Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-01-12T14:19:58Z No. of bitstreams: 1 AntonioRobertoAugusto_DISSERT.pdf: 15947966 bytes, checksum: 6137cc9dd87967a91d0ea2a7fd5913a0 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-01-17T13:19:05Z (GMT) No. of bitstreams: 1 AntonioRobertoAugusto_DISSERT.pdf: 15947966 bytes, checksum: 6137cc9dd87967a91d0ea2a7fd5913a0 (MD5) / Made available in DSpace on 2017-01-17T13:19:05Z (GMT). No. of bitstreams: 1 AntonioRobertoAugusto_DISSERT.pdf: 15947966 bytes, checksum: 6137cc9dd87967a91d0ea2a7fd5913a0 (MD5) Previous issue date: 2014-09-01 / A lideran?a mundial brasileira na obten??o de etanol derivado da cana de a??car pode ser associada ? produ??o do vinhoto, em uma raz?o de 10 a 18 litros de vinhoto para cada litro de etanol produzido durante o processo de destila??o. Nos cultivos da cana-de-a??car, esse vinhoto tem sido aplicado como adubo org?nico, onde o seu bombeamento ? um elemento cr?tico dessa cadeia produtiva. O objetivo deste trabalho foi investigar os principais mecanismos de desgaste de um rotor e de partes de uma bomba centr?fuga ap?s bombear vinhoto tratado em reator (pH 7,3?0.5). Um filme de 300?75 ?m de metal duro ? base de carboneto de tungst?nio-cobalto (WC-Co) foi aplicado ao rotor de ferro fundido cinzento da bomba atrav?s da t?cnica de aspers?o t?rmica HVOF. Considerando-se os trinta anos de experi?ncia do autor no projeto de sistemas de bombeamento, uma bancada para o bombeamento de vinhoto a 27?2oC foi desenvolvida em Laborat?rio para um servi?o de 1.000 horas atrav?s de ensaios durante dez horas di?rias e cont?nuas de uma bomba modelo INI 32-125 operando sob condi??es de cavita??o, conforme o c?lculo de NPSH. Um sistema de recircula??o do vinhoto foi adotado e controlado por uma v?lvula de descarga empregada comumente em processos industriais. Ap?s os ensaios, tanto o rotor revestido pelo metal duro como algumas partes n?o revestidas da bomba apresentaram um desgaste severo por cavita??o-eros?o, enquanto partes do rotor onde os efeitos da cavita??o s?o menores, o revestimento apresentou um desgaste moderado. / The Brazilian capability concerning to the world's leading producer of sugarcane ethanol can be joined together the vinasse production, which inherent amount discharged by distilling is from 10 to18 liters of vinasse per liter of ethanol produced. This vinasse has been applied in sugar-cane crops as organic fertilizer, where its pumping process is a critical element in this string. The aim of this work was investigate the main wear mechanisms of an impeller and parts of a centrifugal pump after pumping vinasse treated in reactor (pH 8,3?0,7). A tungsten carbide-cobalt (WC10Co4%Cr) film based hard metal of 360?35?m ?m was applied on the grey cast iron pump impeller by HVOF thermal aspersion. Based on the 30 years of experience of the author in the design and mounting of pumping systems, a test rig was developed in Laboratory for 1,000 hours of pumping tests of vinasse at 27?2oC for a continuous service during 10 hours by day for a pump model 32-125, working under cavitation conditions through the calculation of Net Positive Suction Head (NPSH), A recirculating system of the vinasse was adopted and controlled by a discharge valve usually employed in the industrial processes. After the tests, both the coated rotor as the uncoated parts of the pump showed severe wear by cavitation-erosion, while parts of the rotor where the effects of cavitation are smaller, the coating showed a moderate wear.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-04-03T19:34:53Z No. of bitstreams: 1 MarianaChiancaLucioDaSilva_DISSERT.pdf: 4659510 bytes, checksum: cbcbd1ce303a5a396ae5c3538766d017 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-04-04T23:23:59Z (GMT) No. of bitstreams: 1 MarianaChiancaLucioDaSilva_DISSERT.pdf: 4659510 bytes, checksum: cbcbd1ce303a5a396ae5c3538766d017 (MD5) / Made available in DSpace on 2017-04-04T23:23:59Z (GMT). No. of bitstreams: 1 MarianaChiancaLucioDaSilva_DISSERT.pdf: 4659510 bytes, checksum: cbcbd1ce303a5a396ae5c3538766d017 (MD5) Previous issue date: 2017-02-16 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O carbeto de tungst?nio (WC) ? amplamente conhecido por suas excelentes propriedades f?sicas e mec?nicas, por?m, apresenta