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Abstract  

Two cyclotrons are being operated at IPEN-CNEN/SP: one model CV-28, capable of accelerating protons with energies up to 24 MeV and beam currents up to 30 mA, and three other particles; the other one, model Cyclone 30, accelerates protons with energy of 30 MeV and currents up to 350 mA. Both have the objective of irradiating targets both for radioisotope production for use in nuclear medicine and general research. The development of irradiating systems completely automatized was the objective of this work, always aiming to reduce the radiation exposition dose to the workers and to increase the reliability of use of these systems.

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Abstract  

The development of an automated water target for the production of18F is described. The system was fully fested and shown to be reliable and secure. The chemical separation of18F was carried out using an anionexchange resin and K2CO3 as eluent. The18F production yields were, on average, (4.81±0.42) MBq/Ah and the specific activity was higher than 6.623×105 MBq/mmol. Heat transfer measurements and calculations were made.

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Abstract  

The SiMCM-41 mesoporous molecular sieve was synthesised by the hydrothermal method. The physicochemical characterisation by infrared spectroscopy, X-ray diffraction and thermogravimetry, showed that the material presents a well-defined structure. In this study, the determination of the total acidity and relative strength of the acid sites of the SiMCM-41,was performed by desorption of adsorbed n-butylamine combined with thermogravimetric measurements. The total acidity, determined by means of the amount of amine desorbed normalised by mass of solid, was equivalent to 0.927 mmol g–1, in the temperature range from 96 to 235°C. By using the Flynn and Wall integral kinetic model, at 5, 10 and 20°C min–1 heating rates, it was determined that the activation energy to desorb n-butylamine was 90.7 kJ mol–1, in the same temperature range, evidencing that SiMCM-41 presents only weak acid sites on its surface.

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Journal of Thermal Analysis and Calorimetry
Authors: Ana C. R. Melo, Edjane F. B. Silva, Larissa C. L. F. Araujo, Mirna F. Farias, and Antonio S. Araujo

Abstract

In this study, were studied the degradation of pure sunflower oil and mixed with H-Beta zeolite. This zeolite was synthesized by the hydrothermal method, followed by calcination and ion exchanged. The characterization of the zeolite was performed by X-ray diffraction and nitrogen adsorption/desorption by the method of BET. The analysis showed that H-Beta zeolite presented a good crystallinity and the template was completely removed from the catalyst. The thermal and catalytic degradation study was carried out using the TG/DTG method in multiple heating rates of 5, 10, and 20 °C min−1. The isoconversion method proposed by Vyazovkin was applied to determine the kinetic parameters for degradation of the sunflower oil. The activation energy for the degradation process of pure sunflower oil was 193 kJ mol−1, while for sunflower oil mixed with 20% of H-Beta zeolite was equivalent to 88 kJ mol−1. It was verified that for the degradation of 90% of the sunflower oil mixed with H-Beta, for a period of 1 h, a temperature of 356 °C was required, whereas for the pure vegetable oil, this value was of 387 °C, at the same time period, showing that the catalyst was effective for the degradation process of sunflower oil.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Costa, S. Crispim, S. Lima, C. Paskocimas, E. Longo, V. Fernandes, A. Araújo, and I. Santos

Abstract  

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Journal of Thermal Analysis and Calorimetry
Authors: S. Silva, M. Conceiçăo, A. Souza, S. Prasad, M. Silva, V. Fernandes, A. Araújo, and F. Sinfrônio

Abstract  

The powder and the bran of algaroba pods, submitted to drying temperatures of 55, 65, 75, 85, 95 and 105C, were studied by conventional and thermogravimetric methods. The dynamic thermogravimetric curves of the samples indicated the following thermal stability order: 105>55>65>95>85>75C. The powder and the bran of algaroba pods, dried at 55C, presented protein content higher and isothermal thermogravimetric profiles comparable. The calorimetric curves of samples, dried at 55C, indicated the gelatinization of starch.

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