BRUNO SANTOS CORREA
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Artigo IPEN-doc 30205 Cobalt doping effects in zinc oxide2024 - PEREIRA, LUCIANO F.D.; FERREIRA, WANDERSON L.; CORREA, BRUNO S.; COSTA, MESSIAS S.; COSTA, CLEIDILANE S.; FILHO, ARNALDO A.M.; SALES, TATIANE S.N.; BOSCH-SANTOS, BRIANNA; SCHELL, JULIANA; BURIMOVA, ANASTASIA; SAXENA, RAJENDRA N.; CABRERA-PASCA, GABRIEL A.; CARBONARI, ARTUR W.In this paper, we investigate the solubility effects of Co in ZnO (Zn1−xCoxO, where x = 0, 0.03, 0.05, 0.1, 0.2, 0.25, 0.4, 0.8, and 1) by combining the results of perturbed angular correlation (PAC) spectroscopy using highly diluted 111Cd as probe nuclei and ab initio calculations based on spin-density functional theory (SDFT). This combined approach enables us to characterize the local structure around Cd ions, where, through PAC technique, it was possible to measure the EFG as a function of temperature and Co concentration and thereby monitor the changes in the structure and the Co solubility threshold in ZnO and the ZnO/CoO/Co3O4 mixed phase. The full-potential linear augmented plane wave plus local orbital (APW+lo) formalism were used here to describe the electronic structure of the supercells, including the atomic relaxations. These Ab initio calculations show an interesting behavior of the Cd and Co impurity levels in the band structure of ZnO, which explains the experimental results in terms of the origin of EFG and the evidence of ferromagnetic response.Artigo IPEN-doc 30219 Investigation of Ni/Ni3C nanoparticle synthesis for application as a catalyst in carbon nanostructure growth2023 - SILVA, CRYSTIAN W.C.; CABRERA-PASCA, GABRIEL A.; SOUZA, KATIUSSE S.; COSTA, CLEIDILANE S.; COSTA, MESSIAS S.; CORREA, BRUNA S.; FERREIRA, WANDERSON L.; FREITAS, RAFAEL S.; CARBONARI, ARTUR W.; OTUBO, LARISSAThe synthesis of functional Ni/Ni3C nanoparticles has attracted significant interest, especially in the field of electrocatalysis, where these promising nanoparticles are employed to develop sophisticated electrocatalysts, particularly for hydrogen production through the hydrogen evolution reaction. However, the significant reactivity of these systems makes them susceptible to degradation, compromising their catalyst performance. One solution explored to mitigate this problem involves the catalytic growth of carbon nanostructures to encapsulate and protect these nanoparticles. The mechanisms for the formation of carbon nanostructures from nanoparticles remain the subject of this study. Among the reported processes, the annealing of nanocatalysts has been described as a highly effective method for producing such systems. This process is influenced by parameters, such as the temperature, atmosphere, and structural and morphological characteristics of the nanocatalysts. In the work reported here, we evaluated the influence of different ligand pairs (oleylamine/oleic acid and oleylamine/palm kernel oil) on the structural, morphological, and magnetic properties of Ni/Ni3C nanoparticles obtained through thermal decomposition at 240 °C for 3 h. Additionally, we investigated the impact of annealing in a nitrogen atmosphere on the structural properties of these nanoparticles and the growth of carbon nanostructures as a protective mechanism. The analyses include conventional techniques such as X-ray diffraction, transmission electron microscopy (TEM), magnetization measurements, and thermogravimetric analysis with differential scanning calorimetry. Additionally, local analysis was conducted using perturbed angular correlation spectroscopy (PAC) across a broad temperature range (30–693 K), utilizing the radioactive tracer 111In(111Cd) for these measurements. The characterizations revealed that palm kernel oil contributes to the formation of nanoparticles with a higher Ni3C content, a broader size distribution, and a lower saturation magnetization. The PAC measurements in the range of 30–50 K, along with density functional theory calculations, indicated the absence of the Ni-hcp phase in the nanoparticles, a topic frequently discussed in the literature. Moreover, the presence of Ni3C regions with carbon deficiency was identified, characterized by a quadrupole frequency (νQ) of 23 MHz and a hyperfine field (Bhf) of 1 T. The temperature-dependent local analysis, combined with thermal analysis and TEM measurements, confirmed the development of carbon nano-onions around the nanoparticles during thermal treatment above 695 K in a nitrogen atmosphere. This observation demonstrates that nanoparticles obtained with palm kernel oil, which has the highest Ni3C content, offer superior encapsulation of Ni nuclei through these graphitic nanostructures.Resumo IPEN-doc 30169 Comparative local analysis of Ni/Ni3C nanoparticles synthed with oleylamine/oleic acid and oleylamine/palm kernel oil ligand pairs2023 - SILVA, CRYSTIAN W.C. da; OTUBO, LARISSA; SOUZA, KATIUSSE S. de; CARBONARI, ARTUR W.; CORREA, BRUNO S.; FREITAS, RAFAEL S. de; PASCA, GABRIEL A.; COSTA, CLEIDILANE S.In recent