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Synergetic Phenomenon between Structural Distortion and Cobalt Valence State and its Effect on the Oxygen Evolution Reaction in Cobalt Ferrites

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Ceramics International 2025年

作者： Fabiano R. Praxedes Thayse R. Silva Maria C.M. Ferreira Marcos A.L. Nobre Daniel A. Macedo Silvania Lanfredi Department of Chemistry and Biochemistry São Paulo State University (Unesp) School of Technology and Sciences R. Roberto Simonsen – 305 CEP: 19060-900 Presidente Prudente - SP Brazil São Paulo State University (Unesp) Institute of Biosciences Humanities and Exact Sciences São José do Rio Preto SP 15054-000 Brazil Materials Science and Engineering Postgraduate Program Federal University of Paraíba (UFPB) 58051-900 João Pessoa - PB Brazil Department of Physics São Paulo State University (Unesp) School of Technology and Sciences R. Roberto Simonsen – 305 CEP: 19060-900 Presidente Prudente - SP Brazil

Nanopowders of cobalt ferrite with the stoichiometry Co x Fe 3-x O 4 (0.4 ≤ x ≤ 1.2) were synthesized at 80 °C using a co-precipitation method. The resulting crystalline, single-phase powders were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Morphological analysis of the cobalt ferrite nanoparticles revealed the formation of spherical particle agglomerates at the nanoscale. Chemical bond analysis by infrared spectroscopy, based on the deconvolution of absorption bands, together with structural characterization by XRD and Rietveld refinement, confirmed the formation of a spinel-type phase with cubic symmetry and space group Fd-3m. The improved electrocatalytic performance was observed for the sample with the highest Co content (Co 1.2 Fe 1.8 O 4 , requiring 320 mV to achieve 10 mA cm -2 ). The structure-activity relationships indicate the OER mechanism in our cobalt ferrites is governed by three interconnected factors: octahedral Co 3+ dominance, bond-angle flexibility, and increased Co content, synergistically enhancing catalytic efficiency.

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Devulcanization of natural rubber in composites with distinct crosslink densities by twin-screw extruder

Devulcanization of natural rubber in composites with distinc...

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作者： Barbosa, Rafael Nunes, Anderson Thadeu Ambrósio, José Donato Materials Science and Engineering Postgraduate Program - PPGCEM Federal University of São Carlos - UFSCar São Carlos SP Brazil Center of Characterization and Materials Development - CCDM Federal University of São Carlos - UFSCar São Carlos SP Brazil

In this study, the effects of the devulcanization process realized by an intermeshing co-rotating twin-screw extruder (ICTSE) on three vulcanized Natural Rubber (NR) composites with different crosslink densities (CD) have been investigated. The extrusion parameters were fixed, as well as the initial material granulometry and auxiliary thermoplastic added to the process. After composites vulcanization, they were characterized accordingly their soluble fraction (SF), crosslink density (CD), mechanical properties and thermogravimetry (TGA). The extrusion was performed on the vulcanized elastomers pursuing selectively crosslink rupture and the same characterization previously cited was conducted on the devulcanized material, except the mechanical properties analysis. The extrusion demonstrate effective devulcanization, evidenced in the increasing of soluble fractions, reduction in crosslink density and thermal stability gain. These results are directly affected by preliminary differences on materials structure and presence of ethylene vinyl-acetate (EVA) on extrusion. © 2017 Universidade Federal de Sao Carlos. All rights reserved.

关键词： Rubber

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Characterization of ZnAl2O4 spinel obtained by hydrothermal and microwave assisted combustion method: A comparative study

Characterization of ZnAl2O4 spinel obtained by hydrothermal ...

