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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

Influência dos pré-tratamentos de bombardeamento com íons de Xe+ e nitretação iônica no desgaste de revestimento de TiN / The influence of pre-treatment of the bombardment with Xe+ ions and ion nitriding in the wear of TiN coatings

Vales, Sandra dos Santos 29 March 2016 (has links)
A tendência mundial de se buscar a sustentabilidade econômica tem causado uma crescente demanda por novas técnicas e novos materiais que gerem: aumento da produtividade, maior velocidade de operação, aumento da vida útil de ferramentas e matrizes, e que reduzam o custo ambiental atual. Nesta busca a modificação de superfícies metálicas é um campo promissor e o bombardeamento com íons de Xe+ tem sido utilizada para texturizar a superfície do substrato, seja para o aumento da aderência de revestimentos com grande dureza ou para melhorar a difusão de N. Neste estudo são relatados os resultados obtidos de ensaios de dureza, desgaste, DRX (fases e tensão residual) e microscopias MEV, AFM e MET, efetuadas em amostras de aço 100Cr6 (globulizada) modificadas superficialmente por meio de bombardeamento com íons de Xe+ e revestimento duplex. Para esse fim, foram preparadas amostras combinando: bombardeamento com íons de Xe+ com energia de 400 e 1000 eV; implantação de N por feixe de íons e plasma pulsado; e deposição do revestimento de TiN por sputtering com diferentes temperaturas em um sistema reativo com N2-IBSD. Uma análise desses resultados permitiu constatar que o bombardeamento de íons de Xe+ gera refinamento de grãos, texturização, e aumenta a densidade de defeitos na estrutura cristalina na superfície tratada em função da energia utilizada. O bombardeamento de Xe+ com energia de 1000 eV melhorou o aprisionamento de nitrogênio e a difusão a 380°C (via feixe de íons) o que levou a formação dos nitretos γ\'-Fe4N e ε-Fe2-3N. Enquanto que com energia de 400 eV levou a formação apenas do nitreto γ\'-Fe4N. As propriedades adquiridas na combinação dos pré-tratamentos de bombardeamento de Xe+ com energia de 400 eV, nitretação a plasma pulsado (520°C) e a deposição do filme de TiN (500°C/240 min) levaram ao melhor desempenho no ensaio de desgaste. / The global trend of seeking economic sustainability has caused a growing demand for new materials that generate: increased productivity, higher operating speed, increased service life of tools and dies, and to reduce the current environmental cost. In this search, the modification of metallic surfaces is a promising field and bombardment Xe+ ions has been used to texture the surface of the substrate, is to increase the tack coatings with high hardness or to improve the N diffusion. In this study are reported the results obtained from testing the hardness, wear, XRD (phase and residual stress) and microscopy SEM, AFM and TEM, made in 100Cr6 steel samples (globulized) surface modified by bombardment with Xe+ and duplex coating. To this end, samples were prepared by combining: bombardment Xe+ ions with energy of 400 and 1000 eV; N implantation by ion beam and pulsed plasma; and deposition of the TiN coating by sputtering at different temperatures in a N2 reaction system-IBSD. An analysis of these results helped to confirm that the bombardment of Xe+ ions produces grain refinement, texturing, and increases the defect density in the crystalline structure of the surface treated according to the energy used. Bombardment of Xe+ ions with energy 1000 eV improved nitrogen trapping and diffusion to 380°C (via ion beam) which led to the formation of γ\'-Fe4N and ε-Fe2-3N nitrides. Whereas with energy 400 eV led to the formation of only γ\'-nitride Fe4N. The properties acquired in the combination of the pre-treatments of Xe+ ions bombardment at 400 eV, pulsed plasma nitriding (520°C) and the deposition of TiN coating (500°C/240 min) leads to a superior performance in wear test.
2

Influência dos pré-tratamentos de bombardeamento com íons de Xe+ e nitretação iônica no desgaste de revestimento de TiN / The influence of pre-treatment of the bombardment with Xe+ ions and ion nitriding in the wear of TiN coatings

