Made available in DSpace on 2014-12-17T14:58:21Z (GMT). No. of bitstreams: 1 EdsonJCS_DISSERT.pdf: 1649413 bytes, checksum: 32339cc7487693336b6710eaa3e1c93c (MD5) Previous issue date: 2013-07-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Many applications require that the plasma discharge is produced apart from the surface to be processed, thus preventing damage caused by bombardment and/or plasma radiation. In the post-discharge regime in various applications thermally sensitive materials can be used. In this work, active species produced by discharge and post-discharge hollow cathode were diagnosed by optical emission spectroscopy and mass spectrometry. The discharge was produced with the gases Ar and Ar - N2 gas flow ranging from 1 to 6 cm3/min and electric current between 150 to 600 mA. It was estimated that the ion density inside the hollow cathode, with 2 mm diameter ranged between 7.71 and 14.1 x 1015 cm-3. It was observed that the gas flow and the electric current changes the emission intensity of Ar and N2 species. The major ionic species detected by quadrupole mass spectrometry were Ar+ and N2+. The ratio of optical emission intensities of N2(1 +)/Ar(811 nm) was related to the partial pressure of N2 after the hollow cathode discharge at low pressure / Muitas aplica??es de plasma exigem que a descarga seja produzida distante da superf?cie a ser processada, evitando assim danos causados pelo bombardeamento e/ou radia??o do plasma. Nesse regime de p?s-descarga v?rias aplica??es em materiais termicamente sens?veis podem ser utilizadas. Neste trabalho esp?cies ativas produzidas por descarga e p?s-descarga de catodo oco foram diagnosticadas por espectroscopia de emiss?o ?ptica e espectrometria de massa. A descarga foi produzida com os gases Ar e mistura Ar - N2 com fluxo de g?s variando de 1 a 6 cm3/min e corrente el?trica entre 150 a 600 mA. Estimou-se que a densidade de ?ons no interior do c?todo oco, com 2 mm de di?metro, variou entre 7,71 e 14,1 x 1015 cm-3. Observou-se que o fluxo de g?s e a corrente el?trica alteram a intensidade de emiss?o das esp?cies de Ar e N2. As principais esp?cies i?nicas detectadas por espectrometria de massa quadrupolar foram de Ar+ e N2+. A raz?o das intensidades de emiss?o ?tica de N2 (1 +)/Ar(811 nm) foi relacionada com a press?o parcial de N2 na p?s-descarga de c?todo oco em baixa press?o

Made available in DSpace on 2014-12-17T15:15:02Z (GMT). No. of bitstreams: 1 FranciscoOA.pdf: 1713095 bytes, checksum: 1ee138883bf7b4da570838f6654b21b0 (MD5) Previous issue date: 2006-12-15 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / In the present work we use a plasma jet system with a hollow cathode to deposit thin TiO2 films on silicon substrates as alternative at sol-gel, PECVD, dip-coating e magnetron sputtering techniques. The cylindrical cathode, made from pure titanium, can be negatively polarized between 0 e 1200 V and supports an electrical current of up to 1 A. An Ar/O2 mixture, with a total flux of 20 sccm and an O2 percentage ranging between 0 and 30%, is passed through a cylindrical hole machined in the cathode. The plasma parameters and your influence on the properties of deposited TiO2 films and their deposition rate was studied. When discharge occurs, titanium atoms are sputtered/evaporated. They are transported by the jet and deposited on the Si substrates located on the substrate holder facing the plasma jet system at a distance ranging between10 and 50 mm from the cathode. The working pressure was 10-3 mbar and the deposition time was 10 -60 min. Deposited films were characterized by scanning electron microscopy and atomic force microscopy to check the film uniformity and morphology and by X-ray diffraction to analyze qualitatively the phases present. Also it is presented the new dispositive denominate ionizing cage, derived from the active screen plasma nitriding (ASPN), but based in hollow cathode effect, recently developed. In this process, the sample was involved in a cage, in which the cathodic potential was applied. The samples were placed on an insulator substrate holder, remaining in a floating potential, and then it was treated in reactive plasma in hollow cathode regime. Moreover, the edge effect was completely eliminated, since the plasma was formed on the cage and not directly onto the samples and uniformity layer was getting in all sampl / Filmes finos de TiO2 foram depositados sobre substrato de sil?cio usando descarga em c?todo oco. A presente t?cnica foi usada como alternativa a outras t?cnicas como solgel, PECVD, dip-coating e magnetron sputtering. O sistema desenvolvido apresenta uma configura??o de c?todo oco cil?ndrico polarizado com tens?o DC variando entre 0 e 1200V e corrente de at? 1 A. Um jato de plasma de Ar + O2, extrai ?tomos do mesmo, que s?o em seguida depositados sobre um substrato frontalmente