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.