To enable improvements in the development of anti-corrosive coatings quick methods of evaluation are required and several are available which are both qualitative and quantitative. This investigation reviews both types of method, the first in the form of traditional salt spray exposure and the second in the form of electrochemical techniques. The emphasis in the experimental work reported here is on the Electrochemical Noise Measurement (ENM). ENM has been used to monitor coatings under immersion conditions, the aim being to assist a paint company develop a set of more environmentally friendly coatings. The immersion test has also incorporated a temperature cycle which proved effective at separating ‘good’ coatings within a short timeframe. Results showed good correlation between ENM and salt spray testing. Work is also reported which was done with the aim of making the ENM method more practically useful. The standard configuration (‘Bridge’) requires two separate specimens which is unattractive for site work. The Single Substrate (SS) arrangement was developed to get around this problem but this still requires the metal to be connected to the measuring instrument. This is avoided in the most recent development which needs No Connection to Substrate (NOCS). Results are given for immersed samples monitored using the ENM NOCS arrangement and compared with the standard ‘Bridge’ method and DC resistance. Results are also presented using sets of different electrodes (platinum, calomel and silver/silver chloride). This preliminary work has shown that the NOCS method holds great promise. In the laboratory Electrochemical Impedance Spectroscopy (EIS) is also commonly employed to assess the performance of anti-corrosive coatings. Concluding this work a comparison of the ENM and EIS techniques was undertaken on a set of laboratory samples. Results showed that both methods had the ability to rank the performance of coatings. However ENM’s advantages (as outlined above) were confirmed

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No description available.

Simple technologies are required for reducing the post harvest losses of horticultural produce. Edible films are being studied extensively for application on fresh and cut fruits and vegetables. Tomato, being a very nutritious and important food and a highly perishable climacteric fruit, this study was planned to investigate the application of chitosan films. Chitosan is a biodegradable waste product from sea food and is safe for consumption. With a view to broaden its antimicrobial activity it was combined with lysozyme, a lytic enzyme. Since the edible films are sensitive to changes in temperature and humidity, they were studied under ambient and optimal conditions of storage. / This study showed that 1% chitosan was more suitable for tomatoes for storage at both conditions of ambient and low temperature. Respiration study showed that 1% chitosan treatments resulted in more favorable levels of CO 2 production and internal O2. This was reflected in the quality of tomatoes held under these conditions. Two per cent chitosan films were unsuitable due to their high CO2 production and low internal O 2 levels. Spoilage was more apparent in this treatment. Lysozyme addition did not show any additional benefit. / The research in this study has demonstrated that the selection of edible films for horticultural produce needs to be integrated with the requirement of storage conditions of the produce.

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Atomic vapors condensed onto solid surfaces form a remarkable category of condensed matter materials, the so-called thin films, with a myriad of compositions, morphological structures, and properties. The dynamic process of atomic condensation exhibits self-assembled pattern formation, producing morphologies with atomic-scale three-dimensional structures of seemingly limitless variety. This study attempts to shed new light on the dynamical growth processes of thin film deposition by analyzing in detail a previously unreported specific distinct emergent structure, a crystalline triangular-shaped spike that grows within copper and silver thin films. I explored the deposition parameters that lead to the growth of these unique structures, referred to as ``nanospikes'', fabricating approximately 55 thin films and used scanning electron microscopy and x-ray diffraction analysis. The variation of parameters include: vapor incidence angle, film thickness, substrate temperature, deposition rate, deposition material, substrate, and source-to-substrate distance. Microscopy analysis reveals that the silver and copper films deposited at glancing vapor incidence angles, 80 degrees and greater, have a high degree of branching interconnectivity between adjacent inclined nanorods. Diffraction analysis reveals that the vapor incidence angle influences the sub-populations of crystallites in the films, producing two different [110] crystal texture orientations. I hypothesize that the growth of nanospikes from nanorods is initiated by the stochastic arrival of vapor atoms and photons emitted from the deposition source at small diameter nanorods, and then driven by localized heating from vapor condensation and photon absorption. Restricted heat flow due to nanoscale thermal conduction maintains an elevated local temperature at the nanorod, enhancing adatom diffusion and enabling fast epitaxial crystal growth, leading to the formation and growth of nanospikes. Electron microscopy and x-ray diffraction analysis, and comparisons to related scientific literature, support this hypothesis. I also designed a highly modular ultrahigh vacuum deposition chamber, capable of concurrently mounting several different pieces of deposition equipment, that allows for a high degree of control of the growth dynamics of deposited thin films. I used the newly designed chamber to fabricate tailor-made nanostructured tantalum films for use in ultracapacitors, for the Cabot Corporation. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2011-01-17 15:22:47.533

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No description available.

No description available.

This study investigated the corrosion of an aluminum alloy with and without coatings under simulated corrosive environments. Coatings were selected and applied from commercial materials and techniques, consisting of microceramic, epoxy primer, and topcoat. The experiments for coated specimens were carried out under various corrosive conditions, specifically, hydrodynamic flow, immersion in salt water and DI water, varying temperatures, and simulated sun light. The hydrodynamic conditions were simulated using a rotating cylinder electrode (RCE) with rotational speeds of 200, 400, 600, 800, and 1000 rpm. The immersion in saltwater and sunlight illumination tests were applied for 8 hours, and the simulated exterior temperature variation were cycled for 7 days. Polarization techniques were used to study the corrosion mechanism and calculate the corrosion rate of coated specimens under simulated salt water. Microstructure of coated specimens were identified by using atomic force microscopy (AFM) and optical microscope (OM) analysis. Results indicated that corrosions in the simulated salt water were generally more serious than those in the distilled water. This was especially true for bare aluminum alloys, that its corrosion rates in the salt water exhibited two orders of magnitude higher than those in the DI water. The combination of an environmentally friendly electrodeposited ceramic coating with a primer and topcoat, which results in a chromium-free coating, exhibited a higher polarization resistance and a lower corrosion rate than the traditional chromate conversion coating combination. In addition, for all coated Al alloys, the corrosion rate increased with increasing rotation speed. For immersion portion, immersion in salt water accelerated the pitting corrosion process and increased the corrosion rate of the aluminum alloy five times higher as compared to the samples without immersion. For the varying temperature portion, the rates of corrosion nearly doubled for bare and ceramic coated Al alloy, under varying temperature conditions for 7 days. Besides, addition of ionic liquid inhibitors, such as BMIMBR and BEIMCl, exhibited great improvement of corrosion resistances of aluminum alloy in the salt water. The corrosion rates of aluminum in the presence of inhibitors were almost one order of magnitude lower than that in the absence of inhibitors.