Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-09-04T20:41:25Z No. of bitstreams: 1 RayaneRicardoDaSilva_DISSERT.pdf: 3651048 bytes, checksum: 6930b6cb5290f28628f512cd882c69ad (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-09-06T20:43:02Z (GMT) No. of bitstreams: 1 RayaneRicardoDaSilva_DISSERT.pdf: 3651048 bytes, checksum: 6930b6cb5290f28628f512cd882c69ad (MD5) / Made available in DSpace on 2017-09-06T20:43:03Z (GMT). No. of bitstreams: 1 RayaneRicardoDaSilva_DISSERT.pdf: 3651048 bytes, checksum: 6930b6cb5290f28628f512cd882c69ad (MD5) Previous issue date: 2017-03-02 / Este trabalho tem como objetivo a s?ntese do Nitreto de Ni?bio, a partir do precursor tris (oxalato) oxiniobato de am?nio hidratado, atrav?s de rea??o g?s-s?lido em reator de leito fixo. Os par?metros reacionais para o tratamento t?rmico para obter o NbN foram com as temperaturas de 700, 800, 900, 1000 e 1100 ?C variando o tempo na isoterma entre 3, 4 e 5 horas. A mistura gasosa ? composta de nitrog?nio e hidrog?nio. A composi??o e a vaz?o total do fluxo de gases foram variadas, como tamb?m a massa do precursor utilizado na rea??o. Os materiais obtidos foram caracterizados atrav?s de difra??o de raios-X (DRX), Refinamento Rietveld e Microscopia Eletr?nica de Varredura (MEV). Com o aumento da temperatura de rea??o e tempo na isoterma observamos a mudan?a de fase de ?xido de ni?bio para nitreto de ni?bio. Houve a forma??o de duas fases de nitreto, estando a fase hexagonal presente em maior quantidade, e a tetragonal em menor quantidade. Com a maior vaz?o, foi obtido o nitreto de ni?bio com alto teor de pureza. / The aim of this work is to study the synthesis of Niobium Nitride, starting from the precursor tris (oxalate) oxiniobate ammonium hydrate, through the gas-solid reaction in a fixed-bed reactor. The heat treatment reaction parameters to obtain the NbN were at temperatures 700, 800, 900 and 1000?C varying the time in the isotherm between 3, 4 and 5 hours. The gas mixture is composed of nitrogen and hydrogen. The composition and the total flow of the gas flow were varied, as well as the mass of the precursor used in the reaction. The obtained materials were characterized by X-ray diffraction (XRD), Rietveld Refinement and Scanning Electron Microscopy (SEM). Increasing the reaction temperature and time in the isotherm it was observed the phase change of niobium oxide to niobium nitride. There was formation of two phases of nitride, and the hexagonal phase is present in greater quantity, and the tetragonal phase in less quantity. With the higher flow rate, the high purity niobium nitride was obtained.

Made available in DSpace on 2014-12-17T14:07:15Z (GMT). No. of bitstreams: 1 MariaVMS_Parcial.pdf: 533267 bytes, checksum: dfba6ad9f2b0c2ad0d26dac46721fabf (MD5) Previous issue date: 2013-10-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The refractory metal carbides have proven important in the development of engineering materials due to their properties such as high hardness, high melting point, high thermal conductivity and high chemical stability. The niobium carbide presents these characteristics. The compounds of niobium impregnated with copper also have excellent dielectric and magnetic properties, and furthermore, the Cu doping increases the catalytic activity in the oxidation processes of hydrogen. This study aimed to the synthesis of nanostructured materials CuNbC and niobium and copper oxide from precursor tris(oxalate) oxiniobate ammonium hydrate through gas-solid and solid-solid reaction, respectively. Both reactions were carried out at low temperature (1000?C) and short reaction time (2 hours). The niobium carbide was produced with 5 % and 11% of copper, and the niobium oxide with 5% of copper. The materials were characterized by X-Ray Diffraction (XRD), Rietveld refinement, Scanning Electron Microscopy (SEM), X-Ray Fluorescence Spectroscopy (XRF), infrared spectroscopy (IR), thermogravimetric (TG) and differential thermal analysis (DTA , BET and particle size Laser. From the XRD analysis and Rietveld refinement of CuNbC with S = 1.23, we observed the formation of niobium carbide and metallic copper with cubic structure. For the synthesis of mixed oxide made of niobium and copper, the formation of two distinct phases was observed: CuNb2O6 and Nb2O5, although the latter was present in small amounts / Os carbetos de metais refrat?rios t?m se revelado importantes no desenvolvimento de materiais de engenharia devido as suas propriedades, tais como: alta dureza, alto ponto de fus?o, alta condutividade t?rmica e alta estabilidade qu?mica. O carbeto de ni?bio apresenta essas caracter?sticas. Os compostos de ni?bio impregnados com cobre tamb?m possuem excelentes propriedades diel?tricas e magn?ticas e, al?m disso, a dopagem com Cu aumenta a atividade catal?tica em processos de oxida??o de hidrog?nio. Este trabalho teve como objetivo a s?ntese dos materiais CuNbC e ?xido de ni?bio e cobre nanoestruturados a partir do precursor tris(oxalato)oxiniobato de am?nio hidratado, atrav?s de rea??o g?s-s?lido e s?lido-s?lido, respectivamente. Para ambos, as rea??es foram realizadas a baixa temperatura (1000?C) e curto tempo de rea??o (2 horas). O carbeto de ni?bio foi produzido com 5% e 11% de cobre e o ?xido de ni?bio e cobre com 5% de cobre. Os materiais obtidos foram caracterizados atrav?s dos ensaios de Difra??o de Raios X (DRX), Refinamento Rietveld, Microscopia Eletr?nica de Varredura (MEV), Espectroscopia por Fluoresc?ncia de Raios-X (FRX), Espectroscopia de Infravermelho (IV), Termogravim?trica (TG), An?lise Termodiferencial (DTA), BET e granulometria a Laser. A partir das an?lises de DRX e do refinamento Reitiveld para o CuNbC com S= 1,23, observou-se a forma??o do carbeto de ni?bio e cobre puro com estrutura c?bica. Na s?ntese realizada do ?xido misto de ni?bio e cobre correu a forma??o de duas fases distintas: CuNb2O6 e Nb2O5, embora a ?ltima tenha sido formada em pequena quantidade / 2020-01-01