posicionado. As amostras s?o posicionadas a dist?ncias do c?todo variando entre 10 e 50 mm. Foram investigadas os par?metros do plasma e sua influ?ncia sobre as propriedades dos filmes depositados. Os par?metros de trabalho para deposi??o de TiO2 foram 20sccm de fluxo da mistura Ar/O2 com percentuais de oxig?nio variando entre 0 -30%, press?o de trabalho 10-3 mbar e tempos de deposi??o de 10 -60 minutos. As amostras foram caracterizadas por microscopia eletr?nica de varredura e microscopia de for?a at?mica para verificar sua uniformidade e morfologia e por difra??o de raios-x para an?lise qualitativa das fases presentes nos filmes. Neste trabalho tamb?m ? apresentado um novo dispositivo, denominado gaiola ionizante, derivada da nitreta??o a plasma em tela ativa (ASPN), mas baseado no efeito de c?todo oco, recentemente desenvolvido. Neste processo as amostras s?o envolvidas por uma gaiola, na qual ? aplicada a diferen?a de potencial, permanecendo em potencial flutuante, sendo tratadas numa regi?o livre da influ?ncia do campo el?trico por um plasma reativo, operando em regime de c?todo oco. Dessa forma foram obtidas camadas uniformes em todas as amostras e eliminados defeitos como o efeito de borda

This study explores the possibility of miniaturizing magnetoplasmadynamic thrusters (MPDTs) to significantly lower power and discharge current levels compared to most conventional MPDTs. A design alternative for MPDTs using a discharge channel with a rectangular cross-section is presented that enables the implementation of strong external magnetic fields to increase the applied-field Lorentz force. The thruster concept uses heaterless calcium aluminate electride (C12A7:e-) hollow cathodes as the electron source. A prototype of the concept intended for the low-amp current range generates thrust in the low millinewton range with a specific impulse ranging between 400 s and 1200 s at power levels below 500 W but shows high thermal power losses to the anode. A further miniaturized version of the concept intended for the sub-amp current range is thermally more sustainable but requires high mass flow rates to achieve a stable discharge, limiting the achievable specific impulse.

Graphene has been shown to be very powerful as a transducer in many biosensor applications due to its high sensitivity. This enables smaller surfaces and therefore less material consumption when producing sensors and concequently cheaper and more portable sensors compared to the commercially available sensors today. The electrical properties of graphene are very sensitive to gas exposure why presence of molecules or small changes in concentration could easily be detected when using graphene as a sensing layer. Graphene is sensitive towards many molecules and in order to detect and possibly identify gas molecules the surface needs to be functionalized. The intention of this project was to use nanoparticles (NPs) to further increase sensitivity and specificity towards selected molecules and also enable biofunctionalization of the NPs, and by that tune the electrical properties of the graphene. This study proposes the use of Fe3O4 and TiO2 NPs to enable sensitive detection of volatile gases and possibly further functionalization of the NPs using biomolecules as a detecting agent in a liquid-phasebiosensor application. The interaction between graphene and NPs have been investigated using several surface charactarization methods and electrical measurements for detection of gaseous molecules and also molecules in a liquid solution. The characterizing methods used are XPS, AFM with surface-potential mapping and Raman spectroscopy with reflectance mapping in order to investigate the NPs interaction with the graphene surface. Sensors where manufactured for gas-phase detection of CO, formaldehyde, benzene and NH3 specifically and display differences in sensitivity and behavior of the Fe3O4 and TiO2 NPs respectively. For liquid measurements the difference in behavior in two buffers was investigated using an in-house flow-cell setup. The surface charecterizing measurements indicated that just a small difference could be found between the two NPs, however a significant change in sensor response could be detected as a function of coverage. The liquid and gas-phase measurements rendered information on differences in sensitivity between the NPs and between analytes where TiO2 showed a higher level of sensitivity towards most of the gases investigated. Both Fe3O4 and TiO2 NP coated graphene showed capability to detect formaldehyde and benzene down to 50 ppb and 5 ppb respectively. The sensitive gas detection could help protecting individuals being exposed to a hazardous level of volatile gases if concentrations increase rapidly or at a long term exposure with lower concentrations, improving saftey and health where these gases are present.