limita??es de uso principalmente quando a propriedade de tenacidade ? solicitada e h? a necessidade de um material mais leve. Como alternativa para minimizar essa problem?tica, a proposta ? a produ??o de um material que alie as propriedades do WC com a alumina (Al2O3), diminuindo assim a sua densidade e promovendo o aumento da tenacidade a determinada temperatura. Assim, neste trabalho, estudou-se os efeitos do percentual da alumina e dos par?metros de processamento da metalurgia do p? na microestrutura do particulado e do sinterizado (WC-Al2O3). E, al?m disso, foram analisadas propriedades f?sicas e mec?nicas, particularmente a densidade e a microdureza, do produto buscando um material de ferramenta de corte alternativo. No estudo, adotou-se, respectivamente, a rota de produ??o de materiais particulados. Os p?s do sistema apresentaram as seguintes composi??es: WC com 5, 10 e 15%p. de Al2O3; que foram processados via moagem de alta energia (MAE), em moinho planet?rio durante, 1, 4 e 10 horas. A conforma??o dos p?s mo?dos foi realizada por prensagem uniaxial de matriz cil?ndrica de di?metro de 5 mm, e com a press?o de compacta??o de 400 MPa. A sinteriza??o foi realizada em forno resistivo via fase s?lida, sob atmosfera controlada (arg?nio), nas temperaturas de 1450?C e 1550?C, durante 1 hora, e com uma taxa de aquecimento de 10?C/min. As mat?rias-primas foram caracterizadas atrav?s dos ensaios de particulometria, difra??o de raio-X (DRX) e microscopia eletr?nica de varredura (MEV). As amostras mo?das e sinterizadas foram submetidas aos mesmos ensaios de caracteriza??o dos p?s iniciais. E, os ensaios de microdureza foram realizados com as amostras sinterizadas. Os resultados mostraram que a moagem de alta energia influenciou significativamente na redu??o da distribui??o de tamanho, entretanto, n?o houve dispers?o das fases constituintes do material. E, devido a sinteriza??o ou consolida??o parcial dos compactados a verde, os valores de microdureza foram baixos, resultante da heterogeneidade da microestrutura que apresentou aglomerados das fases (WC-WC e Al2O3 -Al2O3), e, tamb?m, uma alta porcentagem de poros. Contudo, a alumina influenciou no refinamento da microestrutura dos sinterizados. / Tungsten Carbide (WC) is best known for its excellent physical and mechanical properties. However, it has limitations, mainly when the tougher and lighter material is requested. An alternative to minimize these problems is a composite of WC and alumina (Al2O3) to reducing density and promoting toughness at certain temperatures. Thus, in this work, the effects of the different amount of alumina and powder metallurgy processing parameters on microstructure of particulate and sintered composite (WC-Al2O3) were studied and the mechanical properties, particularly the microhardness, of the product were analyzed to find an alternative cutting tool material. In the study, the particulate materials production route was applied. The powders of the system have the following compositions: WC with 5, 10 and 15wt% of Al2O3 processed by high energy milling in a planetary milling for 1, 4 and 10 hours. Compacting of mixed powders was done using a uniaxial press in a cylindrical die of 5 mm diameter under a pressure of 400 MPa. Solid phase sintering was performed in a resistance furnace at 1450 and 1550 ?C with 1 hour of holding time and heating rate of 10?C/min in argon atmosphere. The raw materials were characterized by particulometry, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The milled powders and sintered samples were subjected to the same tests and microhardness test was also done for sintered samples as well. The results showed that high energy milling met the targets for particle size and however, there was no dispersion of the constituent phases of the material. Due to the sintering or partial consolidation of the green compacts, the microhardness values were low, due to the heterogeneity of the microstructure that presented agglomerates of the phases (WC-WC and Al2O3 -Al2O3), and also a high percentage of pores. However, alumina influenced the sintering microstructure refinement.