Navegando por Autor "Candeia, R. A."
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Artigo Effect of the modifier ion on the properties of MgFe2O4 and ZnFe2O4 pigments(Springer, 2007-03-07) Xavier, Camila S.; Candeia, R. A.; Bernardi, M. I. B; Lima, S. J. G.; Silva, Elson Longo da; Paskocimas, Carlos Alberto; Soledade, Luiz Edmundo Bastos; Souza, Antônio Gouveia de; Santos, Ieda Maria Garcia dosMagnesium and zinc ferrites have been prepared by the polymeric precursor method. The organic material decomposition was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The variation of crystalline phases and particle morphology with calcination temperature were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The colors of the ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes above 800°C, presenting a yellow-orange color with a reflectance peak at the 600–650 nm range, while zinc ferrite crystallizes at 600°C, with a reflectance peak between 650–700 nm, corresponding to the red-brick colorArtigo Influence of soybean biodiesel content on basic properties of biodiesel–diesel blends(Elsevier BV, 2009-04) Bicudo, Tatiana de Campos; Candeia, R. A.; Silva, M. C. D.; Carvalho Filho, J. R.; Brasilino, M. G. A.; Santos, I. M. G.; Souza, A. G.The world tendency in last years is to restrict the use of fossil fuels and replace them partially or totally by renewable fuels. Accordingly, biodiesel is being studied as one of the main alternatives and the production and consumption of this pure biofuel and its binary blends with fossil diesel have been markedly grown. Thus, the present work evaluated the influence of biodiesel concentration on such blends when mixed to diesel in 5, 15, 25 and 50 volume percentages. For each blend, both methanol and ethanol biodiesels were investigated. The biodiesel samples were physicochemically characterized. Their rheological behavior was analyzed. It was observed that the biodiesel enrichment leads to an acceptable increase in the viscosity and to a decrease in the volatilization of the binary blends. The viscosity was also shown to be temperature-dependent, as well as the fatty acids chain length and unsaturationArtigo Influence of the storage on the thermo-oxidative stability of methyl and ethyl esters by PDSC(Springer, 2011-02-14) Bicudo, Tatiana de Campos; Candeia, R. A.; Sinfrônio, F. S. M.; Queiroz, N.; Barros Filho, A. K. D.; Soledade, Luiz Edmundo Bastos; Santos, I. M. G.; Souza, A. L.; Souza, A. G.Biodiesel oxidation is a complex process widely influenced by the chemical composition of the biofuel and storage conditions. Several oxidation products can be formed from these processes, depending on type and amount of the unsaturated fatty acid esters. In this work, fatty acid methyl and ethyl esters were obtained by basecatalyzed transesterification of soybean oil and physicochemically characterized according to standards from ASTM, EN, and ABNT. The thermal and oxidative stabilities of biodiesel samples were investigated during the storage process by pressure differential scanning calorimetry (PDSC) and by viscosity measurements. Absolute viscosities of biodiesels after accelerated aging were also determined. The viscosity increased as the aging temperature and time were raised. The results showed that oxidation induction can occur during storage, decreasing the biodiesel stability. PDSC analysis showed that during storage under climate simulation the values of high-pressure oxidative induction times (HPOIT) were reduced for both FAEE and FAME