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Articles 1 - 10 of 10
Full-Text Articles in Complex Fluids
Towards Long Term Colloid Suspension In A Vertically Rotated System., Md Mahmudur Rahman
Towards Long Term Colloid Suspension In A Vertically Rotated System., Md Mahmudur Rahman
Electronic Theses and Dissertations
Within a colloidal suspension gravity may compromise the observation of governing physical interactions, especially those that are weak and/or take significant time to develop. Conducting the experiment in a long-term microgravity environment is a viable option to negate gravitational effects, though significant resources are required to do so. While it may not be possible to simulate long-term microgravity terrestrially, particles can resist quick sedimentation in a confined suspension system rotating vertically with appropriate rotation speed. The goal of the investigation is to demonstrate the existence of long-term particle suspension regime for a certain colloidal suspension while characterizing colloidal behavior due …
Wetting And Drying Dynamics For Tio2 With Pbs Quantum Dots., Kelly M. Lee
Wetting And Drying Dynamics For Tio2 With Pbs Quantum Dots., Kelly M. Lee
Electronic Theses and Dissertations
Initial solar cells utilized silicon and alloys for their economic viability. Photoelectrochemical photovoltaic cells were discovered with technological advancement which increased solar efficiency and further improved economic feasibility leading to quantum dot sensitized solar cells. Lead sulfide quantum dots and titanium dioxide were studied for wetting and drying effects. Zeta potential, pH values, SEM, and optical microscopes quantified or observed the colloidal suspension and dried sample behavior. Combined mixtures of lead sulfide and titania were dried at 3.6 pH and 12.56 pH values. This due to the observed zeta potential isoelectric point of titania, and behavior showed increased stability occurring …
Aggregation Dynamics Of Bulk Nanoparticle Haloing Systems And The Influence Of Non-Ambient Temperatures., Marzieh Moradi
Aggregation Dynamics Of Bulk Nanoparticle Haloing Systems And The Influence Of Non-Ambient Temperatures., Marzieh Moradi
Electronic Theses and Dissertations
One of the methods of assembling colloids into 3D crystal structures is through the use of nanoparticle haloing. Nanoparticle haloing is a stabilization mechanism in binary particle suspensions possessing both a size and charge asymmetry, with which the nanoparticles aid in the bulk suspension’s stability. By altering the volume fractions of nanoparticles, it is possible to control the effective repulsion between the microparticles. Understanding the colloidal interactions and aggregate crystallinity as a function of nanoparticle concentration, temperature, and time are key challenges in developing future materials and designing crystalized 3D colloidal systems. In this study, we investigated the effect of …
Image Analysis Of Charged Bimodal Colloidal Systems In Microgravity., Adam J. Cecil
Image Analysis Of Charged Bimodal Colloidal Systems In Microgravity., Adam J. Cecil
Electronic Theses and Dissertations
Colloids are suspensions of two or more phases and have been topics of research for advanced, tunable materials for decades. Stabilization of colloids is typically attributed to thermodynamic mechanisms; however, recent studies have identified transport or entropic mechanisms that can potentially stabilize a thermodynamically unstable colloidal system. In this study, suspensions of silsesquioxane microparticles and zirconia nanoparticles were dispersed in a nitric acid solution and allowed to aggregate for 8-12 days in microgravity aboard the International Space Station. The suspensions were subsequently imaged periodically at 2.5x magnification. Due to the inadequacy of existing image analysis programs, the python package “Colloidspy” …
Non-Invasive Detection And Assessment Of Coronary Stenosis From Blood Mean Residence Times., Javad Hashemi
Non-Invasive Detection And Assessment Of Coronary Stenosis From Blood Mean Residence Times., Javad Hashemi
Electronic Theses and Dissertations
Coronary artery stenosis is an abnormal narrowing of a coronary artery caused by an atherosclerotic lesion that reduces lumen space. Fractional flow reserve (FFR) is the gold standard method to determine the severity of coronary stenosis based on the determination of rest and hyperemic pressure fields, but requires an invasive medical procedure. Normal FFR is 1.0 and FFR RT, to account for varying volume and flow rate of individual segments. BloodRT was computed in 100 patients who had undergone the pressure-wire FFR procedure, and a threshold for BloodRT was determined to assess the physiological significance of a stenosis, …
