Guaratinguetá - FEG - Faculdade de Engenharia e Ciências

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Avaliação de parâmetros mais adequados à obtenção de compósitos termoplásticos via moldagem por compressão a quente
(Universidade Estadual Paulista (Unesp), 2023-11-10) Castilho, André Luiz Guimarães de ; Botelho, Edson Cocchieri ; Costa, Michelle Leali
Nos últimos anos têm sido observado um desenvolvimento progressivo em aplicações leves e sustentáveis na indústria automotiva. Neste contexto, os polímeros reforçados com fibras de carbono (CFRP – do inglês Carbon Fiber Reinforced Polymer) têm atraído a atenção desta indústria principalmente devido às suas propriedades como resistência mecânica superior aos metais, rigidez e leveza, oferecendo uma redução significativa no peso final do veículo e, consequentemente, reduzindo a emissão de CO2 e ocasionando a redução do consumo de combustível. O presente trabalho visa avaliar a influência dos parâmetros de reprocessamento na cristalização e nas propriedades mecânicas de um CFRP fabricado a partir de um semipreg comercial constituído de matriz de poliamida 6 reforçada com tecido de fibra de carbono do tipo twill, 2x2. A partir da caracterização térmica do semipreg (calorimetria exploratória diferencial (DSC) e análise termogravimétrica (TGA)), foi possível definir ciclos de processamento e com diferentes taxas de resfriamento para gerar uma provável variação na cristalização do compósito final. Além disso, com base nos resultados obtidos a partir da caracterização térmica, foi conduzido um estudo da cinética de cristalização do semipreg por meio do método isotérmico e não isotérmico. Após o estabelecimento do ciclo de processamento, lâminas de semipreg foram empilhadas na espessura desejada e processadas via técnica de moldagem por compressão a quente. Os compósitos obtidos foram qualificados por inspeção via ultrassom tipo C-scan, e por digestão ácida. Os compósitos também foram avaliados por ensaios mecânicos como: análises dinâmico-mecânica (DMA); resistências ao cisalhamento interlaminar (ILSS), à tração e à excitação por impulso. Os resultados mostram que foi possível realizar o estudo da cinética de cristalização no modo dinâmico, porém o modelo de Avrami não foi adequado para o estudo da cinética no modo isotérmico. Os compósitos reprocessados apresentaram um aumento de 12% na resistência à tração; de 12% no ILSS e de 17% no módulo de elasticidade obtido por excitação por impulso. Tal fato está associado a um possível aumento da cristalinidade da matriz de PA6 no reprocessamento, e consequente, aumento da rigidez do compósito.
O alcance das tecnologias 4.0 na contabilidade: a experiência de um centro de serviços compartilhado
(Universidade Estadual Paulista (Unesp), 2024-05-06) Rezende, Ricardo Lombardi ; Santos, David Ferreira Lopes ; Campos, Renato
As tecnologias 4.0 transcenderam a área industrial e podem ser vistas em diversos setores da economia, incluindo nas atividades da contabilidade. No entanto, o alcance de aplicação e os resultados da utilização das tecnologias 4.0 na contabilidade realizada no interior das empresas ainda é um campo com informações teóricas e empíricas restritas. Por isso, esse estudo tem como objetivo avaliar o alcance dos impactos das tecnologias 4.0 nas atividades da contabilidade e seus reflexos na organização executadas por um Centro de Serviço Compartilhado. Para tanto, essa pesquisa tem como estratégia metodológica o uso de um estudo de caso único, considerando a oportunidade de explorar o objetivo com profundidade, tendo em vista, a possibilidade de utilizar diferentes técnicas para coleta e tratamento dos dados junto a uma realidade empresarial. Combinou-se assim, métodos quantitativos e qualitativos para tratar os dados tomados a partir de observação direta, análise de documentos e procedimentos internos, entrevistas com gestores e questionário aplicado para os profissionais da contabilidade. Para análise qualitativa utilizou-se a análise de conteúdo que será suportada com o uso de análise de similitude e frequência de palavras. Para análises quantitativas foram utilizadas estatísticas descritivas e análise fatorial exploratória. Os resultados preliminares indicam que a aplicação de tecnologias 4.0 com robôs para automação dos processos contábeis, inteligência artificial, integração de sistemas, mobilidade e análise de dados permite uma gestão mais eficiente que possibilita tomar a melhor decisão para a empresa. A utilização dessas tecnologias nos processos manuais e repetitivos do setor contábil permitiram aos profissionais da contabilidade dedicarem-se as atividades estratégicas e analíticas, minimizando a possibilidade de irregularidades contábeis, detectando possíveis fraudes, além de permitir uma rápida análise de dados, mais embasada e precisa. O estudo ainda demonstrou que com a capacitação dos profissionais contábeis possibilitou aproveitar o potencial das tecnologias implementadas, além de permitir o uso de ferramentas de comunicação, plataformas de compartilhando de documentos e videoconferência, permitindo o trabalho de forma remota, aumentando a flexibilidade e a eficiência. Observa-se que com a implementação de tecnologias 4.0 há uma mudança significativa no setor contábil de um centro de serviço compartilhado, possibilitando que a empresa aumente sua eficiência, confiabilidade, transparência e governança.
