Prediction of pressure drop in vertical airwater flow in the presenceabsence of sodium dodecyl sulfate as a surfactant

The aim of this thesis is to develop a better approach for predicting pressure gradient in vertical multiphase flow with and without use of Sodium dodecyl sulfate (SDS) as a surfactant and to develop a program for the prediction of pressure drop by using Microsoft Visual Basic in Excel. Data was collected from four fixed liquid superficial velocity at different ranges of gas superficial velocity in a 0.052m i.d. and 10m long, clear PVC pipe. Results indicate that the addition of SDS resulted in reducing surface tension between phases from 72 to 64 mN/m, decreasing pressure drop by approximately 26% and also Hasan and Kabir model for Air/DI water and Hagedorn and Brown model in the presence of SDS in the mixture is the best model and leads to a reasonably accurate pressure gradient according to measured pressure drop

CONTROLLING THE MORPHOLOGY OF POLYMER BLENDS USING THE NONLINEAR OPTICAL PROPERTIES OF LIGHT

Nonlinear optics and polymer systems are distinct fields that have been studied for decades. These two fields intersect with the observation of nonlinear wave propagation in photoreactive polymer systems. Combining nonlinear pattern formation mechanisms to polymer systems is attractive for directing materials synthesis. This has led to studies on the nonlinear dynamics of transmitted light in polymer media, particularly for optical self-trapping and optical modulation instability. The irreversibility of polymerization leads to permanent capture of nonlinear optical patterns in the polymer structure, which is a new synthetic route to complex structured soft materials. This dissertation discusses the work to date on nonlinear optical pattern formation processes in polymers. A brief overview of the nonlinear optical phenomenon is provided to set the stage for understanding their effects. We review the accomplishments of the field on studying nonlinear waveform propagation in photopolymerizable systems, then discuss our most recent progress in coupling nonlinear optical pattern formation to polymer blends and phase separation. We demonstrate how morphology evolution and phase separation in polymer blends can be controlled through irradiation with arrays of self-trapping of optical beams. We studied the effects of different weight fractions and exposure intensities on morphology evolution during photopolymerization. An in situ microscopy experiments were conducted to elucidate the nature of the phase separation behavior and morphology evolution in a blended system. In situ confocal Raman measurements of polymer conversion were done to obtain better understating of the kinetics and formation dynamics associated with phase separation induced by self-trapped light. Control over morphology depends strongly on the competitive processes of phase separation and photo-crosslinking. Our findings demonstrate a fundamentally new approach to the patterning of polymer blends, which is important for controlling their critical physical phenomenon and establishing advanced structure-property relationships. The fabrication of a new type of solar cell encapsulation architecture comprising a periodic array of step-index waveguides is reported. The materials are fabricated through patterning with light in a photoreactive binary blend of crosslinking acrylate and urethane, wherein phase separation induces the spontaneous, directed formation of broadband, cylindrical waveguides. This microstructured material efficiently collects and transmits optical energy over a wide range of entry angles. Silicon solar cells comprising this encapsulation architecture show greater total external quantum efficiencies and enhanced wide-angle light capture and conversion. This is a rapid, straightforward, and scalable approach to process light-collecting structures, whereby significant increases in cell performance may be achieved. We present a new approach to synthesize microporous surfaces through the combination of photopolymerization-induced phase separation and light pattern formation in photopolymer-solvent mixtures. The mixtures are irradiated with a wide-area light pattern consisting of high and low-intensity regions. This light pattern undergoes self-focusing and filamentation, thereby preserving its spatial profile through the mixture. Over the course of irradiation, the mixture undergoes phase separation, with the polymer and solvent located in the bright and dark regions of the light profile, respectively, to produce a binary phase morphology with a congruent arrangement as the optical pattern. A congruently-arranged microporous structure is attained upon solvent removal. The microporous surface structure can be varied by changing the irradiating light profile via photomask design. The porous architecture can be further tuned through the relative weight fractions of photopolymer and solvent in the mixture, resulting in porosities ranging from those with discrete and uniform pore sizes to hierarchical pore distributions. All surfaces become superhydrophobic (water contact angles \u3e 150) when spray-coated with a thin layer of polytetrafluoroethylene nanoparticles. The water contact angles can be enhanced by changing the surface porosity via the processing conditions. This is a scalable and tunable approach to precisely control microporous surface structure in thin-films to create functional surfaces and anti-wetting coatings

