La friction entre les surfaces mobiles de l’organisme peut être un problème difficile à résoudre, notamment dans les pathologies dégénératives comme l’arthrose ou la sécheresse oculaire. Malgré le développement de nombreux produits pharmaceutiques, les matériaux actuellement utilisés pour protéger les tissus blessés et les dispositifs biomédicaux contre l'usure par frottement sont encore limités dans leurs performances. Il existe un besoin urgent de matériaux injectables capables de protéger ces tissus et dispositifs afin de prolonger leur durée de vie et de traiter efficacement des maladies dégénératives. Parmi les innovations de la dernière décennie, les polymères à structure dite « en brosse » (BBs) se sont révélés prometteurs pour amoindrir les problèmes de friction et d'usure. Inspirés de l’architecture spécifique du protéoglycane 4, l'un des principaux composants lubrifiants du cartilage, les macromolécules BBs sont constituées d’un squelette linéaire et de chaînes latérales formant une brosse dense pouvant maintenir de l’eau sous une pression élevée. Les différentes structures des BBs, selon le squelette et leurs chaînes latérales, conduisent à plusieurs caractéristiques morphologiques et propriétés tribologiques intéressantes dans l’ingénierie tissulaire. Bien que leurs propriétés lubrifiantes aient été prouvées dans plusieurs études, les BBs n’ont à ce jour que peu d’applications. D’une part, la corrélation entre leur structure et leurs propriétés physicochimiques n’est pas encore clairement établie. D’autre part, il manque encore des études relatives à l’efficacité des BBs sur de vrais tissus. Pour pallier ce problème, notre projet vise à caractériser les propriétés physicochimiques et tribologiques des BBs sur différents types de surfaces en fonction de leur structure. La longueur du squelette, la densité de greffage et l’addition du groupe d’ancrage sont les 3 variables principales étudiées dans ce projet. La lubrification ainsi que d’autres propriétés importantes des BBs ont été évaluées sur les surfaces molles des cartilages, des yeux et des lentilles en contact. Les tests tribologiques ont été menés en utilisant un appareil à force de surface (SFA) via l’association du protocole classique et avancé qui l’adapte aux surfaces testées. A côté de la tribologie, l’affinité cinétique, la toxicité, les propriétés antisalissure et anti-inflammatoire des BBs sur les interfaces ont aussi été étudiées dans ce projet via les techniques de LigandTracer et de microscope fluorescent. / Friction between the body's moving surfaces can be a difficult problem to solve, particularly in degenerative pathologies such as osteoarthritis or dry eye. Despite the development of numerous pharmaceutical products, the materials currently used to protect injured tissues and biomedical devices against frictional wear are still limited in their performance. There is an urgent need for injectable materials capable of protecting these tissues and devices in order to extend their life and effectively treat degenerative diseases. Among the innovations of the last decade, polymers with a so-called "brush structure" (BBs) have shown promise in reducing friction and wear problems. Inspired by the specific architecture of proteoglycan 4, one of the main lubricating components of cartilage, BBs macromolecules consist of a linear backbone and side chains forming a dense brush capable of holding water under high pressure. The different structures of BBs, depending on the backbone and their side chains, lead to several morphological features and tribological properties of interest in tissue engineering. Although their lubricating properties have been proven in several studies, BBs have few applications to date. On the one hand, the correlation between their structure and physicochemical properties has not yet been clearly established. On the other hand, studies on the effectiveness of BBs on real tissues are still lacking. To overcome this problem, our project aims to characterize the physicochemical and tribological properties of BBs on different types of surfaces, depending on their structure. Backbone length, graft density and anchoring group are the 3 main variables studied in this project. Lubrication and other important properties of BBs were evaluated on the soft surfaces of cartilages, eyes and contact lenses. Tribological testing was carried out using a Surface Force Apparatus (SFA) via a combination of the classic and advanced protocol, adapting it to the surfaces tested. Alongside tribology, the kinetic affinity, toxicity, anti-fouling and anti-inflammatory properties of BBs on interfaces were also studied in this project via LigandTracer and fluorescent microscopy techniques.

