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  • ItemErrata
    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 [UNESP]; da Silva Braga, Tiago Teixeira [UNESP]; dos Santos Conejo, Luiza [UNESP]; Ancelotti Junior, Antônio Carlos; Costa, Michelle Leali [UNESP]; Botelho, Edson Cocchieri [UNESP]; 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).
  • ItemArtigo
    Kinetic and Viscoelastic Study of Liquid Thermoplastic Matrix Based on Methyl Methacrylate Copolymers
    (2023-01-01) Silveira, Daniel Consoli [UNESP]; da Silva Braga, Tiago Teixeira [UNESP]; dos Santos Conejo, Luiza [UNESP]; Junior, Antônio Carlos Ancelotti; Costa, Michelle Leali [UNESP]; Botelho, Edson Cocchieri [UNESP]; 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.
  • ItemArtigo
    Relationship among morphology, photoluminescence emission, and photocatalytic activity of Eu-doped ceria nanostructures: A surface-type effect
    (2023-01-01) Ortega, P. P. [UNESP]; Amoresi, R. A.C. [UNESP]; Teodoro, M. D.; Longo, E.; Ponce, M. A.; Simões, A. Z. [UNESP]; 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.
  • ItemArtigo
    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 [UNESP]; Bastos, Wagner; Moreno, Henrique [UNESP]; Ramirez, Miguel Angel [UNESP]; 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).
  • ItemArtigo
    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. [UNESP]; Teodoro, M. D.; Andrés, J.; Gouveia, A. F.; Simões, A. Z. [UNESP]; 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.
  • ItemArtigo
    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. [UNESP]; Amoresi, Rafael A.C. [UNESP]; Teixeira, Guilhermina F.; Oliveira, Regiane C.; Coleto Jr, Ubirajara; da Luz, Angélica R. [UNESP]; de Almeida, Priscila B.; Simões, Alexandre Z. [UNESP]; Monteiro Filho, Elias S. [UNESP]; Longo, Elson; Perazolli, Leinig A. [UNESP]; 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.
  • ItemCapítulo de livro
    Oxygen defects, morphology, and surface chemistry of metal oxides: a deep insight through a joint experimental and theoretical perspective
    (2022-01-01) Ciola Amoresi, Rafael Aparecido [UNESP]; Coleto Junior, Ubirajara; Simões, Alexandre Zirpoli [UNESP]; Perazolli, Leinig Antonio [UNESP]; Longo, Elson; Andrés, Juan; Universidade Estadual Paulista (UNESP); Universidade Federal do ABC (UFABC); Universidade Federal de São Carlos (UFSCar); Jaume I University - UJI
    Comprehending the relationship between structure and function of materials is the main goal of materials science for the rational design of their enhanced performance. Despite being unavoidable, defects in materials are not considered an enemy of materials anymore, as some beneficial effects regarding their optimal properties, and consequently potential applications, have been observed. This suggests that the presence of defects is far from being completely understood. In this context, studying the basic interactions of defects in materials can provide a deeper comprehension of this conundrum. Thus, the consonance between the deviations of real materials and the ideal models are constant challenges to be addressed in solid-state science, which has for many decades demanded intense efforts from researchers regarding the control and exploitation of such imperfections. On the other hand, the morphology of materials is generally considered the key to modulate their functional properties. However, for semiconducting structures, morphology is as important as size and composition for the determination of the electronic structure. The exposed surfaces at the morphology are closely related to the physicochemical properties and distinct from the bulk of the material because they are constituted of undercoordinated atoms corresponding to oxygen vacancies and defects. The morphology control and manipulation at each exposed surface with a given surface energy provides a degree of freedom for harvesting and tailoring the functional properties of metal oxides, but this is usually a nontrivial task. Therefore, it is fundamental to understand how the local coordination of atoms at the exposed surfaces, that is, undercoordinated clusters of semiconductor metal oxides with oxygen vacancies, impacts the chemistry and physics of these semiconductors. Here, we investigate the relationship among oxygen defects, morphology, and surface chemistry of metal oxides using a combined experimental and theoretical strategy to unveil their peculiar technological applications as photoluminescent emission, photocatalysts, and antibacterial agents.
