Structure and Physical Properties of EVA/Starch Precursor Materials for Foaming Applications

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

Deposição de A/N por sputtering não reativo

In this work we deposit via non-reactive magnetron sputtering of radio-frequency nanofilmes of nitreto of aluminum(AlN). The nanofilms aluminum nitride are semiconductors materials with high thermal conductivity, high melting point, piezoelectricity and wide band gap (6, 2 eV) with hexagonal wurtzite crystal structure, belonging to the group of new materials called III-V nitrides in which together with the gallium nitride and indium nitride have attracted much interest because they have physical and chemical properties relevant to new technological applications, mainly in microelectronic and optoelectronic devices. Three groups were deposited with thicknesses nanofilms time dependent on two substrates (glass and silicon) at a temperature of 25 ° C. The nanofilms AlN were characterized using three techniques, X-ray diffraction, Raman spectroscopy and atomic force microscopy (AFM), examined the morphology of these. Through the analysis of X-rays get the thickness of each sample with its corresponding deposition rate. The analysis of X-rays also revealed that nanofilms are not crystalline, showing the amorphous character of the samples. The results obtained by the technique, atomic force microscopy (AFM) agree with those obtained using the technique of X-rays. Characterization by Raman spectroscopy revealed the existence of active modes characteristic of AlN in the samples

Organochlorine pesticides and polychlorinated biphenyls in soil and water samples in the northeastern part of São Paulo State, Brazil

Detailed analyses of persistent organic pollutants (POPs) such as organochlorine pesticides (OCPs), hexachlorocyclohexane (HCH) isomers (HCHs), dichlorodiphenyltrichloro ethane (DDT) and its metabolites (DDTs) and congeners of polychlorinated biphenyls (PCBs) in soil and surface water from the northeastern São Paulo, Brazil allowed the evaluation of the contamination status, distribution and possible pollution sources. The pesticides and PCBs demonstrated markedly different distributions, reflecting different agricultural, domestic and industrial usage in each region studied. The ranges of HCH, DDT, and PCBs concentrations in the soil samples were 0.05-0.92, 0.12-11.01, 0.02-0.25 ng g(-1) dry wt, respectively, and in the surface water samples were 0.02-0.6, 0.02-0.58 and 0.02-0.5 ng l(-1), respectively. Overall elevated levels of DDT and PCB were recorded in region 2, a site very close to melting, automotive batteries industries, and agricultural practice regions. High ratios of metabolites of DDT to DDT isomers revealed the recent use of DDT in this environment. The sources of contamination are closely related to human activities, such as domestic and industrial discharge, street runoff, agricultural pesticides and soil erosion, due to deforestation as well as atmospheric transport. (c) 2006 Elsevier Ltd. All rights reserved.

Análises estatísticas em redes complexas: propriedades topológicas, críticas e dinâmicas

In this thesis, we address two issues of broad conceptual and practical relevance in the study of complex networks. The first is associated with the topological characterization of networks while the second relates to dynamical processes that occur on top of them. Regarding the first line of study, we initially designed a model for networks growth where preferential attachment includes: (i) connectivity and (ii) homophily (links between sites with similar characteristics are more likely). From this, we observe that the competition between these two aspects leads to a heterogeneous pattern of connections with the topological properties of the network showing quite interesting results. In particular, we emphasize that there is a region where the characteristics of sites play an important role not only for the rate at which they get links, but also for the number of connections which occur between sites with similar and dissimilar characteristics. Finally, we investigate the spread of epidemics on the network topology developed, whereas its dissemination follows the rules of the contact process. Using Monte Carlo simulations, we show that the competition between states (infected/healthy) sites, induces a transition between an active phase (presence of sick) and an inactive (no sick). In this context, we estimate the critical point of the transition phase through the cumulant Binder and ratio between moments of the order parameter. Then, using finite size scaling analysis, we determine the critical exponents associated with this transition

Influence of the Substitutional Solute on the Mechanical Properties of Ti-Nb Binary Alloys for Biomedical Use

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Solid-liquid transition in Nb powder determined by third harmonic susceptibility

Measurements of the third harmonic of the AC-susceptibility were employed to determine the boundaries of the linear regime of the magnetic response of Nb powder. Non-linear contributions to the magnetic response reveal the occurrence of a structured phase, disappearing as the vortex lattice melts to the liquid state. A systematic study of the third harmonic was conducted to determine how its onset temperature depends on experimental parameters, such as the frequency and amplitude of the excitation field. The melting line (ML) has been extracted from the onset temperature measured at low-frequencies and low-excitation fields in the presence of DC magnetic fields. The study indicates that the ML can be described by a 3D vortex-glass model, except at lower fields, where the system experiences a depinning crossover, and the best description of the experimental data is provided by a 3D Bose-glass model. (c) 2008 Elsevier B. V. All rights reserved.

