A method for the preparation of submicron, monodispersed, spherical particles of aluminum hydrous oxide has been developed. The method consists of the hydrolysis of aluminum acetylacetonate in alcoholic solution by the direct addition of a base at room temperature. The effects of the process parameters including temperature, solvent, type and concentration of base, aluminum acetylacetonate concentration, and stirring time are examined as well as the process reproducibility, particle composition and particle stability. Results obtained have shown that monodispersed particles can be formed with a mean particle diameter of eighty five to two hundred and fifteen nanometers and the mean size is reproducible to within ten percent of the mean diameter. Particles that are redispersed in fresh solvent are stable for at least thirty days. A model is proposed which explains the kinetics of particle growth and the influence of experimental parameters such as temperature, pH, concentration and the solvent on the formation of particles.

Most ceramic articles are produced by first dispersing powders in a suitable liquid, forming the dispersion (by casting, molding, extrusion, etc.), drying and then firing the body to its final sintered state. It has been recognized that dispersion characteristics strongly affect the green body which in turn determines properties of fired ceramic, and recently, dispersion science has become quite important in the development of ceramics processes. In this thesis research, colloidal size alumina powder was dispersed in secondary butyl alcohol with a phosphate ester dispersant. Dispersions were produced in an attrition mill and evaluated by viscometry and sedimentation. These dispersions were "optimized" by adjusting surfactant concentration and milling time. Zeta potential measurements indicated stabilization was not purely electrostatic. It was noted that a small amount of water added to the dispersions dramatically affected dispersion rheology. With slight water addition high solids content slurries (40 vol. percent) could be produced with rheological characteristics desirable for casting. Solution conductivity measurements were made to provide insight into the possible mechanism by which water affects dispersion stability.

A method for the synthesis of submicron copper coated polystyrene particles by electroless deposition has been developed. In this technique, the carboxylated and sulfated polystyrene latex particles of 0.1 μm and 0.24 μm diameter, are first activated by conditioning in a solution of tetraammine palladium (II) chloride monohydrate and then plated in an electroless bath containing cupric sulfate, EDTA-disodium salt, some stabilizers and basic formaldehyde at 72 ± 1°C. The interaction between carboxylic acid groups and Pd(NH₃)₄Cl₂.H₂O has been studied using uv spectroscopy. Copper coated carboxylated polystyrene particles with a mean diameter of 0.4 μm and a standard deviation of 9% of the mean diameter have been synthesized. The size, shape and purity of these particles have been determined by SEM, EDX, and ESCA analysis. The microcrystallinity of the particles has been determined by XRD technique.

Phase separation in glass systems has been studied since the turn of the century, and has developed commercial interest with the VYCOR process and recent interest in glass-ceramics. Phase separation has been studied in the lead borate glass system because it is known to separate across a fairly wide compositional range, and has been shown to undergo both stable and metastable phase separation. To further understand immiscibility in the lead borate system, an investigation has been performed to determine the immiscibility gap under nearly equilibrium conditions. Small-angle x-ray scattering (SAXS) has also been used in an attempt to characterize the kinetics of phase separation of a high-lead composition in the metastable region, using novel sample preparation methods.

Copper aluminosilicate (composition Cu₂O·Al₂O₃·6SiO₂) glass was melted in an alumina crucible at 1500°C and air cooled in situ. A layer of cupric oxide was grown on the polished glass surface and its thickness measured using a scanning electron microscope (SEM). The thickness of the oxide layer was found to increase parabolically with time, with a temperature dependency that was compatible with the diffusion of copper through the layer. The cupric oxide layer was reduced to copper on roughened and polished glass surfaces using a gas mixture of 3% H₂ and 97% N₂, resulting in a glass substrate coated by copper. Adherence of the copper layer to the polished glass substrate was found to be poor. However, adherence was found to increase by roughening the surface before oxidation. Additions of NiO and CaO to the base glass were not detrimental to the production of the copper film.

Various coolant chemicals are known to have enhancing and suppressing effects on wear and the quality of finish, but little has been understood about the nature of these effects. Studies were performed to examine the effects of pH and surface bias on wear, subsurface damage, and the various theories of chemical interaction with the wear process. Results of this examination of wear suggest that chemical adsorbates can play a significant role in wear fracturing. Previous observations of plastic mechanisms in brittle wear have lead tribologists to suggest that chemically induced changes in plasticity are the cause of these effects. Instead, this thesis contends occurrence of plastic effects to be by-product of localized hydrostatic compression and insufficient stress intensity to cause fracture. Crack rates and stress intensities required for fracture to occur are known to vary with adsorption.

