Navegando por Autor "Delmonte, Maurício Roberto Bomio"

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Antimicrobial activity from polymeric composites-based polydimethylsiloxane/TiO2/GO: evaluation of filler synthesis and surface morphology
(Springer, 2016-11-04) Correa, Camila F.; Santana, Luiza R.; Silva, Ricardo M.; Noremberg, Bruno S.; Lund, Rafael G.; Ribeiro, Juliana S.; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio; Nascimento, Rubens Maribondo do; Carreño, Neftalí Lênin Villarreal
Antimicrobial substances may be used to reduce hospital infections and inhibit food contamination, thus ensuring the safety and well being of humans. The objective of this study was to evaluate the antimicrobial activity of the polymeric nanocomposites polydimethylsiloxane (PDMS) embedded with two types of fillers based on titanium dioxide (commercial TiO2 P25 versus TiO2 via facile Micro- wave-assisted hydrothermal-MAH synthesis) and graphene oxide (GO). The nanocomposites were prepared using different compositions, concentrations, and functionalizations (PDMS/TiO2/GO; PDMS/TiO2 and PDMS/GO). The antimicro- bial activity of the samples was evaluated for different treatments on Candida albicans, Staphylococcus aureus, and Enterococcus faecalis, by a modified direct contact test (mDCT). The samples were also evaluated on surface morphology and the roughness as a function of active particles insertion by atomic force microscopy (AFM). Most of the PDMS films whose polymer was embedded with GO and hydrothermal TiO2 showed the highest inhibition growth of bacteria and Candida over 24 h. After 24 h, F, J, and H samples showed the best antibacterial activity, whereas E showed the best antifungal activity. The results indicated that the nanocomposites PDMS/GO/TiO2MAH and PDMS/GO sample enhanced antimi- crobial activity in the treatments tested, therefore they were functional for con- taminant reduction
Avaliação de propriedades ópticas e espessura de filmes finos de TiO2 a partir do espectro de transmitância
(Universidade Federal do Rio Grande do Norte, 2016-05-12) Severiano Sobrinho, Valmar da Silva; Melo, José Daniel Diniz; Costa, Thercio Henrique de Carvalho; ; http://lattes.cnpq.br/3647710047561421; ; http://lattes.cnpq.br/6572298923055649; ; Almeida, Edalmy Oliveira de; ; http://lattes.cnpq.br/1480791721671288; Delmonte, Maurício Roberto Bomio; ; http://lattes.cnpq.br/9558299312183852; Nascimento, Rubens Maribondo do; ; http://lattes.cnpq.br/8671649752936793
Filmes finos de TiO2 podem ser a resposta para grandes questões atuais sobre as melhores maneiras de obter energia, economizar energia e reduzir a poluição. Tais filmes têm sido aplicados com sucesso para produção de células solares; como camada em janelas inteligentes, janelas fotocrômicas e eletrocrômicas; além de possuírem propriedades fotocatalítica interessantes. Este trabalho explora a importância tecnológica e científica desse material realizando investigações a respeito dos filmes de TiO2, sua forma de deposição, técnicas de análise, detalhando formas atuais de análise óptica, buscando, de maneira inovadora, comparar tais técnicas, validar seu uso, e comparar seus resultados na busca de meios econômicos da realização de investigações a respeito de espessura, estrutura e avaliação de propriedades fotocatalíticas do material produzido. Nesse trabalho foram utilizadas, para criação de filmes finos, deposição física pelo método de magnetron sputterin. Para análise óptica e cálculo de espessura e Band Gap dos filmes será apresentado o Método do Envelope que foi originalmente proposto por Manifacier (Manifacier, Gasiot e Fillard, 1976) sendo que mais tarde Swanepoel (1983) conseguiu melhorar ainda mais a precisão desse método para encontrar propriedades ópticas dos filmes finos e sua espessura. Também será apresentado, a aplicação de equações propostas nos trabalhos de Lindgren (Lindgren et al., 2003) e a Lei de Beer-Lambert para cálculo do Coeficiente de Absorção dos filmes, outro dado importante para mais tarde determinar o gap dos mesmos, que será encontrado pelo Método Tauc. Para filmes muito finos, com poucas ou nenhuma franja de interferência se faz necessário o estudo de algum Método Computacional para determinação dos seus parâmetros ópticos e espessura. Para tanto utilizou-se o Método PUMA, um Método Computacional desenvolvido por pesquisadores da UNICAMP/USP. Os filmes depositados foram analisados por DRX, EDS, além de serem submetidos a análise óptica, MEV transversal buscando validar os métodos ópticos em termos das espessuras recuperadas, além de encontrado seus Band Gap e seus valores comparados com o esperado pela literatura confrontando tais resultados com a cristalinidade obtida para os filmes.
