Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1902. / S. M. Greenidge determined to be Samuel Marshall Greenidge from "Forty-Firth Annual Catalogue. School of Mines and Metallurgy, University of Missouri". The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed December 4, 2008)

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Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references: leaf 247-269.

Typescript. Includes vita and abstract. Includes bibliographical references (leaves 130-137). Abstract also available online in ProQuest, free to University of Oregon users.

Thesis (Ph.D.)--McMaster University (Canada), 1991. / Source: Dissertation Abstracts International, Volume: 53-01, Section: B, page: 0503. Supervisor: I. D. Brown.

In general, the bearing alloys have two types of microstructure i.e., either a soft matrix with discrete hard particles or a continuous matrix of the harder metal with small amount of the softer metal finely dispersed in it. The aluminium and copper based bearing alloys which are widely studied fall in the second category. However, the bearing materials which have been studied have micron sized dispersoids. In recent times, it is possible to produce nanoscale dispersoids in a hard matrix by the novel processing route of rapid solidification. This offers an opportunity to study the small length scale effect on tribological processes. In this thesis, we deal with aluminium alloys where nanoscaled dispersions of lead, bismuth and indium are produced by rapid solidification processing. Chapter 1 of the thesis is an introduction, followed by Chapter 2, which reviews the literature on nanomaterials. Special attention is given to the monotectic system, followed by a brief description on friction and wear of materials which is necessary for our present investigation. The details of experimental and characterisation techniques are given in Chapter 3. In Chapter 4, we present a brief study of white metal bearings (babbit). Tin-based babbit of composition, Sn-6wt% Cu-llwt% Sb was studied. The study of babbit was mainly carried out with the idea that it could serve as a benchmark for subsequent studies in aluminium alloys, in terms of tribological properties. In particular, we have carried out a detailed electron microscopic investigation on the phases present in the bearing alloy. The friction and wear behaviour of this material confirms the proper calibration of our setup for wear studies. This is followed by a detailed study on the synthesis, microstructure and tribological behaviour of nanodispersed aluminium alloys, Al-6wt% Pb and Al-10wt% Pb in Chapter 5. For comparison, we have also studied melt-spun aluminium without dispersoids. Detailed electron microscopic characterisation indicates that lead has a cube on cube orientation relationship with the aluminium matrix, and the particles exhibit a lognormal distribution with the mode of the particle size distribution being 15 nm. The pin on disc results suggest a distinct lowering of coefficient of friction corresponding to pure aluminium (μ= 0.40) and as cast aluminium-lead alloys (μ= 0.41). Detailed SEM studies indicate a tribolayer consisting primarily of Al, Pb and Fe. The later comes from the counterface material. Our results clearly indicate that at an early stage, little or no oxidation takes place at the sliding interface. TEM observations indicate significant deformation of lead particles in the sub-surface region. The observations suggest spreading of the lead, which acts as a lubricating layer. Wear behaviour is primarily adhesive and follows Archard's wear law. However, the rate of wear is less than that reported by other investigators on micronsized lead dispersions in aluminium. In Chapter 6, we present the results for alloys dispersed with nanosized indium and bismuth. We show that indium particles on melt-spinning exhibit both cubic and tetragonal crystal structure. The indium particles are coarser (with a mode of 25 nm) than the lead and bismuth particles (which have mode of 15nm). The bismuth containing alloys have a lower wear rate and coefficient of friction compared to lead and indium alloys. However, both indium and bismuth particles do not follow Archard's wear law and the wear vs load graph shows a non-linear behaviour. The results are discussed in terms of known mechanisms of the coefficient of friction and wear. Chapter 7 gives the salient conclusions while in Chapter 8 we discuss some of the unanswered questions and the potential for future work in this field.

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Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-22T14:03:18Z No. of bitstreams: 0 / Made available in DSpace on 2017-11-22T14:03:18Z (GMT). No. of bitstreams: 0 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Nas últimas décadas, o consumo de dispositivos eletrônicos e a alta demanda por armazenamento de dados tem mostrado grandes oportunidades para a criação de novas tecnologias que garantam as necessidades mundiais na área de computação e desenvolvimento. Alguns materiais multiferroicos tem sido amplamente estudados e o BiFeO3, considerado o único material multiferroico em temperatura ambiente, ganhou destaque como candidato para produção de dispositivos lógicos e de memória. O uso de técnicas de crescimento como a deposição por laser pulsado permitiu a produção de filmes finos de BiFeO3 com elevado controle de qualidade. Heteroestruturas de filmes multiferroicos de BiFeO3 e LaBiFeO3 foram crescidas com diferentes espessuras sobre substratos de SrTiO3(100), DyScO3(110) e SrTiO3/Si(100) para avaliação e teste de suas propriedades elétricas e magnéticas. Filmes ferromagnéticos de Co0,9Fe0,1 foram depositados por sputtering sobre os filmes multiferroicos para avaliação da interação interfacial entre ordenamentos magnéticos. Técnicas como fotolitografia foram utilizadas para padronização de microdispositivos gravados sobre as amostras. Tanto os filmes finos de BiFeO3 como os de LaBiFeO3 foram crescidos epitaxialmente sobre os substratos já cobertos com uma camada buffer de SrRuO3 usado como contato elétrico inferior. A estrutura cristalina romboédrica das ferritas de bismuto foi confirmada pelos dados de difração de raios X, bem como a manutenção de tensão estrutural causada pela rede cristalina do substrato para amostras de 20 nm. Os valores de coeficiente do tensor piezelétrico d33 foram da ordem de 0,15 V (∼ 60 kV.cm-2) para amostras com 20 nm de espessura enquanto que os valores de voltagem coerciva para as análises de histerese elétrica foram da ordem de 0,5 V para as mesmas amostras. A relação de coercividade elétrica com a espessura corresponde ao perfil encontrado na literatura pela relação E≈d-2/3. As amostras de CoFe/BFO e CoFe/LBFO depositadas em diferentes substratos apresentam acoplamento interfacial entre ordenamento ferromagnético e antiferromagnético com momento ferromagnético de rede. / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP / CAPES:99999.009511/2014-08 / CNPq:146622/2013-2