Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2015-12-14T21:40:34Z No. of bitstreams: 1 RonycleiRaimundoDaSilva_DISSERT.pdf: 1911613 bytes, checksum: bc12b6ba49c786087e656fbc0870de75 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2015-12-17T18:43:16Z (GMT) No. of bitstreams: 1 RonycleiRaimundoDaSilva_DISSERT.pdf: 1911613 bytes, checksum: bc12b6ba49c786087e656fbc0870de75 (MD5) / Made available in DSpace on 2015-12-17T18:43:16Z (GMT). No. of bitstreams: 1 RonycleiRaimundoDaSilva_DISSERT.pdf: 1911613 bytes, checksum: bc12b6ba49c786087e656fbc0870de75 (MD5) Previous issue date: 2014-01-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / O sistema Mo-Cu ? um comp?sito usado na ind?stria el?trica como material para contato el?trico e resist?ncia de eletrodo de solda assim como dissipador de calor e absorvedor de microondas em dispositivos microeletr?nicos. O emprego desse material em tais aplica??es se deve as excelentes propriedades de condutividade t?rmica e el?trica e a possibilidade de ajuste do seu coeficiente de expans?o t?rmica para satisfazer aqueles dos materiais usados como substratos dos semicondutores na ind?stria micoreletr?nica. A metalurgia do p? atrav?s dos processos de moagem, conforma??o por prensagem e sinteriza??o ? uma t?cnica vi?vel para consolida??o desse tipo de material. Entretanto, a m?tua insolubilidade de ambos as fases e a baixa molhabilidade do Cu l?quido sobre o Mo dificultam a sua densifica??o. A moagem de alta energia ? uma t?cnica de prepara??o de p?s usada para produzir p?s comp?sitos nanocristalinos, com fase amorfa ou solu??o s?lida estendida, os quais aumentam a sinterabilidade de sistemas imisc?veis como o Mo-Cu. Este trabalho investiga a influ?ncia do heptamolibdato de am?nia (HMA) e da moagem de alta energia na prepara??o de um p? comp?sito HMA-20%Cu assim como o efeito desta prepara??o na densifica??o e estrutura do comp?sito Mo-Cu produzido. P?s de HMA e Cu na propor??o de 20% em massa de Cu foram preparados pelas t?cnicas de mistura mec?nica e moagem de alta energia em um moinho planet?rio. Estes foram mo?dos por at? 50 horas. Para observar a evolu??o das caracter?sticas das part?culas, amostras de p?s foram colhidas ap?s 2, 10, 15, 20, 30 e 40 horas de moagem. Amostras cil?ndricas com 5 e 8 mm de di?metro e 3 a 4 mm de espessura foram obtidas por prensagem a 200 MPa tanto para os p?s misturados como para os mo?dos. Tais amostras foram sinterizada a 1200 oC por 60 minutos sob uma atmosfera de H2. Para verificar o efeito da taxa de aquecimento na estrutura do material durante a decomposi??o e redu??o do HMA, foram usadas as taxas de 2, 5 e 10 oC/min.. Os p?s e as estruturas dos corpos sinterizados foram caracterizados por DRX, MO, MEV e EDS. A densidade dos corpos verdes e sinterizados foi medida usando o m?todo geom?trico (massa/volume). Medidas de microdureza vickers com carga de 20 N durante 15 s foram efetuadas nas estruturas sinterizadas. A densidade das estruturas sinterizadas a 10 oC/min. alcan?ou 99 % da densidade te?rica, em quanto a densidade das estruturas sinterizadas a 2 oC/min. atingiu somente 90 % da densidade te?rica. / The Cu-Mo system is a composite used in the electrical industry as material for electrical contact and resistance welding electrode as well as the heat sink and microwave absorber in microelectronic devices. The use of this material in such applications is due to the excellent properties of thermal and electrical conductivity and the possibility of adjustment of its coefficient of thermal expansion to meet those of materials used as substrates in the semiconductor micoreletr?nic industry. Powder metallurgy through the processes of milling, pressing shaping and sintering is a viable technique for consolidation of such material. However, the mutual insolubility of both phases and the low wettability of liquid Cu on Mo impede its densification. However, the mutual insolubility of both phases and the low wettability of liquid Cu on Mo impede its densification. The mechanical alloying is a technique for preparation of powders used to produce nanocrystalline composite powder with amorphous phase or extended solid solution, which increases the sinterability immiscible systems such as the Mo-Cu. This paper investigates the influence of ammonium heptamolybdate (HMA) and the mechanical alloying in the preparation of a composite powder HMA-20% Cu and the effect of this preparation on densification and structure of MoCu composite produced. HMA and Cu powders in the proportion of 20% by weight of Cu were prepared by the techniques of mechanical mixing and mechanical alloying in a planetary mill. These were milled for 50 hours. To observe the evolution of the characteristics of the particles, powder samples were taken after 2, 10, 15, 20, 30 and 40 hours of milling. Cylindrical samples 5 to 8 mm in diameter and 3 to 4 mm thickness were obtained by pressing at 200 MPa to the mixed powders so as to ground. These samples were sintered at 1200 ? C for 60 minutes under an atmosphere of H2. To determine the effect of heating rate on the structure of the material during the decomposition and reduction of HMA, rates of 2, 5 and 10 ? C / min were used .. The post and the structures of the sintered samples were characterized by SEM and EDS. The density of the green and sintered bodies was measured using the geometric method (weight / volume). Vickers microhardness with a load of 1 N for 15 s were performed on sintered structures. The density of the sintered structures 10 ? C / min. reached 99% of theoretical density, how the density of sintered structures to 2 ? C / min. reached only 90% of the theoretical density

