Browsing by Subject "Surface tension"
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Item A study of interfacial tension in ternary systems(Texas Tech University, 1966-05) Prochaska, Frank OttoInterfacial tensions were determined for the five ternary systems water-isopropyl alcohol-benzene, water-isopropyl alcohol-toluene, water-tertiary butyl alcohbl-benzene, water-normal propyl alcohol-toluene, and water-dlethylamlne-toluene in their regions of two liquid phases. Also determined were surface tensions, densities, and refractive indices of the phases. A Fisher Surface Tensiometer employing the ring method was used to make the surface and interfacial tension determinations. A Fisher- Davidson Gravltometer was used to make the density measurements and refractive indices were determined by means of a Bausch and Lomb Abbe-3L Refractometer. A comparison was made of the values determined for the binary and pure liquid phases of the above ternary systems with the accepted values found in the literature. A maximum deviation of 2.81 was indicated. As the other measurements were made under the same conditions all values determined were considered to be in error by no more than 2.8%. A relative immiscibility scale was established for each system by means of the differences of the refractive indices of the conjugate phases. Interfacial tensions of each of the systems were correlated against the corresponding immicibilities established for the phases. A straight line function was indicated for plots of the immiscibility values against the log of the log of one hundred times the interfacial tensions. Correlation coefficients determined for the curves showed a 951 certainty of this type of correlation for one of the systems, a 981 certainty for another, and 991 certainties for the remaining three systems.Item Adhesion of particles on indoor flooring materials(2007-12) Lohaus, James Harold, 1968-; Siegel, Jeffrey A.This dissertation involved a theoretical and experimental investigation of the adhesive forces between spherical particles of four different diameters and two selected flooring materials under different air velocities. Previous theoretical work and experiments described in the literature tended to be conducted with idealized surfaces, and therefore have limited applicability to indoor environments. Controlled experiments were designed, constructed and executed to measure the air velocity required to overcome adhesion forces. The diameters of the particles investigated were 0.5, 3.0, 5.0 and 9.9 [mu]m, and the flooring materials were linoleum and wooden flooring. The critical velocity, the flow at which 50% of the particles detached, is presented as a function of particle diameter for each surface. The measured values were then compared to empirical and theoretical models as well as to a scaling analysis that considers component forces that act on a particle-surface system. The results suggest that critical velocity decreases with increasing particle diameter and that existing models have limited applicability to resuspension from flooring materials.Item Aggregation behavior of ionic liquids in aqueous solution studied by physical methods(2012-08) Gao, Qianqian; Quitevis, Edward L.; Thompson, Jonathan E.; Pappas, DimitriThe role of ILs as a surface active agents needs to be fully understood. Based on the previous work, we characterized the micellization of 1-alkyl-3-methyl-limidazolium bromide ([Cnmim][Br], for n = 8, 10, 12, 14, 16), and 1,3-dialkyl imidazolium bromide ([(Cn)2im][Br], for n = 8, 10, using pyrene fluorescence, surface tension, and conductivity measurements; the aggregation numbers of micelles in water were also obtained using the fluorescence quenching technique. The contact angle of the IL solution on the silicon wafer was measured and analyzed. The data obtained gave a more comprehensive understanding about the micelle formation process of these ILs. Information about the micro-polarity in the micelle interior region, packing density of the ILs in the micelle phase, growth of the micelle with the concentration, absorbance of ILs at the interface, etc. were obtained. The symmetry effect on the aggregation behavior of the two structurally related IL groups was studied. The symmetric ILs behave very differently from the asymmetric ILs due to their distinct structure.Item Development of an inhalational formulation of Coenzyme Q₁₀ to treat lung malignancies(2011-12) Carvalho, Thiago Cardoso; McConville, Jason ThomasCancer is the second leading cause of death in the United States and its onset is highly incident in the lungs, with very low long-term survival rates. Chemotherapy plays a significant role for lung cancer treatment, and pulmonary delivery may be a potential route for anticancer drug delivery to treat lung tumors. Coenzyme Q₁₀ (CoQ₁₀) is a poorly-water soluble compound that is being investigated for the treatment of carcinomas. In this work, we hypothesize that formulations of CoQ10 may be developed for pulmonary delivery with a satisfactory pharmacokinetic profile that will have the potential to improve a pharmacodynamic response when treating lung malignancies. The formulation design was to use a