Results 171 to 180 of about 4,430 (207)

Thermal transformations of vaterite and calcite

Thermochimica Acta, 1994
Abstract The polymorphic transition and the thermal decomposition of vaterite are characterized. The effect of the morphology of the parent vaterite upon the polymorphic transition as well as upon the decomposition of pseudomorphous ex-vaterite, i.e. “spherulitic” calcite, is presented.
Maciejewski, Marek, Oswald, Hans-Rudolf, Reller, Armin   +2 more
openaire   +1 more source

Polarized light through polycrystalline vaterite helicoids

Chemical Communications, 2020
Chiral, polycrystalline vaterite helicoids imaged by complete Mueller matrix polarimetry and simulated on the basis of the superstructure of anisotropic lamellae.
Melissa Tan, Wenge Jiang, Alexander T. Martin, Alexander G. Shtukenberg, Marc D. McKee, Bart Kahr   +5 more
openaire   +2 more sources

Bacterially mediated mineralization of vaterite

Geochimica et Cosmochimica Acta, 2007
Myxococcus xanthus, a common soil bacterium, plays an active role in the formation of spheroidal vaterite. Bacterial production of CO2 and NH3 and the transformation of the NH3 to NH4+ and OH−, thus increasing solution pH and carbonate alkalinity, set the physicochemical conditions (high supersaturation) leading to vaterite precipitation in the ...
Carlos Rodriguez-Navarro, Concepcion Jimenez-Lopez, Alejandro Rodriguez-Navarro, Maria Teresa Gonzalez-Muñoz, Manuel Rodriguez-Gallego   +4 more
openaire   +1 more source

Effects of Trace Lanthanum Ion on the Stability of Vaterite and Transformation from Vaterite to Calcite in an Aquatic System

Bulletin of the Chemical Society of Japan, 2001
Abstract The effect of lanthanum ion on the crystallization of calcium carbonate was investigated using CaCl2–NaHCO3 solutions. A sampling vessel enabling us to sample a small aliquot of a solution at any time almost under a closed condition was invented for the experiments.
Hiroshi Tsuno, Hiroyuki Kagi, Tasuku Akagi   +2 more
openaire   +1 more source

Struktur und Fehlordnung des Vaterits*

Zeitschrift für Kristallographie, 1969
Single-crystal photographs of vaterite (/1 CaC03) show numerous diffuse streaks II e* with maxima which require an increase in the previous lattice parameter a by a factor -y3 to 7.15 A, and doubling (sometimes trebling) of e to 16.94 A; moreover satellite reflections were observed.
openaire   +1 more source

Influence on the Formation of Aragonite or Vaterite by Otolith Macromolecules

European Journal of Inorganic Chemistry, 2004
Abstract Calcium carbonate polymorphism is one of the most challenging problems in biomineralization. Calcium carbonate exists in three crystalline forms: calcite, aragonite and vaterite. Otoliths of teleost fishes are made of vaterite and aragonite, located in different sacs and never mixed together. This paper presents a biochemical
FALINI, GIUSEPPE, FERMANI, SIMONA, VANZO SILVIA, MILETIC MARIN, ZAFFINO GIULIA   +4 more
openaire   +2 more sources

Gallstone of Unusual Composition: Calcite, Aragonite, and Vaterite

Science, 1968
A gallstone of almost perfect octahedral symmetry was composed of a mixture of crystallites of the three polymorphous forms of calcium carbonate: calcite, aragonite, and vaterite.
D J, Sutor, S E, Wooley
openaire   +2 more sources

Raman Spectra of Vateritic Calcium Carbonate

Spectroscopy Letters, 1995
Abstract The Raman spectrum of polycrystalline vaterite is presented and compared to spectra of calcite and aragonite, the other two common CaCO3 polymorphs; Raman spectroscopy easily distinguishes between these three polymorphs. An important feature of the Raman spectrum of vaterite is splitting of both the ν1 and ν4 peaks.
Gesa Behrens, Liisa T. Kuhn, Rick Ubic, Arthur H. Heuer   +3 more
openaire   +1 more source

Sonosynthesis of Vaterite-Type Calcium Carbonate

Crystal Growth & Design, 2017
Metastable nanoparticles of vaterite were formed using a simple ultrasound technique. The effects of ultrasound amplitude and duration, as well as solution concentration, were investigated. The produced particles were characterized using standard X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning and transmission ...
Judith A. Juhasz-Bortuzzo, Barbara Myszka, Raquel Silva, Aldo R. Boccaccini   +3 more
openaire   +1 more source

Crystallization and transformation of vaterite at controlled pH

Journal of Crystal Growth, 2006
Abstract Precipitated calcium carbonate particles were prepared by passing CO 2 /N 2 mixed gases into CaCl 2 solution. The nucleation, crystallization and transformation of vaterite at controlled pH were investigated in this paper. The control of pH was conducted by the addition of ammonia.
Yong Sheng Han, Gunawan Hadiko, Masayoshi Fuji, Minoru Takahashi   +3 more
openaire   +1 more source