Development of superhydrophobicity in silane treated diatomaceous earth and polymer coatings

This dissertation describes the development of superhydrophobicity in fluorosilane treated diatomaceous earth (DE) particles and polymer coatings. The amount of silane coupling agent on the surface of DE particles has been determined by thermogravimetric analysis (TGA). The presence of silane coupling agents on the DE particles has been confirmed by Fourier transform infrared spectroscopy (FTIR). The minimum amount of fluorosilane coupling agent required to exhibit superhydrophobicity has been determined. The development of the superhydrophobicity in the coatings with simple polymers like polystyrene (PS) or poly(vinyl acetate) (PVAc) as binders has been followed as a function of the particle loading using contact angle measurements and scanning electron microscopy.The effect of particle morphology in the development of superhydrophobicity has been studied systematically. It was found that less-dense treated CelTix DE particles produced superhydrophobicity at 30 wt% of particles loading compared to more dense treated DiaFil DE (rod-shaped) and EcoFlat DE (irregularly shaped) particles with low molecular mass polystyrene binder system. The effects of particle morphology, surface area, porosity and density in the development of superhydrophobicity have been described.The effect of viscosity of the binder solution in the development of superhydrophobicity has been observed. Changes in the solvent systems have not affected the superhydrophobicity for similar coating compositions. The DE particles were found to be robust and the coatings prepared with the sonicated DE samples also exhibited superhydrophobicity.Additionally, untreated and treated diatomaceous earth particles and epoxy composites have been prepared. The thermal and dynamic mechanical properties of DE/epoxy composites have been evaluated. The mechanical properties of the DE/epoxy composites revealed that treated DE particles act as better reinforcing agents compared to untreated DE particles

Deposition and assembly of magnesium hydroxide nanostructures on zeolite 4A surfaces

A deposition - precipitation method was developed to produce magnesium hydroxide / zeolite 4A (Mg(OH)₂ - Z4A) nanocomposites at mild conditions and the effect of processing variables such as precursor concentration, type of base added, and synthesis time on the composition, size, and morphology of the nanocomposite were studied. It was determined that the precursor concentration, basicity, and synthesis time had a significant effect on the composition, size, and morphology of the deposited magnesium hydroxide (Mg(OH)₂) nanostructures. The properties of the Mg(OH)₂ - Z4A such as surface area, pore volume and composition were characterized. Mg(OH)₂ - Z4A samples and bare zeolite 4A were dispersed in Ultem® polymer to form a mixed matrix membrane. The thermal and mechanical properties of the resulting films were investigated. It was found that the addition of rigid bare zeolites into the polymer decreased the mechanical properties of the polymer composite. However, some of these adverse effects were mitigated in the polymer composite loaded with Mg(OH)₂ - Z4A samples. Isotherms for the adsorption of Mg(OH)₂ petals on zeolite 4A were measured in order to determine the optimum conditions for the formation of magnesium hydroxide / zeolite 4A nanocomposites at ambient conditions. The loading of the Mg(OH)₂ can be determined from the adsorption isotherms and it was also found that the adsorption of Mg(OH)₂ on zeolite A occurs via 3 mechanisms: ion exchange, surface adsorption of Mg²⁺ ions, and surface precipitation of Mg(OH)₂. Without the addition of ammonium hydroxide, the predominant processes are ion exchange and surface adsorption of Mg²⁺ ions. In the presence of ammonium hydroxide, Mg(OH)₂ crystals are precipitated on the surface of zeolite 4A at moderate Mg²⁺ ions concentration and the loading of Mg(OH)₂ was found to increase with increasing Mg²⁺ ions concentration. A detailed examination of the interactions between Mg(OH)₂ and functional groups on the zeolite surface was conducted. Solid-state 29Si, 27Al, and 1H NMR spectra were coupled with FTIR measurements, pH and adsorption studies, and thermogravimetric analyses to determine the interactions of Mg(OH)₂ with surface functional groups and to characterize structural changes in the resulting zeolite after Mg(OH)₂ deposition. It was discovered that acid - base interactions between the weakly basic Mg(OH)₂ and the acidic bridging hydroxyl protons on zeolite surface represent the dominant mechanism for the growth of Mg(OH)₂ nanostructures on the zeolite surface.Ph.D.Committee Chair: Teja, Amyn; Committee Member: Deng, Yulin; Committee Member: Koros, William; Committee Member: Nair, Sankar; Committee Member: Tannenbaum, Rin