Made available in DSpace on 2014-12-17T14:06:59Z (GMT). No. of bitstreams: 1 EdalmyOA.pdf: 3019202 bytes, checksum: 652b61310237ca737b3decb6945b78be (MD5) Previous issue date: 2008-06-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The system built to characterize electrodes and, consequently, deposited fine films are constituted by a hollow cathode that works to discharges and low pressures (approximately 10-3 to 5 mbar), a source DC (0 to 1200 V), a cylindrical camera of closed borossilicato for flanges of stainless steel with an association of vacuum bombs mechanical and spread. In the upper flange it is connected the system of hollow cathode, which possesses an entrance of gas and two entrances for its refrigeration, the same is electrically isolated of the rest of the equipment and it is polarized negatively. In front of the system of hollow cathode there is a movable sample in stainless steel with possibility of moving in the horizontal and vertical. In the vertical, the sample can vary its distance between 0 and 70 mm and, in the horizontal, can leave completely from the front of the hollow cathode. The sample and also the cathode hollow are equipped with cromel-alumel termopares with simultaneous reading of the temperatures during the time of treatment. In this work copper electrodes, bronze, titanium, iron, stainless steel, powder of titanium, powder of titanium and sil?cio, glass and ceramic were used. The electrodes were investigated relating their geometry change and behavior of the plasma of the cavity of hollow cathode and channel of the gas. As the cavity of hollow cathode, the analyzed aspects were the diameter and depth. With the channel of the gas, we verified the diameter. In the two situations, we investigated parameters as flow of the gas, pressure, current and applied tension in the electrode, temperature, loss of mass of the electrode with relationship at the time of use. The flow of gas investigated in the electrodes it was fastened in a work strip from 15 to 6 sccm, the constant pressure of work was among 2.7 to 8 x 10-2 mbar. The applied current was among a strip of work from 0,8 to 0,4 A, and their respective tensions were in a strip from 400 to 220 V. Fixing the value of the current, it was possible to lift the curve of the behavior of the tension with the time of use. That curves esteem in that time of use of the electrode to its efficiency is maximum. The temperatures of the electrodes were in the dependence of that curves showing a maximum temperature when the tension was maximum, yet the measured temperatures in the samples showed to be sensitive the variation of the temperature in the electrodes. An accompaniment of the loss of mass of the electrode relating to its time of use showed that the electrodes that appeared the spherical cavities lost more mass in comparison with the electrodes in that didn't appear. That phenomenon is only seen for pressures of 10-2 mbar, in these conditions a plasma column is formed inside of the channel of the gas and in certain points it is concentrated in form of spheres. Those spherical cavities develop inside of the channel of the gas spreading during the whole extension of the channel of the gas. The used electrodes were cut after they could not be more used, however among those electrodes, films that were deposited in alternate times and the electrodes that were used to deposit films in same times, those films were deposited in the glass substrata, alumina, stainless steel 420, stainless steel 316, sil?cio and steel M2. As the eletros used to deposit films in alternate time as the ones that they were used to deposit in same times, the behavior of the thickness of the film obeyed the curve of the tension with relationship the time of use of the electrode, that is, when the tension was maximum, the thickness of the film was also maximum and when the tension was minimum, the thickness was minimum and in the case where the value of the tension was constant, the thickness of the film tends to be constant. The fine films that were produced they had applications with nano stick, bio-compatibility, cellular growth, inhibition of bacterias, cut tool, metallic leagues, brasagem, pineapple fiber and ornamental. In those films it was investigated the thickness, the adherence and the uniformity characterized by sweeping electronic microscopy. Another technique developed to assist the production and characterization of the films produced in that work was the caloteste. It uses a sphere and abrasive to mark the sample with a cap impression, with that cap form it is possible to calculate the thickness of the film. Through the time of life of the cathode, it was possible to evaluate the rate of waste of its material for the different work conditions. Values of waste rate up to 3,2 x 10-6 g/s were verified. For a distance of the substratum of 11 mm, the deposited film was limited to a circular area of 22 mm diameter mm for high pressures and a circular area of 75 mm for pressure strip. The obtained films presented thickness around 2,1 ?m, showing that the discharge of arch of hollow cathode in argon obeys a curve characteristic of the tension with the time of life of the eletrodo. The deposition rate obtained in this system it is of approximately 0,18 ?m/min / O sistema constru?do para caracterizar eletrodos e, conseq?entemente, filmes finos depositados ? constitu?do por um c?todo oco que trabalha a altas e baixas press?es (aproximadamente 10-3 a 5 mbar), uma fonte DC (0 a 1200 V), uma c?mara cil?ndrica de borossilicato fechada por flanges de a?o inox com uma associa??o de bombas de v?cuo mec?nica e difusora. No flange superior est? conectado o sistema de c?todo oco, o qual possui uma entrada de g?s e duas entradas para a sua refrigera??o, o mesmo est? eletricamente isolado do resto do equipamento e ? polarizado