Model for interpreting surface crystallization using quartz crystal microbalance: theory and experiments
Author(s)
Lapidot, T
Sedransk Campbell, KL
Heng, JY
Type
Journal Article
Abstract
Surface crystallization of calcium sulfate was investigated using a dissipation crystal quartz microbalance (QCM-D) together with microscopy to understand the mechanical property changes occurring during the growth process. The use of optical microscopy and SEM revealed that needle-shaped crystals grow as clusters on the QCM sensor’s surface, not in uniform layers. As crystallization growth progressed, QCM-D revealed inversions between negative and positive frequency shifts. This behavior, a function of the growth of crystals in clusters, is not adequately predicted by existing models. As such, a new mass-to-frequency conversion model is proposed herein to explain the observed frequency inversions. This model is derived from a lumped element approach with point-contact loading and Mason equivalent circuit theory. Critically, the physical phenomena occurring form the basis of the model, particularly addressing the three sources of impedance. When a crystal nucleates and grows, its inertial impedance is considered along with a Kelvin–Voigt link with a hydration layer. A comparison between the proposed model and experimental data, of both frequency and dissipation data for the first four harmonics, shows good agreement for the supersaturations (S = C/C*) of S = 3.75, S = 3.48, and S = 3.22. Additionally, significant improvements over existing models for the case of surface crystallization are observed. The proposed model was therefore able to explain that frequency inversions are caused by a shift from inertia-dominated to elastic-dominated impedance, occurring as a result of crystal growth. Using the nucleation induction time and nucleation rates, determined with imaging, an additional understanding of the crystals’ mechanical properties (stiffness and dampening) was obtained.
Date Issued
2016-03-30
Date Acceptance
2016-03-30
Citation
Analytical Chemistry, 2016, 88 (9), pp.4886-4893
ISSN
1086-4377
Publisher
American Chemical Society
Start Page
4886
End Page
4893
Journal / Book Title
Analytical Chemistry
Volume
88
Issue
9
Copyright Statement
This document is the Accepted Manuscript version of a Published Work that appeared in final form in Analytical Chemistry, © 2016 American Chemical Society, after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.analchem.6b00713
Subjects
Analytical Chemistry
0301 Analytical Chemistry
0904 Chemical Engineering
0399 Other Chemical Sciences
Publication Status
Published