Multifunctional Superhydrophobic Nanoparticle Coatings for Cellulose-based Substrates by Liquid Flame Spray

Wettability of a solid surface by a liquid plays an important role in several phenomena and applications, for example in adhesion, printing, and coating. Especially, wetting of rough surfaces has attracted a great scientific interest in recent decades. Superhydrophobic surfaces, which possess extraordinary water repellency properties due to their low surface energy chemistry and specific nano- and microscale roughness, are of particular interest due to the great variety of potential applications ranging from self-cleaning surfaces to microfluidic devices. Another driving force for the extensive scientific work on superhydrophobicity has been a desire for detailed understanding of wetting phenomena on different types of superhydrophobic surfaces, for example on natural superhydrophobic surfaces of lotus leaves where easy mobility of water droplets results in self-cleaning effect, rose petals where water droplets firmly adhere to the surface, and butterfly wings which possess directional water droplet adhesion. This thesis work reviews recent aspects on different modes of superhydrophobicity and explores a variety of functional anti-wetting/wetting properties on both natural and artificial superhydrophobic surfaces. In addition, fabrication techniques, properties, and potential applications of superhydrophobic surfaces and coatings are examined with focus on cellulose-based substrate materials on which an extensive literature survey is executed. In recent years, a great number of different approaches ranging from simple one-step methods to sophisticated multi-step procedures to fabricate superhydrophobic coatings on cellulose-based substrate materials such as cotton or paper have been reported. Potential applications for the cellulose-based superhydrophobic materials vary from water- and stain-repellent, self-cleaning and breathable clothing to cheap and disposable lab-on-a-chip devices. The experimental section of this work focuses on fabrication of functional superhydrophobic and superhydrophilic nanoparticle coatings on cellulose-based substrate materials by liquid flame spray (LFS) and examination of the coating properties. LFS proved itself straightforward and versatile one-step method to fabricate broad range of functional nanoparticle coatings on various substrate materials in an atmospheric roll-to-roll process. It has established itself among the most potential candidates for large-scale production of superhydrophobic coatings on affordable cellulose-based substrates

Control of Wettability Using Flame Generated Multicomponent Nanoparticle Coatings

