Interplay between Thermally Induced Aragonite–Calcite Transformation and Multistep Dehydration in a Seawater Spiral Shell (Euplica scripta)

While heating a seawater spiral shell (Euplica scripta), thermally induced aragonite–calcite (A–C) transformation occurred within the temperature region of multistep thermal dehydration. Here, the kinetic interplay between the A–C transformation and thermal dehydration was studied as a possible caus...

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Bibliographic Details
Published in:Processes 2023-06, Vol.11 (6), p.1650
Main Authors: Tone, Taiga, Koga, Nobuyoshi
Format: Article
Language:English
Subjects:
Analysis
Aragonite
Calcite
Calcite crystals
Carbonates
Decomposition
Dehydration
Differential thermal analysis
Fourier transforms
Heat
Infrared spectroscopy
Kinetics
Mass spectrometry
Mass spectroscopy
Mineralization
Powders
Reduction
Scanning electron microscopy
Sea-water
Seawater
Spectrum analysis
Temperature
Thermal transformations
Thermogravimetry
Transformation temperature
Water vapor
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Summary:While heating a seawater spiral shell (Euplica scripta), thermally induced aragonite–calcite (A–C) transformation occurred within the temperature region of multistep thermal dehydration. Here, the kinetic interplay between the A–C transformation and thermal dehydration was studied as a possible cause of the reduction in the A–C transformation temperatures. The kinetics of the A–C transformation was systematically investigated under isothermal conditions by powder X-ray diffractometry and under linear nonisothermal conditions by Fourier transform infrared spectroscopy. The thermal dehydration was characterized as a partially overlapping, three-step process by thermogravimetry–differential thermal analysis coupled with mass spectroscopy for the evolved gases. The A–C transformation occurred in the temperature range of the final part of the second dehydration step and the initial part of the third dehydration step. The kinetics of A–C transformation and thermal dehydration were characterized by contracting geometry-type models, in which the respective transformations were regulated by a constant linear advancement rate and diffusional removal of water vapor, respectively. Based on the kinetic results, the mutual interaction of those thermally induced processes is discussed as a possible cause of the reduction in the A–C transformation temperature.
ISSN:2227-9717
2227-9717
DOI:10.3390/pr11061650