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Resumen es: Se ha estudiado un nanocomposito preparado a partir de beta ciclodextrina y magnetita, mediante tecnicas de susceptibilidad magnetica dinamica a frecue...
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The adverse environmental effects of petroleum-based packaging plastics have necessitated the need for eco-friendly bioplastics. Most bioplastics are starch-based and are not without drawbacks, hence there is the need for their properties... more
The adverse environmental effects of petroleum-based packaging plastics have necessitated the need for eco-friendly bioplastics. Most bioplastics are starch-based and are not without drawbacks, hence there is the need for their properties to be improved. In this study, the effect of varying concentrations of dialdehyde starch and silica solutions on the physical, mechanical, biodegradable, surface topology, and thermal properties of the bioplastic films was examined. The additive concentrations were varied from 60 to 100%. The bioplastic films produced with dialdehyde starch solution recorded better moisture content (6.62–11.85%), bioplastic film solubility (4.23–7.90%), and tensile strength (1.63–3.06 MPa), against (11.24–14.26%), (7.77–19.27%) and (0.53–0.73 MPa) respectively for bioplastic films produced with silica solution. The atomic force microscopy analysis; root-mean-square roughness, kurtosis, and skewness revealed better miscibility and compatibility between the starch ma...
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Conversores catalíticos ou catalisadores automotivos são formados por metais nobres como platina, paládio, ródio e molibdênio, suportados em filmes de alumina depositados em cordierita, um material cerâmico poroso, os quais convertem... more
Conversores catalíticos ou catalisadores automotivos são formados por metais nobres como platina, paládio, ródio e molibdênio, suportados em filmes de alumina depositados em cordierita, um material cerâmico poroso, os quais convertem gases poluentes em dióxido de carbono, água e nitrogênio, produtos não poluentes. Neste trabalho, é discutida a desativação de catalisadores automotivos devido às altas temperaturas de operação e por contaminação inorgânica originária dos combustíveis e óleos utilizados. Catalisadores novos e usados foram analisados por adsorção gasosa, picnometria, difração de raios X, e microscopia eletrônica de varredura para caracterizações texturais, morfológicas e estruturais. Microssonda eletrônica foi utilizada para detectar a composição dos catalisadores e dos seus contaminantes.
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ABSTRACT The new Microscopy Center at the Federal University of Minas Gerais (UFMG) is presently in the final stages of construction. Here, we will describe the history as well as the technical aspects of this new facility, which will be... more
ABSTRACT The new Microscopy Center at the Federal University of Minas Gerais (UFMG) is presently in the final stages of construction. Here, we will describe the history as well as the technical aspects of this new facility, which will be fully available to the scientific, state and private enterprise communities in 2007. We envision that this multi-user facility will be a place where researchers from material sciences and biomedical areas will share space, microscopes and knowledge. Such cross- discipline interactions should promote a better interface between these diverse areas and enhance the growth of emerging areas such as nanotechnology and bioengineering.
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OBJETIVO: o presente trabalho teve como finalidade avaliar clinicamente uma nova alternativa mecânica para a erupção guiada ao plano oclusal de um dente pré-molar impactado empregando magnetos atrativos da liga samário-cobalto.... more
OBJETIVO: o presente trabalho teve como finalidade avaliar clinicamente uma nova alternativa mecânica para a erupção guiada ao plano oclusal de um dente pré-molar impactado empregando magnetos atrativos da liga samário-cobalto. METODOLOGIA: o tratamento cirúrgico-ortodôntico foi realizado em uma paciente jovem de 11 anos portadora de oclusão de Classe I de Angle, com impactação do segundo pré-molar inferior direito. O sistema magnético empregado consistiu de um magneto colado com resina fotopolimerizável sobre a superfície vestibular do dente impactado e um outro pólo magnético rígido incrustado em um aparelho banda alça. Previamente à instalação do sistema magnético no meio bucal, os magnetos foram caracterizados através de análise de fluorescência, difração de raios X e nível de magnetização. A relação força/distância empregada foi quantificada, os magnetos foram medidos e a geometria magnética bucal estabelecida. RESULTADOS: o tempo empregado na desimpactação foi de 40 dias e for...
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ABSTRACT Alumina nanotube was synthesized by hydrolysis of aluminum isopropoxide followed by gelation and drying under hypercritical condition. The influence of temperature on the structural, textural, and morphological properties of the... more
ABSTRACT Alumina nanotube was synthesized by hydrolysis of aluminum isopropoxide followed by gelation and drying under hypercritical condition. The influence of temperature on the structural, textural, and morphological properties of the material was studied by powder X-ray diffraction, infrared spectroscopy, nitrogen adsorption, thermal analysis, scanning and transmission electronic microscopy. The as-prepared alumina (300°C) was formed by boehmite crystallites. Its structure collapsed after heating (500–1200 °C) yielding γ, δ and θ alumina nanophases. The aerogel surface area changed from 254 to 99m2g−1 in this heating range. The formation of alumina nanotubes was verified by transmission microscopy analysis at the heating range.