negativamente. Em frente ao sistema de c?todo oco encontra-se um porta amostra em a?o inox m?vel com possibilidade de se mover na horizontal e vertical. Na vertical, o porta amostra pode variar a sua dist?ncia entre 0 e 70 mm e, na horizontal, pode sair completamente da frente do c?todo oco. Tanto o porta amostra como o c?todo oco s?o equipados com termopares de cromel-alumel com leitura simult?nea das temperaturas durante o tempo de tratamento. Neste trabalho foram utilizados eletrodos de cobre, bronze, tit?nio, ferro, a?o inox, p? de tit?nio, p? de tit?nio e sil?cio, vidro e cer?mica. Os eletrodos foram investigados com rela??o a sua mudan?a de geometria e comportamento do plasma dentro da cavidade de c?todo oco e canal do g?s. Quanto a cavidade de c?todo oco, os aspectos analisados foram o di?metro e sua profundidade. Com o canal do g?s, verificamos o di?metro. Nas duas situa??es, investigamos par?metros como fluxo do g?s, press?o, corrente e tens?o aplicada no eletrodo, temperatura, perda de massa do eletrodo com rela??o ao tempo de uso. O fluxo de g?s investigado nos eletrodos foi fixado em uma faixa de trabalho de 15 a 6 sccm, a press?o constante de trabalho ficou entre 2.7 a 8 x 10-2 mbar. A corrente aplicada foi entre uma faixa de trabalho de 0,8 a 0,4 A, e as suas respectivas tens?es ficaram em uma faixa de 400 a 220 V. Fixando o valor da corrente, foi poss?vel levantar a curva do comportamento da tens?o com o tempo de uso. Essa curva estima em que tempo de uso do eletrodo a sua efici?ncia ? m?xima. As temperaturas dos eletrodos ficaram na depend?ncia dessa curva mostrando uma temperatura m?xima quando a tens?o era m?xima, j? as temperaturas medidas nas amostras mostraram ser sens?veis a varia??o da temperatura no eletrodo. Um acompanhamento da perda de massa do eletrodo com rela??o ao seu tempo de uso mostrou que os eletrodos que apareceram as cavidades esf?ricas perderam mais massa em compara??o aos eletrodos em que essas n?o apareceram. Esse fen?meno s? ? visto para press?es de 10-2 mbar, nestas condi??es uma coluna de plasma se forma dentro do canal do g?s e em determinados pontos fica concentrado em forma de esferas. Essas cavidades esf?ricas evoluem dentro do canal do g?s se propagando durante toda a extens?o do canal do g?s. Os eletros utilizados foram cortados depois que n?o puderam ser mais usados, no entanto entre esses eletrodos filmes que foram depositados em tempos alternados e os eletrodos que foram utilizados para depositar filmes em tempos iguais, esses filmes foram depositados nos substratos de vidro, alumina, a?o inox 420, a?o inox 316, sil?cio e a?o M2. Tanto os eletros usados para depositar filmes em tempo alternado como os que foram usados para depositar em tempos iguais, o comportamento da espessura do filme obedeceu a curva da tens?o com rela??o ao tempo de uso do eletrodo, isto ?, quando a tens?o era m?xima, a espessura do filme tamb?m foi m?xima e quando a tens?o era m?nima, a espessura foi m?nima e no caso onde o valor da tens?o foi constante, a espessura do filme tende a ficar constante. Os filmes finos que foram produzidos tiveram aplica??es com nano bast?o, bio-compatibilidade, crescimento celular, inibi??o de bact?rias, ferramenta de corte, ligas met?licas, brasagem, fibra de abacaxi e decorativos. Nesses filmes foi investigada a espessura, a ader?ncia e a uniformidade caracterizadas por microscopia eletr?nica de varredura. Outra t?cnica desenvolvida para atender a produ??o e caracteriza??o dos filmes produzidos nesse trabalho foi o caloteste. Ele se utiliza de uma esfera e abrasivo para marcar a amostra com uma impress?o de calota, com essa forma de calota ? poss?vel calcular a espessura do filme. Atrav?s do tempo de vida do c?todo, foi poss?vel avaliar a taxa de desgaste do seu material para as diferentes condi??es de trabalho. Valores de taxa de desgaste at? 3,2 x 10-6 g/s foram verificados. Para uma dist?ncia do substrato de 11 mm, o filme depositado ficou limitado a uma ?rea circular de 22 mm de di?metro para press?es altas e uma ?rea circular de 75 mm para faixa de press?o. Os filmes obtidos apresentaram espessura em torno de 2,1 ?m, mostrando que a descarga de arco de c?todo oco em arg?nio obedece a uma curva caracter?stica da tens?o com o tempo de vida do eletrodo. A taxa de deposi??o obtida neste sistema ? de aproximadamente 0,18 ?m/min

Made available in DSpace on 2014-12-17T14:57:58Z (GMT). No. of bitstreams: 1 KarilanyDC_TESE.pdf: 5082673 bytes, checksum: 4427463c2d2c4ca61196bdca31ba604e (MD5) Previous issue date: 2014-06-10 / In recent years there has been a significant growth in technologies that modify implant surfaces, reducing healing time and allowing their successful use in areas with low bone density. One of the most widely used techniques is plasma nitration, applied with excellent results in titanium and its alloys, with greater frequency in the manufacture of hip, ankle and shoulder implants. However, its use in dental implants is very limited due to high process temperatures (between 700 C o and 800 C o ), resulting in distortions in these geometrically complex and highly precise components. The aim of the present study is to assess osseointegration and mechanical strength of grade II nitrided titanium samples, through configuration of hollow cathode discharge. Moreover, new formulations are proposed to determine the optimum structural topology of the dental implant under study, in order to perfect its shape, make it efficient, competitive and with high definition. In the nitriding process, the samples were treated at a temperature of 450 C o and pressure of 150 Pa , during 1 hour of treatment. This condition was selected because it obtains the best wettability results in previous studies, where different pressure, temperature and time conditions were systematized. The samples were characterized by