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Materials Science Forum Vol. 805 (2015) pp 591-597 by Josiane Carneiro Souza

Papers by Josiane Carneiro Souza

Materials Research

In this work, iron chloride (FeCl 3 .6H 2 O), a single reagent, was used to create the phases of ... more In this work, iron chloride (FeCl 3 .6H 2 O), a single reagent, was used to create the phases of hematite (α-Fe 2 O 3) and akaganeite (β-FeOOH) without the need of organic solvents using the microwave-assisted hydrothermal technique (HM). X-ray diffraction demonstrated the efficacy of the HM technique in the generation of crystalline phases of α-Fe 2 O 3 at 180 o C and β-FeOOH at 120 o C. The development of pseudo-cunic and stick-like particles was a result of changes in experimental variables, which also had a substantial impact on the materials structural characteristics. The nitrogen (N 2) adsorption/desorption isotherms of the samples containing akaganeite and hematite phase resembled those of mesoporous materials. Hematite has a surface area of 25.44 m 2 g-1 , while akaganeite has a surface area of 110.60 m 2 g-1 , according to the calculation. Thermodifferential and thermogravimetric techniques were used to assess thermal degradation. The use of microwave hydrothermal synthesis was promoted as being quick, easy, affordable, and safe for the environment.

Ciência e Engenharia de Materiais: conceitos, fundamentos e aplicação, 2021

Inorganic Chemistry, 2021

In this paper, we relate the synthesis of silver selenite (Ag2SeO3) by different methods [sonoche... more In this paper, we relate the synthesis of silver selenite (Ag2SeO3) by different methods [sonochemistry, ultrasonic probe, coprecipitation, and microwave-assisted hydrothermal]. These microcrystals presented structural long-range order as confirmed by X-ray diffraction (XRD) and Rietveld refinements, and structural short-range order as confirmed by Fourier transform infrared (FT-IR), and Raman spectroscopies. X-ray photoelectron spectroscopy (XPS) provided information about the surface of the samples indicating that they were pure. The microcrystals presented different shape and size due to synthesis method as observed by field emission scanning electron microscopy (FE-SEM). The optical properties of these microcrystals were evaluated by ultraviolet−visible (UV−vis) spectroscopy and photoluminescence (PL) measurements. Thermal analysis confirmed the temperature stability of the as-synthetized samples. Further trapping experiments prove that the holes and hydroxyl radical, in minor extent, are responsible for the photocatalytic reactions. To complement and rationalize the experimental results, first-principles calculations have been performed within the framework of density functional theory. The experimental results are sustained by DFT calculations that decipher the geometric, energetic, and structural parameters as well as vibrational frequencies; further, the electronic properties (band structure diagram and density of states) of the bulk and corresponding surfaces of Ag2SeO3 were also investigated. On the basis of the calculated values of the surface energies, a map of the available morphologies was obtained by using Wulff construction and compared to the experimental FE-SEM images. By determining the energy profiles associated with the transformation process between different morphologies obtained along the synthesis method, we are capable to find a correlation between morphology and photocatalytic activity, along with photodegradation of Rhodamine B dye under UV light, based on the different numbers of unsaturated superficial Ag and Se cations (local coordination, i.e., clusters) of each surface.

Ionics, 2020

Herein, to balance the overall performance of SPEEK membrane, the imidazolium hydrogen sulfate (I... more Herein, to balance the overall performance of SPEEK membrane, the imidazolium hydrogen sulfate (Im.HSO 4), 1methylimidazolium hydrogen sulfate (MI.HSO 4), and 1-butyl-3-methylimidazolium hydrogen sulfate (BMI.HSO 4) ionic liquids (ILs) were used as dopants in polymer matrix. A series of SPEEK/ionic liquid composite membranes were successfully fabricated by casting method and evaluated. Comparative studies showed that the membranes doped with 5 wt.% of MI.HSO 4 or BMI.HSO 4 ILs showed an increase in the proton conductivity of 50% and 30% at 80°C, respectively, compared with the pristine SPEEK membrane. The proton exchange membrane fuel cell (PEMFC) performance demonstrated that the membrane doped with 5 wt.% of BMI.HSO 4 IL (SBMI5) has the highest current density value and the highest power density without loss of performance as temperature increases. This result indicates that this membrane is promising for fuel cells application.

