Made available in DSpace on 2014-12-17T14:07:02Z (GMT). No. of bitstreams: 1 DarciaSSMM_DISSERT.pdf: 2144091 bytes, checksum: 373e58cf1ee08b2c45a550ad627238d6 (MD5) Previous issue date: 2012-04-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present work has as objective the development of ceramic pigments based in iron oxides and cobalt through the polymeric precursor method, as well as study their characteristics and properties using methods of physical, chemical, morphological and optical characterizations.In this work was used iron nitrate, and cobalt citrate as precursor and nanometer silica as a matrix. The synthesis was based on dissolving the citric acid as complexing agent, addition of metal oxides, such as chromophores ions and polymerization with ethylene glycol. The powder obtained has undergone pre-ignition, breakdown and thermal treatments at different calcination temperatures (700 ?C, 800 ?C, 900 ?C, 1000 ?C and 1100 ?C). Thermogravimetric analyzes were performed (BT) and Differential Thermal Analysis (DTA), in order to evaluate the term decomposition of samples, beyond characterization by techniques such as BET, which classified as microporous materials samples calcined at 700 ? C, 800 ? C and 900 ? C and non-porous when annealed at 1000 ? C and 1100 ? C, X-ray diffraction (XRD), which identified the formation of two crystalline phases, the Cobalt Ferrite (CoFe2O4) and Cristobalite (SiO2), Scanning Electron Microscopy (SEM) revealed the formation of agglomerates of particles slightly rounded;and Analysis of Colorimetry, temperature of 700 ?C, 800 ?C and 900 ?C showed a brown color and 1000 ?C and 1100 ?C violet / O presente trabalho tem como objetivo o desenvolvimento de pigmentos cer?micos a base de ?xidos de ferro e cobalto atrav?s do m?todo dos precursores polim?ricos, bem como o estudo de suas caracter?sticas e propriedades atrav?s de m?todos de caracteriza??es f?sicas, qu?micas, morfol?gicas e ?pticas. Neste trabalho foi utilizado nitrato de ferro e citrato de cobalto como precursores e s?lica nanom?trica como matriz. A s?ntese foi baseada na dissolu??o do ?cido c?trico, como agente complexante; adi??o dos ?xidos met?licos, como ?ons crom?foros e polimeriza??o com etileno glicol. O P? obtido passou por pr?-calcina??o, desagrega??o e tratamentos t?rmicos em diferentes temperaturas de calcina??o (700 ?C, 800 ?C, 900 ?C, 1000 ?C e 1100 ?C). Foram feitas An?lises de Termogravimetria (TG) e An?lise T?rmica Diferencial (DTA), a fim de se avaliar a termodecomposi??o das amostras, al?m de caracteriza??es por t?cnicas como BET, que classificou como materiais microporosos as amostras calcinadas a 700 ?C, 800 ?C e 900 ?C e n?o porosos quando calcinados a 1000 ?C e 1100 ?C; Difra??o de Raios-X (DRX), que identificou a forma??o de duas fases cristalinas, a Ferrita de Cobalto (CoFe2O4) e a Cristobalita (SiO2); Microscopia Eletr?nica de Varredura (MEV), que revelou a forma??o de aglomerados de part?culas ligeiramente arredondadas; e an?lise de colorimetria na regi?o do UV-Vis?vel, verificando a varia??o e o potencial de cromaticidade do pigmento que a temperaturas de 700 ?C, 800 ?C e 900 ?C apresentou a cor marrom e a 1000 ?C e 1100 ?C a cor violeta

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-06-13T18:57:01Z No. of bitstreams: 1 RaquelGuilhermeDeCarvalho_TESE.pdf: 2127311 bytes, checksum: dad2b807e182cde2957844b6d86756bd (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-06-14T19:13:58Z (GMT) No. of bitstreams: 1 RaquelGuilhermeDeCarvalho_TESE.pdf: 2127311 bytes, checksum: dad2b807e182cde2957844b6d86756bd (MD5) / Made available in DSpace on 2017-06-14T19:13:58Z (GMT). No. of bitstreams: 1 RaquelGuilhermeDeCarvalho_TESE.pdf: 2127311 bytes, checksum: dad2b807e182cde2957844b6d86756bd (MD5) Previous issue date: 2016-06-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Neste trabalho, foram investigadas o efeito do sam?rio como dopante nas propriedades fotocatal?tica e