Thermal Expansion of Synthetic Aragonite Condensed Review of Elastic Properties

Lucas, Anita; Mouallem-Bahout, M.; Carel, C.; Gaude, J.; Matecki, M.

doi:10.1006/jssc.1999.8310

Cited by 41 publications

(37 citation statements)

References 24 publications

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“…The unit-cell parameters for the isostructural carbonates are in excellent agreement with those obtained previously (e.g., De Villiers 1971, Jarosch & Heger 1986, 1988, Lucas et al 1999, Holl et al 2000. However, cell parameters obtained in this study are significantly more accurate, as they were obtained from HRPXRD data (Table 2a).…”

Section: Linear Structural Trendssupporting

confidence: 90%

THE ORTHORHOMBIC STRUCTURE OF CaCO3, SrCO3, PbCO3 AND BaCO3: LINEAR STRUCTURAL TRENDS

Antao

Hassan

2009

The Canadian Mineralogist

147

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The crystal structures of four isostructural orthorhombic carbonates, CaCO 3 (aragonite), SrCO 3 (strontianite), PbCO 3 (cerussite), and BaCO 3 (witherite), were obtained by Rietveld refinements using data acquired by synchrotron high-resolution powder X-ray diffraction (HRPXRD). For BaCO 3 , powder neutron-diffraction data were obtained and refined by the Rietveld method. For aragonite, we also carried out a refinement of the structure by single-crystal X-ray diffraction. These carbonates belong to the space group Pmcn, with Z = 4. The CO 3 group is slightly non-planar, and the two independent C-O distances are slightly different. The CO 3 group becomes more symmetrical and less aplanar from CaCO 3 to BaCO 3 (M 2+ radii : Ca < Sr < Pb < Ba). The CaCO 3 structure is, therefore, the most distorted, whereas the BaCO 3 structure is the least distorted. Several linear structural trends are observed in plots of selected parameters as a function of the unit-cell volume, V. These parameters are radii of the nine-coordinated M 2+ cations, the unit-cell axes, the average and distances, average angle, and aplanarity. These linear trends are the result of the effective size of the divalent ionic radius of the M cations that are coordinated to nine oxygen atoms. The geometrical features of the CO 3 group can be obtained reliably only by using neutron-diffraction data, especially in the presence of other heavy atoms.Keywords: CaCO 3 , aragonite, SrCO 3 , strontianite, PbCO 3 , cerussite, BaCO 3 , witherite, Rietveld refinements, synchrotron highresolution powder X-ray diffraction (HRPXRD), neutron diffraction, crystal structure. SOMMAIreNous avons affiné la structure cristalline de quatre carbonates orthorhombiques isostructuraux, CaCO 3 (aragonite), SrCO 3 (strontianite), PbCO 3 (cérusite), et BaCO 3 (witherite), par la méthode de Rietveld en utilisant les données acquises par diffraction X à haute résolution avec rayonnement synchrotron. Pour le BaCO 3 , nous avons utilisé des données obtenues par diffraction neutronique, aussi affinées par la méthode de Rietveld. Pour l'aragonite, nous avons affiné la structure par diffraction X sur monocristal. Ces carbonates répondent au groupe spatial Pmcn, avec Z = 4. Le groupe CO 3 est légèrement non planaire, et les deux distances C-O indépendantes diffèrent légèrement. Le groupe CO 3 devient plus symétrique et moins aplanaire en allant de CaCO 3 à BaCO 3 (M 2+ rayon : Ca < Sr < Pb < Ba). La structure de CaCO 3 serait donc la plus difforme, tandis que la structure de BaCO 3 serait la moins difforme. Plusieurs tendances structurales sont évidentes dans les tracés de paramètres choisis en fonction du volume de la maille élémentaire, V. Parmi ces paramètres sont le rayon des cations M 2+ à coordinence neuf, les dimensions le long des axes de la maille élémentaire, les distances et moyennes, l'angle moyen, et l'aplanarité. Ces tracés linéaires sont le résultat de la dimension effective du rayon ionique du cation M bivalent coordonné aux ne...

