RODRIGO UCHIDA ICHIKAWA

RODRIGO UCHIDA ICHIKAWA

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Characterization of nanostructured Mn-Zn ferrites synthesized by coprecipitation method using CTAB
2020 - 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.
The influence of iron content and alkaline concentration on Mn0.75Zn0.25FeyO4 structure, surface charge and acb response
2017 - MOURA, TIAGO F.A.; NAVARRO, RAPHAELLA; SHIOTSUKI, AUGUSTO K.; UTIYAMA, ANA P.M.S.; ICHIKAWA, RODRIGO U.; MATOS, RONALDO V.R.; CASTRO, GUSTAVO R.; YOSHITO, WALTER K.; MARTINEZ, L.G.; MIRANDA, JOSE R.A.; SAEKI, MARGARIDA J.
Nanotechnology applied on magnetic material provide a good opportunity to develop biomaterials as tracers for Alternating Current Biosuceptometry (ACB)and Magnetic Resonance Imaging (MRI) to diagnose certain diseases as cancer. The magnetic nanoparticles can still constitute drug carrier systems and hyperthermia agent for cancer treatment. Neverthless, the efficiency for therapy and diagnosis depends on the magnetic susceptibility. In this work, the ferrite nanoparticles with nominal composition Mn0.75Zn0.25FeyO4, where 1.5 ≤ y ≤ 2.8, were synthesized by the co-precipitation method and, the influence of iron content and concentration of precipitating agent on the structure, ACB response and surface charge was analyzed. It was noted that the synthesis using alkaline metal hydroxide between 0.1, 0.15 and 0.2 mol/L provides single-phase materials [ICSD 28515 (PDF - 742 402), space group Fd3m]. The higher concentration (0.25 mol/L) leads to materials with higher crystallinity and similar ACB response to those precipitated by lower concentration base, despite the secondary phase. A surface charge of 30 mV in module was achieved, which decreased as the concentration of the precipitating agent increased.
Cation distribution of Mn-Zn ferrite nanoparticles using pair distribution function analysis and resonant X-ray scattering
2018 - ICHIKAWA, RODRIGO U.; PARRA, JOAO P.R.L.L.; VALLCORBA, ORIOL; PERAL, INMA; YOSHITO, WALTER K.; SAEKI, MARGARIDA J.; TURRILLAS, XAVIER; MARTINEZ, LUIS G.
Mn-Zn ferrite nanoparticles were synthesized by chemical co-precipitation method and analysed using X-ray synchrotron diffraction data. Pair distribution function (PDF) analysis was used to probe the local structure and revealed that the first-neighbour distances of Fe-Fe and Mn-Zn in the 3.0 up to 3.5˚A range are different from the ones usually reported in the literature. For the sample with the best magnetic behaviour, resonant X-ray scattering (RXS) using three energies close to the absorption edges of Mn, Zn and Fe was applied to determine the cation distribution which explained the previous result from PDF analysis.
Size-strain analysis of iron-excess Mn–Zn ferrite nanoparticles using synchrotron diffraction and its correlation with magnetic saturation and isoelectric pH
2018 - ICHIKAWA, RODRIGO U.; PARRA, JOAO P.R.L.L.; MARTINS, MURILLO L.; YOSHITO, WALTER K.; SAEKI, MARGARIDA J.; TURRILLAS, XAVIER; MARTINEZ, LUIS G.
Iron-excess Mn–Zn ferrite nanoparticles were prepared by coprecipitation with sodium hydroxide (NaOH) at different concentrations (0.1, 0.2, 0.5 and 1.0 mol/L). The results of X-ray diffraction (XRD) analysis using Whole Powder Pattern Modeling (WPPM) showed that higher concentrations of NaOH promote crystallite growth and broader dispersion in crystallite sizes. Energy dispersive X-ray spectroscopy indicates that zinc loss is noticeable when [NaOH] ≥ 0.2 mol/L. XRD revealed also a significant less-crystalline phase contribution alongside the main peaks of the nanocrystalline cubic spinel ferrite phase. The less-crystalline fraction is lower for the ferrite obtained with 0.2 mol/L of NaOH, being about 50% and more than 70% for the other samples. Despite of the less-crystalline fraction and the excess of iron, no secondary phases were detected. The Warren curves showed that the concentration of NaOH significantly influences the microstrain in the crystallites, being smaller for the sample obtained with NaOH at 0.2 mol/L. The sample prepared with this condition presented the better properties to be used as magnetic tracer in clinical diagnoses combining small mean crystallite size, low microstrain, which resulted in materials with higher magnetic saturation and high surface charge under blood pH.
