AFM Investigation for the Initial Growth Processes of Calcium Carbonate on Hydrophilic and Hydrophobic Substrate

Abstract

Heterogeneous nucleation and crystal growth of calcium carbonate on the mica and the highly oriented pyrolytic graphite (HOPG) substrate have been investigated by means of an atomic force microscope (AFM) with a contact mode procedure. AFM observation could lead to initial crystallization processes that were amorphous and crystalline, with an intermediate state between them. Amorphous calcium carbonate deposited on surfaces could be observed as a transient precursor phase of crystal. The shape of the amorphous calcium carbonate on the substrates is indicative of final crystal shape. Classical heterogeneous nucleation theory has been considered in order to describe the surface crystallization on the mica and the HOPG. We then measured the contact angle between the amorphous calcium carbonate and the substrates. The formation energy required for the heterogeneous nucleation on the HOPG surface was 40 times higher than that on the mica surface. To explain the difference in the mica and the HOPG surface, we have discussed a possible model for the interfacial structure between the solution and the substrate.

Effect of Mica and Hematite (001) Surfaces on the Precipitation of Calcite

“…The shape of calcite-biotite interface is created as a triangle based on the interface morphology derived from SEM studies and the crystal shape of calcite. Our observations of the first set orientation are consistent with previous work on the epitaxial growth of calcite on muscovite [14,15]. For example, the authors of reference [14] showed through their SEM and XRD measurements that the (001) plane of calcite is aligned virtually parallel to the muscovite basal plane, which is the same orientation in biotite.…”

“…Normally, calcite precipitates if the Mg/Ca ratio of the solution is below about 1:5 (a tenth that of normal seawater), and aragonite becomes the only polymorph if Mg/Ca ≥ 1 [30]. This is consistent with the observations in modern marine environment where dissolved magnesium Our observations of the first set orientation are consistent with previous work on the epitaxial growth of calcite on muscovite [14,15]. For example, the authors of reference [14] showed through their SEM and XRD measurements that the (001) plane of calcite is aligned virtually parallel to the muscovite basal plane, which is the same orientation in biotite.…”

“…While there is a plethora of literature work concerning carbonates crystallization on carbonate seeds or on structured organic surfaces [8][9][10][11][12][13], only a few studies have dealt with the effect of non-carbonate minerals on carbonate nucleation and crystallization [14,15]. In the present work, we examine the epitaxial growth of CaCO 3 polymorphs on biotite, muscovite, hematite to evaluate the effect of geometry match between functional and binding groups on the substrates' basal (001) face and structures of calcite surfaces.…”

Bio-inspired superhydrophilic coatings with high anti-adhesion against mineral scales

“…As shown in Figure 3a, the CARs of the nanohair hydrogel coatings clearly reduced as the nanohair length gradually increased. Compared with the flat hydrogel coatings (CARs of 2.70 ± 0.70%), the nanohair hydrogel coatings exhibit considerable anti-adhesion performance against mineral crystals (CARs of 0.73 ± 0.30% for the short nanohairs), especially for the superhydrophilic intermediate and long nanohairs (CARs of 0.30 ± 0.08% and 0.17 ± 0.09%, respectively), which may be because water molecules preferentially approach the superhydrophilic surface of PHEMA nanohairs, thereby reducing the growth of mineral crystals, 48 and because the abundant -OH groups also promote resistance against the adhesion of these mineral crystals. 49 Therefore, the superhydrophilic property and surface structure of the nanohair hydrogel coatings probably contribute to their unique anti-scaling property.…”

Fundamental nanoscale surface strategies for robustly controlling heterogeneous nucleation of calcium carbonate

“…5 However, it is oen not possible to exclusively study one particular factor since adjustment of surface chemistry also leads to changes in other surface properties. Consequently, in spite of the previous attempts to investigate heterogeneous nucleation and growth of CaCO 3 on different surfaces, [13][14][15][16][17][18][19][20][21] much is still unknown before a guiding principle can be developed for designing surfaces to control this dynamic process.…”