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Section: Linear Structural Trendssupporting

confidence: 90%

THE ORTHORHOMBIC STRUCTURE OF CaCO3, SrCO3, PbCO3 AND BaCO3: LINEAR STRUCTURAL TRENDS

Antao

Hassan

2009

The Canadian Mineralogist

147

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“…Lucas et al 43 used in situ XRD to study the effects of heating on CaCO 3 . They were able to show a phase change from aragonite to calcite at a temperature of 450˚C.…”

Section: Introductionmentioning

confidence: 99%

In situ X-ray diffraction of CaO based CO2 sorbents

Molinder

Comyn

Hondow

et al. 2012

Energy Environ. Sci.

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In situ X-ray diffraction coupled with Rietveld refinement has been used to study CO 2 capture by CaO, Ca(OH) 2 and partially hydrated CaO, as a function of temperature. Phase quantification by Rietveld refinement was performed to monitor the conversion to CaCO 3 and the results were compared to those derived using thermogravimetric analysis (TGA). It was found that Ca(OH) 2 converted directly to 100% CaCO 3 without the formation of a CaO intermediate, at ca. 600˚C. Both pure CaO and partially hydrated CaO (33.6 wt% Ca(OH) 2 ) reached the same capture capacity, containing approximately 65 wt% CaCO 3 at 800˚C. It was possible to provide direct evidence of the capture mechanism. The stresses in the Ca(OH) 2 phase of the partially hydrated CaO were found to be more than 20 times higher than its strength, leading to disintegration and the generation of nano-sized crystallites. The crystallite size determined using diffraction (75×16 nm) was in good agreement with the average crystallite size observed using TEM (of 83×16 nm). Electron diffraction images confirmed coexistence of CaO and Ca(OH) 2 . The analysis provides an explanation of the enhanced capture /disintegration observed in CaO in the presence of steam.Keywords: Rietveld analysis, in-situ X-ray diffraction, CaO, CO 2 capture, hydration, capture mechanism, attrition, regeneration, synchrotron. Graphical abstractIn situ XRD, in conjunction with phase quantification using Rietveld analysis, was used successfully to study CO 2 capture in CaO and Ca(OH) 2 as well as in partially hydrated CaO.The work shows how in situ XRD can be used as a supplemental technique to TGA, by which the mechanism of capture and hydration can be elucidated. IntroductionConcerns about global warming have prompted both national and international efforts to curb CO 2 emissions. CaO based materials are being considered as CO 2 sorbents for removal of CO 2 from flue gases at temperatures between 400˚C and 800˚C. Applications include pre-and post-combustion carbon capture technologies. [1][2][3][4][5][6][7][8][9][10] In addition, with the growing replacement of fossil fuels by biomass sources, and due to the high oxygen content of biomass, many of the processes of thermochemical fuel upgrading generate significant CO 2 at medium-high temperatures. [11][12] This provides the opportunity for in situ CO 2 capture in the 400-800˚C range and for improved heat transfer arising from the coupling of the endothermic gasification reactions with the exothermicity of the CO 2 chemisorption. This results in lower reaction temperatures and lower fuel consumption. [13][14] The advantages of CaO based materials as CO 2 sorbents for pre-and post-combustion CO 2 capture are their low cost, high abundance, large sorption capacity and fast reaction kinetics. 15-17 However, a major shortcoming of CaO based materials as CO 2 sorbents is the degradation in sorption capacity after multiple capture and regeneration cycles, due to loss of surface area through sintering. 18-21 For large scale CO 2 capture, th...

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“…Below 160°C, the crystal type of calcium carbonate remained unchanged and the organic matters in shell were fully decomposed [27]. Below 400°C, the aragonite in shell could completely change to calcite and the calcium carbonate remained nonthermally decomposed [26]. Fig.…”

Section: Effects Of Heat Treatment Of MMmentioning

confidence: 99%

“…The aragonite and calcite have the irreversible change at specific temperature [26]; thus, in this paper, various heat treatment methods were used to control the crystal type of calcium carbonate of MM to study the effect of the crystal type of calcium carbonate on the crystallization behavior of PP. Three temperatures of 160, 360, and 400°C were used to thermally treat MM.…”

Section: Effects Of Heat Treatment Of MMmentioning

confidence: 99%