Caracterização e análise das propriedades da fibra de Macambira (Bromelia Laciniosa)

Concern for the environment and the exploitation of natural resources has motivated the development of research in lignocellulosic materials, mainly from plant fibers. The major attraction of these materials include the fact that the fibers are biodegradable, they are a renewable natural resource, low cost and they usually produce less wear on equipment manufacturing when compared with synthetic fibers. Its applications are focused on the areas of technology, including automotive, aerospace, marine, civil, among others, due to the advantageous use in economic and ecological terms. Therefore, this study aims to characterize and analyze the properties of plant fiber macambira (bromelia laciniosa), which were obtained in the municipality of Ielmo Marino, in the state of Rio Grande do Norte, located in the region of the Wasteland Potiguar. The characterization of the fiber is given by SEM analysis, tensile test, TG, FTIR, chemical analysis, in addition to obtaining his title and density. The results showed that the extraction of the fibers, only 0.5% of the material is converted into fibers. The results for title and density were satisfactory when compared with other fibers of the same nature. Its structure is composed of microfibrils and its surface is roughened. The cross section has a non-uniform geometry, therefore, it is understood that its diameter is variable along the entire fiber. Values for tensile strength were lower than those of sisal fibers and curauá. The degradation temperature remained equivalent to the degradation temperatures of other vegetable fibers. In FTIR analysis showed that the heat treatment may be an alternative to making the fiber hydrophobic, since, at high temperature can remove the hemicellulose layer, responsible for moisture absorption. Its chemical constitution is endowed with elements of polar nature, so their moisture is around 8.5% which is equivalent to the percentage of moisture content of hydrophilic fibers. It can be concluded that the fiber macambira stands as an alternative materials from renewable sources and depending on the actual application and purpose, it may achieve satisfactory results

Avaliação, identificação e atividade enzimática de bactérias psicotróficas presentes no leite cru refrigerado

Extended storage of refrigerated milk can lead to reduced quality of raw and processed milk, which is a consequence of the growth and metabolic activities of psychrotrophic bacteria, able to grow under 7oC or lower temperatures. Although most of these microorganisms are destroyed by heat treatment, some have the potential to produce termoresistant proteolytic and lipolytic enzymes that can survive even UHT processing and reduce the processed products quality. Recently, the IN 51 determineds that milk should be refrigerated and stored at the farm what increased the importance of this group of microorganisms. In this work, psychrotrophic bacteria were isolated from 20 communitarian bulk tanks and 23 individual bulk tanks from dairy farms located at Zona da Mata region of Minas Gerais State and from southeastern Rio de Janeiro. Selected milk dilutions were plated on standard agar and after incubation for 10 days at 7oC, five colonies were isolated, firstly using nutrient agar and after using McConkey agar for 24 hours at 21oC. The isolates were identified by morphology, Gram stain method, catalase production, fermentative/oxidative metabolism and by API 20E, API 20NE, API Staph, API Coryne or API 50 CH (BioMerieux). In order to ensure reproductibility, API was repeated for 50% of the isolates. Species identification was considered when APILAB indexes reached 75% or higher. 309 strains were isolated, 250 Gram negative and 59 Gram positive. 250 Gram negative isolates were identified as: Acinetobacter spp. (39), Aeromonas spp. (07), A. Hydrophila (16), A. sobria (1), A. caviae (1), Alcaligenes feacalis (1), Burkholderia cepacia (12), Chryseomonas luteola (3), Enterobacter sp. (1), Ewingella americana(6), Hafnia alvei (7), Klebsiella sp. (1), Klebsiella oxytoca (10), Yersinia spp. (2), Methylobacterium mesophilicum (1), Moraxella spp. (4), Pantoea spp. (16), Pasteurella sp. (1), Pseudomonas spp. (10), P. fluorescens (94), P. putida (3), Serratia spp. (3), Sphigomonas paucomobilis (1). Five isolates kept unidentified. Pseudomonas was the predominant bacteria found (43%) and P. fluorescens the predominant species (37.6%), in accordance with previous reports. Qualitative analysis of proteolytic and lipolytic activity was based on halo formation using caseinate agar and tributirina agar during 72 hours at 21oC and during 10 days at 4°C, 10oC and 7°C. Among 250 Gram negative bacteria found, 104 were identified as Pseudomonas spp. and 60,57% of this group showed proteolytic and lipolytic acitivities over all four studied temperatures. 20% of Acinetobacter, Aeromonas, Alcaligenes, Burkholderia, Chryseomonas, Methylobacterium, Moraxella presented only lipolytic activity. Some isolates presented enzymatic activity in one or more studied temperatures. Among Gram positive bacteria, 30.51% were proteolytic and lipolytic at 10oC, 8.47% were proteolytic at 7oC, 10oC, and 21oC, 8.47% were proteolytic at all studied temperatures (4oC, 7oC, 10oC and 21oC) and 3.38% were proteolytic only at 21oC. At 4oC, only one isolate showed proteolytic activity and six isolates were lipolytic. In relation to Gram negative microorganisms, 4% were proteolytic and lipolytic at 7oC, 10oC and 21oC, 10% were proteolytic at 10oC and 4.4% were lipolytic at 4oC, 7oC, 10oC and 21oC, while 6.4% of all isolates were proteolytic and lipolytic at 10oC and 21oC as well as lipolytic at 4oC and 7oC. These findings are in accordance with previous researches that pointed out Pseudomonas as the predominant psycrotrophic flora in stored refrigerated raw milk

