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Article Dans Une Revue Crystal Growth & Design Année : 2021

Anisotropic Time-Resolved Dynamics of Crystal Growth Induced by a Single Laser Pulse Nucleation

Résumé

Nucleation and growth of crystallites are induced by the shockwave of a single laser nanosecond pulse in highly supersaturated solutions of potassium nitrate (saltpeter). The kinetics of the turbidity resulting from the light scattering by the growing crystals is observed by time-resolved optical spectroscopy. With an optical path of 10 mm, we first focused on the early part of the growth under various conditions, but it is limited by the detection system to a few percent of the total growth. Remarkably, in this domain and for all supersaturated concentrations studied, the turbidity increases proportionally with time. This zero-order process with an accretion rate constant (k = 4.7 × 107 L mol–1 s–1) implies that the nuclei and growing crystals’ concentration remain constant. This concentration is determined from the final diameter of crystals that are observed to have a bipyramidal shape by transmission electron microscopy (TEM). Moreover, the number of accretion sites per crystal must be constant in this time range and they are identified as the apexes. In complement, the kinetics detected with shorter optical paths permits us to observe larger parts of the total growth (up to 35% with 1 mm of optical path). In this case, after the linear part, the turbidity increase is markedly accelerated, indicating that the number of accretion sites per crystal increases rapidly with the crystal size and that the edges and facet sites also fix the molecules. The complete analysis by a homogeneous kinetics model of the signals obtained under various conditions concludes to an anisotropic growth of the crystals with another accretion rate constant (k′ = 100 L mol–1 s–1) that is much lower on these edges and facet sites than on the apexes. However, this contribution becomes predominant only when the crystals develop to a larger size.

Domaines

Matériaux
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Dates et versions

hal-03322576 , version 1 (26-10-2021)

Identifiants

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Sarah Al Gharib, Abdel Karim El Omar, Adnan Naja, Ariane Deniset-Besseau, Sergey Denisov, et al.. Anisotropic Time-Resolved Dynamics of Crystal Growth Induced by a Single Laser Pulse Nucleation. Crystal Growth & Design, 2021, 21 (2), pp.799-808. ⟨10.1021/acs.cgd.0c01016⟩. ⟨hal-03322576⟩
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