Department: Engineering : Materials Science ![[clear]](close-x.png "Remove this limiter")
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1.
AGASHE, NIKHIL R.
IN-SITU SMALL ANGLE X-RAY SCATTERING STUDIES OF CONTINUOUS NANO-PARTICLE SYNTHESIS IN PREMIXED AND DIFFUSION FLAMES.
Degree: PhD, Engineering : Materials Science, 2004, University of Cincinnati
► Flame technology is an extremely effective method to synthesize nano-particles of ceramic…
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▼ Flame technology is an extremely effective method to synthesize nano-particles of ceramic oxides. The single-step chemistry, the ability to control shape and size and to produce millions of tons of nano-powders per annum with relative ease have made it popular with industry. Although this process primarily focused on oxides of silicon and titanium, it has now been adopted for manufacture of several other oxides of bismuth, vanadium, aluminum, iron, germanium and zirconium. There has been extraordinary progress in the application of flame burner to synthesize newer oxides having a wide range of particle size, polydispersity, composition and aggregation. But the fundamentals behind the mechanisms for particle formation and growth are still not well understood. Due to the extremely fast reaction rates, high temperatures and low concentrations associated with this process, it is difficult to accurately observe the formation of nuclei and their growth to aggregated nano-particles. Entire particle growth from inception to aggregation takes place in a few milliseconds! Light scattering and thermophoretic sampling have been used extensively to study such flames. But light scattering suffers from the brightness of the flame and the limitation on the size-range it can probe. It can only detect aggregates, and information about primary particles needs to be obtained by thermophoretic sampling. However thermophoretic sampling is an intrusive technique and sample collection in the flame involves disturbance of flow of the gases and the particles in the flame. It is necessary to find a single non-intrusive technique that can yield complete information for the flame and detect the rapid growth. In-situ small angle x-ray scattering (iSAXS), which utilizes high energy x-rays from synchrotron sources fits such a role perfectly. iSAXS of particles in the flame provides full information from nano-scale to micron-scale and about the evolution of particles and their morphology. Experiments were carried out at third generation synchrotrons like Advanced Photon Source (USA) and European Synchrotron Radiation Facility (France). Several premixed and diffusion flames producing silica and titania were investigated for the product volume fraction, primary particle size, polydispersity of powders, number concentration, aggregate size, mass fractal dimension and degree of branching.
Advisors/Committee Members: Beaucage, Dr. Gregory.
Subjects: Engineering, Materials Science
Keywords: Insitu Small Angle X-ray Scattering; Nucleation; Flame Synthesis; Mass Fractal Aggregates; Nano-particle Growth
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2.
AGASHE, NIKHIL RAVINDRA.
IMPLICATIONS OF AGGREGATION AND MASS FRACTAL NATURE OF AGGREGATES ON THE PROPERTIES OF ORGANIC PIGMENTS AND POLYMER COMPOSITES.
Degree: MS, Engineering : Materials Science, 2001, University of Cincinnati
► Aggregation of organic pigments was studied by small and ultra-small angle x-ray…
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▼ Aggregation of organic pigments was studied by small and ultra-small angle x-ray scattering. The aggregation of organic pigments and the implications for optical properties has not been previously reported in the literature, although extensive literature of this type exists for inorganic pigments such as titania. The pigments were also inspected for primary particle-size by electron microscopy and aggregate size by light scattering. The pigments were examined as dry powders as well as after embedding in polymer matrices. All the pigments exhibited mass-fractal behavior when mixed into various polymers. Some pigments exhibited mass-fractal behavior even in powder form. The scattering patterns reflected differences in mass fractal dimension and particle size. The mass fractal dimension and the size of the aggregates in the polymer depend on the chemical nature of the pigment, the size and strength of the primary particle, the surface characteristics of the pigment and the interaction between the pigment and the polymer. The size and mass fractal dimension of the aggregate shows a clear dependence on the type of polymer used. A relation between the aggregate size and optimal optical properties is proposed here. Aggregates having size between 1 to 2 microns show best optical properties. It is proposed that the pigment aggregate growth needs to be controlled during processing to have good optical performance of the pigment. The processes of aggregation were examined for these pigments. Most of the pigments formed aggregates by a reaction limited aggregation process, except two pigments, which exhibited diffusion limited aggregation.
Advisors/Committee Members: Beaucage, Dr. Gregory.
Keywords: ORGANIC PIGMENTS; AGGREGATION; MASS FRACTAL AGGREGATES; SAXS
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3.
AHN, HYEON WOO.
SYNTHESIS, CHARACTAERIZATION AND COMPUTER SIMULATIONS OF STEREOREGULAR POLY-(METHYLPHENYLSILOXANE).
Degree: PhD, Engineering : Materials Science, 2002, University of Cincinnati
► The synthesis of stereoregular siloxane polymers may revolutionize the siloxane industry. In…
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▼ The synthesis of stereoregular siloxane polymers may revolutionize the siloxane industry. In the past, the preparation of stereoregular siloxane polymers was hindered by the unavailability of appropriate organosilicon monomers, the lack of efficient synthetic methods suitable for the stereoselective polymerization, and difficulties in the evaluation of the stereoregulartity of the resulting polymers. Thus, in this dissertation, the synthesis of stereoregular poly(methylphenylsiloxane) (PMPS) was pursued using cis-trimethyltriphenylcyclotrisiloxane (cis-P3) as the monomer. In addition, a new concept of stereoregular polymer, which was named ‘Ahn-Clarson’s Stereoregular Polymer’ was proposed and its significance was studied by computer simulations. The result of the simulations indicate the possibility that we would obtain PMPS with extended linear behavior in its conformation by placing the same number of pendant groups on both sides of the chain in an alternating fashion. For the synthesis of stereoregular PMPS, detailed information on the preparation and separation of the monomer was determined. Using pure cis-P3, when cyclohexane was used as solvent in an anionic ring-opening polymerization, an equilibrium reaction was observed. In this reaction, it was found that 2,4’,6,8’-tetramethyl-2’,4,6’,8-tetraphenylcylcotetrasiloxane (trans-P4[IV]) was hardly formed and its mechanism was proven by 1H-NMR. Also, a totally non-equilibrium anionic ring-opening polymerization was accomplished when tetrahydrofuran was used as solvent and the condition to achieve the non-equilibrium reaction was determined. Using a non-equilibrium anionic ring-opening polymerization, stereoregular PMPS with 80% isotacticity was prepared and was proven by both 1H-NMR and DSC. Current contradictions of the assignment of the triad peaks of PMPS were explained and it was proven that the meso-meso triad peak was seen upfield. Finally, the rotational isomeric state theory was employed to calculate the characteristic ratio of different types of stereoregular PMPS and it is proposed here that the current structural parameters of PMPS must be revised for more accurate calculations.
Advisors/Committee Members: Clarson, Dr. Stephen J.
Keywords: silicones; steroregular; poly(methlphenylsiloxane); antonic ring-opening polymerization; rotational isomeric; cis-trimethyltriphenlcyclotrisiloxane
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4.
AKUNDY, GOURI.
DEPOSITION OF POLYANILINE-POLYPYRROLE COMPOSITE COATINGS ON ALUMINUM.
Degree: MS, Engineering : Materials Science, 2001, University of Cincinnati
► The electrodeposition of polyaniline, polypyrrole and their composite coatings on aluminum was…
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▼ The electrodeposition of polyaniline, polypyrrole and their composite coatings on aluminum was successfully performed by cyclic voltammetry using oxalic acid as the electrolyte. Electrodeposition parameters such as scan rate and the number of cycles (reaction time) were varied. At longer reaction times, the characteristic peak currents corresponding to the formation of the homopolymers were seen in their respective cyclic voltammograms. The infrared spectra of the coatings showed the presence of aluminum oxalate passive film at short cycles. At longer cycles, the infrared spectra of the composite coatings showed both the absorption bands of polyaniline and polypyrrole. The scanning electron micrographs revealed globular morphology for polyaniline, microspheroidal structure for polypyrrole and flaky morphology for the composite. The behavior of the cyclic voltammograms at longer cycles revealed a quasi-reversible charge transfer mechanism. A chemical reaction preceding irreversible charge transfer was observed at shorter cycles. The adhesion of the composite coatings to the aluminum substrate was determined by lap shear tests according to an ASTM standard procedure D-1002-94. For a high aniline concentration (90%) in the reaction mixture, higher adhesion (12.5 MPa) values were obtained in comparison with the control (7.74 MPa). With a high concentration of pyrrole (90%) in the reaction mixture, good adhesion results (12.09 MPa) were obtained at shorter reaction times (30 sec).