  • ItemArtigo
    Mechanical Properties, Corrosion Behavior, and In Vitro Cell Studies of the New Ti-25Ta-25Nb-5Sn Alloy
    (2023-03-01) Silva, Kerolene Barboza da [UNESP]; Carobolante, João Pedro Aquiles [UNESP]; Rajan, S. Sudhagara [UNESP]; Júnior, Celso Bortolini [UNESP]; Sabino, Roberta Maia; Seixas, Maurício Rangel [UNESP]; Nakazato, Roberto Zenhei [UNESP]; Popat, Ketul C.; Claro, Ana Paula Rosifini Alves [UNESP]; 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.
  • ItemArtigo
    The Relationship between Photoluminescence Emissions and Photocatalytic Activity of CeO2 Nanocrystals
    (2023-03-13) Moreno, H. [UNESP]; Domingues, G. L. [UNESP]; Assis, M.; Ortega, P. P. [UNESP]; Mastelaro, V.; Ramirez, M. A. [UNESP]; Simões, A. Z. [UNESP]; Universidade Estadual Paulista (UNESP); University Jaume I; Universidade de São Paulo (USP)
    In this work, we focus on understanding the morphology and photocatalytic properties of CeO2 nanocrystals (NCs) synthesized via a microwave-assisted solvothermal method using acetone and ethanol as solvents. Wulff constructions reveal a complete map of available morphologies and a theoretical-experimental match with octahedral nanoparticles obtained through synthesis using ethanol as solvent. NCs synthesized in acetone show a greater contribution of emission peaks in the blue region (∼450 nm), which may be associated with higher Ce3+ concentration, originating shallow-level defects within the CeO2 lattice while for the samples synthesized in ethanol a strong orange-red emission (∼595 nm) suggests that oxygen vacancies may originate from deep-level defects within the optical bandgap region. The superior photocatalytic response of CeO2 synthesized in acetone compared to that of CeO2 synthesized in ethanol may be associated with an increase in long-/short-range disorder within the CeO2 structure, causing the Egap value to decrease, facilitating light absorption. Furthermore, surface (100) stabilization in samples synthesized in ethanol may be related to low photocatalytic activity. Photocatalytic degradation was facilitated by the generation of ·OH and ·O2- radicals as corroborated by the trapping experiment. The mechanism of enhanced photocatalytic activity has been proposed suggesting that samples synthesized in acetone tend to have lower e′─h· pair recombination, which is reflected in their higher photocatalytic response.
  • ItemArtigo
    The Effect of Self-Healing Agent Fraction on CFRP Mechanical Behavior: Statistical Analysis Approach
    (2023-02-01) Chuves, Yuri Pereira [UNESP]; Monticeli, Francisco Maciel; do Nascimento, Allana Azevedo; Barbosa, Ana Paula Cysne; Voorwald, Herman Jacobus Cornelis [UNESP]; Cioffi, Maria Odila Hilário [UNESP]; Universidade Estadual Paulista (UNESP); Technological Institute of Aeronautics (ITA); Federal University of Rio Grande Do Norte
    The self-healing application in structural composites aims to recover component properties, control damage propagation, and increase component life. In this way, this study proposes to characterize and predict the inter-laminar shear behavior of polymer composites (5HS carbon/epoxy) with different fractions of self-healing agent. In addition, this work aims to measure the influence of self-healing content on the mechanical response. The ANOVA evidenced that the healing agent fraction influences on mechanical properties more than the internal dispersion for the same laminate before the healing cycle. Weibull distribution evidenced a linear decrease in shear stresses for higher EMAA (poly(ethylene-co-methacrylic acid)) content, regarding stiffness decrease as a response to ductile thermoplastic behavior. Ineffective healing effects were observed for the translaminar and intra-laminar damage, once most particles were concentrated in inter-laminar sections. However, the healing efficiency reached an average of 62% for shear stress and 106% for toughness behavior, provided by the closing shear cracks, i.e., up to 57% of reduced area related to the initial crack size. The predictive approach before and after healing action in the mechanical behavior provides the appropriate self-healing level to meet the specific project requirements, thus saving time and cost.