In this work a new wet-chemical method of preparing tungsten oxide thin films is described. This involves the dissolution of tungsten metal in aqueous hydrogen peroxide and reaction with acetic acid to form an alcohol-soluble precursor. All synthesis stages of this new precursor, termed peroxotungstic ethoxide, are characterized to determine possible reactions. The chemical and microstructural evolution of films is described as a function of firing temperature, utilizing infrared spectroscopy, diffraction and other optical data. A novel method of increasing the crack-free thickness of the films is given: a combination of oxalic acid dihydrate as a solution additive and film firing under controlled humidity. With this combination, fired crack-free films up to one micron in thickness were prepared. Oxalic acid dihydrate roughened and also caused crystallization of these films at lower temperatures (250°C) than expected. These rougher films exhibited an improved electrochromic response, as measured by optical and electrochemical characterizations.

<p> In this study, the performance of a Gold-Copper alloy has been examined in order to explore the possibility of its use as a cathode catalyst in a Proton Exchange Membrane (PEM) Fuel Cell. The performance of Oxygen Reduction Reaction (ORR), which occurs at the cathode, is evaluated using the Density Function Theory (DFT) computational code, SeqQuest. A surface segregation study is performed to identify a low energy surface of the catalyst. A binding site analysis of various intermediate molecules that occur during the ORR process is performed. The intermediate reactions of the ORR are simulated on the surface. Using the binding energies and energy barriers, the pathway that the Gold-Copper alloy prefers to follow is determined. The alloy is found to be a promising catalyst as it prefers to take the four electron pathway. An estimation of the Current Density has been made, and the effect the operating temperature has on it is observed.</p>

<p> In this work, beneficial effects of tensile mean strain on fatigue behavior and microstructure of superelastic NiTi (i.e. Nitinol) are studied. Most applications, such as endovascular stents made with NiTi, are subjected to a combination of constant and cyclic loading; thus, understanding the fatigue behavior of NiTi undergoing mean strain loading is necessary. Cyclic strain-controlled fatigue tests are designed to investigate the effects of tensile mean strain on fatigue of superelastic NiTi. Experimental observations show that combinations of large tensile mean strains and small strain amplitudes improve the fatigue life of superelastic NiTi. This behavior arises from reversible, stress-induced phase transformations. The phase transformations cause &ldquo;stress plateaus&rdquo; or strain ranges with no change in stress value. Scanning electron microscopy (SEM) of the fracture surfaces of specimens revealed generally short crack growth. Electron backscatter diffraction (EBSD) found the amount of residual martensite to be about ~8%, regardless of loading conditions.</p>

<p> Carbon-fiber composites are increasingly employed in the Aerospace and Automotive industries owing to their lightweight and excellent mechanical properties. However, this class of material, when subjected to out-of-plane loads, is often susceptible to an internal damage in the form of delamination that can severely reduce its load bearing capacity. Several toughening methods including the implementation of thermoplastic materials are used to increase the damage tolerance of the polymer-matrix composites. In particular, non-woven thermoplastic veils, when used as interleaving materials between the plies in a composite structure, is extremely efficient at improving the interlaminar (delamination) fracture toughness and impact-resistance of composites. In addition, the toughening of the polymer matrix, if not adversely affecting the manufacturing process, can result in an increase in the toughness-related properties of composite laminates such as the resistance to micro-cracking under thermal-cycling conditions. </p><p> In this study, the effects of matrix toughening and interleaving of the composite with non-woven Polyamide (PA) veils on the Interlaminar Fracture Toughness (ILFT) of Carbon-fiber/Benzoxazine composites are investigated. Formulated Benzoxazine (BZ) resins in non-toughened and toughened variants along with several non-woven PA veils with different melt temperatures are used to manufacture composite laminates through the Vacuum Assisted Resin Transfer Molding (VARTM) process. The ILFT of composites is measured by obtaining the resistance to crack propagation in the interlayer under tensile forces (Mode-I ILFT) or shear forces (Mode-II ILFT). The critical strain energy release rate (Gc) recorded during interlaminar fracture gives a measure of the ILFT of a composite. </p><p> The laminates interleaved with the PA veils show an increase of nearly 50% for the Mode-I crack initiation (GIc initiation), regardless of the melt temperature of the PA veils. The Mode-I crack propagation (GIc propagation) of the laminate increases by using the PA veils with melt temperatures lower than the cure temperature of the BZ resin. </p><p> In the Mode-II ILFT (GIIc) tests, the laminates interleaved with the PA veils show a significant impact on the GIIc values, as increases of nearly 170% are observed. A strong correlation between PA melt temperatures and the GIIc values is noted. The greatest GIIc values are noted when the melt temperature of the PA veil is greater than the cure temperature of the BZ resin. </p><p> The matrix toughness plays a significant role in affecting the GIc values. The laminates manufactured with the toughened BZ resin result in the greatest increase in the GIc values. In contrary, the use of the toughened BZ resin does not result in an improvement in the GIIc values.</p>