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Papers by Laédna Souto Neiva

Materials Research

In this study, the effects of dopant concentrations on the structural and morphological character... more In this study, the effects of dopant concentrations on the structural and morphological characteristics of Zn 1-x Mn x O powders (x= 0.025, 0.05, 0.075, and 0.1 mole) synthesized by the Pechini method has been investigated. The powder was characterized by X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET) specific surface, energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and Spectroscopy with Fourier transform (FTIR). An XRD analysis of the powder showed the formation of ZnO phase with a typical single phase wurtzite structure. The EDX analysis revealed Mn incorporated in the ZnO structure. The particle size calculated by BET ranged from 24 to 63 nm, confirming the nanometric size of the powder particles. The SEM analysis revealed irregular shaped particle agglomerates and the presence of nanosheets. From FTIR it was confirmed the wurtzite structure in ZnO and ZnO nanoparticles doped with Mn.

DEMOCRATIZAÇÃO DO CONHECIMENTO E VALORIZAÇÃO PROFISSIONAL: CAMINHOS PARA O DESENVOLVIMENTO TECNOLÓGICO E SOCIAL

Brazilian Journal of Development

Materials Engineering presents an important process in the development of new technologies, in th... more Materials Engineering presents an important process in the development of new technologies, in the creation and improvement of materials, aimed at improving aspects of society, such as: health, safety, quality and well-being of human life. Being ethics is an intrinsic factor to life in which it is possible to affirm that the exercise exerts the capacity to think in actions and conducts that can be used as exercises of any type of activity. technical and human resources. Aligned in this context, the present work aims to trigger on the ethics in the training and the performance of materials engineers based on a bibliographical review. During the review process, the ethics-related study topics were highlighted, which are of great relevance for postgraduate studies in life sciences; since the experience is a part of the professional is increasingly progressing its presentation devices that are beyond technical training. Based on the article of literature over time, this is a work that can be applied to a professional in the area of communication, such as the applications of technical norms required in the exercise of the profession in a way associated with moral, legal, environmental and humanitarian concepts. Finally, it was possible to verify that it was indispensable for the professional tasks of the engineering of materials or for the formation of other activities similar to the plan and the use of concepts and concepts specific to the social sciences, as is the case of ethical issues, with focus in explaining the code of professional ethics in order to meet a challenge as the demands demanded by the increasingly pluralized and multicultural world does not qualify at the present time.

Materials Science Forum, 2010

This work has for aim to synthesize CeO2 catalytic supports doped with Cu2+ by combustion reactio... more This work has for aim to synthesize CeO2 catalytic supports doped with Cu2+ by combustion reaction method. Thus were obtained catalytic supports with the composition Ce1-xCuxO2 and the effect caused by doped element in the structure of the CeO2 was evaluated. The concentration value (x) of the Cu doped took over the values of 0.0; 0.3 and 0.5 mol. The catalytic supports developed were submitted to the structural characterization by X-ray diffraction, morphologic analysis by SEM and textural analysis by means of adsorption-dessorption of N2 by BET method. The results showed that the doped element (Cu) was not completely incorporated in the CeO2 structure and was evidenced that how much larger the quantity of Cu larger maid the disorder of the atomic structure of the obtained material. The analyzed supports present mesoporous nature structure.

Advanced Powder Technology Viii, Pts 1 and 2, 2012

Because of the unique properties that the system TiO2-ZrO2 has, this system has attracted great i... more Because of the unique properties that the system TiO2-ZrO2 has, this system has attracted great interest in catalytic circles. In general, the TiO2-ZrO2 oxides composites have a greater surface area and a stronger acidity when compared to the single oxide and they are used as catalysts supports for many catalytic reactions. This work is to evaluate the effect of calcined temperature in structural and morphological characteristics of Ti1-xZrxO2nanopowders obtained by Pechini method. For this study, the doping value was 0.25 moles of Zr. The powders were calcined at temperature of 500 to 900°C for one hour. The powders were characterized by XRD, SEM and BET. The X-ray diffraction showed that the powders present a TiO2anatase phase and another of ZrO2tetragonal. The crystallite size ranged from 4.8 to 14.6 nm for the temperature of 500 to 900°C, respectively. The analysis of scanning electron microscopy showed soft homogeneous agglomerates with particles around 100 nm. The main particles sizes by BET were ranged from 10 to 20 nm, showing that the synthesis is effective to obtain nanometric powders.