Advisors/Committee Members: Iroh, Dr. Jude.
Subjects: Engineering, Materials Science
Keywords: conduting polymers; polyaniline; polypyrrole; composite; electrochemical polymerization
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5.
ASHIRGADE, AKSHAY A.
ENVIRONMENTALLY-COMPLIANT NOVOLAC SUPERPRIMERS FOR CORROSION PROTECTION OF ALUMINUM ALLOYS.
Degree: MS, Engineering : Materials Science, 2006, University of Cincinnati
► The Environmental Protection Agency (EPA) in the US has imposed legislations on…
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▼ The Environmental Protection Agency (EPA) in the US has imposed legislations on the use of hexavalent chromium and solvents contributing to emission of volatile organic compounds in primer coatings. This has led researchers to pursue development of alternative environmentally-friendly coatings which would eliminate chromate conversion coatings (CCC). This thesis discusses the work done towards the development of a novel, chromate-free, low-VOC, water-based, organic coating system for corrosion protection of AA 2024-T3 aerospace alloy. These special coatings which can be applied directly to the metal are termed as ‘superprimers’ and consist of novolac epoxy binder, silanes, polyurethane and non-chromate inhibitors. Coating evaluation tests were employed to compare the performance of the superprimer coatings with controls. SEM, FTIR and NMR were carried out to understand the chemistry of the coatings. The requirement for a conversion coating was obviated and the coating system developed was on par with the chromate-based control coating in terms of performance.
Advisors/Committee Members: Van Ooij, Dr. William J.
Subjects: Engineering, Materials Science
Keywords: Organic Coatings; Superprimer; Corrosion; Novolac; AA 2024-T3; Silane
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6.
Atthipalli, Gowtam.
Light Scattering by Colloids Larger than Wavelength of Light.
Degree: MS, Engineering : Materials Science, 2007, University of Cincinnati
► The twin objectives of this thesis is to understand what happens when…
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▼ The twin objectives of this thesis is to understand what happens when light is scattered by colloids larger than the wavelength of light and study light scattering results on an absolute scale by means of calibration. The first objective was achieved studying scattering by silica and the second objective used light scattering results from spherical polystyrene beads and calibrate a static light scattering instrument. Inorganic silica is widely used a filler material in rubber to increase its mechanical properties. Precipitated silica particles, like the ones studied in this report have three major size scales – agglomerates, aggregates, primary particles. Light scattering technique has been used to study the breakup of agglomerates in silica. The study aims at providing insight into the breakup of agglomerates by a combination of varying three parameters - concentration, obscuration and sonication power. The breakup of agglomerates is helpful in the dispersion of silica in a rubber matrix without actually formulating rubber. Polystyrene (PS) beads were used for the calibration study. Using Mie theory the contrast (difference in the scattering length densities) was identified and calculated.
Advisors/Committee Members: Schaefer, Dr. Dale.
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7.
Aykanat, Aydin.
Synthesis, Characterization and Cure Kinetics of Polyaniline Modified Clay / Epoxy Nanocomposites.
Degree: PhD, Engineering : Materials Science, 2008, University of Cincinnati
► This research work focuses on the synthesis characterization and processing of conducting…
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▼ This research work focuses on the synthesis characterization and processing of conducting polymer coated both carbon fiber and montmorillonite clay based nano-particles to improve the mechanical, thermal, and adhesive properties of epoxy based micro and nano composites. The entire research work mainly consists of two parts. In the first part, homogeneous and uniform coatings of polyaniline were successfully deposited onto carbon fibers by aqueous electrodeposition technique using p-toluene sulfonic acid as the electrolyte. Electrochemical deposition of aniline was carried out by cyclic voltammetry in the potential range of -0.2 V to 1.0 V vs. SCE. The electrochemical deposition parameters such as the number of cycles, scan rate (SR), initial monomer ([M]) and electrolyte concentration ([E]) were systematically varied. The amount of composite coatings on carbon fibers was dependant on the electrochemical deposition parameters. From the weight gain analysis, rate of the reactions (Rp) were calculated. As the aniline concentration was increased up to 0.35 M and electrolyte concentration up to 0.5 M, the deposition rate also increased, whereas an increase in scan rate decreased the deposition rate. The kinetic analysis showed that the rate equation for the p-toluene sulfonic acid system is Rp ∝ SR-1.25 [M]0.73 [E]0.95. IR spectra also show an increase in the deposition of polyaniline coatings on carbon fibers with a decrease in the scan rate and an increase in both monomer and electrolyte concentration. The ratio of two oxidation states of polyaniline namely emeraldine and pernigraniline obtained during electrodeposition can be varied by changing the electrochemical deposition parameters. SEM results show that carbon fiber surface was uniformly coated with polyaniline resulting a dense, rough and reactive surface that increases the compatibility and wettability of carbon fibers. The effect of PANi coated carbon fibers on the curing behavior of diglycidyl ether of bisphenol-A (DGEBA) epoxy prepolymer crosslinked with tri ethylene tetra amine (TETA) was analyzed by DSC. The tensile, flexural and impact tests of carbon fiber epoxy micro composites showed that PANi coated carbon fiber epoxy systems have higher modulus, toughness and mechanical strengths compared to unmodified carbon fiber epoxy composites. In the second part of the research work, conducting polyaniline (PANi) montmorillonite (MMT) clay nanocomposites were synthesized by using in-situ polymerization. The X-Ray diffraction patterns showed that polyaniline was intercalated between clay galleries in the order of nanoscale. From the SEM micrographs, it was revealed that, in-situ polymerization of aniline took place both in and out of the clay galleries. Polyaniline surface modified clay nanoparticles were then dispersed in diglycidyl ether of bisphenol-A (DGEBA) epoxy prepolymer using high shear mixing and ultrasonication. The viscosity measurements of modified and unmodified clay dispersed in epoxy prepolymer systems showed that PANi modified clay has lower viscosity than the pristine clay that provides easiness during processing. Infrared spectroscopy data proves that reactive secondary and tertiary amine groups on the fully dispersed polyaniline modified clay platelets react with epoxy resin resulting a strong chemical and physical interaction between nanoparticles and polymeric matrix. The effect of PANi surface modified nano particles on the curing reaction and kinetics of epoxy with tri-ethylene tetra amine (TETA) was analyzed by using DSC and explained by modified Avrami equation. The X-Ray diffraction pattern of fully cured 5% (w/w) PANi-MMT clay epoxy nanocomposites showed exfoliation behavior. Thermal analysis showed that for 5% (w/w) PANi-MMT filled epoxy nanocomposites has higher thermal stability than both fully cured pristine epoxy and 5% (w/w) clay epoxy nanocomposite. With the addition and exfoliation of 5% (w/w) PANi modified clay an increase of 8 °C in glass transition temperature was observed with respect to pristine epoxy. Thermal analysis also showed that polyaniline on the surface of nanoparticles improves crosslinking reaction by reducing the curing time and helping the reaction to occur at lower temperatures. Mechanical testing results for 5% (w/w) polyaniline clay epoxy nanocomposites showed 30 to 35% increase in the tensile strength compared to the pristine epoxy. This enhancement of the tensile strength is ascribed to the resistance exerted by the clay itself as well as the aspect ratio of the clay layers and the partial exfoliation and/or fully intercalation of clay galleries. The degree of intercalation of the clay platelets in the epoxy matrix is proportional to an increase in the flexural strengths. In-situ polymerization of aniline within the clay galleries causes a more homogeneous exfoliation of the clay in the epoxy matrix.
Advisors/Committee Members: Iroh, Jude.