Stabilization Of Bimodal Colloidal Systems Via Nanoparticle Haloing In Microgravity., Luke Hawtrey
Stabilization Of Bimodal Colloidal Systems Via Nanoparticle Haloing In Microgravity., Luke Hawtrey
Electronic Theses and Dissertations
Colloidal suspensions typically contain a multi-phase system of solid particles suspended in a liquid medium. Colloids are widely used in industrial applications such as inks, paints, motor oils, foods, cosmetics, and many more. Colloidal systems are typically formed by the interaction of the attractive van der Waals forces and one or more repulsive forces. These repulsive forces include electrostatic repulsion, steric hindrance, and nanoparticle haloing. Nanoparticle Haloing (NPH) is a phenomenon discovered in 2001 as a viable method to stabilize colloidal systems of uncharged silica microparticles using highly charged zirconia nanoparticles. For this thesis the effects of NPH were tested …
Fluid Flow Analysis Of Diluted Evaporating American Whiskey Droplets., Martin J. Brown Vi
Fluid Flow Analysis Of Diluted Evaporating American Whiskey Droplets., Martin J. Brown Vi
Electronic Theses and Dissertations
The recent discovery of the unique structures, whiskey webs, formed when the evaporation of diluted American whiskey, has raised many questions as to the nature of the structures. Their formation process follows as such: (1) dilution of the whiskey to form nanoaggregates, (2) formation of a monolayer at the air-liquid interface, (3) chaotic ethanol evaporation caused monolayer collapse (via dynamic pressure), (4) bulk fluid evaporation caused monolayer collapse (via reduction of surface area), where the web-like structures reside on the surface, and finally, (5) web-like structures deposit on the substrate. The webs imaged via SEM had a striking resemblance to …
Viscoelastic Roll Coating Flows, Mitchell A. Johnson
Viscoelastic Roll Coating Flows, Mitchell A. Johnson
Electronic Theses and Dissertations
The physics of a fluid flow between two rotating cylinders is important in processes such as bearing lubrication, roll coating, and printing. A small amount of dissolved polymer in the fluid can have a large impact on the behavior of the process. Viscoelasticity affects the stability of application and metering processes, and reduces the maximum speed at which a uniform film can be coated onto a substrate. The goal of this work is to characterize the effect of viscoelasticity on the forward roll coating operation. A bench-top apparatus simulated the process. Measurements of the gap between the roll surfaces, pressure …
Characterization Of Chitosan Films For Cell Culture Applications, Michael Katalinich
Characterization Of Chitosan Films For Cell Culture Applications, Michael Katalinich
Electronic Theses and Dissertations
Chitosan (β-(l,4)-2-amino-2-deoxy-D-glucose) is a naturally occurring, abundant biopolymer exhibiting desirable biomaterial properties of biodegradability, low toxicity and good biocompatibility. These properties indicate the suitability of chitosan as a surface for mammalian cell growth. The goal of this thesis is to explore the potential for using chitosan as a surface for NIH 3T3 fibroblast attachment and growth. '4 standard, reproducible film-formation technique, based on other researchers techniques was established. The reproducibility of this technique. through characterization of the physical and chemical properties of these films, was good. The attachment and growth of NIH 3T3 fibroblasts on chitosan films and controls was …
Bubble Growth Behavior In Supersaturated Liquid Solutions, David Robert Cyr
Bubble Growth Behavior In Supersaturated Liquid Solutions, David Robert Cyr
Electronic Theses and Dissertations
The growth characteristics of gas bubbles in supersaturated liquid solutions were measured in preliminary experiments involving glass bottles followed by more controlled and systematic investigations using a custom designed experimental apparatus. It was proven that the presence of pre-existing gas was responsible for the bubble formation observed. Bubble growth occurred in very regular cyclical patterns at specific locations containing trapped gases. In the custom designed apparatus, liquids could be saturated with gases and supersaturated solutions made by depressurizing the system. Artificial capillaries, pre-seeded with air bubbles, behaved in a similar manner to naturally occurring sites containing pre-existing gases. The apparent …