Materials Science Forum, 2012

This work shows the influence of the fuels aniline, carbohydrazide and glycine on structural and ... more This work shows the influence of the fuels aniline, carbohydrazide and glycine on structural and morphological characteristics of ZnAl2O4 synthesized by combustion reaction. Samples were prepared according to the propellants and explosives theory using a vitreous silica crucible and a muffle furnace as heating source. During the synthesis was measured the time and temperature of the reaction. After The samples were structurally and morphologically characterized by the following techniques: XRD, nitrogen adsorption / desorption (BET / BJH), and SEM. The higher temperature was achieved by the synthesis using aniline, whose value was of 876°C. XRD results showed that all the samples presented the ZnAl2O4 spinel as majority phase and, ZnO and Al2O3 as segregated phases. The samples also showed low surface area, varying of 23.6 to 28.7 m2/g, and particle size of 45 to 55 nm, besides mesoporous characteristic and irregular agglomerates formation.

Materials Science Forum, 2014

The synthesis by combustion reaction stands as an alternative technique for preparing powders wit... more The synthesis by combustion reaction stands as an alternative technique for preparing powders with high purity level, nanometric particle size and low cost. Therefore, this study had as objective the synthesis and characterization of ferrite powders with nominal composition NI1-xZnxFe2O4 (x = 0.6, 0.7 and 0.8 mol) prepared by combustion reaction using urea as fuel. The influence of the quantity of zinc in the final characteristics of the powders was also investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET) and scanning electron microscopy (SEM). All compositions resulted in nanometric powders of Ni-Zn ferrites with direct formation of the inverse spinel phase, showing the effectiveness of the synthesis method applied. The increase of zinc's concentration caused an increase in surface area, ranging 4 m2g-1 from 23 m2 g-1. And the SEM micrographs show that the powders have thinner particle morphology with increasing zinc content.

Materials Science Forum, 2010

Materials Science Forum, 2012

The aim this work is to synthesize the CeO2in the ceramic powder form through three different met... more The aim this work is to synthesize the CeO2in the ceramic powder form through three different methods of synthesis, they are: method of combustion, Pechini method and hydrothermal method. Will be evaluated the influence exerted by these methods of preparing of the metallic oxide on the structural features presented in the same. Three samples of CeO2were synthesized in this work, they were analysed by x-ray diffraction, SEM and adsorption and desorption of N2by BET method. According to the results has been observed that the synthesis method has great influence on the structural characteristics of CeO2obtained. The sample of CeO2synthesized by Pechini method showed a structure with a higher percentage of crystallinity and average pore diameter smaller when compared to samples of CeO2synthesized by means of the combustion method and of the hydrothermal method. The sample synthesized by the combustion reaction method presented larger agglomerated of unitary particles.

Journal of Physics D: Applied Physics, 2010

Polycrystalline and epitaxial Ni x Fe 3−x O 4 (0 x 1.03) thin films were fabricated by reactively... more Polycrystalline and epitaxial Ni x Fe 3−x O 4 (0 x 1.03) thin films were fabricated by reactively co-sputtering Fe and Ni targets in a mixed Ar + O 2 atmosphere, and the structure, magnetic and magnetotransport properties were investigated systematically. The saturation magnetization and resistivity can be tuned over a wide range. The room-temperature saturation magnetization for the polycrystalline thin films decreases linearly with x from 440 to 230 emu cm −3 , due to Ni substitution. For the epitaxial thin films, the saturation magnetization and the resistivity can be tuned in the range 195-340 emu cm −3 and 10 −4-10 −2 m by Ni substitution and the introduction of Fe vacancies, because both Ni substitution and Fe vacancies can influence the charge carrier density and the double exchange on the B sublattice.