Mn-Zn ferrite nanoparticles probed by synchrotron pair distribution function analysis and anomalous X-ray scattering
2017 - ICHIKAWA, R.U.; PARRA, J.P.R.L.L.; VALLCORBA, O.; PERAL, I.; YOSHITO, W.K.; SAEKI, M.J.; TURRILLAS, X.; MARTINEZ, L.G.
Among the numerous applications of Mn1-xZnxFe2O4 nanoparticles we can highlight biomedical applications as magnetic tracer in Alternate Current Biosusceptometry (ACB), Magnetic Resonance Imaging (MRI), for diagnosis of cancer and others diseases as diabetes and Parkinson, whose severity can be monitored by analyzing the disturbances of the gastrointestinal motility [1,2]. Specifically, the former (ACB) method is promising because of its low cost, it is non-invasive method and because it can be conducted without ionizing radiation. Major advances have been achieved by developing a bionanocomposite based on ferrites for the theranostics [3] as well, of breast cancer, by carrying drugs or hyperthermia. Recently, we reported that Mn0.75Zn0.25Fe2.8O4 nanoparticles with different surface charge can be produced precipitating them by NaOH with different concentrations [2]. This behavior is observed if an excess of Iron is introduced to the ferrite. Five samples precipitated with different NaOH concentrations were analyzed by X-ray synchrotron diffraction (XRD) which revealed a less crystalline phase contribution alongside the main peaks of the cubic spinel ferrite phase. Pair Distribution Function (PDF) analysis was used to probe the local structure and showed that Fe-Fe, Mn-Mn and Zn-Zn bond distances in the 3.0 up to 3.5 Å range are different from the ones usually reported in the literature. Lastly, for the sample with best magnetic behavior anomalous X-ray scattering (AXS) using three energies close to the absorption edges of Mn, Zn and Fe was applied to determine its cation distribution complementing the previous result from PDF analysis.
Characterization of Mn0.67Zn0.33Fe2O4 nanoparticles synthesized under different pH
2017 - 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.
The influence of synthesis parameters on the structure and acb response of Mn0.75 Zn0.25FeyO4 ferrite
2016 - NAVARRO, RAPHAELLA; MOURA, TIAGO F.A.; YOSHITO, WALTER K.; ICHIKAWA, RODRIGO; MARTINEZ, LUIZ G.; MATOS, RONALDO V.R.; MIRANDA, JOSE R. de A.; SAEKI, MARGARIDA J.
The interest to use magnetic nanoparticles in biomedicine has increased due to their inducible magnetic properties[1-4]. In the treatment of certain diseases as cancer, it has been used to constitute drug carrier systems[2,3] as well as hyperthermia agents[3,4]. These materials can also be used as a tracer in the diagnosis by Magnetic Resonance Imaging (MRI)[3,4] and Alternating Current Biosuceptometry (ACB)5, which are techniques that do not use ionizing radiation. Neverthless, the sensitivity of these techniques depend on the magnetic susceptibility of tracers. In this work, the ferrite nanoparticles with the composition of Mn0.75Zn0.25FeyO4 (ferrite), where 1.5 ? y ? 2.8, were synthesized by the co-precipitation method and the influence of iron content, reaction time and concentration of precipitating agent on the structure and ACB response was analyzed. It was noted that the synthesis using alkaline metal hydroxide between 0.1 and 0.2 mol/L provides single-phase materials with spinel structure [ICSD 28515 (PDF - 742 402), space group Fd3m]. The higher concentration (0.2 mol/L) leads to materials with higher crystallinity and adequate performance for the ACB technique. The longer the reaction time the greater is the magnetic susceptibility for compositions wherein the iron is in excess (y>2.0). Also, the susceptibility is higher for ferrites with excess of iron.
Densificação de BaZr0,1Ce0,7Y0,1Yb0,1O3-γ para aplicação como eletrólito de Células a Combustível de Óxido Sólido
2015 - SILVA, R.I.V. da; YOSHITO, W.K.; MARTINS, M.L.; ICHIKAWA, R.U.; SANTOS, D.I. dos; MARTINEZ, L.G.; SAEKI, M.J.