(130) Elektra Delta - on the stability of the new third moonlet
(2023-07-01) Valvano, G. ; Oliveira, R. Machado ; Winter, O. C. ; Sfair, R. ; Borderes-Motta, G. ; Universidade Estadual Paulista (UNESP) ; Eberhard Karls Universität Tübingen ; Universidad Carlos III de Madrid ; Kiruna
The aim of this work is to verify the stability of the proposed orbital solutions for the third moonlet (Delta) taking into account a realistic gravitational potential for the central body of the quadruple system (Alpha). We also aim to estimate the location and size of a stability region inside the orbit of Gamma. First, we created a set of test particles with intervals of semimajor axis, eccentricities, and inclinations that covers the region interior to the orbit of Gamma, including the proposed orbit of Delta and a wide region around it. We considered three different models for the gravitational potential of Alpha: irregular polyhedron, ellipsoidal body, and oblate body. For a second scenario, Delta was considered a massive spherical body and Alpha an irregular polyhedron. Beta and Gamma were assumed as spherical massive bodies in both scenarios. The simulations showed that a large region of space is almost fully stable only when Alpha was modelled simply as an oblate body. For the scenario with Delta as a massive body, the results did not change from those as mass-less particles. Beta and Gamma do not play any relevant role in the dynamics of particles interior to the orbit of Gamma. Delta's predicted orbital elements are fully unstable and far from the nearest stable region. The primary instability source is Alpha's elongated shape. Therefore, in the determination of the orbital elements of Delta, it must be taken into account the gravitational potential of Alpha assuming, at least, an ellipsoidal shape.
Erratum: Kinetic and viscoelastic study of liquid thermoplastic matrix based on methyl methacrylate copolymers (Materials Research 26 (e20210619) DOI: 10.1590/1980-5373-MR-2021-0619)
(2023-01-01) Silveira, Daniel Consoli ; da Silva Braga, Tiago Teixeira ; dos Santos Conejo, Luiza ; Ancelotti Junior, Antônio Carlos ; Costa, Michelle Leali ; Botelho, Edson Cocchieri ; Universidade Estadual Paulista (UNESP) ; Instituto de Engenharia Mecânica ; Laboratório de Estruturas Leves
In the legend of figures 2 and 3, where it was written: Figure 2. Heat flow vs. time curves for reactions with the autocatalytic mechanism of the polymeric systems. Figure 3. Dynamic DSC of MMA systems and BzO initiator in different concentrations. Should read: Figure 2. Heat flow vs. time curves (exo up) for reactions with the autocatalytic mechanism of the polymeric systems. Figure 3. Dynamic DSC of MMA systems and BzO initiator in different concentrations (exo up).
The influence of a close secondary star on the planetary formation: The case of γ cephei b
(2023-07-01) Camargo, B. C.B. ; Kley, W. ; Winter, O. C. ; Universidade Estadual Paulista (UNESP) ; Universität Tübingen
The formation of planets around a single star is a complex process that depends on many parameters. Planetary systems with a secondary star too close to the primary star can significantly complicate the process. In this work, we explored the formation of γ Cephei b, a giant planet located in a close binary system, using a hydrodynamic approach. We tested different parameters for the discs and protoplanet in an attempt to reproduce the observed features. We found that in situ formation can reach the observational mass of the planet. Both isothermal and radiative disc conditions exhibited similar planetary evolution. However, our results demonstrated a high planetary eccentricity. To understand this behaviour, we applied secular theory to the γ Cephei system. We found that the system can reproduce the observational and simulated values of eccentricities.