  • ItemArtigo
    Magnetoelectric coupling at room temperature in LaTiO3/SrTiO3 heterojunctions
    (2023-06-01) Simoes, A. Z. [UNESP]; Ortega, P. P. [UNESP]; Ramirez, M. A. [UNESP]; Moreno, H. [UNESP]; Aldao, C. M.; Ponce, M. A.; Moura, F.; Universidade Estadual Paulista (UNESP); University of Mar del Plata (UNMdP) and National Research Council (CONICET); National Research Council (CONICET); Federal University of Itajuba
    This work focuses on LaTiO3 (LTO) thin films synthesized by the polymeric precursor method and deposited onto SrTiO3 (STO) substrates via spin coating. The results show interesting coexisting ferromagnetic (Mr≈2.85 emu/g) - ferroelectric (Pr≈18.5 μC/cm2) responses at room temperature. Magnetoelectric coupling can be observed under DC bias magnetic field (14 V/cm.Oe), and its dielectric constant is affected by the coupling between magnetic and electric dipoles at room temperature as well as oxygen octahedra distortion along direction a. Little film-substrate mismatch significantly influences the system dielectric properties. Our results suggest the possibility to induce ferromagnetic/ferroelectric phases in the LTO/STO heterojunctions using an electric/magnetic field, respectively, due to the magnetoelectric coupling. This study also helps comprehend oxygen vacancy dynamics when applying a tensile strain or an external electric field, which is fundamental for actuators, switches, magnetic field sensors, and new types of electronic memory devices.
  • ItemResenha
    Waste Paper as a Valuable Resource: An Overview of Recent Trends in the Polymeric Composites Field
    (2023-01-01) de Oliveira, Daniel Magalhães [UNESP]; de Bomfim, Anne Shayene Campos [UNESP]; Benini, Kelly Cristina Coelho de Carvalho [UNESP]; Cioffi, Maria Odila Hilário [UNESP]; Voorwald, Herman Jacobus Cornelis [UNESP]; Rodrigue, Denis; Universidade Estadual Paulista (UNESP); Université Laval
    This review focuses on polymeric waste-paper composites, including state-of-the-art analysis with quantitative and qualitative discussions. Waste paper is a valuable cellulose-rich material, produced mainly from office paper, newspaper, and paper sludge, which can be recycled and returned to paper production or used in a new life cycle. A systematic literature review found 75 publications on this material over the last 27 years, with half of those published during the last five years. These data represent an increasing trend in the number of publications and citations that have shown an interest in this field. Most of them investigated the physicomechanical properties of composites using different contents of raw waste paper or the treated, modified, and cellulose-extracted types. The results show that polyethylene and polypropylene are the most used matrices, but polylactic acid, a biodegradable/sourced polymer, has the most citations. The scientific relevance of waste-paper composites as a subject includes the increasing trend of the number of publications and citations over the years, as well as the gaps identified by keyword mapping and the qualitative discussion of the papers. Therefore, biopolymers and biobased polymers could be investigated more, as well as novel applications. The environmental impact in terms of stability and degradation should also receive more attention regarding sustainability and life cycle analyses.
  • ItemArtigo
    Simultaneous Treatment of Both Sides of the Polymer with a Conical-Shaped Atmospheric Pressure Plasma Jet
    (2023-01-01) Kodaira, Felipe Vicente de Paula [UNESP]; Leal, Bruno Henrique Silva [UNESP]; Tavares, Thayna Fernandes [UNESP]; Quade, Antje; Hein, Luis Rogerio de Oliveira [UNESP]; Chiappim, William [UNESP]; Kostov, Konstantin Georgiev [UNESP]; Universidade Estadual Paulista (UNESP); Leibniz Institute for Plasma Science and Technology—INP
    A conical-shaped atmospheric pressure plasma jet (CS-APPJ) was developed to overcome a standard limitation of APPJs, which is their small treatment area. The CS-APPJs increase the treatment area but use the same gas flow. In the present work, polypropylene samples were treated by CS-APPJ and characterized by scanning electron microscope (SEM), the contact angle, Fourier-transformed infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was observed that the treatment co-occurs on the face directly in contact with the plasma and on the opposite face (OF) of the samples, i.e., no contact. However, the treatment changed the chemical composition on each side; the OF is rougher than the direct contact face (DCF), probably due to the oxygen groups in excess at the DCF and nitrogen in quantity at the OF. Although simultaneous treatment of both sides of the sample occurs for most atmospheric plasma treatments, this phenomenon is not explored in the literature.