Estudo dos óxidos A2B2O7 e ABO3 a base de terras raras, para aplicações térmicas e catalíticas a altas temperaturas

Rare earth elements have recently been involved in a range of advanced technologies like microelectronics, membranes for catalytic conversion and applications in gas sensors. In the family of rare earth elements like cerium can play a key role in such industrial applications. However, the high cost of these materials and the control and efficiencies associated processes required for its use in advanced technologies, are a permanent obstacle to its industrial development. In present study was proposed the creation of phases based on rare earth elements that can be used because of its thermal behavior, ionic conduction and catalytic properties. This way were studied two types of structure (ABO3 and A2B2O7), the basis of rare earths, observing their transport properties of ionic and electronic, as well as their catalytic applications in the treatment of methane. For the process of obtaining the first structure, a new synthesis method based on the use of EDTA citrate mixture was used to develop a precursor, which undergone heat treatment at 950 ° C resulted in the development of submicron phase BaCeO3 powders. The catalytic activity of perovskite begins at 450 ° C to achieve complete conversion at 675 ° C, where at this temperature, the catalytic efficiency of the phase is maximum. The evolution of conductivity with temperature for the perovskite phase revealed a series of electrical changes strongly correlated with structural transitions known in the literature. Finally, we can establish a real correlation between the high catalytic activity observed around the temperature of 650 ° C and increasing the oxygen ionic conductivity. For the second structure, showed clearly that it is possible, through chemical processes optimized to separate the rare earth elements and synthesize a pyrochlore phase TR2Ce2O7 particular formula. This "extracted phase" can be obtained directly at low cost, based on complex systems made of natural minerals and tailings, such as monazite. Moreover, this method is applied to matters of "no cost", which is the case of waste, making a preparation method of phases useful for high technology applications

The effect of Eu3+ concentration on the Y2O3 host lattice obtained from citrate precursors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Intake of isoflavone-supplemented soy yogurt fermented with Enterococcus faecium lowers serum total cholesterol and non-HDL cholesterol of hypercholesterolemic rats

The aim of this study was to obtain an isoflavone-supplemented soy yogurt, fermented with Enterococcus faecium CRL 183 and Lactobacillus helveticus ssp jugurti, with suitable sensory properties and to assess the effects of the final product on blood lipids in hypercholesterolemic rats. Four isoflavone supplementation procedures were tested, in which the isoflavone was added at these stages: (1) before heat-treatment; (2) after heating and before fermentation; (3) after fermentation and (4) in the okara (by-product of soy milk) flour stirred into the fermented product when consumed. The products were subjected to a test of sensory acceptability. To assess their potential hypocholesterolemic properties in vivo, four groups of rats were used: control (C), hypercholesterolemic (H), hypercholesterolemic plus fermented product (HF) and hypercholesterolemic plus isoflavone-supplemented fermented product (HFI). Hypercholesterolemia was induced in rats of groups H, HF and HFI by feeding them on a commercial rat chow to which cholesterol and cholic acid had been added. Total, HDL and non-HDL cholesterol and triglycerides were measured in the blood of the rats. No significant sensorial differences were detected among the samples of soy yogurt supplemented with isoflavones at various processing stages. Rats fed a fermented soy product enriched with isoflavones (HFI group) had significantly (P < 0.05) less serum total cholesterol (15.5%) compared with rats fed a hypercholesterolemic diet (H group). Non-HDL cholesterol was less (P < 0.05) in rats fed a fermented soy product enriched or not with isoflavones (27.4 and 23.2%) compared to H group. The HDL-C and triglyceride concentrations did not differ significantly among the groups. It was possible to obtain an isoflavone-supplemented soy yogurt with satisfactory sensory characteristics. The resulting supplemented soy yogurt was capable of producing a lipid-lowering effect in hypercholesterolemic rats, relative to the animals that did not consume this product.

Structural and electrochemical properties of LiCoO2 prepared by combustion synthesis