Efeitos da história térmica nas propriedades do polímero pet: um experimento para ensino de análise térmica

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

Preparation and characterization of ordered intermetallic platinum phases for electrocatalytic applications

Ordered intermetallic phases of Pt with several transition metals have been prepared and their electrocatalytic properties studied. In light of these tests it is proposed that these catalysts could be used as electrodes in fuel cells, as they combine an excellent capacity to adsorb organic fuels at the Pt sites with low susceptibility to being poisoned by intermediates and reaction products at the transition-metal sites. An experimental procedure used to obtain the four intermetallic phases Pt-M (M = Mn, Pb, Sb and Sn) is described. The phases thus produced were characterized by X-ray diffraction, scanning electron microscopy with surface analysis by energy-dispersive X-ray spectrometry, scanning tunneling microscopy and X-ray photoelectron spectroscopy. The data thus obtained support the conclusion that the method described here is highly effective for the preparation of Pt-M phases featuring a range of structural and electronic modifications that will allow a useful relation to be established between their physicochemical properties and predicted electrocatalytic activity. (C) 2007 Elsevier Ltd. All rights reserved.

Influência da Dureza dos Discos Abrasivos no Corte de Materiais Dúcteis

O corte de materiais por disco abrasivo é um dos processos que apresentam as melhores características de economia, eficiência e rapidez sendo muito utilizado no meio industrial. Fatores como porcentagens e homogeneidade da mistura dos componentes, tamanho, forma (abrasividade), tenacidade e dureza dos grãos abrasivos, tipos de ligantes e de abrasivos, velocidade de corte e velocidade de mergulho influenciam na segurança, no desempenho e comportamento da operação. Este trabalho apresenta um estudo sobre a influência da dureza dos discos abrasivos no desempenho do processo de corte em operações do tipo remoção a seco. O aumento da dureza dos discos propiciou um aumento da força tangencial de corte e da relação G, devido à mais forte ligação entre o grão e o ligante no compósito. Os resultados mostram que a dureza dos discos abrasivos afeta a economia, pois influencia na vida útil dos discos abrasivos em termos de números de cortes proporcionados; a produtividade, pois está relacionada com o número de trocas de discos desgastados; os esforços necessários para a operação, pois estão relacionados com as forças tangenciais de corte.

Evaluation of Electrical Properties of Lap Joints for BSCCO and YBCO Tapes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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)

Alumina porous ceramics: mathematical behavior at different commercial starch concentration

Several researches have been developed in order to verify the porosity effect over the ceramic material properties. The starch consolidation casting (SCC) allows to obtain porous ceramics by using starch as a binder and pore forming element. This work is intended to describe the porous mathematical behavior and the mechanical resistance at different commercial starch concentration. Ceramic samples were made with alumina and potato and corn starches. The slips were prepared with 10 to 50 wt% of starch. The specimens were characterized by apparent density measurements and three-point flexural test associated to Weibull statistics. Results indicated that the porosity showed a first-order exponential equation e(-x/c) increasing in both kinds of starches, so it was confirmed that the alumina ceramic porosity is related to the kind of starch used. The mechanical resistance is represented by a logarithmic expression R = A + B/1+10((Log(x0)-P)C).

FeNbP in ultra-low carbon Nb-added steel containing high P

Precipitation of FeTiP is reported to occur in Ti-added IF steels containing high P during thermomechanical processing. An ultra-low carbon (ULC) Nb-added steel ingot containing a higher P content (< 0.8 wt-%) was produced via aluminothermic reduction of Fe2O3 followed by double electron beam melting (EBM). FeNbP coarse precipitates were observed in the as-cast microstructure. After soaking at 1050C for 1 h, the plate was hot rolled from 31 mm down to 7 mm in thickness (total reduction of 77%). During cold rolling of these hot bands we observed embrittlement. We believe that this embrittlement can be attributed to the presence of the FeNbP precipitates. Light optical and scanning electron microscopy (SEM/EDS) were used to characterize the microstructure of this ULC steel. (C) 2000 Elsevier B.V. All rights reserved.

Avaliações térmica e reológica da matriz termoplástica PEKK utilizada em compósitos aeronáuticos

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