Subjects: Engineering; Materials science; Polymers
Keywords: polyaniline; montmorillonite; clay; epoxy; nanocomposite; curing; kinetics; conducting polymer
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8.
BAFNA, AYUSH ASHOK.
OPTICAL PROPERTIES AND ORIENTATION IN POLYETHYLENE BLOWN FILMS.
Degree: MS, Engineering : Materials Science, 2001, University of Cincinnati
► In this thesis we report structural factors affecting the optical properties of…
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▼ In this thesis we report structural factors affecting the optical properties of blown polyethylene films. Two types of blown polyethylene films of similar degree of crystallinity were made from 1) single-site catalyst HDPE (STAR alpha) and 2) Ziegler-Natta catalyst HDPE (ZN) resins. The STAR alpha film exhibited high clarity and gloss, while the ZN film was turbid. Small-angle x-ray scattering (SAXS), small-angle light scattering (SALS) and optical microscopy gave quantitative and qualitative information regarding structure and orientation in the films. A new approach is described for determining the 3-dimensional lamellar normal orientation from SAXS. Both the clear STAR alpha and turbid ZN films had similar lamellar crystalline structures, long periods and degree of crystallinity but displayed different degrees of nano-scale orientation. It is demonstrated that optical haze is related to surface features that seem to be linked to the bulk morphology. The relationship between haze and structural orientation is described. The lamellar orientation was linked to rod like structures seen in optical microscopy and SALS through stacked lamellae or cylindrite morphology on the nano-scale. The micron-scale rod-like structures seem directly related to surface roughness by comparison of index matched immersion and surface micrographs. The higher haze and lower gloss of the ZN film was shown to be caused by extensive surface roughness, not observed in the STAR alpha film.
Advisors/Committee Members: Beaucage, Dr. Gregory.
Keywords: POLYETHYLENE; ORIENTATION; SAXS; OPTICAL PROPERTIES; SALS
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9.
BAFNA, AYUSH ASHOK.
POLYETHYLENE-CLAY NANOCOMPOSITES: PROCESSING-STRUCTURE-PROPERTY RELATIONSHIP.
Degree: PhD, Engineering : Materials Science, 2004, University of Cincinnati
► A brief overview of synthesis and characterization techniques of nanocomposites and the…
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▼ A brief overview of synthesis and characterization techniques of nanocomposites and the importance for considering clay layer orientation along with its dispersion in the nanocomposites is discussed. Although few earlier reports tried to qualitatively relate the clay orientation to the property enhancement, no quantitative study was present. The possible reason for this was the absence of a technique to quantitatively determine the 3D orientation of structures in a Nanocomposite. In the present study a technique to determine the 3D orientation was developed. The effect of compatibilizer concentration on the orientation and dispersion of structures in polyethylene nanocomposite films was studied. It was shown that increase in concentration decreased the orientation of clay layer normals along the film thickness. The possible reason that could explain this behavior is discussed. It was also of interest to study the effect of processing conditions on the orientation of structures in nanocomposite films and relate the change in orientation to film properties. Polyethylene nanocomposite films with varying thickness were extrusion cast using different draw down ratios. Decreasing thickness was observed to increase the clay basal plane orientation along the film machine direction which in turn was observed to increase the reinforcing ability of the clay layers in both pseudo-static and dynamic tensile property measurements. A model to theoretically predict the tensile modulus based on the degree of clay orientation is developed and its data compared to that obtained experimentally. Bottles from 2 different nanocomposites varying in clay content were blow molded using varying processing conditions. It was observed that varying processing conditions did not have a significant effect on the orientation of the clay layers in the bottles. The effect of clay content on barrier, column crush strength and drop impact strength of nanocomposite bottles was also studied.
Advisors/Committee Members: Beaucage, Dr. Gregory.
Subjects: Engineering, Materials Science
Keywords: Polyethylene, nanocomposites, films, orientation, properties
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10.
Bafna, Shakhar M.
Environmentally-Friendly Polyurethane-Silane Superprimer for Corrosion Protection of AA2024-T3.
Degree: MS, Engineering : Materials Science, 2007, University of Cincinnati
► Chromates used as pretreatments for metals and as anti-corrosive pigments in primers…
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▼ Chromates used as pretreatments for metals and as anti-corrosive pigments in primers have been found to be a strong carcinogen and hence there is considerable pressure from environmentalists and government agencies for its replacement. Dr. Van Ooij and his research group have developed an array of environmentally friendly hydrophobic silane based pretreatments for corrosion protection of metals. However these coatings are extremely thin, of the order of a few hundred nanometers and hence unable to provide long term corrosion protection like a paint film which has thickness in microns. To eliminate this problem, the idea of Superprimer was conceptualized. “Superprimers” are self-priming coatings containing a mixture of polymer resin and silane as the binder and chromate-free, environmentally friendly corrosion inhibitor make a complete primer formulation. Thus, by adding the right silane to a coating resin, the chromate pretreatment step would be eliminated and the chromate pigment would be replaced by an environmentally friendly anti-corrosive pigment. This research deals with the evaluation of polyurethane-silane superprimer coatings as potential replacement of chromate pretreatment and chromat-containing high VOC primers for corrosion protection of AA 2024-T3 aluminum alloy. The silane chosen was BTSE because of its dipodal structure, hydrophobicity and ability to hydrolyze in water. EIS revealed that the hydrophobicity of the coatings increased considerably due to addition of 4 % BTSE silane improving its impedance and water barrier properties. RAIR and NMR spectroscopy showed hydrolysis and self condensation to siloxanes of the silane molecules. The formation of the siloxane network enhances the tensile strength, Tg and thermal degradation behavior of the coating, as detected by tensile testing, DSC and TGA, respectively. ToF_SIMS and EDXS studies of the interface indicated the presence of siloxane layer at the interface between the metal and coating. It indicated that the silane added to the polyurethane formulation segregated at the interface to form a dense siloxane network below the polyurethane coating. Four different, environmentally friendly corrosion inhibitive pigments were studied by incorporating them separately in the optimized polyurethane-silane formulation and applied them directly over AA2024-T3 without the use of a chromate conversion coating. Corrosion tests such as EIS and salt spray test (ASTM-B117) indicated that calcium zinc molybdate can be a promising replacement to chromates for the system under study.
Advisors/Committee Members: Van Ooij, Dr. William.
Subjects: Engineering, Materials Science
Keywords: superprimer; silane; chromates; polyurethane
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11.
BENGU, BASAK.
THE MOLECULAR STRUCTURE OF INTERFACES FORMED BETWEEN PLASMA POLYMERIZED SILICA-LIKE FILMS AND EPOXY ADHESIVES.
Degree: PhD, Engineering : Materials Science, 2007, University of Cincinnati
► The molecular structure of the interphase formed by curing a model adhesive…
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▼ The molecular structure of the interphase formed by curing a model adhesive system consisting of the diglycidyl ether of bisphenol-A (DGEBA) and dicyandiamide (DDA) against inorganic substrates, including mechanically polished aluminum, electrogalvanized steel (EGS) and plasma polymerized silica-like primer films, was determined using reflection–absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). RAIR analysis suggested that DGEBA/DDA mixtures created an interphase with a different molecular structure from the bulk of the adhesive when cured in contact with aluminum. The formation of this unique interphase was mainly due to interactions between DDA and the Al surface. XPS analysis indicated that aluminum ions exposed by heating the substrate surface were necessary for this interaction. DDA was found to adsorb onto the aluminum surface via the lone pair of electrons on the nitrogen atoms of the nitrile groups. A slight decrease in the nitrile stretching frequency indicated an additional back-bonding interaction between aluminum ions and the nitrile groups. Slight back donation of electrons from the metal to DDA resulted in a reduction product that led to the formation of the carbodiimide form of DDA. This specific reaction caused a decrease in the concentration of nitrile groups in the interphase and changed the network structure of the epoxy adhesive in the regions close to the oxide surface. The interaction of DDA with EGS surfaces followed a similar trend. However, the effects were much more pronounced with EGS and the path of the curing reaction and the network structure near the metal surface were strongly affected by EGS/DDA interactions. Two types of plasma polymerized silica-like films were prepared from hexamethyldisiloxane (HMDSO) monomer and oxygen by varying the gas compositions. One of the films was high and the other was low in hydroxyl content. XPS results showed that adjacent to the silica-like primer films, the adhesive had a composition enriched in DDA, indicating that curing agent was preferentially adsorbed onto the silica-like films. The preferential adsorption of the curing agent was lower in the case of low-hydroxyl silica like films, probably due to fewer active sites present on the low-hydroxyl silica like films.