Materials Research

In this study, the effects of dopant concentrations on the structural and morphological character... more In this study, the effects of dopant concentrations on the structural and morphological characteristics of Zn 1-x Mn x O powders (x= 0.025, 0.05, 0.075, and 0.1 mole) synthesized by the Pechini method has been investigated. The powder was characterized by X-ray diffraction (XRD), Brunauer-Emmet-Teller (BET) specific surface, energy dispersive X-ray (EDX), scanning electron microscopy (SEM) and Spectroscopy with Fourier transform (FTIR). An XRD analysis of the powder showed the formation of ZnO phase with a typical single phase wurtzite structure. The EDX analysis revealed Mn incorporated in the ZnO structure. The particle size calculated by BET ranged from 24 to 63 nm, confirming the nanometric size of the powder particles. The SEM analysis revealed irregular shaped particle agglomerates and the presence of nanosheets. From FTIR it was confirmed the wurtzite structure in ZnO and ZnO nanoparticles doped with Mn.

DEMOCRATIZAÇÃO DO CONHECIMENTO E VALORIZAÇÃO PROFISSIONAL: CAMINHOS PARA O DESENVOLVIMENTO TECNOLÓGICO E SOCIAL

Brazilian Journal of Development

Materials Engineering presents an important process in the development of new technologies, in th... more Materials Engineering presents an important process in the development of new technologies, in the creation and improvement of materials, aimed at improving aspects of society, such as: health, safety, quality and well-being of human life. Being ethics is an intrinsic factor to life in which it is possible to affirm that the exercise exerts the capacity to think in actions and conducts that can be used as exercises of any type of activity. technical and human resources. Aligned in this context, the present work aims to trigger on the ethics in the training and the performance of materials engineers based on a bibliographical review. During the review process, the ethics-related study topics were highlighted, which are of great relevance for postgraduate studies in life sciences; since the experience is a part of the professional is increasingly progressing its presentation devices that are beyond technical training. Based on the article of literature over time, this is a work that can be applied to a professional in the area of communication, such as the applications of technical norms required in the exercise of the profession in a way associated with moral, legal, environmental and humanitarian concepts. Finally, it was possible to verify that it was indispensable for the professional tasks of the engineering of materials or for the formation of other activities similar to the plan and the use of concepts and concepts specific to the social sciences, as is the case of ethical issues, with focus in explaining the code of professional ethics in order to meet a challenge as the demands demanded by the increasingly pluralized and multicultural world does not qualify at the present time.

Materials Science Forum, 2010

This work has for aim to synthesize CeO2 catalytic supports doped with Cu2+ by combustion reactio... more This work has for aim to synthesize CeO2 catalytic supports doped with Cu2+ by combustion reaction method. Thus were obtained catalytic supports with the composition Ce1-xCuxO2 and the effect caused by doped element in the structure of the CeO2 was evaluated. The concentration value (x) of the Cu doped took over the values of 0.0; 0.3 and 0.5 mol. The catalytic supports developed were submitted to the structural characterization by X-ray diffraction, morphologic analysis by SEM and textural analysis by means of adsorption-dessorption of N2 by BET method. The results showed that the doped element (Cu) was not completely incorporated in the CeO2 structure and was evidenced that how much larger the quantity of Cu larger maid the disorder of the atomic structure of the obtained material. The analyzed supports present mesoporous nature structure.

Advanced Powder Technology Viii, Pts 1 and 2, 2012

Because of the unique properties that the system TiO2-ZrO2 has, this system has attracted great i... more Because of the unique properties that the system TiO2-ZrO2 has, this system has attracted great interest in catalytic circles. In general, the TiO2-ZrO2 oxides composites have a greater surface area and a stronger acidity when compared to the single oxide and they are used as catalysts supports for many catalytic reactions. This work is to evaluate the effect of calcined temperature in structural and morphological characteristics of Ti1-xZrxO2nanopowders obtained by Pechini method. For this study, the doping value was 0.25 moles of Zr. The powders were calcined at temperature of 500 to 900°C for one hour. The powders were characterized by XRD, SEM and BET. The X-ray diffraction showed that the powders present a TiO2anatase phase and another of ZrO2tetragonal. The crystallite size ranged from 4.8 to 14.6 nm for the temperature of 500 to 900°C, respectively. The analysis of scanning electron microscopy showed soft homogeneous agglomerates with particles around 100 nm. The main particles sizes by BET were ranged from 10 to 20 nm, showing that the synthesis is effective to obtain nanometric powders.

