OSMAR FLAVIO DA SILVEIRA LEITE NETO
2 resultados
Resultados de Busca
Agora exibindo 1 - 2 de 2
Resumo IPEN-doc 28567 Cd impurities in Vanadium oxides2021 - BURIMOVA, ANASTASIA; LEITE NETO, OSMAR F.; BOSCH-SANTOS, BRIANNA; CORREA, EDUARDO L.; PEREIRA, LUCIANO F.D.; SALES, TATIANE S.N.; RIBEIRO JUNIOR, IBERE S.; COSTA, MESSIAS S.; COSTA, CLEIDILANE; DANG, THANH T.; ZYABKIN, DMITRY; VAN STIPHOUT, KOEN K.F.; GERAMI, ADELEH M.; CORREIA, JOAO M.; SCHELL, JULIANA; CARBONARI, ARTUR W.The number of metastable phases, the capriciousness at changing external conditions, and lack of accurate description of local behavior already resulted in severe misinterpretation of experimental outcomes for vanadium oxides[1–3]. The scope of already implemented and potential applications of vanadium oxides is, indeed, impressive, particularly as a battery cathode for energy storage[ 4]. Doping is widely exploited as a means of application-oriented tuning of the material properties. The properties of each particular phase may be tuned by doping to satisfy specific requirements and/or improve the functional performance. In the work here reported, electric quadrupole interaction on 111mCd nuclei implanted in vanadium pentaoxide doped with different concentrations of Cd were measured with time-differential perturbed angular correlations (TDPAC). Pure V2O5 as well as doped with 1%, 5%, and 10% of Cd were measured at different temperatures. To correlate the results with the possible formation of different phases and compounds, samples of VO2, CdV2O6, and Cd2V2O7 were also measured. The intention is to provide a comprehensive description, at an atomic level, of the doping effects on the local crystal structure and the electronic structure around the impurity and the consequences on the properties of the host oxides. Preliminary results show that the probability of formation of cadmium vanadates is low but the temperature and atmosphere of measurements have an important effect on the local scale.Resumo IPEN-doc 27308 RE-doped Fe3O4 (RE = Eu, Gd, Er) nanoparticles for nanothermometry2019 - CORREA, E.; BOSCH-SANTOS, B.; SALES, T.; CABRERA-PASCA, G.; CORREA, B.S.; NETO, O.F.; CARBONARI, A.W.; OLESHKO, V.; DENNIS, C.Temperature affects every physical system, chemical reaction, and biological process. A new method, magnetic nanothermometry, is being explored to measure temperature throughout a volume. This method uses large changes in magnetization as function of temperature, which cannot be obtained with current magnetic nano-objects (MNO). To get a large magnetization change we have examined the magnetic properties of RE-doped Fe3O4 (RE = Eu, Gd, Er) MNO. Samples were synthesized by co-precipitation. For the doped material, RE+3 were chosen in order to replace the Fe+3 in the (Fe+2)(Fe+3)2O4 structure. Structural characterization was performed by X-ray diffraction and transmission electron microscopy. Hyperfine interaction parameters as a function of temperature (300 K to 873 K) were obtained by perturbed angular g-g correlation (PAC) spectroscopy using 111In(111Cd) as probe nuclei. To fit the PAC spectra, the 111Cd probes were considered to occupy three sites: tetrahedral, octahedral, and a third site where the probes are located at the nanoparticle surface [1]. The hyperfine magnetic field Bhf was calculated using the Larmor equation, and its behavior as a function of temperature follows a Brillouin-type transition. For example, the Curie temperature (TC) obtained for 5% Er-doped was approx. 846 K (FIG. 1), which is higher than the expected TC for pure Fe3O4 (approx. 722 K) [2]. Magnetization as a function of temperature shows a 70 % change in magnetization around 100 K for Er-doped Fe3O4 (FIG.2), which is an improvement in temperature on pure Fe3O4 (below 50 K) [3]. Current work is focused on correlating the temperature range in which the magnetization change occurs and determining if it depends on the dopant element.