1. FT-NIR and DSC characterisation of water in opal
- Author
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Thomas, P, Chauviré, B, Flower-Donaldson, K, Aldridge, L, Smallwood, A, and Liu, B
- Subjects
03 Chemical Sciences, 09 Engineering, 19 Studies in Creative Arts and Writing ,Materials - Abstract
© 2020 Elsevier Ltd and Techna Group S.r.l. Opal is a hydrous silica (Si02.nH2O) formed through a dissolution-precipitation process. The formation process incorporates water into the structure as bound silanol and molecular water. As the water is distributed in a range of states, multiple methods of characterisation are required to identify each state. This study reports the results of temperature dependent FT-NIR and DSC investigation on natural opal samples of the opal-A (amorphous) and opal-CT (poorly crystalline cristobalite with tridymitic stacking faults) types. Significant differences in the melting behaviour of crystallisable water as well as differences in the spectral characteristics of the non-crystallisable molecular water are observed. These differences are ascribed to the different microstructures of the opal types.
- Published
- 2020