Doctor of Philosophy / Department of Chemical Engineering / Larry E. Erickson / Over the past decade, nanomaterials have been the subject of enormous interest. Their defining characteristic is a very small size in the range of 1-100 nm. Due to their nanometer size, nanomaterials are known to have unique mechanical, thermal, biological, optical and chemical properties, together with the potential for wide-ranging industrial applications. Here, we synthesized nanocrystalline metal oxides through the sol-gel process and used these materials as desulfurization adsorbents and photocatalysts. Deep desulfurization of fuels has received more and more attention worldwide, not only because of health and environmental consideration but also due to the need for producing ultra-low-sulfur fuels, which can only be achieved under severe operating conditions at high cost using hydrodesulfurization (HDS). Consequently, development of new and affordable deep desulfurization processes to satisfy the decreasing limit of sulfur content in fuels is a big challenge. Sol-gel derived Cu/Al[subscript]2O[subscript]3 and Zn/Al[subscript]2O[subscript]3 adsorbents have been demonstrated to be effective in the removal of thiophene from a model solution. Results showed that Cu[superscript]+ was the active site and thermal treatment under vacuum was critical for Zn/Al[subscript]2O[subscript]3 since a defective, less crystalline spinel led to stronger interaction between zinc ions and thiophene molecules in the adsorption process. The kinetic study suggested that most of the adsorption occurred in the first 30 min, and adsorption equilibrium was attained after 1.5 h. Both adsorbents showed good regenerative property. TiO2 is considered the most promising photocatalyst due to its high efficiency, chemical stability, non-toxicity, and low cost for degradation and complete mineralization of organic pollutants. However, the use of TiO[subscript]2 is impaired because it requires ultraviolet (UV) activation ([Lambda]<387 nm). The shift of optical response of TiO[subscript]2 from the UV to the visible light region would have a profound positive effect on the efficient use of solar energy in photocatalytic reactions. We shifted the optical response of TiO[subscript]2 and improved the photocatalytic efficiency through size modification and transition metal ion and nonmetal atom doping. Experimental results showed that C and V co-doped TiO[subscript]2 catalysts had much higher activity than commercial P25 TiO[subscript]2 towards the degradation of acetaldehyde under visible light irradiation. For the first time, we reported that activities were comparable in the dark and under visible light irradiation for co-doped TiO[subscript]2 with 2.0 wt% V. C and N co-doped TiO[subscript]2 exhibited higher activity for the degradation of methylene blue than pure TiO[subscript]2 under visible light and UV irradiation. Possible mechanisms were discussed based on the experimental results.

Master of Science / Department of Civil Engineering / Hayder A. Rasheed / Throughout history natural fiber was used as one of the main building materials all over the world. Because the use of such materials has decreased in the last century, not much research has been conducted to investigate their performance as a reinforcing material in cement and concrete. In order to investigate one of the most common natural fibers, wheat fibers, as a reinforcing material, 156 mortar specimens and 99 concrete specimens were tested. The specimens were tested in either uniaxial compression or flexure. The uniaxial compression test included 2 in (50.8 mm) mortar cubes and 4x8 in (101.6 x 203.2 mm) concrete cylinders. As for the flexure test, they were either 40x40x160 mm cementitious matrix prisms or 6x6x21 in (152.4x152.4x533.4 mm) concrete prisms. Several wheat fibers percentages were studied and compared with polypropylene fiber as a benchmarking alternative. The average increase in the uniaxial compression strength for cementitious matrix cubes reinforced with 0.5% long wheat fiber exceeded that of their counterparts reinforced with polypropylene fiber by 15%. Whereas for concrete cylinders reinforced with 0.75% long wheat fiber, their strength exceeded that of their counterparts reinforced with polypropylene fiber by 5% and that of the control by 7%. The flexural strength of cementitious matrix prisms reinforced with 0.75% long wheat fiber exceeded that of their counterparts reinforced with polypropylene fiber by 27%. Meanwhile, concrete prisms reinforced with both long wheat fiber and polypropylene fiber showed deterioration in strength of up to 17%. Finally, ABAQUS models were developed for concrete cylinders and prisms to simulate the effect of inclusion of the wheat fibers.

Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the bysuss revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

The chemistry and corrosion mechanisms associated with reduced sulfur compounds such as calcium sulfide, present in ground granulated blast-furnace slag (GGBFS), have been studied in high-density concrete, mortar and simulated pore-water environments. The high-density concrete and mortar samples were produced to replicate the high-density GGBFS concrete, in the dry storage containers (DSCs), used for radiation shielding from used nuclear fuel. Electrochemical measurements on embedded steel electrodes in high-density GGBFS concrete and mortar samples, showed that sulfide is capable of consuming oxygen to create a stable, reducing environment, though not in all cases, and the high-frequency electrolyte resistance increases with hydration time. Ion chromatography on simulated pore-water environments determined that thiosulfate is quite kinetically stable as a sulfide oxidation product and magnetite is capable of oxidizing sulfide. Microscopy has also been used to provide visual evidence of GGBFS hydration and elemental quantification of the hydrating microstructure in different environments.

Since their accidental introduction into the Great Lakes in mid- to late-1980s, the freshwater zebra mussels, Dreissena polymorpha, have colonized most lakes and waterways across eastern North America. Their rapid spread is partly attributed to their ability to tenaciously attach to hard substrates via an adhesive apparatus called the byssus, resulting in serious environmental and economic impacts. A detailed ultrastructural study of the bysuss revealed a 10 nm adhesive layer at the attachment interface. Distributions of the main adhesive amino acid, 3,4-dihydroxyphenylalanine (DOPA), and its oxidizing (cross-linking) enzyme, catechol oxidase, were determined histochemically. It was found that, upon aging, DOPA levels remained high in the portion of the byssus closest to the interface, consistent with an adhesive role. In contrast, reduced levels of DOPA corresponded well with high levels of catechol oxidase in the load-bearing component of the byssus, presumably forming cross-links and increasing the cohesive strength.