Advisors/Committee Members: Boerio, F Dr. James.
Subjects: Engineering, Materials Science
Keywords: Dicyandiamide; Diglycidyl ether of bisphenol-A; Plasma polymerized silica-like films; Interfaces; Aluminum; XPS; RAIR
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12.
BERTELSEN, CRAIG MICHAEL.
RUBBER-TO-METAL BONDING: AN INVESTIGATION OF CHEMICAL REACTIONS AND ADHESION AT THE INTERFACE.
Degree: PhD, Engineering : Materials Science, 2001, University of Cincinnati
► Adhesion of rubber to steel plays an important role in many areas…
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▼ Adhesion of rubber to steel plays an important role in many areas of technology. However, adhesion of natural rubber (NR) to most metals is poor due to the polarity of the rubber surface. In order to obtain adhesion, the substrates are often plated with brass, which is one of the few metals that NR will adhere to. The goal of this research was to elucidate the chemistry between rubber and brass at the interface and to develop primers that could replace the brass plating. Rubber fracture and model rubber experiments were used to determine the mechanisms responsible for adhesion between rubber and brass. Plasma polymerization was used to develop acetylene primers to replace brass plating. In the rubber fracture experiments, failure surfaces from rubber/brass lap joints and single wire adhesion tests were analyzed using X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR). It was concluded that a rubber boundary layer existed, which consisted of high levels of oxidation and silicon that were related to adhesion failure. The composition of this layer depended on cure cycle. Model rubber experiments were used to determine the effects of two vulcanization accelerators, N,N-dicyclohexyl-2-benzothiazole sulfenamide and N-tert-butyl-2-benzothiazole sulfenamide, on the reactions between rubber and brass. Squalene, a low molecular weight hydrocarbon was used in place of NR. The chemical reactions between rubber and brass were characterized by IR, Raman, and XPS analysis. Analysis of the brass substrates after reaction with the model rubber systems showed that stearates, copper oxide, and sulfides formed initially on the surface. This was followed by squalene deposition and polyene formation (crosslinking). The rates at which these reactions occurred depended on the accelerator. Plasma-polymerized acetylene primers were developed using a microwave reactor. It was determined that low levels of fragmentation of acetylene molecules led to good adhesion in the rubber/plasma film/steel system. Fragmentation was controlled by the processing parameters, such as pressure, power and flow ratio used in the deposition process. Rubber/steel lap joints prepared from steel adherends coated with plasma-polymerized acetylene films outperformed joints prepared from brass-plated steel adherends in tests of initial adhesion and durability of adhesion.
Advisors/Committee Members: Boerio, Dr. F. James.
Subjects: Engineering, Materials Science
Keywords: model rubber systems; plasma-polymerized acetylene; rubber-to-brass adhesion; failure analysis; IR, Raman, and XPS analysis
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13.
BHARGAVA, SUMEET.
TEMPERATURE AND GAS SENSING CHARACTERISTICS OF GRAPHITE/POLYMER (PEO) BASED COMPOSITE STRUCTURES.
Degree: MS, Engineering : Materials Science, 2006, University of Cincinnati
► Conductive polymer composites have long been used in sensing applications. Since the…
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▼ Conductive polymer composites have long been used in sensing applications. Since the demand for such sensors is growing, further research is needed to keep pace and come up with new and improved materials. These materials have percolation structures with sufficient conductor phase dispersed in the polymer insulator matrix. The resistance in these materials can vary with temperature and gas ambience, so as to serve as sensitive sensors, with typically a sharp transition at a particular temperature. This study focused on the use of Poly Ethylene Oxide and graphite flakes. For such plate-like morphologies the conducting paths are formed at low percolation concentrations. The components were blended and hot pressed to pellets. Thermistor and gas sensing data showed sharp change. An inert ceramic additive was used to escalate the thermal stability. Microstructures and other structural features of the samples were observed using Optical microscopy and SEM to establish the structure-property correlation
Advisors/Committee Members: Buchanan, Dr. Relva C.
Subjects: Engineering, Materials Science
Keywords: CPC, conductive polymer composites, polymer composites, conductive composites, PEO, temperature sensors, gas sensors, polymer ceramic composite
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14.
Biao, Qi.
Sanding, Grit Blasting and Plasma Etching: Effect on Surface Composition and Surface Energy of Graphite/Epoxy Composites.
Degree: MS, Engineering : Materials Science, 2009, University of Cincinnati
► Peel ply treatment, sanding, grit-blasting, and plasma etching were used to prepare…
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▼ Peel ply treatment, sanding, grit-blasting, and plasma etching were used to prepare the surface of graphite/epoxy composites in order to improve surface adhesion performance. We measured the contact angles on the treated surfaces and subsequent wetting anisotropy was found on the sanded and grit blasted surfaces. Linear Kaelble method was employed to determine the surface energy. It was found that polar component of surface energy of sanded and girt blasted composites was between 0 mJ/m2 to 1.4 mJ/m2 while dispersive component of surface energy was between 41.0 mJ/m2 to 56.6 mJ/m2. The surface energy of composites after plasma etching with gap being 1.90 cm was 67.6 mJ/m2 with polar component of surface energy being 36.7 mJ/m2 and dispersive component of surface energy being 30.9 mJ/m2 while the surface energy of composites after plasma etching with gap being 2.54 cm was 41.4 mJ/m2 with polar component of surface energy being 3.0 mJ/m2 and dispersive component of surface energy being 38.4 mJ/m2. The surface energy results indicated the increase of the surface energy of sanded and grit-blasted composites was mainly due to the increase of the dispersive component of the surface energy while the increase of the surface energy after plasma etching treatment was attributed to the increase of the polar component of the surface energy. Moreover, the effect of plasma etching on the surface energy of composites was greatly influenced by plasma etching gap distance.XPS results indicated that sanding and grit blasting did not cause significant surface chemical composition changes compared with surface chemical composition of peel ply treated surfaces. After plasma etching with gap being 2.54 cm, there was a slight increase of oxygen concentration and decrease of carbon concentration while plasma etching with gap being 1.90 cm greatly changed the surface composition by increasing oxygen concentration and decreasing carbon concentration. Therefore, low content of polar functional groups from oxygen and nitrogen on the sanded and grit blasted surface resulted in the low polar component of surface energy. The big increase of polar groups such as C-O and C=O and a decrease in non-polar groups such as C-H and C-C made the composite surface after air plasma etching more polar, and resulted in the big increase of polar component of surface energy. SEM micrographs showed that sanding and grit blasting greatly changed the composites surface morphology and roughness while plasma etching did not cause significant surface morphology and roughness change compared with surfaces after peel ply treatments. Sanded surfaces were covered with oriented sanding scratches with sharp edges, random distributed debris and exposed and broken fibers while the main surface features of grit-blasted surfaces were micro-cracks and wear debris with different sizes distributed on them. The unique geometric morphology of sanded and grit-blasted surfaces controlled the liquid spreading on the surface and hence determined the contact angles and caused wetting anisotropy. Moreover, it could affect the surface energy by determining contact angles of probe liquids from which the surface energy was calculated. It was evident that the plasma etching treatment offered a more satisfactory method of improving surface adhesion performance for graphite/epoxy composites without causing surface damages and graphite fiber exposures and breakages.
Advisors/Committee Members: Boerio, F.James.
Subjects: Engineering
Keywords: Sanding; Surface Energy; Grit Blasting; XPS spectrum obtained; XPS; Peel ply; contact angles
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15.
BREESE, DAVID RYAN.
MODELING THE EFFECTS OF SOLID STATE ORIENTATION ON BLOWN HIGH MOLECULAR WEIGHT HIGH DENSITY POLYETHYLENE FILMS: A COMPOSITE THEORY APPROACH.