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-06-02T19:56:11Z No. of bitstreams: 1 RuanSavioDaCostaTertuliano_DISSERT.pdf: 5270679 bytes, checksum: e7cecd59df0a1f5abd8a454eb7de168d (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-06-06T20:49:20Z (GMT) No. of bitstreams: 1 RuanSavioDaCostaTertuliano_DISSERT.pdf: 5270679 bytes, checksum: e7cecd59df0a1f5abd8a454eb7de168d (MD5) / Made available in DSpace on 2017-06-06T20:49:20Z (GMT). No. of bitstreams: 1 RuanSavioDaCostaTertuliano_DISSERT.pdf: 5270679 bytes, checksum: e7cecd59df0a1f5abd8a454eb7de168d (MD5) Previous issue date: 2017-04-06 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A busca por materiais de alto valor agregado, alta aplicabilidade e elevada sustentabilidade motiva inova??es em todas as ?reas da engenharia. Um dos materiais desenvolvidos atualmente com tais requisitos s?o os carbetos dopados, que s?o compostos de cer?mica e metais. Este trabalho prop?e a s?ntese, caracteriza??o e avalia??o cin?tica do carbeto de tungst?nio dopado com cobalto (WC-Co). As etapas de produ??o do material s?o: s?ntese do precursor por via ?mida mediante agita??o em etanol de uma mistura de paratungstato de am?nio e nitrato de cobalto, secagem da lama obtida em mufla por 18h a 80?C, maceragem do p? seco, caracteriza??o preliminar usando as t?cnicas de MEV, DRX e EDS, rea??o g?s-s?lido de carborredu??o a 750, 800 e 850?C em atmosfera com 5% de metano e 95% hidrog?nio em reator de leito fixo e leito rotativo (agita??o de 34 rpm) e caracteriza??o final usando as t?cnicas j? citadas. Os resultados obtidos mostram um material contendo part?culas de carbeto de tungst?nio com o cobalto aderido de boa ?rea interfacial e aplic?vel a ?reas como: em catalisadores, reatores ? membrana e c?lulas combust?veis, o que ressalta a import?ncia desse tipo de pesquisa. / The search for high value-added materials, wide applicability and high sustainability encourages innovation in all areas of engineering. One of the materials currently being developed with such requirements are the doped carbides, which are composed with a mix of ceramics and metals. This work proposes the synthesis, characterization, kinetic evaluation and of tungsten carbide doped with cobalt (WC-Co) in fix and rotating bed reactor. The steps of material production was: synthesis of the precursor of washed by stirring in ethanol of a mixture of ammonium paratungstate and cobalt nitrate, drying th/e slurry obtained in oven for 18h at 80 ?C, the dry powder milling, preliminary characterization by SEM techniques, XRD and SDS, gas-solid reaction of reduction at 750, 800 and 850 ? C in an atmosphere of 5% methane and 95% hydrogen in fix bed and rotating bed reactor (at 34 rpm agitation) and the final characterization using the aforementioned techniques. The results show a material containing particles of tungsten carbide with cobalt adhered, with good interfacial and applicable in areas such as in catalysts, membrane reactors and fuel cells, which emphasizes the importance of such research.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-12-12T17:53:46Z No. of bitstreams: 1 MariaJoseSantosLima_TESE.pdf: 8256758 bytes, checksum: 2af332071bb76b3070e1cdcc7d8adcb2 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-12-13T17:58:53Z (GMT) No. of bitstreams: 1 MariaJoseSantosLima_TESE.pdf: 8256758 bytes, checksum: 2af332071bb76b3070e1cdcc7d8adcb2 (MD5) / Made available in DSpace on 2017-12-13T17:58:53Z (GMT). No. of bitstreams: 1 MariaJoseSantosLima_TESE.pdf: 8256758 bytes, checksum: 2af332071bb76b3070e1cdcc7d8adcb2 (MD5) Previous issue date: 2017-07-18 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Neste trabalho foram sintetizados p?s-comp?sitos WC-Ni atrav?s de Carborredu??o da mistura de paratungstato de am?nio hidratado (APT) com o nitrato de n?quel nas propor??es (5% p.Ni, 10% p.Ni e 15% p.Ni) a baixa temperatura (800?C a 950?C) e em curto tempo de rea??o (90 min a 150 min) em um ?nico processo de s?ntese. Os p?s foram caracterizados por difra??o de raios X, microscopia eletr?nica de varredura, espectroscopia de energia dispersiva (EDS), e fluoresc?ncia de raios X (FRX), an?lise de tamanho de part?culas e adsor??o de nitrog?nio pela t?cnica do BET, al?m de medidas de magnetiza??o, coercividade e reman?ncia. O estudo do tamanho de cristalito foi obtido a partir dos dados dos difratogramas de raios X dos p?s-comp?sitos, atrav?s da equa??o de Scherrer. Foi realizado um planejamento experimental fatorial 23 com tr?s pontos centrais com a finalidade avaliar a influ?ncia das condi??es de s?ntese nas vari?veis-resposta. Os par?metros de s?ntese avaliados neste trabalho foram: tempo de rea??o (90min, 120min e 150min), temperatura de s?ntese (800?C, 850?C e 900?C) e concentra??o de n?quel em peso (5%p.Ni, 10%p.Ni e 15%p.Ni). Foi poss?vel produzir p?s-comp?sitos de WC-Ni nonom?tricos nas propor??es desejadas com a pureza desejada, com tamanho m?dio de cristalito variando de 24,2 nm at? 38 nm, com ?rea superficial variando de 24,6 m?