BaCeMIIIO3-δ (MIII = metals with valence 3+ as Y, Yb, Gd, etc) is the most investigated proton conductive ceramic to be applied as electrolyte in the electrochemical devices as Solid Oxide Fuel Cell (SOFC). Despite their high conductivity, the low chemical stability in the presence of acidic gases (CO2 and SO2) requires improvements. The stability can be provided by doping with zirconium [1] and the loss in conductivity due to the presence of zirconium can be retrieved by adding yttrium and ytterbium [2]. The conductivity at the grain interface is also a major factor for an efficient electrolyte, so the synthesis is an important step. One of the synthesis methods used to obtain complex stoichiometry materials is Pechini and their variations as EDTA-Citrate method [3]. However, this class of methods have still hurdles to obtain dense materials due to the difficulty to eliminate carbonates. One way to facilitate the elimination of carbonates is to obtain materials with high surface area. The aim of this work is to synthesize BaZr0,1Ce0,7Y0,1Yb0,1O3-δ by citrate-EDTA method and evaluate the influence of pH (~5 and ~8) during the precursor synthesis in order to obtain materials with high surface area. After synthesizing the resins, they were heat treated at: 600ºC/4h and 1000ºC/3h (all in air). The obtained ceramic powders were characterized by TG/DTA, XRD, EDX, FTIR and N2 adsorption at 77K. After, the green ceramic pellets were obtained, they were submitted to the following sintering process: 500ºC/1h, 1000ºC/1h and 1450ºC/3h (all in air). The dense pellets were characterized by XRD, EDX, relative density by Archimedes method, SEM and impedance measurement. Regarding to the powder samples, the TG/DTA results indicated the formation of perovskite phase at the range of 700ºC-1000ºC (endothermic process) and, at same time the carbonate is eliminated (exothermic process). The XRD patterns of materials calcined at 1000ºC/3h showed that EDTA-citrate method provided materials under perovskite type structure when synthesized in boths pHs. The analysis by EDX (materiais obtained in boths pHs and calcined at 1000ºC/3h) confirmed that the compositions are close to the nominal one. The FTIR results indicated the carbonates are still present even calcining at 1000°C/3h, for boths pHs. The N2 adsorption results showed that the materials synthesized in pH~8 exhibited higher surface area than materials synthesized in pH~5 (22 m2/g and 9 m2/g, respectively, for materials calcined at 600ºC/4h). Regarding to the dense materials, the XRD patterns of the pellets synthesized by controlling pH~8 and sintered at 1450ºC/3h showed crystalline structure with higher symmetry (orthorhombic phase) while the XRD patterns of the pellets synthesized at pH~5 showed phase with lower symmetry (monoclinic phase). The analysis by EDX in the samples sintered at 1450ºC/3h confirmed that the composition is close to the nominal one, for boths pHs. The pellets obtained from materials synthetized at pH~8 showed higher relative density than the pellets at pH~5, being 98% and 94%, respectively. The SEM analysis corroborated these results. The impedance spectroscopy showed the total conductivity within the densified material (pH 8) is in the range 11-0,54 mS/cm when measured in wet air at the temperature of 800ºC-400ºC. In other words, considering a current density of 300mA/cm2 and a thickness of 20 m, the overpotential is close to 100 mV at 700oC, showing that the materials prepared by EDTA-citrate method can be used as electrolyte in the intermediate temperature SOFC (IT-SOFC).
Influence of Ph on the densification of BaZrsub(0.1)Cesub(0.7)Ysub(0.1)Ybsub(0.1)Osub(3-'gamma')
2015 - SILVA, I.V. da; YOSHITO, W.K.; MARTINS, M.L.; ICHIKAWA, R.U.; SANTOS, D.I. dos; MARTINEZ, L.G.; CENTENO, M.A.; ODRIOZOLA, J.A.G.; SAEKI, MARGARIDA J.
Size-strain analysis of nanostructured Mn-Zn ferrites using x-ray line profile methods
2015 - ICHIKAWA, R.U.; PARRA, J.P.R.L.L.; MARTINS, M.L.; YOSHITO, W.K.; SAEKI, M.J.; TURRILLAS, X.; MARTINEZ, L.G.