Morphological Control of Multifunctional Melting Gel Coatings via Electrospray Deposition
The ability to alter surface interactions with controlled coatings is a fundamental area in materials processing. Oligomeric silsesquioxanes (OSS), or melting gels (MG), are a class of hybrid gels comprised of an inorganic 3D network with grafted functional organic components. They are synthesized via the sol-gel process, which refers to the initiation of an inorganic network from a precursor solution. Melting gels are typically produced through the hydrolysis and polymerization of their alkoxide type precursors such as tetraethyl orthosilicate (TEOS) and mono- or di-substituted siloxanes. The final product is a hybrid gel with nanoscale mixing whose bulk properties are determined by the initial mixing ratios of its components. The reversible “melting” at around 110℃ is a result of the incomplete hydrolyzing/condensation of the substitute siloxane; it is a softening process that occurs by sufficiently exceeding the gel’s glass transition temperature. When gels are heat treated at or above their consolidation point (130℃ - 170℃), they undergo further cross-linking to form organically modified silica glasses. Owing to their hybrid nature, melting gels leverage the benefits of both their components: their coatings are dense, crack-free, and hermetic with low temperature processing. By appropriately tuning surface properties, these glass sprays can be used as protective coatings in electronics and anti-corrosion coatings in metals. Electrospray deposition (ESD) presents itself as a useful MG coating technique because it potentially offers dynamic control over the consolidated gel structure down to the micro- and nanoscale. ESD uses high voltages to produce charged, monodisperse droplets from a solution, and when using low solid contents, it uniformly delivers small amounts of melting gel at a continuous rate. Recent work has also demonstrated ESD’s ability to coat 3D objects due to its self-limiting nature when spraying insulating materials. In order to gain a fundamental understanding of this melting gel deposition technique, the interaction between charged electrospray droplets and simultaneous consolidation reactions must be investigated. ESD was used to spray dilute solutions of 1 wt% methyl- and phenyl-substituted melting gels in 2-butanone onto silicon. Parameters such as the pH of melting gel synthesis, solution viscosity, and spray polarity can be varied to alter and study the effects of charge injection on the consolidation of melting gels into hybrid glasses. Furthermore, the precise effects of charge injection can be isolated by comparing spun and sprayed films. Optical images, film thickness measurements, nanoindentation, FT-IR, and goniometry were used to evaluate and demonstrate the effects of these parameters on both the physical morphology along with the chemical structure of final coatings.
Morphological Control of Multifunctional Melting Gel Coatings via Electrospray Deposition
Category
Poster Presentation
Description
Session: 16-01-01 National Science Foundation Posters - On Demand
ASME Paper Number: IMECE2020-25155
Session Start Time: ,
Presenting Author: Arielle Gamboa
Presenting Author Bio: Arielle recently earned her BS and MS degrees in Mechanical Engineering at Rutgers University under the supervision of Dr. Jonathan P. Singer. Her MS thesis focused on the electrospray deposition of melting gels and was funded through the NSF Advanced Manufacturing Program (Award #1911518). During her time in Dr. Singer’s group, she also worked on several other projects that explored laser-induced thermocapillary dewetting and electrospray deposition for fabrication and materials processing. Throughout her undergraduate career, she was an active member in numerous student organizations committed to outreach and professional development, including the Rutgers ASME chapter where she served as the society representative and secretary for two years. She is currently pursuing her PhD in Mechanical Engineering at the University of Illinois, Urbana-Champaign, in the Energy Transport Research Lab.
Authors: Arielle Marie Gamboa Rutgers University
Lin Lei Rutgers University
James Mercado Lehman College-CUNY
Jennifer Guzman Lehman College-CUNY
Lisa KleinRutgers University
Andrei Jitianu Lehman College-CUNY
Jonathan Singer Rutgers University