Moisture damage in asphalt mixes can be defined as loss of strength and durability due to the presence of moisture at the binder-aggregate interface (adhesive failure) or within the binder (cohesive failure). This research focuses on the evaluation of the susceptibility of aggregates and asphalts to moisture damage through understanding the micro-mechanisms that influence the adhesive bond between aggregates and asphalt and the cohesive strength and durability of the binder. Moisture damage susceptibility is assessed using surface energy measurements and dynamic mechanical analysis (DMA). Surface energy is defined as the energy needed to create a new unit surface area of material in vacuum condition. Surface energy measurements are used to compute the adhesive bond strength between the aggregates and asphalt and cohesive bond strength in the binder. DMA testing is used to evaluate the rate of damage accumulation in asphalt binders and mastics. The DMA applies a cyclic, torsional strain controlled loading to cylindrical asphalt mastics until failure. The DMA results are analyzed using continuum damage mechanics that focuses on separating the energy expended in damaging the material from that associated with viscoelastic deformation. A new approach is developed to analyze the DMA results and calculate the rate of damage. The developed approach is used to evaluate six asphalt mixtures which have performed either well or poorly in the field. The resistance of the field mixes to moisture damage is shown to be related to the calculations of bind energies and the accumulated damage in the DMA.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (p. 107-112).

Thesis (M.S.)--University of North Texas, Aug., 2009. / Title from title page display. Includes bibliographical references.

The goal of this project was to advance adhesion science and technology related to the Australian hardwood spotted gum (Corymbia citriodora). Plantation-grown spotted gum exhibits poor adhesion properties in comparison with similar woods, such as Gympie messmate (Eucalyptus cloeziana). To better understand adhesion differences between these two woods, this research compared and contrasted the surface chemistries of plantation-grown spotted gum and Gympie messmate with a particular focus on sensitivity to thermal deactivation. Wetting measurements were performed using the sessile drop method. Initial and equilibrium contact angles, time-dependent wetting, and surface energy were determined. Time-dependent wetting and equilibrium contact angles were most informative. Initial contact angles and surface energy calculated with them were misleading and often generated anomalous results. Heating water-saturated wood to mild surface temperatures (105 deg C, directly after evaporative cooling) severely deactivated spotted gum but not Gympie messmate. This suggests conventional kiln drying appears unsuitable for spotted gum while amenable for Gympie messmate. Spotted gum likely requires non-aqueous, low surface tension adhesives or aqueous adhesives formulated with surface active wetting agents. Water-saturation (followed by room-temperature vacuum drying) substantially altered the surface chemistries of both woods, making them more hydrophilic. Consequently, the question was raised of whether a water-spray onto the wood surface prior to adhesive application could improve bonding. If so, this simple, industrially-feasible treatment could prove very beneficial to the wood composites industry. Water-saturation also revealed differences in the two wood's water permeability, which has implications for adhesive penetration and wood drying and may additionally help explain adhesion differences. Analysis of the plantation-grown heartwood (inner, middle, and outer heartwood regions) revealed significant wetting differences on spotted gum with only minor differences on Gympie messmate. The Australian woods were compared to two North American woods-loblolly pine (Pinus taeda) and Douglas-fir (Pseudotsuga menziesii). Examining water wetting measurements, the Australian and North American woods exhibited some interesting similarities. However, methylene iodide wetting measurements revealed that the Australian woods were quite different from the North American samples studied here. / Master of Science

In this study, the behavior of partially saturated coarse-grained soil packings was studied as a function of solid surface composition and aqueous salt concentration. The substrates tested were PTFE and soda lime glass, while the aqueous electrolytes consisted of NaCl and CaCl2 in differing concentrations. In order to gain a fundamental understanding of the unsaturated soils system, the two phase intersections of gas-liquid and solid-liquid were studied. The effect of varying aqueous electrolytes on the gas-liquid interface was analyzed by testing the surface tension while systematically varying the electrolyte concentration, while the effect on the solid/liquid/gas interface was studied by altering the surface hydrophobicity and aqueous solution concentration. In order to extend the analysis to soil fabrics, four ideal coarse gained packings were subdivided into their smallest repeating units. These repeating units, along with the measured dependence of the contact angles and surface tension on salt types, allowed an estimation of the equilibrium behavior of the capillary rise and tensile strength within a uniform coarse-grained fabric.