fotoluminescente do ?xido de zinco obtidas pelas s?nteses hidrotermal por micro-ondas (HM) e precursores polim?ricos. Essa pesquisa foi dividida em duas etapas, primeiro micropart?culas de ZnO:Smx (X= 0, 1, 2, 4 e 8 mol%) foram obtidos pelas s?nteses hidrotermal por micro-ondas (HM) e precursores polim?ricos. Na segunda etapa do trabalho a resina obtida pela s?ntese dos precursores polim?ricos foi utilizada para produzir filmes finos obtidos pelo m?todo spin coating. As t?cnicas de caracteriza??o, an?lises t?rmicas (TG / DSC), difra??o de raios X (DRX), microscopia eletr?nica de varredura (MEV), microscopia eletr?nica de varredura com emiss?o de campo (MEV-FEG), espectroscopia na regi?o do UV-Vis?vel (UV-Vis), medidas de fotoluminesc?ncia (FL) e an?lise da ?rea superficial espec?fica pelo m?todo de BET foram utilizadas na caracteriza??o dos p?s e dos filmes. Pela an?lise de difra??o de raios X (DRX), as amostras obtidas pela s?ntese hidrotermal por micro-ondas apresenta fase de ZnO com estrutura tipo wurtzita hexagonal sem nenhuma fase secund?ria. As amostras obtidas pela s?ntese dos precursores polim?ricos apresentaram fases secund?rias com a presen?a do Sm2O3, quando dopadas com 2 e 4 mol% de Sam?rio. As imagens por microscopia eletr?nica de varredura das amostras obtidas pela s?ntese hidrotermal por micro-ondas mostram a morfologia em forma de bast?es com as extremidades hexagonais. O desempenho fotocatal?tico das amostras dos p?s e filmes finos foram testados utilizando o corante azul de metileno, e caracterizado por espectroscopia na regi?o do UV-vis. As medidas do espectro de azul de metileno ap?s os testes de fotodegrada??o exibiu melhor atividade fotocatal?tica das micropart?culas de ZnO dopado com 8 mol% de Sm3+, sendo alcan?ada a maior taxa de degrada??o do corante no tempo de 120 minutos. As amostras foram tamb?m reutilizadas em tr?s ciclos de fotodegrada??o, as amostras com 2, 4 e 8 mol% de Sm3+ apresentaram efici?ncia fotocatal?tica mesmo quando reutilizado ap?s os ciclos de fotodegrada??o. / In this work, the effect of samarium as a dopant on the photocatalytic and photoluminescent properties of zinc oxide obtained by hydrothermal (HM) synthesis and polymer precursors were investigated. ZnO:Smx microparticles (X = 0, 1, 2, 4 and 8 mol%) were obtained by microwave hydrothermal (HM) syntheses and polymer precursors. In the second step of the work the resin obtained by the synthesis of the polymeric precursors was used to produce thin films obtained by the spin coating method. The techniques of characterization, thermal analysis (TG / DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), scanning electron microscopy with field emission (SEM-FEG), UV-Visible spectroscopy (UV-Vis), photoluminescence (FL) measurements and analysis of the specific surface area by the BET method were used in the characterization of the powders and films. By the analysis of X-ray diffraction (XRD), the samples obtained by microwave hydrothermal synthesis present a ZnO phase with hexagonal wurtzite structure with no secondary phase. Samples obtained by the synthesis of polymer precursors showed secondary phases with the presence of Sm2O3, when doped with 2 and 4 mol% Samarium. Scanning electron microscopy images of samples obtained by hydrothermal microwave synthesis show the morphology in the form of rods with hexagonal ends. The photocatalytic performance of the samples of the powders and thin films were tested using the methylene blue dye, and characterized by spectroscopy in the UV-vis region. Measurements of the methylene blue spectrum after the photodegradation tests showed better photocatalytic activity of the ZnO microparticles doped with 8 mol% Sm3+, with the highest rate of degradation of the dye in the time of 120 minutes. Samples were also reused in three cycles of photodegradation, samples with 2, 4 and 8 mol% Sm3+ showed photocatalytic efficiency even when reused after the photodegradation cycles.