The dynamics of co-orbital giant exomoons - applications for the Kepler-1625 b and Kepler-1708 b satellite systems
(2023-04-01) Moraes, R. A. ; Borderes-Motta, G. ; Winter, O. C. ; Mourão, D. C. ; Universidade Estadual Paulista (UNESP) ; Bioengineering and Aerospace Engineering Department ; Swedish Institute of Space Physics
Exomoons are a missing piece of exoplanetary science. Recently, two promising candidates were proposed, Kepler-1625 b-I and Kepler-1708 b-I. While the latter still lacks a dynamical analysis of its stability, Kepler-1625 b-I has already been the subject of several studies regarding its stability and origin. Moreover, previous works have shown that this satellite system could harbour at least two stable massive moons. Motivated by these results, we explored the stability of co-orbital exomoons using the candidates Kepler-1625 b-I and Kepler-1708 b-I as case studies. To do so, we performed numerical simulations of systems composed of the star, planet, and the co-orbital pair formed by the proposed candidates and another massive body. For the additional satellite, we varied its mass and size from a Mars-like to the case where both satellites have the same physical characteristics. We investigated the co-orbital region around the Lagrangian equilibrium point L4 of the system, setting the orbital separation between the satellites from θmin = 30◦ to θmax = 90◦. Our results show that stability islands are possible in the co-orbital region of Kepler-1708 b-I as a function of the co-orbital companion's mass and angular separation. Also, we identified that resonances of librational frequencies, especially the 2:1 resonance, can constrain the mass of the co-orbital companion. On the other hand, we found that the proximity between the host planet and the star makes the co-orbital region around Kepler-1625 b-I unstable for a massive companion. Finally, we provide TTV profiles for a planet orbited by co-orbital exomoons.
Imbalanced classification applied to asteroid resonant dynamics
(2023-01-01) Carruba, V. ; Aljbaae, S. ; Caritá, G. ; Lourenço, M. V.F. ; Martins, B. S. ; Alves, A. A. ; Universidade Estadual Paulista (UNESP) ; Division of Space Mechanics and Control
Introduction: Machine learning (ML) applications for studying asteroid resonant dynamics are a relatively new field of study. Results from several different approaches are currently available for asteroids interacting with the z2, z1, M1:2, and ν6 resonances. However, one challenge when using ML to the databases produced by these studies is that there is often a severe imbalance ratio between the number of asteroids in librating orbits and the rest of the asteroidal population. This imbalance ratio can be as high as 1:270, which can impact the performance of classical ML algorithms, that were not designed for such severe imbalances. Methods: Various techniques have been recently developed to address this problem, including cost-sensitive strategies, methods that oversample the minority class, undersample the majority one, or combinations of both. Here, we investigate the most effective approaches for improving the performance of ML algorithms for known resonant asteroidal databases. Results: Cost-sensitive methods either improved or had not affect the outcome of ML methods and should always be used, when possible. The methods that showed the best performance for the studied databases were SMOTE oversampling plus Tomek undersampling, SMOTE oversampling, and Random oversampling and undersampling. Discussion: Testing these methods first could save significant time and efforts for future studies with imbalanced asteroidal databases.