/g at? 46,7 m?/g. Os p?s apresentaram morfologia com part?culas de tamanhos e formas variadas, bastante aglomeradas, bem como uma boa dispers?o e homogeneiza??o das fases. As caracter?sticas espec?ficas desses materiais nanom?tricos proporcionam a sua utiliza??o tanto para a produ??o de metal duro como em rea??es catal?ticas. Os p?s-comp?sitos obtidos neste trabalho foram aplicados na produ??o de metal duro-WC-Ni atrav?s de sinteriza??o em fase s?lida e l?quida, utilizando as t?cnicas de sinteriza??o convencional e sinteriza??o por ?spark plasma sintering? para fins de compara??o. Nas amostras sinterizadas, foram realizadas medidas de dureza Vickers e densidade por picnometria. Tamb?m foram realizadas an?lises de DRX, MEV e EDS com mapeamento. Os melhores resultados para as os sinterizados de WC-Ni, foram obtidos para as amostras sinterizadas via SPS a 1350?C, apresentando dureza Vickers (2322 HV) e densidade (97,67 %) superiores as das amostras sinterizadas por sinteriza??o convencional a maiores temperaturas. / In this work WC-Ni composite powders were synthesized by carborreduction of the hydrated ammonium paratungstate (APT) mixture with the nickel nitrate in proportions (5% p.Ni, 10% p.Ni and 15% p.Ni) a low temperature (800 ? C to 950 ? C) and small reaction time (90min to 150min) in a single synthesis process. The powders were characterized mainly by X-ray diffraction, scanning electron microscopy (SEM), dispersive energy spectroscopy (EDS), X-ray fluorescence (FRX), particle size analysis and (BET) and measures of magnetization, coercivity and remanence. The study of crystallite size was obtained from the X-ray diffractograms of post-composites, using the Scherrer equation. A factorial experimental design 23 with three central points was carried out to evaluate the influence of the synthesis conditions on the response variables (crystallite size). The synthesis parameters evaluated in this work were: reaction time (90min, 120min and 150min), synthesis temperature (800 ? C, 850 ? C and 900 ? C) and concentration of nickel by weight (5% p.Ni, 10 % P.Ni and 15% p.Ni). It was possible to produce nanometric WC-Ni composite powders in the desired proportions with the desired purity, with a mean crystallite size varying from 24.2 nm to 38 nm, with a surface area ranging from 24.6m?/g to 46.7 m?/g. The powders presented morphology with particles of varied sizes and shapes, quite agglomerated and also presented a good dispersion and homogenization of the phases. The specific characteristics of these nanometric materials provide their use for both the hard metal in catalytic reactions.Therefore, the composite powders obtained in this work were applied in the production of WC-Ni hard metal by solid and liquid phase sintering using conventional sintering and Spark Plasma Sintering techniques for comparison purposes. In the sintered samples the measurements of Vickers hardness and density by pycnometry were performed. We also performed XRD, SEM and EDS analyzes with mapping. The best results for the sintered WC-Ni were obtained for the sintered samples via SPS at 1350?C, showing Vickers hardness (2322 HV) and density (97.67%) higher than the samples sintered by conventional sintering at higher temperatures. / 2018-08-23