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Organic–inorganic magnetic hybrid materials (MHMs) combine a nonmagnetic and a magnetic component by means of electrostatic interactions or covalent bonds, and notable features can be achieved. Herein, we describe an application of a... more
Organic–inorganic magnetic hybrid materials (MHMs) combine a nonmagnetic and a magnetic component by means of electrostatic interactions or covalent bonds, and notable features can be achieved. Herein, we describe an application of a self-assembled material based on ferrite associated with β-cyclodextrin (Fe-Ni/Zn/βCD) at the nanoscale level. This MHM and pure ferrite (Fe-Ni/Zn) were used as an adsorbent system for Cr3+ and Cr2O72− ions in aqueous solutions. Prior to the adsorption studies, both ferrites were characterized in order to determine the particle size distribution, morphology and available binding sites on the surface of the materials. Microscopy analysis demonstrated that both ferrites present two different size domains, at the micro- and nanoscale level, with the latter being able to self-assemble into larger particles. Fe-Ni/Zn/βCD presented smaller particles and a more homogeneous particle size distribution. Higher porosity for this MHM compared to Fe-Ni/Zn was observ...
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ABSTRACT Hexagonal barium titanate (HBT) thin films were prepared on borosilicate plate substrates via sol–gel method using the dip-coating process. The structure, texture and morphology of the thin film were analyzed by X-ray... more
ABSTRACT Hexagonal barium titanate (HBT) thin films were prepared on borosilicate plate substrates via sol–gel method using the dip-coating process. The structure, texture and morphology of the thin film were analyzed by X-ray diffraction, atomic force microscopy, nanoindentation technique, and transmission electron microscopy. The results showed that the thin film annealed at 700 °C crystallized with BaTiO3 hexagonal phase and traces of Ba2TiO4 (secondary phase). The nanoparticles and the RMS roughness of the sample treated at 700 °C presented high values when compared with those thermally treated at lower temperatures. The hardness and Youngs’ modulus of the thin films increased with increasing in grain size, and the thin film annealed at 700 °C with crystallite size about 10 nm presented multiple “pop-in” events during nano-indentation loading curves. The annealing temperature, growth size and surface roughness were discussed in connection with the HBT mechanical properties.
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γ-LiAlO2 plate-like nanostructures have been synthesized by lyophilization of a gel precursor prepared by coprecipitation process. Aqueous solutions of Al(NO3)3.9H2O and LiNO3 were used as precursors, and NaOH was used as precipitant... more
γ-LiAlO2 plate-like nanostructures have been synthesized by lyophilization of a gel precursor prepared by coprecipitation process. Aqueous solutions of Al(NO3)3.9H2O and LiNO3 were used as precursors, and NaOH was used as precipitant agent. After freeze-drying, the samples were calcined at several temperatures for characterization. The lyophilization process allowed the preparation of γ-LiAlO2 phase at 750 °C, which remained stable until temperatures about 1150 oC, without the formation of other undesired phases as LiAl5O8. Copyright © 2016 VBRI Press.
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The global production capacity of corrugated cardboard used in packaging increased by 3.5% per year in the last decade. These packages have limited life span and, after use, contribute for increasing the waste stream on the planet. An... more
The global production capacity of corrugated cardboard used in packaging increased by 3.5% per year in the last decade. These packages have limited life span and, after use, contribute for increasing the waste stream on the planet. An interesting alternative for their reuse is the manufacture of unconventional furniture and objects. Nevertheless, there are few studies addressing the performance of cardboard for their application in furniture products. In this study we characterized corrugated cardboard by scanning electron microscopy, energy dispersive spectroscopy. X-ray diffraction, determination of the basic weight of paper (grammage), resistance to burst, column compression and uniaxial compression of test samples manufactured with a specific geometry. Results indicate that cardboard can be a material of great feasibility and workability to be used in furniture design.
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Different studies investigate the use of waste glass in Portland cement compounds, either as aggregates or as supplementary cementitious materials. Nevertheless, it seems that there is no consensus about the influence of particle color... more
Different studies investigate the use of waste glass in Portland cement compounds, either as aggregates or as supplementary cementitious materials. Nevertheless, it seems that there is no consensus about the influence of particle color and size on the behavior of the compounds. This study addresses the influence of cement replacement by 10 and 20% of the colorless and amber soda-lime glass particles sized around 9.5 μm on the performance of Portland cement mortars. Results revealed that the partial replacement of cement could contribute to the production of durable mortars in relation to the inhibition of the alkali-aggregate reaction. This effect was more marked with 20% replacement using amber glass. Samples containing glass microparticles were more resistant to corrosion, in particular those made of colorless glass. The use of colorless and amber glass microparticles promoted a reduction in wear resistance.
