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All Journal Journal of Applied Materials and Technology Bulletin of Chemical Reaction Engineering & Catalysis
Oliveira, Adhimar Flávio
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Chemical Engineering, Chemistry & Bioengineering Chemistry Civil Engineering, Building, Construction & Architecture Engineering Mechanical Engineering

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Heterobimetallic Zn2+/Co2+ Monocarboxylates as Precursors for ZnO Microparticles Doped with Cobalt and its Photocatalytic Activity in Methyl Orange Oxidation Correa, Hélder Inocêncio Ferreira; Ramalho Jr, Ralf Ricardo; Oliveira, Adhimar Flávio; Lisboa, Fabio da Silva
Bulletin of Chemical Reaction Engineering & Catalysis 2024: BCREC Volume 19 Issue 4 Year 2024 (December 2024)
Publisher : Masyarakat Katalis Indonesia - Indonesian Catalyst Society (MKICS)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.9767/bcrec.20211

Abstract

In this work, zinc oxide microparticles doped with cobalt were prepared from two novel layered heterobimetallic monocarboxylates as precursors to obtain uniform shape and size oxide particles, aiming for a photocatalytic removal of methyl orange. Both monocarboxylates produced ZnO doped with Co2O3 after calcination at 700 or 900 °C, in 7 or 12 hours. The particles formed by the laurate precursor presented rectangular prisms shaped, while those formed from stearate were sphere-like particles. All particles ranged from 0.1 to 0.9 μm size, with a direct bandgap of 2.2 to 2.6 eV and an indirect bandgap of 0.25 to 1.70 eV. The ZnO/Co prepared presented photocatalytic activity on methyl orange photodegradation. The solid prepared by the laurate precursor showed a photodegradation rate of 0.00185 min-1, while the one obtained from the stearate precursor presented a photodegradation rate of 0.00860 min-1, eight times greater. These results show that the material may be very useful in removing dyes from water samples. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Antimicrobial properties of silver/graphene oxide nanocomposite prepared by redox chemical reaction Leyva Gonzalez, Maria Elena; Ribeiro Rodrigues, Rosana; dos Santos, Igor Luiz; Oliveira, Adhimar Flávio; Tavares Wanderley Neto, Estácio; Nakagomi, Fabio; Marques, Paulo Sergio; Tavares , Eder do couto
Journal of Applied Materials and Technology Vol. 6 No. 1 (2024): September 2024
Publisher : Faculty of Engineering Universitas Riau and Applied Materials and Technology Society

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31258/Jamt.6.1.21-29

Abstract

Silver nanoparticles (AgNPs) exhibit outstanding antimicrobial properties, making them highly valuable in biomedical applications. This study presents the synthesis of a graphene oxide-silver nanoparticle (GO-Ag) nanocomposite via a redox chemical reaction, where the hydroxyl groups reduced silver ions present in graphene oxide (GO). Graphene oxide was obtained through electrochemical exfoliation of graphite, followed by ultrasonic exfoliation in the presence of silver ions to form GO-Ag. The materials were characterized using ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). UV-Vis, FTIR, and Raman spectra confirmed GO synthesis. In contrast, XRD and UV-Vis spectra verified the presence of silver nanoparticles in GO-Ag by detecting the surface plasmon resonance (SPR) band and silver’s characteristic diffraction peaks. SEM analysis showed the successful formation of silver nanoparticles on GO sheets. The disc diffusion method assessed Antimicrobial activity against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). GO-Ag nanocomposite displayed significant antibacterial activity, as evidenced by the formation of inhibition zones, whereas GO alone showed no antimicrobial effect. The enhanced antibacterial properties of GO-Ag are attributed to the synergistic interaction between GO and AgNPs. The increased surface area of silver nanoparticles further enhances their antibacterial effectiveness by facilitating better interaction with bacterial membranes. These findings highlight GO-Ag’s potential for use in antimicrobial coatings, wound dressings, and biomedical devices. This study demonstrates an effective, environmentally friendly approach to synthesizing antimicrobial nanocomposites, paving the way for their application in various medical and industrial fields.
Characterization and impact of graphene oxide on the curing and mechanical properties of epoxy resins Jimenez, Gina Maritzell Colmenares; Oliveira, Adhimar Flávio; Carneiro, Tessa Martins de Carvalho; Wanderley Neto, Estacio Tavares; Gonzalez, Maria Elena Leyva
Journal of Applied Materials and Technology Vol. 7 No. 1 (2025): September 2025
Publisher : Faculty of Engineering Universitas Riau and Applied Materials and Technology Society