X-ray diffraction, scanning electron microscope, roughness, microhardness and wettability. Biomechanical fatigue tests were then conducted. Finally, a formulation using the three dimensional structural topology optimization method was proposed, in conjunction with an hadaptive refinement process. The results showed that plasma nitriding, using the hollow cathode discharge technique, caused changes in the surface texture of test specimens, increases surface roughness, wettability and microhardness when compared to the untreated sample. In the biomechanical fatigue test, the treated implant showed no flaws, after five million cycles, at a maximum fatigue load of 84.46 N. The results of the topological optimization process showed well-defined optimized layouts of the dental implant, with a clear distribution of material and a defined edge / Nos ?ltimos anos tem-se observado um grande crescimento em tecnologias para modifica??o de superf?cies de implantes que reduzam o tempo de espera da cicatriza??o, assim como possibilite seu uso com sucesso em ?reas de baixa densidade ?ssea. Dentre as diferentes t?cnicas, a nitreta??o por plasma desponta como forte candidata, uma vez que a mesma j? est? sendo empregada com excelentes resultados no tit?nio e suas ligas, aplicados com maior frequ?ncia na confec??o de implantes de quadril, ombro e tornozelo. Entretanto, seu uso em implantes dent?rios ? bastante limitado devido ?s altas temperaturas do processo (entre 700 C o e 800 C o ) resultando em distor??es nessas pe?as que possuem geometria complexa e alto grau de precis?o. O objetivo deste trabalho ? avaliar a osseointegra??o e resist?ncia mec?nica de amostras de tit?nio grau II nitretadas, atrav?s da configura??o de descarga em c?todo oco. Al?m disto, propor formula??es para determina??o da topologia ?tima estrutural do implante dent?rio em estudo, com o intuito de aperfei?oar sua forma, que seja eficiente, competitiva e com alta defini??o. No processo de nitreta??o, as amostras foram tratadas em temperatura a de 450 oC e press?o de 150 Pa , durante 1 hora de tratamento. Esta condi??o foi escolhida por apresentar os melhores resultados de molhabilidade em trabalhos anteriores, onde sistematizou-se diferentes condi??es de press?o, temperatura e tempo. As amostras tratadas foram caracterizadas por Difra??o de Raios-X, Microscopia Eletr?nica de Varredura, Rugosidade, Microdureza e Molhabilidade. Posteriormente, foram realizados ensaios biomec?nicos de fadiga. Finalizando com uma proposta de formula??o atrav?s do m?todo de otimiza??o topol?gica tridimensional, combinado a um processo de refino h-adaptativo. Os resultados mostraram que a nitreta??o a plasma, utilizando a t?cnica de descarga em c?todo oco, produziu mudan?as na textura superficial dos corpos de prova, aumento da rugosidade superficial, da molhabilidade e da microdureza quando comparado a amostra sem tratamento. No ensaio biomec?nico de fadiga, o implante tratado n?o apresentou sinal de falha, ap?s cinco milh?es de ciclos, a uma carga m?xima de fadiga de 84, 46 N . Os resultados do processo de otimiza??o topol?gica apresentaram leiautes otimizados bem definidos do implante dent?rio, com uma n?tida distribui??o de material e defini??o do contorno.

Die vorliegende Dissertation behandelt Charakterisierung, Modellbildung sowie Anwendung einer magnetfeldgestützten Hohlkathoden-Bogenentladung. Hohlkathoden sind seit den 1960er Jahren Gegenstand grundlagen- sowie anwendungsorientierter Forschung und werden seit 20 Jahren am Fraunhofer-Institut für Elektronenstrahl- und Plasmatechnik für die Anwendung auf dem Gebiet der Vakuumbeschichtung weiterentwickelt. Ziel dieser Arbeit ist es, die technologischen Fortschritte physikalisch zu verstehen und gezielte Weiterentwicklungen für spezifische Einsatzgebiete zu ermöglichen. In der untersuchten Hohlkathodenbauform ist das aus Tantal bestehende, vom Arbeitsgas Argon durchströmte Kathodenröhrchen koaxial von einer Ringanode sowie von einer Magnetfeldspule umgeben. Die Entladung wird durch Hochspannungspulse gezündet, worauf sich ein diffuser Bogen im Röhrchen (internes Plasma) ausbildet. Das Röhrchen wird von Plasmaionen auf hohe Temperaturen geheizt, die eine thermionische Emission von Elektronen ermöglichen, welche das Plasma speisen. Das technologisch nutzbare externe Plasma wird im Vakuumrezipienten durch Wechselwirkung der Gasteilchen mit Strahlelektronen aus der Kathode erzeugt. Bei starker Reduktion des Arbeitsgasflusses wird die Entladung durch das Magnetfeld der Spule stabilisiert. Der experimentelle Befund, dass dadurch Plasmadichte und -reichweite sowie ggf. die Ladungsträgerenergien im Rezipienten aufgrund des intensiveren Elektronenstrahls wesentlich gesteigert werden können, wird durch ortsaufgelöste Langmuir-Sondenmessung, optische Emissionsspektroskopie und energieaufgelöste Massenspektrometrie ausführlich belegt und nach der Lösung von Strom- und Wärmebilanzgleichungen durch die Verhältnisse im Kathodenröhrchen begründet. Neben Argon werden auch typische Reaktivgase der Vakuumbeschichtung im Hohlkathodenplasma betrachtet: zum einen Stickstoff und Sauerstoff, die in reaktiven PVD-Prozessen (physikalische Dampfphasenabscheidung) zur Beschichtung mit Oxid- bzw. Nitridschichten zum Einsatz kommen und durch Ionisation, Dissoziation und Anregung im Hohlkathodenplasma verbesserte Schichteigenschaften ermöglichen; zum anderen Azetylen, das bei PECVD (plasmagestützte chemische Dampfphasenabscheidung) von amorphen wasserstoffhaltigen Kohlenstoffschichten z. B. für tribologische oder biokompatible Beschichtungen genutzt wird. Azetylen wird durch Streuprozesse mit Elektronen und Ionen im Plasma aufgespalten, wodurch schichtbildende Spezies erzeugt werden, die am Substrat kondensieren. Durch die Wahl der Plasmaparameter sowie durch abgestimmte Substratbiasspannung und Substratkühlung