SILAS CARDOSO DOS SANTOS

SILAS CARDOSO DOS SANTOS

Página do item completo

Resultados de Busca

Agora exibindo 1 - 5 de 5

Correlation between zeta potential and electron paramagnetic resonance of thulium, europium co-doped yttria based suspensions
2024 - SANTOS, S.C.; RODRIGUES JUNIOR, O.; CAMPOS, L.L.
The formation of advanced ceramic components with homogeneous microstructure and functional characteristics demands a suitable control of particle dispersion. Thus, the characterization of particle stability as immersed in a liquid medium is important. The present paper reports an approach to evaluate the stability of europium, thulium co-doped yttria (YET) nanoparticles by a correlation between zeta potential and Electron Paramagnetic Resonance (EPR) techniques. Based on results, YET suspensions exhibited high stability apart from pH 10, while their isoelectric point presented a slight variation from pHIEP 8.5 to 9.2 according to thulium content 0 and 2 at.%, respectively. The peak-to-peak amplitude of EPR spectra of the YET suspensions increased as pH shifted toward alkaline condition, following zeta potential curves features. The present achievements are very useful parameters to form stable suspensions based on rare-earth oxides and to advance toward new materials for radiation dosimetry.
Building up europium thulium co-doped yttria nanoparticles with electron paramagnetic resonance response by colloidal synthesis
2023 - SANTOS, SILAS C. dos; RODRIGUES JR., ORLANDO; CAMPOS, LETICIA L.
In the radiation dosimetry field the research for new materials is a continuos demand with the aim to provide highly improvement procedures where ionizing radiation is used. Considering this challenge, the present work reports the colloidal synthesis of europium-thulium-co-doped yttria powders (YET) and evaluates the dopants effect on the promotion of EPR response of yttria. The powdered compositions prepared with up to 2at.%Tm and 2at.%Eu (at.%, atomic percentage) were evaluate by XRD, PCS, SEM, and EPR. Based on the results, the proposed synthesis method provided ceramic powders with cubic C-type form and mean particle size (d50) less than 160nm. The most significant EPR dose-response was noticed for the powdered composition prepared with 0.5at. %Tm (YET0.5) as irradiated with 5kGy (60Co). These findings are key parameters to advance toward the formation of new materials for radiation dosimetry.
Colloidal processing of thulium-yttria microceramics
2022 - SANTOS, S.C.; RODRIGUES JUNIOR, O.; CAMPOS, L.L.
The development of new dosimetric materials is essential for the safe and effective use of nuclear technology. In the present study, an eco-friendly bio-prototyping approach was developed for preparing thulium-yttria microceramics with potential applications in radiation dosimetry. Micro-powder compacts were obtained by casting colloidal thulium-yttria suspensions prepared with 20 vol% particles in thin-walled tube templates. Samples were sintered at 1600 °C for 2 h under the environmental pressure and atmosphere to obtain thulium-yttria microceramics with dimensions of 3.33 ± 0.01 mm × 2.27 ± 0.01 mm (height × diameter), as well as a cubic C-type structure, pycnometric density of 4.79 g cm−3 (95.61% theoretical density), and surface microstructure comprising hexagon-like grains bonded at the boundaries. The use of thulium as an activator of yttria greatly improved the electron paramagnetic resonance (EPR) response of the microceramics, where the main EPR peak (p1) was recorded at 351.24 mT and the g factor was 2.0046. The innovative findings obtained in this study may facilitate the production of new solid state dosimeters.
EPR response of yttria micro rods activated by europium
2018 - SANTOS, S.C.; RODRIGUES JUNIOR, O.; CAMPOS, L.L.
Rare earth (RE) materials present excellent properties, which importance is recognized worldwide. Innovation approaches in energy, medicine, communication, transportation, militarism, and radiation dosimetry consist in RE based materials. As yttrium oxide (Y2O3) exhibits intrinsic lattice characteristics that enable doping with others RE elements (Y2O3:RE), new materials with promising characteristics can be developed. This work aims to evaluate EPR response of europium-yttria (Y2O3:Eu) rods obtained by bio-prototyping. Ceramic rods containing up to 10 at.%Eu were irradiated with gamma doses from 0.001 to 150 kGy and evaluated by Electron Paramagnetic Resonance (EPR) at room temperature with X-band EPR. Based on results, Y2O3:Eu rods with 2 at.%Eu exhibited the most significant response, in which linear behavior arose from 0.001 up to 50 kGy. Fading and thermal annealing evaluations revealed that 2 at%.Eu improved dosimetric characteristics of yttria remarkably. These innovative findings afford that Y2O3:Eu is a promising material for radiation dosimetry.
EPR dosimetry of yttria micro rods
2018 - 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.