Prediction of pressure drop in vertical airwater flow in the presenceabsence of sodium dodecyl sulfate as a surfactant

The aim of this thesis is to develop a better approach for predicting pressure gradient in vertical multiphase flow with and without use of Sodium dodecyl sulfate (SDS) as a surfactant and to develop a program for the prediction of pressure drop by using Microsoft Visual Basic in Excel. Data was collected from four fixed liquid superficial velocity at different ranges of gas superficial velocity in a 0.052m i.d. and 10m long, clear PVC pipe. Results indicate that the addition of SDS resulted in reducing surface tension between phases from 72 to 64 mN/m, decreasing pressure drop by approximately 26% and also Hasan and Kabir model for Air/DI water and Hagedorn and Brown model in the presence of SDS in the mixture is the best model and leads to a reasonably accurate pressure gradient according to measured pressure drop

Simulations of Morphology Evolution in Polymer Blends during Light Self-Trapping

Simulations are presented for binary phase morphologies prepared via coupling the self-trapping properties of light with photopolymerization induced phase separation in blends of reactive monomer and inert linear chain polymer. The morphology forming process is simulated based on a spatially varying photopolymerization rate, dictated by self-trapped light, coupled with the Cahn–Hilliard equation that incorporates the free energy of polymer mixing, degree of polymerization, and polymer mobility. Binary phase morphologies form with a structure that spatially correlates to the profile of the self-trapped beam. Attaining this spatial correlation emerges through a balance between the competitive processes entailed in photopolymerization-induced decreases in diffusion mobility and the drive for the blend components to phase separate. The simulations demonstrate the ability for a self-trapped optical beam to direct binary phase morphology along its propagation path. Such studies are important for controlling the structure of polymer blends, whereby physical properties and critical physical and chemical phenomena may be enhanced

A Computational Study on the Ca2+ Solvation, Coordination Environment, and Mobility in Electrolytes for Calcium Ion Batteries

Calcium (ion) batteries are promising next-generation energy storage systems, owing to their numerous benefits in terms of performance metrics, low-cost, mineral abundance, and economic sustainability. A central and critical area to the advancement of the technology is the development of suitable eletrolytes that allow for good salt solubility, ion mobility, electrochemical stability, and reversible redox activity. At this time, the study of different solvent-salt combinations is very limited. Here, we present a computational study on the coordination environment, solvation energetics, and diffusivity of calcium ions over a range of pertinent ionic liquids, cyclic and acylic alkyl carbonates, and specific alkyl nitriles and alkyl formamides, using the salts calcium bis(trifluoromethylsulfonyl)imide (Ca(TFSI)2) and calcium perchlorate (Ca(ClO4)2). Key findings are that several solvents from different solvent classes present comparable solvation environments and mobilities. Ca(TFSI)2 is prefered over Ca(ClO4)2 owing to the former’s mix coordination of Ca2+ to O and N atoms. Ionic liquids with alkyl sulfonate anions provide better coordation over TFSI, which leads to greater diffusivity. Binary organic mixtures (carbonates) provide the best solvation of Ca2+, however, single organic solvents also provide good solvation, such as EC, THF and DMF, as well as some acyclic carbonates. Ion pairing with the salt anion is always present, but can be mitigated through solvent selection, which also correlates to greater mobility; however, there are examples in which strong ion pairing is not significantly adverse to diffusivity. The solvent incorporate into the solvation structure with binary organic mixtures correlates well with the solvation capabilities of the individual solvents. Finally, we show that ionic liquids (specifically alkyl imidazole (cation) alkyl sulfonate (anion) ionic liquids) do not decompose when coordinating at a Ca metal interface, which indicates its promising stability. Overall, this study contributes further generalized understanding of the correlation between solvent and salt and the resultant Ca2+ complexes and Ca2+ mobility in a range of electrolytes, and reveals a range of possible solvents suitable for exploration in calcium (ion) batteries