lassen sich die Beschichtungsrate einstellen sowie polymer-, graphit- oder diamantartige Eigenschaften erzielen. Neben der Plasmadiagnostik mittels energieaufgelöster Massenspektrometrie werden die erzeugten Kohlenstoffschichten vorgestellt und hinsichtlich Härte, Zusammensetzung und Morphologie analysiert. / In the present thesis, characterization, modeling and application of a magnetically enhanced hollow cathode arc discharge are presented. Since the 1960s, hollow cathodes are being studied in basic and applied research. At Fraunhofer Institute for Electron Beam and Plasma Technology, further development concerning the application in vacuum coating technology has been carried out for about twenty years. The present work targets on physically understanding the technological progress in order to enable specific further development and application. In the investigated hollow cathode device, a ring-shaped anode and a magnetic field coil are arranged coaxially around the tantalum cathode tube, which is flown through by argon as the working gas. The discharge is ignited by high voltage pulses establishing a diffuse arc within the cathode tube (internal plasma). The cathode is being heated by the plasma ions to high temperatures, which leads to thermionic emission of electrons sustaining the plasma. The external plasma in the vacuum chamber, which can be used for technological applications, is generated by collisions of gas atoms with beam electrons originating from the cathode. In the case of strongly reduced working gas flow, the discharge is stabilized by the magnetic field of the coil; the related experimental findings such as significantly increased plasma density and range as well as higher charge carrier energies in the external plasma are extensively proved by spatially resolved Langmuir probe measurements, optical emission spectroscopy, and energy-resolved ion mass spectrometry. Furthermore, the results are correlated to the conditions within the cathode tube by solving the current and heat balance equations. Besides argon, typical reactive gases used in vacuum coating are examined in the hollow cathode plasma, too. First, nitrogen and oxygen, which are applied in PVD (physical vapor deposition) processes for the deposition of oxide and nitride layers, are ionized, dissociated, and excited by plasma processes. In the case of practical application, this plasma activation leads to improved film properties. Second, acetylene is used as a precursor for PECVD (plasma-enhanced chemical vapor deposition) of amorphous hydrogenated carbon films, e.g. for tribological or biocompatible applications. Acetylene is cracked by electron and ion scattering in the plasma providing film-forming species to be deposited on the substrate. The deposition rate as well as the polymeric, graphitic, or diamond-like properties can be controlled by plasma parameters, a defined substrate bias, and substrate cooling. The hollow cathode-generated acetylene plasma has been characterized by energy-resolved ion mass spectrometry, and the carbon films obtained are analyzed regarding hardness, film composition, and morphology.

Testing of hardware to be used in space sometimes involves using vacuum chambers. The need to test hollow cathodes, used as neutralizers for some Electric Propulsion Thrusters, and low power Hall Effect Thrusters at OHB Sweden requires a vacuum chamber to be upgraded. The thesis aims firstly to show the process of adapting the vacuum chamber at OHB to test a heaterless hollow cathode. The requirements of the test included a maximum temperature of a 100 °C in the cathode’s bracket and a pressure inside the chamber around 10¯6 mbar during the test. To accomplish the first, the mounting structure was subjected to a thermal simulation using CREO. Once, the requirement was fulfilled the structure was manufactured and mounted. For the second requirement, a vacuum chamber characterization was done to see the pressure evolution inside the facility. Lastly, the fluid line was designed and mounted in the facility. An upgrade of the current vacuum chamber was deemed insufficient to test low power Hall Effect Thrusters. A comparison between the current vacuum chamber at OHB Sweden and other vacuum chambers designed for this purpose was made. The conclusion was drawn that a new vacuum chamber is necessary. Proposals for the design of a new vacuum facility are presented with particular focus on dimensions, the pump system, sputter protection and thermal protection. / Testandet av hårdvara som ska användas i rymden involverar ibland vakuumkammare. Behovet av att testa hollow cathodes, som används som neutraliserare för vissa jonmotorer, och Hall Effect Thrusters med låg effekt hos OHB Sweden kräver att en vakuumkammare uppgraderas. Avhandlingen syftar först till att redogöra för hur en av vakuumkammarna hos OHB Sweden kan anpassas för att testa en heaterless hollow cathode. Kraven för testet inkluderar en maximal temperatur på 100 °C grader i katodens fäste och och ett vakuum runt 10 ¯6 mbar. En jig designades genom bland annat termisk simulering i CREO. När det termiska kravet ansågs uppfyllas tillverkades och installerades denna jig. För det andra kravet karakteriserades vakuumkammaren med dess vakuumpumpar i syfte att bedöma om dessa kunde uppfylla kravet. Slutligen designades och installerades ett rörsystem som möjliggör matning av bränsle till testobjekten. En uppgradering av nuvarande vakuumkammare bedömdes otillräcklig för att testa Hall Effect Thrusters med låg effekt. En jämförelse mellan nuvarande vakuumkammare på OHB Sweden och andra vakuumkammare designade för detta ändamål gjordes och slutsatsen drogs att en ny vakuumkammare är nödvändig. Förslag på design av ny vakuumkammare presenteras med särkilt fokus på dimensioner, pumpssystemet, sputtingskydd och termiskt skydd.