vibrating-mesh nebulizer to aerosolize aqueous dispersions of CoQ₁₀ stabilized by phospholipids physiologically found in the lungs. In the first study, a method was developed to measure the surface tension of liquids, a physicochemical property that has been shown to influence the aerosol output characteristics from vibrating-mesh nebulizers. Subsequently, this method was used, together with analysis of particle size distribution, zeta potential, and rheology, to further evaluate the factors influencing the capability of this nebulizer system to continuously and steadily aerosolize formulations of CoQ₁₀ prepared with high pressure homogenization. The aerosolization profile (nebulization performance and in vitro drug deposition of nebulized droplets) of formulations prepared with soybean lecithin, dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC) and distearoylphosphatidylcholine (DSPC) were evaluated. The rheological behavior of these dispersions was found to be the factor that may be indicative of the aerosolization output profile. Finally, the pulmonary deposition and systemic distribution of CoQ₁₀ prepared as DMPC, DPPC, and DSPC dispersions were investigated in vivo in mice. It was found that high drug amounts were deposited and retained in the mouse lungs for at least 48 hours post nebulization. Systemic distribution was not observed and deposition in the nasal cavity occurred at a lower scale than in the lungs. This body of work provides evidence that CoQ₁₀ may be successfully formulated as dispersions to be aerosolized using vibrating-mesh nebulizers and achieve high drug deposition in the lungs during inhalation.Item Flow patterns and instabilities in two-phase down flow in packed beds(Texas Tech University, 1978-12) Halfacre, GlennNot availableItem Identification and characterization of non-flammable azeotropic mixtures for precision cleaning(2017-04-18) Perry, Jacob; Williams, Darren L.; Gross, Dustin E.; Thompson, David E.The goal of this thesis is to provide methods that can be used to search for new azeotropes with specific desired properties, and methods to characterize these new azeotropes. All azeotrope possibilities that were examined in this study were low-boiling azeotropes composed of non-aqueous solvents, and the desired properties were for the azeotropes to be non-flammable and have good solvency against hydrocarbon grease. In this study, azeotropes were formed for use in cleaning applications, specifically vapor degreasing. For cleaning applications, the most important quality of the azeotrope is solvency. However, in a vapor degreaser flammability is an issue. To obtain the desired solvency in an azeotrope, the Hansen Solubility Parameters (HSPs) were used to decide what solvents were good candidates. However, the solvents that were found from this search were flammable. In an attempt to get the desired properties, the solvents were paired with non-flammable solvents that had similar boiling points to obtain a blend with good solvency and no flammability. Then, these pairs were mixed and distilled to identify whether the pairs formed low-boiling azeotropes. The resulting azeotropes were characterized by obtaining their boiling point, flash point, thermal expansion coefficient, surface tension, density, viscosity and composition. The boiling points were obtained from the distillation process. The flash points were found using a modified ASTM D56 method. Thermal expansion coefficients were obtained through the dependence of the density on temperature. The surface tension and density were obtained using a DuNouy ring tensiometer. Viscosity was found using a ball drop viscometer. Finally, the composition was found using Raman spectroscopy. All these standard procedures can be found in the appendix. A solubility parameter-based model for predicting azeotropic behavior in binary mixtures was explored as an extension of the results of this thesis work. The goal of this model is to predict the likelihood that a given pair of solvents will form a low-boiling azeotrope. Such a model would save time in the laboratory, reduce personnel exposure, and reduce waste by steering the researchers away from unpromising mixtures that are unlikely to form azeotropes.Item Mass transfer area of structured packing(2010-05) Tsai, Robert Edison; Eldridge, R Bruce; Rochelle, Gary T.; Bonnecaze, Roger T.; McGlamery, Gerald G.; Seibert, A Frank; Truskett, Thomas M.The mass transfer area of nine structured packings was measured as a function of liquid load, surface tension, liquid viscosity, and gas rate in a 0.427 m (16.8 in) ID column via absorption of CO₂ from air into 0.1 mol/L NaOH. Surface tension was decreased from 72 to 30 mN/m via the addition of a surfactant (TERGITOL[trademark] NP-7). Viscosity was varied from 1 to 15 mPa·s using poly(ethylene oxide) (POLYOX[trademark] WSR N750). A wetted-wall column was used to verify the kinetics of these systems. Literature model predictions matched the wetted-wall column data within 10%. These models were applied in the interpretation of the packing results. The packing mass transfer area was most strongly dictated by geometric area (125 to 500 m²/m³) and liquid load (2.5 to 