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作者： De Macedo, Heloísa Pimenta De Araújo Medeiros, Rodolfo Luíz Bezerra De Medeiros, Amanda Lucena De Oliveira, Ângelo Anderson Silva De Figueredo, Gilvan Pereira De Freitas Melo, Marcus Antônio De Araújo Melo, Dulce Maria Postgraduate Program in Science and Engineering of Materials Federal University of Rio Grande do Norte - UFRN Natal RNCEP 59078-970 Brazil Postgraduate Program in Science and Engineering of Petroleum Federal University of Rio Grande do Norte - UFRN Natal RNCEP 59078-970 Brazil Postgraduate Program in Chemistry Chemistry Institute Federal University of Rio Grande do Norte - UFRN Natal RNCEP 59078-970 Brazil Chemistry Department Federal Institute of Education Science and Technology of Maranhão - IFMA São LuísMACEP 65076-091 Brazil Department of Chemical Engineering Federal University of Rio Grande do Norte - UFRN Natal RNCEP 59078-970 Brazil

In this work, zinc aluminate spinel was prepared by two methods of directly synthesis (without calcination): microwave assisted combustion and hydrothermal method. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2-adsorption/ desorption isotherms. The XRD patterns confirmed the formation of cubic ZnAl2O4 spinel structure with no secondary phases for both synthesis routes, whereas the hydrothermal method yielded powders with crystallite size 3 times smaller (6.9 nm), as compared to the powders produced by microwave assisted combustion method (25.6 nm). The micrographs revealed agglomerated powders with plate-like morphologies for both routes. Nitrogen adsorption/desorption isotherms (BET) revealed higher surface area (183 m2.g-1) and greater pore volume (0.173 cm3.g-1) for ZnAl2O4 powders prepared by the hydrothermal method. © 2017 Universidade Federal de Sao Carlos. All rights reserved.

关键词： Zinc compounds

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High-Temperature Oxidation Behavior of Fe-18Al Alloy Added with 2 %ZrO2 Nanoparticles

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IOP Conference Series: materials science and engineering 2019年第1期515卷

作者： P Pawawoi D H Prajitno A A Dewi A Manaf Postgraduate Program of Materials Science Study Department of Physics Faculty of Mathematics and Natural Sciences Universitas Indonesia Depok 16514 PTNBR- BATAN Jln. Tamansari 71 Bandung 40317 Bandung Metallurgical Engineering of Jenderal Achmad Yani University Jln. Gatot Subroto PO. Box 807 Bandung 40285

The oxidation behaviour of ZrO2 nanoparticles added to Fe-18Al alloy has been studied. Isothermal oxidation behaviour with various temperatures and times was investigated and the results of microstructure showed the presence of Fe3Al intermetallic phases in grey color, Al2O3 oxide in white color, and the porosity indicated by dark color. The results of XRD and SEM-EDS analysis also confirmed the presence of the ZrO2 nanoparticles in addition to Fe3Al intermetallic phases and Al2O3 oxide phases. The addition of ZrO2 nanoparticles tended to decrease oxidation rate by promoting Al2O3 layers.

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Chemical Composition,Antioxidant and Antimicrobial Activity of the Oil and Plant Extract Myrocarpus frondosus Allemao

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American Journal of Plant sciences 2017年第7期8卷 1560-1571页

作者： Ivandra Ignês de Santi Darci Alberto Gatto Miriam Ribeiro Galvao Machado Patrícia Soares Bilhalva dos Santos Rogerio Ant?nio Freitag Natural Products Research Laboratory Graduate Program in Biochemistry and Bioprospecting Federal University of Pelotas Pelotas Brasil Postgraduate Program Materials Science and Engineering Federal University of Pelotas Pelotas Brasil Center for Chemical Sciences Pharmaceutical and Food Federal University of Pelotas Pelotas Brasil Chemical and Environmental Engineering Department University of the Basque Country (UPV/EHU) San Sebastian Spain

The objective of this study was to evaluate the chemical profile of extracts (aqueous and ethanol) and the essential oil of Myrocarpus frondosus Allem?o, the sensitivity of strains of Escherichia coli, Staphylococcus aureus, Salmonella typhimurium and Listéria monocytogenes, front the extracts and essential oil, by means of the microdilution method in broth, the antioxidant activity by the ABTS method, and the content of phenolic compounds present in the extracts and oil. For the preparation of extracts from plant leaves used with ethanol and water, then separated, the chemical identification of compounds was performed by high-performance liquid chromatography (CLAE-DAD) and gas chromatography coupled to mass spectrum (CG/MS). With the chemical analysis of the extracts obtained the presence of the major compound rutin, and oil major compound was found germacrene B. In the microdilution method in broth, oil and extracts showed inhibition against all the bacteria tested in the concentrations 1 mg/ml to 0.25 mg/ml, except for Staphylococcus aureus at a concentration of 0.25 mg/ml of the essential oil and trans-caryophyllene. The results of Minimum Bactericidal Concentration showed that the essential oil had bactericidal activity at a concentration of 1mg/ml for all bacteria tested and trans-caryophyllene at the same concentration only for Listeria monocytogenes. In relation to the essential oil, antioxidant activity showed higher radical reduction capacity of 40.92% and the content of phenolic compounds ethanol extract showed more 12.72%. The in vitro results support the conclusion that the essential oil is very promising both in antimicrobial action as antioxidant activity and the leaf extracts on antioxidant activity.