Degree: MS, Engineering : Materials Science, 2005, University of Cincinnati
► Polyethylene films are a major component in today’s flexible packaging and are…
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▼ Polyethylene films are a major component in today’s flexible packaging and are made with the most widely used polymer in the world. The selection of polyethylene films is the direct result of their balance of cost, processing, and physical properties. To take full advantage of this balance, the effects of the operating parameters of the film fabrication process must be understood in an effort to optimize the relationship between processing and physical properties. Of particular interest to the design of most packages is controlling the degree of molecular orientation in a film. This characteristic is generally determined by selecting the proper polymer, film fabrication process (e.g. cast vs. blown), and the ideal operating conditions (cast quench rate, blown high stalk, blown in-the-pocket, etc.) to produce a film with the desired degree of orientation. For the case where extremely high degrees of uniaxial orientation are required, the fabricated film is typically oriented in a “solid state” drawing process, where the quenched film is stretched in a given direction at temperatures below that of the melting point of the polymer. During this process, the stacked lamellae that form during the film fabrication process are transformed into rigid, long fiber-like structures. The presence of these rigid structures produce films with significantly enhanced moduli, break strengths, and optical properties. The goal of this program is to characterize the films with the intent of modeling the transformation of lamellae into fibers and predicting the previously mentioned physical properties. By doing so, a connection can be formed between the polymer’s characteristics and the final film properties, resulting in the fabrication of films that are unique to the industry.
Advisors/Committee Members: Beaucage, Dr. Gregory.
Keywords: Orientation; Polyethylene; MDO; Uniaxial stretch; High Molecular Weight; Bimodal Molecular Weight Distribution; Semi-crystalline
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16.
Breese, David Ryan.
Transitional Fiber/Non-Fibrous Gel Process-Structure-Property Model for Uniaxially Oriented Polymer Films.
Degree: PhD, Engineering : Materials Science, 2009, University of Cincinnati
► Controlling the extent of nano-lamellar crystalline orientation is of great interest in…
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▼ Controlling the extent of nano-lamellar crystalline orientation is of great interest in polymer processes because an inexpensive plastic film can be converted into a higher valued film of dramatically improved properties. Where high degrees of uniaxial orientation are required, the polymer is typically oriented in a solid state drawing post-processing operation, where the polymer is stretched in a single direction at temperatures just below the melting point. One commercial example, currently drawing wide interest in the polymer processing field, is known as machine direction orientation (MDO). During this process, pre-existing nano-crystallites are transformed into rigid, anisotropic structures. The presence of these rigid structures significantly enhances the moduli and break strength of the polymer film. A direct connection can be formed between the polymer's analytic characteristics, MDO processing conditions and the final engineering properties of the film. Within this dissertation are: Structure-property model applicable to a wide variety of polymers that predicts critical properties of the oriented film. Process model that estimates the film temperature throughout the orientation process, a necessity for relating the effects of processing conditions to the properties of the film. Experimental examples of the use of the structure-property model, which provides a detailed description of the structural changes that are occurring during orientation. This dissertation provides several comprehensive tools for the understanding and the modeling the process-structure-property relationship of oriented polymer films. A universal structure-property model has been developed that predicts the critical properties of a wide range of oriented polymer films. A heat transfer model has also been developed that estimates the film temperature throughout the orientation process. This model can be used in conjunction with the fiber/non-fibrous gel model to understand the effects of orientation conditions and equipment design on the film properties, as well as for the optimization of processing conditions and equipment design. Three independent experiments (LDPE, MDPE and ULDPE) were conducted that utilized the fiber/non-fibrous gel model, along with SAXS, XRD, DSC and mechanical testing, which provided a global understanding of the structure-property relationships that are occurring during orientation. With this knowledge, the structure can be controlled to produce films with specific physical properties.
Advisors/Committee Members: Beaucage, Gregory.
Subjects: Materials science; Polymers
Keywords: MDO; uniaxial; machine direction orientation; polymer; film; orientation; fiber; non-fibrous gel; LDPE; ULDPE; MDPE; plastic
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17.
Cain, Robert J.
Aqueous Processing of Corrosion Inhibiting Hybrid Nanocomposite Bulk Coating.
Degree: MS, Engineering : Materials Science, 2006, University of Cincinnati
► Environmentally friendly sol-gel coatings were developed on the automotive alloy AA6111. The…
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▼ Environmentally friendly sol-gel coatings were developed on the automotive alloy AA6111. The one-step coating process neither involves adding heavy metal chromium compounds nor organic solvents. Nano-structured silane coatings were developed and were systematically, optimized for corrosion resistance, as a function of reactant concentration and days of precursor reaction time. It was found that the precursor solution composed of Glycidoxypropyltrimethoxysilane (GPTMS) and Tetramethoxysilane (TMOS) (with a 3/1 respective ratio) needed at least 3 days of reacting time for proper hydrolysis and condensation. The results also indicate that at least a 7:1 ratio of curing agent Aminopropyl triethoxysilane (APTEOS) to GPTMS was optimal. The structure and composition of the hybrid coatings were determined using Fourier Transform Infrared Spectroscopy (FTIR). Coating adhesion was evaluated with dynamic contact angle analysis (DCA) and scratch testing. Corrosion performance was determined using DC Polarization (DCPT) and time dependent Electrochemical Impedance Spectroscopy (EIS). However, within two weeks, exposure to corrosive solution demonstrate coating instability in 3.5% NaCl salt solution. Hydrodynamic instability was improved, and internal stresses were reduced by replacing the monomeric curing agent with a commercial polymeric amine adduct. A wide range of reactant ratios were evaluated from 1:1 to 9:1, all of which were comparable with polarization tests. The 7 to 1 ratio lasted EIS testing for over three months. The curing kinetics were evaluated with respect to time, temperature, and extent of cure. Different curing temperatures were evaluated from room temperature to 130°C. It was found that the presence of water may slow the reaction rate below 100°C. Finally, fillers were introduced for their corrosion resistance and corrosion sensing abilities. Na+ Montmorrilonite clay composites were produced and exhibited water sensing abilities as confirmed by X-Ray Diffraction (XRD). XRD also confirmed the amorphous nature of the coating. Successful electrochromic behavior was observed in two of the coating formulations incorporating Prussian Blue with prolonged exposure to corrosive solutions.
Advisors/Committee Members: Iroh, Dr. Jude.
Subjects: Engineering, Materials Science
Keywords: Corrosion; Coating; Sol-gel; Aluminum; Nano; Silane
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18.
CHAKRAVARTY, SRINIVAS L.N.
DEVELOPMENT OF SCRATCH RESISTANT PECVD SILICA-LIKE FILMS.
Degree: MS, Engineering : Materials Science, 2000, University of Cincinnati
► Plasma-enhanced chemical vapor deposition (PECVD) was used to deposit silica-like films onto…
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▼ Plasma-enhanced chemical vapor deposition (PECVD) was used to deposit silica-like films onto various substrates to improve their scratch resistance. These films were deposited using a dual-frequency (microwave/low frequency) plasma reactor, which allowed the concentration of the active species in the plasma and the energy of bombardment of the species on the substrate to be controlled separately. External plasma parameters, including microwave (MW) power, low frequency (LF) power, and deposition time were varied to observe their effects on the thickness and hydroxyl content of the silica-like films. These parameters were optimized on ferroplate substrates to obtain thick silica-like films with low hydroxyl content to enhance their scratch resistance. However, it was found that when these silica-like films were deposited for deposition times longer than 2500 seconds, some undesirable powder particles were formed. Incorporation of powder particles into the film was detrimental to the scratch resistance properties. This problem was overcome by depositing films at low pressures (10 Pa). In order to optimize the external plasma parameters for enhancement of scratch resistance on ferroplate substrates at these low pressures, Taguchi's design of experiments was used. It was shown that silica-like films at a thickness of 4 (m or more could be deposited at the rate of 300 Å/min using these optimized parameters. These films exhibited excellent scratch resistance on ferroplate substrates. These films were also found to enhance the scratch resistance of polycarbonate substrates. Optical microscopy of the silica-like films directly deposited on FKM substrates revealed the presence of cracks in the films due to the compressive stresses in the film. Crack-free films were obtained on FKM substrates by depositing 2-layered films comprising a siloxane film as the first layer and silica-like film on top of the siloxane film. It was shown that these 2-layered films exhibited significantly better scratch resistance on FKM substrates than the directly deposited silica-like films. Tape peel tests were used to qualitatively evaluate the adhesion of the films to the FKM substrates. It was shown that the adhesion of the directly deposited silica-like films and multi-layered films to the FKM substrates was very good.
