Uncertainty in the Study of Comparative Perception: A Methodological Challenge

Stebbins, William C.

doi:10.1007/978-3-0348-7463-2_28

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“…The aim of this contribution is to present new results obtained by a multinuclear ( 19 F, 27 Al, and 23 Na) NMR study of the high-temperature liquids of the NaF−AlF 3 binary systems and to discuss the mechanism of dissolution of alumina (Al 2 O 3 ) in cryolite-based liquids from the observation of 17 O. Due to its high polarizability 17 O has a large range of chemical shifts and is thus very sensitive to the structure of its local environment in crystalline, amorphous, or liquid materials. − Its observability is limited only by its very low intrinsic sensitivity due to low natural abundance (0.037%) that can be circumvented by isotopic enrichment. The combination of information obtained from the observation by NMR of all the different nuclei present in these high-temperature melts enables us to discuss previously proposed models of the liquid structure and to give the first experimental evidence of the presence of at least two oxyfluoride species upon dissolution of alumina.…”

Section: Introductionmentioning

confidence: 99%

Structure of High-Temperature NaF−AlF₃−Al₂O₃ Melts: A Multinuclear NMR Study

et al. 2002

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Fluoroaluminate molten salts are used in the Hall-Heroult industrial process for the production of aluminum by electrolysis. To better understand the mechanism of the dissolution of alumina (Al 2 O 3 ) in cryolitic melts, we have studied the structure of these liquids up to 1025 °C by in-situ NMR of 27 Al, 23 Na, 19 F, and 17 O, using a laser-heated experimental setup. From these experiments we can propose a quantification of the different aluminum-bearing species AlF 4 -, AlF 5 2-, and AlF 6 3in the liquid and give a direct experimental evidence of the existence of at least two different oxy-fluoride species, Al 2 OF 6 2and Al 2 O 2 F 4 2-, when dissolving alumina in the fluoride liquid. The obtained results are compared with other spectroscopic data obtained by in-situ Raman spectroscopy.

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Section: Introductionmentioning

confidence: 99%