  • ItemArtigo
    The Influence of Equal Channel Angular Pressing on Structure and Mechanical Properties of New β-Ti Alloy Ti–10Mo–8Nb–6Zr
    (2022-12-01) Gunderov, D. V.; Churakova, A. A.; Polyakov, A. V.; Raab, A. G.; Gunderova, S. D.; Lebedev, Yu. A.; Claro, Ana Paula Rosifini Alves [UNESP]; Russian Academy of Sciences; Ufa State Aviation Technical University (USATU); Bashkir State University; Perm National Research Polytechnic University (PNIPU); Universidade Estadual Paulista (UNESP)
    Abstract: This work presents comparative studies of structural and mechanical properties of a new β-Ti alloy Ti–10Mo–8Nb–6Zr exposed to conventional cold rotational forging and equal channel angular pressing (ECAP) at 250°C. The main phase in the initial quenched state after forging and ECAP is the BCC β phase. Broadening of X-ray lines of the β phase and TEM data indicate refinement of structure and increase in concentration of lattice defects after deformational treatment. In the initial state, the alloy has ultimate tensile strength of about 700 MPa, the yield stress of 450 MPa, and relative elongation to failure of ~30%. As a consequence of forging, the ultimate strength and yield stress of Ti–10Mo–8Nb–6Zr alloy increase to 1230 and 950 MPa, and after ECAP, they increase to 1280 and 1270 MPa, respectively; also, the relative elongation decreases to 6%. Significant improvement of strength properties of Ti–10Mo–8Nb–6Zr alloy exposed to ECAP makes it more promising for application in the medical field.
  • ItemArtigo
    Impact of diamond tool wear on the surface finish of lithium silicate glass ceramics machined with the assistance of CAD/CAM systems
    (2023-01-01) Simba, Bruno Galvão [UNESP]; Alves, Manuel Fellipe Rodrigues Pais; Villela, Tales Ferreira; Ribeiro, Marcos Valério [UNESP]; Strecker, Kurt; dos Santos, Claudinei; Universidade Estadual Paulista (UNESP); Universidade do Estado do Rio de Janeiro (UERJ); Universidade Federal Fluminense (UFF); Universidade Federal de São João del-Rei
    In this work, the effect of wear of diamond tools on the surface roughness and its influence on the mechanical properties of dental lithium silicate glass–ceramic milled by a CAD/CAM system was investigated. Cutting tools with distinct tool life, new cutting tool (NCT), mid-life cutting tool (MLCT) corresponding to cumulative 2 h of milling and end-of-life cutting tool (ELCT) corresponding to cumulative 4 h of milling were used for machining commercial lithium metasilicate LM, Li2SiO3, using a Sirona inLab MC X5® milling machine. The different tools were characterized by scanning electron microscopy (SEM). Their microstructure indicated a depletion of diamond particles on the surface, as a function of the accumulated time of use. The lithium metasilicate samples were characterized by their phase composition using X-ray diffraction (XRD) analysis and their microstructure by (SEM). Furthermore, the mechanical properties Vickers hardness, fracture toughness and the elastic parameters were determined. The as-received LM samples presented 44% of Li2SiO3 and 56% amorphous phase. These LM samples exhibited a Vickers hardness of 6.1 ± 0.3 GPa, a fracture toughness of 1.3 ± 0.2 MPa m1/2, a modulus of elasticity of 82.3 GPa and a Poisson’s ratio of 0.16. The surface roughness of the machined LM samples was evaluated using a roughness meter. The profilometry measurements of the machined LM samples indicate a slight increase in the roughness parameter Ra with increasing wear of the cutting tools, i.e., using NCT, MLCT or ELCT tools, in addition to a considerable increase in the total height of the Rt profile from 11 to 17 µm. The formation of small microcracks during machining may nucleate new flaws in the material, if the critical initial crack size is exceeded. Aspects related to the performance of heat treatments for crystallization of lithium disilicate, Li2Si2O5, and its implications on the microstructure, softening of the residual amorphous phase and its surface roughness are discussed.
