RODRIGO UCHIDA ICHIKAWA

RODRIGO UCHIDA ICHIKAWA

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Influence of temperature on obtaining apatites by sol- gel method
2023 - GARCIA, JOAO I.M.M.; GOMES, ANDERSON M.; ZAMBUZZI, WILLIAN F.; ICHIKAWA, RODRIGO U.; SAEKI, MARGARIDA J.
Calcium phosphate-based ceramics (apatites) are synthetic materials that have a chemical composition similar to bone tissue, which makes them interesting to use as biomaterials [1]. In this work, the apatite precursor sols at concentrations of 0.7 mol/L and 1.4 mol/L are prepared by dissolving calcium nitrate and phosphorus pentoxide in ethanol. The sols are kept at rest for 24 hours for hydrolysis (gelatinization) under room temperature and humidity. After hydrolysis, the resulting gels are dried at 80°C to remove the organic solvent and then calcined under different temperatures (from 500°C to 1200°C, with increments of 100°C) for 8h [2]. The X-ray diffraction analysis of the samples by the Rietveld method indicates that the samples are composed of monoclinic and hexagonal hydroxyapatite (HAp), the former being predominant, and calcium β-triphosphate (TCP)[3] . For the material started from the sol with a concentration of 0.7 mol/L, the hydroxyapatite fraction increases from 28.8% to 66.5% when the calcination temperature increases from 500°C to 800°C. Above this temperature, the fraction of this phase decreases. With a concentration of 1.4 mol/L, the hydroxyapatite fraction decreases from 88.2% to 19.5% progressively with increasing temperature from 500°C to 1200°C. The micrographs revealed the formation of particulate but porous materials that agglomerate without sintering up to a temperature of 900°C, from where the formation of sintered and dense agglomerates is observed. The results of the EDX analysis showed a Ca/P molar ratio of around 1.5 for all materials. The cytotoxicity assay, using pre-osteoblast cells (MC3T3-E1, Subclone 4) by non-direct contact of 24h, showed that cell viability and adhesion did not differ from those of the control. A decrease in viability and adhesion was observed for samples prepared at a concentration of 0.7 mol/L and calcined at temperatures above 900°C.
Caracterização da hidroxiapatita preparada pelo método sol-gel por difração de raios X
2022 - CARRA, M.G.J.; GARCIA, J.I.M.M.; SAEKI, M.J.; ICHIKAWA, R.U.
Cerâmicas a base de fosfato de cálcio são muito estudadas devido a sua aplicação na regeneração e reabilitação óssea. É o constituinte principal da matriz mineral óssea, podendo ser usadas na forma de pó, para reparos, e como revestimentos de implantes. Este trabalho descreve a preparação do pó de hidroxiapatita (Ca10(PO4)6(OH)2, HAp) pelo método sol-gel. O sol precursor é versátil, pois pode ser usado também para revestir implantes como o de titânio. Inicialmente, o sol de HAp nas concentrações de 0,7 mol/L ou 1,4 mol/L em íon metálico é preparado em etanol partindo-se de nitrato de cálcio e pentóxido de fósforo. O sol é mantido em repouso para a hidrólise (gelatinização) em temperatura e umidade ambiente. Em seguida é seca à 80ºC e calcinada sob diferentes temperaturas (de 500ºC à 700ºC) por 8h. Finalmente, as amostras são caracterizadas por difração de raios X (DRX). A identificação de fases e a estimativa do tamanho médio de cristalitos são feitas por meio da análise dos perfis de difração aplicando-se o método de Pawley. Tanto a preparação do precursor nas concentrações de 0,7 mol/L ou 1,4 mol/L como temperaturas de calcinação de 500oC a 700oC proporcionaram hidroxiapatita, sendo que o grau de pureza varia com a temperatura. Esta análise em função da temperatura de calcinação mostra caminhos para obter amostras de hidroxiapatita monofásica. Sua preparação na forma de filmes sobre a superfície do titânio sob condições estudadas neste trabalho contribuirá para melhorar a osseointegração com o implante.
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.
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.
Study of hydration of sulphoaluminate cement by in situ synchrotron diffraction
2017 - ROSSETTO, C.M.; MARTINEZ, L.G.; ICHIKAWA, R.U.; CAREZZATO, G.L.; CARVALHO, A.M.G.; TURRILLAS, X.