Biofilms of cellulose and hydroxyapatite composites: Alternative synthesis process
(SAGE Publications, 2020-09-01) Pieper, Cari M.; Rosa, Wellington L. O. da; Lund, Rafael G.; Silva, Adriana F. da; Piva, Evandro; Salas, Mabel M. S.; Maron, Guilherme K.; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da; Carreño, Neftalí Lênin Villarreal
A new biofilm of cellulose coated with hydroxyapatite particles have been prepared using a simple, fast and low temperature process based on a microwave-assisted hydrothermal synthesis. The cellulose used as matrix of the biocomposite was extracted from banana stems residues. The hydroxyapatite coating was performed using calcium nitrate tetrahydrate, phosphoric acid, and 1,2-ethylenediamine dispersed in a cellulose/water solution, with posterior microwave-assisted hydrothermal synthesis, for 5 min at 140°C. The chemical, structural, thermal, and morphological properties of the composites were investigated by X-ray diffraction, infrared spectroscopy, thermogravimetry and field emission scanning electron microscopy. Results showed that the methodology was effective to produce high quality composites, with good thermal stability. Cell viability tests indicated that the cellulose/ Hap films were not cytotoxic
Cerium molybdate nanocrystals: Microstructural, optical and gas- sensing properties
(Elsevier, 2021-03-15) Oliveira, Fernanda Karine Fonseca; Santiago, Anderson de Azevedo Gomes; Catto, Anderson de Azevedo Gomes; Silva, Luís Fernando da; Tranquilin, Ricardo Luis; Silva, Elson Longo da; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio
Metal molybdate compounds have attracted considerable attention due to their technological applications. Herein, we demonstrate the controllable synthesis of cerium molybdate (Ce2(MoO4)3) nanocrystals via the co-precipitation method followed by microwave-assisted hydrothermal (MAH) treatment at 150 C during different times (15, 30 and 60 min). The effect of MAH treatment time on the microstructural, optical, and ozone gas-sensing properties of these nanocrystals was investigated. X-ray diffraction (XRD) and Raman spectroscopy measurements revealed that the samples presented a single-crystalline phase with scheelite-type tetragonal structure. Field emission gun scanning electron microscopy (FEG-SEM) images showed that the MAH conditions favored changes in the Ce2(MoO4)3 nano crystal morphology. Photoluminescence (PL) measurements indicated a significant enhancement of PL emission with MAH time, suggesting an increase in the intrinsic defects formed during the MAH treatment. The gas-sensing performance of cerium molybdate nanocrystals towards sub-ppm ozone levels was also investigated. The experiments revealed complete recovery and good repeatability as well as good sensor response, which was improved in the sample synthesized at longer MAH time
Characterization and photocatalytic application of Ce4+, Co2+, Mn2+ and Ni2+ doped Fe3O4 magnetic nanoparticles obtained by the co-precipitation method
(Elsevier, 2020-02-15) Andrade Neto, Nivaldo Freire de; Nascimento, Leulomar Enedino do; Corrêa, Marcio Assolin; Bohn, Felipe; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
In this work, Ce4+, Co2+, Mn2+ and Ni2+ doped Fe3O4 nanoparticles were obtained by the co-precipitation method at 70 °C. The effects of the metal cations in the Fe3O4 lattice were investigated by X-ray diffraction (XRD), X-ray fluorescence (XRF), field emission scanning electron microscopy (SEM), nitrogen adsorption by the Brunauer-Emmett-Teller (BET) and UV–Visible (UV–Vis) spectroscopy. Magnetic properties were estimated by vibrating sample magnetometer (VSM) at room temperature and the electrical properties are studied through I–V curves. The photocatalytic properties were studied by the discoloration of the methylene blue (MB) dye. The reduction in the intensity of the diffraction peaks, followed by their enlargement, indicate that doping reduces the crystallite size of Fe3O4. Doping provided the reduction of the remaining magnetization, as the saturation magnetization increases, not being reached with 17 kOe. The electrical results indicate that only cobalt reduces the resistivity of Fe3O4, as manganese is the most increasing doping. Photocatalytic tests indicate that the defects generated by doping increase the photocatalytic activity of Fe3O4, being more expressive through doping with cerium
