Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-11-22T20:52:06Z No. of bitstreams: 1 AnaEmiliaDinizSilvaGuedes_TESE.pdf: 9494896 bytes, checksum: 3ab916a68a0925f9bdd33da14e59c06b (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-11-23T23:34:34Z (GMT) No. of bitstreams: 1 AnaEmiliaDinizSilvaGuedes_TESE.pdf: 9494896 bytes, checksum: 3ab916a68a0925f9bdd33da14e59c06b (MD5) / Made available in DSpace on 2017-11-23T23:34:34Z (GMT). No. of bitstreams: 1 AnaEmiliaDinizSilvaGuedes_TESE.pdf: 9494896 bytes, checksum: 3ab916a68a0925f9bdd33da14e59c06b (MD5) Previous issue date: 2017-03-14 / A obten??o de nanomateriais com propriedades espec?ficas para aditiva??o de ?leo para lubrificante industrial ainda ? um desafio, mas tem gerado expectativas que podem minimizar problemas de cunho tribol?gico, onde o atrito e o desgaste s?o os principais respons?veis por falhas em equipamentos e m?quinas. O objetivo desta tese foi determinar condi??es ?timas de s?ntese de nanopart?culas via micro-ondas para gerar nanopart?culas de ?xidos de ferro com propriedades caracter?sticas para serem aplicadas a lubrificantes. Para tanto, variou-se pot?ncia e tempo de s?ntese em tr?s niveis, para avaliar suas influ?ncias nas propriedades f?sico-qu?micas das nanopart?culas. A caracteriza??o das nanopart?culas foi realizada por DRX, MEV, MET, SAXS, UV-vis, FTIR e PPMS. Ap?s a caracteriza??o, foram selecionadas as nanopart?culas que apresentassem morfologia com tend?ncia esf?rica, que n?o sofreram oxida??o ap?s a s?ntese, resultando em fases mais est?veis do ?xido de ferro. Ap?s a aditiva??o destes ?xidos em uma base lubrificante, avaliou-se o desempenho tribol?gico deste ferrofluido atrav?s de trib?metro esfera sobre disco na presen?a e aus?ncia de um campo magn?tico fixo e constante. As an?lises tribol?gicas do a?o e o desempenho do lubrificante foram realizados atrav?s do coeficiente de atrito e caracteriza??o do desgaste do disco atrav?s do MEV. O processo de s?ntese das nanopart?culas estudado se mostrou eficiente e mais r?pido que as tradicionais, com caracter?sticas superparamagn?ticas e tamanho de gr?o abaixo de 15 nm. Percebeu-se ainda a exist?ncia de uma correla??o entre o tamanho de gr?o e tempo de s?ntese, e que estes nano-?xidos permaneceram est?veis ? oxida??o ao final do processo. O recobrimento e uso de dispersante permitiu obter solu??es est?veis. As SPIONS (nanopart?culas superparamagn?ticas), como aditivos, tiveram bom comportamento antidesgaste e redutor do atrito, podendo ser comparadas a um lubrificante comercial, tendo resultados superiores quando o nanolubrificante ? exposto a um campo magn?tico fixo. / The obtaining of nanomaterials with specific properties for additivation of oil for industrial lubricant is still a challenge, but there are some expectations that may minimize tribological problems, which are primarily responsible for failures in equipment and machinery. The purpose of this thesis is to determine the optimal conditions for synthesis of these nanoparticles by microwaves, which generate nanoparticles of iron oxides with specific properties to be applied to lubricants. For this, power and time of synthesis were varied in 3 levels to evaluate their influence on the physicochemical properties of the nanoparticles. The characterization of the nanoparticles was performed by XRD, SEM, TEM, SAXS, UV-Vis, FTIR, VSM and PPMS. After characterization, the nanoparticles that presented morphology with a spherical tendency and which did not undergo oxidation after synthesis were selected, resulting in more stable phases of iron oxide. After the addition of these oxides in a lubricant base, it was evaluated the tribological performance of this ferrofluid through tribometer sphere on disk in the presence and absence of a fixed and constant magnetic field. The tribological analyzes of the steel and the performance evaluation of the lubricant were performed through wear characterization on the disc via SEM and considering the coefficient of friction during the tests, respectively. The nanoparticle synthesis process was more efficient and faster than traditional nanoparticles with superparamagnetic characteristics and grain size below 15 nm. It is further noticed the existence of a correlation between grain size and time syntheses. Also, the nano-oxides remained stable upon oxidation at the end of the process. The coating and the usage of dispersant resulted in stable solutions. SPIONS (superparamagnetic nanoparticles) as additives had anti-wear and friction-reducing behavior, although it varied with the type of sample, quantity of the additive and presence or absence of the magnetic field. Although some SPIONS presented as additives have good anti-wear and friction-reducing behavior, it can be compared to a commercial lubricant, having better superior results when the nanolubrifier is exposed to a fixed magnetic field.