Made available in DSpace on 2014-12-17T14:06:57Z (GMT). No. of bitstreams: 1 RomuloRMS.pdf: 3055902 bytes, checksum: 75eaf485a85529179129dd468ccfc772 (MD5) Previous issue date: 2007-12-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The ionic plasma nitriding is one of the most important plasma assisted treatment technique for surface modification, but it presents some inherent problems mainly in nitriding pieces with complex geometries. In the last four years has appeared a plasma nitriding technique, named ASPN (Active Screen Plasma Nitriding) in which the samples and the workload are surrounded by a metal screen on which the cathodic potential is applied. This new technique makes possible to obtain a perfect uniform nitrided layer apart from the shape of the samples. The present work is based on the development of a new nitriding plasma technique named CCPN (Cathodic Cage Plasma Nitriding) Patent PI 0603213-3 derived from ASPN, but utilizes the hollow cathode effect to increase the nitriding process efficiency. That technique has shown great improvement on the treatment of several types of steels under different process conditions, producing thicker and harder layers when compared with both, ASPN and ionic plasma nitriding, besides eliminating problems associated with the later technique. The best obtained results are due to the hollow cathode effect on the cage holes. Moreover, characteristic problems of ionic plasma nitriding are eliminated due to the fact that the luminescent discharge acts on the cage wall instead of on the samples surface, which remains under a floating potential. In this work the enhancement of the cathodic cage nitriding layers proprieties, under several conditions for some types of steels was investigated, besides the mechanism for nitrides deposition on glass substrate, concluding that the CCPN is both a diffusion and a deposition process at the same time / A nitreta??o i?nica ? um dos processos de revestimento superficial dos mais importantes, mas apresenta alguns problemas inerentes, principalmente, na nitreta??o de pe?as com geometria complexa. Nos ?ltimos quatro anos surgiu uma nova t?cnica de nitreta??o a plasma, denominada de ASPN (Active Screen Plasma Nitriding), na qual as amostras s?o envolvidas por uma tela polarizada catodicamente e com ela ? poss?vel obter uma camada nitretada, perfeitamente uniforme, independente da forma da amostra. O nosso trabalho baseia-se no desenvolvimento, no ?mbito do LabPlasma, de uma nova t?cnica de nitreta??o em plasma, denominada nitreta??o em gaiola cat?dica (NGC) dep?sito de patente PI 0603213-3 derivada da ASPN, mas que utiliza o efeito de c?todo oco para aumentar a efici?ncia do processo de nitreta??o. Esta t?cnica apresentou bastante efic?cia na nitreta??o de v?rios tipos de a?os, nas mais variadas condi??es de tratamento, proporcionando a obten??o de camadas mais espessas e de maior dureza, quando comparada com a ASPN e com a nitreta??o i?nica convencional, al?m de eliminar problemas de irregularidades associados ? t?cnica convencional. Sua maior efici?ncia deve-se ? utiliza??o do efeito de c?todo oco estabelecido nas paredes dos furos da gaiola, enquanto que a elimina??o dos problemas inerentes ? t?cnica convencional, deve-se ao fato do plasma atuar na gaiola e n?o nas amostras, as quais permanecem em potencial flutuante. Neste trabalho, foram avaliadas as condi??es de otimiza??o da nitreta??o, realizada com esta t?cnica, para diferentes tipos de a?os, al?m de investigarmos os mecanismos que atuam, quando da deposi??o de nitretos em substratos de vidro, observando que a NGC ? um processo misto de difus?o e deposi??o

Made available in DSpace on 2014-12-17T14:07:01Z (GMT). No. of bitstreams: 1 NataliaFD_DISSERT.pdf: 4136751 bytes, checksum: 47b384d6442f251d58542735c23ae300 (MD5) Previous issue date: 2012-02-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Titanium nitride films were grown on glass using the Cathodic Cage Plasma Deposition technique in order to verify the influence of process parameters in optical and structural properties of the films. The plasma atmosphere used was a mixture of Ar, N2 and H2, setting the Ar and N2 gas flows at 4 and 3 sccm, respectively and H2 gas flow varied from 0, 1 to 2 sccm. The deposition process was monitored by Optical Emission Spectroscopy (OES) to investigate the influence of the active species in plasma. It was observed that increasing the H2 gas flow into the plasma the luminescent intensities associated to the species changed. In this case, the luminescence of N2 (391,4nm) species was not proportional to the increasing of the H2 gas into the reactor. Other parameters investigated were diameter and number of holes in the cage. The analysis by Grazing Incidence X-Ray Diffraction (GIXRD) confirmed that the obtained films are composed by TiN and they may have variations in the nitrogen amount into the crystal and in the crystallite size. The optical microscopy images provided information about the homogeneity of the films. The atomic force microscopy (AFM) results