Characterization and photoluminescent, photocatalytic and antimicrobial properties of Boron-Doped TiO2 Nanoparticles Obtained by Microwave-Assisted Solvothermic Method
(Springer, 2019-02-27) Andrade Neto, Nivaldo Freire de; Zanatta, Paolo; Nascimento, Leulomar Enedino do; Nascimento, Rubens Maribondo do; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
Boron doped TiO2:xB (x = 0 mol.%, 1 mol.%, 2 mol.%, 4 mol.% and 8 mol.%) was quickly synthesized by a microwave-assisted solvothermic method at 140C for 10 min. The nanoparticles obtained were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, photoluminescence, field emission scanning electron microscopy, electron microscopy and diffuse optical reflectance. The photocatalytic properties were estimated against methylene blue dye. The antimicrobial activity was measured by the disc diffusion technique against S. aureus and E. coli bacteria. The XRD patterns show that there was no formation of secondary phases and that all the peaks correspond to the anatase phase of TiO2. Rietveld’s refinement showed that the addition of B3+ in the TiO2 lattice promotes a reduction in the size of the crystallites and this reduction it effectively increases the degradation capacity of the methylene blue dye, which after 50 min the 8%B sample degraded completely, while the pure TiO2 sample reduced its concentration by 95%. Boron-doped TiO2 was effective when reused and after the third cycle the photocatalytic activity of the powders was maintained. In addition, the incorporation of 8%B in the TiO2 lattice resulted in an increase from 8.66 mm to 15.61 mm and 9.04 mm to 13.65 mm in the inhibition halos of the S. aureus and E. coli bacteria, respectively
Computational procedure to an accurate DFT simulation to solid state systems
(Elsevier, 2019-12) Gomes, Eduardo O.; Fabris, Guilherme da Silva Lopes; Ferrer, Mateus M.; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio; Andres, Juan; Silva, Elson Longo da; Sambrano, Júlio Ricardo
The density functional theory has become increasingly common as a methodology to explain the properties of crystalline materials because of the improvement in computational infrastructure and software development to perform such computational simulations. Although several studies have shown that the characteristics of certain classes of materials can be represented with great precision, it is still necessary to improve the methods and strategies in order to achieve more realistic computational modeling. In the present work, strategies are reported in a systematic way for the accurate representation of crystalline systems. The crystalline compound chosen for the study as a case test was BaMoO4, both because of its potential technological application and because of the low accuracy of the simulations previously reported in the literature. The computational models were carried out with the B3LYP and WC1LYP functionals selected from an initial set containing eight hybrid functionals in conjunction with an all-electron basis set. Two different strategies were applied for improving the description of the initial models, both involving atomic basis set optimization and Hartree-Fock exchange percentage adjustment. The results obtained with the two strategies show a precision of structural parameters, band gap energy, and vibrational properties never before presented in theoretical studies of BaMoO4. Finally, a flowchart of good calculation practices is elaborated. This can be of great value for the organization and conduction of calculations in new research