The chemistry and corrosion mechanisms associated with reduced sulfur compounds such as calcium sulfide, present in ground granulated blast-furnace slag (GGBFS), have been studied in high-density concrete, mortar and simulated pore-water environments. The high-density concrete and mortar samples were produced to replicate the high-density GGBFS concrete, in the dry storage containers (DSCs), used for radiation shielding from used nuclear fuel. Electrochemical measurements on embedded steel electrodes in high-density GGBFS concrete and mortar samples, showed that sulfide is capable of consuming oxygen to create a stable, reducing environment, though not in all cases, and the high-frequency electrolyte resistance increases with hydration time. Ion chromatography on simulated pore-water environments determined that thiosulfate is quite kinetically stable as a sulfide oxidation product and magnetite is capable of oxidizing sulfide. Microscopy has also been used to provide visual evidence of GGBFS hydration and elemental quantification of the hydrating microstructure in different environments.

Double cantilever beam (DCB) specimens with distinct intermetallic microstructures and different geometries were fractured under different mode ratios of loading, ψ, to obtain critical strain energy release rate, Jc. The strain energy release rate at crack initiation, Jci, increased with phase angle, ψ, but remained unaffected by the joint geometry. However, the steady-state energy release rate, Jcs, increased with the solder layer thickness. Also, both the Jci and Jcs decreased with the thickness of the intermetallic compound layer. Next, mode I and mixed-mode fracture tests were performed on discrete (l=2 mm and l=5 mm) solder joints arranged in a linear array between two copper bars to evaluate the J = Jci (ψ) failure criteria using finite element analysis. Failure loads of both the discrete joints and the joints in commercial electronic assemblies were predicted reasonably well using the Jci from the continuous DCBs. In addition, the mode-I fracture of the discrete joints was simulated with a cohesive zone model which predicted reasonably well not only the fracture loads but also the overall load-displacement behavior of the specimen. Additionally, the Jci calculated from FEA were verified estimated from measured crack opening displacements in both the continuous and discrete joints. Finally, the pad-crater fracture mode of solder joints was characterized in terms of the Jci measured at various mode ratios, ψ. Specimens were prepared from lead-free chip scale package-PCB assemblies and fractured at low and high loading rates in various bending configurations to generate a range of mode ratios. The specimens tested at low loading rates all failed by pad cratering, while the ones tested at higher loading rates fractured in the brittle intermetallic layer of the solder. The Jci of pad cratering increased with the phase angle, ψ, but was independent of surface finish and reflow profile. The generality of the J =Jci(ψ) failure criterion to predict pad cratering fracture was then demonstrated by predicting the fracture loads of single lap-shear specimens made from the same assemblies.

Double cantilever beam (DCB) specimens with distinct intermetallic microstructures and different geometries were fractured under different mode ratios of loading, ψ, to obtain critical strain energy release rate, Jc. The strain energy release rate at crack initiation, Jci, increased with phase angle, ψ, but remained unaffected by the joint geometry. However, the steady-state energy release rate, Jcs, increased with the solder layer thickness. Also, both the Jci and Jcs decreased with the thickness of the intermetallic compound layer. Next, mode I and mixed-mode fracture tests were performed on discrete (l=2 mm and l=5 mm) solder joints arranged in a linear array between two copper bars to evaluate the J = Jci (ψ) failure criteria using finite element analysis. Failure loads of both the discrete joints and the joints in commercial electronic assemblies were predicted reasonably well using the Jci from the continuous DCBs. In addition, the mode-I fracture of the discrete joints was simulated with a cohesive zone model which predicted reasonably well not only the fracture loads but also the overall load-displacement behavior of the specimen. Additionally, the Jci calculated from FEA were verified estimated from measured crack opening displacements in both the continuous and discrete joints. Finally, the pad-crater fracture mode of solder joints was characterized in terms of the Jci measured at various mode ratios, ψ. Specimens were prepared from lead-free chip scale package-PCB assemblies and fractured at low and high loading rates in various bending configurations to generate a range of mode ratios. The specimens tested at low loading rates all failed by pad cratering, while the ones tested at higher loading rates fractured in the brittle intermetallic layer of the solder. The Jci of pad cratering increased with the phase angle, ψ, but was independent of surface finish and reflow profile. The generality of the J =Jci(ψ) failure criterion to predict pad cratering fracture was then demonstrated by predicting the fracture loads of single lap-shear specimens made from the same assemblies.

The primary objective was to predict the relative storage capacity of carbonate rocks relevant for carbon dioxide sequestration. To achieve this, a detailed pore scale characterization of model carbonate rocks, Indiana Limestone and Pink Dolomite, was conducted utilizing micro-computed tomography (microCT) data using pore network modeling and invasion percolation simulations. For the first time in literature, Pink Dolomite’s pore space characteristics were analyzed. A secondary objective was to compare thresholding techniques as applied to carbonates which exhibit dual porosity (porosity at multiple length scales). The analysis showed the sensitivity of existing methods to the thresholding technique, imaging method and material. Overall, the contributions of this work provide an assessment of two carbonates relevant for carbon capture and storage at the pore scale; and a preliminary assessment into thresholding dual porosity carbonates.