As the fluidic devices are miniaturized to improve portability, the friction of the microchannel becomes intrinsically high and a high pumping power will be required to drive the fluid. Since the pumping power delivered by portable devices is limited, one method to reduce this is to render the surface to become slippery. This can be achieved by roughening up the microchannel wall and form a bed of air pockets between the roughness elements, which is known as the superhydrophobic Cassie-Baxter state. While the study on superhydrophobic microchannels are focused mainly in maximizing the friction reduction effects and maintaining the stability of the air pockets, less attention has been given to characterizing the microchannel friction under a metastable state, where partial flooding of the micro-textures may be present, and under heated conditions, where the air pockets are trapped between the micro-textures. In order to quantify the frictional characteristics, microchannels with micron-sized trenches on the side walls were fabricated and tested under varying inlet pressures and heating conditions. By measuring the hydrodynamic resistance and comparing with numerical simulations, results suggest that (1) the air-water interface behaves close to a no-slip boundary condition, (2) friction becomes insensitive to the wetting degree once the micro-trenches become highly wetting, (3) the fully wetted micro-trench may be beneficial over the de-wetted ones in order to achieve friction reduction effects and (4) heating the micro-trenches to induce a highly de-wetting state may actually be detrimental to the microchannel flow due the excessive growth of the air layer. As part of the future work to characterize heat transfer in superhydrophobic microchannels, a rectangular microchannel with microheaters embedded close to the side walls was fabricated and the corresponding heat transfer rates were measured through dual fluorescence thermometry. Results suggested that significant heat is lost through the environment despite the high thermal resistance of the microchannel material. An extra insulation is suggested prior to characterizing the convective heat transfer coefficients in the superhydrophobic microchannel flow. / text

Master of Science / Department of Apparel, Textiles, and Interior Design / Jooyoun Kim / Seong-O Choi / Superhydrophobicity (water contact angle, WCA >150˚) can be achieved by introducing surface roughness and decreasing surface energy. Polystyrene (PS) electrospun web can be used as an excellent substrate for superhydrophobic surface due to its low surface energy (~33 mN/m) and processibility to form various roughness. As the Cassie-Baxter model explains, the presence of roughness amplifies anti-wettability of materials whose surface energy is low (hydrophobic, WCA >90˚). This study aims to fabricate superhydrophobic PS nonwoven webs by electrospinning process and vapor deposition of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFDTS) and to investigate the influence of fiber morphology and surface energy on wettability. To this end, PS webs with various fiber morphologies were electrospun under different polymer concentrations and solvent mixtures. PS substrates were treated by air plasma to attach –OH groups before the vapor deposition of PFDTS. Air plasma treatment itself increased the surface energy of PS; however, with PFDTS coating, the surface energy was decreased. The wettability was characterized by WCA and sliding angle measurement. WCAs on the electrospun webs were greater than that of flat PS film (WCA=95˚) due to the increased roughness of the web. The web with beads or grooved fibers achieved superhydrophobicity (WCA>150˚). PFDTS deposition lowered the surface energy of PS surface to about 15.8 mN/m. PS web with PFDTS deposition presented high water contact angle up to 169˚ and low sliding angle about 3˚. Also it was attempted to characterize the interfacial area between water and a solid surface on irregular fibrous webs. The fraction of solid surface area wet by the liquid (solid fraction) was observed by staining the rough electrospun web with a hydrophobic fluorescent dye, coumarin. The actual solid fraction corresponded fairly well with the theoretical solid fraction calculated by the Cassie-Baxter equation, demonstrating that the treated superhydrophobic surface follows the Cassie-Baxter wetting state.

O controle da temperatura de transformação de fase gama-alfa da alumina pelo uso de aditivos iônicos tem sido alvo de diversos estudos nas ultimas décadas. No entanto, os efeitos destes aditivos são usualmente explicados considerando apenas parâmetros cinéticos e de difusão e a conseqüência destas impurezas nas energias dos polimorfos e nas energias de superfície são geralmente desconsideradas. Neste trabalho, o efeito termodinâmico do Zr, Mg e Mn na transformação gama-alfa é estudado para pós de Al2O3 preparados pelo método do precursor polimérico. Microcalorimetria de adsorção acoplada com calorimetria de dissolução de alta temperatura mostraram que os íons Zr diminuem a energia de superfície do gama-Al2O3, aumentando a estabilidade da fase de transição, que é fortemente dependente desta energia. Utilizando as mesmas técnicas, mostrou-se que o íon Mg aumenta a estabilidade termodinâmica do g-Al2O3, também aumentando a temperatura de transformação. O efeito do Mg, no entanto, foi também relacionado a efeitos cinéticos tais como a diminuição de difusão pela rede. A ação do íon Mn na diminuição da temperatura de transformação foi sugerida como fortemente relacionada a parâmetros de difusão. Vacâncias geradas pela substituição de Al3+ por Mn4+ seriam responsáveis pelo aumento do processo difusional atômico pela rede, fazendo com que o sistema atinja o tamanho crítico pré-determinado para esta reação em temperaturas mais baixas. Estas importantes conclusões abrem novas perspectivas no estudo da ação de aditivos em processos de alta temperatura, que devem ser avaliados considerando ambos efeitos termodinâmico e difusional. / The control of the gamma-alpha alumina transformation temperature using ionic additives has been the subject of several studies in the past decades. In this sense, the influence of these additives is usually explained considering only kinetic and diffusional parameters. Effects of these impurities on energetics of polymorphism and surface energies are usually disregarded. In this work, the thermodynamic effect of Zr, Mg and Mn on the gamma-alpha transformation is reported on Al2O3 powders prepared by the polymeric precursor method. Adsorption microcalorimetry coupled with high temperature oxide melt solution calorimetry showed that Zr ions dramatically decrease the surface energy of gamma-Al2O3, increasing the stability of the transition phase as which has been described to have its stability considerably related to the surface energy. By the same techniques, Mg was shown to increase the thermodynamic stability of g-alumina, also increasing the transformation temperature. The role of Mg on the control of the transformation temperature, however, was also related to kinetic factors, such as the bulk diffusion decreasing. The effect of Mn on decreasing the transformation temperature, however, was considered to be almost completely related to diffusion parameters, and vacancies generated by the substitution of Al3+ by Mn4+ would be responsible for the increase in bulk diffusion, allowing the system to reach a pre-determined critical particle size at lower temperatures. These important conclusions opened new perspectives in the role of additives in the high-temperature processes that should now on be evaluated from both thermodynamic effects and kinetics viewpoints.

