INSTITUTO DE PESQUISAS ENERGÉTICAS E NUCLEARES
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Navegação Periódicos - Artigos por Agências de fomento "Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)"

Navegação Periódicos - Artigos por Agências de fomento "Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)"

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  • IPEN-DOC 23152

    BERECZKI, ALLAN ; WETTER, NIKLAUS U. . 100W continuous linearly polarized, high beam quality output from standard side-pumped Nd:YAG laser modules. Optics and Laser Technology, v. 96, p. 271-275, 2017. DOI: 10.1016/j.optlastec.2017.05.020

    Abstract: Dynamically stable operation with joined stability zones of a linearly polarized resonator is shown for a laser containing two diode side-pumped Nd:YAG rods. The unpolarized resonator generated 115W of output. When polarized by a Brewster plate, it reached 100.5W of output power at a beam quality M2 < 2. Best measured beam quality was of 1.1 and 1.3 in the x and y directions respectively, with 76W of 95% polarized output. The output power achieved is, to our knowledge, the highest reported for continuous polarized, fundamental-mode lasers using standard side-pumped Nd:YAG modules.

    Palavras-Chave: neodymium lasers; lasers; resonators; solid state lasers; temperature dependence; diode-pumped solid state lasers; beams; quality factor

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  • IPEN-DOC 29785

    DIPOLD, JESSICA ; BORDON, CAMILA D.S.; MAGALHAES, EVELLYN S.; KASSAB, LUCIANA R.P.; JIMENEZ-VILLAR, ERNESTO; WETTER, NIKLAUS U. . 1337 nm emission of a Nd3+-doped TZA glass random laser. Nanomaterials, v. 13, n. 13, p. 1-11, 2023. DOI: 10.3390/nano13131972

    Abstract: Random lasers have been studied using many materials, but only a couple have used glass matrices. Here, we present a study of zinc tellurite and aluminum oxide doped with different percentages of neodymium oxide (4 wt.%, 8 wt.%, and 16 wt.%) and demonstrate for the first time random laser action at 1337 nm. Laser emission was verified and the laser pulse’s rise time and input–output power slope were obtained. A cavity composed of the sample’s pump surface and an effective mirror formed by a second, parallel layer at the gain-loss boundary was probably the main lasing mechanism of this random laser system. The reason for the absence of emission at 1064 nm is thought to be a measured temperature rise in the samples’ active volume.

    Palavras-Chave: doped materials; laser materials; neodymium lasers; scattering; glass; tellurium oxides

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  • IPEN-DOC 28520

    LA FAUCI, L.; SPATAFORA, A.; CAPPUZZELLO, F.; AGODI, C.; CARBONE, D.; CAVALLARO, M.; LUBIAN, J.; ACOSTA, L.; AMADOR-VALENZUELA, P.; BORELLO-LEWIN, T.; BRISCHETTO, G.A.; CALABRESE, S.; CALVO, D.; CAPIROSSI, V.; CHAVEZ LOMELI, E.R.; CIRALDO, I.; CUTULI, M.; DELAUNAY, F.; DJAPO, H.; EKE, C.; FINOCCHIARO, P.; FIRAT, S.; FISICHELLA, M.; FOTI, A.; GUAZZELLI, M.A.; HACISALIHOGLU, A.; IAZZI, F.; LINARES, R.; MA, J.; MEDINA, N.H.; MORALLES, M. ; OLIVEIRA, J.R.B.; PAKOU, A.; PANDOLA, L.; PETRASCU, H.; PINNA, F.; RIES, P.C.; RUSSO, G.; SGOUROS, O.; SOLAKCI, S.O.; SOUKERAS, V.; SOULIOTIS, G.; TORRESI, D.; TUDISCO, S.; WANG, J.; YANG, Y.; YILDIRIN, A.; ZAGATTO, V.A.B.. 18O+76Se elastic and inelastic scattering at 275 MeV. Physical Review C, v. 104, n. 5, p. 054610-1 - 054610-9, 2021. DOI: 10.1103/PhysRevC.104.054610