LiCoO2 powders were prepared by combustion synthesis, using metallic nitrates as the oxidant and metal sources and urea as fuel. A small amount of the LiCoO2 phase was obtained directly from the combustion reaction, however, a heat treatment was necessary for the phase crystallization. The heat treatment was performed at the temperature range from 400 up to 700 degreesC for 12 h. The powders were characterized by X-ray diffraction (XRD), X ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and specific surface area values were obtained by BET isotherms. Composite electrodes were prepared using a mixture of LiCoO2, carbon black and poly(vinylidene fluoride) (PVDF) in the 85:10:5% w/w ratio. The electrochemical behavior of these composites was evaluated in ethylene carbonate/dimethylcarbonate solution, using lithium perchlorate as supporting electrolyte. Cyclic voltammograms showed one reversible redox process at 4.0/3.85 V and one irreversible redox process at 3.3 V for the LiCoO2 obtained after a post-heat treatment at 400 and 500 degreesC.Raman spectroscopy showed the possible presence of LiCoO2 with cubic structure for the material obtained at 400 and 500 degreesC. This result is in agreement with X-ray data with structural refinement for the LiCoO2 powders obtained at different temperatures using the Rietveld method. Data from this method showed the coexistence of cubic LiCoO2 (spinel) and rhombohedral (layered) structures when LiCoO2 was obtained at lower temperatures (400 and 500 degreesC). The single rhombohedral structure for LiCoO2 was obtained after post-heat treatment at 600 degreesC. The maximum energy capacity in the first discharge was 136 mA g(-1) for the composite electrode based on LiCoO2 obtained after heat treatment at 700 degreesC. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Dynamical Elastic Moduli of the Ti-13Nb-13Zr biomaterial alloy by mechanical spectroscopy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermo and photochromic properties of Na2O-WO3-SbPO4 glasses

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural characterization of Ti-15Mo alloy used as biomaterial by Rietveld method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nanoindentation mechanical properties characterization of glassy polymeric carbon treated with ion beam

Phenolic resins when heat treated in inert atmosphere up to 1000 degreesC become glassy polymeric carbon (GPC), a chemically inert and biocompatible material useful for medical applications, such as in the manufacture of heart valves and prosthetic devices. In earlier work we have shown that ion bombardment can modify the surface of GPC, increasing its roughness. The enhanced roughness, which depends on the species, energy and fluence of the ion beam, can improve the biocompatibility of GPC prosthetic artifacts. In this work, ion bombardment was used to make a layer of implanted ions under the surface to avoid the propagation of microcracks in regions where cardiac valves should have pins for fixation of the leaflets. GPC samples prepared at 700 and 1500 degreesC were bombarded with ions of silicon. carbon, oxygen and gold at energies of 5, 6, 8 and 10 MeV, respectively, and fluences between 1.0 x 10(13) and 1.0 x 10(16) ions/cm(2). Nanoindentation hardness characterization was used to compare bombarded with non-bombarded samples prepared at temperatures up to 2500 degreesC. The results with samples not bombarded showed that the hardness of GPC increases strongly with the heat treatment temperature. Comparison with ion bombarded samples shows that the hardness changes according to the ion used, the energy and fluence. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Obtaining of Nanoapatite in Ti-7.5Mo Surface After Nanotube Growth

Titanium and their alloys have been used for biomedical applications due their excellent mechanical properties, corrosion resistance and biocompatibility. However, they are considered bioinerts materials because when they are inserted into the human body they are cannot form a chemical bond with bone. In several studies, the authors have attempted to modify their characteristic with treatments that changes the material surface. The purpose of this work was to evaluate obtaining of nanoapatite after growing of the nanotubes in surface of Ti-7.5Mo alloy. Alloy was obtained from c.p. titanium and molibdenium by using an arc-melting furnace. Ingots were submitted to heat treatment and they were cold worked by swaging. Nanotubes were processed using anodic oxidation of alloy in electrolyte solution. Surfaces were investigated using scanning electron microscope (SEM), FEG-SEM and thin-film x-ray diffraction. The results indicate that nanoapatite coating could form on surface of Ti-7.5Mo experimental alloy after nanotubes growth.

Growth of Calcium Phosphate Using Chemically Treated Titanium Oxide Nanotubes

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A metallurgical study of aluminium alloys used as aircraft components

The effects of heat treatment on morphologies and microstructures of Al 2024 and Al 7050 alloys, used as aircraft components, were studied by metallographic techniques. Light microscopy (LM) and quantitative image analysis were used to characterize the precipitate dispersion and morphology for these alloys. The application of the scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) combined techniques for studying these multiphase systems makes it possible to distinguish and quantify the different phases in the surface structure. Xray diffraction also permitted a qualitative comparison of the structures before and after heat treatments.

Caracterização mecânica e microestrutural de um aço baixo carbono microligado com estrutura multifásica

Neste trabalho foi realizada a caracterização mecânica e microestrutural de um aço microligado com estrutura multifásica. Foi aplicado tratamento térmico pré-determinado, objetivando a formação de uma microestrutura multifásica no material. Na caracterização microestrutural foram utilizados ataques químicos à base de metabissulfito de sódio e ácido pícrico, enquanto a caracterização mecânica foi realizada através de ensaios de tração. Os resultados demonstram o elevado potencial dos aços multifásicos em aplicações que necessitem de valores superiores de resistência e ductilidade, pois tanto para temperatura isotérmica de 400ºC quanto para 350ºC houve um ganho no limite de resistência à tração ficando em torno de 786MPa e 773MPa respectivamente, representando um aumento de 15,5% e 13,6% com relação ao material fornecido.

Surface characterization of Ti-7.5Mo alloy modified by biomimetic method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)