI3F, AICI2F2, and AICIF3, for instance, were identified in fluoride-containing chloroaluminate melts (Gilbert et al., 1988). 

Inorganic Compounds. The Raman microprobe has been used by Berg and Kerridge (2000) to obtain computer mappings of the structures of salt eutectics solidified from their melts. In contrast to metallic eutectics, which commonly occur... 

Recently Raman spectroscopy has been applied, in combination with other methods, to show that certain characteristic spectral bands can be identified that are characteristic for conformational forms (conformers) of the IL components, and that the associated conformational equilibria might be partly responsible for the salts to have such low melting points. 

Some idea of how Raman spectroscopy works—how light from nonelastic scattering on molecules contains information on the vibratory state of the bonds therein— has been given in Section 2.11. Raman spectroscopy can be used to obtain information on the structure of ions in molten salts, as has been shown in the last three sections. Ha-e, two further molten salt systems that eontain eomplexes and that have been subjected to Raman spectroscopy are described. The first one concerns melts of zinc chloride hydrate. 

Interaction of XeFs AnF4 with Liquid HF. Anhydrous HF (AHF) was melted onto a sample of XeF5 AuF4" contained in a FEP tube. The lemon yellow salt quickly interacted with the liquid AHF to produce an orange-yellow solid. Removal of volatiles provided the latter solid. Raman spectroscopy and an X-ray powder photograph - showed it... 

This new adduct is a bright yellow solid melting at 160 °C 147 148). The Raman spectrum shows lines characteristic of hexafluoroarsenate, and the absence of an Xe—F vibration justifies its formulation as an ionic salt. The parent, FXeOTeF5, is a poorer donor than XeF2 since it is formed by reaction of the salt with XeF2 (Eq. 28). 

Structural studies in fused salts by means of careful and thorough high-temperature measurements of electrical conductivity, density, viscosity, and laser- Raman spectroscopy have been reviewed. Four problem areas are discussed (1) melting mechanisms of ionic compounds with large polyatomic cations, (2) salts as ultra-concentrated electrolyte solutions, (3) structural aspects and Raman spectroscopy, and (4) electrolysis of molten carbonates. The results in these areas are summarized and significant contributions to new experimental techniques for molten-salt studies are discussed.275 The physical properties and structure of molten salts have also been reviewed in terms of operational (hole, free volume, partly disordered crystal) and a priori (intermolecular potential) models.276 Electrochemistry... 

Direct methods for studying the structure of molten salts are X-ray and neutron diffraction analyses, infrared and Raman spectroscopy, NMR (nuclear magnetic resonance) measurement, and also very recently, XAFS (X-ray Absorption Fine Structure) measurement in melts, were developed. Fiowever, the most frequently used direct methods are X-ray and XAFS measurements, Raman spectroscopy, and NMR measurements. Therefore these three methods of direct investigation will be briefly described here. 

Raman spectra of (M, M )F-A1F3 (M, M = Li, Na, K) molten salts at 1293 K have been obtained by Robert and Gilbert (2000). The intensity ratios between the bands that are characteristic of the different complexes, are strongly affected by the M/M ratio, especially when one of the alkaline metal cations is Li+. Its presence, together with another cation seems to produce an increase in the acidity of the melt. The result of the de-convolution of the spectra compares well with vapor pressure data, showing the same kind of deviation. Quantitative modeling has not been possible because there is a lack of thermodynamic data allowing a comparison with spectroscopic results. 

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