The hydration of calcium sulphoaluminate cement mixtures was studied in situ by synchrotron X-ray diffraction at the XRD1 beamline at the Laboratório Nacional de Luz Síncrotron (LNLS – Campinas). The specimens were analyzed in borosilicate glass capillary tubes of 0.7 mm and imbued with deionized water. As the hydration reaction is very fast, the data collection was started after two minutes of mixing with water. The Xray wavelength chosen to get an adequate flux for these short time acquisitions was 1.033258 Å (12 keV), determined with a corundum standard. Diffraction patterns were collected every 35 seconds at temperatures ranging from 40 °C to 55 °C with accuracy better than 0.1 °C attained with a hot air blower. The diffracted signal was collected with an array of 24 Mythen detectors [1]. The diffraction patterns accumulated had appropriate statistics to determine the kinetics of the reaction either by quantitative Rietveld analysis or by fitting isolated diffraction peaks to Gaussian curves as a function of time. The most important phases involved in the hydration are Klein´s salt, also known as Ye’elimite, Ca4(AlO2)6SO4, and gypsum, CaSO4.2H2O to yield Ettringite, Ca6Al2(SO4)3(OH)12·26H2O, phase responsible for the mechanical properties. These studies show the potential of XRD1 beamline to investigate at controlled temperatures in situ fast reactions involving crystalline phases with time resolutions inferior to one minute, which is ideal for the hydration of cementitious mixtures. The series of diffraction patterns collected for one and half hour are shown in Figure 1(a) and (b). In Figure 1(c) the evolution of the relative proportions of crystalline phases can be seen. Non-crystalline phases such as CSH gel or Al(OH)3 (gibbsite) are not taken in consideration [2]. The figures clearly show that the ettringite formation happens in two stages, the second one starting after approximately forty minutes. It is also interesting to notice that this stages seem to coincide with the depletion of Ca2SiO4 (C2S) for the first stage and the depletion of Ca3SiO5 (C3S) for the second one.
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).
Propriedades de armazenamento de hidrogênio do composto tife nanoestruturado, obtido a partir da síntese por reação de misturas de pós de TiH2 e Fe processadas por moagem de alta energia
2016 - FALCAO, R.B.; DAMMANN, E.D.C.C.; ROCHA, C.J.; ICHIKAWA, R.U.; DURAZZO, M.; MARTINEZ, L.G.; LEAL NETO, R.M.
Neste trabalho investigaram-se as propriedades de armazenamento de hidrogênio do composto TiFe, sintetizado a partir da reação sob vácuo de misturas dos pós de TiH2 e de Fe processadas por moagem de alta energia. O TiH2 foi escolhido como precursor, no lugar do Ti, em razão de sua fragilidade, benéfica para a diminuição da aderência dos pós no ferramental de moagem, um problema recorrente quando se processam misturas de pós de Ti e Fe. A composição das amostras para moagem da mistura dos pós de TiH2 e Fe seguiu a proporção em massa prevista pela estequiométrica do composto TiFe (50:50). As moagens foram realizadas em um moinho do tipo planetário em intervalos de tempo que variaram entre 5 e 40 horas, sob atmosfera de argônio de elevada pureza. Em todos os experimentos foram mantidos constantes a rotação do prato do moinho, a quantidade de amostra, o diâmetro e o número de bolas. As amostras moídas foram caracterizadas por calorimetria exploratória diferencial (DSC), termogravimetria (TG), microscopia eletrônica de varredura (MEV) e difração de raios X (DRX). Apenas TiH2 e Fe foram observados nas amostras moídas, com um grau crescente de refino microestrutural em função do aumento do tempo de moagem. O composto TiFe nanoestruturado (tamanho de cristalito entre 12,5 e 21,4 nm) foi obtido de forma majoritária em todas as amostras após a reação de síntese promovida por um aquecimento até 873K sob vácuo. As amostras reagidas foram caracterizadas por microscopia eletrônica de transmissão (MET) e DRX. Um equipamento do tipo Sieverts, de construção própria, foi utilizado para levantar curvas termodinâmicas de absorção e dessorção de hidrogênio no modo dinâmico (fluxo constante de hidrogênio). Todas as amostras absorveram hidrogênio à temperatura ambiente (~298K) sem a necessidade de ciclos térmicos de ativação. Uma significativa melhora nas propriedades de armazenamento de hidrogênio, em relação às cinéticas de absorção e dessorção de hidrogênio associadas ao monohidreto de TiFe (TiFeH), foi observada na amostra moída por 10 horas. Observou-se neste caso, entretanto, uma significativa perda na capacidade reversível de armazenamento (de até ~31%). Os platôs de absorção e dessorção de hidrogênio à temperatura ambiente, da amostra moída por 10 horas, foram de aproximadamente 0,8 e 0,35MPa, respectivamente. A capacidade máxima de armazenamento foi de 0,764% em massa de hidrogênio (H:M~0,396), sob pressão de até 1,1MPa, com reversão de até 0,913% em massa de hidrogênio (H:M~0,474), sob pressão de até 0,1MPa. Em relação à cinética de absorção e dessorção de hidrogênio, foram observadas as taxas máximas de 1,34 e 2,12cm3/g.min., respectivamente. Tais resultados foram atribuídos à expansão volumétrica observada na fase TiFe e à uma significativa quantidade de TiH2 livre formado após a primeira absorção de hidrogênio pela amostra.