The present thesis is the result of a research period at the Institute of Space and Astronautical Science of the Japanese Aerospace Exploration Agency, ISAS/JAXA within Funaki Laboratory of the Department of Space Flight Systems that followed the path of plume plasma diagnostics for space electric propulsion drives. During the experimental studies two high-current hollow cathodes and an innovative prototype of a low-voltage fully external discharge plasma thruster (XPT) had their plasma plumes diagnosed using electrostatic probes and retarding potential analyser (RPA). A Hall thruster and hollow cathode plume is defined as an unmagnetised quasi-neutral plasma which is mainly formed of neutral particles, electrons, singly and doubly charged ions. Plasma diagnostic techniques provide information through practical observations in order to fully understand the dynamics of the aforementioned plume components, the physical processes taking place within the plume and their effects on the spacecraft, for instance. Mastering these aspects of the plasma plume of space electric propulsion drives bolster the design processes, leading to highly efficient devices. Firstly, the introduction provides insights on the fundamental principles of hollow cathodes and Hall thrusters and a brief presentation of the plasma diagnostic techniques used during the research: single and double Langmuir probes, emissive probes and retarding potential analyser. Then, the fundamental plume diagnostics principles are depicted in an exhaustive way, departing from classical plasma kinetic theory, energy distribution functions and ending with an overview on the theory of charge collection by cylindrical probes. Subsequently, peculiarities of various analysis techniques are exposed for the Langmuir probes, emissive probes and RPA, with an emphasis on their strengths and demerits. The experimental setups for the cathodes and XPT plume diagnostic procedures are then outlined. The experimental logic, setup and electrical diagrams as well as a presentation of each probe design and manufacturing details are extensively discussed. The hollow cathodes experimental results are exposed with a discourse that aims of overviewing the difference between the various data analysis methods applied for the raw data. A discussion ensued based on the results in order to effectively identify mechanisms that produced the observed plasma parameters distributions. For the first time, the plume of a fully external discharge plasma thruster was diagnosed utilising double Langmuir probes.  The thesis highlights the main results obtained for the XPT far-field plume plasma diagnostics. The experimental findings for both thruster centreline positions and 2D plume maps for several axial distances away from the anode plate offer a ground basis for future measurements, a comparison term and a database to support ongoing computational codes. The results are discussed and related to the thruster performances data obtained during previous experiments. The thesis includes consistency analyses between the experimental data and the numerical simulation results and the uncertainties in measured plasma parameters associated with each data analysis procedure are evaluated for each data set. Last, the conclusions underline the main aspects of the research and further work on the previously mentioned plasma diagnostic techniques for hollow cathodes and XPT is suggested. / La présente thèse est le résultat d'une période de recherche à l'Institut des Sciences Spatiales et Astronautiques de l'Agence Spatiale Japonaise, ISAS / JAXA qui a suivi la voie des diagnostics du plasma de la plume de propulseurs électriques spatiaux. Au cours des études expérimentales, deux cathodes creuses à fort courant et un prototype innovant d'un propulseur basse tension à décharge externe de plasma (XPT) avaient leurs faisceaux de plasma diagnostiqués en utilisant des sondes électrostatiques et un analyseur à potentiel retardé. La plume d’un propulseur à effet Hall et d’une cathode creuse est définie comme un plasma quasi-neutre non-magnétisé qui est principalement formé de particules neutres, d’électrons, d’ions monovalents et bivalents. Les techniques de diagnostic du plasma fournissent des informations, via des observations pratiques, afin de bien comprendre la dynamique des composants de la plume mentionnés ci-dessus, les processus physiques qui se déroulent dans la plume et leurs effets sur une sonde spatiale, par exemple. La maîtrise de ces aspects du plasma de la plume généré par les propulseurs électriques spatiaux renforce les processus de conception de ce type de propulsion, ce qui conduit à des dispositifs hautement efficaces. Tout d'abord, l'introduction donne un aperçu sur les principes fondamentaux de cathodes creuses et de propulseurs à effet Hall, et une brève présentation des techniques de diagnostic du plasma utilisées lors de la recherche : sondes de Langmuir simples et doubles, des sondes émissives et d’analyseur à potentiel retardé. Ensuite, les principes fondamentaux de diagnostic de la plume sont représentés de manière exhaustive, d’abord la théorie cinétique classique du plasma, les fonctions de distribution en énergie et pour terminer une vue d'ensemble de la théorie de la collecte de charge par des sondes cylindriques. Par la suite, les particularités des diverses techniques d'analyse sont exposées pour les sondes de Langmuir, les sondes émissives et RPA, en mettant l'accent sur leurs avantages et leurs inconvénients. Les montages expérimentaux pour les procédures de diagnostic de la plume-plasma de cathodes et du XPT sont ensuite décrits. La logique expérimentale, les schémas électriques ainsi qu'une présentation de la conception et de la fabrication de chaque sonde sont largement discutés. Les résultats expérimentaux pour les cathodes creuses sont exposés de façon à présenter la différence entre plusieurs méthodes d'analyse de données appliquées aux données brutes. Une discussion s’ensuit, basée sur les résultats afin d'identifier efficacement les mécanismes qui ont produits les propriétés électroniques observées. Pour la première fois, la plume d'un propulseur à décharge externe de plasma a été diagnostiquée en utilisant des sondes de Langmuir doubles. La thèse met en évidence les principaux résultats obtenus pour le diagnostic en champ lointain de la plume-plasma du XPT. Les résultats expérimentaux pour les positions sur l'axe du propulseur et le cartes 2D de la plume pour plusieurs distances axiales loin de l’anode offrent une base pour de futures mesures, un terme de comparaison et une base de données pour appuyer les codes numériques. Les résultats sont discutés et sont rapportés aux données de performances du propulseur obtenus lors des essais précédents. La thèse comprend des analyses de la cohérence entre les données expérimentales et les résultats de simulation numérique, et les incertitudes des paramètres mesurés du plasma associées à chaque procédure d'analyse des données sont évaluées pour chaque ensemble de données. Enfin, les conclusions soulignent les principaux aspects de la recherche et une poursuite des travaux sur les techniques de diagnostic de plasma pour les cathodes creuses et le XPT est suggérée.