Advisors/Committee Members: Boerio, F. James.
Subjects: Engineering, Materials Science
Keywords: stresses in films; powder formation; 90 degree peel test; optical microscopy; Si-O-Si band assignments
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19.
Champhekar, Mangesh C.
Orientation in Polyethylene-Nanoclay Composites.
Degree: MS, Engineering : Materials Science, 2008, University of Cincinnati
► In this thesis we report the change in the orientation of the…
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▼ In this thesis we report the change in the orientation of the polymer lamellae and clay platelets from a PE-Nanocomposite film to that in the pressed composite sample, when a number of such films are hot pressed to form a pressed sample (strip), about 5 mm in thickness. Small-angle x-ray scattering (SAXS) was used to compare the quantitative and qualitative information regarding the structure and orientation of these structures in the film and the pressed strip. It was observed that the polymer lamellar normals in the composite film which were oriented in the MD get oriented in the ND in the pressed film sample. Diffraction studies carried out on both the samples show that the clay platelet normals for the film samples show a stronger orientation in the ND than for the pressed film sample. The tensile properties of the PE-Nanocomposite pressed sample (strip) and that of the Polyethylene (HDPE) film pressed sample (strip) was measured using an instron tensile machine and the values compared. The composite showed an increase in the modulus as compared to that observed in the virgin HDPE sample.
Advisors/Committee Members: Beaucage, Gregory.
Subjects: Materials science
Keywords: HDPE; Nanoclay; Orientation; SAXS; Diffraction; Tensile testing
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20.
CHANDRASEKARAN, SENTHILKUMAR.
ELECTRODEPOSITION OF BIS-SILANE FOR THE PRETREATMENT OF ALUMINUM ALLOYS.
Degree: MS, Engineering : Materials Science, 2006, University of Cincinnati
► The need for toxic chromate replacements in metal-finishing industries has prompted an…
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▼ The need for toxic chromate replacements in metal-finishing industries has prompted an intensive search for replacement technologies in recent years. Organofunctional silanes have emerged as an outstanding, environment friendly corrosion protectors of metal substrates for replacing the conventional chromate treatments. It has been recently demonstrated that electrodeposition of silane films on metal surfaces results in improvement of corrosion protection compared to the conventional coating methods like dip coating and spray coating. It has also been proved that uniformity and better control over the thickness of the coating can be achieved by electrodeposition. This thesis dissertation consists of two parts: (1) Identification of a novel silane, which produces comparatively hydrophobic, corrosion resistant film. (2) Development of a new volatile organic content (VOC)-free, water-based silane system. Various combinations of silane mixtures were tested at different voltages, pH’s, bath concentrations and exposure times on panels of aluminum alloys. The film formed was characterized mainly using electrochemical, surface and interfacial characterization techniques. Application of time of flight secondary ion mass spectroscopy (TOF-SIMS) to electrodeposited films has provided direct evidence for the presence of O2 Al(O-Si-O)and OAl(O-Si-O)2 groups at the silane-aluminum oxide interface. Also pulsed electrodeposition (alternating positive and negative voltage) of silanes were studied which show better performance, as anodization of the aluminum oxide layer is achieved and the silane film reacts with the metal oxide in a different way.
Advisors/Committee Members: van Ooij, Dr. William J.
Subjects: Engineering, Materials Science
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21.
CHASE, JENNIFER E.
SEMI-CONTINUOUS PLASMA POLYMERIZATION OF A FILM TO ENHANCE THE TEXTURE PROPERTIES OF AN ELASTOMER.
Degree: MS, Engineering : Materials Science, 2000, University of Cincinnati
► The texture of a styrene butadiene rubber (SBR) film was enhanced by…
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▼ The texture of a styrene butadiene rubber (SBR) film was enhanced by the deposition of a plasma-polymerized, siloxane-like coating. This improvement in texture was quantified as a reduction in the coefficient of friction of the SBR film, from approximately 1.2 for the uncoated material to 0.3 for the coated material. The adhesional forces in the elastomer that result in SBR film having a high coefficient of friction were masked upon the application of the coating. However, the desirable bulk properties of the elastomer such as the extensibility and modulus were retained. A dual-mode reactor, in which both low frequency (LF) and microwave (MW) power were applied to the plasma, was used to yield a deposition rate of approximately 280 nm min-1. During deposition, carrier gases (Ar and O2) were flowed through the reactor, along with the monomer (hexamethyldisiloxane, HMDSO). Batch depositions were performed to determine the reactor parameters that yielded the maximum deposition rate and the minimum coefficient of friction. Semi-continuous depositions were also performed by inserting an unwind and rewind mechanism into the reactor to produce a moving web that simulated an industrial coating process. The molecular structure of the deposited films was determined using attenuated total reflectance (ATR) infrared spectroscopy and found to consist of mainly Si-O-Si and Si-CH3 groups. The thicknesses of the films, and hence the deposition rates, were determined by variable angle spectroscopic ellipsometry (VASE). The coefficient of friction values for the films were determined by tribometry. A film thickness of approximately 100 nm usually resulted in a reduction in coefficient of friction of the SBR material to approximately 0.30. The SBR film was extremely sensitive to increases in the temperature of the LF electrode, due to the applied LF power. However, when the LF power was reduced to 15 W and the MW power was increased to 500 W, the SBR film was processed for a semi-continuous deposition lasting approximately 15 min. Approximately 10 ft of coated material with a low coefficient of friction were produced prior to the web failing due to heating. For the continuous processing of SBR film, the heating of the LF electrode must be controlled.
Advisors/Committee Members: Boerio, F. James.
Subjects: Engineering, Materials Science
Keywords: thin film; surface engineering
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22.
CHAVAN, HARSHAD S.
INVESTIGATION OF β-PHASE POLY (VINYLIDENE FLUORIDE) FILMS USING SMALL- ANGLE X-RAY SCATTERING.
Degree: MS, Engineering : Materials Science, 2006, University of Cincinnati
► Piezoelectric materials undergo a change in polarization in response to mechanical stress.…
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▼ Piezoelectric materials undergo a change in polarization in response to mechanical stress. The phenomenon is used in a variety of devices from sonar detectors to actuators. Although most piezo-materials are ceramics, some polymers have been found to display piezoelectric response. Poly (vinylidene fluoride) (PVDF) exhibits the strongest piezoelectric response of any commercially available polymer. The origin of piezoelectricity in PVDF is extensively debated in the literature. Studies have been attempted to understand structure-piezoelectric property relationships. Very little information is available on the morphology observed in PVF2. 2-dimensional small-angle and wide-angle x-ray scattering studies were performed to understand the lamellar morphology of PVDF (beta phase) films. This investigation revealed that there are two populations of lamellae of average spatial orientation. The lamellae are not perpendicular or parallel to the machine direction (MD), implied by the literature. It is found that lamellar plane normals make ± 42 – 48 degree angle with the MD and that lamellar long period was 80 – 89 Å . The effect of such a lamellar morphology on piezoelectric response and specifically bending piezoelectricity is discussed. It is thought that stress-induced lamellar rotation may play a role in piezoelectric response. Bending piezoelectric response in single films can be explained on the basis of a heterogeneous mesoscale structure. Structural features which need to be incorporated in models of piezoelectricity for PVDF films are discussed.
Advisors/Committee Members: Beaucage, Dr. Gregory.
Subjects: Engineering, Materials Science
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23.
Cho, Hoon-Sung.
Design and Development of a multifunctional nano carrier system for imaging, drug delivery, and cell targeting in cancer research.
