Obtenção de nanofibras de carbono a partir do processo de eletrofiação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Comportamento do carbono orgânico e de atributos químicos, físicos e microbiológicos de um solo arenoso em área de conversão pastagem - Eucalipto

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nanopartículas de Pd suportadas em compósitos óxido-carbono: influência das interações metal-suporte na oxidação de etanol em meio básico

Fuel cells powered directly with ethanol (Direct Ethanol Fuel Cell-DEFC) are very attractive for the possibility of using a renewable fuel in the generation of clean energy. However, it is still necessary to deepen the understanding of catalytic processes and their dependence on the catalytic properties. This work proposes to study the catalytic activity of ethanol oxidation in an alkaline medium of Pd nanoparticles supported in carbon oxide hybrids using various transition metal oxides (MoO3, TiO2, WO3 and ZrO2). The materials prepared were characterized by techniques such as X-ray diffraction, transmission electron microscopy (TEM) and X-ray dispersive spectroscopy (EDX) to verify the structure, the distribution of particles in the supports and the presence of Pd on particles oxide. Experiments of X-rays absorption spectroscopy were carried out using soft X-rays (SXS) to evaluate the changes in the electronic properties of the Pd particles caused by interactions with different oxides. Measurements of cyclic voltammetry and potential sweeps of adsorbed CO oxidation allowed evaluating general aspects of the catalysts' electrochemical behavior and determining the electrochemically active area thereof. The catalytic performances of ethanol oxidation in alkaline medium were evaluated by electrochemical techniques (potential scan and chronoamperometry), and showed an improvement in activity with the addition of oxides in material containing only carbon, which was most pronounced for the catalyst containing TiO2. This improvement was predominantly associated with the electronic effects caused by the interaction of Pd on the support, causing a vacancy in the 4d band of Pd which, in turn, produces variations in adsorption energies of the species...

Influência da incorporação de nanofibras de poliamida 6 com e sem nanotubos de carbono como reforço de prótese parcial fixa adesiva

The aim of this study was to evaluate the behavior of reinforced composites with polyamide 6 fibers aligned (6000 rpm) and alignment (120 rpm) with or without CNT using the flexural strength test. After preparation of nanofibers aligned nylon 6 (6000 rpm) and alignment (120 rpm) with and without incorporation of nanotube carbon by the method of electrospinning, were performed one control group (n = 10) and 4 experimental groups (n = 40) G1: Control (just resin Charisma - Heraeus Kulzer) ;G2 Resin + N6 aligned (6000 rpm) + CNT; G3:Resin + N6 alignment (120 rpm) + CNT; G4: Resin + aligned ( 6000 rpm) N6. G5: Resin + N6 alignment (120 rpm). The fibers were cut to the dimensions of 0,3 x 15 mm and were applied an adhesive at the surface (Single Bond 2) for 5 min and cured. In the matrix, was added resin in the proximal box (Charisma A2, Heraeus Kulzer) and cured for 40 s. (power 1100 mW / cm²). A first layer of resin and on the resin was deposited. The resin layers specimens were light irradiated with three overlapping exposures delivered. For each resin layer were light irradiated for 40 sec. The samples were tested with a cross-speed of 1 mm / min, and a 50 Kgf at Universal testing machine (EMIC mod.DL2000). The Dunnet test showed that only the nanotube group was significantly different from the control group. The ANOVA two-way indicates that the nanotube factor was statistically significant (p < 0.05) and there is no interaction between factors and orientation nanotube. The presence of nanotube showed lower fracture resistance values for aligned and unaligned groups. The results of this study showed that the orientation of the fibers does not influence the strength of composite resins and the incorporation of nylon nanofibers with carbon nanotubes decreased the fracture resistance values. The presence of the fibers has not been able to improve the strength of the material in any of the...

Aplicação de carbono vítreo monolítico para produção de eletrodos a partir da resina furfurílica com diferentes variações de pH

Nowadays, we live in a time of rapid research for technological advances, in a way that this pursuit of new technologies is deeply connected to the diversity of new materials that have been developed by mankind. It deals with issues such as materials with enhanced properties which offer better quality, less cost and high performance, while they are accessible both in their production and moment of operation. In this context, it was required to develop electrodes that were easy to prepare as well as which present high electric conductivity and good mechanic proprieties by using carbonaceous material as basis. For this reason, the best parameters of the furfuryl resin cures were established with different pH variations through viscosimetric measurements and differential scanning calorimetry. By scanning electron microscopy (SEM) was possible to identify an increased porosity in the samples with pH 7 and pH 8, as compared to samples with lower pH content. After carbonization of the material, the characterization of monolithic glassy carbon was held by means of FT-IR techniques, Raman spectroscopy, X-ray diffraction and cyclic voltammetry. The spectra showed that the change in pH does not have significant influence on the crystallographic ordering of the material and its structural characteristics. As for the electrochemical character, the CVM electrodes showed excellent response, with good reversibility and wide potential window. Some voltammetric curve deviations were only observed for the sample with pH 4, which may be related to processing parameters adopted