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31258/Jamt.7.1.11-21

Abstract

Graphene oxide (GO) has been widely studied as a nanofiller for epoxy resins due to its excellent mechanical, thermal, and interfacial properties. In this study, GO was synthesized via electrochemical exfoliation and characterized using FTIR, XRD, TGA, and SEM. GO was incorporated into an epoxy matrix (Litestone 3200 resin with 2131H hardener) at different weight percentages (0.10%, 0.13%, 0.20%, and 0.50%), and the curing behavior was analyzed through differential scanning calorimetry (DSC). The cure kinetics were evaluated using the Kissinger and Ozawa methods. The results indicated that the activation energy increased at 0.13% GO but decreased at higher concentrations. TGA analysis showed that the addition of GO improved thermal stability, particularly at 0.10% GO. FTIR confirmed the presence of oxygenated functional groups in GO, XRD indicated partial exfoliation and structural disorder, and SEM revealed sheet-like morphology. These results were consistent and complementary, supporting the successful incorporation of GO into the epoxy network. The addition of GO slightly improved the mechanical modulus without significantly altering the glass transition temperature (Tg).
Powder metallurgy synthesis of Pd-doped MoS2: A structural and morphological study Nogueira, Jonas Miguel; Oliveira, Adhimar Flavio; Rubinger, Rero Marques; Correa Carvalho, Celso Henrique
Journal of Applied Materials and Technology Vol. 7 No. 1 (2025): September 2025
Publisher : Faculty of Engineering Universitas Riau and Applied Materials and Technology Society

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.31258/Jamt.7.1.31-40

Abstract

This study reports the synthesis and structural characterization of palladium (Pd)-doped molybdenum disulfide (MoS?) produced via the powder metallurgy route. The primary objective was to investigate how Pd incorporation influences the structural, morphological, and electrical properties of MoS?, thereby demonstrating the advantages of powder metallurgy compared to conventional synthesis techniques. The materials were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy. XRD confirmed the retention of the hexagonal MoS? phase without the formation of secondary Pd-related phases, indicating successful substitutional doping. SEM–EDS analyses revealed a uniform Pd distribution and progressive morphological evolution with increasing Pd content, characterized by enhanced surface roughness and improved particle dispersion. FTIR and Raman spectra showed modifications in bonding environments and vibrational modes, evidencing the structural influence of Pd atoms on the MoS? lattice. Electrical measurements, performed using both I–V and four-point probe methods, demonstrated a conductivity increase from 9.6 × 10?? S·m?¹ for pure MoS? to 1.6 × 10?? S·m?¹ and 1.9 × 10?? S·m?¹ for the 1% and 2% Pd-doped samples, respectively. This enhancement is attributed to the higher charge carrier density and improved interlayer charge transport induced by Pd doping. These findings confirm that powder metallurgy provides an effective and scalable synthesis pathway for achieving homogeneous Pd incorporation in MoS?. The resulting materials exhibit excellent structural integrity and enhanced electrical performance, making them promising candidates for catalytic, sensing, and energy storage applications.
Co-Authors Carneiro, Tessa Martins de Carvalho Correa Carvalho, Celso Henrique Correa, Hélder Inocêncio Ferreira dos Santos, Igor Luiz Gonzalez, Maria Elena Leyva Jimenez, Gina Maritzell Colmenares Leyva Gonzalez, Maria Elena Lisboa, Fabio da Silva Marques, Paulo Sergio Nakagomi, Fabio Nogueira, Jonas Miguel Ramalho Jr, Ralf Ricardo Ribeiro Rodrigues, Rosana Rubinger, Rero Marques Tavares , Eder do couto Tavares Wanderley Neto, Estácio Wanderley Neto, Estacio Tavares