Cellulosic materials have several applications, from rheological modifiers to structural reinforcement and packaging components. Using cellulosic materials may also contribute to environmental sustainability because it can be sourced from agricultural byproducts. In this work, self-sustained composite films were produced by the casting of TEMPO-oxidized cellulose nanofibers/graphite composite dispersions. Oscillatory rheology and tensile strength tests showed that the presence of graphite did not significantly contribute to the enhancement of neither the rheological nor mechanical properties of the dispersions and films. Morphological analysis showed that particle segregation and setting occurred during film casting, resulting in particle concentration gradient along the thickness of the film. These results could indicate the low exfoliation efficiency of the microfluidization process and, therefore, justify why the graphite did not act as a reinforcement of the cellulose matrix. However, the graphite particles contributed to a higher barrier to water vapor permeation of the cellulosic films. applications components byproducts work selfsustained self sustained TEMPOoxidized TEMPO oxidized nanofibersgraphite nanofibers therefore matrix However

Objetivou-se, nesse trabalho, avaliar os briquetes dos resíduos do processamento dos grãos de café submetidos aos processos de carbonização e torrefação. Os briquetes foram carbonizados utilizando-se taxa de aquecimento de 1,67 ºC min-1 com temperatura inicial de 50 ºC e final de 450 ºC, por 30 min. A torrefação dos briquetes foi realizada em uma mufla em duas taxas de aquecimento: 1,5 e 3,0 ºC min-1 até 250 ºC, temperatura mantida durante 60 min. Foram determinados os rendimentos em briquetes torrificados e carbonizados, em líquido pirolenhoso, em gases não condensáveis e em carbono fixo. Para todos os briquetes foram quantificados os teores de carbono fixo, cinzas, voláteis, dos componentes elementares (C, H, N, S, O), o poder calorífico superior, a densidade aparente e energética e a resistência à compressão diametral. Os briquetes carbonizados apresentaram maior potencial energético devido aos elevados teores de carbono fixo e elementar e poder calorífico, porém baixa resistência mecânica. Os briquetes torrificados nas duas taxas de aquecimento consideradas apresentaram características e propriedades energéticas semelhantes mas densidade energética inferior em relação aos briquetes carbonizados e in natura.

This research aimed to evaluate the briquettes made with residues from processing of coffee grain submitted to carbonization and torrefaction. The briquettes were carbonized at a heating rate of 1.67 ºC min-1 with initial temperature of 50 ºC and final of 450 ºC, which was kept during 30 min. The torrefaction of the briquettes was made in a muffle furnace at two heating rates: 1.5 and 3.0 ºC min-1 until 250 ºC, temperature kept during 60 min. The yields in torrefied and carbonized briquettes, pyroligneous liquor, non-condensable gases and fixed carbon were determined. For all briquettes the fixed carbon, ash, volatile and elemental components (C, H, N, S, O) contents and higher heating value, apparent and energetic density and resistance to diametric compression were quantified. The carbonized briquette presented high energetic potential due to higher fixed and elemental carbon content and heating value, but had low mechanical resistance. The briquettes torrified at the two considered heating rates presented similar energetic properties and characteristics, but lower energetic density than carbonized and fresh briquettes.

Pb/Ti, Sn and Mg-based nanocomposite materials were prepared by the high-energy mechanical milling of commercial powders. The surface of these ceramic compounds was strongly influenced by the doping, diameter of the milling spheres and time of the mechanical milling (amorphization process). Such milling leads to the formation of nanocrystalline materials. The mechanical processing parameters of these compounds were investigated through Brunauer, Emmett and Teller isotherms, wide angle X-ray diffraction, transmission electron microscopy and CO2 adsorption.

We have produced nanocomposite films of Ni:SiO2 by an alternative polymeric precursor route. Films, with thickness of ~ 1000 nm, were characterized by several techniques including X-ray diffraction, scanning electron microscopy, atomic force microscopy, flame absorption atomic spectrometry, and dc magnetization. Results from the microstructural characterizations indicated that metallic Ni-nanoparticles with average diameter of ~ 3 nm are homogeneously distributed in an amorphous SiO2 matrix. Magnetization measurements revealed a blocking temperature T B ~ 7 K for the most diluted sample and the absence of an exchange bias suggesting that Ni nanoparticles are free from an oxide layer.