Assessing the spin-orbit obliquity of low-mass planets in the breaking the chain formation model: a story of misalignment
(2023-06-01) Esteves, Leandro ; Izidoro, André ; Winter, Othon C ; Bitsch, Bertram ; Isella, Andrea ; Universidade Estadual Paulista (UNESP) ; Rice University ; Max-Planck-Institut für Astronomie
The spin-orbit obliquity of a planetary system constraints its formation history. A large obliquity may either indicate a primordial misalignment between the star and its gaseous disc or reflect the effect of different mechanisms tilting planetary systems after formation. Observations and statistical analysis suggest that system of planets with sizes between 1 and 4 R has a wide range of obliquities (∼0-30°), and that single- and multiplanet transiting have statistically indistinguishable obliquity distributions. Here, we revisit the 'breaking the chains' formation model with focus in understanding the origin of spin-orbit obliquities. This model suggests that super-Earths and mini-Neptunes migrate close to their host stars via planet-disc gravitational interactions, forming chain of planets locked in mean-motion resonances. After gas-disc dispersal, about 90-99 per cent of these planetary systems experience dynamical instabilities, which spread the systems out. Using synthetic transit observations, we show that if planets are born in discs where the disc angular momentum is virtually aligned with the star's rotation spin, their final obliquity distributions peak at ∼5° or less, and the obliquity distributions of single- and multiplanet transiting systems are statistically distinct. By treating the star-disc alignment as a free-parameter, we show that the obliquity distributions of single- and multiplanet transiting systems only become statistically indistinguishable if planets are assumed to form in primordially misaligned natal discs with a tilt' distribution peaking at ≥10-20°. We discuss the origin of these misalignments in the context of star formation and potential implications of this scenario for formation models.
Experimental Development of Calcium Looping Carbon Capture Processes: An Overview of Opportunities and Challenges
(2023-05-01) Toledo, Rubens C. ; Arce, Gretta L. A. F. ; Carvalho, João A. ; Ávila, Ivonete ; Universidade Estadual Paulista (UNESP)
Global warming might be mitigated if emissions were interrupted through carbon capture technologies, as there is a significant amount of comprehensive studies on them. An outline of the main gaps and trends of a technology is critical for further development. In this context, this study provides an overview of calcium looping carbon capture processes that have proven their potential and commercial viability. A bibliometric analysis is conducted on both Scopus and Web of Science database by seeking the keywords “calcium looping”, “co2 capture”, and “fluidized bed” in titles, abstracts, and keywords. Word selection was based on a list of relevant papers on the topic. These items of data have been processed and analyzed based on the number of publications and citations by emphasizing recent publication evolution, journal influence, the use of specific keywords, and co-citation. Results reveal that the European Union (EU) leads the rankings on the topic, followed by Canada. Keyword choice might have affected the number of citations. Recent studies used limestone as a sorbent and a dual fluidized bed reactor with a calciner or resistance depending on its size. Most studies are focused on technology scale-up. Although scale-up seems to be a priority, multiple studies are designed to assess the effect of steam generation and SO (Formula presented.) on the process.
Contributions of Annex SL to Corporate Sustainability
(2021-01-01) Nunhes, Thaís Vieira ; Campos, Thalita Láua Reis ; Francisco, Fernanda Ellen ; Oliveira, Otávio José de ; Universidade Estadual Paulista (UNESP)
With the advance of globalization and population increase, it was necessary to intensify the production of goods to meet the new demands that arose. As a result, a significant emergence of negative socio-environmental impacts was observed, affecting the entire planet. The UN launched the 2030 Agenda to encourage all sectors of the economy, including the industrial sector, in promoting Sustainable Development (SD). Companies have sought to adopt techniques, tools and practices that enable SD in organizations. Among the range of possibilities to operationalize sustainable management, there are the Certifiable Management Systems (CMSs) ISO 9001, ISO 14001, and ISO 45001. In order to facilitate the integration between these systems, ISO launched in 2018 the Annex SL with the High-Level Structure (HLS), providing greater compatibility between them. However, most companies do not know enough about this change and its benefits for sustainability. Thus, this work presents the main contributions of Annex SL to the development of sustainability in companies that have implemented CMSs. By reviewing the literature on the relationship between CMSs and sustainability, and the expertise of the authors, it was possible to identify and discuss on the contributions of the main elements of the HLS to sustainability, which are organizational context analysis, risk management, evidence-based decision making, emphasis on measuring and evaluating processes and results, and a culture of integration and continuous improvement.