    Abstract: Background: An accurate description of the initial and final state interactions in the 18O+76Se collision is demanded by the NUMEN project. The study of single and double charge exchange nuclear reactions is the main purpose for NUMEN, since these can be used as tools to provide experimentally driven information about nuclear matrix elements of interest in the context of neutrinoless double-β decay. To date, the details of the optical potentials and nuclear response to isospin operators for many of the projectile-target systems proposed for the NUMEN double charge exchange studies are poorly known. The 18O+76Se case, here under study, is particularly relevant due to its connection with the 76Ge neutrinoless double-β decay. Purpose: In this work the authors want to characterize the initial-state interaction for the 18O+76Se reactions at 275 MeV incident energy determining the optical potential and evaluating the effect of couplings with the inelastic scattering on the elastic channel. Methods: The angular distributions of differential cross section were measured in the angular region between 4◦ and 22◦ in the center-of-mass reference frame. The cross sections were compared with theoretical calculations, that adopt different optical potentials. Coupling effects on the elastic channel were determined into the coupled channels formalism. Results: The excitation energy spectrum of the colliding nuclei and the cross section angular distributions were measured with satisfactory energy resolution. The elastic scattering cross section is not well reproduced in the full angular range explored when the optical model approach is adopted. A good agreement is found using coupled channel calculations. The initial state interaction for the 18O+76Se nuclear reactions at 275 MeV is determined. Conclusions: Coupled channels effects are crucial to obtain a good description of the measured elastic and inelastic channels cross sections, even at large transferred momenta where the optical model approach fails in reproducing the experimental data. The role of channel coupling could be relevant also in the analysis of other open reaction channels in the same collision and should be accounted for in double charge exchange analyses as well.

    Palavras-Chave: oxygen 18; selenium 76; elastic scattering; inelastic scattering; nuclear reactions

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  • IPEN-DOC 28521

    CALABRESE, S.; CAVALLARO, M.; CARBONE, D.; CAPPUZZELLO, F.; AGODI, C.; BURRELLO, S.; DE GREGORIO, G.; FERREIRA, J.L.; GARGANO, A.; SGOUROS, O.; ACOSTA, L.; AMADOR-VALENZUELA, P.; BELLONE, J.I.; BORELLO-LEWIN, T.; BRISCHETTO, G.A.; CALVO, D.; CAPIROSSI, V.; CHAVEZ LOMELI, E.R.; CIRALDO, I.; COLONNA, M.; DELAUNAY, F.; DJAPO, H.; EKE, C.; FINOCCHIARO, P.; FIRAT, S.; FISICHELLA, M.; FOTI, A.; GUAZZELLI, M.A.; HACISALIHOGLU, A.; IAZZI, F.; LA FAUCI, L.; LAY, J.A.; LINARES, R.; LUBIAN, J.; MEDINA, N.H.; MORALLES, M. ; OLIVEIRA, J.R.B.; PAKOU, A.; PANDOLA, L.; PETRASCU, H.; PINNA, F.; RUSSO, G.; SOLAKCI, S.O.; SOUKERAS, V.; SOULIOTIS, G.; SPATAFORA, A.; TORRESI, D.; TUDISCO, S.; YILDIRIN, A.; ZAGATTO, V.A.B.. 18O-induced single-nucleon transfer reactions on 40Ca at 15.3A MeV within a multichannel analysis. Physical Review C, v. 104, n. 6, p. 064609-1 - 064609-12, 2021. DOI: 10.1103/PhysRevC.104.064609

    Abstract: Background: Nucleon transfer reactions are selective tools for nuclear physics investigations. The theoretical and computational limits affecting in the past their data analysis could be nowadays surmounted thanks to the advent of methods with refined approximations and constraints, even when heavy-ion collisions are considered. Purpose: Modern microscopic calculations of heavy-ion-induced transfer reactions combined with precise experimental data offer the chance for accurately testing different reaction models as well as the nuclear structure description of the involved nuclear states. Method: Single proton and neutron transfer reactions were measured with theMAGNEX magnetic spectrometer for the 18O+40Ca system at 15.3A MeV. Excitation energy spectra and angular differential cross section distributions were extracted. The experimental results are compared with theoretical calculations performed in distorted wave and coupled channel Born approximation. The use of a coupled channel equivalent polarization potential to effectively describe the coupling effects affecting the initial state interaction is also considered. Spectroscopic amplitudes derived from a large-scale shell model with appropriate interactions adapted for the involved nuclei are employed. Results: Our theoretical calculations are in good agreement with experimental data, without the need for any scaling factor, validating the adopted reaction and nuclear structure parameters. Moreover, under the present experimental conditions, a weak dependence of the obtained results on the choice of the reaction models was observed. Conclusions: The good agreement between experimental and theoretical results validates the reliability of the parameter sets entering the calculations. They are extracted from or tested in complementary analyses of other reaction channels under the same experimental conditions. Such a multichannel approach represents the best option to pursue a solid, comprehensive, and model-independent description of the single-nucleon transfer reactions. The successful description of the present one-nucleon transfer data is also propaedeutic to the accurate assessment, under the same theoretical description, of higher-order transfer processes, like the sequential nucleon transfer mechanisms which are in competition with the direct charge exchange reactions.

