Made available in DSpace on 2014-12-17T14:58:04Z (GMT). No. of bitstreams: 1 EraldoCS_DISSERT.pdf: 3770041 bytes, checksum: 781cd8af5bcf3a0660e0344b0a08f87a (MD5) Previous issue date: 2010-10-14 / The nanometric powders have special features that usually result in new properties, originating applications or expanding them in various fields of knowledge. Because having a high area/volume ratio, phenomena such as superficial strength of adsorption becomes greater than the weight of the powder which makes more difficult its handling. The high power of agglomeration of these powders requires study and development of equipments to enable its management into the plasma torch. The objective of this work is to develop a powder feeder which can solve the mainly problems about insertion of powder into the thermal spray developed in the laboratory of plasmas, which are carried out with plasma torch arc not transferred (plasma spray). Therefore, it was made a aluminum s powder feeder and tests were performed to verify their operation and determine its rate of deposition by spraying powders of niobium pentoxide (Nb2O5) and titanium dioxide (TiO2) with particle sizes less than 250 mesh (<0.063 mm). We used masses of 0.5 g - 1.0 g and 1.5 g of each powder in tests lasting 15 seconds - 20 to 25 seconds for each mass. The tests were performed in two ways: at atmospheric pressure using argon gas with a flow of 9 l / min as carrier gas and through a Venturi pipe also using argon gas with a flow of 9 l / min as carrier gas and with a flow of 20 l/min as the feed gas passing through the Venturi pipe. The powder feeder developed in this paper is very easy to be handling and building, resulting in feeding rate of 0.25 cm3/min - 1.37 cm3/min. The TiO2 showed higher feeding rates than the Nb2O5 in all tests, and the best rates were obtained with tests using mass 1.5 g and time of 15 seconds, reaching feeding rate of 1.37 cm3/min. The flow of feed had low interference in feeding rate during the tests / Os p?s nanom?tricos apresentam caracter?sticas especiais que geralmente resultam em novas propriedades, ampliando ou originando melhores aplica??es nas diversas ?reas de conhecimento. Devido ao fato de possuir uma alta raz?o ?rea/volume, fen?menos como a for?a de adsor??o de superf?cie tornam-se superiores ao peso, dificultando o seu manuseio. O alto poder de aglomera??o dificulta processos como o de alimenta??o de p?s em tochas de plasma, por exemplo. O objetivo do presente trabalho ? desenvolver um alimentador de p?s, para trabalhos com aspers?o t?rmica, que s?o realizados em tocha de plasma de arco n?o transferido (plasma spray). Para tanto, foi confeccionado um dispositivo em alum?nio, sendo realizados testes para verificar seu funcionamento e determinar sua taxa de alimenta??o durante aspers?o de p?s de pent?xido de ni?bio (Nb2O5) e di?xido de tit?nio (TiO2), com tamanhos de part?culas inferiores a mesh 250 (< 0,063 mm). Foram utilizadas massas de 0,5 g - 1,0 g e 1,5g de cada p?, em testes com dura??o de 15 s - 20 s e 25 segundos para cada massa. Os ensaios foram realizados de duas maneiras: ? press?o atmosf?rica utilizando-se g?s arg?nio com fluxo de 9 l/min como g?s de arraste e atrav?s de um tubo de Venturi utilizando tamb?m o g?s arg?nio com fluxo de 9 l/min como g?s de arraste e com fluxo de 20 l/min como g?s de alimenta??o, passando pelo interior do tubo de Venturi. O alimentador de p? desenvolvido neste trabalho ? de f?cil constru??o e manuseio, obtendo-se taxas de alimenta??o de 0,25 cm3/min - 1,37 cm3/min. O TiO2 apresentou maiores taxas de alimenta??o que o Nb2O5 em todos os testes, e as melhores taxas foram obtidas com os ensaios utilizando massa de 1,5 g e tempo de 15 segundos, atingindo taxa de alimenta??o de 1,37 cm3/min. O fluxo de alimenta??o apresentou pouca interfer?ncia na taxa de alimenta??o durante a realiza??o dos testes