Kinetic and Viscoelastic Study of Liquid Thermoplastic Matrix Based on Methyl Methacrylate Copolymers
(2023-01-01) Silveira, Daniel Consoli ; da Silva Braga, Tiago Teixeira ; dos Santos Conejo, Luiza ; Junior, Antônio Carlos Ancelotti ; Costa, Michelle Leali ; Botelho, Edson Cocchieri ; Universidade Estadual Paulista (UNESP) ; Instituto de Engenharia Mecânica ; Laboratório de Estruturas Leves
The industries that have polymers as an important raw material in their production, such as the construction, automotive, electrical and electronic sectors, always seek innovations to cut costs, reduce weight, easiness of processing, maximizing mechanical properties, and recyclability. In this context, this work presents the study of the kinetic parameters and viscoelastic behavior of a new thermoplastic system initially liquid. Through differential scanning calorimetry (DSC) analysis, Brookfield viscosimetry; dynamic-mechanical analysis (DMA) and mathematical modeling with consolidated and standardized methods, it was possible to evaluate the polymerization kinetics and viscoelastic behavior of the material in solutions with different concentrations. The generated equations allow the prediction of the kinetic and gelation behavior of the material reducing the need for laboratory tests to determine polymer properties. The found results showed that concentrations of benzoyl peroxide initiator with 1wt% in the methyl methacrylate (MMA) copolymer solution have the best viscoelastic and dynamic-mechanical properties with a less expensive polymerization cycle.
Relationship among morphology, photoluminescence emission, and photocatalytic activity of Eu-doped ceria nanostructures: A surface-type effect
(2023-01-01) Ortega, P. P. ; Amoresi, R. A.C. ; Teodoro, M. D. ; Longo, E. ; Ponce, M. A. ; Simões, A. Z. ; Universidade Estadual Paulista (UNESP) ; Universidade Federal do ABC (UFABC) ; Universidade Federal de São Carlos (UFSCar) ; National Research Council (CONICET)
Herein, we discuss the synthesis of Eu-doped ceria nanostructures via the microwave-assisted hydrothermal method. The morphological analysis showed that Eu-doped ceria nanoparticles, nanorods, nanocubes, and nanopolyhedrons with different sets of exposed facets were obtained. The structural characterization revealed that the samples were crystalline and without secondary phases. The optical analysis showed a decrease in the bandgap energies of the Eu-doped nanostructures compared with pure ceria nanoparticles, and different photoluminescence emissions were found depending on the morphology. The photocatalytic activity of each nanostructure was evaluated, and Eu-doped nanopolyhedrons were the most promising photocatalyst, exhibiting a 60% and 80% increase in RhB discoloration compared to the Eu-doped and pure ceria nanoparticles, respectively. The better performance of the nanopolyhedrons is probably associated with the presence of different exposed facets, such as (111), (200), (220), and (311). The main species involved in the photocatalytic process were holes. The performances of each nanostructure were associated with their different exposed facets, the concentration of oxygen vacancies, and surface defects.
On the gas heating effect of helium atmospheric pressure plasma jet
(2023-05-01) do Nascimento, Fellype ; Gerling, Torsten ; Kostov, Konstantin Georgiev ; Universidade Estadual Paulista (UNESP) ; Leibniz Institute for Plasma Science and Technology-INP
Plasma medicine is an emerging research field which has been driven by the development of plasma sources suitable to generate low temperature plasmas. In many cases, such devices can operate without a gas flow, producing a plasma discharge from the ambient air. However, the most common case is the use of a working gas at a given flow rate to produce a plasma jet. Helium (He) is one of the gases commonly used as the carrier gas to generate cold atmospheric pressure plasma jets (CAPPJs) due mainly to the easiness to ignite a gas discharge with it. However, in this work it was observed that most of the heating of a He CAPPJ can come just from the expansion of the He gas. This was found through measurements of gas temperature (T gas ), using fiber optic temperature (FOT) sensors, and thermal output, using both FOT and infrared imaging with the He flow impinging on a copper (Cu) plate. Such findings were achieved through comparisons of T gas and the temperature on the Cu (T Cu ) plate in the conditions with and without discharge ignition, as well as comparing T gas in the free gas/jet mode with and without discharge ignition. It was verified that the T gas values increased as the distance from the gas outlet was enlarged, especially at low He flow rates, even without discharge ignition. Despite the temperature increase with distance, it is possible to produce plasma jets with temperatures lower than 40 °C at low He flow rates.