Connecting the surface structure, morphology and photocatalytic activity of Ag2O: An in depth and unified theoretical investigation
(Elsevier, 2020-04-15) Ribeiro, Renan Augusto Pontes; Oliveira, Marisa Carvalho de; Delmonte, Maurício Roberto Bomio; Lazaro, Sérgio Ricardo de; Andrés, Juan; Silva, Elson Longo da
The surface morphology of the materials is known to have significant influence on the overall photocatalytic performance. Therefore, identifying the corresponding electronic structures associated with the surface redox centers is essential for the rational design of Ag2O-based photocatalysts. In this study, comprehensive and sys- tematic theoretical calculations revealed the connection between electronic structure and morphology responsible for the photo-induced mechanism. First-principles calculations showed that the activity of Ag+ cations on the exposed surfaces is dependent of their local coordination and electronic configuration. Electrons were found to migrate to the energetically favorable (1 1 1) surface, while holes are concentrated in the more unstable (1 0 0) and (1 1 0) surfaces. The complete set of available morphologies was obtained, enabling us to rationalize the photocatalytic activity in terms of composition, geometry, and electronic structure of the exposed surfaces. Moreover, the localization and characterization of excited electronic states of both bulk material and exposed surfaces allow us to discuss the fundamental reactions involved in the photocatalytic mechanism underlying the morphological evolution and would promote significantly the development and application of singlet-triplet mechanism. The detailed insights provided by our work could benefit the design and preparation of new efficient photocatalysts based on Ag2O
Connecting theory with experiment to understand the photocatalytic activity of CuO–ZnO heterostructure
(Elsevier, 2020-05) Oliveira, Marisa Carvalho de; Fonseca, V. S.; Andrade Neto, Nivaldo Ferreira da; Ribeiro, Renan Augusto Pontes; Silva, Elson Longo da; Lazaro, Sérgio Ricardo de; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio
Semiconductor based photocatalysis attracts wide attention because of its ability to directly utilize solar energy to degrade pollutants and convert energy, with heterojunction photocatalysts being good candidates for superior activity due to the spatial separation of photogenerated electron–hole pairs. Herein, CuO/ZnO heterostructures were successfully synthesized by a microwave-assisted hydrothermal method, with the structure, electronic and photocatalytic properties analyzed by means of experimental and theoretical methods. The X-ray diffraction patterns revealed that a CuO/ZnO heterostructure was formed, while FE-SEM analysis indicates the role of different morphologies for CuO, ZnO and CuO/ZnO heterostructures. The solar-driven photocatalytic mea-surements combined with DFT calculations indicate that CuO, as a p-type and narrow band-gap sensitizer, can make the n-type ZnO respond to visible light and promote the separation of photogenerated charge carriers by building a p-n heterogeneous structure. As a result, the CuO/ZnO heterostructure shows good promise for solar-driven photodegradation
Desenvolvimento de carreadores ambientalmente amigáveis com propriedade de liberação lenta do nitrogênio da ureia fertilizante
(2016-03-09) Souza, Iane Maiara Soares de; Delmonte, Maurício Roberto Bomio; Paskocimas, Carlos Alberto; ; ; ; Zonta, Everaldo; ; Ruiz, Juan Alberto Chavez;