Made available in DSpace on 2014-12-17T15:15:04Z (GMT). No. of bitstreams: 1 AnnaCDM_DISSERT.pdf: 3464816 bytes, checksum: 8d617feb92fa3c439455f7c50d0cdd96 (MD5) Previous issue date: 2014-05-30 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The study and fabrication of nanostructured systems composed of magnetic materials has been an area of great scientific and technological interest. Soft magnetic materials, in particular, have had great importance in the development of magnetic devices. Among such materials we highlight the use of alloys of Ni and Fe, known as Permalloy. We present measurement results of structural characterization and magnetic films in Permalloy (Ni81Fe19), known to be a material with high magnetic permeability, low coercivity and small magneto- crystalline anisotropy, deposited on MgO (100) substrates. The Magnetron Sputtering technique was used to obtain the samples with thicknesses varying between 9 150 nm. The techniques of X- ray Diffraction at high and low angle were employed to confirm the crystallographic orientation and thickness of the films. In order to investigate the magnetic properties of the films the techniques of Vibrant Sample Magnetometry (VSM), Ferromagnetic Resonance (FMR) and Magnetoimpedance were used. The magnetization curves revealed the presence of anisotropy for the films of Py/MgO (100), where it was found that there are three distinct axis - an easy-axis for ?H = 0?, a hard-axis for ?H = 45? and an intermediate for ?H = 90?. The results of the FMR and Magnetoimpedance techniques confirm that there are three distinct axes, that is, there is a type C2 symmetry. Then we propose, for these results, the interpretation of the magnetic anisotropy of Py/MgO ( 100 ) is of type simple C2, ie a cubic magnetic anisotropy type ( 110 ) / O estudo e obten??o de sistemas nanoestruturados compostos por materiais magn?ticos tem se mostrado uma ?rea de grande interesse cient?fico e tecnol?gico. Materiais magn?ticos macios, em especial, tem tido grande import?ncia no desenvolvimento de dispositivos magn?ticos. Entre esses tipos de materiais cabe-nos destacar o uso de ligas de Ni e Fe, conhecidas como Permalloy. Neste trabalho apresentamos resultados de medidas de caracteriza??o estrutural e magn?tica em filmes nanom?tricos de Permalloy (Ni81Fe19), conhecido por ser um material com alta permeabilidade magn?tica, baixa coercividade e pequena anisotropia magneto-cristalina, depositado em substratos de MgO(100). A t?cnica de Magnetron Sputtering foi utilizada na obten??o das amostras com espessuras variando entre 9 150nm. As t?cnicas de Difratometria de Raios-X em alto e baixo ?ngulo foram empregadas para confirmar a orienta??o cristalogr?fica e a espessura dos filmes. Com o intuito de investigar as propriedades magn?ticas dos filmes foram usadas as t?cnicas de Magnetometria de Amostra Vibrante (VSM), Resson?ncia Ferromagn?tica (FMR) e Magnetoimped?ncia. As curvas de magnetiza??o revelaram a presen?a de anisotropia para os filmes de Py/MgO(100), verificando-se a ocorr?ncia de tr?s eixos distintos um eixo-f?cil para ?H=0?, um eixo-duro para ?H=45? e um eixo intermedi?rio para ?H=90?. Os resultados obtidos usando as t?cnicas de FMR e Magnetoimped?ncia confirmaram que h? tamb?m tr?s eixos distintos, isto ?, h? uma simetria tipo C2. Propomos ent?o, para esses resultados, a interpreta??o de que a anisotropia magn?tica do Py/MgO(100) seja do tipo C2 simples, isto ?, uma anisotropia magn?tica c?bica tipo (110)

