n/a ----Introduction---- I have presented my dissertation in four specific parts as specified on page 2 of the "Guidelines For Internship Requirements of Master of Applied Science in Material Conservation": Part I: Details of the programme of work carried out Part 11: Description of the function and facilities of the Canadian Conservation Institute Part 111: Details of conservation work carried out: Examination and Treatment Reports Part I V : A. Technical Training Sessions and Lectures B. Visits t o Conservation Laboratories C. Visits to Cultural Institutions Each part can be considered a separate unit and, therefore, the bibliography pertaining to each section follows it immediately, contrary to the usual format of being placed as an entire unit at the end of the dissertation. The use of photographic reproduction and official documentation is restricted for ethical, political, legal, security and other reasons (Appendix 11). Therefore, limited photographic documentation is evident in the treatment reports presented. The CC1 Examination and Treatment format did not comply with the size specifications for the dissertation. Therefore, it was not used. However, the following forms have been reduced and presented in Appendices 111, I V and V: Request for Conservation Services, Request for Analytical Services and Time Log on Work for the National Museum of Man. In addition to the examination and treatment reports, I have chosen to include a literature survey of the tannic acid treatment for ferrous metals. The literature survey increased my understanding of the treatment.

Electrochemical techniques have potential for use in conservation, both to evaluate the protectiveness of existing coatings on metal artefacts and to evaluate potential new conservation coatings. Three electrochemical methods have been examined in this study for their applicability to conservation problems. Corrosion Potential Measurement is simple but provides only minimal information on the corrosion processes occurring in an electrochemical system. Electrochemical Impedance Spectroscopy provides both mechanistic and predictive information on coating performance, but the data are complex to interpret and measurements require equipment that is at present too bulky for effective on-site use and beyond the budget of most conservation laboratories. Electrochemical Noise Measurement can be performed using cheap, portable instrumentation and theoretically requires relatively simple statistical processing and interpretation, making it attractive for conservation applications. This project looks at the development of a simple, low cost electrochemical noise measurement system for conservation needs, and uses it to compare Electrochemical Noise Measurement with the other two techniques.

<p> The mechanisms operating during the metal-assisted growth of III-V nanowires (NWs) by molecular beam epitaxy on (1 1 l)B substrates were investigated through a series of experiments aimed at determining the influence of growth conditions on the morphology and crystal structure. Using GaAs as the principal material system for these studies, it is shown that a good control of these two characteristics can be achieved via a tight control of the temperature, V /III flux ratio, and Ga flux. Low and intermediate growth temperatures of 400°C and 500°C resulted in a strongly tapered morphology, with stacking faults occurring at an average rate of 0.1 nm^(-1). NWs with uniform diameter and the occurrence of crystal defects reduced by more than an order of magnitude were achieved at 600°C, a V /III flux ratio of 2.3, and a Ga impingement rate on the surface of 0.07 nm/s, and suggest the axial growth is group V limited. Increasing the flux ratio favored uniform sidewall growth, thus making the process suitable for the fabrication of core-shell structures. Further observation of steps on the sidewall surface of strongly tapered NWs suggests that radial growth of the shell proceeds in a layer-by-layer fashion, with the edge progressing in a step-flow mode toward the tip. </p> <p> From the experimental considerations, an analytical description of the growth is proposed, based on a simple material conservation model. Direct impingement of growth species on the particle, coupled to their diffusion from the sidewall and the substrate surface, are considered in the derivation of expressions for the time evolution of both axial and radial growths. Factors that take into account the nonunity probability of inclusion of group III adatoms in the axially growing crystal are introduced. Moreover, a step-mediated growth is included to describe the axial evolution of the shell. </p> / Thesis / Doctor of Philosophy (PhD)