Sandra dos Santos Vales 29 March 2016 (has links)
A tendência mundial de se buscar a sustentabilidade econômica tem causado uma crescente demanda por novas técnicas e novos materiais que gerem: aumento da produtividade, maior velocidade de operação, aumento da vida útil de ferramentas e matrizes, e que reduzam o custo ambiental atual. Nesta busca a modificação de superfícies metálicas é um campo promissor e o bombardeamento com íons de Xe+ tem sido utilizada para texturizar a superfície do substrato, seja para o aumento da aderência de revestimentos com grande dureza ou para melhorar a difusão de N. Neste estudo são relatados os resultados obtidos de ensaios de dureza, desgaste, DRX (fases e tensão residual) e microscopias MEV, AFM e MET, efetuadas em amostras de aço 100Cr6 (globulizada) modificadas superficialmente por meio de bombardeamento com íons de Xe+ e revestimento duplex. Para esse fim, foram preparadas amostras combinando: bombardeamento com íons de Xe+ com energia de 400 e 1000 eV; implantação de N por feixe de íons e plasma pulsado; e deposição do revestimento de TiN por sputtering com diferentes temperaturas em um sistema reativo com N2-IBSD. Uma análise desses resultados permitiu constatar que o bombardeamento de íons de Xe+ gera refinamento de grãos, texturização, e aumenta a densidade de defeitos na estrutura cristalina na superfície tratada em função da energia utilizada. O bombardeamento de Xe+ com energia de 1000 eV melhorou o aprisionamento de nitrogênio e a difusão a 380°C (via feixe de íons) o que levou a formação dos nitretos γ\'-Fe4N e ε-Fe2-3N. Enquanto que com energia de 400 eV levou a formação apenas do nitreto γ\'-Fe4N. As propriedades adquiridas na combinação dos pré-tratamentos de bombardeamento de Xe+ com energia de 400 eV, nitretação a plasma pulsado (520°C) e a deposição do filme de TiN (500°C/240 min) levaram ao melhor desempenho no ensaio de desgaste. / The global trend of seeking economic sustainability has caused a growing demand for new materials that generate: increased productivity, higher operating speed, increased service life of tools and dies, and to reduce the current environmental cost. In this search, the modification of metallic surfaces is a promising field and bombardment Xe+ ions has been used to texture the surface of the substrate, is to increase the tack coatings with high hardness or to improve the N diffusion. In this study are reported the results obtained from testing the hardness, wear, XRD (phase and residual stress) and microscopy SEM, AFM and TEM, made in 100Cr6 steel samples (globulized) surface modified by bombardment with Xe+ and duplex coating. To this end, samples were prepared by combining: bombardment Xe+ ions with energy of 400 and 1000 eV; N implantation by ion beam and pulsed plasma; and deposition of the TiN coating by sputtering at different temperatures in a N2 reaction system-IBSD. An analysis of these results helped to confirm that the bombardment of Xe+ ions produces grain refinement, texturing, and increases the defect density in the crystalline structure of the surface treated according to the energy used. Bombardment of Xe+ ions with energy 1000 eV improved nitrogen trapping and diffusion to 380°C (via ion beam) which led to the formation of γ\'-Fe4N and ε-Fe2-3N nitrides. Whereas with energy 400 eV led to the formation of only γ\'-nitride Fe4N. The properties acquired in the combination of the pre-treatments of Xe+ ions bombardment at 400 eV, pulsed plasma nitriding (520°C) and the deposition of TiN coating (500°C/240 min) leads to a superior performance in wear test.
3

Interface-Based Software Development / Interface-Based Software Development

Rais, Aziz January 2017 (has links)
Even though there are many software development and project management methodologies available, research and practice both show that IT software development projects still fail, and that the quality of software products does not always meet customers' expectations. There might be multiple causes for such failures, but some of these reasons can be seen to influence or create others. Therefore, the larger the project is, the higher its risk of failure, especially if the teams involved work remotely (distributed and outsourced). This increase in project complexity is considered the motivation for this paper. Similarly, there are other factors that can result in a project's failure and customers' dissatisfaction regarding software quality. All such factors identified by research conducted by organizations specializing in this area are analyzed in order to identify a common root of IT project failures. Once the root causes of these failures have been identified and analyzed, the goal of the Interface based software development methodology is to solve them. The solution offered by an Interface based software development methodology is to improve understanding of software requirements and to describe these requirements with interfaces in an object-oriented way. Interface based software development will support and drive development towards service-oriented architecture (SOA) and component-based development (CBD). The goal of interface based software development is to increase software testability and maintainability and to make it more easily feasible to execute various software development processes in parallel.
4