International Journal of Energy Research, 2018

Nafion membranes were prepared by incorporating in the polymer matrix the 1-butyl-3-methylimidazo... more Nafion membranes were prepared by incorporating in the polymer matrix the 1-butyl-3-methylimidazolium (BMI +) ionic liquid cation at different doping levels. Increasing the doping time of the membranes with the ionic liquid results in increased incorporation of the BMI + cation but a decrease in the bulk conductivity. The thermogravimetric analysis shows that the BMI + cation incorporation increases the thermal stability of the membranes. The higher discharge efficiency of the fuel cell at 80°C was obtained by using Nafion membrane after 15 minutes of doping in the ionic liquid solution.

Ionics, 2018

Two ionic liquids (ILs) with different alkyl chains, 1-butyl-3-methylimidazolium chloride (BMI.Cl... more Two ionic liquids (ILs) with different alkyl chains, 1-butyl-3-methylimidazolium chloride (BMI.Cl) and 1-hexadecyl-3methylimidazolium chloride (C16MI.Cl), were incorporated into ZnO particles using the microwave-assisted hydrothermal (MAH) method. The morphology and microstructure of ZnO and ZnO/IL composites were characterized along with their photocatalytic effect for dye degradation. While the incorporation of ILs into the ZnO particles did not alter their morphology, it converted the shallow defects into deep defects. These changes improved Rhodamine B (RhB) photodegradation efficiency. The dye degradation reached 62% when ZnO/C1640 was used, whereas it reached 30% when pure ZnO was used, during the same time interval.

Materials Science Forum, 2014

Green sand molds are used in metal casting process. However, after heating, activated bentonite p... more Green sand molds are used in metal casting process. However, after heating, activated bentonite present in green sand loses the binding properties, and part of the foundry sand has to be discarded from the process. The ABNT NBR 15.984/2011 standard establishes the management of waste foundry sand (WFS) avoiding disposal in landfills. The objective of this work was to investigate the possibility of reusing the WFS from the study of its interaction with sodium silicate binder. Studies with silica sand and new green sand were performed in order to compare the results obtained with the WFS. The characterization of the samples was performed by measuring compressive strength, by X-ray diffraction, by optical microscopy and by scanning electron microscopy. The results showed that there is an interaction of the sodium silicate with the WFS as well as with the silica sand and green sand.

Ecl�tica Qu�mica Journal

The disposal of substances pollutant, such as methylene blue dye (MB), into wastewater, arouses t... more The disposal of substances pollutant, such as methylene blue dye (MB), into wastewater, arouses the interest of technologies to remove these pollutants. The discoloration of MB by photocatalysis and using femtosecond laser-irradiated Fe2O3 materials as photocatalysts proved to be a promising way to treat this pollutant. Here, Fe2O3 obtained by the conventional hydrothermal process and heat-treatment, subsequently femtosecond laser-irradiated treatment. Materials obtained with a mixture of irradiated ?-Fe2O3 and ?-Fe2O3 phases revealed lower crystallinity than irradiated ?-Fe2O3 samples. The irradiation treatment and the increase in crystallinity were crucial to improve the performance of ?-Fe2O3 irradiated sample in the discoloration of MB, which reached 90% in 75�min of dye solution exposure under UV irradiation. The irradiation treatment proved to allow greater exposure of the particle surfaces, which coalesced and presented a greater distribution of medium size, indicating a more...

This paper demonstrates that femtosecond laser-irradiated Fe 2 O 3 materials containing a mixture... more This paper demonstrates that femtosecond laser-irradiated Fe 2 O 3 materials containing a mixture of α-Fe 2 O 3 and ε-Fe 2 O 3 phases showed significant improvement in their photoelectrochemical performance and magnetic and optical properties. The absence of Raman-active vibrational modes in the irradiated samples and the changes in charge carrier emission observed in the photocurrent density results indicate an increase in the density of defects and distortions in the crystalline lattice when compared to the nonirradiated ones. The magnetization measurements at room temperature for the nonirradiated samples revealed a weak ferromagnetic behavior, whereas the irradiated samples exhibited a strong one. The optical properties showed a reduction in the band gap energy and a higher conductivity for the irradiated materials, causing a higher current density. Due to the high performance observed, it can be applied in dye-sensitized solar cells and water splitting processes. Quantum mechanical calculations based on density functional theory are in accordance with the experimental results, contributing to the elucidation of the changes caused by femtosecond laser irradiation at the molecular level, evaluating structural, energetic, and vibrational frequency parameters. The surface simulations enable the construction of a diagram that elucidates the changes in nanoparticle morphologies.