Unveiling the metal-insulator transition at YTiO3/LaTiO3 interfaces grown by the soft chemical method
(2023-07-01) Tolentino Cabral, Ana Cristina ; Tafur Tanta, Urbano Miguel ; Simões, Alexandre Zirpoli ; Bastos, Wagner ; Moreno, Henrique ; Ramirez, Miguel Angel ; Ponce, Miguel Adolfo ; Moura, Francisco ; Federal University of Itajubá ; Universidade Estadual Paulista (UNESP) ; Universidade Federal de São Carlos (UFSCar) ; CONICET-Universidad Nacional de Mar del Plata
In the last couple of years, perovskites and transition metal oxides have demonstrated high potential for energy storage/processing applications. Oxide interfaces with piezoelectric, magnetic and metal-insulator transition based on YTiO3/LaTiO3 heterostructured films were investigated in this work. The Mott insulator, YTiO3, was deposited onto a Mott insulator, LaTiO3, via polymeric precursor method. Spin coating was performed to obtain a YTiO3/LaTiO3 heterostructed thin films deposited onto Pt/TiO2/SiO2/Si substrates. Structure, morphology, and electrical properties of the films were assessed. The YTiO3/LaTiO3 heterostructures exhibit ferromagnetic and piezoelectric behavior (d33máx≈8.11 p.m./V), which may be attributed to smaller grain (average grain size≈20.00 nm) and, thus, a higher grain boundary density, and stress in the film plane due to the different properties of the interface. The dielectric permittivity and dielectric loss at 1 KHz were found to be 70 and 0.41, respectively. I–V measurements on different electrode areas confirmed a metal-to-insulator transition, indicating a potential aplication in correlated electron random access memory (CeRAM).
The Santa Filomena meteorite shower: Trajectory, classification, and opaque phases as indicators of metamorphic conditions
(2023-05-01) Tosi, Amanda ; Zucolotto, Maria Elizabeth ; Andrade, Diana Paula ; Winter, Othon Cabo ; Mourão, Daniela Cardozo ; Sfair, Rafael ; Ziegler, Karen ; Perez, Pablo Daniel ; Suarez, Sergio ; Ornellas, Iara Deniz ; Zurita, Marcelo ; Mendes, Julio Cezar ; Kellner, Alexander Wilhelm ; Wolff, Wania ; Universidade Federal do Rio de Janeiro (UFRJ) ; Universidade Estadual Paulista (UNESP) ; Eberhard Karls Universität Tübingen ; University of New Mexico ; Centro Atomico Bariloche (CONICET) ; Brazilian Meteor Observation Network
On August 19, 2020, at 13:18—UTC, a meteor event ended as a meteorite shower in Santa Filomena, a city in the Pernambuco State, northeast Brazil. The heliocentric orbital parameters resulting from images by cameras of the weather broadcasting system were semimajor axis a = 2.1 ± 0.1 au, eccentricity e = 0.55 ± 0.03, and inclination i = 0.15o ± 0.05. The data identified the body as an Apollo object, an Earth-crossing object with a pericenter interior to the Earth's orbit. The chemical, mineralogical, and petrological evaluations, as well as the physical analysis, followed several traditional techniques. The meteorite was identified as a H5-6 S4 W0 ordinary chondrite genomict breccia. The large amount of metal in the meteorite made a metallographic evaluation based on the opaque phases possible. The monocrystalline kamacite crystals suggest a higher petrological type and the distorted Neumann lines imply at least two different shock events. The absence of the plessite phase shows that the meteorite did not reach the highest shock levels S5 and S6. The well-defined polycrystalline taenite is indicative of petrologic types 4 and 5 due to the conserved internal tetrataenite rim at the boundaries. The presence of polycrystalline taenites and the characteristics of the Agrell Effect suggest that the Santa Filomena meteorite did not reheat above 700°C. The absence of martensite confirms reheating temperatures <800°C and a slow cooling rate. The Ni contents and sizes of the zoned taenite particles indicate a slow cooling rate ranging from 1 to 10 K Myr−1.