Made available in DSpace on 2014-12-17T14:07:12Z (GMT). No. of bitstreams: 1 RaimisonBA_DISSERT.pdf: 2147079 bytes, checksum: db6881c15458f1e487de74465b7088a0 (MD5) Previous issue date: 2013-07-04 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Magnetic ceramics have been widely investigated, especially with respect to intrinsic and extrinsic characteristics of these materials. Among the magnetic ceramic materials of technological interest, there are the ferrites. On the other hand, the thermal treatment of ceramic materials by microwave energy has offered various advantages such as: optimization of production processes, high heat control, low consumption of time and energy among others. In this work were synthesized powders of Ni-Zn ferrite with compositions Ni1- xZnxFe2O4 (0.25 ≤ x ≤ 0.75 mols) by the polymeric precursor route in two heat treatment conditions, conventional oven and microwave energy at 500, 650, 800 and 950?C and its structural, and morphological imaging. The materials were characterized by thermal analysis (TG/ DSC), X-ray diffraction (XRD), absorption spectroscopy in the infrared (FTIR), scanning electron microscopy (SEM), X-ray spectroscopy and energy dispersive (EDS) and vibrating sample magnetometry (VSM). The results of X-ray diffraction confirmed the formation of ferrite with spinel-type cubic structure. The extrinsic characteristics of the powders obtained by microwave calcination and influence significantly the magnetic behavior of ferrites, showing particles ferrimagn?ticas characterized as soft magnetic materials (soft), is of great technological interest. The results obtained led the potential application of microwave energy for calcining powders of Ni-Zn ferrite / Cer?micas magn?ticas t?m sido amplamente investigadas, principalmente com rela??o as caracter?sticas intr?nsecas e extr?nsecas destes materiais. Dentre os materiais cer?micos magn?ticos de interesse tecnol?gico, destacam-se as ferritas. Por outro lado, o tratamento t?rmico de materiais cer?micos por energia de microondas tem oferecido diversas vantagens, tais como: otimiza??o dos processos de obten??o, alto controle de aquecimento, menor consumo de tempo e energia entre outras. Neste trabalho, foram sintetizados p?s de ferritas Ni-Zn com composi??es Ni1-xZnxFe2O4 (0,25 ≤ x ≤ 0,75 mols) pela rota dos precursores polim?ricos em duas condi??es de tratamento t?rmico, em forno convencional e por energia de microondas a 500, 650, 800 e 950?C, e sua caracteriza??o estrutural, morfol?gica e magn?tica. Os materiais obtidos foram caracterizados por an?lises t?rmicas (TG/DSC), difra??o de raios x (DRX), espectroscopia de absor??o na regi?o do infravermelho (FTIR), microscopia eletr?nica de varredura (MEV), espectroscopia de raios X por dispers?o de energia (EDS) e magnetometria de amostra vibrante (VSM). Os resultados da difra??o de raios X confirmaram a forma??o da ferrita com estrutura c?bica do tipo espin?lio. As caracter?sticas extr?nsecas dos p?s obtidos e a calcina??o por microondas influenciaram de forma significativa o comportamento magn?tico das ferritas, apresentando part?culas ferrimagn?ticas, caracterizadas como materiais magn?ticos moles (macias), sendo de grande interesse tecnol?gico. Os resultados obtidos induziram o potencial de aplica??o de energia de microondas para a calcina??o de p?s de ferritas Ni-Zn

Made available in DSpace on 2014-12-17T14:58:06Z (GMT). No. of bitstreams: 1 EverlaniaMS_DISSERT.pdf: 3651916 bytes, checksum: 47bd28b5197e92c8cda3dddf63274b6d (MD5) Previous issue date: 2011-02-08 / Considering the constant evolution of technology in growth and the need for production techniques in the ceramics area to move forward together, we sought in this study, the research and development of polymeric precursor method to obtain inorganic ceramic pigments. Method that provides quality to obtain the precursor powders of oxides and pigments at the same time, offers time and cost advantages, such as reproducibility, purity and low temperature heat treatment, control of stoichiometry. This work used chromium nitrate and iron nitrate as precursors. The synthesis is