    Palavras-Chave: nucleon reactions; calcium 40; oxygen 18; calculation methods; born approximation; distorted wave theory; magnets

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  • IPEN-DOC 24704

    ARAGAO, LUIZ E.O.C.; ANDERSON, LIANA O.; FONSECA, MARISA G.; ROSAN, THAIS M.; VEDOVATO, LAURA B.; WAGNER, FABIEN H.; SILVA, CAMILA V.J.; SILVA JUNIOR, CELSO H.L.; ARAI, EGIDIO; AGUIAR, ANA P.; BARLOW, JOS; BERENGUER, ERIKA; DEETER, MERRITT N.; DOMINGUES, LUCAS G. ; GATTI, LUCIANA ; GLOOR, MANUEL; MALHI, YADVINDER; MARENGO, JOSE A.; MILLER, JOHN B.; PHILLIPS, OLIVER L.; SAATCHI, SASSAN. 21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions. Nature Communications, v. 9, n. 536, 2018. DOI: 10.1038/s41467-017-02771-y

    Abstract: Tropical carbon emissions are largely derived from direct forest clearing processes. Yet, emissions from drought-induced forest fires are, usually, not included in national-level carbon emission inventories. Here we examine Brazilian Amazon drought impacts on fire incidence and associated forest fire carbon emissions over the period 2003-2015. We show that despite a 76% decline in deforestation rates over the past 13 years, fire incidence increased by 36% during the 2015 drought compared to the preceding 12 years. The 2015 drought had the largest ever ratio of active fire counts to deforestation, with active fires occurring over an area of 799,293 km(2). Gross emissions from forest fires (989 +/- 504 Tg CO2 year(-1)) alone are more than half as great as those from old-growth forest deforestation during drought years. We conclude that carbon emission inventories intended for accounting and developing policies need to take account of substantial forest fire emissions not associated to the deforestation process.

    Palavras-Chave: carbon dioxide; deforestation; forests; monitoring; greenhouse gases; tropical regions; climates; droughts; fires; amazon river; brazil

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  • IPEN-DOC 19230

    VIANA, R.S.; AGASTHYA, G.A.; YORIYAZ, H. ; KAPADIA, A.J.. 3D element imaging using NSECT for the detection of renal cancer: a simulation study in MCNP. Physics in Medicine and Biology, v. 58, n. 17, p. 5867-5883, 2013.

    Palavras-Chave: kidneys; carcinomas; computerized tomography; three-dimensional calculations; neutron emission; stimulated emission; simulation; m codes

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  • IPEN-DOC 26646

    SILVA, J.P.L. ; TEIXEIRA, L.F. ; BELLINI, M.H. . [6]-Gingerol decreases clonogenicity and radioresistance of human prostate cancer cells. Clinical Oncology and Research, v. 2, n. 5, p. 1-3, 2019. DOI: 10.31487/j.COR.2019.05.07

    Abstract: The phenolic compound [6]-Gingerol, isolated from Zingiber officinale, has been demonstrated to have antitumor activity for different types of malignant tumours. Prostate cancer is the most common malignancy among males worldwide, being the second leading cause of cancer death in men. In the present study, we investigated the antitumor action of [6]-Gingerol on a human prostate cancer cell line (LNCaP). Our data shows that [6]-Gingerol treatment induced a dose-dependent decrease in the cell viability. Compared with the vehicle control, the cell viabilities were 79.90 ± 3.56% and 53.06 ± 7.82% when the LNCaP cells were exposed to 150 μg/mL and 300 μg/mL of [6]-Gingerol, respectively. The treatment of LNCaP with 300 μM of [6]-Gingerol led to a significant reduction (~25%) on the clonogenic survival of these cells. Furthermore, [6]-gingerol acted as a radiosensitizer for LNCaP cells. The pretreatment of these cells with [6]-Gingerol significantly enhanced the killing effects of ionizing radiation with a dose enhancement ratio of 1.25. Our results demonstrate the anti-tumour activities of [6]-Gingerol. Further studies are needed to elucidate the mechanisms involved.