O nitrogênio é um macronutriente fundamental para o crescimento vegetal. Atualmente, devido os desgastes ao longo dos anos e a elevada demanda na produção de alimentos, o solo não consegue fornecer às plantas o nitrogênio necessário para seu crescimento. Por isso, o uso de fertilizantes nitrogenados é amplamente aplicado na agricultura, onde a ureia, por possuir elevado teor de nitrogênio, é o mais usado. Contudo, suas elevadas perdas acarretadas principalmente por volatilização de amônia e lixiviação de nitrato fazem com que seja necessário o desenvolvimento de sistemas que reduzam a velocidade de hidrólise da ureia. Neste trabalho foram desenvolvidos dois tipos de fertilizante a base de ureia e carreadores, um em que a ureia foi misturada com bentonita e outro onde a ureia foi misturada com a clinoptilolta, onde para cada argilomineral foram formulados três tipos de fertilizantes, variando as proporções carreador:ureia na forma: 1:4, 1:8 e 1:16. Ainda foi formulado um terceiro fertilizante constituído somente de ureia triturada e misturada com os aditivos utilizados nas formulações como talco e solução de PVP. Todas as composições propostas foram compactadas em cilindros com diâmetro de 7mm e altura de 4mm. Os fertilizantes foram caraterizados quanto a sua morfologia, análise química e mineralogia pelas técnicas de FRX, DRX, FTIR, TG/DSC e MEV. A eficiência agronômica foi avaliada quanto as perdas de volatilizado, atingindo uma redução de 53% para Z1U16.
Desenvolvimento do pigmento condutor SnO2-Sb2O3 e sua aplicação em vidrados semicondutores
(ABCERAM, 2004-04) Aguiar, R.; Paskocimas, Carlos Alberto; Leite, Edson Roberto; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio
Esmaltes semicondutores são utilizados no recobrimento de isoladores elétricos para evitar descargas superficiais nos isoladores, associadas a grandes diferenças de potencial, proporcionando uma melhora no desempenho sob poluição ambiental. Como os vidrados utilizados nas indústrias cerâmicas são isolantes, uma maneira de torná-los semicondutores é adicionando óxidos condutores. Misturou-se ao esmalte porcentagens variadas do pigmento condutor SnO2 dopado com 5% de Sb2O3. O esmalte foi aplicado sobre peças de porcelana a verde e queimado a 1250 0C. Por microscopia eletrônica de varredura verificou-se que a concentração de pigmento na superfície das amostras é baixa e não influencia a condutividade elétrica. Na fratura, a porcentagem de pigmento ficou próxima de 35%. Assim, a superfície ficou com aspecto visual de ótima qualidade. A resistividade elétrica ocorreu pelo interior do vidrado, obtendo-se valores próximos de 104 Ohm.m
Development of ZnO/PDMS nanocomposite with photocatalytic/ hydrophobic multifunction
(Chemical Physics Letters, 2020-02) Nascimento, Maria Carolina Burgos Costa do; Santiago, Anderson de Azevedo Gomes; Gondima, Juliane Germano de Souza; Tranquilin, Ricardo Luis; Silva, Fabio S. da; Fernandez, Fernando Ferreira; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio
The polydimethylsiloxane (PDMS)/ZnO nanocomposite coatings were deposited on the borosilicate substrate by spray method. ZnO nanoparticles were synthesized by polyol method and further surface modification by functionalization with [(3-Aminopropyl)triethoxysilane] (APTS) in different concentrations (0.5, 1.0, and 1.5 ml). The results showed that there is an influence in the exposure to UV radiation and a decrease in the temperature, consequently presenting decreases in the contact angle of ZnO/PDMS nanocomposites. The 0.5 ml of APTS was the best design for ZnO/PDMS nanocomposite with photocatalytic and hydrophobic characteristics, showing a contact angle of 117° and 25% of MB discoloration in 90 min
Disclosing the structural, electronic, magnetic, and morphological properties of CuMnO2: a unified experimental and theoretical approach