Retorque de parafusos de pilares protéticos com recobrimento de carbono tipo diamante: uma análise da manutenção do torque após fadiga mecânica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito do filme de carbono DLC aplicado por plasma como recobrimento em Polietileno de Ultra Densidade e Alto Peso Molecular (UHWPE) e planejamento virtual utilizando a técnica de elementos finitos em cirúrgias de próteses totais da ATM

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Nanopartículas de Pd suportadas em compósitos óxido-carbono: influência das interações metal-suporte na oxidação de etanol em meio básico

Fuel cells powered directly with ethanol (Direct Ethanol Fuel Cell-DEFC) are very attractive for the possibility of using a renewable fuel in the generation of clean energy. However, it is still necessary to deepen the understanding of catalytic processes and their dependence on the catalytic properties. This work proposes to study the catalytic activity of ethanol oxidation in an alkaline medium of Pd nanoparticles supported in carbon oxide hybrids using various transition metal oxides (MoO3, TiO2, WO3 and ZrO2). The materials prepared were characterized by techniques such as X-ray diffraction, transmission electron microscopy (TEM) and X-ray dispersive spectroscopy (EDX) to verify the structure, the distribution of particles in the supports and the presence of Pd on particles oxide. Experiments of X-rays absorption spectroscopy were carried out using soft X-rays (SXS) to evaluate the changes in the electronic properties of the Pd particles caused by interactions with different oxides. Measurements of cyclic voltammetry and potential sweeps of adsorbed CO oxidation allowed evaluating general aspects of the catalysts' electrochemical behavior and determining the electrochemically active area thereof. The catalytic performances of ethanol oxidation in alkaline medium were evaluated by electrochemical techniques (potential scan and chronoamperometry), and showed an improvement in activity with the addition of oxides in material containing only carbon, which was most pronounced for the catalyst containing TiO2. This improvement was predominantly associated with the electronic effects caused by the interaction of Pd on the support, causing a vacancy in the 4d band of Pd which, in turn, produces variations in adsorption energies of the species...

Influência da incorporação de nanofibras de poliamida 6 com e sem nanotubos de carbono como reforço de prótese parcial fixa adesiva

The aim of this study was to evaluate the behavior of reinforced composites with polyamide 6 fibers aligned (6000 rpm) and alignment (120 rpm) with or without CNT using the flexural strength test. After preparation of nanofibers aligned nylon 6 (6000 rpm) and alignment (120 rpm) with and without incorporation of nanotube carbon by the method of electrospinning, were performed one control group (n = 10) and 4 experimental groups (n = 40) G1: Control (just resin Charisma - Heraeus Kulzer) ;G2 Resin + N6 aligned (6000 rpm) + CNT; G3:Resin + N6 alignment (120 rpm) + CNT; G4: Resin + aligned ( 6000 rpm) N6. G5: Resin + N6 alignment (120 rpm). The fibers were cut to the dimensions of 0,3 x 15 mm and were applied an adhesive at the surface (Single Bond 2) for 5 min and cured. In the matrix, was added resin in the proximal box (Charisma A2, Heraeus Kulzer) and cured for 40 s. (power 1100 mW / cm²). A first layer of resin and on the resin was deposited. The resin layers specimens were light irradiated with three overlapping exposures delivered. For each resin layer were light irradiated for 40 sec. The samples were tested with a cross-speed of 1 mm / min, and a 50 Kgf at Universal testing machine (EMIC mod.DL2000). The Dunnet test showed that only the nanotube group was significantly different from the control group. The ANOVA two-way indicates that the nanotube factor was statistically significant (p < 0.05) and there is no interaction between factors and orientation nanotube. The presence of nanotube showed lower fracture resistance values for aligned and unaligned groups. The results of this study showed that the orientation of the fibers does not influence the strength of composite resins and the incorporation of nylon nanofibers with carbon nanotubes decreased the fracture resistance values. The presence of the fibers has not been able to improve the strength of the material in any of the...

Aplicação de carbono vítreo monolítico para produção de eletrodos a partir da resina furfurílica com diferentes variações de pH

Nowadays, we live in a time of rapid research for technological advances, in a way that this pursuit of new technologies is deeply connected to the diversity of new materials that have been developed by mankind. It deals with issues such as materials with enhanced properties which offer better quality, less cost and high performance, while they are accessible both in their production and moment of operation. In this context, it was required to develop electrodes that were easy to prepare as well as which present high electric conductivity and good mechanic proprieties by using carbonaceous material as basis. For this reason, the best parameters of the furfuryl resin cures were established with different pH variations through viscosimetric measurements and differential scanning calorimetry. By scanning electron microscopy (SEM) was possible to identify an increased porosity in the samples with pH 7 and pH 8, as compared to samples with lower pH content. After carbonization of the material, the characterization of monolithic glassy carbon was held by means of FT-IR techniques, Raman spectroscopy, X-ray diffraction and cyclic voltammetry. The spectra showed that the change in pH does not have significant influence on the crystallographic ordering of the material and its structural characteristics. As for the electrochemical character, the CVM electrodes showed excellent response, with good reversibility and wide potential window. Some voltammetric curve deviations were only observed for the sample with pH 4, which may be related to processing parameters adopted