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Aluminato de lítio (LiAlO2) foi sintetizado por coprecipitação. O material foi calcinado em diferentes temperaturas e caracterizado por difração de raios X, espectroscopia na região do infravermelho com transformada de Fourier, adsorção... more
Aluminato de lítio (LiAlO2) foi sintetizado por coprecipitação. O material foi calcinado em diferentes temperaturas e caracterizado por difração de raios X, espectroscopia na região do infravermelho com transformada de Fourier, adsorção gasosa, microscopia eletrônica de varredura (MEV) e microscopia eletrônica de transmissão (MET), possibilitando sua caracterização estrutural, morfológica e textural. Diferentes fases cristalinas foram observadas à medida que a temperatura foi elevada de 550 para 1150 ºC. Texturalmente o material foi classificado como não-poroso e particulado a 550 e 750 ºC, apresentando microporos a 950 ºC. Análises comparativas de imagens de MET e MEV possibilitaram a identificação nanoflocos e microfolhas como as principais morfologias presentes no material.
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As células a combustível de óxido sólido (SOFC) são dispositivos capazes de gerar energia elétrica com alta eficiência e baixa emissão de poluentes. As altas temperaturas de operação dessas células (600 a 1000 °C) são benéficas no sentido... more
As células a combustível de óxido sólido (SOFC) são dispositivos capazes de gerar energia elétrica com alta eficiência e baixa emissão de poluentes. As altas temperaturas de operação dessas células (600 a 1000 °C) são benéficas no sentido de possibilitar a reforma in situ do combustível utilizado, bem como sua aplicação em sistemas de co-geração de energia, aumentando sua eficiência teórica total que pode chegar entre 80 e 85%. Entretanto, essas altas temperaturas, o contato direto entre materiais de constituições químicas diferentes e a utilização de gases redutores e oxidantes, são alguns dos fatores que impõem severas restrições aos materiais usados na preparação de seus principais componentes. O presente artigo tem como objetivo revisar o desenvolvimento do estado da arte, com relação aos materiais de ânodo, cátodo, eletrólito, interconectores e selantes, usados em SOFCs. Os requisitos necessários para o bom funcionamento de cada componente e os materiais que melhor se adequam a...
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Research Interests: Engineering and Cardboard
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Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Sintering, Microstructure, and 15 moreMagnetic Materials, Scanning Electron Microscopy, Powder Diffraction, Ceramics, Porosity, Grain Growth, Cooling Rate, Chemical Analysis, Ceramic, Scanning Electron Microscope, Microstructures, Qualitative Modeling, Physics Chemistry, Energy Dispersive Spectrometry, and High density
In this work we have explained the diffuse phase transitions (PT) of sol-gel grown Barium Titanate samples through a model where weighted sums of “normal” PT from micro-regions of the material are performed. Using... more
In this work we have explained the diffuse phase transitions (PT) of sol-gel grown Barium Titanate samples through a model where weighted sums of “normal” PT from micro-regions of the material are performed. Using Landau-Devonshire's expressions for ferroelectric transitions, we obtain the smeared macroscopic behaviour of the PT. The results are used to show why deviations from Curie-Weiss, and also Smolensky-Isupov, behaviours of the dielectric permittivity are very often found in ferroelectric relaxors.
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Research Interests: Materials Engineering, Condensed Matter Physics, Materials Science, Spectroscopy, Copper, and 14 moreSol Gel Process, Silica, Nanocomposite, Pore Size, Nitrogen, Composite Material, Silica Gel, X ray diffraction, Dopant, Sol gel, Sol Gel Method, Gel Growth, Positron Annihilation Spectroscopy, and pore structure
Research Interests: Engineering, Materials Science, Ultrasound, Polymer, Differential scanning calorimetry, and 13 moreTheoretical Morphology (in Biology), Physical sciences, Polymer Electrolyte, Conductivity, CHEMICAL SCIENCES, Glass Transition, Ionic Conductivity, Room Temperature, Propylene Glycol, Electrolyte, Ethylene Glycol, thermal behaviour, and ionic bonding
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Magnetic nanocomposite thin films formed by cobalt ferrite dispersed in silica matrix were prepared by sol-gel process using tetraethylorthosilicate (TEOS) as a precursor of silica, and metallic nitrates as precursors of the ferrite. The... more
Magnetic nanocomposite thin films formed by cobalt ferrite dispersed in silica matrix were prepared by sol-gel process using tetraethylorthosilicate (TEOS) as a precursor of silica, and metallic nitrates as precursors of the ferrite. The films were prepared with 5–50 wt. % ferrite contents and deposited on substrate using the dip-coating process. The films obtained were adherent, transparent, homogeneous and free of microcracks, with thickness between 30 and 500 nm. The films obtained presented crystalline CoFe2O4 phases dispersed in SiO2 amorphous matrix and saturation magnetization of approximately 9 emu/g considering the composite mass and 30 emu/g considering the ferrite mass.
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Page 1. Introduction Interest in the preparation of thin films using the solgel process by dip-coating has increased in the last few years. Brinker and Scherer [1] reviewed studies made until 1990. Other authors [2, 3] have reviewed... more
Page 1. Introduction Interest in the preparation of thin films using the solgel process by dip-coating has increased in the last few years. Brinker and Scherer [1] reviewed studies made until 1990. Other authors [2, 3] have reviewed relevant results published after that. ...