The energetics of nanophase calcite

Forbes, Tori Z.; Radha, A. V.; Navrotsky, Alexandra

doi:10.1016/j.gca.2011.09.034

Cited by 60 publications

(72 citation statements)

References 67 publications

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“…The properties of the nanocalcites (same materials as used in our previous study of surface energy) are listed in Table S1 (29). All samples have highly uniform particle size (65-133 nm).…”

Section: Resultsmentioning

confidence: 99%

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Probing the energetics of organic–nanoparticle interactions of ethanol on calcite

Navrotsky

2015

Proc. Natl. Acad. Sci. U.S.A.

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Knowing the nature of interactions between small organic molecules and surfaces of nanoparticles (NP) is crucial for fundamental understanding of natural phenomena and engineering processes. Herein, we report direct adsorption enthalpy measurement of ethanol on a series of calcite nanocrystals, with the aim of mimicking organic-NP interactions in various environments. The energetics suggests a spectrum of adsorption events as a function of coverage: strongest initial chemisorption on active sites on fresh calcite surfaces, followed by major chemical binding to form an ethanol monolayer and, subsequently, very weak, near-zero energy, physisorption. These thermochemical observations directly support a structure where the ethanol monolayer is bonded to the calcite surface through its polar hydroxyl group, leaving the hydrophobic ends of the ethanol molecules to interact only weakly with the next layer of adsorbing ethanol and resulting in a spatial gap with low ethanol density between the monolayer and subsequent added ethanol molecules, as predicted by molecular dynamics and density functional calculations. Such an ordered assembly of ethanol on calcite NP is analogous to, although less strongly bonded than, a capping layer of organics intentionally introduced during NP synthesis, and suggests a continuous variation of surface structure depending on molecular chemistry, ranging from largely disordered surface layers to ordered layers that nevertheless are mobile and can rearrange or be displaced by other molecules to strongly bonded immobile organic capping layers. These differences in surface structure will affect chemical reactions, including the further nucleation and growth of nanocrystals on organic ligand-capped surfaces.thermodynamics | adsorption calorimetry | ligand-capped nanocrystal | biomineralization | carbonate formation

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“…The properties of the nanocalcites (same materials as used in our previous study of surface energy) are listed in Table S1 (29). All samples have highly uniform particle size (65-133 nm).…”

Section: Resultsmentioning

confidence: 99%

“…Four high-quality commercial nanocalcite samples, characterized and used previously in a study of calcite surface energy (29), were used as adsorbents (Table S1). The details of direct gas adsorption calorimetry experiments are described in Materials and Methods.…”

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confidence: 99%

Probing the energetics of organic–nanoparticle interactions of ethanol on calcite

Navrotsky

2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The research carried out by Yue et al [1] showed a downward shift in the decomposition temperature (*50°C) for nanophase compared to the normal size of calcite. In another TG analysis [38], the shift of temperature was not seen and no Aggregate size and aggregation time…”

Section: Thermal Analysis Of Calcitementioning

confidence: 95%

“…The effect of calcite particle size on the decomposition parameters was studied before [1,38,39]. The research carried out by Yue et al [1] showed a downward shift in the decomposition temperature (*50°C) for nanophase compared to the normal size of calcite.…”

Section: Thermal Analysis Of Calcitementioning

confidence: 99%

Simulation, aggregation and thermal analysis of nanostructured calcite obtained in a controlled multiphase process

Wszelaka‐Rylik

Piotrowska

Gierycz

2014

J Therm Anal Calorim

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In the present experiments, the carbonation process in multiphase system was carried out using the reactor with rotating discs. Calcite was produced by controlled fast precipitation through gaseous CO 2 adsorption in Ca(OH) 2 slurry. Furthermore, the reaction kinetics' were controlled by disc's revolution speed in the range from 80 rpm through 120 to 160 rpm. Initial concentration of the slurry ranged between 54 and 110 mM L -1 . The aggregates of crystals precipitated in the aqueous solution were of sub-micrometric size. Dynamic light scattering method showed that mean aggregate diameter decreased with the higher mixing rate as long as the mixing condition was homogenous (up to 160 rpm). Thermogravimetric analysis revealed that the surface of calcite was polluted by unwanted, different compounds amount of which depends on the initial concentration of the slurry. Therefore, in order to obtain chemically pure calcite, CaCO 3 powder was heated up in the laboratory oven. In order to explain the mechanism of calcite particles' aggregation, the simulation of the aggregates formation has been performed based on the new model taking into account kinetics of the multiphase reaction, crystal growth and their agglomeration. The obtained data on crystal morphology during the precipitation process have been compared with the model simulation results. The internally consistent model very well describes both the formation and the aggregation of the calcite nanoparticles, and the same can be used and recommended for accurate calculations of the particle and aggregates' sizes as well as their distribution in the reactor.

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“…The conditions and mechanisms of the formation of secondary phases in veins associated with primary phases remain largely unknown due to their small, often nanoscale size. The mineralogical complexity of such small-scale systems complicates the accurate modeling of elemental behavior due to largely unknown thermodynamic properties (e.g., Navrotsky, 2004;Forbes et al, 2011), which is one of the main concerns of the safe storage of hazardous wastes.…”

Section: Introductionmentioning

confidence: 99%

Role of vein-phases in nanoscale sequestration of U, Nb, Ti, and Pb during the alteration of pyrochlore

Deditius

Smith

Utsunomiya

et al. 2015

Geochimica et Cosmochimica Acta

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The energetics of nanophase calcite

Cited by 60 publications

References 67 publications

Probing the energetics of organic–nanoparticle interactions of ethanol on calcite

Probing the energetics of organic–nanoparticle interactions of ethanol on calcite

Simulation, aggregation and thermal analysis of nanostructured calcite obtained in a controlled multiphase process

Role of vein-phases in nanoscale sequestration of U, Nb, Ti, and Pb during the alteration of pyrochlore

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