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-07-22T14:59:52Z No. of bitstreams: 1 HeytorVitorSouzaBezerraDeAzevedo_DISSERT.pdf: 4226943 bytes, checksum: 879f905d96e12f6e15faa6de0fec4be5 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-07-26T22:08:45Z (GMT) No. of bitstreams: 1 HeytorVitorSouzaBezerraDeAzevedo_DISSERT.pdf: 4226943 bytes, checksum: 879f905d96e12f6e15faa6de0fec4be5 (MD5) / Made available in DSpace on 2016-07-26T22:08:45Z (GMT). No. of bitstreams: 1 HeytorVitorSouzaBezerraDeAzevedo_DISSERT.pdf: 4226943 bytes, checksum: 879f905d96e12f6e15faa6de0fec4be5 (MD5) Previous issue date: 2016-01-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Comp?sitos ? base de alumina (Al2O3), carbeto de tungst?nio (WC) e cobalto (Co) apresentam propriedades espec?ficas como baixa densidade, alta resist?ncia ? oxida??o, alto ponto de fus?o e elevada in?rcia qu?mica. Esse comp?sito revela ser um material promissor para ser aplicado em diversos campos da engenharia. Este trabalho tem como objetivo avaliar algumas propriedades mec?nicas durante a confec??o e, ap?s a sinteriza??o do comp?sito (Al2O3 - WC - Co). P?s comp?sitos com a composi??o de 80%.p de Al2O3, 18%.p de WC e 2%.p de Co foram processados pela rota de moagem de alta energia (MAE), em moinho planet?rio por 50 horas, bem como por mistura manual em um recipiente de vidro, seguindo a mesma propor??o em peso. Amostras foram coletadas (2, 10, 20, 30, 40 e 50 horas) durante o processo de moagem. Em seguida, os p?s foram prensados no formato de amostra circular com di?metro de 5 mm em uma prensa uniaxial com press?es de 200 e 400 MPa. A sinteriza??o ocorreu de duas maneiras: a primeira sinteriza??o via fase s?lida foi realizada ? 1300 ?C e ? 1126 ?C durante 1h com taxa de aquecimento de 10?C/min em forno resistivo sob atmosfera de arg?nio as press?es de compacta??o utilizadas foram de 200 e 400 MPa, a segunda sinteriza??o foi realizada em dilat?metro via fase s?lida ? 1300 ?C com press?o de compacta??o de 200 MPa, tamb?m foi realizada em dilat?metro outra sinteriza??o, desta vez por fase l?quida ? 1550 ?C com press?es de compacta??o de 200 e 400 MPa, obedecendo os mesmos par?metros utilizados no forno resistivo. As mat?rias-primas foram caracterizadas por difra??o de raios X - (DRX), fluoresc?ncia de raios X - (FRX), microscopia eletr?nica de varredura (MEV), espectroscopia por dispers?o de energia (EDS) e particulometria a laser. As amostras sinterizadas foram submetidas a ensaios de microdureza. Os resultados mostraram que a moagem de alta energia atingiu os objetivos quanto ao tamanho de part?cula e a densifica??o do comp?sito. Entretanto, a microdureza n?o alcan?ou resultados significativos, isso ? um ind?cio que o comp?sito possui baixa tenacidade ? fratura. / Composites based on alumina (Al2O3), tungsten carbide (WC) and cobalt (Co) exhibit specific properties such as low density, high oxidation resistance, high melting point and high chemical inertia. That composite shows to be a promising material for application in various fields of engineering. In this work, the mechanical properties of the composite (Al2O3 ? WC ? Co), particularly density and hardness, were evaluated according to the effects of the variables of powder processing parameters, green compact and sintered. Powder composites with the composition of 80 wt% Al2O3, 18 wt% WC and 2 wt% Co were processed by high energy ball milling in a planetary mill for 50 hours as well as mixed by manual mixing in a glass vessel with the same proportion. Samples were collected (2, 10, 20, 30, 40 and 50 hours) during the milling process. Then, the powders were compacted in a cylindrical die with 5 mm in diameter in a uniaxial press with pressures of 200 and 400 MPa. The sintering was in two stages: first, the solid phase sintering was performed at 1126 and 1300 ?C for 1 hour with a heating rate of 10 ?C/min in a resistive furnace under argon atmosphere for green samples compacted in 200 and 400 MPa; the second sintering was performed on dilatometer in solid phase at 1300 ?C for green sample compacted in 200 MPa, another sintering also was performed on dilatometer, this time in liquid phase at 1550 ?C for green samples compacted in 200 and 400 MPa, with the same parameters used in resistive furnace. The raw materials were characterized by X ? ray diffraction (XRD), X ? ray fluorescence (XRF), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and laser particlemeter. The sintered samples were subjected to microhardness testing. The results showed that high energy milling achieved to the objectives regarding the particle size and the dispersion of composite phases. However, the hardness did not achieve to significant results, this is an indication that the composite has low fracture toughness.