Neste trabalho é apresentada a reação de condensação aldólica entre metanol e acetona promovida por nanopartículas de dióxido de estanho, não dopadas e dopadas com as terras raras Ce e Y. Diversas condições de relação molar metanol/acetona foram avaliadas, objetivando a obtenção com elevada seletividade do composto a, b-insaturado, metil vinil cetona. As nanopartículas foram preparadas empregando-se o método dos precursores poliméricos. As amostras foram caracterizadas por meio de adsorção de N2 para determinação de área superficial específica (BET), difração de raios X (DRX), adsorção química de CO2, espectroscopia de fotoelétrons (XPS) e microscopia eletrônica de transmissão (MET). O comportamento catalítico observado para as amostras de SnO2 sugere que a relação molar metanol/acetona e a dopagem com as terras raras desempenham um papel importante na atividade catalítica do material e na seletividade aos produtos reacionais. Os resultados de DRX e XPS apontam para a formação de uma camada de segregação, para as amostras dopadas, devido ao tratamento térmico imposto. Essa camada de segregação afeta diretamente o comportamento catalítico do material frente à reação de condensação.

Aldol condensation between methanol and acetone, catalyzed by undoped and rare earths (Ce and Y) doped tin oxide nanoparticles is presented. Several methanol/acetone molar ratio conditions were evaluated aiming to produce methyl vinyl ketone as the main product. The undoped and doped ultrafine nanoparticles of tin oxide were prepared using the polymeric precursor method. The characterization was carried out by means of N2 adsorption (BET), X-ray diffraction (XRD), CO2 chemisorption, X-ray photoemission spectroscopy (XPS) and transmission electron microscopy (TEM). The catalytic behavior observed for SnO2 samples suggests that the methanol/acetone molar ratio and Ce and Y doping play an important role in the catalytic activity and in the product selectivity. The results from XRD and XPS pointed to the de-mixing process for the doped samples, due to the heat-treatment. This segregation layer contributes to the observed change in the catalytic behavior.

Ca1-xLa xTiO3 powders were prepared by the polymeric precursor method. X-ray diffraction (XRD), FT-Raman spectroscopy, transmission electron microscopy (TEM), and N2 and CO2 adsorption were used for the microstructural and surface characterization of the powders. Room temperature photoluminescence (PL) was observed in Ca1-xLa xTiO3 amorphous particles. The PL intensity of these powders was found to be dependent on the lanthanum molar concentration.

The objectives of this work are to supply a basic background on nanostructured materials and also to report about the obtaining of nanoparticles, mainly, tin dioxide nanocrystalline particles (obtained by using the polymeric precursor method) presenting a high stability against particle growth due to the usage of a metastable solid solution. The synthesis and growth of SnO2 nanoribbons by a carbothermal reduction process are also discussed.

The carbon dioxide reforming of methane was carried out over nickel catalysts supported on the gamma-Al2O3/CeO2 system prepared by wet impregnation. With the increase of the CeO2 weight in the catalyst, a higher stability was observed in the catalytic activity, together with an excellent resistance to carbon deposition and a better Ni dispersion. The catalysts were characterized by means of surface area measurements, TPR, H2 chemisorption, XRD, SEM, EDX, XPS and TEM. An interaction between Ni and CeO2 was observed to the Ni/CeO2 sample after activation in a H2 atmosphere above 300 ºC. Such behavior has a significantly influence on the catalytic activity.

Nickel nanoparticles supported on amorphous silica ceramic matrix were synthesized by the polymeric precursor method. The nanostructure was characterized by NMR, BET, XRD, SEM, TEM, and flame atomic absorption spectrometry techniques. It was observed a dependence of the crystallite size on the thermal annealing, under a N2 atmosphere. The materials presented a high catalytic activity and selectivity upon the beta-pinene hydrogenation reaction. The magnetic hystereses were also correlated with the morphology of the processed material.

In this study, the crystallization process of SrTiO3 thin films, prepared by a chemical method, was characterized by Fourier Transformed Infra Red (FT-IR), Grazing Incident X-ray Diffraction (GIXRD), Thermal Analysis (TG) and X-ray Absorption Near Edge Structure (XANES). The results showed that an amorphous inorganic phase is formed, consisting of clusters of oxygen five-coordinate titanium. The amorphous phase begins crystallizing at temperatures above 450 °C. No intermediate crystalline phase and no preferential orientation was observed for films deposited on MgO (100). FT-IR results suggest the presence of the carbonate group. However, the low thermal stability of this group and the low crystallization temperature of the observed SrTiO3 phase indicate that this carbonate is adsorbed.