— A) Bright‐field TEM image and B) corresponding SAED pattern of a single crystal domain in dolomite film generated from ACC films prepared at [Ca²⁺] = 10 × 10⁻³ m and [Mg²⁺] = 100 × 10 ...
— However, the mixture of calcite and vaterite, the mixture of aragonite and calcite, pure calcite cryatals were produced when the concentration of imidazole were 50%, 60%, 70%, respectively; In the ...
— The non-linearity of Eq. (1) in seawater is consistent with the calcite surface transitioning through three dissolution mechanisms that become active at different critical saturations ("Ω critical s"): retreat of pre-existing steps for Ω = 1 to Ω critical ≈ 0.9, the opening of etch pits at defects for Ω ≈ 0.9 to Ω critical ≈ 0.75, and the opening of etch …
of the annealed films can be controlled according to the mag-nesium content of the ACC precursor, and pure aragonite films comprising single crystal domains are formed at very low mag-nesium concentrations. With the ability to characterize the thin films using transmission electron microscopy (TEM), these
— Nevertheless, our calcite films remained intact and continuous throughout the SFA experiments, ... (SI) with respect to calcite and Ca 2+ concentration were calculated in the PhreeqC software, ...
— This film covers the crystal surface forming a layer that prevents direct interaction of ions and molecules with the calcite surface, for example reducing ... (of which 40 Å in the z-direction is the calcite crystal), the ion concentration is approximately 250 mM. We note that this concentration is considerably higher than that used in the XR ...
— An innovative sampling and measurement protocol combined with scanning and transmission electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy is presented,...
— 4. Kinetic fractionation and evaporation. When calcite precipitates from a thin film of drip water that is supersaturated with respect to calcite Ca 2+ and carbonate are removed from the solution and irreversibly incorporated into the calcite crystal lattice. During this process the concentration of DIC changes with some time dependent function C(t), …
— Crystallization of two-dimensional spherulitic calcium carbonate films was performed on planar films of chitosan in the presence of poly(acrylic acid) (PAA). The …
— A new and simple method for preparing large-area and continuous calcium carbonate films under mild conditions is described. Amorphous calcium carbonate (ACC) films have been formed both in …
— They observed that calcite was formed at low concentrations of the reactants through the transformation of unstable phases, ACC, vaterite and aragonite, into stable calcite. ... that the absorption of CO 2 in a suspension of lime is accompanied and boosted by a fast reaction in the gas-liquid film [119, 153]. The use of gas mixtures has not a ...
— At constant calcium chloride and polymer (polyaspartic acid, sodium salt) concentrations, a pronounced influence of the Mg 2+ /Ca 2+ ratio was observed. Our experiments revealed an increasing inhibitory effect of Mg 2+ on calcite growth with the increase of Mg 2+ /Ca 2+ ratio in the parent solution, but this effect was manifest in …
— In particular, when calcium is leaving (entering) the water film—i.e. deposition, f>0 (dissolution, f<0)—then the calcium concentration increases (decreases) from the …
— This film covers the crystal surface forming a layer that prevents direct interaction of ions ... (of which 40 Å in the z-direction is the calcite crystal), the ion concentration is approximately ...
Experimental Methods of Calcite Dissolution 107 by Nernst (1904). It assumes that mass transport by molecular diffusion is essentially across a Nernst layer of thickness B, which has to be defined for each special case. For a first-order heterogeneous reaction at the surface, the flux Fe from the
— The optimal concentration in DHBC was found to be between 3 and 10 ppm, and ACC nanoparticles of 60–100 nm in diameter could be formed. ... They found that oriented large-area calcite films could be prepared by controlling the transformation of an ACC film by varying the temperature conditions in air and air humidity, without the aid of …
— Particles of calcite start to dissolve in environments where the ambient seawater carbonate ion concentration falls beneath the equilibrium carbonate ion concentration (which is elevated towards the …
— The calcite films thus grown within days or weeks varied in thickness but typically were polycrystalline and epitaxial: a variety of morphologies and surface features are recorded. ... In uncoated samples the portlandite crystal dissolves in the aqueous phase and the corresponding rise in calcium concentration is monitored as a function of time ...
— At low water-film thickness this reaction becomes rate limiting. The time dependent diffusion–reaction equations are solved for free drift dissolution by a finite-difference scheme, to obtain the dissolution rate of calcite as a function of the average calcium concentration in the water film. Dissolution rates are obtained for high ...
— Sr partitioning on calcite crystals growing from Ca 2 +–Sr 2 +–CO 3 2 − solutions was studied by means of friction force microscopy (FFM). Experiments were performed with various Sr 2 +(aq) /Ca 2 +(aq) concentration ratios and total Sr 2 +(aq) concentration in order to examine conditions under which Sr-calcite growth is self …
— Pore fluid Sr concentrations tend to increase with depth and time due to calcite dissolution and precipitation (Fig. 1).The increase in pore fluid Sr occurs even if R net = 0, because primary biogenic calcite has Sr concentrations that are much higher than the equilibrium value with respect to seawater (Zhang et al., 2020).When biogenic …
At low concentration (o24 mM), Mg2+ modifies the habit to form calcite with a prismatic shape; while at higher concentrations, approaching that of seawater (51 mM), the calcite is mostly inhibited, thus enabling the …
— The main challenges are as follows: (i) calcite has a soluble mineral surface involved in dissolution and precipitation processes in solutions; (ii) Ca 2+ and CO 3 2− are released by calcite dissolution and Ca 2+ ions combine with PO 4 3− to form calcium phosphate precipitates, while CO 3 2−, as a base, has a strong impact on the ...
There is a tremendous amount of literature on calcite dissolution experiments performed with various materials (synthetic calcite, natural calcites and limestone) under various …
— Using recent data on calcite dissolution and precipitation by Plummer et al., the deposition of CaCO 3 from thin films of supersaturated solutions of H 2 O/1bCO 2 /1bCaCO 3 to a CaCO 3 surface is calculated. The results are compared to previous calculations by Dreybrodt, which were based on precipitation kinetics as proposed by …
— Changes in calcification of marine organisms must be considered to explain the deepening of carbonate accumulation during ocean recovery from acidification …
— Speleothem deposits are among the most valuable continental formations in paleoclimate research, as they can be dated using absolute dating methods, and they also provide valuable climate proxies.
— We welcome the opportunity to comment on Victor Truesdale's paper, "Evidence and potential implications of exponential tails to concentration versus time plots for the batch dissolution of calcite" (Truesdale 2015).There are two major issues that warrant discussion here: (1) how rate "constants" are manipulated to describe overall …
— The vertical settling of plastic debris in oceans is poorly understood. A large share of low-density microplastics (LDMPs) are largely absent from sea surfaces. The present study employs a model ...
— We demonstrated the crystallization of calcium carbonate (CaCO 3) on polarized calcite single crystal substrates with three different orientations characterized by the (10.0), (00.1), and (10.4) planes in the presence of polyaspartic acid (PAsp) as an organic additive.The precipitates had a multiple phase structure with thin-film-like and …
— In this work, the removal of phosphate with or without added sulfate at various concentrations was studied at 48 h and at pH 4.5 or 13.0 (Fig. 3)pared to the results without the addition of sulfate at pH 4.5, low SO 4 2− /PO 4 3− ratios of 1.5 and 3.0 enhanced the removal of phosphate. Because sulfate increased dissolution of calcite …
— Conversely, in a dry system, the entire calcite interface becomes accessible for hydrogen adsorption, resulting in comparatively higher adsorption values. Apart from this, the percentage decrease was consistent in all temperatures since the water-film concentration was kept constant at all temperature values. 3.6.