revealed some microstructural characteristics and surface roughness. The thickness was measured by ellipsometry. The optical properties such as transmittance and reflectance (they were measured by spectrophotometry) are very sensitive to changes in the crystal lattice of the material, chemical composition and film thicknesses. Therefore, such properties are appropriate tools for verification of this process control. In general, films obtained at 0 sccm of H2 gas flow present a higher transmittance. It can be attributed to the smaller crystalline size due to a higher amount of nitrogen in the TiN lattice. The films obtained at 1 and 2 sccm of H2 gas flow have a golden appearance and XRD pattern showed peaks characteristics of TiN with higher intensity and smaller FWHM (Full Width at Half Maximum) parameter. It suggests that the hydrogen presence in the plasma makes the films more stoichiometric and becomes it more crystalline. It was observed that with higher number of holes in the lid of the cage, close to the region between the lid and the sample and the smaller diameter of the hole, the deposited film is thicker, which is justified by the most probability of plasma species reach effectively the sample and it promotes the growth of the film / Filmes finos de nitreto de tit?nio foram crescidos sobre vidro utilizando a t?cnica de deposi??o por descarga em gaiola cat?dica a fim de averiguar a influ?ncia das vari?veis de processo nas propriedades ?pticas e estruturais do filme. Como atmosfera do plasma foi utilizada a mistura de gases Ar, N2 e H2, fixando o fluxo de Ar e N2 em 4 e 3 sccm, respectivamente, e usando fluxos de 0, 1 e 2 sccm de H2. O processo de deposi??o foi monitorado por Espectroscopia de Emiss?o ?ptica (OES) para investiga??o das esp?cies ativas no plasma. Observou-se que com o aumento fluxo de H2 as intensidades das esp?cies luminescentes no plasma sofrem altera??es e que a esp?cie N2 (391,4 nm) n?o teve um crescimento proporcional ao fluxo de H2. Outros par?metros investigados foram o di?metro e o n?mero de furos da gaiola. As an?lises de difra??o de raios X com ?ngulo de incid?ncia rasante (GIXRD) comprovaram que os filmes obtidos s?o compostos por TiN, podendo ter varia??es quanto a quantidade de nitrog?nio na rede e o tamanho de cristalito; a microscopia ?ptica forneceu dados sobre a homogeneidade, a partir da microscopia de for?a at?mica (AFM) observou-se algumas caracter?sticas microestruturais do filme e a rugosidade. A espessura foi quantificada atrav?s das an?lises de elipsometria. As propriedades ?pticas como reflet?ncia e transmit?ncia (medidas por espectrofotometria) s?o bastante sens?veis a altera??es na rede cristalina do material, composi??o qu?mica e espessura, sendo, portanto, uma boa ferramenta para verifica??o do controle do processo. De maneira geral, os filmes obtidos com fluxo de 0 sccm de H2 possuem uma maior transmit?ncia atribu?da ao menor cristalinidade decorrente da maior quantidade de nitrog?nio na rede cristalina do TiN. Os filmes obtidos nos fluxos de 1 e 2 sccm de H2 obtiveram um aspecto dourado e o difratograma apresentou picos caracter?sticos do TiN com maior intensidade e menor largura a meia altura, sugerindo que com a presen?a de hidrog?nio na atmosfera do plasma os filmes s?o mais estequiom?tricos e com maior cristalinidade. Quanto ? configura??o da gaiola observou-se que com maior quantidade de furos na tampa, maior a proximidade da tampa com a amostra e menor o di?metro do furo, maior ? a espessura do filme, o que ? justificado pela maior probabilidade das esp?cies do plasma atingirem efetivamente o substrato e promoverem o crescimento do filme

Made available in DSpace on 2014-12-17T14:07:06Z (GMT). No. of bitstreams: 1 PolianaRFS_DISSERT.pdf: 3998823 bytes, checksum: e0480a4a5d6b04450e748434898535a9 (MD5) Previous issue date: 2013-03-01 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The technique of plasma nitriding by the cathode cage mainly stands out for its ability to produce uniform layers, even on parts with complex geometries. In this study, it was investigated the efficiency of this technique for obtaining duplex surface, when used, simultaneously, to nitriding treatment and thin film deposition at temperatures below 500?C. For this, were used samples of AISI 41 0 Martensitic Stainless Steel and performed plasma treatment, combining nitriding and deposition of thin films of Ti and/or TiN in a plasma atmosphere containing N2-H2. It was used a cathodic cage of titanium pure grade II, cylindrical with 70 mm diameter and 34 mm height. Samples were treated at temperature 420?C for 2 and 12 hours in different working pressures. Optical Microscopy (OM), Scanning Electron Microscopy (SEM) with micro-analysis by Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), Atomic Force Microscopy (AFM) and analysis of Vickers Microhardness were used to investigate coating properties such as homogeneity and surface topography, chemical composition, layer thickness, crystalline phase, roughness and surface microhardness. The results