SILAS CARDOSO DOS SANTOS
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Artigo IPEN-doc 24787 EPR dosimetry of yttria micro rods2018 - SANTOS, S.C.; RODRIGUES JUNIOR, O.; CAMPOS, L.L.The use of rare earths (RE) as dopant of materials has led the development of advanced materials for many applications such as optical tracers, special alloys, semiconductors, as well as radiation dosimeters. The development of new dosimetric materials based on REs is a great challenge in innovation of materials. Yttria (Y2O3) presents luminescent proprieties and is a promising material for radiation dosimetry. The present paper aims to evaluate paramagnetic defects of Y2O3 rods obtained via bio-prototyping by using Electron Paramagnetic Resonance (EPR) technique at room temperature. Ceramic rods were irradiated with gamma doses from 0.001 to 150 kGy and evaluated by EPR at room temperature with X-band EPR. According to EPR results, as sintered samples exhibited an EPR signal with principal g tensor of 2.020 and maximum line width around 2.3 mT, which is ascribed to interstitial oxygen ion. Dose response behaviour exhibited two distinct dose ranges, one is from 1 to 100Gy and the second is from 0.1 to 70 kGy. Thermal annealing approaches reveal that defect centres of yttria decay significantly at high temperature. These innovative results make Y2O3 a promising material for radiation dosimetry.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.