Disclosing the nature of vacancy defects in α-Ag2WO4
(2023-08-01) Assis, M. ; Castro, M. S. ; Aldao, C. M. ; Buono, C. ; Ortega, P. P. ; Teodoro, M. D. ; Andrés, J. ; Gouveia, A. F. ; Simões, A. Z. ; Longo, E. ; Macchi, C. E. ; Somoza, A. ; Moura, F. ; Ponce, M. A. ; Universidade Federal de São Carlos (UFSCar) ; University Jaume I (UJI) ; University of Mar del Plata and National Research Council (CONICET) ; Universidade Estadual Paulista (UNESP) ; Institute of Materials Physics of Tandil - IFIMAT (UNCPBA) and CIFICEN (UNCPBA-CICPBA-CONICET) ; Federal University of Itajubá
Defects at semiconductors with electron acceptor and donor sites govern the electronic and optoelectronic applications due to their unique electronic properties. This work provides deep insight into the nature of defects and the conduction mechanism in α-Ag2WO4. To this aim, a detailed analysis of the results of XRD with Rietveld refinements, FE-SEM images, and measurements of different spectroscopies (impedance, positron annihilation lifetime, and photoluminescence) are carried out on α-Ag2WO4 samples synthesized by a simple co-precipitation method. Two types of vacancy defects: cationic O-vacancies, and anionic Ag or Ag–O vacancy complexes are elucidated with a Schottky p-type potential barrier. The results indicate that the Ag vacancies remain constant during thermal treatment, while an opposite effect is found for the oxygen vacancies. This behavior governs the multifunctional properties of α-Ag2WO4 semiconductors via a tunneling plus thermionic conduction mechanism.
Effect of chemical potential on the structural modification of titanate-based photocatalysts: Fast dye degradation efficiency and adsorption power
(2023-06-25) Pereira, Chrystopher A.M. ; Amoresi, Rafael A.C. ; Teixeira, Guilhermina F. ; Oliveira, Regiane C. ; Coleto Jr, Ubirajara ; da Luz, Angélica R. ; de Almeida, Priscila B. ; Simões, Alexandre Z. ; Monteiro Filho, Elias S. ; Longo, Elson ; Perazolli, Leinig A. ; Universidade Estadual Paulista (UNESP) ; Universidade Federal do ABC (UFABC) ; Universidade Federal de Goiás (UFG) ; Universidade Federal de São Carlos (UFSCar) ; Federal Institute of São Paulo (IFSP)
In this work, the impact of the chemical potential of sodium hydroxide concentration was evaluated in the synthesis of titanate-based photocatalysts prepared by the microwave-assisted hydrothermal method. The materials were characterized by techniques that made it possible to unveil their structural, morphological, and electronic properties, corroborating the formation of a heterojunction of sodium titanate (Na2Ti6O13) and hydrated hydrogen titanate (H2Ti3O7·H2O). The results demonstrated that the increased chemical potential of NaOH caused an ionic exchange between Na+ and H+ ions, making the H2Ti3O7·H2O phase more stable. The oriented attachment (OA) growth mechanism was predominant, resulting in nanoparticles with nanosheet-like morphology. The photocatalytic efficiency of the materials was tested for the discoloration of Rhodamine B (RhB) and Methylene Blue (MB) dyes. The photocatalyst with the best efficiency showed a half-life time for RhB discoloration of only 5 min and a high capacity of adsorption in the MB medium (∼90% in 10 min). The details of the nanoparticle growth mechanism, the charge transport in the heterojunction, and the stability and reusability of the materials were clarified.
Mechanical Properties, Corrosion Behavior, and In Vitro Cell Studies of the New Ti-25Ta-25Nb-5Sn Alloy
(2023-03-01) Silva, Kerolene Barboza da ; Carobolante, João Pedro Aquiles ; Rajan, S. Sudhagara ; Júnior, Celso Bortolini ; Sabino, Roberta Maia ; Seixas, Maurício Rangel ; Nakazato, Roberto Zenhei ; Popat, Ketul C. ; Claro, Ana Paula Rosifini Alves ; Universidade Estadual Paulista (UNESP) ; Colorado State University (CSU)
This study aims to characterize a new Ti-25Ta-25Nb-5Sn alloy for biomedical application. Microstructure, phase formation, mechanical and corrosion properties, along with the cell culture study of the Ti-25Ta-25Nb alloy with Sn content 5 mass% are presented in this article. The experimental alloy was processed in an arc melting furnace, cold worked, and heat treated. For characterization, optical microscopy, X-ray diffraction, microhardness, and Young’s modulus measurements were employed. Corrosion behavior was also evaluated using open-circuit potential (OCP) and potentiodynamic polarization. In vitro studies with human ADSCs were performed to investigate cell viability, adhesion, proliferation, and differentiation. Comparison among the mechanical properties observed in other metal alloy systems, including CP Ti, Ti-25Ta-25Nb, and Ti-25Ta-25-Nb-3Sn showed an increase in microhardness and a decrease in the Young’s modulus when compared to CP Ti. The potentiodynamic polarization tests indicated that the corrosion resistance of the Ti-25Ta-25Nb-5Sn alloy was similar to CP Ti and the experiments in vitro demonstrated great interactions between the alloy surface and cells in terms of adhesion, proliferation, and differentiation. Therefore, this alloy presents potential for biomedical applications with properties required for good performance.