(American Chemical Society, 2020-02-14) Santiago, Anderson de Azevedo Gomes; Tranquilin, Ricardo Luis; Oliveira, Marisa Carvalho de; Ribeiro, Renan Augusto Pontes; Lazaro, Sérgio Ricardo de; Corrêa, Marcio Assolin; Bohn, Felipe; Silva, Elson Longo da; Motta, Fabiana Villela da; Delmonte, Maurício Roberto Bomio
Precise control of the overall performance for solid-state materials is associated with morphological modulations which provide an alternative way to the rational design based on understanding the corresponding electronic structures of the exposed surfaces. Experimental and theoretical efforts were combined herein to elucidate the structural−property relationship of CuMnO2 nanoparticles from different morphologies. The microwave-assisted hydrothermal method was employed to synthesize these crystals with different morphologies, while first-principle quantum mechanical calculations were performed at the DFT level to obtain the structural, electronic, and magnetic properties of CuMnO2 surfaces. Our structural results have confirmed a monoclinic structure for crednerite-type CuMnO2 nanoparticles described by the Jahn−Teller-distorted octahedral [MnO6] clusters, which are connected by linear 2-fold [CuO2]. FE-SEM images combined with Wulff construction analyses indicated that CuMnO2 nanoparticles adopt a hexagonal nanoplate-like morphology which can enclose a major extent of the (100) surface with contributions from (101), (110), and (111) surfaces. Electronic structure and magnetic characterizations were discussed by the role of the corresponding electronic states of exposed surfaces which control the energy-level band diagram and spin density distribution. These results extend our fundamental understanding of the atomic processes which underpin the morphological modulations of the CuMnO2 material, thus creating a new path to obtain selected nanoparticles with desirable properties which optimize their applications
Effect of Ag clusters doping on the photoluminescence, photocatalysis and magnetic properties of ZnO nanorods prepared by facile microwave-assisted hydrothermal synthesis
(Springer, 2017-04-13) Souza, Renata Priscilla de Araújo; Motta, Fabiana Vilella da; Nascimento, José Heriberto Oliveira do; Delmonte, Maurício Roberto Bomio; Borges, Filipe Martel de Magalhães; Corrêa, Marcio Assolin; Silva, Elson Longo da; Li, Maximo Siu; Bohn, Felipe; Paskocimas, Carlos Alberto
We report a chemical route to synthesize stabilized ZnO:Ag nanoparticles (NPs) combined with nanosized metallic Ag using microwave-assisted hydrothermal synthesis. We employ X-ray diffraction (XRD), field emission guns scanning electron microscopy, transmission electron microscopy, spectrophotometry, photodegradation, photoluminescence and magnetic characterizations to investigate the structural, morphological, photocatalytic and magnetic properties of ZnO:Ag samples with different Ag concentrations. We verify through XRD results the standard wurtzite crystalline phases and face-centered cubic for metallic Ag NPs. Moreover, we confirm through spectrophotometry the photocatalysis in the samples. The Ag clusters doping the pure material causes the shift from green to yellow-red, which are lower energy wavelengths, thus corroborating changes of its electrical properties due to the decreased gap. We interpret the magnetic properties in terms of the nanosizing and similar effects. Under these conditions, we show the improvement of the photocatalytic and magnetic properties of ZnO NPs
Effect of calcium on the structural properties of Ba(1−x)Ca x TiO3 particles synthesized by complex polymerization method
(Springer, 2014-01-14) Araújo, Vinícius Dantas; Motta, Fabiana Villela da; Marques, Ana Paula de Azevedo; Paskocimas, Carlos Alberto; Delmonte, Maurício Roberto Bomio; Silva, Elson Longo da; Varela, José A.