  • ItemArtigo
    Processing and Characterization of a New Quaternary Alloy Ti10Mo8Nb6Zr for Potential Biomedical Applications
    (2022-12-01) Carobolante, João Pedro Aquiles [UNESP]; Pereira Júnior, Adelvam [UNESP]; Bortolini Junior, Celso [UNESP]; Barboza da Silva, Kerolene [UNESP]; Sabino, Roberta Maia; Popat, Ketul C.; Claro, Ana Paula Rosifini Alves [UNESP]; Universidade Estadual Paulista (UNESP); Colorado State University
    The study of new metallic biomaterials for application in bone tissue repair has improved due to the increase in life expectancy and the aging of the world population. Titanium alloys are one of the main groups of biomaterials for these applications, and beta-type titanium alloys are more suitable for long-term bone implants. The objective of this work was to process and characterize a new Ti10Mo8Nb6Zr beta alloy. Alloy processing involves arc melting, heat treatment, and cold forging. The characterization techniques used in this study were X-ray fluorescence spectroscopy, X-ray diffraction, differential scanning calorimetry, optical microscopy, microhardness measurements, and pulse excitation technique. In vitro studies using adipose-derived stem cells (ADSC) were performed to evaluate the cytotoxicity and cell viability after 1, 4, and 7 days. The results showed that the main phase during the processing route was the beta phase. At the end of processing, the alloy showed beta phase, equiaxed grains with an average size of 228.7 µm, and low Young’s modulus (83 GPa). In vitro studies revealed non-cytotoxicity and superior cell viability compared to CP Ti. The addition of zirconium led to a decrease in the beta-transus temperature and Young’s modulus and improved the biocompatibility of the alloy. Therefore, the Ti10Mo8Nb6Zr alloy is a promising candidate for application in the biomedical field.
  • ItemArtigo
    Recent advances in the use of Polyamide-based materials for the automotive industry
    (2022-01-01) Kondo, Marcel Yuzo [UNESP]; Montagna, Larissa Stieven; de Melo Morgado, Guilherme Ferreira; de Castilho, André Luiz Guimarães [UNESP]; dos Santos Batista, Larissa Anne Pereira; Botelho, Edson Cocchieri [UNESP]; Costa, Michelle Leali [UNESP]; Passador, Fabio Roberto; Rezende, Mirabel Cerqueira; Ribeiro, Marcos Valério [UNESP]; Universidade Estadual Paulista (UNESP); Universidade Federal de São Paulo (UNIFESP); Instituto de Pesquisas Tecnológicas – IPT
    Polyamide (PA) is a well-known and researched thermoplastic due to its excellent mechanical and physical properties, making it developed in the automotive sector, suitable for lighter vehicles, and, consequently, lower fuel consumption. This review manuscript presents the applications of PA-based materials in the manufacture of vehicle parts, with a description of their processing, a discussion about their thermal properties and the crystallization of polymer structure, the challenges of machining PA-based composite materials, and the feasibility of recyclability. This work aims to revise literature about the use of polyamide 6 (PA6), polyamide 66 (PA66), and polyamide 12 (PA12) and their composites reinforced with fiberglass (FG) and carbon fiber (CF) focused on the potential that these materials have as alternative materials for the automotive industry.
  • ItemTrabalho apresentado em evento
    Structure and micro-hardness of titanium alloy Ti10Mo8Nb6Zr after high pressure torsion
    (2022-09-14) Gunderov, Dmitry; Churakova, Anna; Kiseleva, Svetlana; Gunderova, Sophia; Pedro, Joao [UNESP]; Claro, Ana Paula Rosifini Alves [UNESP]; Ufa Federal Research Center RAS; Ufa State Aviation Technical University; Universidade Estadual Paulista (UNESP)
    The team of the Sao Paolo University (Brazil) developed a new β-Ti alloy Ti10Mo8Nb6Zr, which is perspective as material for medical implants. The structure and micro-hardness of titanium alloy Ti10Mo8Nb6Zr after high pressure torsion were studied. The XRD analysis showed that β-phase was the main phase of Ti10Mo8Nb6Zr alloy in the initial state. After high pressure torsion, β-phase remains the main one. There is also an additional α-phase, but its amount is low (below 10%). The half-width of a primary X-ray line of β-phase is greatly increased after HPT. This testifies to an increased density of dislocations and refinement of grains during HPT. According to TEM, after HPT a nanosized structure is formed. The TEM studies show that the alloy after HPT n=0.5 and n=5 contains both sub-grains with low-angle sub-boundaries and grains with high-angle boundaries and a high density of dislocations. Even after HPT with a relatively low n (n=0.5) a rather fine structure is formed with a size of grains/sub-grains of about 200-500 nm. After HPT with n = 5, the microstructure of Ti10Mo8Nb6Zr alloy is additionally refined, but the size of grains/sub-grains is about 200-300 nm. HPT with a low number of revolutions n=0.5 leads to a substantial growth of HV from 326 to 400. Further increase in the number of revolutions leads to additional growth of microhardness. The HV increment after HPT of this alloy (about 20%) is much lower than that after HPT of titanium and α-Ti alloys.