Control of Morphology in Polymer Blends through Light Self-Trapping: An <i>in Situ</i> Study of Structure Evolution, Reaction Kinetics, and Phase Separation

We report on how polymer morphology is controlled through the self-trapping of transmitted optical beams in photoreactive polymer blends. Self-trapped optical beams, characterized by divergence-free propagation, drives the growth of a congruent arrangement of polymer filaments in the blends. With suitable component weight fractions and exposure intensity, binary phase morphologies form in precisely the same pattern as the beams’ arrangement, thereby producing 2D structures in polymer blend volumes of large depth and area. Morphology evolution and the formation processes were observed by <i>in situ</i> microscopy. <i>In situ</i> confocal Raman measurements of polymer conversion and molecular weight increase along the filament regions reveal that polymerization undergoes autoacceleration, followed by the onset of mixing instability which leads to phase separation. These phenomena begin at the front end of the filament and propagate along its length over the depth of the blend. Control over morphology is discussed with respect to the competitive processes of phase separation and photo-cross-linking

A solid polymer electrolyte for aluminum ion conduction

We report on the synthesis and characterization of a solid polymer electrolyte for aluminum ion conduction. The solid polymer electrolyte is produced via the copolymerization of a low molecular weight polytetrahydrofuran and a cycloaliphatic epoxy. The crosslinked copolymer is swollen in THF solutions of different concentrations of aluminum nitrate as the aluminum ion source. The conductivity as a function of concentration is measured via AC impedance spectroscopy over a temperature range of 20–110 °C. We attain conductivities that increase with salt loading, reaching a value of 2.86 × 10−5 S·cm−1. Thermogravimetric analysis shows the electrolytes are stable up to 150 °C. Raman spectroscopy reveals complete dissociation of the aluminum nitrate salt in the electrolyte over the concentration range explored. This study establishes a polymer system and synthetic route towards solid polymer electrolytes for aluminum ion conduction, for the development of all solid-state aluminum ion batteries. Keywords: Polymers, Electrolyte, Aluminum, Ion conductio

Synthesis of Micropillar Arrays via Photopolymerization: An in Situ Study of Light-Induced Formation, Growth Kinetics, and the Influence of Oxygen Inhibition

We report a study on the growth kinetics and resultant structures of arrays of pillars in photo-cross-linkable films during irradiation with a periodic array of microscale optical beams under ambient conditions. The optical beams experience a self-focusing nonlinearity owing to the photopolymerization-induced changes in refractive index, thereby concentrating light and driving the concurrent, parallel growth of microscale pillars along their path length. We demonstrate control over the pillar spacing and pillar height with the irradiation intensity, film thickness, and the size and spacing of the optical beams. The growth of individual pillars in a periodic array arises from the combination of intense irradiation in the beam regions and oxygen inhibition afforded by the open, ambient conditions under which growth is carried out. We propose a kinetic model for pillar growth that includes free-radical generation and oxygen inhibition in thick films of photoinitiated media in order to interpret the experimental results. The model effectively correlates micropillar array structure to the oxygen inhibition effects. This approach of growing micropillar arrays through photopolymerization is straightforward and scalable and opens opportunities for the design of textured surfaces for applications

Optical Autocatalysis Establishes Novel Spatial Dynamics in Phase Separation of Polymer Blends during Photocuring

We report a fundamentally new nonlinear dynamic system that couples optical autocatalytic behavior to phase evolution in photoreactive binary polymer blends. Upon exposure to light, the blend undergoes spontaneous patterning into a dense arrangement of microscale polymer filaments. The filaments’ growth in turn induces local spinodal decomposition of the blend along their length, thereby regulating the spatially dynamics of phase separation. This leads to the spontaneous organization of a large-scale binary phase morphology dictated by the filament arrangement. This is a new mechanism for polymer blend organization, which couples nonlinear optical dynamics to chemical phase separation dynamics, and offers a new approach to light-directed patterning and organization of polymer and hybrid blends