Degree: PhD, Engineering : Materials Science, 2010, University of Cincinnati
► There has been an increasing need in the last decade for early…
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▼ There has been an increasing need in the last decade for early diagnosis and treatment of cancer prior to the tumor mass becoming evident as anatomical anomaly. A major challenge in cancer diagnosis is to distinguish cancer cells from the surrounding, normal tissue. For early cancer diagnosis and treatment, a nano carrier system was designed and developed with key components uniquely structured according to biomedical and clinical requirements: targeting, drug storage capabilities, fluorescent emissions near the infrared range for in vivo imaging, and magnetic hyperthermia. For in vivo imaging, quantum dots with emissions near infrared range (~800 nm) were conjugated onto the surface of carbon nanotubes and nanospheres consisting of a spherical polystyrene matrix (~100 nm) and high fraction of superparamagnetic Fe3O4 nanoparticles (~10 nm) embedded. The QDs on these nano carriers exhibited intense visible emissions using fluorescent spectroscopy and successfully facilitated in vivo soft tissue imaging in mice. For drug storage, the chemotherapeutic agent, paclitaxel (PTX) was loaded onto the surfaces of these nano-carriers by using a layer of biodegradable poly(lactic-co-glycolic acid) (PLGA). A cell-based cytotoxicity assay was employed to verify successful loading of pharmacologically active drug, PTX. Cell viability of human, metastatic PC3mm2 prostate cancer cells was assessed in the presence and absence of various nano-carrier populations using the MTT assay. For hyperthermia, Fe3O4 nanoparticles were conjugated onto the surfaces of carbon nanotubes (CNT) and embedded into the nanospheres. Magnetization measurements showed nearly reversible hysteresis curves from the Fe3O4-conjugated CNTs and the magnetic nanospheres (MNS). Application of an alternating electromagnetic field effectively induced heating the solution of the Fe3O4-conjugated CNTs and the magnetic nanospheres (MNS) into temperature ranges (up to 55 °C) suitable for therapeutic hyperthermia. PTX loaded nano-carrier systems were, then, developed by conjugating anti-Prostate Specific Membrane Antigen (anti-PSMA) for in vitro and in vivo targeting. Specific detection studies of anti-PSMA-conjugated nano carrier systems binding activity in LNCaP prostate cancer cells were carried out. Substantial differences were observed between the targeted- and non-targeted nano carriers. LNCaP cells were targeted successfully by the conjugation of anti-PSMA on the nano carrier surfaces. To explore in vivo targeting, the nano carriers conjugated with anti-PSMA were intravenously injected into nude mice bearing a human prostate cancer cell (LNCaP). Upon post-injection, significant fluorescence attributed to the nano-carrier system was detected, indicating substantial uptake in the region of the tumor.
Advisors/Committee Members: Shi, Donglu.
Subjects: Materials science
Keywords: fluorescent image; in vivo image; drug delivery; targeting; nanoparticle; multifunctional carrier
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24.
Chokalingam, Kumar.
Poly (Allylamine Hydrochloride) and Poly (Acrylic Acid) Multilayers for Gas Separation.
Degree: MS, Engineering : Materials Science, 2007, University of Cincinnati
► This work focuses on the formation of multilayers by layer-by-layer deposition of…
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▼ This work focuses on the formation of multilayers by layer-by-layer deposition of weak polyelectrolytes, poly (allylamine hydrochloride) and poly (acrylic acid). These multilayers were built on smooth surfaces (silicon wafer) and rough surfaces (Millipore membrane, clay-coated paper). The effect of concentrations, pH of the depositing polyelectrolyte solutions and drying between the absorption steps were investigated in films deposited on Si wafers. These films were characterized using ellipsometry, contact angle and AFM. In the pH ranges investigated in the study (2.5-4.5), at concentrations of 10-2 M and 10-1 M, the layer-by-layer deposition proceeds in a linear manner, with pH influencing the thickness of the bilayers. Thickness of the films increased with increase in the solution pH. The films deposited at higher concentrations showed higher thickness and roughness. Drying in all cases, lead to thinner and rougher films. Contact angle studies showed that the wettability of the polyelectrolyte multilayers is likely dependent upon the interpenetration of the underlying layer and can change with the pH of the solution. Drying had a significant effect when films were deposited at lower concentration but no effect when films were deposited at higher concentrations. Polyelectrolytes were also deposited on Millipore membranes and clay- coated papers. USAXS data on coated Millipore membranes showed that coating densified the fibers and also reduced the pore and solid chords. Permeation studies in coated Millipore membranes showed that bilayers increase the selectivity for CO2. Permeation studies in coated clay-coated paper showed that bilayers reduce water vapor permeability.
Advisors/Committee Members: Schaefer, Dr. Dale.
Subjects: Engineering, Materials Science
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25.
Connelly, Michael.
An Analysis of Innovation in Materials and Energy.
Degree: PhD, Engineering : Materials Science, 2010, University of Cincinnati
► This dissertation presents an analysis of innovation in engineering materials and energy…
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▼ This dissertation presents an analysis of innovation in engineering materials and energy sources. More than fifty engineering materials and fourteen energy sources were selected for an evaluation of the relationship between the yearly production activity and yearly patent counts, which may be considered as a measure of innovation, for each. Through the employment of correlation theory, best-fit and origin shift analyses, it has been determined here that engineering materials and energy sources display similar life cycle and innovative activity behaviors. Correlation theory revealed a relationship between the yearly production and yearly patent counts indicating the extent that production and innovation affect each other. Best-fit analysis determined that four-stage life cycles exist for both engineering materials (metals and non-metals) and energy sources. Correlation and best-fit indicators of an estimated Stage III are confirmed by the presence of an origin shift of the patent data when compared to the production data which indicates that patents, or innovation, are driving, or being driven by, production. This driving force could represent the constructive or destructive side of the innovative process, with such sides being delineated by a possible universal constant above which there is destructive innovative behavior and below which exists constructive innovation. The driving force may also illustrate the manner in which an engineering material or energy source transitions into an innovatively less active state, enter Stage IV and possibly become a commodity. A possible Stage V, indicating “Final Death”, is introduced in which production is on a steep decline with no signs of recovery. Additionally, innovatively active energy sources are often found to utilize or be supported by innovatively active engineering materials. A model is presented that can be used for the evaluation of innovation and production that can be applied to both engineering materials and energy sources that may be used to predict the innovative behavior of these resources in order that they can be more effectively allocated and utilized.
Advisors/Committee Members: Sekhar, Jainagesh.
Subjects: Materials science
Keywords: Innovation; Materials; Energy; Patents; Production; Life-cycle
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26.
CONNELLY, MICHAEL C.
THE RELATIONSHIP BETWEEN PATENTS AND TECHNICAL INNOVATION: INNOVATION MEASUREMENT AS APPLIED TO METALS.
Degree: MS, Engineering : Materials Science, 2007, University of Cincinnati
► This thesis defines and discusses the position of innovation in modern society.…
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▼ This thesis defines and discusses the position of innovation in modern society. Explored are the attempts to find an effective and reliable method for the measurement of innovation and innovative activity. Two schools of thought exist in reference to measurement, one suggesting the use of patents as the best indicator of innovative activity, and the other recommending alternative means not using patent data. The thesis proposes a method of measurement utilizing yearly patent counts. A model was developed using nine metals whose yearly production activity was correlated with patent counts associated with the same materials. This correlated data was then entered into best-fit equations to obtain fitted patent and activity life cycle curves. Differences in the origins of these fitted curves were interpreted as lags of time in the life cycle of the patent or activity allowing for comparisons between patents and innovative activity. The behavior of patents was found to be similar to that of the innovative process, making patents an accurate measure and representation of innovation.
Advisors/Committee Members: Sekhar, Dr. Jainagesh.
Subjects: Engineering, Materials Science
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27.
Deshpande, Pranav K.
Wear Resistance and Electrical Property of Infrared Processed Copper/Tungsten Carbide Composites.