Made available in DSpace on 2014-12-17T14:07:01Z (GMT). No. of bitstreams: 1 KarlaSMGS_partes_autorizadas_pelo_autor.pdf: 1248832 bytes, checksum: 6139c9f98f965322e719dfe4f7274a99 (MD5) Previous issue date: 2009-03-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The mixed metal oxides constitute an important class of catalytic materials widely investigated in different fields of applications. Studies of rare earth nickelates have been carried by several researchers in order to investigate the structural stability afforded by oxide formed and the existence of catalytic properties at room temperature. So, this study aims synthesize the nanosized catalyst of nickelate of lanthanum doped with strontium (La(1-x)SrxNiO4-d; x = 0,2 and 0,3), through the Pechini method and your characterization for subsequent application in the desulfurization of thiophene reaction. The precursor solutions were calcined at 300?C/2h for pyrolysis of polyester and later calcinations occurred at temperatures of 500 - 1000?C. The resulting powders were characterized by thermogravimetric analysis (TG / DTG), surface area for adsorption of N2 by BET method, X-ray diffraction (XRD), scanning electron microscopy (HR_SEM) and spectrometry dispersive energy (EDS). The results of XRD had show that the perovskites obtained consist of two phases (LSN and NiO) and from 700?C have crystalline structure. The results of SEM evidenced the obtainment of nanometric powders. The results of BET show that the powders have surface area within the range used in catalysis (5-50m2/g). The characterization of active sites was performed by reaction of desulfurization of thiophene at room temperature and 200?C, the relation F/W equal to 0,7 mol h-1mcat -1. The products of the reaction were separated by gas chromatography and identified by the selective detection PFPD sulfur. All samples had presented conversion above 95% / Os ?xidos met?licos mistos constituem uma importante classe de materiais catal?ticos mundialmente investigados em diferentes campos de aplica??es. Estudos envolvendo niquelatos de terras raras v?m sendo realizados por v?rios pesquisadores no intuito de investigar a estabilidade proporcionada pelo ?xido estrutural formado e a exist?ncia de propriedades catal?ticas, ? temperatura ambiente. Neste contexto, este trabalho tem como objetivo a s?ntese do catalisador nanom?trico de niquelato de lant?nio dopado com estr?ncio (La(1-x)SrxNiO4-d; x = 0,2 e 0,3), atrav?s do m?todo Pechini e caracteriza??o para posterior aplica??o em rea??o de dessulfuriza??o de tiofeno. As solu??es precursoras foram calcinadas a 300?C/2h, para pir?lise do poli?ster e posteriores calcina??es foram realizadas nas temperaturas entre 500 - 1000?C. Os p?s resultantes foram caracterizados por an?lise termogravim?trica (TG/DTG), ?rea superficial por adsor??o de N2 pelo m?todo BET, difra??o de raios x (DRX), microscopia eletr?nica de varredura de alta resolu??o (HR_MEV) e espectroscopia por energia dispersiva (EDS). Com os dados de an?lise t?rmica, foi poss?vel definir as temperaturas e calores envolvidos no processo de decomposi??o dos ?xidos finais. Os resultados de DRX mostraram que as perovisquitas obtidas s?o constitu?das de duas fases (LSN e NiO) e a partir de 700?C apresentaram estrutura cristalina. Os resultados de MEV evidenciaram a obten??o de p?s nanom?tricos. Os resultados de BET mostraram que os p?s obtidos apresentam ?rea superficial dentro da faixa utilizada em cat?lise (5-50m2/g). A caracteriza??o dos s?tios ativos foi realizada atrav?s da rea??o de dessulfuriza??o de tiofeno ? temperatura ambiente e a 200oC, com raz?o F/W igual a 0,7molh-1mcat -1. Os produtos da rea??o foram separados por cromatografia em fase gasosa e identificados por detec??o PFPD seletivo a enxofre. Todas as amostras apresentaram convers?o acima de 95%