The University of Southampton
University of Southampton Institutional Repository

Raman mapping in the elucidation of solid salt eutectic and near eutectic structures

Raman mapping in the elucidation of solid salt eutectic and near eutectic structures
Raman mapping in the elucidation of solid salt eutectic and near eutectic structures
The distribution of the different components of solidified eutectic or near-eutectic salt mixtures (eutectics) was examined by use of Raman microscope mapping of the structures formed when these melts were slowly cooled. Seven binary and one ternary system were investigated. In most cases the component crystallized phases consisted of roughly rounded areas of about 0.5-5 µm across, the areas alternating in all directions across the sections. These three-dimensional structures may best be described by the term conglomerate. The size of these areas depended on the cooling rate and the composition. When unidirectional cooling was applied it was possible for the system (KCl-Na2SO4, 60 : 40 mol/mol) to observe lamellar arrangements of the component phases, in an arrangement closely similar to what is frequently found among metallic or ceramic eutectics. Each area, conglomerate or lamellar, did not consist of a pure chemical component, although having one component in a high concentration. Probably the behaviour represents separation on solidification due to the limiting solid solubility. The conglomerate structures are very different from what has been found for metallic or ceramic eutectics. Small changes in composition, in sectioning direction and in solidification technique were found to result in relatively small differences. The major effect was found to result from the rate of solidification, faster cooling causing markedly smaller rounded areas with the conglomerate becoming much finer grained. The high area of interphasial contact between the solid solutions is considered to be responsible for the unexpectedly high electrical conductivity previously found and to give rise to part of the melting enthalpy differences between those of solidified salt eutectics and those of the corresponding unmelted mechanical mixtures of the component salts. Mixtures with a larger variation away from the eutectic composition also showed a conglomerate structure, but with bigger and more irregular areas.
1097-4555
165-172
Berg, Rolf W.
0a1a01bc-5e7a-442d-8c78-b8791cdfcb84
Kerridge, David H.
8ac6422a-c915-41e0-b573-33311cafb21a
Berg, Rolf W.
0a1a01bc-5e7a-442d-8c78-b8791cdfcb84
Kerridge, David H.
8ac6422a-c915-41e0-b573-33311cafb21a

Berg, Rolf W. and Kerridge, David H. (2002) Raman mapping in the elucidation of solid salt eutectic and near eutectic structures. Journal of Raman Spectroscopy, 33 (3), 165-172. (doi:10.1002/jrs.814).

Record type: Article

Abstract

The distribution of the different components of solidified eutectic or near-eutectic salt mixtures (eutectics) was examined by use of Raman microscope mapping of the structures formed when these melts were slowly cooled. Seven binary and one ternary system were investigated. In most cases the component crystallized phases consisted of roughly rounded areas of about 0.5-5 µm across, the areas alternating in all directions across the sections. These three-dimensional structures may best be described by the term conglomerate. The size of these areas depended on the cooling rate and the composition. When unidirectional cooling was applied it was possible for the system (KCl-Na2SO4, 60 : 40 mol/mol) to observe lamellar arrangements of the component phases, in an arrangement closely similar to what is frequently found among metallic or ceramic eutectics. Each area, conglomerate or lamellar, did not consist of a pure chemical component, although having one component in a high concentration. Probably the behaviour represents separation on solidification due to the limiting solid solubility. The conglomerate structures are very different from what has been found for metallic or ceramic eutectics. Small changes in composition, in sectioning direction and in solidification technique were found to result in relatively small differences. The major effect was found to result from the rate of solidification, faster cooling causing markedly smaller rounded areas with the conglomerate becoming much finer grained. The high area of interphasial contact between the solid solutions is considered to be responsible for the unexpectedly high electrical conductivity previously found and to give rise to part of the melting enthalpy differences between those of solidified salt eutectics and those of the corresponding unmelted mechanical mixtures of the component salts. Mixtures with a larger variation away from the eutectic composition also showed a conglomerate structure, but with bigger and more irregular areas.

Full text not available from this repository.

More information

Published date: 2002

Identifiers

Local EPrints ID: 22825
URI: http://eprints.soton.ac.uk/id/eprint/22825
ISSN: 1097-4555
PURE UUID: 58e69ab5-7f73-436e-a7cb-9dea60c67fc2

Catalogue record

Date deposited: 24 Mar 2006
Last modified: 15 Jul 2019 19:21

Export record

Altmetrics

Contributors

Author: Rolf W. Berg
Author: David H. Kerridge

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×