CHIEKO YAMAGATA
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Artigo IPEN-doc 28662 Three routes for the synthesis of the bioceramic powder of the CaO-MgO-SiO2 system2022 - YAMAGATA, CHIEKO; LEME, DANIEL R.; RODRIGUES, VANESSA G.; ERETIDES, GABRIEL T.; RODAS, ANDREA C.D.We report three routes for the synthesis of CaO-MgO-SiO2 (CMS) bioceramic powder using different Si sources and synthesis procedures. The ceramic powders were synthesized from Na2SiO3 waste solution by the sol-gel process combined with co-precipitation (synthesis route I and synthesis route II), and from TEOS (tetraethyl orthosilicate) by conventional sol-gel (synthesis route III). Ceramic powders of the CMS multiphase system were obtained, including diopside, wollastonite, akermanite, monticellite and merwinite, which are suitable for application as biomaterial. These powders were sintered at 1200 °C for 2 h to obtain the CMS ceramics. The ceramics mostly contained diopside and wollastonite crystalline phases. Those ceramics when submitted to cytotoxicity tests revealed to be non-cytotoxic, according to ISO10993-5:2009. The ceramics were tested for in vitro bioactivity while soaked in simulated body fluid (SBF) solution. After 14 days, the presence of hydroxyapatite particles on the surface of ceramics was confirmed by Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) micrographs. The surfaces were completely covered with hydroxyapatite, after 21 days. In summary, CaO-MgO-SiO2 (CMS) ceramic powder derived from three routes of synthesis have potential application in the biomedical area. However, further in-vitro and in-vivo studies are needed.Artigo IPEN-doc 25843 Use of waste water glass as silica supplier in synthesis of pure and Mg-doped lanthanum silicate powders for IT-SOFC application2019 - YAMAGATA, C.; LEME, D.R.; CASTANHO, S.R.H.M.Water glass in alkali solution (Na2SiO3/NaOH) an abundant effluent, generated in the alkaline fusion of zircon sand, represents a potential silica source to be converted in useful silica technological application. Actually, the generation of energy by environmental-friendly method is one of the major challenges for researchers. Solid Oxide Fuel Cells (SOFC) is efficient and environmentally clean technique to energy production, since it converts chemical energy into electrical power, directly. Apatite-type lanthanum silicates are promising materials for application as an electrolyte in intermediate temperature SOFC (IT-SOFC) because of their higher ionic conductivity, in temperatures of range 600–700 °C, than conventional zirconia electrolytes. In this work, pure (La9,56(SiO4)6O2,34) and Mg-doped (La9,8Si5,7Mg0,3O26,4) lanthanum silicate were synthesized, from that rich effluent. Using the sol-gel followed by precipitation method, the single crystalline apatite phase of both silicates was obtained by thermal treatment at 900 °C of their precursors. Sintered ceramic samples reached density of higher than 90%.Artigo IPEN-doc 25792 Micrograded ceramic-metal composites2019 - RESTIVO, THOMAZ A.G.; BECCARI, RAFAEL F.; PADILHA, WELLINGTON R.; DURAZZO, MICHELANGELO; TELLES, VICTOR B.; COLETI, JORGE; YAMAGATA, CHIEKO; SILVA, ANTONIO C. da; SUZUKI, EDUARDO; TENORIO, JORGE A.S.; MELLO-CASTANHO, SONIA R.H.The article shows new designed cermets and processes concerning primary to applications as thermal insulation materials with low emissivity. A new projected microstructure was obtained where dense regions (micropellets) rest inside the main porous pellet. The feature resembles a frozen hypercube, therefore such architecture is called hyper-pellet/ cermet. The processing method to obtain the hyper-cermet is based on sequential tape castings and sintering techniques. Ni-zirconia lamellae were prepared by a special mechanochemical process followed by sintering, which remain inside the main pellets as a dense region. The whole pellet is turned to be porous by employing pore-forming additives. All the constituents and porosity shapes are aligned along the disc/ flake planes. Thermal conductivity is estimated for the materials up to 800 °C by a flash diffusivimeter. Ceramographic analyses show graded density regions with directional constituents and pores. Applications of such materials are foreseen as temperature insulation materials and thermal radiation shields.Artigo IPEN-doc 22838 Processing, microstructure and thermoluminescence response of biomorphic yttrium oxide ceramics2016 - SANTOS, S.C.; YAMAGATA, C.; CAMPOS, L.L.; MELLO-CASTANHO, S.R.H.The present work reports a fast-direct bio-prototyping process using Luffa Cylindrica vegetable sponge to produce biomorphic yttrium oxide ceramics with reticulated-porous architecture and thermoluminescence response. Processing parameters as rheology of yttrium oxide suspensions, bio-template surface treatment and thermal decomposition of bio-template were investigated. Shear thinning suspensions of 30 vol% yttrium oxide with apparent viscosity of 243mPa.s provided a successful impregnation of samples, whereby bio-templates with smooth ceramic layer and hierarchical reticulated architecture were formed. By thermal treatment at 1600 degrees C for 2 h biomorphic yttrium oxide ceramics with porous microstructure and TL response at 150 degrees C and lambda=550 nm were produced. The proposed fast direct bio-prototyping process is suitable for the production of ceramic components with complex shape and demonstrates potential for general applicability to any bio-template. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.Artigo IPEN-doc 21769 Bio-prototyping and thermoluminescence response of cellular rare earth ceramics2016 - SANTOS, S.C.; YAMAGATA, C.; CAMPOS, L.L.; MELLO CASTANHO, S.R.H.The use of renewable materials is essential toward green economy. Vegetable structures are abundant, exhibit complex hierarchically built shape and an architecture that is promising to form functional materials. In this work using a mixture of rare earth oxides, which contain around 57 wt% yttrium oxide, cellular ceramics by bio-prototyping from the vegetable sponge Luffa cylindrica were produced and the thermoluminescence response was evaluated. By colloidal processing aqueous suspensions with 25 vol% solids content, pH 10, 1 wt% deffloculant and 0.2 wt% binder exhibited shear thinning behavior and apparent viscosity suitable for replica method. By thermal treatment at 1600 ◦C for 2 h in air biomorphic rare earth ceramics with dense microstructure and reticulated architecture were produced.