Investigations On The Influence Of Process Parameters On The Deposition Of Samarium Cobalt (SmCo) Permanent Magnetic Thin Films For Microsystems Applications

Balu, R 12 1900 (has links)
The research in permanent magnet thin films focuses on the search of new materials and methods to increase the prevalent data storage limit. In the recent past the work towards the application of these films to micro systems have also gained momentum. Materials like samarium cobalt with better magnetic properties and temperature stability are considered to be suitable in this regard. The essential requirement in miniaturization of these films is to deposit them on silicon substrates that can alleviate the micro fabrication process. In this work, an effort has been made to deposit SmCo films with better magnetic properties on silicon substrates. In the deposition of SmCo, the composition of the deposited films and the structural evolution are found to play an important role in determining the magnetic properties. Proper control over these parameters is essential in controlling the magnetic properties of the deposited films. SmCo being a two component material the composition of the films is dependent on the nature of the source and the transport of the material species from source to substrate. On the other hand, structural evolution is dependent on the energetical considerations between the SmCo lattice and substrate lattice. This most often is dominated by the lattice match between the condensing lattice and the substrate lattice. As such Si does not provide good lattice match to SmCo lattice. Hence suitable underlayers are essential in the deposition of these films. Materials like W, Cu, Mo and Cr were used as underlayers. Out of all these Cr is found to provide good lattice match and adhesion to SmCo lattice. Sputtering being the common deposition tool, SmCo could be sputtered either from the elemental targets of Sm and Co or from the compound target of SmCo5. Sputtering of elemental targets of Sm and Co provides the flexibility of varying the composition whereas sputtering from the SmCo alloy target provides to flexibility of controlling the structural evolution by different process parameters. In this work two different techniques namely Facing Target Sputtering (FTS) and Ion Beam Sputter Deposition (IBSD) were followed in depositing SmCo films. In FTS technique, SmCo films were directly deposited on silicon substrates by simultaneous sputtering of samarium and cobalt targets facing each other. This sputtering geometry enabled to achieve films with a wide composition range of 55 – 95 at. % of cobalt in single deposition. The resulting composition variation and material property variation were investigated in terms of process parameters like pressure, temperature, SubstrateTarget Distance (STD) and InterTarget Distance (ITD). The composition distribution of the films was found to be dependent on the thermalisation distances and the mean free path available during the transport. To explain the process and the composition variation, a simulation model based on Monte Carlo method has been employed. The simulated composition variation trends were in good agreement with that of the experimental observations. IBSD, known for its controlled deposition, was employed to deposit both Cr (as an underlayer) and SmCo films. Cr with close epitaxial match with SmCo induces structural evolution in deposited films. The initial growth conditions were found to play a dominant role in the structural evolution of these Cr films. Hence, initial growth conditions were modified by means of oblique incidence and preferential orientation of (200) plane was obtained. With three different angles of incidence, three different surface orientations of Cr films were achieved. These films were then used as structural templates in the deposition of SmCo films. The influence of parameters like composition, impurities, film thickness, beam energy, ion flux, annealing, angles of incidence and underlayer properties on the structural and magnetic properties of SmCo was studied. The structural evolution of SmCo has been found to depend on the structural orientation of Cr underlayers. This followed the structural relation of SmCo(100)||Cr(110)||Si(100) and SmCo(110)||Cr(100)||Si(100). A mixed surface plane orientation was observed in the case of mixed orientation Cr template. The magnetic coercivities were found to increase from 50 Oe to 5000 Oe with the change in the structure of the deposited films.

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