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PEREIRA, G. R.; ROCHA, H. S. ; CALZA, C. ; ANJOS, M. J. ; PÉREZ, C. A. ; LOPES, R. T. (2009).
Resumo: The main goal of this work is two‐fold: (1) to compare three different excitation conditions in x‐ray fluorescence microtomography (XRFCT) in the analysis of reference samples, and (2) to determine the elemental distribution map for breast tissue samples, in order to verify concentrations of certain elements correlated with characteristics and pathology, using x‐ray transmission microtomography (CT). The experiments were performed at the X‐Ray Fluorescence Facility (D09B‐XRF) of the Brazilian Synchrotron Light Laboratory (LNLS), Campinas, Brazil. In this work, a multilayer monochromator with photon energies near 12 keV, a monochromatic beam at 9.8 keV using a Si (111) crystal, and the white beam were used for elements excitation of elements inside the sample. The sample was placed on a high‐precision goniometer and translation stages, which allowed for rotation as well as translation perpendicular to the beam. Fluorescence photons were collected by means of an energy dispersive HPGe detector placed at 90° to the incident beam, while transmitted photons were detected with a fast Na(Tl) scintillation counter, placed behind the sample, in the direction of the incoming beam. Transmission CT images were reconstructed using a filtered back‐projection algorithm, and XRFCT images were reconstructed using a filtered back‐projection algorithm with absorption correction. Copyright © 2009 John Wiley & Sons, Ltd.
CRUZ, Raphael da Costa ; MARTINS, Rosana Janot ; CARDOSO, Márcio José Estillac de Mello ; BARCIA, O. E. (2009).
Resumo: Density measurements were made for binary aqueous solutions of polyethylene glycol at seven temperatures: 283.15, 288.15, 293.15, 298.15, 303.15, 308.15, and 313.15K. Polyethylene glycol samples with nominal average molar masses of 3000g⋅mol−1 (PEG 3000), 6000g⋅mol−1 (PEG 6000), 10000g⋅mol−1 (PEG 10000) and 20000g⋅mol−1 (PEG 20000) were used. These results were used to determine the specific volumes of solutions with solute-to-solvent mass ratios (mass of the solute/mass of the solvent) in the range 0.0546 to 1.4932 for PEG 3000, from 0.0553 to 1.4986 for PEG 6000, from 0.0552 to 1.2241 for PEG 10000, and from 0.0530 to 1.2264 for PEG 20000. The differences between the specific volume of a solution and the specific volume of the pure solvent, at a given temperature, were represented by a virial-type equation in terms of solute concentration. The first-order coefficient of the expansion is the partial specific volume of the solute at infinite dilution. The higher-order coefficients are related to the contribution of pairs, triplets, and higher-order solute aggregates, according to the Constant-Pressure Solution Theory. The functional dependence of the virial coefficients upon temperature is discussed in terms of solute-solute and solute-solvent interactions. The effect of the PEG molar mass on the partial specific volume of solute at infinite dilution, as well as the contributions of pairs of solute molecules to the solution volume, are also investigated. The apparent specific volume, apparent specific expansibility, apparent specific expansibility at infinite dilution and virial coefficients of the apparent specific expansibility are also presented.
ROCHA, A. C.; OLIVEIRA, Sérgio ; TROTA FILHO, J. ; COUTO, P. R. (2009).
Resumo: The aim of this work is presenting results of uncertainty of measurement calculations applied to both a low temperature PEMFC (proton exchange membrane fuel cell) and a high temperature SOFC (solid oxide fuel cell) by using Monte Carlo method simulations. The intention is correlating electric voltage, obtained in the technical literature, and energetic efficiency of the fuel cells studied in this work. In order to validate the Monte Carlo results achieved a comparison with the procedure for the evaluation of the uncertainty of measurement existing in the GUM 95 ”Guide to the Expression of Uncertainty in Measurement” (by BIPM, IEC, IFCC, ISO, IUPAC, IUPAP and OIML) is made. A reasoning of the balancing of the sources of uncertainty is presented as well. In last, it is discussed why the calibration process and traceability of the voltmeter are key factors in providing reliable metrological results in the production of electricity by fuel cell technology. This work is the first part of a broader study from which the next steps will be the validation of these presented simulations by fuel cell bench tests and the planning and development of Brazilian Conformity Assessment programs for PEMFC and SOFC fuel cells afterwards.
DASILVA, C ; MARGARITMATTOS, I ; MATTOS, O ; PERROT, H ; TRIBOLLET, B ; VIVIER, V. (2009).
Resumo: The molybdate–zinc conversion process was investigated by means of different techniques such as EIS, interfacial pH measurements, QCM and SECM. SEM and XPS complemented the electrochemical measurements. EIS results have shown different behaviour as function of the pH of the solution. Interfacial pH measurements have evidenced that the coatings were formed after about 200 s. The QCM measurements have exhibited three main characteristic regions and have shown that the formation kinetics was pH-dependent. The surface characterization has shown the presence of Mo5+ inside the coatings. The Mo and P amounts did not markedly change when the conversion time was increased.
Fragata, F. L. ; AMORIM, C. C. ; Ordine, A. P. ; MARROIG, M. C. ; MOTA, R. O. ; MARGARIT-MATTOS, I. C. P. (2009).
Resumo: Surface cleaning tools made of copper alloys are widely employed when sparks have to be avoided. On the other hand, copper residues may be left on the surface. It is not known whether such copper incrustation interferes with the performance of a painting system. Therefore, the aim of this paper is to evaluate the effect of steel surface treatment with copper-containing tools on the performance of a painting system. Painted samples pretreated with ferrous and copper-containing tools were submitted to corrosion tests. The performance was monitored by visual inspection and electrochemical impedance. The surfaces of unpainted samples were analyzed by energy dispersion spectroscopy (EDS) and the open circuit potentials were measured. It is shown that the residues left on the metallic surface due to the mechanical action of the cleaning tools did not interfere significantly with the performance of the painting system.