In situ hydration of sulphoaluminate cement mixtures monitored by synchrotron X-ray diffraction
2016 - ROSSETTO, C.M.; ICHIKAWA, R.U.; MARTINEZ, L.G.; CAREZZATO, G.L.; CARVALHO, A.M.; TURRILLAS, X.
The hydration of calcium sulphoaluminate cement mixtures was studied in situ by synchrotron X-ray diffraction at the XRD1 beamline of the Laboratório Nacional de Luz Síncrotron (LNLS – Campinas). The specimens were analyzed in borosilicate glass capillary tubes of 0.7 mm and imbued with deionized water. As the hydration reaction is very fast, the data collection was started after two minutes of mixing with water. The X-ray wavelength chosen to get an adequate flux for these short time acquisitions was 1.033258 Å, determined with a corundum standard. Diffraction patterns were collected every 35 seconds at temperatures ranging from 40°C to 55°C with accuracy better than 0.1°C attained with a hot air blower. The diffracted signal was collected with an array of 24 Mythen detectors. The diffraction patterns accumulated had appropriate statistics to determine the kinetics of the reaction either by quantitative Rietveld analysis or by fitting isolated diffraction peaks to Gaussian curves as a function of time. The most important phases involved in the hydration are Klein´s salt, also known as Ye’elimite, Ca4(AlO2)6SO4, and gypsum, CaSO4.2H2O to yield Ettringite, Ca6Al2(SO4)3(OH)12·26H2O, phase responsible for the mechanical properties. These studies show the potential of XRD1 beamline to investigate at controlled temperatures in situ fast reactions involving crystalline phases with time resolutions inferior to one minute, which is ideal for the hydration of cementitious mixtures.
In situ hydration of sulphoaluminate cement mixtures monitored by synchrotron X-ray diffraction
2016 - TURRILLAS, X.; MARTINEZ, L.G.; ROSSETTO, C.M.; ICHIKAWA, R.U.; CARVALHO, A.M.; CAREZZATO, G.L.
The hydration of calcium sulpho-aluminate cement mixtures was studied in situ by synchrotron X-ray diffraction at the XRD1 beamline of the Laboratório Nacional de Luz Síncrotron (LNLS) in Campinas, SP. The powder specimens were introduced in borosilicate glass capillary tubes of 0.7 mm of internal diameter and imbued with deionized water. As the hydration reaction is very fast the capillaries were placed on the goniometer and the data collection was started after two minutes of mixing with water. The X-ray energy chosen to get an adequate flux for these short time acquisitions was 12 keV or more precisely 1.033258 Å, determined with polycrystalline corundum standard. Diffraction patterns were collected sequentially every 35 seconds for several hours at temperatures ranging from 40 degC to 55 degC with an accuracy better than 0.1 degC attained with the help of a hot air blower. The diffracted signal was collected with an array of twenty-four Mythen detectors at 760 mm from the capillary tube. The diffraction patterns had appropriate statistics to determine the kinetics of the reaction either by quantitative Rietveld analysis or by fitting isolated diffraction peaks to Gaussian curves as a function of time. The most important phases involved in the hydration are Klein´s salt, also known as Ye’elimite, Ca4(AlO2)6SO4, and gypsum, CaSO4.2H2O to yield Ettringite, Ca6Al2(SO4)3(OH)12·26H2O, phase responsible for the mechanical properties.