Untersuchung der Eigenschaften einer Argon-Glimmentladung mit Titankathode mittels Langmuir-Sonde und laserinduzierter Fluoreszenz

In this work an abnormal Argon glow discharge with Titanium cathode has been investigated. The results presented are the measurements and calculations concerning the electron beam plasma in the negative glow. Two diagnostics have been employed to determine the plasma parameters. A Langmuir probe has been used in the negative glow to measure the spatial distributions of the electron density, temperature and the plasma potential. Two electron groups were found, slow electrons with a temperature of 0.3 eV and density of $\sim$ 10$^{11}$ cm$^{-3}$, and fast electrons with $\sim$ 3.0 eV and $\sim$ 10$^{7}$ cm$^{-3}$. Under all operational conditions the plasma potential was almost constant within the negative glow and about 1.5 V positive with respect to the anode voltage. The electric field has been calculated from the potential profile. It is shown that, within the error of measurement, this electric field is equal to the ambipolar electric field, which has been calculated from the electron density and temperature p rofiles. The density distribution of titanium atoms, ions and $^{3}$P$_{2}$ metastable argon atoms has been measured by means of the laser induced fluorescence. The densities were absolutly calibrated using a carbon arc as a radiation standard. The spatial resolution was 1.5 mm in the axial direction and 3 mm in the radial direction. In the range of operation a titanium density (Ti I) of about 3.0 x 10$^{10}$ cm$^{-3}$ has been found. From the population distribution of the titanium atoms in the ground state levels the temperature profile in the discharge axis has been determined. In the negative glow a nearly constant temperature of about 350 K has been found. Towards the cathode a temperature rise up to 410 K at 0.5 kV (0.2 mb) and up to 540 K at 2.1 kV (0.1 mb) has been observed. A numerical calculation of the electron density distribution has been carried out. By solving the diffusion equation a lot of information concerning the beam electrons has been obtained. The position of the density maxima has been seen to depend on the amount of the low energy beamelectrons. From the shape of the radial density profiles it turned out that the divergency of the beam electrons increased with the length of the cathode fall. With the experimental density profiles several collisional rates have been evaluated and used in a numerical calculation of the axial profiles of the titanium atoms and $^{3}$P$_{2}$ metastable argon atoms. A good agreement with the experimental profiles has been achieved in both cases

Propriedades macroscópicas de um plasma magnetizado

Orientador: Paulo Hiroshi SakamakaDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb WataghinResumo: Este trabalho experimental foi dedicado ao estudo das propriedades macroscópicas de um plasma não homogêneo c anisotrópico. Com este objetivo foi construída uma máquina linear de espelho magnético na qual o plasma era produzido na forma de uma coluna cilíndrica por rádio freqüência (RF). As medidas das propriedades macroscópicas do plasma foram levantadas basicamente com o uso das sondas de Langmuir, Hall e magnética. Os resultados experimentais obtidos são discutidos, analisados e comparados com os que foram fornecidos pelo modelo teórico proposto para representar o tensor de permissividade dielétrica do plasma. Estes resultados Indicam que o plasma magnetizado possui propriedades não lineares e anisotrópicas, propriedades estas que se apresentam de forma não homogênea ao longo da coluna de plasmaAbstract: Not informedMestradoFísicaMestre em Físic

Changing in Fatigue Life of 300 M Bainitic Steel After Laser Carburizing and Plasma Nitriding

In this work 300M steel samples is used. This high-strength steel is used in aeronautic and aerospace industry and other structural applications. Initially the 300 M steel sample was submitted to a heat treatment to obtain a bainític structure. It was heated at 850 °C for 30 minutes and after that, cooled at 300 °C for 60 minutes. Afterwards two types of surface treatments have been employed: (a) using low-power laser CO2 (125 W) for introducing carbon into the surface and (b) plasma nitriding at a temperature of 500° C for 3 hours. After surface treatment, the metallographic preparation was carried out and the observations with optical and electronic microscopy have been made. The analysis of the coating showed an increase in the hardness of layer formed on the surface, mainly, among the nitriding layers. The mechanical properties were analyzed using tensile and fatigue tests. The results showed that the mechanical properties in tensile tests were strongly affected by the bainitic microstructure. The steel that received the nitriding surface by plasma treatment showed better fatigue behavior. The results are very promising because the layer formed on steel surface, in addition to improving the fatigue life, still improves protection against corrosion and wear

Changing in Fatigue Life of 300 M Bainitic Steel After Laser Carburizing and Plasma Nitriding

In this work 300M steel samples is used. This high-strength steel is used in aeronautic and aerospace industry and other structural applications. Initially the 300 M steel sample was submitted to a heat treatment to obtain a bainític structure. It was heated at 850 °C for 30 minutes and after that, cooled at 300 °C for 60 minutes. Afterwards two types of surface treatments have been employed: (a) using low-power laser CO2 (125 W) for introducing carbon into the surface and (b) plasma nitriding at a temperature of 500° C for 3 hours. After surface treatment, the metallographic preparation was carried out and the observations with optical and electronic microscopy have been made. The analysis of the coating showed an increase in the hardness of layer formed on the surface, mainly, among the nitriding layers. The mechanical properties were analyzed using tensile and fatigue tests. The results showed that the mechanical properties in tensile tests were strongly affected by the bainitic microstructure. The steel that received the nitriding surface by plasma treatment showed better fatigue behavior. The results are very promising because the layer formed on steel surface, in addition to improving the fatigue life, still improves protection against corrosion and wear