based on the dissolution of citric acid as a complexing agent, addition of metal oxides, such as ion chromophores; polymerization with ethylene glycol and doping with titanium oxide. Passing through precalcination, breakdown, thermal treatments at different temperatures of calcination (700 to 1100 oC), resulting in pigments: green for chromium oxide deposited on TiO2 (CrTiO3) and orange for iron oxide deposited on TiO2 ( FeTiO3). Noticing an increase of opacity with increasing temperature. Were performed thermal analysis (TG and ATD) in order to evaluate its thermodecomposition. The powders were also characterized by techniques such as XRD, revealing the formation of crystalline phases such as iron titanate (FeTiO3) and chrome titanate (CrTiO3), SEM, demonstrating formation of rounded particles for both oxides and Spectroscopy in the UV-Visible Region, verifying the potential variation and chromaticity os pigments. Thus, the synthesized oxides were within the requirements to be applied as pigments and shown to be possible to propose its use in ceramic materials / Considerando a evolu??o tecnol?gica em constante crescimento e a necessidade de t?cnicas de produ??o na ?rea de cer?mica que avancem em conjunto, buscou-se neste estudo, a pesquisa e desenvolvimento do m?todo dos precursores polim?ricos para obten??o de pigmentos cer?micos inorg?nicos. M?todo que proporciona qualidade a obten??o dos p?s precursores dos ?xidos pigmentantes e ao mesmo tempo, oferece vantagens de tempo e custo, como: reprodutibilidade, pureza, baixas temperaturas de tratamento t?rmico e controle de estequiometria. Neste trabalho foram utilizados nitrato de cromo e nitrato de ferro, como precursores. A s?ntese foi baseada na dissolu??o do ?cido c?trico, como agente complexante; adi??o dos ?xidos met?licos, como ?ons crom?foros; polimeriza??o com etileno glicol e dopagem com ?xido de tit?nio. Passando por pr?-calcina??o, desagrega??o, tratamentos t?rmicos em diferentes temperaturas de calcina??o (700 a 1100 oC), resultando em pigmentos: verde para o ?oxido de cromo depositado sobre TiO2 (CrTiO3) e laranja para o ? Oxido de Ferro depositado sobre TiO2 (FeTiO3). Percebendo-se aumento de sua opacidade com o aumento da temperatura. Foram feitas an?lises t?rmicas (TG e ATD), a fim de avaliar sua termo de composi??o. Os p?s foram caracterizados tamb?m por t?cnicas como DRX, revelando-se a forma??o de fases cristalinas como Titanato de Ferro (FeTiO3) e Titanato de Cromo (CrTiO3); MEV, evidenciando-se forma??o de aglomerados de part?culas ligeiramente hexagonais para ambos os ?oxidos e Espectroscopia na Regi?o do UV-Vis?vel, verificando a varia??o e o potencial de cromaticidade dos pigmentos. Desta forma, os ?xidos sintetizados apresentaram-se dentro dos requisitos necess?rios para serem aplicados como pigmentos e mostra-se poss?vel propor sua utiliza??o em materiais cer?micos

Made available in DSpace on 2014-12-17T15:42:31Z (GMT). No. of bitstreams: 1 AnneMichelleGPS.pdf: 4577671 bytes, checksum: 19f54b9da1543ee4a1008ce93d607ec1 (MD5) Previous issue date: 2007-10-04 / Bifunctional catalysts based on zircon oxide modified by tungsten (W = 10, 15 and 20 %) and by molybdenum oxide (Mo= 10, 15 e 20 %) containg platinum (Pt = 1%) were prepared by the polymeric precursor method. For comparison, catalysts the tungsten base was also prepared by the impregnation method. After calcinations at 600, 700 and 800 ?C, the catalysts were characterized by X-ray diffraction, fourier-transform infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption and scanning electron microscopy. The profile of metals reduction was determined by temperature programmed reduction. The synthesized catalysts were tested in n-heptane isomerization. X-ray diffractogram of the Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts revealed the presence of tetragonal ZrO2 and platinum metallic phases in all calcined samples. Diffraction peaks due WO3 and ZrO2 monoclinic also were observed in some samples of the Pt/WOx-ZrO2 catalysts. In the Pt/MoOx-ZrO2 catalysts also were observed diffraction peaks due ZrO2 monoclinic and Zr(MoO4)2 oxide. These