Materials Science Forum, 2012

This work shows the influence of the fuels aniline, carbohydrazide and glycine on structural and ... more This work shows the influence of the fuels aniline, carbohydrazide and glycine on structural and morphological characteristics of ZnAl2O4 synthesized by combustion reaction. Samples were prepared according to the propellants and explosives theory using a vitreous silica crucible and a muffle furnace as heating source. During the synthesis was measured the time and temperature of the reaction. After The samples were structurally and morphologically characterized by the following techniques: XRD, nitrogen adsorption / desorption (BET / BJH), and SEM. The higher temperature was achieved by the synthesis using aniline, whose value was of 876°C. XRD results showed that all the samples presented the ZnAl2O4 spinel as majority phase and, ZnO and Al2O3 as segregated phases. The samples also showed low surface area, varying of 23.6 to 28.7 m2/g, and particle size of 45 to 55 nm, besides mesoporous characteristic and irregular agglomerates formation.

Materials Science Forum, 2014

The synthesis by combustion reaction stands as an alternative technique for preparing powders wit... more The synthesis by combustion reaction stands as an alternative technique for preparing powders with high purity level, nanometric particle size and low cost. Therefore, this study had as objective the synthesis and characterization of ferrite powders with nominal composition NI1-xZnxFe2O4 (x = 0.6, 0.7 and 0.8 mol) prepared by combustion reaction using urea as fuel. The influence of the quantity of zinc in the final characteristics of the powders was also investigated. The powders were characterized by X-ray diffraction (XRD), nitrogen adsorption (BET) and scanning electron microscopy (SEM). All compositions resulted in nanometric powders of Ni-Zn ferrites with direct formation of the inverse spinel phase, showing the effectiveness of the synthesis method applied. The increase of zinc's concentration caused an increase in surface area, ranging 4 m2g-1 from 23 m2 g-1. And the SEM micrographs show that the powders have thinner particle morphology with increasing zinc content.

Materials Science Forum, 2010

Materials Science Forum, 2012

The aim this work is to synthesize the CeO2in the ceramic powder form through three different met... more The aim this work is to synthesize the CeO2in the ceramic powder form through three different methods of synthesis, they are: method of combustion, Pechini method and hydrothermal method. Will be evaluated the influence exerted by these methods of preparing of the metallic oxide on the structural features presented in the same. Three samples of CeO2were synthesized in this work, they were analysed by x-ray diffraction, SEM and adsorption and desorption of N2by BET method. According to the results has been observed that the synthesis method has great influence on the structural characteristics of CeO2obtained. The sample of CeO2synthesized by Pechini method showed a structure with a higher percentage of crystallinity and average pore diameter smaller when compared to samples of CeO2synthesized by means of the combustion method and of the hydrothermal method. The sample synthesized by the combustion reaction method presented larger agglomerated of unitary particles.

Journal of Physics D: Applied Physics, 2010

Polycrystalline and epitaxial Ni x Fe 3−x O 4 (0 x 1.03) thin films were fabricated by reactively... more Polycrystalline and epitaxial Ni x Fe 3−x O 4 (0 x 1.03) thin films were fabricated by reactively co-sputtering Fe and Ni targets in a mixed Ar + O 2 atmosphere, and the structure, magnetic and magnetotransport properties were investigated systematically. The saturation magnetization and resistivity can be tuned over a wide range. The room-temperature saturation magnetization for the polycrystalline thin films decreases linearly with x from 440 to 230 emu cm −3 , due to Ni substitution. For the epitaxial thin films, the saturation magnetization and the resistivity can be tuned in the range 195-340 emu cm −3 and 10 −4-10 −2 m by Ni substitution and the introduction of Fe vacancies, because both Ni substitution and Fe vacancies can influence the charge carrier density and the double exchange on the B sublattice.