Experimental Study on Mineral Dissolution and Carbonation Efficiency Applied to pH-Swing Mineral Carbonation for Improved CO2 Sequestration
(2023-03-01) Galina, Natália R. ; Arce, Gretta L. A. F. ; Maroto-Valer, Mercedes ; Ávila, Ivonete ; Universidade Estadual Paulista (UNESP) ; Heriot-Watt University
Mineral carbonation incurs high operating costs, as large amounts of chemicals and energy must be used in the process. Its implementation on an industrial scale requires reducing expenditures on chemicals and energy consumption. Thus, this work aimed to investigate the significant factors involved in pH-swing mineral carbonation and their effects on CO2 capture efficiency. A central composite rotatable design (CCRD) was employed for optimizing the operational parameters of the acid dissolution of serpentinite. The results showed that temperature exerts a significant effect on magnesium dissolution. By adjusting the reaction temperature to 100 °C and setting the hydrochloric acid concentration to 2.5 molar, 96% magnesium extraction was achieved within 120 min of the reaction and 91% within 30 min of the reaction. The optimal efficiency of carbon dioxide capture was 40–50%, at higher values than those found in literature, and 90% at 150 bar and high pressures. It was found that it is technically possible to reduce the reaction time to 30 min and maintain magnesium extraction levels above 90% through the present carbonation experiments.
Physicochemical Characterization and Thermal Behavior of Different Wood Species from the Amazon Biome
(2023-03-01) Bimestre, Thiago Averaldo ; Silva, Fellipe Sartori ; Tuna, Celso Eduardo ; dos Santos, José Carlos ; de Carvalho, João Andrade ; Canettieri, Eliana Vieira ; Universidade Estadual Paulista (UNESP) ; Associated Laboratory of Combustion and Propulsion—LCP/INPE
The Brazilian Amazon is one of the main tropical wood-producing regions in the world, where exploration and industrial processing are among its main economic activities. Wood is characterized as a material consisting mainly of compounds with a high degree of polymerization and molecular weight such as cellulose, hemicellulose and lignin, in addition to other compounds such as ash and extractives. This chemical complexity of wood brings with it a wide possibility of chemical and thermochemical processing aiming at the production of bioproducts and biofuels. In this context, it is essential to know the physicochemical properties and thermal behavior of wood species from the Amazon biome to add value to the product, reducing waste and maximizing the species used. This work presents an investigation into the physicochemical and thermogravimetric characteristics of 21 species of wood from the Amazon, in addition to the determination of the higher heating value (HHV) of each one of them, focusing on the energy use of the biomass under analysis. The samples showed a high lignin content, varying between 26.8% and 33.9%, with a standard deviation of 1.7% and an average of 30.0%. The Trattinnickia sp. had the highest lignin content (33.86 ± 0.13%). The cellulose content varied from 31.3% to 55.9%, with a standard deviation of 7.3% and an average of 41.74%. The Ruizterania albiflora had the highest cellulose content (55.90 ± 1.20%). For the hemicellulose content, the variation ranged from 8.6% to 17.0%, with a standard deviation of 2.6% and an average of 12.38%. The samples that showed the highest HHVs were Ocotea sp. (18.588 ± 0.082 MJ kg−1) followed by Ferreiraa spectabilis (18.052 ± 0.157 MJ kg−1).

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