    Palavras-Chave: prostate; neoplasms; radiosensitivity effects; radiosensitizers; radiosensitivity; clone cells; cloning; viability; medicinal plants; spices; radiotherapy; tumor cells

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  • IPEN-DOC 24719

    CARVALHO, SABRINA G.M. ; MUCCILLO, ELIANA N.S. ; MUCCILLO, REGINALDO . AC electric field assisted pressureless sintering zirconia: 3mol% yttria solid electrolyte. Physica Status Solidi A: applications and materials science, v. 215, n. 6, p. 1700647-1 - 1700647-5, 2018. DOI: 10.1002/pssa.201700647

    Abstract: 3mol% yttria ionic conductors are sintered by applying AC electric fields with frequencies in the 0.5-1.0kHz range at 1100 degrees C. The sintering experiments are conducted in pressed pellets positioned between platinum electrodes inside a dilatometer furnace. The dilatometer is modified in order to allow for the simultaneous monitoring of thickness shrinkage, electric voltage, and current across the pellet. The results show that the higher the frequency of the electric field, the higher the attained shrinkage and the apparent density of the pellets. Increasing the frequency of the applied electric field leads to an increase in the Joule heating promoted by the electric current pulse through the polycrystalline ceramic sample. A higher frequency therefore leads to higher amount of thermal energy delivered to the sample, favoring enhanced densification. The ionic resistivity decreases in pellets sintered with increasing frequency of the applied electric field. We suggest that Joule heating favors pore elimination and the removal of chemical species at the space charge region, inhibiting the blocking of oxide ions at the interfaces.

    Palavras-Chave: ac systems; ceramics; dilatometry; electric fields; electric impedance; hz range; ionic conductivity; joule heating; pellets; polycrystals; porosity; shrinkage; sintered materials; sintering; density; solid electrolytes; temperature range 1000-4000 k; thickness; yttrium oxides; zirconium oxides

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  • IPEN-DOC 18371

    AZEVEDO, JULIANA de S.; HORTELLANI, MARCOS A. ; SARKIS, JORGE E.S. . Accumulation and distribution of metals in the tissues of two catfish species from Cananéia and Santos - São Vicente Estuaries. Brazilian Journal of Oceanography, v. 60, n. 4, p. 463-472, 2012.

    Palavras-Chave: brazil; coastal waters; estuaries; contamination; metals; copper; zinc; cadmium; lead; fishes; animal tissues; biological accumulation

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  • IPEN-DOC 29108

    SANTOS, NATHALIA V. dos; VIEIRA, CAROLINA L.Z.; SALDIVA, PAULO H.N.; DE ANDRE, CARMEN D.S.; MAZZILLI, BARBARA P. ; ANDRADE, MARIA de F.; SAUEIA, CATIA H. ; SAIKI, MITIKO ; VERAS, MARIANA M.; KOUTRAKIS, PETROS. Accumulation of trace element content in the lungs of São Paulo city residents and its correlation to lifetime exposure to air pollution. Scientific Reports, v. 12, p. 1-7, 2022. DOI: 10.1038/s41598-022-15048-2

    Abstract: Heavy metals are natural and essential elements of the environment and living beings, produced from natural (e.g. volcanic activity and cosmic ray-induced spallation) and anthropogenic processes (e.g. industrial and fossil fuel combustion). High-concentrations of heavy metals and radionuclides are also originated from anthropogenic activities in urban and industrial areas. In this preliminary study, we analyzed the levels of heavy metals and Polonium-210 (210Po) in lung tissues in autopsies from residents of the city of Sao Paulo, SP, Brazil. In order to identify the link among sources of the heavy metals in lungs, factor analysis was performed. Of the first four factors, which explain 66% of the total variability, three were associated with vehicular sources. The fitting of a regression model with 210Po as the response variable and with the four factors as explanatory variables, controlling for age, sex and tobacco, showed a significant association between the concentration of polonium and the first factor that is generated by catalysts and brakes (coefficient = 0.90, standard error = 0.33, p = 0.016). Our findings suggest an association between traffic-related trace metals and 210Po in lung autopsies.

