PROMOTING DESIRED WETTING BEHAVIOR IN GRAPHENE AND MICRO/NANOSTRUCTURED SYSTEMS

Carpenter, James S

Permalink

https://hdl.handle.net/2142/121252 Copy

Description

Title

PROMOTING DESIRED WETTING BEHAVIOR IN GRAPHENE AND MICRO/NANOSTRUCTURED SYSTEMS

Author(s)

Carpenter, James S

Issue Date

2023-07-13

Director of Research (if dissertation) or Advisor (if thesis)

Miljkovic, Nenad

Doctoral Committee Chair(s)

Miljkovic, Nenad

Committee Member(s)

• van der Zande, Arend
• Braun, Paul
• Murphy, Catherine

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Wettability
• Superhydrophobic
• Graphene

Abstract

Solid/liquid interactions are ubiquitous in nature and many different technological applications. In particular, surface energy and wettability are important to perfomance in biofouling, chemical and biological sensors, anti-icing/frosting, phase change heat transfer, and other areas. Non-wetting superhydrophobic surfaces are a potentially effective strategy to prevent the freezing of supercooled droplets upon impact, an undesirable outcome in HVAC, power transmission, and aircraft applications. While there have been studies examining the anti-icing performance of supercooled droplets impacting supercooled superhydrophobic surfaces, few (if any) have performed this examination for deeply supercooled water droplet temperatures down to -15 °C in icing conditions. This dissertation details experimental work on characterizing the anti-icing performance of a rationally-designed, supercooled (down to -35 °C) superhydrophobic surface being impacted by supercooled (down to -15 °C) water droplets. The results show different freezing conditions based on droplet temperature, surface temperature, and impact speed, results which can be used to rationally design anti-icing surfaces. Moreover, the surface energy of graphene and its chemical derivatives governs fundamental interfacial interactions like molecular assembly, wetting, and doping. However, quantifying the surface energy of supported 2D materials, such as graphene, is difficult because (1) they are so thin that electrostatic interactions emanating from the underlying substrate are not completely screened, (2) the contribution from the monolayer is sensitive to its exact chemical state, and (3) the adsorption of airborne contaminants, as well as contaminants introduced during transfer processing, screen the electrostatic interactions from the monolayer and underlying substrate, changing the determined surface energy. Here, we determine the polar and dispersive surface energy of bare, fluorinated, and hydrogenated graphene through contact angle measurements with water and diiodomethane. We accounted for environmental factors, including substrate surface energies and combating adsorption of airborne contaminants by using a pressurized inert gas vessel. Hydrogenating graphene raises the polar surface energy with little effect on its dispersive surface energy. Fluorinating graphene lowers the dispersive surface energy with a substrate-dependent effect on its polar surface energy. These results unravel how changing graphene structure modifies surface energy, with applications for hybrid nanomaterials, bioadhesion, biosensing, and remote epitaxy. Overall, this dissertation provides needed experimental design criteria for anti-icing performance during supercooled droplet impact on non-wetting superhydrophobic surfaces. Further, it provides needed measurements of the surface energy of two common chemically functionalized forms of graphene, while employing measures to ensure reproducible results.

Graduation Semester

2023-08

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 James Carpenter

Owning Collections