Ferroelectric materials, such as barium titanate (BaTiO3), have been extensively studied for application in electronic and optical devices. The substitution of Ba by Ca is an effective method to improve the piezoelectricity temperature stability, as it can greatly lower the tetragonal–orthorhombic phase transition temperature, whereas the change of the Curie point is negligible. Ba(1−x)Ca x TiO3 (x = 0, 0.05, 0.10, 0.15, and 0.20) powders were prepared by complex polymerization method. The effect of calcium on the tetragonality of the BaTiO3 system was monitored using basic characterization techniques: X-ray diffraction, differential scanning calorimetry, and Raman spectroscopy. The results indicate that increased calcium contents raise the Curie temperature (T c) and that the addition of calcium in the BT matrix reduces tetragonality
Effect of different starting materials on the synthesis of Ba0.8Ca0.2TiO3
(SpringerOpen, 2015-01-31) Medeiros, P. N.; Araújo, Vinícius Dantas de; Marques, Ana Paula de Azevedo; Tranquilin, Ricardo Luis; Paskocimas, Carlos Alberto; Delmonte, Maurício Roberto Bomio; Varela, José A.; Silva, Elson Longo da; Motta, Fabiana Villela da
Literature has reported the synthesis of barium calcium titanates by various synthesis methods such as solid state reaction, co-precipitation and polymer precursors. These compounds are usually obtained using calcium carbonate (CaCO3), barium carbonate (BaCO3) and titanium oxide as starting materials. This study investigated the effect of different starting reagents on the synthesis of Ba0.8Ca0.2TiO3 (BCT) by complex polymerization method (CPM). Two sets of starting precursors were used: titanium citrate, CaCO3 and BaCO3, and titanium citrate and Ba1−x Ca x CO3 solid solution precursor. Samples were crystallized at a temperature range from 400 °C to 700 °C for different time. The obtained powders were characterized by X-ray diffraction (XRD), thermogravimetry (TG) and differential thermal analysis (DTA), and Raman and infrared spectroscopy. The infrared spectroscopy indicated that the chelation processes of Ba, Ca, Ti and CA ions are very similar. The results showed that the use of CaCO3 and BaCO3 or Ba1−x Ca x CO3 solid solution as precursors does not affect the final properties of BCT powders obtained by CPM
Effect of polyvinyl alcohol on the shape, photoluminescence and photocatalytic properties of PbMoO4 microcrystals
(Elsevier, 2014-10) Araújo, Vinícius Dantas; Tranquilin, Ricardo Luis; Motta, Fabiana Villela da; Paskocimas, Carlos Alberto; Bernardi, Maria Inês Basso; Cavalcante, L.S.; Andres, Juan; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio
For this study, lead molybdate (PbMoO4) microcrystals were prepared by the co-precipitation method and processed using a conventional hydrothermal method at 100 °C for 10 min with polyvinyl alcohol (PVA) as the capping agent. These microcrystals were structurally characterized by X-ray diffraction (XRD) and micro-Raman spectroscopy, and their morphology was investigated by field-emission gun scanning electron microscopy (FEG-SEM). The optical properties were analyzed by ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns and MR spectrum indicate that the PbMoO4 microcrystals have a scheelite-type tetragonal structure. FE-SEM images reveal that the PVA promotes the aggregation of several octahedrons and the formation of large porous stake-like PbMoO4 microcrystals which are related to the oriented attachment growth process. Moreover, the effect of the capping agent hinders the growth of a large amount of micro-octahedrons which can be verified with by several nanocrystals on large crystals. Intense green PL emission was observed at room temperature for PbMoO4 microcrystals which are related to structural defects at medium range and intermediary energy levels between the valence band (VB) and the conduction band (CB). Photocatalytic activity was observed for PbMoO4 as a catalyst in the degradation of the rhodamine B (RhB) dye, achieving total degradation after 90 min under UV-light
Effect of sintering parameters using the central composite design method, electronic structure and physical properties of yttria-partially stabilized ZrO2 commercial ceramics
(Sciendo, 2017-02-24) Paskocimas, Carlos Alberto; Mendes, A. M.; Nascimento, Maria Carolina Burgos Costa do; Araújo, V. D.; Motta, Fabiana Villela da; Acchar, Wilson; Silva, Elson Longo da; Delmonte, Maurício Roberto Bomio; Cavalcante, L. S.
