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Title: Manganese-calcium intermixing facilitates heteroepitaxial growth at the (1014) calcite-water interface

Abstract

For this research, in situ atomic force microscopy (AFM) measurements were performed to probe surface precipitates that formed on the (10$$\bar{1}$$4) surface of calcite (CaCO 3) single crystals following reaction with Mn2 +-bearing aqueous solutions. Three-dimensional epitaxial islands were observed to precipitate and grow on the surfaces. In situ time-sequenced measurements demonstrated that the growth rates were commensurate with those obtained for epitaxial islands formed on calcite crystals reacted with Cd2 +-bearing aqueous solutions of the same range in supersaturation with respect to the pure metal carbonate phase. This finding was unexpected as rhodochrosite (MnCO 3) and calcite display a 10% lattice mismatch, based on the area of their (10$$\bar{1}$$4) surface unit cells, whereas the lattice mismatch is only 4% for otavite (CdCO 3) and calcite. Coatings of varying thicknesses were therefore synthesized by reacting calcite single crystals in calcite-equilibrated aqueous solutions with up to 250 μM MnCl 2. Ex situ X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectivity (XRR), and AFM measurements of the reacted crystals demonstrated the formation of an epitaxial (Mn,Ca)CO 3 solid solution. The epitaxial solid solution had a spatially complex composition, whereby the first few nanometers were rich in Ca and the Mn content increased with distance from the original calcite surface, culminating in a topmost region of almost pure MnCO 3 for the thickest coatings. The effective lattice mismatch was therefore much smaller than the nominal mismatch thus explaining the measured growth rates. Lastly, these findings highlight the strong influence played by the substrate on the composition of surface precipitates in aqueous conditions.

Authors:
 [1];  [1];  [1];  [1];  [2];  [2];  [3];  [1]; ORCiD logo [1]
  1. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Physical and Computational Sciences Directorate, Physical Sciences Division
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Earth and Biological Sciences Directorate, Environmental Molecular Sciences Division
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Energy and Environment Directorate, Nuclear Sciences Division
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1379947
Report Number(s):
PNNL-SA-125533
Journal ID: ISSN 0009-2541; PII: S0009254117304904
Grant/Contract Number:
AC05-76RL01830
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Volume: 470; Journal ID: ISSN 0009-2541
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 58 GEOSCIENCES; Metal carbonates; Epitaxy; Mineral growth; Lattice mismatch; Mineral coatings

Citation Formats

Xu, Man, Riechers, Shawn L., Ilton, Eugene S., Du, Yingge, Kovarik, Libor, Varga, Tamas, Arey, Bruce W., Qafoku, Odeta, and Kerisit, Sebastien. Manganese-calcium intermixing facilitates heteroepitaxial growth at the (1014) calcite-water interface. United States: N. p., 2017. Web. doi:10.1016/j.chemgeo.2017.09.001.
Xu, Man, Riechers, Shawn L., Ilton, Eugene S., Du, Yingge, Kovarik, Libor, Varga, Tamas, Arey, Bruce W., Qafoku, Odeta, & Kerisit, Sebastien. Manganese-calcium intermixing facilitates heteroepitaxial growth at the (1014) calcite-water interface. United States. doi:10.1016/j.chemgeo.2017.09.001.
Xu, Man, Riechers, Shawn L., Ilton, Eugene S., Du, Yingge, Kovarik, Libor, Varga, Tamas, Arey, Bruce W., Qafoku, Odeta, and Kerisit, Sebastien. 2017. "Manganese-calcium intermixing facilitates heteroepitaxial growth at the (1014) calcite-water interface". United States. doi:10.1016/j.chemgeo.2017.09.001.
@article{osti_1379947,
title = {Manganese-calcium intermixing facilitates heteroepitaxial growth at the (1014) calcite-water interface},
author = {Xu, Man and Riechers, Shawn L. and Ilton, Eugene S. and Du, Yingge and Kovarik, Libor and Varga, Tamas and Arey, Bruce W. and Qafoku, Odeta and Kerisit, Sebastien},
abstractNote = {For this research, in situ atomic force microscopy (AFM) measurements were performed to probe surface precipitates that formed on the (10$\bar{1}$4) surface of calcite (CaCO3) single crystals following reaction with Mn2+-bearing aqueous solutions. Three-dimensional epitaxial islands were observed to precipitate and grow on the surfaces. In situ time-sequenced measurements demonstrated that the growth rates were commensurate with those obtained for epitaxial islands formed on calcite crystals reacted with Cd2+-bearing aqueous solutions of the same range in supersaturation with respect to the pure metal carbonate phase. This finding was unexpected as rhodochrosite (MnCO3) and calcite display a 10% lattice mismatch, based on the area of their (10$\bar{1}$4) surface unit cells, whereas the lattice mismatch is only 4% for otavite (CdCO3) and calcite. Coatings of varying thicknesses were therefore synthesized by reacting calcite single crystals in calcite-equilibrated aqueous solutions with up to 250 μM MnCl2. Ex situ X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectivity (XRR), and AFM measurements of the reacted crystals demonstrated the formation of an epitaxial (Mn,Ca)CO3 solid solution. The epitaxial solid solution had a spatially complex composition, whereby the first few nanometers were rich in Ca and the Mn content increased with distance from the original calcite surface, culminating in a topmost region of almost pure MnCO3 for the thickest coatings. The effective lattice mismatch was therefore much smaller than the nominal mismatch thus explaining the measured growth rates. Lastly, these findings highlight the strong influence played by the substrate on the composition of surface precipitates in aqueous conditions.},
doi = {10.1016/j.chemgeo.2017.09.001},
journal = {Chemical Geology},
number = ,
volume = 470,
place = {United States},
year = 2017,
month = 9
}