Pintojen kastuvuuden muokkaaminen on ollut yksi tärkeimmistä tutkimusaiheista jo vuosia. Kehitysidea vettähylkiviin ja vesihakuisiin pintoihin on tullut alun perin luonnon esimerkeistä. Yleisin tapa muokata pinnan kastumista on valmistaa pinnalle toiminnallinen nanopinnoite. Tässä työssä valmistettiin toiminnallisia nanopinnoitteita kartonki-, puu- ja lasipinnoille. Menetelmänä käytettiin nesteliekkiruiskutusta (Liquid Flame Spray, LFS), jossa nanohiukkasia muodostetaan aerosolimenetelmällä. Superhydrofobisia eli vettähylkiviä ja superhydrofiilisiä eli vesihakuisia pinnoitteita on tehty jo aiemmin nesteliekkiruiskutuksella, mutta tässä työssä tutkittiin tarkemmin pinnoitteen rakennetta ja selvitettiin mikä on minimimäärä pinnoitetta, jolla pinnan kastumista saadaan muokattua. Pinnan kastuvuus muuttui radikaalisti, vaikka pinta oli vain osittain nanohiukkasten peitossa. Pinnoitteen pysyvyys ja kulutuskestävyys ovat perinteisesti nanopinnoitteiden suurimpia ongelmia, joten ne ovat tämänkin työn tutkimusaiheita. Pinnoitteen kestävyys riippuu pääosin pinnoitteen adheesiosta ja koheesiosta. Adheesiolla tarkoitetaan pinnoitteen kiinnittymistä materiaalin pintaan ja koheesiolla hiukkasten keskinäistä kiinnipysyvyyttä nanopinnoitteessa. Tässä työssä koheesiota on pyritty parantamaan muokkaamalla nanopinnoitteen hiukkasrakennetta. Aiemmissa töissä superhydrofobinen pinnoite on saatu aikaan TiO2 nanohiukkasilla, mutta tässä työssä TiO2 nanopinnoitteen agglomeraattien kestävyyttä parannettiin lisäämällä pinnoitteeseen myös SiO2 nanohiukkasia. Tällä tavoin pinnoitteen koheesiota saatiin parannettua niin että pinnoitteen huokoisuus ja vettähylkivyys säilyivät lähes ennallaan. Tässä työssä LFS-menetelmää yhdisteltiin myös muiden pinnoitusmenetelmien kanssa. Yhdistämällä useiden pinnoitusmenetelmien hyviä puolia, saatiin aikaan superamfifobinen pinnoite eli pinnoite hylki myös muita nesteitä kuin vain vettä. LFS-menetelmällä valmistettiin huokoinen nanorakenne, jonka pintaa parannettiin plasmakäsittelyllä tai kemiallisella kaasufaasipinnoituksella (Chemical Vapor Deposition, CVD). Näillä yhdistelmäpinnoituksilla pinta saatiin hylkimään vettä, oliiviöljyä, etyleeniglykolia, diodometaania sekä n-heksadekaania. Yhdistelmäpinnoitteiden pysyvyyttä testattiin pisaratesteillä, joissa pinnoille pudotettiin tuhansia vesipisaroita. Pinnoite pysyi vahingoittumattomana, joten yhdistelmäpinnoitteella voitiin todeta olevan kohtuullisen hyvä adheesio ja koheesio.Control of wettability of surfaces has been a hot research topic for years. Developing superhydrophobic and superhydrophilic surfaces are originally inspired by nature. Most common way to control the wettability of a surface is to produce functional nanocoatings on different substrates. In this work, aerosol synthesis method Liquid Flame Spray (LFS) was used for fabricating functional nanocoatings on paperboard, wood and glass substrates. Superhydrophobic and superhydrophilic nanocoatings have been previously produced by LFS method, but in this work the structure of the nanocoating was researched more closely to gain better understanding of the stability of the coating. Furthermore, minimum amount of coating for wettability modification was determined. Wettability of a surface was significantly changed even if the surface was only partly covered with nanoparticles. Stability and wear resistance of functional nanocoatings is generally quite poor, so this was one of the research topics of this work. Stability of a coating depends on the adhesion and cohesion of the coating. Adhesion describes the interaction between a coating and a substrate and cohesion describes particle-to-particle interactions in the coating layer. This work focused on improving the cohesion of the nanocoatings by modifying the material composition of produced nanoparticles. Previously superhydrophobic TiO2 nanocoatings have been fabricated by LFS, but in this work TiO2 nanocoating was doped with SiO2, to improve the cohesion between agglomerated nanoparticles. Cohesion was successfully improved without losing the desired porosity or wetting properties. LFS method was also combined with other coating methods. By combining LFS with other coating methods, superamphiphobic behavior was achieved, meaning that nanocoated surface repelled also other liquids than water. Nanoparticle layer formed optimal, porous layer on a surface and nanoparticle layer was afterwards modified by plasma treatment or chemical vapor deposition to obtain needed chemical composition of the coating. By combining different coating methods, excellent repellency for water, olive oil, ethylene glycol (EG), diiodomethane (DIM) and n-Hexadecane was observed. Stability of multicomponent coatings was tested with thousands of water droplets and coating remained unharmed. This indicates relatively good adhesion and cohesion of the multicomponent coatings

Application of superhydrophobic coatings as a corrosion barrier : a review

This review provides an overview of recent advances in the application of superhydrophobic surfaces to act as corrosion barriers. The adverse consequences of corrosion are a serious and widespread problem resulting in industrial plant shutdowns, waste of valuable resources, reduction in efficiency, loss or contamination of products, and damage to the environment. Superhydrophobic surfaces, inspired by nature, can be considered as an alternative means for improving the protection of metals against corrosion. Due to the possibility of minimizing the contact area between liquids and a surface, superhydrophobic surfaces can offer great resistance to corrosion. Artificial superhydrophobic surfaces have been developed with the potential of being applied in numerous settings including self-cleaning, anti-icing, oil-water separation, and especially anti-corrosion applications. In this paper, we review the concept of superhydrophobicity through presentation of different theoretical models. The fabrication and application of superhydrophobic surfaces are presented, and we then discuss the use of superhydrophobic coatings as barriers against the corrosion of metals