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Title: Nucleation and Epitaxy-Mediated Phase Transformation of a Precursor Cadmium Carbonate Phase at the Calcite/Water Interface

Abstract

Mineral nucleation can be catalyzed by the presence of mineral substrates; however, the mechanisms of heterogeneous nucleation remain poorly understood. A combination of in situ time-sequenced measurements and nano-manipulation experiments were performed using atomic force microscopy (AFM) to probe the mechanisms of heteroepitaxial nucleation of otavite (CdCO3) on calcite (CaCO3) single crystals that exposed the (10-14) surface. Otavite and calcite are isostructural carbonates that display a 4% lattice mismatch, based on their (10-14) surface areas. AFM observations revealed a two-stage process in the nucleation of cadmium carbonate surface precipitates. As evidenced by changes in height, shape, growth behavior, and friction signal of the precipitates, a precursor phase was observed to initially form on the surface and subsequently undergo an epitaxy-mediated phase transformation to otavite, which then grew epitaxially. Nano-manipulation experiments, in which the applied force was increased progressively until precipitates were removed from the surface, showed that adhesion of the precursor phase to the substrate was distinctively weaker than that of the epitaxial phase, consistent with that of an amorphous phase. These findings demonstrate for the first time that heterogeneous mineral nucleation can follow a non-classical pathway like that found in homogenous aqueous conditions.

Authors:
ORCiD logo; ORCiD logo; ORCiD logo
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1349166
Report Number(s):
PNNL-SA-122339
Journal ID: ISSN 1932-7447; 48389; KC0302060
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry. C; Journal Volume: 121; Journal Issue: 9
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory

Citation Formats

Riechers, Shawn L., Rosso, Kevin M., and Kerisit, Sebastien N. Nucleation and Epitaxy-Mediated Phase Transformation of a Precursor Cadmium Carbonate Phase at the Calcite/Water Interface. United States: N. p., 2017. Web. doi:10.1021/acs.jpcc.6b11727.
Riechers, Shawn L., Rosso, Kevin M., & Kerisit, Sebastien N. Nucleation and Epitaxy-Mediated Phase Transformation of a Precursor Cadmium Carbonate Phase at the Calcite/Water Interface. United States. doi:10.1021/acs.jpcc.6b11727.
Riechers, Shawn L., Rosso, Kevin M., and Kerisit, Sebastien N. Fri . "Nucleation and Epitaxy-Mediated Phase Transformation of a Precursor Cadmium Carbonate Phase at the Calcite/Water Interface". United States. doi:10.1021/acs.jpcc.6b11727.
@article{osti_1349166,
title = {Nucleation and Epitaxy-Mediated Phase Transformation of a Precursor Cadmium Carbonate Phase at the Calcite/Water Interface},
author = {Riechers, Shawn L. and Rosso, Kevin M. and Kerisit, Sebastien N.},
abstractNote = {Mineral nucleation can be catalyzed by the presence of mineral substrates; however, the mechanisms of heterogeneous nucleation remain poorly understood. A combination of in situ time-sequenced measurements and nano-manipulation experiments were performed using atomic force microscopy (AFM) to probe the mechanisms of heteroepitaxial nucleation of otavite (CdCO3) on calcite (CaCO3) single crystals that exposed the (10-14) surface. Otavite and calcite are isostructural carbonates that display a 4% lattice mismatch, based on their (10-14) surface areas. AFM observations revealed a two-stage process in the nucleation of cadmium carbonate surface precipitates. As evidenced by changes in height, shape, growth behavior, and friction signal of the precipitates, a precursor phase was observed to initially form on the surface and subsequently undergo an epitaxy-mediated phase transformation to otavite, which then grew epitaxially. Nano-manipulation experiments, in which the applied force was increased progressively until precipitates were removed from the surface, showed that adhesion of the precursor phase to the substrate was distinctively weaker than that of the epitaxial phase, consistent with that of an amorphous phase. These findings demonstrate for the first time that heterogeneous mineral nucleation can follow a non-classical pathway like that found in homogenous aqueous conditions.},
doi = {10.1021/acs.jpcc.6b11727},
journal = {Journal of Physical Chemistry. C},
number = 9,
volume = 121,
place = {United States},
year = {Fri Feb 24 00:00:00 EST 2017},
month = {Fri Feb 24 00:00:00 EST 2017}
}
  • No abstract prepared.
  • Metastable pseudomorphic Si{sub 0.83}Ge{sub 0.17} with thickness of 135 nm was deposited on (001) Si substrate by molecular beam epitaxy and amorphized to a depth of {approx}360 nm, using 3x10{sup 15} cm{sup -2} Ge ions at 270 keV. Samples were regrown by solid phase epitaxy in the 500-600 degree sign C temperature range. The regrowth rate was measured in situ by time resolved reflectivity, while the structure of the epilayers was investigated by transmission electron microscopy. Three regions can be distinguished in SiGe after solid phase epitaxy, independent of the annealing temperature: (1) a 20 nm defect-free layer close tomore » the original crystal-amorphous interface, (2) a middle region with a high density of planar defects, and (3) a layer with dislocations and stacking faults extending up to the surface. The activation energy of the SiGe solid phase epitaxy is equal to the activation energy of Si except in the middle region. The amorphous-crystal interface evolution was studied by transmission electron microscopy of partially regrown samples. In order to study the effects of dopants, some samples were also implanted with B{sup +} and Sb{sup +} ions. At the ion projected range (125 nm for both implants) the regrowth rate increases by a factor of 3 with respect to the unimplanted SiGe, but the defect-free layer again is found to be about 20 nm in all cases. Moreover, the activation energy of the solid phase epitaxy regrowth process does not depend on dopant introduction, while the only observable effect of B or Sb incorporation is a smoothness of the amorphous-crystal interface during solid phase epitaxy.« less
  • Elucidating the kinetics and mechanisms of heteroepitaxial nucleation and growth at mineral-water interfaces is essential to understanding surface reactivity in geochemical systems. In the present work, the formation of heteroepitaxial cadmium carbonate coatings at calcite-water interfaces was investigated by exposing calcite (10-14) surfaces to Cd-bearing aqueous solutions. In situ atomic force microscopy (AFM) was employed as the primary technique. The AFM results indicate that the heteroepitaxial growth of cadmium carbonate proceeds via three different mechanisms depending on the initial supersaturation of the aqueous solution: advancement of existing steps, nucleation and growth of three-dimensional (3D) islands, and nucleation and spread ofmore » two-dimensional (2D) nuclei. The 3D islands and 2D nuclei exhibit different morphologies and growth kinetics. The effects of supersaturation on heteroepitaxial growth mechanisms can be interpreted in terms of the free energy barrier for nucleation. At low initial supersaturation, where 3D nucleation dominates, it is hypothesized, from the growth rate and morphology of the 3D islands observed with AFM, that the crystallization of the overgrowth follows a non-classical pathway involving the formation of a surface precursor that is not fully crystalline, whereas high supersaturation favors the formation of crystalline 2D nuclei whose morphology is based on the atomic structure of the calcite substrate. Cross-sectional transmission electron microscopy (TEM) images reveal that the atomic structure of the interface between the cadmium carbonate coating and calcite shows perfect, dislocation-free epitaxy.« less
  • The ability of surface precipitates to form heteroepitaxially is an important factor that controls the extent of heterogeneous growth. In this work, the growth of cadmium and cobalt carbonate phases on (10-14) calcite surfaces is compared for a range of initial saturation states with respect to otavite (CdCO3) and sphaerocobaltite (CoCO3), two isostructural metal carbonates that exhibit different lattice misfits with respect to calcite. Calcite single crystals were reacted in static conditions for 16 hours with CdCl2 and CoCl2 aqueous solutions with initial concentrations 0.3 ≤ [Cd2+]0 ≤ 100 μM and 25 ≤ [Co2+]0 ≤ 200 μM. The reacted crystalsmore » were imaged in situ with atomic force microscopy (AFM) and analyzed ex situ with X-ray photoelectron spectroscopy (XPS). AFM images of Cd-reacted crystals showed the formation of large islands elongated along the direction, clear evidence of heteroepitaxial growth, whereas surface precipitates on Co-reacted crystals were small round islands. Deformation of calcite etch pits in both cases indicated the incorporation of Cd and Co at step edges. XPS analysis pointed to the formation of a Cd-rich (Ca,Cd)CO3 solid solution coating atop the calcite substrate. In contrast, XPS measurements of the Co-reacted crystals provided evidence for the formation of a mixed hydroxy-carbonate cobalt phase. The combined AFM and XPS results suggest that the lattice misfit between CoCO3 and CaCO3 ( 15% based on surface areas) is too large to allow for heteroepitaxial growth of a pure cobalt carbonate phase on calcite surfaces in aqueous solutions and at ambient conditions. The use of the satellite structure of the Co 2p3/2 photoelectron line as a tool for determining the nature of cobalt surface precipitates is also discussed.« less
  • Here, the systematic variation of rates and the mechanism of cadmium uptake on the (104) surface of dolomite (CaMg(CO 3) 2) were investigated using in situ and ex situ atomic force microscopy (AFM), ex situ specular X-ray reflectivity (XR), and ex situ X-ray fluorescence (XRF). Selected experiments were performed on the calcite (CaCO 3) (104) surface for comparison. Aqueous solutions of CdCl 2, CaCl 2, and NaHCO 3, undersaturated with respect to calcite and supersaturated with respect to otavite (CdCO 3) and the (Cd xCa 1-x)CO 3 solid solution, were reacted with dolomite surfaces for minutes to days. Calcite substratesmore » were reacted with solutions containing 1-50 μM CdCl 2, and with no added Ca or CO 3. Thin carbonate films following the Stranski-Krastanov growth mode were observed on both substrates. Specular XR and XRF revealed the formation of nm-thick Cd-rich carbonate films that were structurally ordered with respect to the dolomite (104) plane. Epitaxial films adopted the calcite crystal structure with a d 104- spacing (3.00 Å) larger than those of pure dolomite (2.88 Å) and otavite (2.95 Å) indicating either a solid solution with x approximate to 0.5, or a strained Cd-rich carbonate with a composition near that of otavite. The growth rate r of this phase increases with the initial supersaturation of the solution with respect to the solid solution, beta max, and follows the empirical relationship, as determined from XRF measurements, given by: r = 10 -4.88 ± 0.422.29 ± 0.24 max - 1), (in units of atoms of Cd/Å 2/h).The morphology of the overgrowth also varied with β max, as exemplified by AFM observations. Growth at step edges occurred over the entire β max range considered, and additional growth features including 3 Å high monolayer islands and ~ 25 Å high tall islands were observed when log β max > 1. On calcite, in situ XR indicated that this phase is similar to the Cd-rich overgrowth formed on dolomite and images obtained from X-ray reflection interface microscopy (XRIM) reveal the existence of laterally variable Cd-rich domains.« less