In this work, the effect of sintering parameters on electronic structure and physical properties of yttria-partially stabilized ZrO2 (YPSZ) commercial ceramics has been studied using the central composite design (CCD) method. The CCD method allows using empirical modelling with better fitting, by considering the interaction between both factors. Different temperature ranges and sintering times for processing of YPSZ ceramics have been used in order to evaluate the grain growth, hardness and volumetric shrinkage by the CCD method. X-ray diffraction patterns and Rietveld refinement data indicate that non-sintered YPSZ ceramics exhibits two phases related to tetragonal and monoclinic structures, while the sintered YPSZ ceramics exhibits a single phase related to a tetragonal structure. Moreover, the monoclinic structure presents zirconium (Zr) atoms coordinated to seven oxygen (O) atoms, while in the tetragonal structure Zr atoms are coordinated to eight O atoms. Field emission scanning electron microscopy images were employed to monitor the sintering and growth process. In addition, the response surfaces obtained from calculations presented the effect of thermal and kinetic variables on the physical properties such as average grain size, volumetric shrinkage and hardness of YPSZ ceramics
Effect of temperature on the morphology and optical properties of Ag2WO4 obtained by the co-precipitation method: Photocatalytic activity
(Elsevier, 2019-08-15) Andrade Neto, Nivaldo Freire de; Oliveira, P. M.; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
In this work, Ag2WO4 was obtained at different co-precipitation temperatures (10, 30, 50, 70 e 90 °C). X-ray diffraction (XRD), X-ray fluorescence (XRF), field emission electron microscopy (SEM), chemical mapping, X- ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller method (BET) and spectroscopy in the ultraviolet region (UV–Vis) were used to characterize the Ag2WO4 particles. The photocatalytic and adsorbent activities were estimated by contact with methylene blue (MB) and methyl orange (MO) dyes. The Ag2WO4 obtained by the co-precipitation method presented monoclinic crystalline phase with nanorod morphology. The increase of the temperature favored the elongation and reduction of the thickness of the nanorods, which increased the surface area of the powders, favoring the photocatalytic and adsorptive activities. The high adsorption of the cationic molecules (MB dye), accompanied by the low anionic adsorption (MO dye), indicate the anionic character of the Ag2WO4 nanorods. In addition, the AW90 sample showed the best result in the reuse tests, where it lost only 5% of its efficiency in the fourth cycle
Effect of temperature on the photocatalytic properties of TiO2 -CeO2 multilayer thin films obtained by spin coating method
(ABCERAM, 2020) Nunes, T. B. O.; Andrade Neto, Nivaldo Freire de; Garcia, Laurênia Martins Pereira; Nascimento, Rubens Maribondo do; Delmonte, Maurício Roberto Bomio; Motta, Fabiana Villela da
TiO2-CeO2 multilayer thin films were deposited by the spin coating method and calcined at 500 and 700 °C. Thin films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and diffuse reflectance spectroscopy. Photocatalytic properties were estimated by varying the concentration of the methylene blue dye (MB) when illuminated by UV radiation. The XRD patterns showed that the temperatures of 500 and 700 °C were effective to obtain TiO2 and CeO2 phases. The difference in the homogeneity of TiO2 and CeO2 films was evident in the AFM images, where the films showed an average roughness of 2.0 and 5.3 nm, respectively. The CeO2 -TiO2 thin film obtained at 700 °C showed the best photocatalytic activity, reducing the concentration of MB by approximately 80%, while the CeO2 and TiO2 films obtained at 700°C reduced only 20% and 29%, respectively. The reuse test showed that the thin films maintained their photocatalytic activity after 4 cycles, and there was no need for thermal treatment, indicating that it is an immobilized photocatalyst with high efficiency in the degradation of organic dyes

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