decades, Ni/Ni3C nanoparticles have been a topic of interest, especially for their catalytic and magnetic properties, promising as electrocatalysis, for example [1]. These systems are usually obtained by chemical methods, in the presence of ligands responsible for controlling their structure and morphology [2]. In this work, we carried out a comparative study of the hyperfine interactions occurring in Ni/Ni3C nanoparticles, synthed by thermal decomposition in the presence of oleylamine/oleic acid and oleylamine/palm kernel oil ligand pairs, at 513 K, for 3 hours. The local analysis was performed using perturbed correlation spectroscopy (PAC) in the temperature range from 30K to 300K, using the 111Cd probe, implanted in the samples by diffusion, during the synthesis. The parameters of the hyperfine interactions were compared to the results obtained by XRD, TEM and magnetization, indicating the obtainment of Ni/Ni3c nanoparticles of the core-shell type, showing a higher Ni3C content, greater distribution and lower saturation magnetization for nanoparticles synthed with palm kernel oil compared to those obtained with oleic acid. In addition, the hyperfine parameters showed the existence of regions with a quadrupole frequency of 24 MHz and a magnetic hyperfine field of 1T in both samples, which may be indicative of carbon-deficient Ni3C regions, predicted in the literature [3].Resumo IPEN-doc 29751 Magnetic properties of Er-doped Fe3O4 nanoparticles studied by perturbed angular spectroscopy2019 - CORREA, E.L.; BOSCH-SANTOS, B.; SALES, T.S.N.; CABRERA-PASCA, G.A.; CORREA, B.S.; CARBONARI, A.W.; OLESHKO, V.P.; DENNIS, C.L.Artigo IPEN-doc 29041 Local crystalline structure of doped semiconductor oxides characterized by perturbed angular correlations2022 - BURIMOVA, ANASTASIA; CARBONARI, ARTUR W.; LIMA, NICOLE P. de; MIRANDA FILHO, ARNALDO A.; SOUZA, ALEXANDRE P. dos S.; SALES, TATIANE da S.N.; FERREIRA, WANDERSON L.; PEREIRA, LUCIANO F.D.; CORREA, BRUNO S.; SAXENA, RAJENDRA N.Doping semiconductor oxides with trace amounts of non-native elements can improve their properties such as bandgap and conductivity. The lack of local techniques makes the precise characterization of these materials difficult. Among the few techniques capable of providing local characterization, those based on hyperfine interactions at probe nuclei have the advantage of being well established, probing the material homogeneously and completely, thus investigating different regions of material. Some of these techniques are also quite sensitive even at extremely low dopant concentrations. The perturbed angular correlation technique, combined with first-principles calculations, has recently been shown to be a powerful method for characterizing doped semiconductor oxides. In this paper, we present a brief review of the unique information extracted from the semiconductor investigation with such a complex approach, including semiconductor oxides doped with cadmium and other elements. A strong relationship between the local environment, including electronic structure, and the nature of the dopant and the native element of the doped oxides is also shown.Artigo IPEN-doc 28524 Magnetic and structural properties of the intermetallic Ce(1−x)LaxCrGe3 series of compounds2021 - BOSCH-SANTOS, B.; CABRERA-PASCA, G.A.; CORREA, E.L.; CORREA, B.S.; SALES, T.N.S.; MOON, K-W.; DENNIS, C.L.; HUANG, Q.; LEAO, J.B.; LYNN, J.W.; CARBONARI, A.W.The Ce(1−x)LaxCrGe3 (x = 0, 0.19, 0.43, 0.58, and 1) intermetallic compound system has been investigated by magnetization measurements and neutron scattering techniques to determine the effect of La doping on the magnetic ordering and exchange interaction between Cr ions. The structural and magnetic characterization in this series was first verified by x-ray diffraction and bulk magnetization measurements. The samples exhibit the known hexagonal perovskite structure (P63/mmc space group) and have a single magnetic phase according to magnetizationmeasurements. In this paper, the ferromagnetic ordering temperature for Cr evolves smoothly from a range of 68 K to 77 K for CeCrGe3 to a range of 91 K to 96 K for LaCrGe3 as La replaces Ce. Magnetization results indicate the formation of domain walls below the transition temperature for all Ce(1−x)LaxCrGe3 systems investigated. Neutron results indicate ordered magnetic Cr moments aligned along the c axis for the x = 1 LaCrGe3 system, as well as for x = 0.19, 0.43, and 0.58, which contrasts with the x = 0 CeCrGe3 where the moments order in the ab plane.Artigo IPEN-doc 28161 Crystalline and magnetic properties of CoO nanoparticles locally investigated by using radioactive indium tracer2021 - SANTOS, RENATA V.; CABRERA-PASCA, GABRIEL A.; COSTA, CLEIDILANE S.; BOSCH-SANTOS, BRIANNA; OTUBO, LARISSA; PEREIRA, LUCIANO F.D.; CORREA, BRUNO S.; EFFENBERGER, FERNANDO B.; BURIMOVA, ANASTASIA; FREITAS, RAFAEL S.; CARBONARI, ARTUR W.We herein report a comprehensive investigation on the magnetic, structural, and electric properties of CoO nanoparticles