Retorque de parafusos de pilares protéticos com recobrimento de carbono tipo diamante: uma análise da manutenção do torque após fadiga mecânica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito do filme de carbono DLC aplicado por plasma como recobrimento em Polietileno de Ultra Densidade e Alto Peso Molecular (UHWPE) e planejamento virtual utilizando a técnica de elementos finitos em cirúrgias de próteses totais da ATM

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Carbono em agregados do solo sob vegetação nativa, pastagem e sistemas agrícolas no bioma Cerrado

A matéria orgânica do solo (MOS) é responsável pela fertilidade, ciclagem de nutrientes e estabilidade da estrutura, possuindo estreita relação com a agregação do solo. No entanto, ainda não é clara a relação entre as classes de agregados na dinâmica de acúmulo ou perda de MOS em função do uso e manejo do solo. Este trabalho teve como objetivo avaliar os teores de carbono (C) em agregados do solo sob quatro usos e manejos: Cerrado nativo (CE), sistema plantio direto (SPD), sistema plantio convencional (SPC) e pastagem (PA). As áreas de estudo estão localizadas no município de Rio Verde (GO), em solo classificado como Latossolo Vermelho distrófico de textura argilosa. Em amostras de solo coletadas em fevereiro de 2007 nas camadas de 0-5, 5-10 e 10-20 cm de profundidade, foram determinados: a quantidade de macroagregados (maiores que 2,0 mm), mesoagregados (maiores que 0,25 e menores que 2,00 mm) e microagregados (maiores que 0,05 e menores que 0,25 mm) estáveis em água, os índices de agregação diâmetro médio ponderado (DMP) e geométrico (DMG) e os teores de C nas classes de agregados estabelecidas. No solo avaliado observou-se predominância de macroagregados, com maior quantidade sob CE e PA, em comparação ao solo sob SPD e SPC, indicando efeito negativo do cultivo do solo na conservação de macroagregados. Contudo, os teores de C nos agregados do solo na camada de 0-20 cm foram maiores no CE e SPD em relação a PA e SPC, sugerindo que o não revolvimento e a manutenção dos resíduos culturais na superfície do solo favorecem o acúmulo de C. Com isso, foi verificado que os macro e mesoagregados podem ser mais sensíveis ao tipo de uso e manejo do solo, quando comparados aos microagregados. A agregação do solo sob PA é semelhante à do CE, embora com menores teores de C, sugerindo dinâmica de agregação diferenciada, o que merece a atenção de novas pesquisas.

Estoques de carbono e nitrogênio no solo cultivado com mamona na Caatinga

Grande parte da produção brasileira de mamona encontra-se no Nordeste, como opção de cultura para a região semiárida no bioma Caatinga. O objetivo deste estudo foi avaliar as alterações nos estoques de C e N devido à mudança de uso do solo de vegetação natural para o cultivo de mamona no bioma Caatinga. Este trabalho foi realizado na Fazenda Floresta, no município de Irecê, no centro-norte baiano. O clima da região é do tipo BSwh (Köppen) - clima semiárido de altitude. O solo foi classificado em Latossolo Vermelho de textura argilosa. As situações avaliadas foram: três áreas cultivadas com mamona com diferentes tempos de implantação: (i) com 10 anos, (ii) com 20 anos e (iii) com 50 anos; e uma área de referência (vegetação nativa de Caatinga) contígua às situações avaliadas. Os estoques de C e N foram determinados em amostras de solo coletadas em cinco minitrincheiras, nas camadas de 0-5, 5-10, 10-20 e 20-30 cm. Os resultados mostraram que o constante aporte de resíduos vegetais na Caatinga promoveu a manutenção dos estoques de C (90 Mg ha-1) e N (10 Mg ha-1) para a camada de 0-30 cm. A mudança de uso da terra para o cultivo da mamona ocasiona redução em aproximadamente 50 % nos estoques de C e N do solo em relação à vegetação nativa nos primeiros 10 anos de implantação da cultura. A meia-vida da matéria orgânica do solo (MOS) calculada para essa situação na região do semiárido foi de 4,7 anos. O fator de emissão de C do solo, devido à mudança de uso da terra após 20 anos, conforme proposto pelo método do IPCC (2006), foi de 2,47 Mg C ano-1. Por meio do conjunto dos resultados, observa-se a fragilidade do solo do bioma Caatinga no que se refere à perda de MOS devido à mudança de uso da terra.

Citotoxicidade e genotoxicidade de nanotubos de carbono

There are many controversies regarding the cyto- and genotoxicity of carbon nanotubes (CNTs). In this work, we discuss that many of the incongruous arguments are probably associated with the poor physical-chemical characterization of the CNT samples used in many publications. This manuscript presents examples of carbon nanostructures observed under high resolution electron microscopy that can be found in typical CNT samples, and shows which roles in cyto- and genotoxicity need to be better investigated. Issues concerning chemical treatment are addressed and examples of misunderstandings that can occur during the studies of cyto- and genotoxicity of CNT samples are given.