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  • In situ atomic force microscopy (AFM) measurements were performed to probe surface precipitates that formed on the (10-14) surface of calcite (CaCO3) single crystals following reaction with Mn2+-bearing aqueous solutions with a range of initial concentrations. Three-dimensional epitaxial islands were observed to precipitate and grow on the surfaces and in situ time-sequenced measurements demonstrated that their growth rates were commensurate with those obtained for epitaxial islands formed on calcite crystals reacted with Cd2+-bearing aqueous solutions of the same range in supersaturation with respect to the pure metal carbonate phase. This finding was unexpected as rhodochrosite (MnCO3) and calcite display amore » 10% lattice mismatch, based on the area of their (10-14) surface unit cells, whereas the lattice mismatch is only 4% for otavite (CdCO3) and calcite. Coatings of varying thicknesses were therefore synthesized by reacting calcite single crystals with calcite-equilibrated aqueous solutions with concentrations of up to 250 µM MnCl2 and analyzed to determine the composition of the surface precipitates. Ex situ X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectivity (XRR), and AFM measurements of the reacted crystals demonstrated the formation of an epitaxial (Mn,Ca)CO3 solid solution with a spatially complex composition atop the calcite surface, whereby the first few nanometers were rich in Ca and the Mn content increased with distance from the original calcite surface, culminating in a topmost region of almost pure MnCO3 for the thickest coatings. These findings explain the measured growth rates (the effective lattice mismatch was much smaller than nominal mismatch) and highlight the strong influence played by the substrate on the composition of surface precipitates in aqueous conditions.« less
  • Heteroepitaxy of a manganese carbonate phase with nanometer dimensions on the (101{sub 4}) surface of calcite (CaCO3) using an AFM has been observed in solution during dissolution of calcite when the ion activity product of Mn2? and CO32- nears the solubility limit of MnCO3. Growth-rate observations at different Mn concentrations, coupled with XPS and EPR measurements, suggest that the resulting phase is Mn05Ca05CO3. These islands, while growing many microns in length along the[22{sub 1}] direction, have a uniform width in the range of 120-240 nm and a uniform height of approximately 2.7 nm, corresponding to nine atomic layers. The islandsmore » cease growing when they encounter step edges and have been observed to dissolve when undercut by a growing etch pit.« less
  • Elucidating how cation intermixing can affect the mechanisms of heteroepitaxial growth in aqueous media has remained a challenging endeavor. Toward this goal, in situ atomic force microscopy was employed to image the heteroepitaxial growth of otavite (CdCO3) at the (10-14) surface of calcite (CaCO3) single crystals in static aqueous conditions. Heteroepitaxial growth proceeded via spreading of three-dimensional (3D) islands and two-dimensional (2D) atomic layers at low and high initial saturation levels, respectively. Experiments were carried out as a function of applied force and imaging mode thus enabling determination of growth mechanisms unaltered by imaging artifacts. This approach revealed the significantmore » anisotropic nature of heteroepitaxial growth on calcite in both growth modes and its dependence on supersaturation, intermixing, and substrate topography. The 3D islands not only grew preferentially along the [42-1] direction relative to the [010] direction, resulting in rod-like surface precipitates, but also showed clear preference for growth from the island end rich in obtuse/obtuse kink sites. Pinning to step edges was observed to often reverse this tendency. In the 2D growth mode, the relative velocities of acute and obtuse steps were observed to switch between the first and second atomic layers. This phenomenon stemmed from the significant Cd-Ca intermixing in the first layer, despite bulk thermodynamics predicting the formation of almost pure otavite. Composition effects were also responsible for the inability of 3D islands to grow on 2D layers in cases where both modes were observed to occur simultaneously. Overall, the AFM images highlighted the effects of intermixing on heteroepitaxial growth, particularly how it can induce thickness-dependent growth mechanisms at the nanoscale.« 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
  • 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