基底上矿物成核和生长的数值研究,ACS Earth and Space Chemistry

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基底上矿物成核和生长的数值研究
ACS Earth and Space Chemistry ( IF 2.9 ) Pub Date : 2022-06-09 , DOI: 10.1021/acsearthspacechem.1c00376
Fengchang Yang ₁ , Ke Yuan ₁ , Andrew G. Stack ₁ , Vitalii Starchenko ₁

Affiliation

由于溶液中反应性离子的传输限制和局部消耗，矿物和其他晶体的成核和生长过程可以相互显着影响。大多数数值模型和实验测量通常都集中在生长或成核上，但不是两者兼而有之。在这项工作中，我们将基于经典成核理论的异质成核过程结合到微连续体模型中，该模型实施了 Darcy-Brinkman-Stokes 方法来研究扩散系统中衬底上的成核和晶体生长之间的相互作用。我们展示了 Damköhler 数（反应速率）和成核速率前因子如何改变基板上的有效成核速率。较高的表面生长速率会耗尽最初出现在基板上的核周围的溶质浓度，创建屏蔽进一步成核的岛。该模型预测，测量的成核率可能会受到基板上晶体成核历史的影响。在相对于扩散的高增长率的极端情况下，它预测随后的成核速率受到反应物耗尽的限制。我们引入一个无量纲数 α 来表示生长过程中的表面传播速率与异质成核速率之间的关系。我们表明，控制 Damköhler 数和 α 以在不同的反应和成核速率下实现相似的沉淀状态非常重要。我们建议观察到的普遍性可以指导对成核率实验结果的解释，因为匹配实验可以通过同时调整传输、反应和成核参数来实现。

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Numerical Study of Mineral Nucleation and Growth on a Substrate

Nucleation and growth processes of minerals and other crystals can significantly affect one another due to the transport limitations and local depletion of reactive ions in the solution. Most numerical models and experimental measurements have typically focused on either growth or nucleation, but not both. In this work, we incorporate a heterogeneous nucleation process based on classical nucleation theory into a microcontinuum model that implements the Darcy–Brinkman–Stokes approach to study the interplay between nucleation and crystal growth on a substrate in diffusive systems. We demonstrate how the Damköhler number (reaction rate) and nucleation rate prefactor change the effective nucleation rate on a substrate. Higher surface growth rates deplete the solute concentration around the nuclei that appear initially on the substrate, creating islands that screen against further nucleation. The model predicts that measured nucleation rates may be affected by the history of crystal nucleation on the substrate. In the extreme case of high growth rates relative to diffusion, it predicts that the rate of subsequent nucleation is limited by reactant depletion. We introduce a nondimensional number α to represent the relation between surface propagation rate during growth and the heterogeneous nucleation rate. We show that it is important to control Damköhler number and α to achieve similar precipitation regimes at different reaction and nucleation rates. We suggest that the observed universality can guide the interpretation of experimental results on nucleation rates, since matching experiment can be achieved by tuning transport, reaction, and nucleation parameters simultaneously. In addition, we show how the bulk solution concentration affects the structure and topology of precipitation on a substrate.

更新日期：2022-06-09

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