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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Efeito autorreparador em primer carregado com inibidor de corrosão encapsulado em haloisita. / Self-healing effect of primer loaded with corrosion inhibitor encapsulated in halloysite.

Carvas, Gabriela Silva Ferreira 14 June 2019 (has links)
O objetivo deste trabalho é avaliar o efeito autorreparador de um primer alquídico base solvente (SB) e um primer acrílico base água (WB) aditivados com nanocontainers de haloisita carregados com inibidor de corrosão dodecilamina (DDA) aplicados em aço carbono. O efeito inibidor da dodecilamina foi avaliado através de ensaios eletroquímicos de espectroscopia de impedância eletroquímica (EIS) em diferentes condições, sendo verificada que a sua eficiência aumenta em meio ácido. Com o intuito de aumentar o lúmen da haloisita, gerando mais capacidade de carregamento de inibidor, a haloisita foi tratada com ácido sulfúrico 2 mol/L por 6 h a 55 °C. A haloisita tratada foi caracterizada através de análises termogravimétricas (TGA) e microscopia eletrônica de varredura (MEV). Em seguida, a dodecilamina foi carregada em haloisita tratada, através da técnica de pulso de vácuo. A cinética de liberação do inibidor de dentro da haloisita foi estudada através da técnica de EIS, onde foi constatada que a sua atuação é dependente do pH, com maior velocidade de liberação em pH 2. Os nanocontainers foram adicionados em um primer alquídico base solvente e um primer acrílico base água para a avaliação da resistência à corrosão dos sistemas através de espectroscopia de impedância eletroquímica (EIS), técnica de varredura com eletrodo vibratório (SVET) e ensaios acelerados de corrosão em câmara de névoa salina (SSC). A aderência dos dois sistemas foi avaliada através do ensaio de aderência por tração (pull-off). Para os dois sistemas avaliados foi possível verificar o efeito autorreparador, porém ele não foi tão longo, provavelmente devido à baixa eficiência no carregamento da dodecilamina na haloisita. A análise de custo da haloisita carregada com dodecilamina mostrou a necessidade de otimização dos processos de carregamento a fim de viabilizar o projeto na indústria de tintas. / The aim of this work is to evaluate the self-healing effect of a solvent based (SB) alkyd primer and a water based (WB) acrylic primer loaded with dodecylamine (DDA) corrosion inhibitor encapsulated in halloysite nanocontainers on carbon steel. The inhibitor effect of dodecylamine was evaluated by electrochemical impedance spectroscopy (EIS) under different conditions, and it was verified that its efficiency increases in acid medium. To enlarge halloysite lumen and increase its loading capacity, halloysite was treated with 2 mol/L sulfuric acid for 6 h at 55 °C. Halloysite before and after treatment was characterized by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Thereafter, the dodecylamine was loaded into treated halloysite by the vacuum pulse technique. The release kinetics of the inhibitor from within halloysite nanotubes were studied through the EIS technique where it was found that the action of halloysite is pH-dependent, with a higher release kinetics at pH 2. The nanocontainers were loaded in a solvent based alkyd primer and a water based acrylic primer for the evaluation of the corrosion resistance of the systems through electrochemical impedance spectroscopy (EIS), scanning vibration electrode technique (SVET) and accelerated corrosion tests in a salt spray chamber (SSC). The adhesion of the two systems was evaluated through the pull-off adhesion test. For the two systems evaluated, it was possible to verify the self-healing effect, but this effect was not long, probably due to the low loading efficiency of dodecylamine in halloysite nanotubes. The cost analysis of halloysite loaded with dodecylamine showed that the loading process needs an optimization in order to make this project feasible in the coating industry.
2

Mechanically Driven Reconstruction of Materials at Sliding Interfaces to Control Wear

Shirani, Asghar 05 1900 (has links)
To minimize global carbon emissions, having efficient jet engines and internal combustion engines necessitates utilizing lightweight alloys such as Al, Ti, and Mg-based alloys. Because of their remarkable strength/weight ratio, these alloys have received a lot of attention. Nonetheless, they have very poor tribological behavior, particularly at elevated temperatures beyond 200 °C, when most liquid lubricants begin to fail in lubrication. Over the last two decades, there has been a lot of interest in protecting Al, and Ti-based alloys by developing multiphase solid lubricants with a hard sublayer that provide mechanical strength and maintain the part's integrity while providing lubricity. The development of novel coatings with superior lubricity, high toughness, and high-temperature tolerance remains a challenging and hot topic to research and provide new engineered solutions for. To address and provide solutions to protect light-weight, i.e., Al, and Ti alloys at high-temperature and bestow superior tribological properties to such alloys, three types of adaptive lubricious coatings have been studied in this thesis: Nb-Ag-O self-healing lubricious ternary oxide, PEO-chameleon a self-adaptive multi-phase coating, and Sb2O3-MSH-C lubricious adaptive coatings to address this challenge. The development of the Nb-Ag-O ternary resulted in a coefficient of friction as low as 0.2 at 600 °C and crack healing at 900 °C. PEO-chameleon coatings demonstrated a remarkably low COF, as low as 0.07 at 300 °C and 1.4 GPa applied pressure. Finally, the Sb2O3-MSH-C multi-phase lubricious solid lubricant revealed superlubricity, with a CoF of 0.008 at 300 °C, providing a potentially promising contender for high-temperature, high-load applications.

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