L'objectif de cette thèse est de fournir une meilleure compréhension des différents phénomènes physiques liés aux microplasmas/microdécharges. Pour cela, des matrices de microréacteurs sur silicium ont été étudiées. De nombreuses configurations ont été construites de manière à analyser l’influence de chaque paramètre physique sur le fonctionnement de ces dispositifs. Le présent travail porte sur l'élaboration et la caractérisation de dispositifs micro-décharge à base de silicium. Dans ce travail de thèse, les régimes de courant continu (DC) et de courant alternatif (AC) sont étudiés en utilisant des configurations de décharges différentes. Pour la fabrication de ces réacteurs, nous sommes partis de wafers de Silicium que nous avons structurés et traités en salle blanche. La technologie de fabrication utilisée est compatible avec les méthodes de fabrication de dispositifs CMOS. Les microréacteurs sont constitués d’électrodes de nickel et de silicium séparés par une couche diélectrique de SiO2 de 6 μm d’épaisseur. L’épaisseur du diélectrique est ici beaucoup plus faible que celle des microréacteurs étudiés jusqu’à présent. Les dispositifs sont constitués de cavités de 25 à 150 microns de diamètre. Les essais de microdécharge ont été effectués dans des gaz inertes à une pression comprise entre 100 et 1000 Torrs. Nous avons d’abord étudié les phénomènes d’allumage et d’extinction à partir de microdispositifs monocavité en alumine. Puis, nous avons étudié le fonctionnement en DC/AC de microréacteurs en silicium comportant un nombre de cavité compris entre 1 et1024. Les caractéristiques des microdécharges ont été étudiées grâce à des mesures électriques, des mesures de spectroscopie d'émission optique (OES), de spectroscopie d’absorption à diode laser (DLAS) et de spectroscopie d'émission optique résolue en temps (PROES). Ces différents diagnostics nous ont permis de mettre en évidence les phénomènes d’allumage, d’extinction, d’instabilité et les mécanismes de défaillance de nos microdispositifs. Ce travail de thèse a permis de tester les performances et les limites technologiques des matrices de microdécharges sur silicium. Une attention particulière a été portée sur leur durée de vie. / The objective of this thesis is to provide a better understanding of various physical phenomena related to microplasmas/microdischarges. For this purpose, arrays of microreactors on silicon were studied. Different array configurations were fabricated to analyse the influence of each parameter on the physical operation of these devices. The present work focuses on the development and characterisation of micro-discharge devices based on silicon. In this thesis, direct current (DC) and alternating current (AC) regimes are studied using different discharge configurations. For the fabrication of these reactors, Silicon wafers are structured and processed in a cleanroom. Fabrication technology used is compatible with the CMOS technology. The microreactors are fabricated with nickel and silicon electrodes, separated by a dielectric layer of SiO2 with a thickness of 6 μm. The thickness of the dielectric is much lower here than the microreactors studied so far. The devices consist of cavities with 25 to 150 μm in diameter. Experiments of the microdischarges are performed in inert gases at a pressure between 100 and 1000 Torr. We first studied the phenomena of ignition and extinction for the microdevices based on alumina. Then, we studied the microreactors based on silicon containing 1 to 1024 cavities under DC and AC regimes. Characteristics of microdischarges were studied by electrical measurements, measurements of optical emission spectroscopy (OES), laser diode absorption spectroscopy (DLAS) and phase resolved optical emission spectroscopy (PROES). These diagnostics allowed us to investigate the phenomena of ignition, extinction, instability and failure mechanisms of the microplasma devices. This thesis work allowed testing the performance and technological limitations of the silicon based microdischarge arrays. Particular attention was paid to their life time.