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-01-12T14:20:00Z No. of bitstreams: 1 RodolfoAlbuquerqueBuarqueDeAssuncao_DISSERT.pdf: 3341925 bytes, checksum: 95332904ffdde1cc83db64f825ee63fe (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-18T14:22:16Z (GMT) No. of bitstreams: 1 RodolfoAlbuquerqueBuarqueDeAssuncao_DISSERT.pdf: 3341925 bytes, checksum: 95332904ffdde1cc83db64f825ee63fe (MD5) / Made available in DSpace on 2017-01-18T14:22:16Z (GMT). No. of bitstreams: 1 RodolfoAlbuquerqueBuarqueDeAssuncao_DISSERT.pdf: 3341925 bytes, checksum: 95332904ffdde1cc83db64f825ee63fe (MD5) Previous issue date: 2016-06-30 / O comp?sito Mo-Cu ? muito usado como material para contatos el?tricos e dissipadores de calor devido ?s excelentes propriedades do cobre de condutividade t?rmica e el?trica e boa trabalhabilidade, aliada ? alta resist?ncia a solda e eros?o por arco el?trico do molibd?nio. No primeiro caso, formas bastante simples s?o exigidas e a infiltra??o de cobre l?quido em um esqueleto de molibd?nio pr?-sinterizado ? a t?cnica de consolida??o normalmente utilizada. Diferentemente, geometrias mais complexas e densidades iguais ou pr?ximas da te?rica s?o necess?rias para aplica??o como dissipadores de calor. A metalurgia do p? atrav?s das t?cnicas de prepara??o de p?s com processamento por moagem de alta energia, compacta??o ou moldagem de p? por inje??o e sinteriza??o ? uma rota bastante vi?vel para produ??o desses componentes. Entretanto, a baixa solubilidade entre cobre e molibd?nio dificulta a obten??o de densidade igual ou pr?xima da densidade te?rica. Este trabalho investiga a obten??o do comp?sito Mo-27,82%?Cu preparado por moagem de alta energia e mistura mec?nica dos p?s de cobre e heptamolibdato de am?nio (HMA) de f?rmula qu?mica (NH4)6Mo7O24 .4H2O, decomposto e reduzido por H2, antes e durante a sinteriza??o, evidenciando duas rotas de fabrica??o diferentes para o material. A influ?ncia da press?o de compacta??o na densifica??o e microestrutura do comp?sito Mo-27,82%?Cu tamb?m foi investigada. Para isto, os p?s mo?dos por 50 horas foram prensados a 200, 400 e 600 MPa. Para se entender o efeito da temperatura na densidade e microestrutura do comp?sito Mo-27,82%?Cu, amostras foram sinterizadas a 1000, 1100 e 1200 oC. Os corpos prensados a 200 e 400 MPa e sinterizados a 1200 oC alcan?aram a maior densidade entre as amostras produzidas, no valor de 94?0,4 % da densidade te?rica. Por?m, aqueles que foram decompostos e reduzidos durante a sinteriza??o apresentaram trincas de fabrica??o. J? os corpos sinterizados a 1100 oC atingiram o maior valor de microdureza (571,70?78,82 HV), apesar de uma baixa densidade em rela??o a te?rica (79,17?1,78%). / The Mo-Cu composite is a material used for electrical contact and heat sinks due its excellent properties of thermal and electrical conductivity and cooper good workability allied to its great resistance welding and electrical arc erosion of molybdenum. In the first case, simple shapes are required and the infiltration of the pre-sintered molybdenum skeleton with liquid copper is the technique of consolidation normally used. On the second case, more complex geometries and a density near or equal the theoretical density are required for the application as heat sink. The powder metallurgy is a very viable route for the production of these components, through the techniques of powder preparation processed by mechanical alloying, compaction or casting. However, the low dissolution of one component in the other and the liquid copper high contact angle on the molybdenum phase difficult the obtainment of a density near or equal the theoretical density. This research investigates the obtainment of the Mo-27,82%?Cu composite prepared by mechanical alloying and mechanical mix of the copper powders and ammonium heptamolybdate (HMA) of chemical formula (NH4)6Mo7O24 .4H2O, decomposed and reduced by ?2 before and during the sintering, showing two different fabrication routes for the material. The compaction pressure influence at the densification and microstructure of the Mo-27,82%?Cu composite were also investigated. For this, the powder milled for 50 hours and the mixed powder were pressed at 200, 400 and 600 MPa. In order to understand the temperature effect at the density and microstructure were sintered at 1000, 1100 and 1200 ?C. The bodies pressed at 200 and 400 MPa and sintered at 1200?C reached 94?0,4 % of the theoretical density. However, those which were decomposed and reduced during sintering showed manufacturing cracks. On the other hand, the bodies sintered at 1100 ?C reached the highest microhardness value (571,70?78,82 HV), despite a low theory density (79.17 ? 1.78%).