  • ItemArtigo
    Dry machining of nodular cast iron using a YAG-reinforced alumina ceramic cutting tool
    (2022-11-01) de Sousa, Leopoldo Ferreira; Simba, Bruno Galvão [UNESP]; de Souza, José Vitor Candido [UNESP]; Ribeiro, Marcos Valério [UNESP]; de Macedo Silva, Olivério Moreira; dos Santos, Claudinei; UNIFOA-MEMAT; Universidade Estadual Paulista (UNESP); DCTA-IAE-AMR; Universidade do Estado do Rio de Janeiro (UERJ)
    In this work, an alumina-yttrium aluminum garnet (Al2O3-YAG) cutting tool was developed and characterized aiming application in dry machining of nodular (spheroidal) cast iron. Ceramic powders containing 85 wt.% Al2O3 and 15 wt.% Y3Al5O12(YAG) were homogenized, compacted, and sintered at 1600 °C for 2 h at a heating rate of 5 °C/min. The sintered ceramic presented relative density of 98.3 ± 0.2%. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed α-Al2O3 and YAG as crystal phases, both with equiaxed grains with average sizes of 1–4 μm (Al2O3 phase) and 0.7–1 μm (YAG phase). In addition, this ceramic composite presented Vickers hardness and fracture toughness of 15.2 ± 0.2 GPa and 4.6 ± 0.3 MPa.m1/2, respectively. The dry machining performance of the Al2O3-YAG cutting tool was compared with that of a commercial cemented carbide cutting tool using cutting speed (VC) of 200 and 500 m/min, feed rate (f) of 0.25 and 0.10 mm/rev, and axial depth of cut (ap) of 0.60 mm. The results showed that the best setting for the cemented carbide cutting tool was obtained at VC = 200 m/min and f = 0.25 mm/rev, which produced the best machinability with average surface roughness (Ra) of 3.516 μm, cutting length (LC) of 6000 m, and maximum flank wear (VBmax) of 0.58 mm. For the Al2O3-YAG cutting tool, the best setting was achieved at VC = 500 m/min and f = 0.10 mm/rev, which produced Ra = 0.848 μm, LC = 12,293 m, and VBmax = 0.54 mm.
  • ItemArtigo
    Studies of curing cycle of carbon fiber/epoxy resins (8552® and M21®) prepregs based on thermal and rheological analyses
    (2022-01-01) Silva, Sheila Marques [UNESP]; Silva, Carolina Paiva Nascimento; de Carvalho Silva, Thiago; Rezende, Mirabel Cerqueira; Botelho, Edson Cocchieri [UNESP]; Costa, Michelle Leali [UNESP]; Universidade Estadual Paulista (UNESP); Universidade de São Paulo (USP); LEL/IPT; Federal Center for Technological Education Celso Suckow da Fonseca
    Thermal and rheological characterizations were performed on prepreg produced with two different commercial epoxy resins - M21® and 8552® - aiming to study and optimize the curing cycle of structural components used in aerospace industry. Characterizations were performed by differential scanning calorimetry (DSC), rheology and dynamic mechanical analysis techniques were assessed and the results were correlated and supported by Fourier Transform Infrared spectroscopy. Additionally, to heating rates suggested by the material supplier, DSC analysis allowed to evaluate further heating rates: 2, 5, 10, 15 and 20 °C/min. Materials presented the n fractional order kinetic of cure and have in its formulation the presence of thermoplastics, in addition to epoxy and amine. Results confirmed that the best heating rates for processing both materials are the lower ones, as they result in a better control of the reactions between chemical compounds involved and the physical changes that are part of curing process stages. Results have analytically confirmed the suggested proposal for curing cycle from supplier is the best choice for materials involved.