Ultrasonic observation of the calcite-aragonite transition
نویسندگان
چکیده
منابع مشابه
Direct observation of the transition from calcite to aragonite growth as induced by abalone shell proteins.
The mixture of EDTA-soluble proteins found in abalone nacre are known to cause the nucleation and growth of aragonite on calcite seed crystals in supersaturated solutions of calcium carbonate. Past atomic force microscope studies of the interaction of these proteins with calcite crystals did not observe this transition because no information about the crystal polymorph on the surface was obtain...
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Calcium carbonate (CaCO3) occurs in two major polymorphs: rhombohedral calcite and orthorhombic aragonite, the latter is thermodynamically metastable. In this study, we first prepared aragonite needle-like particles by introducing CO2-containing gas into Ca(OH)2 aqueous slurry. Then, the resulted aragonite particles were heat treated at 500 ◦C for 1 h, in order to induce the aragonite–calcite p...
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[1] Based on measurements from the WOCE/JGOFS global CO2 survey, the CLIVAR/CO2 Repeat Hydrography Program and the Canadian Line P survey, we have observed an average decrease of 0.34% yr 1 in the saturation state of surface seawater in the Pacific Ocean with respect to aragonite and calcite. The upward migrations of the aragonite and calcite saturation horizons, averaging about 1 to 2 m yr , a...
متن کاملThe Raman spectrum of CaCO3 polymorphs calcite and aragonite: a combined experimental and computational study.
Powder and single crystal Raman spectra of the two most common phases of calcium carbonate are calculated with ab initio techniques (using a "hybrid" functional and a Gaussian-type basis set) and measured both at 80 K and room temperature. Frequencies of the Raman modes are in very good agreement between calculations and experiments: the mean absolute deviation at 80 K is 4 and 8 cm(-1) for cal...
متن کاملUnusual micrometric calcite-aragonite interface in the abalone shell Haliotis (Mollusca, Gastropoda).
Species of Haliotis (abalone) show high variety in structure and mineralogy of the shell. One of the European species (Haliotis tuberculata) in particular has an unusual shell structure in which calcite and aragonite coexist at a microscale with small patches of aragonite embedded in larger calcitic zones. A detailed examination of the boundary between calcite and aragonite using analytical mic...
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ژورنال
عنوان ژورنال: Journal of Geophysical Research
سال: 1963
ISSN: 0148-0227
DOI: 10.1029/jz068i002p00529