showed there is a direct proportionality between the presence of H2 in plasma atmosphere and the quantity of titanium in surface chemical composition. It was also observed that the plasma treatment at lowpressure is more effective in formation of TiN thin film / A t?cnica de nitreta??o a plasma por gaiola cat?dica vem se destacando, principalmente, pela sua capacidade de produzir camadas uniformes mesmo em pe?as com geometria complexa. Neste trabalho, investigou-se a efici?ncia desta t?cnica para obten??o de superf?cie duplex, quando utilizada, simultaneamente, para tratamento de nitreta??o e deposi??o de filmes finos em temperaturas inferiores a 500?C. Para tal, foram utilizadas amostras do a?o inoxid?vel martens?tico AISI 410 e realizados tratamentos a plasma, combinando a nitreta??o e deposi??o de filmes finos de Ti e/ou TiN, em uma atmosfera contendo N2-H2. Foi utilizada uma gaiola cat?dica de tit?nio puro grau II em forma cil?ndrica, com 70 mm de di?metro e 34 mm de altura. As amostras foram tratadas numa temperatura de 420?C, com dura??o de 2 e 12 horas e em diferentes press?es de trabalho. Microscopia ?ptica (MO), Microscopia Eletr?nica de Varredura (MEV) com microan?lise por Espectroscopia de Energia Dispersiva (EDS), Difra??o de Raios-X (DRX), Microscopia de For?a At?mica (MFA) e ensaio de Microdureza Vickers foram empregados para investigar as propriedades do revestimento, tais como homogeneidade e topografia superficial, composi??o qu?mica, espessura da camada, fases cristalinas, rugosidade e microdureza superficial. Os resultados mostraram existir uma proporcionalidade direta entre a presen?a de H2 na atmosfera do plasma e a quantidade do elemento qu?mico tit?nio na composi??o qu?mica superficial. Observou-se, tamb?m, que o tratamento a plasma em baixa press?o ? mais eficaz na forma??o do filme fino de nitreto de tit?nio

Made available in DSpace on 2014-12-17T14:58:23Z (GMT). No. of bitstreams: 1 LinoAF_DISSERT.pdf: 8452397 bytes, checksum: f4854ebf6942546ff7bf8e8e0a4689c4 (MD5) Previous issue date: 2013-08-09 / The technique of ion nitriding, despite being fully consolidated in the industry, has great limitations when applied to the treatment of small parts. This is because effects that occur due to non-uniformity of the electric field, generate localized heating in parts, damaging the uniformity of nitrided layer. In addition, because the samples are treated static parts thereof are untreated. To expand the use of plasma nitriding, this work presents the development, assembly and testing of a prototype plasma reactor with rotatory cathodic cage [patent pending], able to meet these needs, giving the material a uniform treatment and opening doors to industrial scale production. The samples tested with hexagonal nuts are 6.0 mm in diameter, made of stainless steel AISI 304 nitrided at a pressure of 1 mbar in an atmosphere of 20% H2 + 80% N2 for 1 h. After treatment, testing visual inspection, optical microscopy and microhardness were carried out to check the effectiveness of the process for uniformity and hardness of the parts. All samples exhibited uniform color, and matte brownish, unlike the untreated samples, silver color and gloss. The hardness of the surface (top and sides) was 65% and even higher than the original hardness. The nitrided layer showed great uniformity in microstructure and thickness. It is concluded, therefore, that the unit was effective constructed for the purposes for which it was designed / A t?cnica de nitreta??o i?nica, apesar de estar plenamente consolidada na ind?stria, possui grande limita??o quando aplicada ao tratamento de pe?as pequenas. Isso acontece porque efeitos que ocorrem devido a n?o uniformidade do campo el?trico, geram aquecimentos localizados nas pe?as, prejudicando a uniformidade da camada nitretada. Al?m disso, pelo fato das amostras serem tratadas de maneira est?tica, partes das mesmas ficam sem tratamento. Para ampliar o uso da nitreta??o a plasma, este trabalho apresenta o desenvolvimento, montagem e teste de um prot?tipo de reator de plasma com gaiola cat?dica rotat?ria [patente requerida], capaz de atender a essas necessidades, conferindo ao material um tratamento uniforme e abrindo portas ? produ??o em escala industrial. As amostras submetidas ao teste s?o porcas sextavadas de 6,0 mm de di?metro, fabricadas em a?o inoxid?vel AISI 304, nitretadas numa press?o de 1 mbar em atmosfera de 20%H2 + 80%N2, durante 1 h. Ap?s o tratamento, ensaios de inspe??es visuais, microscopia ?tica e microdureza foram realizadas a fim de conferir a efic?cia do processo quanto ? uniformidade e dureza das pe?as. Todas as amostras apresentaram cor uniforme, amarronzada e fosca, ao contr?rio das amostras sem tratamento, de cor prata e brilhosas. A dureza da superf?cie (topo e lateral) mostrou-se uniforme e 65% superior ? dureza original, considerado o tempo de tratamento. A camada nitretada apresentou grande uniformidade na microestrutura e espessura. Conclui-se, portanto, que o equipamento constru?do mostrou efic?cia para os fins a que foi designado