phases contained on Pt/WOx-ZrO2 and Pt/MoOx-ZrO2 catalysts varied in accordance with the W or Mo loading and in accordance with the calcination temperature. The infrared spectra showed absorption bands due O-W-O and W=O bonds in the Pt/WOx-ZrO2 catalysts and due O-Mo-O, Mo=O and Mo-O bonds in the Pt/MoOx-ZrO2 catalysts. Specific surface area for Pt/WOx-ZrO2 catalysts varied from 30-160 m2 g-1 and for the Pt/MoOx-ZrO2 catalysts varied from 10-120 m2 g-1. The metals loading (W or Mo) and the calcination temperature influence directly in the specific surface area of the samples. The reduction profile of Pt/WOx-ZrO2 catalysts showed two peaks at lower temperatures, which are attributed to platinum reduction. The reduction of WOx species was evidenced by two reduction peak at high temperatures. In the case of Pt/MoOx-ZrO2 catalysts, the reduction profile showed three reduction events, which are attributed to reduction of MoOx species deposited on the support and in some samples one of the peak is related to the reduction of Zr(MoO4)2 oxide. Pt/WOx-ZrO2 catalysts were active in the n-heptane isomerization with high selectivity to 3-methyl-hexane, 2,3- dimethyl-pentane, 2-methyl-hexane among other branched hydrocarbons. The Pt/MoOx-ZrO2 catalysts practically didn't present activity for the n-heptane isomerization, generating mainly products originating from the catalytic cracking / Catalisadores bifuncionais a base de ?xido de zirc?nio modificado por ?xidos de tungst?nio (W = 10, 15 e 20 %) ou molibd?nio (Mo= 10, 15 e 20 %) contendo platina (Pt = 1 %) foram preparados pelo m?todo dos precursores polim?ricos. Por compara??o, catalisadores a base de tungst?nio tamb?m foram preparados pelo m?todo de impregna??o. Ap?s calcina??es a 600, 700 e 800 ?C, os catalisadores foram caracterizados por difra??o de raios-X, espectroscopia de absor??o na regi?o do infravermelho, an?lise termogravim?trica, an?lise t?rmica diferencial, adsor??o de nitrog?nio e microscopia eletr?nica de varredura. Os perfis de redu??o dos metais foram determinados por redu??o a temperatura programada. Os catalisadores sintetizados foram testados na isomeriza??o do n-heptano. Os difratogramas de raios-X dos catalisadores Pt/WOx-ZrO2 e Pt/MoOx-ZrO2 revelaram a presen?a do ZrO2 tetragonal e da platina met?lica em todas as amostras calcinadas. Picos de difra??o referentes ao WO3 e ao ZrO2 monocl?nico tamb?m foram observados em algumas das amostras dos catalisadores Pt/WOx-ZrO2. Nos catalisadores do tipo Pt/MoOx-ZrO2 tamb?m foram observados picos de difra??o referente ao ZrO2 monocl?nico e ao ?xido Zr(MoO4)2. O aparecimento destas outras fases contidas nos catalisadores Pt/WOx-ZrO2 e Pt/MoOx-ZrO2 variaram de acordo com o teor de W ou Mo e de acordo com a temperatura de calcina??o. Os espectros de absor??o na regi?o do infravermelho exibiram bandas de absor??o referentes as liga??es O-W-O e W=O nos catalisadores Pt/WOx-ZrO2 e referentes as liga??es O-Mo-O, Mo=O e Mo-O nos catalisadores Pt/MoOx-ZrO2. A ?rea superficial espec?fica dos catalisadores Pt/WOx-ZrO2 variou de 30-160 m2 g-1 e para os catalisadores do tipo Pt/MoOx-ZrO2 variou de 10-120 m2 g-1. O teor de metais (W ou Mo) e a temperatura de calcina??o exercem uma influ?ncia direta no valor da ?rea superficial espec?fica das amostras. Os perfis de redu??o dos catalisadores Pt/WOx-ZrO2 exibiram dois picos a baixas temperaturas, os quais s?o atribu?dos a redu??o da platina. A redu??o das esp?cies WOx foi evidenciada por dois picos de redu??o a altas temperaturas. No caso dos catalisadores Pt/MoOx-ZrO2, os perfis de redu??o mostram tr?s eventos de redu??o, os quais s?o atribu?dos a redu??o das esp?cies MoOx depositadas no suporte e em algumas amostras um dos picos ? relacionado com a redu??o do ?xido Zr(MoO4)2. Os catalisadores Pt/WOx-ZrO2 foram ativos para a isomeriza??o do n-heptano com alta seletividade a 3-metil-hexano, 2,3-dimetil-pentano e 2-metil-hexano entre outros hidrocarbonetos ramificados. Os catalisadores Pt/MoOx- ZrO2 praticamente n?o apresentaram atividade para a isomeriza??o do n-heptano, gerando principalmente produtos oriundos do craqueamento catalitico