Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2015-12-02T22:57:03Z No. of bitstreams: 1 HugoFernandesMedeirosDaSilva_DISSERT.pdf: 30197183 bytes, checksum: aff97f351eb1c274b3b803536423bba1 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2015-12-09T20:00:17Z (GMT) No. of bitstreams: 1 HugoFernandesMedeirosDaSilva_DISSERT.pdf: 30197183 bytes, checksum: aff97f351eb1c274b3b803536423bba1 (MD5) / Made available in DSpace on 2015-12-09T20:00:18Z (GMT). No. of bitstreams: 1 HugoFernandesMedeirosDaSilva_DISSERT.pdf: 30197183 bytes, checksum: aff97f351eb1c274b3b803536423bba1 (MD5) Previous issue date: 2014-06-20 / Estruturas porosas est?o sendo amplamente investigadas para uso em implantes biom?dicos, com objetivo de integrar o implante de forma mec?nica e funcional no interior do tecido ?sseo. Al?m disso, esta estrutura tamb?m ? importante para que f?rmacos possam se armazenados podendo induzir e acelerar o processo de osseointegra??o. Com o intuito de investigar esse efeito, p?s met?licos de Ti, 35Nb e 4Sn foram sinterizados por plasma usando descarga por c?todo oco. As sinteriza??es foram realizadas em plasma de arg?nio, press?o fixada em 4 mbar e temperaturas de 500?C, 600?C e 700?C. Tamb?m foram sinterizadas amostras em forno ? resit?ncia el?trica ? 1200?C, afim de comparar a sinteriza??o a plasma com um met?do convencional. Verificou-se que amostras sinterizadas por plasma na configura??o de c?todo oco apresentaram gradiente de porosidade, enquanto as amostras sinterizadas em forno resistivo n?o apresentaram. Al?m disso, encontrou-se diferen?as na micro-estrutura onde obteve-se uma superfic?e mais porosa e o n?cleo mais denso, em diferentes temperaturas. Assim como per?l de percola??o de ?gua destilada, e a compara??o da composi??o qu?mica das camadas porosas das amostras tratadas por plasma foram os pricipais resultados obtidos. Diante dos resultados obtidos, pode-se concluir que essa estrutura ? particularmente importante para aplica??o na ?rea biom?dica tais como arcabou?os para libera??o de f?rmacos e implantes. . / Porous structures are being widely investigated for use in biomedical implants, aiming to mechanically integrate and functionally the implant inside the bone tissue. Moreover, this structure is also important for drugs that can be stored and can induce and accelerate the process of osseointegration. With the purpose to investigate this effect, Ti, Nb and Sn metal powders, were sintered by plasma using a hollow cathode discharge. Sintering was performed in argon plasma set at 4 mbar pressure and temperatures of 500 ? C, 600 ? C and 700 ? C. Samples were also sintered in the electrical resistance furnace at 1200 ? C in order to compare plasma sintering with the conventional method. It was observed that plasma samples sintered with the hollow cathode configuration showed a gradient in porosity, while the samples sintered in the resistive furnace did not. Furthermore, differences in the microstructure of the samples were found, were a surface with higher porosity and ales porous core were obtained at different temperatures. The percolation profile of distilled water and the chemical compositions of the porous layers of the plasma treated samples were the main results obtained. Based on these results, we can conclude that this structure is particularly important for application in the biomedical field such as scaffolds for drug delivery and implants

Made available in DSpace on 2014-12-17T14:07:20Z (GMT). No. of bitstreams: 1 MariaRPF_TESE.pdf: 4797522 bytes, checksum: 8d9626466b01e2425f6ea6036398adcf (MD5) Previous issue date: 2014-01-24 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Carbide reinforced metallic alloys potentially improve some important mechanical properties required for the overall use of important engineering materials such as steel and nickel. Nevertheless, improved performance is achieved not only by composition enhancement but also by adequate processing techniques, such as novel sintering methods in the case of powder metallurgy. The method minimizes energy losses in addition to providing uniform heating during sintering. Thus, the general objective of this study was to evaluate the density, hardness, flexural strength, dilatometric behavior and to analyze the microstructure of metal matrix composites based nickel with addition of carbides of tantalum and / or niobium when sintered in a conventional furnace and Plasma assisted debinding and sintering (PADS). Initially, were defineds best parameters of granulation, screening and mixing procedure. After, mixtures of carbonyl Ni and 5%, 10% and 15 wt.