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.

No description available.

No description available.

Multilayer polymer systems are a focus of increasing research effort motivated by the possibility to realize compact and flexible energy storage and energy harvesting devices. However, the performance and stability of these polymer systems are highly dependent on temperature. In this study the structure of monolayer ferroelectric polyvinylidene fluoride (PVDF) thin films and the relaxation dynamics as a function of temperature are characterized using XRD, FTIR and second harmonic generation (SHG). Multilayered ferroelectric polyvinylidene fluoride (PVDF) systems are fabricated using enabling technology in co-extrusion for increased energy storage and energy harvesting efficiency as well as increased stability at elevated temperatures. To understand the physics of why these multilayered systems perform better than single layer PVDF characterization techniques using second harmonic generation (SHG), electric field induced second harmonic (EFISH) and Raman laser spectroscopy are developed. Results show that the combination of Raman and SHG is a very sensitive, non-destructive and versatile technique that can be used to study the ferroelectric and structural properties of these systems. The addition of the EFISH technique allows the interrogation of structural and dielectric properties within individual layers and at the interfaces.

An Ion Selective Conductimetic Microsensor (ISCOM) for the detection of cesium ions was devleoped. The operating principle of an ISCOM is based on the concentration dependant change in the bulk conductivity of an ion selective membrane. Changes in conductivity are achieved by salt extraction of the target ion into the bulk of the membrane that is formed on top of a planar interdigitated electrode, thus allowing the monitoring of the membrane conductivity. Characterisation of the planar interdigitated electrode was undertaken using numerous techniques. This that that there was considerable inter-diffusion of the elemental layers comprising the subsurface structure of the electrode and allowed the identification of chromium as a contaminant. This was reported back to the electrode manufacturers and subsequently removed. Thermodynamic analsysis indicated that the elements of the surface of the electrode would not present any problems (background signal etc) during the normal operation of the ISCOM device. A method for the deposition of the ion selective membrane onto the electrode was developed. Initially the membrane was formed in a well on the electrode surface that was created by the lamination of additional layers onto the device structure. This method was abandoned due to the high failure rates of these devices caused by solution seepage under the laminated layer resulting in it peeling away from the electrode structure. The second method used was the forming of a membrane by direct drop coating i.e. application of a drop of the membrane on to the electrode. This work indicated that greater sensitivity could be obtained with thinner membranes. The final method to be used was the spin coating of the ion selective membrane onto the electrode surface. This work demonstrated that the greatest sensitivity, and response times of less than 15 seconds, were achieved when spin coating was conducted at speed of 1000 rpm or grater. In addition to this the response of the ISCOMs was found to linearly related to the square root of the target ion concentration. An analysis of the eeffect on device sensitivity of the composition of the ion selective membrane in terms of the relative level of membrane components was undertaken usign the experimental design software MODDE 6.0. This showed that the optimal membrane composition was 10% ionophore, 20% polymer and 70% pasticiser. Such membrances have a limit of detection of 4.95 x 10 M cesium. The selectivity of the cesium ISCOM was analysed using a semi-empirical method develoepd for this sensor from data generated using a method based on teh Fixed Inference Method (FIM) for the determination of ISE selectivity. It was found that the selectivity of the cesium ISCOM was comparable to that reported for ISEs. Particularly the interference by rubidium in the ISCOM system is the lowest of any sensor system reported to date with logks value of -2.22. The results for preliminary investigations into the device lifetime are also presented.

This thesis explores the possibility of alternatives to copper lining inside the water heater tank in water heaters. The need for an alternative is based on the increasing copper prices the recent years. The aim of this thesis is to compare three different materials, stainless steel, copper and a nickel coated plain carbon steel. This comparison is based on a basic corrosion test and a literature survey to render a merit value for each environment/metal interface. The testing solution consists of 100ppm Cl - concentration the specimens are tested in three different pH levels and at three different temperatures. The specimens have their weight measured before and after the test. The 15μm thick nickel coating was performed by Ferroprodukter AB, composing of 9% P and 91% Ni. The copper and stainless steel specimens are both from Thermia’s actual water heater tank. The copper lining is made of pure copper and the stainless steel hull is made of ferritic stainless steel. The results from the corrosion test are measured in weight change by modulus, |Δw|/w, for the comparison of the three materials. It was found that stainless steel was the worst material, performing better at higher temperatures and higher pH , but overall performance is far from copper and nickel’s corrosion properties. The nickel coating and copper specimen showed comparable results and perform more or less equally well. Regarding identification of corrosion mechanics, it may consist of either pitting and general corrosion damage or a mixture of both. To avoid the fact that weight change may be both negative and positive, the solution to this was to incorporate a merit value based on the absolute value of the weight change, divided by the initial weight of the specimen. In conclusion, stainless steel total weight change by modulus accumulates to 16.072g, nickel coated specimen accumulates a weight change by modulus equal to 8.544g, important note: two of the nickel coated specimen account for ~72.4% of the total weight change by modulus which then accumulates to 2.36g. Copper’s total weight change by modulus was 2.937g thus the lowest. However, disregarding from the 90캜 regime; stainless steel scores 13.496g, copper 2.151g, and nickel 1.095g.

<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>