Degree: PhD, Engineering : Materials Science, 2006, University of Cincinnati
► Copper matrix composites with 53 vol% of WC particle reinforcements have been…
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▼ Copper matrix composites with 53 vol% of WC particle reinforcements have been prepared with an infrared infiltration technique. The process produced fully dense composite owing to excellent wetting between copper and WC. The microhardness values of completely infiltrated Cu/WC composites were in the range of 360-370 HV which is significantly higher than the microhardness of pure copper, 65 HV. The electric conductivity of these composites, as determined by a four-point-probe method, is similar to commercially available Cu/W composites containing 52 vol% of tungsten. The wear behavior of Cu/WC composites has been determined with a pin-on-disk technique against a sintered SiC abrasive disk. The wear rate as a function of a normal wear stress and composite porosity was investigated. Results have shown that up to a normal load of around 9 N (or 0.55 MPa pressure), the wear rate of fully dense Cu/ WC composites increases linearly with the applied pressure. Results also show that porosity in the Cu/WC composite increases wear. A model of wear, taking into account various wear mechanisms, was developed. This model successfully predicts the wear behavior of dense Cu/WC composites. Owing to its significantly better wear resistance, as compared to Cu/W composites, the composition of Cu/ 53 vol% WC composite was varied by an innovative technique to improve the electrical conductivity of these composites without much compensation on its wear resistance. The technique of composition variation also helped in overcoming the shortcomings of pressure-less infiltration technique.
Advisors/Committee Members: Lin, Dr. Ray Y.
Subjects: Engineering, Materials Science
Keywords: Copper Composites; Electrical Contacts; Wear Resistance; Infrared; Pressureless Infiltration
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28.
Deshpande, Pranav Kishore.
Infrared Processed Copper-Tungsten Carbide Composites.
Degree: MS, Engineering : Materials Science, 2002, University of Cincinnati
► The objective of this study is to develop copper matrix composite for…
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▼ The objective of this study is to develop copper matrix composite for electrical contact application. Copper matrix composites with refractory material reinforcement have properties such as high electrical conductivity and high wear and erosion resistance, which make them a preferred candidate for electrical contact application. The approaches for making of these composites have been different not only in the selection of the type, size and shape of the reinforcements but also in the steps involved in its making. This study focuses on the particulate reinforced metal matrix composites produced by using the liquid metal infiltration process. The process consists of the injection and subsequent solidification of liquid copper within the interstitial spaces of a porous tungsten carbide preform. The two critical parameters of this process are temperature and pressure. While the temperature parameter is critical for the viscosity of the liquid metal to be sufficient and the superheat considerations, the pressure parameter plays an important role in forcing the liquid metal into the porous preform. The effect of temperature variation on the microstructure and properties of the composite has been discussed. The infiltration process in this study is without the application of any pressure with the capillary forces providing sufficient pressure drop at the infiltration front. The reliance on the capillary forces brings to fore the wettability aspect of the process. The need of favorable wetting behavior between the constituents cannot be overstated. Copper-tungsten carbide composites were prepared in a very short time using the infrared heating process. The composite produced has a significant increase in the hardness value (360-370 VHN) as compared to copper (170 VHN). The resistivity value of the composite (5.4 x 10 -6Ω-m) is very close to the resistivity value of copper (1.7 x10 –6Ω-m). The density value as close as 97-98% of the theoretical density value has been achieved. The microstructure shows homogeneous distribution of the constituent phases. The study lays foundation for some extensive work on the control of the volume fraction of the constituents and also the predictability of the process.70
Advisors/Committee Members: Lin, Ray Y.
Subjects: Engineering, Materials Science
Keywords: WC-CU composites; infrared technology; copper and composites
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29.
DHOKE, MANJIRI ARVIND.
POROUS POLYMER MEMBRANES AS SUPPORTING SCAFFOLDS FOR BILAYER UPID MEMBRANES (BLM).
Degree: MS, Engineering : Materials Science, 2005, University of Cincinnati
► The outer limiting boundary of a cell, the cell membrane, is a…
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▼ The outer limiting boundary of a cell, the cell membrane, is a bilayered lipid membrane and it gives the cell control over its internal environment. A realistic in vitro model of the cell membrane can help gain invaluable information about fundamental life processes. A self-assembled bilayer lipid membrane (BLM) made from phospholipids resembles the cell membrane in structure and function and can be used as a model. However, the mechanical and electrical instability of the BLM poses a major problem to its wide experimental study. The purpose of this work was to study and develop flexible and porous polymer membranes to act as supporting scaffolds for bilayer lipid membranes (BLM). Commercially available polycarbonate filters and laboratory synthesized porous poly (l-lactic acid) (PLLA) membranes were examined for the application. Lipid structure and BLM stability was determined by ion flow measurements. Ion flow measurements showed that deposition of phospholipids on a porous membrane resulted in a 3 orders of magnitude increase in its ion flow resistance. This increase in ion flow resistance indicated formation of dense ion impermeable structures in the pores of the membranes. On addition of Gramicidin- D, which is an ion channel forming molecule, to the above system, a drastic decrease in ion flow resistance was observed. This suggested formation of Gramicidin-D ion channels within the ion impermeable phospholipid structures. Gramicidin- D can form ion channels only across unit bilayer lipids. Thus, the decreased ion flow resistance pointed towards a stable bilayer structure within the membrane pores. Thus, stabilized BLM’s were formed in the membrane pores with the polymer membrane providing it mechanical stability. In a preliminary study utilizing another kind of an ion channel, Kv1.5 potassium ion channels were successfully reconstituted within BLM’s supported by PLLA membranes. These studies have led to the conclusion that membranes with pore sizes of 3-10µ with an aspect ratio nearing 3 are good scaffolds for BLM stabilization. Also, better pore structure uniformity aids BLM formation and stabilization.
Advisors/Committee Members: Boerio, Dr. F.J.
Keywords: Bilayer Lipid Membranes, Polymers Membranes, Poly (l-lactic Acid)
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30.
Dutta, Indrajit.
Electro-Mechanical Behavior of Strontium Modified Lead Zirconate Titanate Ceramics.
Degree: PhD, Engineering : Materials Science, 2007, University of Cincinnati
► Since the discovery of perovskite ferroelectrics, the solid solution of PbZrO3-PbTiO3 (PZT)…
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▼ Since the discovery of perovskite ferroelectrics, the solid solution of PbZrO3-PbTiO3 (PZT) system is intensively studied due to its excellent electro-mechanical properties for transducers and actuators applications. The strontium modified PZT (PSZT) at the Zr rich end shows a long antiferroelectric-ferroelectric boundary suitable for field induced phase transition study and associated electro-mechanical behavior study. A modified oxide route was developed to process PSZT ceramics with different Zr4+/Ti4+ ratios for repeatable ultra-high strain applications. Repeatable ultrahigh strain of ~ 0.8% was achieved for PSZT compositions near the AT-FR phase boundary. Other compositions showed strain (0.35-0.8%) which were still better than the commercially available materials of same class. The PSZT ceramics showed high polarization response as well. Polarization over 41µC/cm2 was observed for certain ceramics on the FR side. A novel dynamic in-situ X-Ray diffraction was conducted on the different PSZT ceramics to understand the field induced electromechanical property changes. The ultrahigh strain in these materials, on the antiferroelectric tetragonal side of the phase diagram, was found to be due to unit cell volume change along with the movement of the non 180° domains. For the rhombohedral ferroelectric materials the strain was mostly contributed by the unit cell volume increase. Compositions farther away from the boundary in the AFT side did not show any structural change or domain movements. Electrical fatigue behavior of PSZT ceramics was investigated by subjecting the as-sintered ceramics to low frequency (30 Hz) electric field up to 107 cycles. The fatigue free polarization behavior (<10% degradation) was attributed to the high density and low porosity of the PSZT ceramics. The high strain degradation nature (~50% degradation) was found to be partially due to internal stress development during the electrical cycles and partially due to the formation of fatigue induced mechanical damage layer under the electrode. Thermal annealing and removal of the damaged layer showed the complete recovery of the strain to its original as-sintered value. Some preliminary electric fatigue experiments with electron beam deposited aluminum (Al) electrode were conducted on PSZT ceramics. The results showed promising fatigue resistance behaviors.
Advisors/Committee Members: Singh, Raj N.
Subjects: Engineering, Materials Science
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