% NbC and TaC were prepared in a Y-type mixer under wet conditions during 60 minutes. The mixtures were then dried and granulated using 1.5 wt. % paraffin diluted in hexane. Granulates were cold pressed under 600 MPa. Paraffin was then removed from the pressed pellets during a pre-sintering process carried out in a tubular furnace at 500 ?C during 30 min. The heating rate was 3 ?C/min. The pellets were then sintered using either a plasma assisted reactor or a conventional resistive tubular furnace. For both methods, the heating rate was set to 8 ?C/min up to 1150 ?C. The holding time was 60 minutes. The microstructure of the sintered samples was evaluated by SEM. Brinell hardness tests were also carried out. The results revealed that higher density and higher hardness values were observed in the plasma-assisted sintered samples. Hardness increased with the concentration of carbides in the Ni-matrix. The flexural strength also increased by adding the carbides. The decline was larger for the sample with addition of 5% 5% TaC and NbC. In general, compositions containing added carbide 10% showed less porous and more uniform distribution of carbides in the nickel matrix microstructural appearance. Thus, both added carbide and plasma sintering improved density, hardness, flexural strength and microstructural appearance of the composites / Ligas met?licas refor?adas por carbetos melhoram potencialmente algumas propriedades mec?nicas necess?rias para a utiliza??o de importantes materiais de engenharia, tais como o a?o e o n?quel. No entanto, o desempenho ? conseguido n?o apenas pela melhoria de composi??o, mas tamb?m por t?cnicas de processamento adequadas, tais como, novos m?todos de sinteriza??o, no caso da metalurgia do p?. Desta forma, o objetivo do presente trabalho foi avaliar a dureza, resist?ncia ? flex?o, comportamento dilatom?trico e analisar a microestrutura de comp?sitos de matriz met?lica base n?quel com adi??o de carbetos de t?ntalo e/ou ni?bio quando sinterizados em forno tubular convencional e Plasma assisted debinding sintering (PADS). Os carbetos (5%, 10% e 15% em massa) foram misturados ao p? de n?quel carbonila via ?mido com aux?lio do misturador Y adaptado durante 1h. Ap?s secagem, as misturas foram submetidas ao processo denominado de granula??o em tambor. Utilizou-se 1,5% de parafina (% massa) dilu?da em hexano. Os p?s granulados foram compactados a frio utilizando press?o de 600 MPa. Antes da sinteriza??o a uma taxa de 8 ?C/min com patamar 1h na temperatura de 1150?C tanto em forno tubular quanto em reator PADS, as amostras foram pr?-sinterizadas em forno tubular para extra??o da parafina a uma taxa de 3 ?C/min com patamar 30 min em 500 ?C. A dureza avaliada foi a Brinell e a an?lise microestrutural por MEV. Os resultados mostraram que as amostras sinterizadas assistidas por plasma apresentaram dureza superior ?quelas sinterizadas em forno convencional. As imagens por MEV comprovaram esses maiores valores de durezas, uma vez que a matriz apresentou-se mais densificada. Com rela??o ? adi??o dos carbetos, a dureza aumentou com o aumento da concentra??o dos mesmos. A resist?ncia ? flex?o tamb?m aumentou ao adicionar os carbetos. A retra??o foi maior para a amostra com adi??o de 5% de TaC e 5% NbC. De maneira geral, as composi??es com adi??o de 10% de carbetos apresentaram um aspecto microestrutural menos poroso e com uma distribui??o mais uniforme dos mesmos na matriz de n?quel. Assim, tanto a adi??o de carbetos quanto a sinteriza??o com aux?lio do plasma melhoraram a dureza e o aspecto microestrutural dos comp?sitos