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-11-22T20:52:06Z No. of bitstreams: 1 ValdicleideSilvaEMello_TESE.pdf: 9723505 bytes, checksum: b50a18bfb9494080353e8e9f0c36a628 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-11-23T23:41:33Z (GMT) No. of bitstreams: 1 ValdicleideSilvaEMello_TESE.pdf: 9723505 bytes, checksum: b50a18bfb9494080353e8e9f0c36a628 (MD5) / Made available in DSpace on 2017-11-23T23:41:33Z (GMT). No. of bitstreams: 1 ValdicleideSilvaEMello_TESE.pdf: 9723505 bytes, checksum: b50a18bfb9494080353e8e9f0c36a628 (MD5) Previous issue date: 2017-02-21 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / O desafio da nanotecnologia aplicada na lubrifica??o automotiva est? no controle e na manipula??o de par?metros de processamento para tornar poss?vel a aplica??o de nanopart?culas como aditivos para lubrificantes. Tais par?metros extrapolam apenas uma ?rea do conhecimento, e para obter o ?xito, se faz necess?rio trazer ? esta tem?tica conhecimentos multidisciplinares, utilizando de conceitos da qu?mica, f?sica, mec?nica e tribologia. Nessa tese, foram estudados os efeitos de diferentes par?metros de processamento citados pela literatura que podem causar melhorias na atua??o antidesgaste de nanopart?culas em ?leos lubrificantes, desde o tamanho, a concentra??o, a dispers?o, o agente de modifica??o de superf?cie da part?cula, o agente dispersante e a rugosidade dos corpos em contato atrav?s de um conjunto de t?cnicas discutidas ao decorrer do trabalho. Os resultados mostraram que a maior pot?ncia (495 W) utilizada durante a s?ntese de nanopart?culas em micro-ondas resultou em menor tamanho de part?cula e melhor dispers?o no ?leo, mas a forma da nanopart?cula n?o foi influenciada. A utiliza??o de ?cido oleico, como agente de recobrimento, e tolueno, como dispersante, melhorou a dispers?o das nanopart?culas no ?leo. Foi identificada uma faixa de rugosidade na qual as nanopart?culas se depositaram nos sulcos da superf?cie e atuam positivamente na redu??o do coeficiente de atrito. Por outro lado, nas condi??es de baixa e alta rugosidade, o atrito e o desgaste s?o potencializados. A a??o antidesgaste foi melhorada nos n?veis mais baixos de concentra??o de NNP no ?leo lubrificante (0,1%) n?o apenas em estado estacion?rio, mas tamb?m nas etapas de running-in. Nessa tese, ap?s a manipula??o de diversos par?metros de processamento, foram preenchidas lacunas deixadas na literatura em rela??o aos mecanismos de atua??o das nanopart?culas quando aditivadas em ?leos lubrificantes e foi poss?vel alcan?ar uma condi??o na qual as nanopart?culas se equiparam aos resultados exibidos com um aditivo comumente usado (ZDDP) . / The challenge of nanotechnology applied in automotive lubrication is in control and manipulation of processing parameters to make possible the application of nanoparticles as additives in lubricants. These parameters flee just one area of knowledge, but that, for the success, it is necessary to bring to this theme multidisciplinary knowledge, making use of concepts from chemistry, physics, mechanics and tribology. In this thesis, were studied the effect of the different processing parameters mentioned in the literature that may cause improvement in antiwear performance of nanoparticles in lubricating oils since the size, concentration, dispersion, surface modifying agent particle, dispersing and surface roughness of the bodies in contact through a range of techniques discussed in the course of work. The results showed that the highest power used (495 W) during the synthesis of nanoparticles in a microwave results in smaller particle size and better dispersion in oil. However, the shape of the nanoparticle was not influenced. The use of oleic acid as coating agent and toluene as the dispersant improved dispersion of the nanoparticles in oil. A smoothness range has been identified in which the nanoparticles were deposited on the surface grooves and had a positive effect in reducing friction, but in the conditions of high and low surface roughness, friction and wear are enhanced. The anti-wear action has been improved at the lowest levels of NNP concentration in the lubricating oil (0,1%) not only steady state but also in the running-in too. In this thesis, after manipulation of several processing parameters, some gaps left in the literature were filled regarding the action of nanoparticles mechanisms when additives in lubricating oils. And it was possible to achieve a condition in which the nanoparticles match the results displayed with a commonly used additive (ZDDP).