with different sizes by local inspection through hyperfine interactions measured in a wide range of temperatures (10–670 K) by using radioactive 111In(111Cd) tracers with the perturbed angular correlations technique. Small cobalt oxide nanoparticles with the characteristic size of 6.5 nm have been prepared by the wet chemical route that turned out to be essential to incorporate radioactivity tracers during nucleation and growth of the particles. Nanocrystalline samples with 22.1 nm size were obtained by thermal treatments under low pressure of helium at 670 K. The hyperfine data were correlated with X-ray diffraction, ZFC–FC magnetic measurements, and transmission electron microscopy to describe the structure, magnetic properties, size, and shape of samples. An analysis of the temperature evolution of hyperfine parameters revealed that the structural distortion and the magnetic disorder in the core and on the surface layer play an important role in the magnetic behavior of CoO nanoparticles.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.Resumo IPEN-doc 27090 Hyperfine interaction study of iron oxide nanoparticles coated with Amazon ucuúba, bacaba and açaí, oils by PAC spectroscopy using 111In-111Cd nuclear probe nuclei2019 - CORREA, B.S.; COSTA, M.S.; SENA, C.; CABRERA-PASCA, G.A.; CARVALHO JUNIOR, R.N.; SAXENA, R.N.; CARBONARI, A.W.The use of nanoparticles coated with different materials have been the subject of study by many researchers to improve the quality of nanomaterials for biomedical applications such as controlled drug delivery, image contrast and treatment of cancer by magnetic hyperthermia [1]. In this work we used ucuúba (virola surinamensis), bacaba (Oenocarpus bacaba Mart.) and açaí (Euterpe oleracea Mart.) oils to coat Fe3O4 nanoparticles. The ucuúba, bacaba and açaí are native tree of the Amazon forest, whose oils are rich in fatty acids present in different proportions, such as, lauric, myristic, steatic, oleic, palmitic, and linoleic acid. These pure oils, free of solvents, were obtained by the extraction method with carbon dioxide in the supercritical state [2], and added during the synthesis process of iron oxide nanoparticles by thermal decomposition method [3]. The samples were characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Perturbed Angular Correlation (PAC) spectroscopy. The XRD results confirmed the formation of Fe3O4 phase. The TEM results determined the average size to be (> 5 nm) and possible spherical morphology of the magnetite nanoparticles. In order to perform the PAC measurements, 111In-111Cd probe nuclei were diffused in the powder samples at 973 K for 2.5 h. PAC measurements permitted the determination of electric quadrupole and magnetic dipole -hyperfine parameters as a function of temperature. The Curie temperature in each case was determined to be ~ 855 K.Resumo IPEN-doc 27089 Effects of surfactant on the morphology of α-Bi2O3 synthesized by the Sol-gel method2019 - PAES, S.C.; CORREA, B.S.; COSTA, M.S.; SENA, C.; CABRERA-PASCA, G.A.; SAXENA, R.N.; CARBONARI, A.W.Nano and micromaterial research, with a well-defined size and shape, has attracted attention from researchers in the areas of chemistry, physics, engineering and biomedicine, due to the wide range of possible applications such as: health, environment, catalysis and miniaturization of electronic devices. In this sense, the chemical routes of synthesis, such as Sol-Gel, are more prominent because it allows the production of particulate materials and thin films, with controllable size and morphology. In this work, bismuth oxide microparticles were synthesized by the Sol-Gel method using metallic bismuth (99.999% purity) in acid solution. Initially, bismuth was diluted with nitric acid solution and distilled water. After dilution, citric acid (600 mg) and ethylene glycol were added. The volume of ethylene glycol was varied from 1 to 3.75 mL, in order to study the morphological effects of its concentration. The samples were then subjected to the calcination process at 673 K for 12 hours. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and Raman spectroscopy. The XRD diffractograms and the Raman spectrum vibration bands showed that the synthesized samples correspond to the bismuth oxide in the alpha phase (α-Bi2O3) [1-3]. The EDS results show typical elements of bismuth oxide, without contaminants. The SEM images revealed different morphologies, ranging from the formation of flakes to microspherical particles with good size distribution (diameter 0.7 and 2.0 μm). All samples have a crystalline structure and vibration modes corresponding to the α-Bi2O3 phase, but these have totally different morphologies, which proves the dependence of the morphology with the concentration of ethylene glycol. In order to perform the PAC measurements, 111In-111Cd probe nuclei were diffused in the samples during synthesis. PAC measurements permitted the determination of electric quadrupole - hyperfine parameters as a function of temperature, from 50 to 673 K.