ANASTASIA BURIMOVA
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Artigo IPEN-doc 25614 Low temperature synthesis of pure and Fe-doped HfSiO4: Determination of Si and Fe fractions by neutron activation analysis2019 - SALES, T.N.S.; BOSCH-SANTOS, B.; SAIKI, M.; BURIMOVA, A.; PEREIRA, L.F.D.; SAXENA, R.N.; CARBONARI, A.W.A new method of synthesis of hafnium silicate HfSiO4 (also known as hafnon) is reported. We observed a selfcontrolled incorporation of SiO2 from the quartz tube in which a sample of hafnium oxide nanoparticles was heated. This approach was then adapted to Fe-doped hafnon production. Sample structure, morphology and composition were characterized by X-ray diffraction, electron microscopy and neutron activation analysis. Diffraction data has shown that lattice parameters of doped HfSiO4 thus obtained are very close to those previously known for bare hafnon. The hafnon-like phase stabilized at T=900 °C which is about 500 °C lower than the corresponding transition of bare bulk hafnium silicate. The fractions of Si and Fe in the composite matrices were determined with neutron activation analysis. These results completed by X-ray diffraction data allowed to assume that (i) Fe initially substituted Hf in the HfO2 lattice; (ii) there was no migration of iron atoms from Hf to Si sites at the formation of hafnon-like phase; (iii) doped and undoped hafnium oxide has taken as much Si from the quartz as was needed for the arrangement of Fe1-xHfxSiO4 tetragonal system, 0≤x<0.2. Our results are consistent with those obtained for similar materials, such as metal (Fe,V) doped zircon, where the dopant also demonstrated catalytic effect on phase stabilization.Resumo IPEN-doc 23266 Determination of Si content in Fe-doped HfSiO4 nanoparticles by neutron activation analysis2017 - SALES, T.S.N.; BOSCH-SANTOS, B.; SAIKI, M.; PEREIRA, L.F.; CARBONARI, A.W.; SAXENA, R.N.; BURIMOVA, A.New synthesis method of Fe-doped hafnium silicate nanoparticles (NPs) with tetragonal structure is reported. The procedure implies auto-controlled incorporation of Si from the quartz to the iron-doped hafnium oxide NPs. X-ray diffraction data has shown that lattice parameters of Fe-HfSiO4 thus obtained are very close to those previously known for hafnon. It was established that the hafnon-like phase has stabilized at T=1173K which is ~500K lower than the corresponding transition of bare bulk hafnium silicate. The fractions of Si and Fe in the composite matrix were evaluated via neutron activation analysis (NAA). Delayed gamma NAA results allowed to assume that (i) Fe initially substituted Hf in the HfO2 lattice; (ii) there was no migration of iron atoms from Hf to Si sites throughout the formation of hafnon-like phase; (iii) Fe-doped hafnium oxide has taken as much Si from the quartz as was needed for the arrangement of Fe1-x-Hf x SiO4 tetragonal system. Our results are consistent with those observed for similar materials, such as metal (Fe,V) doped zircon, where metal has also demonstrated catalytic effect on phase stabilization.