On the sensitivity of the evaporative pattern deposition of particulate mass to the ionic strength in kinetically stable
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part of Springer Nature, 2020 https://doi.org/10.1140/epjst/e2020-000005-6
THE EUROPEAN PHYSICAL JOURNAL SPECIAL TOPICS
Regular Article
On the sensitivity of the evaporative pattern deposition of particulate mass to the ionic strength in kinetically stable suspensions Anna Zigelman, Ekhlas Homede and Ofer Manora Wolfson Department of Chemical Engineering, Technion-Israel Institute of Technology, Haifa 3200003, Israel Received 15 January 2020 / Accepted 6 July 2020 Published online 14 September 2020 Abstract. The deposition of particulate mass from a volatile suspension is a common process. Usually, the employed suspensions are designed to be kinetically stable, which is achieved by employing surface forces of molecular origin, e.g., the electrical double layer (EDL) or steric forces, to render high energy barriers to particle attachments. One may expect that a high energy barrier in the original suspension will render the deposit morphology solely connected to particle convection in the volatile liquid and, once most of the carrier liquid has evaporated, to capillary attraction between detached particles to each other and to the solid substrate. However, we show that variations in the magnitude of large energy barriers to particle attachments in our original suspensions are connected to variations in the deposit morphology following the evaporation of the carrier liquid. In our experiments, the different original EDL induced energy barriers are large and traverse tens and hundreds of KB T in magnitude. Nevertheless, the evaporation of the carrier liquid during the deposition process supports the convection of mass toward the three phase contact line between the suspension, substrate, and vapor phases. The convection of particle and ion mass dynamically increases particle concentration and ionic strength in the vicinity of the contact line. The elevated ionic strength reduces the energy barriers to particle attachments in that vicinity, which appears to locally support particle coagulation and adsorption effects and hence to alter the deposit morphology. Thus, the morphology of the deposit may show considerable sensitivity to the specific magnitude of energy barrier to particle attachments in the original, kinetically stable, suspension.
1 Introduction The deposition of colloidal assemblies via the evaporation of colloidal suspensions attracts a great deal of attention from experimental perspective [1–6] as well as from a theoretical point of view [7–11]. Among the main applications of the manipulated a
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The European Physical Journal Special Topics
particulate morphologies are the fabrication of electronic circuits, printing, coating, separation processes, etc. [12–15]. The deposition of nanoparticles from volatile liquids attracts special interest due to their properties which many times are directly related to their size [16]. A variety of methods to produce and deposit the colloids were proposed elsewhere [17–20]. In particular, attention is given to keeping colloidal d
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