关键词： Myrocarpus frondosus Allemao Antimicrobial Antioxidant

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Phase and crystallite size analysis of (Ti1-xMox)C-(Ni,Cr) cermet obtained by mechanical alloying

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AIP Conference Proceedings 2018年第1期1945卷

作者： Suryana Muhammad Anis Azwar Manaf 1Materials Science Postgraduate Program Physics Department Universitas Indonesia Jl. Salemba Raya No.4 Jakarta 10430 Indonesia 2Department of Metallurgy and Materials Engineering Universitas Indonesia Depok 16424 Indonesia

In this paper, we report the phase and crystallite size analysis of (Ti1-xMox)C-(Ni,Cr) with x = 0-0.5 cermet obtained by mechanical alloying of Ti, Mo, Ni, Cr and C elemental powders using a high-energy shaker ball mill under wet condition for 10 hours. The process used toluene as process control agent and the ball to mass ratio was 10:1. The mechanically milled powder was then consolidated and subsequently heated at a temperature 850°C for 2 hours under an argon flow to prevent oxidation. The product was characterized by X-ray diffraction (XRD) and scanning electron microscope equipped with energy dispersive analyzer. Results shown that, by the selection of appropriate condition during the mechanical alloying process, a metastable Ti-Ni-Cr-C powders could be obtained. The powder then allowed the in situ synthesis of TiC-(Ni,Cr) cermet which took place during exposure time at a high temperature that applied in reactive sintering step. Addition to molybdenum has caused shifting the TiC XRD peaks to a slightly higher angle which indicated that molybdenum dissolved in TiC phase. The crystallite size distribution of TiC is discussed in the report, which showing that the mean size decreased with the addition of molybdenum.

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Synthesis of green-emitting carbon quantum dots with excitation wavelength dependent photoluminescence obtained from aqueous beetroot extract

Synthesis of green-emitting carbon quantum dots with excitat...

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作者： Andrade, George R. S. Costa, Silvânio S. L. Nascimento, Cristiane C. Gimenez, Iara F. Postgraduate Program in Materials Science and Engineering Federal University of Sergipe Saõ Cristóvaõ Brazil Postgraduate Program in Chemistry Federal University of Bahia Salvador Brazil NUPEG Federal University of Sergipe Saõ Cristóvaõ Brazil Federal Institute of Education Science and Technology of Sergipe Aracaju Brazil Department of Chemistry Federal University of Sergipe Saõ Cristóvaõ Brazil

In this work, 3 simple, fast, labour and energy efficient methodologies were used to prepare carbon quantum dots (C-dots) using a red beetroot (Beta vulgaris subsp. vulgaris var. vulgaris) aqueous extract as the carbon source: Alkali-assisted (AA), microwave-assisted (MA) and alkali-microwave-assisted (AMA) synthesis. TEM images shows nanoparticles with a nearly spherical morphology and diameters around 7.0 nm. FTIR spectra show characteristic peaks of C-H, C-O, O-H and C=C bonds for all the samples. The emission spectra show an interesting feature of the as-prepared samples: The emission band position can be tunable by changing the excitation wavelength. Comparing the 3 different methodologies in terms of photoluminescence properties, the one based only on the microwave-assisted heating has showed the most improved emission. © 2016 materials Research Society.

关键词： Semiconductor quantum dots

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S3M: A suggestion mechanism for semantic web service composition 15

S3M: A suggestion mechanism for semantic web service composi...

