RODRIGO UCHIDA ICHIKAWA
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Artigo IPEN-doc 27404 Characterization of nanostructured Mn-Zn ferrites synthesized by coprecipitation method using CTAB2020 - MARANHAO, W.C.A.; ICHIKAWA, R.U.; TURRILLAS, X.; YOSHITO, W.K.; SAEKI, M.J.; ORLANDO, M.T.D.; MARTINEZ, L.G.In this work it was investigated the influence of CTAB surfactant concentration on the synthesis of the compound Mn0.75Zn0.25Fe2O4 by the coprecipitation method. It was also compared the influence of hydrothermal treatment on the synthesized materials. The magnetic properties were characterized by AC susceptometry for the determination of the magnetic susceptibility and magnetic density energy. The phases, crystal structure and morphology of the nanoferrites were determined by Rietveld analysis of X-ray diffraction data. It was found the presence of two phases: Franklinite and Akaganeite and it was shown that the samples synthesized only by coprecipitation presented the tendency to increasing the crystallite sizes of the akaganeite phase and decreasing of crystallite sizes of the Franklinite phase as a function of CTAB concentration. The samples submitted to subsequent hydrothermal treatment presented a tendency to decreasing the crystallite sizes of both phases and increasing in Franklinite phase fraction, compared to the samples synthesized only by coprecipitation, suggesting that the hydrothermal treatment was effective in obtaining nanostructured materials of smaller particles.Artigo IPEN-doc 24312 Characterization of Mn0.67Zn0.33Fe2O4 nanoparticles synthesized under different pH2017 - ICHIKAWA, RODRIGO U.; YOSHITO, WALTER K.; SAEKI, MARGARIDA J.; MARANHAO, WILLIAN C.A.; GOULART, FATIMA; MARTINEZ, LUIS G.Nanostructured Mn-Zn ferrites were synthesized using co-precipitation in alkaline solution with different pH. The samples were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), thermal analysis (TG-DTA), dynamic light scattering (DLS) and scanning electron microscopy (SEM) techniques. Monophasic nanoparticles were formed when synthesized with pH 10.5. This sample was heat-treated and its XRD data was refined by the Rietveld method. Mean crystallite sizes and microstrains were determined from X-ray line profile analysis using Single-Line and Warren-Averbach methods, which revealed a mean crystallite size of approximately 10 nm and negligible microstrains. Zn content was estimated using refined cell parameters, giving a value of 33 at %, in accordance with XRF result. TG-DTA revealed that the incorporation of α-Fe2O3 occurs around 1130 °C and 1200 °C with recrystallization of the Mn-Zn ferrite spinel phase. DLS showed that mean particle size increase with temperature up to 1159 nm at 800 °C. SEM analysis showed the samples agglomerate and present similar morphology with negligible size changing when calcined between 280 °C and 800 °C. However, the sample calcined at 1200 °C presents larger agglomerates due to the sintering process.Resumo IPEN-doc 21606 Size-strain analysis of nanostructured Mn-Zn ferrites using x-ray line profile methods2015 - ICHIKAWA, R.U.; PARRA, J.P.R.L.L.; MARTINS, M.L.; YOSHITO, W.K.; SAEKI, M.J.; TURRILLAS, X.; MARTINEZ, L.G.Artigo IPEN-doc 21598 Characterization of Mnsub(0.67)Znsub(0.33)Fesub(2)Osub(4) nanoparticles synthesized under different pH2015 - ICHIKAWA, RODRIGO U.; YOSHITO, WALTER K.; SAEKI, MARGARIDA J.; MARANHAO, WILLIAN C.A.; GOULART, FATIMA; MARTINEZ, LUIS G.