75 m³/m²·h or 1 to 30 gpm/ft²). A reduction in surface tension enhanced the effective area. The difference was more pronounced for the finer (higher surface area) packings (15 to 20%) than for the coarser ones (10%). Gas velocity (0.6 to 2.3 m/s), liquid viscosity, and channel configuration (45° vs. 60° or smoothed element interfaces) had no appreciable impact on the area. Surface texture (embossing) increased the area by 10% at most. The ratio of effective area to specific area (a[subscript e]/a[subscript p]) was correlated within limits of ±13% for the experimental database: [mathematical formula]. This area model is believed to offer better predictive accuracy than the alternatives in the literature, particularly under aqueous conditions. Supplementary hydraulic measurements were obtained. The channel configuration significantly impacted the pressure drop. For a 45°-to-60° inclination change, pressure drop decreased by more than a factor of two and capacity expanded by 20%. Upwards of a two-fold increase in hold-up was observed from 1 to 15 mPa·s. Liquid load strongly affected both pressure drop and hold-up, increasing them by several-fold over the operational range. An economic analysis of an absorber in a CO₂ capture process was performed. Mellapak[trademark] 250X yielded the most favorable economics of the investigated packings. The minimum cost for a 7 m MEA system was around $5-7/tonne CO₂ removed for capacities in the 100 to 800 MW range.Item Nanofabrication via directed assembly: a computational study of dynamics, design & limits(2016-08) Arshad, Talha Ali; Bonnecaze, R. T. (Roger T.); Ellison, Christopher J.; Ganesan, Venkat; Sreenivasan, S. V.; Willson, Carlton G.Three early-stage techniques, for the fabrication of metallic nanostructures, creation of controlled topography in polymer films and precise deposition of nanowires are studied. Mathematical models and computational simulations clarify how interplay of multiple physical processes drives dynamics, provide a rational approach to selecting process parameters targeting specific structures efficiently and identify limits of throughput and resolution for each technique. A topographically patterned membrane resting on a film of nanoparticles suspended in a solvent promotes non-uniform evaporation, driving convection which accumulates particles in regions where the template is thin. Left behind is a deposit of particles the dimensions of which can be controlled through template thickness and topography as well as film thickness and concentration. Particle distribution is shown to be a competition between convection and diffusion represented by the Peclet number. Analytical models yield predictive expressions for bounds within which deposit dimensions and drying time lie. Ambient evaporation is shown to drive convection strong enough to accumulate particles 10 nm in diameter. Features up to 1 µm high with 10 nm residual layers can be deposited in < 3 minutes, making this a promising approach for continuous, single-step deposition of metallic nanostructures on flexible substrates. Selective exposure of a polystyrene film to UV radiation has been shown to result in non-uniform surface energy which drives convection on thermal annealing, forming topography. Film dynamics are shown to be a product of interplay between Marangoni convection, capillary dissipation and diffusion. At short times, secondary peaks form at double the pattern density of the mask, while at long times pattern periodicity follows the mask. Increased temperature, larger surface tension differentials and thick films result in faster dynamics and larger features. Electric fields in conjunction with fluid flow can be used to position semi-conducting nanowires or nanotubes at precise locations on a substrate. Nanowires are captured successfully if they arrive within a region next to the substrate where dielectrophoresis dominates hydrodynamics. Successful assembly is predicated upon a favorable balance of hydrodynamics, dielectrophoresis and diffusion, represented by two dimensionless groups. Nanowires down to 20 nm in length can be assembled successfully.Item Parallel adaptive finite element methods for problems in natural convection(2008-05) Peterson, John William, Ph. D.; Carey, Graham F.Numerical simulations of combined buoyant and surface tension driven flow, also known as Rayleigh-Bénard-Marangoni (RBM) convection are conducted for heated fluid layers of small aspect ratio (defined as the ratio of the horizontal extent of the domain divided by the depth of the fluid) in square cross-section containers. A particular non-dimensionalization of the governing equations is developed in which the aspect ratio of the domain appears as a continuous parameter. The simulations extend and enhance existing experimental studies of the RBM convection phenomenon by mapping continuous solution branches in aspect ratio and Marangoni number parameter space. Key implementation aspects of the development of the adaptive mesh refinement (AMR) library libMesh are discussed, and a series of simulations of the RBM problem with a stick-slip boundary condition demonstrate the suitability of AMR for computing these flows.