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21st Brazilian Symposium on Multimedia and the Web, WebMedia 2015

作者： Busanello Da Silva, Diogo P. Weber, Mathias Henrique Siqueira, Frank Department of Informatics and Statistics Federal University of Santa Catarina Florianópolis Brazil Postgraduate Program on Materials Science and Engineering Federal University of Santa Catarina Florianópolis Brazil

ISBN: (纸本)9781450339599

Web Service composition is a complex and error-prone process that requires the support of software tools in order to become feasible. Composition tools can help a developer to select compatible services from vast service repositories, taking into account characteristics such as port compatibility, availability, cost, and so on. This paper describes S3M, a service suggestion mechanism that, coupled with the CVFlow workflow editor, helps developers to select services and to build compositions. Service suggestions are given to the user taking into account the semantic description of Web Services in SAWSDL format. © 2015 ACM.

关键词： Websites

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Microwave-assisted hydrothermal synthesis of NiO-Ce1-xEuxO2-δ powders for fuel cell catalytic anodes

Microwave-assisted hydrothermal synthesis of NiO-Ce1-xEuxO2-...

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Symposium on Nanotechnology General Session - 225th ECS Meeting

作者： Medeiros, A.L. Martinelli, A.E. Melo, D.M.A. Orlandi, M.O. Macedo, D.A. Materials Science and Engineering Postgraduate Program UFRN Natal59072-970 Brazil Institute of Chemistry UNESP Araraquara14801-907 Brazil Department of Materials Engineering UFPB João Pessoa58051-900 Brazil

ISBN: (纸本)9781607685869

CeO2-based materials doped with rare earth (TR+3) can be used as alternative to traditional NiO-YSZ anodes in solid oxide fuel cells as they have higher ionic conductivity and lower ohmic losses compared to YSZ. Moreover, they allow fuel cell operation at lower temperatures (500-800°C). In the anode composition, the concentration of NiO acting as catalyst in YSZ provides high electrical conductivity and high electrochemical activity of reactions, promoting internal reform in the cell. In this work, NiO - Ce1-xEuxO2-δ compounds (x = 0.1, 0.2 and 0.3) have been synthesized by microwave-assisted hydrothermal method. The materials were characterized by TG, XRD, TPR and SEM-FEG techniques. The refinement of data obtained by X-ray diffraction showed the presence of ceria doped with europium crystallized in a cubic phase with fluorite structure, in addition to the presence of NiO. The microwaveassisted hydrothermal method showed significant reduction in the average particle size and good mass control of phase compositions compared to other chemical synthesis techniques. © The Electrochemical Society.

关键词： Nickel oxide

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Electrical properties of lanthanum silicate apatite electrolytes prepared by an innovative chemical route

Electrical properties of lanthanum silicate apatite electrol...

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Symposium on Nanotechnology General Session - 225th ECS Meeting

作者： Macedo, G.L.S. Macedo, D.A. Rajesh, S. Martinelli, A.E. Figueiredo, F.M.L. Marques, F.M.B. Nascimento, R.M. Department of Chemical Engineering UFRN Natal59078-970 Brazil Department of Materials Engineering UFPB João Pessoa58051-900 Brazil Dept. of Materials and Ceramic Eng. CICECO University of Aveiro 3810-193 Portugal Materials Science and Engineering Postgraduate Program UFRN 59078-970 Brazil

ISBN: (纸本)9781607685869

This work reports the synthesis of apatite-type lanthanum silicate powders with nominal composition La10Si6O27 by an innovative chemical route which combines co-precipitation and sol-gel approaches. The herein proposed synthetic procedure is advantageous in reducing energy consumption and processing time, key elements to decrease the total manufacturing cost. The asprepared powder was calcined between 500 and 900 °C. Structure of the calcined powders, characterized by X-ray diffraction (XRD) and Rietveld refinement, indicated the formation of apatite crystalline lanthanum silicate with minor amount of L2O3 at 900 °C. The apatite powder was further analyzed by scanning electron microscopy (SEM). The effect of sintering temperature, ranging from 1400 to 1450 °C, on the electrical properties was investigated by impedance spectroscopy. Electrical measurements were recorded in the 400-800 °C temperature range. The lanthanum silicate electrolyte sintered at 1450 °C exhibited total electrical conductivity (σ700 °C = 2.12 × 10-3 ***-1) comparable with samples from literature prepared by sol-gel and freeze drying methods and sintered at 1500 °C. The results in the present study demonstrate that the co-precipitation method combined with a solgel approach is a promising alternative route to synthesize lanthanum silicate powders. © The Electrochemical Society.

关键词： Powders

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