<p>Since the discovery in 1977 that conjugated polymers can be doped to achieve almost metallic electronic conduction, the research field of conducting polymers has escalated, with applications such as light emitting diodes, solar cells, thin film transistors, electrochemical transistors, logic circuits and sensors. The materials can be chemically modified during their synthesis in order to tailor the desired mechanical, electronic and optical properties of the final product. Polymers are also generally possible to process from solution, and regular roll-to-roll printing techniques can therefore be used for manufacturing of electronic components on flexible substrates like plastic or paper. On top of that, the nature of conjugated polymers enables the creation of devices with novel properties, which are not possible to achieve by using inorganic materials such as silicon.</p><p>The work presented in this thesis mainly focuses on devices that utilize two rather unique properties of conducting polymers. Conducting polymers are generally electrochromic, i.e. they change color upon electrochemical oxidation or reduction, and can therefore be used as both conductor and pixel element in simple organic displays. As a result of the electrochemical reaction, some polymers also alter their surface properties and have proven to be suitable materials for organic electronic wettability switches. Control of surface wettability has applications in such diverse areas as printing techniques, micro-fluidics and biomaterials.</p><p>The aim of the thesis is to briefly describe the physical and chemical background of the materials used in organic electronic devices. Topics include molecular properties and doping of conjugated polymers, electrochromism, surface tension etc. This slightly theoretical part is followed by a more detailed explanation of device design, functionality and characterization. Finally, a glance into future projects will also be presented.</p> / ISRN/Report code: LiU-TEK-LIC-2005:50

In this study, novel bio-inks formulated with horseradish peroxidase, HRP, and some additives were successfully developed for piezoelectric inkjet application. The optimized bio-ink formulation had a reliable jetting performance and maintained the biofunctionality before and after printing. The bio-ink also demonstrated a good storage life for up to 40 days at 4 oC with a negligible loss of biofunctionality. However, it was observed that some additives used in the bio-ink for obtaining necessary operational characteristics had detrimental effects on the enzyme activity. Especially, it was found that various viscosity modifiers typically used in commercial inkjet inks significantly impaired HRP activity prior to printing. Sodium Carboxymethyl Cellulose was shown to be an effective viscosity modifier that had no adverse effect on the biological activity of the HRP enzyme. Using a confocal scanning fluorescent microscope, a method for characterizing the spatial distribution of the active enzyme within the cellulosic paper substrates after inkjet printing was developed. Interestingly, it was found that the active printed HRP enzyme was mostly located in the cell walls of the cellulosic fibers instead of near the pigments or fillers. In an effort to better understand the fundamental interactions between the enzyme and the immobilization substrates, HRP adsorption isotherms on various substrate surfaces were obtained using the depletion method. The substrates included not only pulp fibers with varying degree of hydrophobicity and pigment and latex (the key materials used in papermaking), but also other types of cellulosic fibers of different morphologies, crystallinities, porosities, or surface charge densities. The influence on enzyme adsorption and inactivation behaviour of these substrates was compared with that of polystyrene beads (dialysed), which has been well studied in the literature. Results from this thesis indicated that hydrophobic interactions between the enzyme and the substrate surfaces had a major impact on the HRP adsorption behavior, while electrostatic interactions played a minor role. However, strong hydrophobic interactions could lead to enzyme inactivation. Research findings from this study suggested that cellulosic pulp fibers could be tailor-made into excellent enzyme immobilization supports by using existing fiber surface modification techniques.