CHIEKO YAMAGATA
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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 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.Artigo IPEN-doc 20089 Yttria nettings by colloidal processing2014 - SANTOS, S.C.; ACCHAR, W.; YAMAGATA, C.; MELLO CASTANHO, S.