    Palavras-Chave: environmental impacts; chemical wastes; brazil; public health; elements; air pollution control; heavy metals; respiratory system

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  • IPEN-DOC 26619

    NANDENHA, J. ; NAGAHAMA, I.H.F. ; YAMASHITA, J.Y. ; FONTES, E.H. ; AYOUB, J.M.S. ; SOUZA, R.F.B. de ; FONSECA, F.C. ; NETO, A.O. . Activation of methane on PdZn/C electrocatalysts in an acidic electrolyte at low temperatures. International Journal of Electrochemical Science, v. 14, n. 12, p. 10819-10834, 2019. DOI: 10.20964/2019.12.76

    Abstract: PdZn/C electrocatalysts were prepared by sodium borohydride utilized as reducing agent for activation methane in an acidic medium at room temperature and in a proton exchange membrane fuel cell (PEMFC) at 80°C. The materials prepared were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The diffractograms of the PdZn/C electrocatalysts showed only peaks associated with Pd face-centered cubic (fcc) structure. Cyclic voltammograms (CV) of all electrocatalysts after adsorption of methane shown an increment in current during the anodic scan, this effect was more pronounced for Pd(70)Zn(30)/C. In situ ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared) experiments was not observed the formation of intermediates adsorbed for PdZn/C electrocatalysts, this behavior indicated that the methane oxidation occurs by parallel mechanisms. Polarization curves at 80°C in PEMFC show that Pd(90)Zn(10)/C has superior performance over the other electrocatalysts in methane oxidation.

    Palavras-Chave: methane; palladium; zinc; electrocatalysts; sodium compounds; borohydrides; reduction; oxidation; polarization; electrolytes; diagrams

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  • IPEN-DOC 26397

    QUEIROZ, CARLA M.S. ; MACHADO, ARTHUR P. ; PAIVA, ANA R.N. ; ANTONIASSI, RODOLFO M. ; VAZ, JORGE M. ; SPINACE, ESTEVAM V. . Active Pt/CeO2 catalysts prepared by an alcohol‑reduction process for low‑temperature CO‑PROX reaction. Materials for Renewable and Sustainable Energy, v. 8, n. 3, p. 1-8, 2019. DOI: 10.1007/s40243-019-0155-y

    Abstract: Pt/CeO2 catalysts were prepared with 0.5 and 1 wt% of Pt loadings by an alcohol-reduction process using a solution of ethylene glycol and water as a reducing agent and solvent. The obtained catalysts were characterized by energy-dispersive X-ray spectroscopy, X-ray diffraction, and transmission electron microscopy. Transmission electron micrographs showed Pt nanoparticles with average sizes of 2.2 and 2.4 nm for Pt content of 0.5 and 1 wt%, respectively. The preferential oxidation of carbon monoxide in hydrogen-rich stream (CO-PROX reaction) was studied in the temperature range of 25–150 °C. Pt/CeO2 catalysts showed maximum CO conversions in the range of 80–98% and CO2 selectivity in the range of 50–70% at 50 °C.

    Palavras-Chave: catalysts; cerium; cerium oxides; platinum; alcohols; reduction; hydrogen; carbon monoxide; selective catalytic reduction

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  • IPEN-DOC 28154

    LIMA, F.S. ; FONTES, E.H. ; NANDENHA, J. ; SOUZA, R.F.B. de ; NETO, A.O. . Addition of bismuth to Pt and Pd for electric power generation with selective cogeneration of acetate from ethanol in a fuel cell type reactor. Journal of Fuel Chemistry and Technology, v. 49, n. 10, p. 1540-1548, 2021. DOI: 10.1016/S1872-5813(21)60141-X

    Abstract: Pt/C, PtBi(95:5)/C, Pd/C, and PdBi(95:5)/C were synthesized by the sodium borohydride reducing method to produce metal nanoparticles with advanced electronic properties to enhance the ethanol oxidation reaction (EOR) mechanism. The Transmission Electron Microscopy (TEM) images and X-ray photoelectron spectroscopy (XPS) showed that a small Bi content does not affect the nanoparticle size PdBi/C; in contrast, it does affect the PtBi ones. The X-ray diffraction analysis revealed a lattice parameter modification by Bi dope in Pt crystalline structure. Furthermore, the ATR-FTIR results indicated the suppression of carbonate formation and increment in acetate production. The results of polarization and power density curves on DEFC, the material PtBi/C presented the more high power density, almost six times bigger than Pt/C. PtBi/C also has the highest current density (44 mW/cm2) and the lowest onset potential (−0.6 V) in linear sweep voltammetry experiments. It also has the highest final current density in current-time experiments. Hence, PtBi/C is a very promising electrocatalyst for DEFC.

    Palavras-Chave: direct ethanol fuel cells; bismuth; ethanol; oxidation

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  • IPEN-DOC 26398

    PAPAI, RODRIGO; FREITAS, MILLENA A.S. de; FONSECA, KARINA T. da; ALMEIDA, GILMAR A. de ; SILVEIRA, JOÃO R.F. da; SILVA, ANDRE L.N. da; FERREIRA NETO, JOÃO B.; SANTOS, CELIA A.L. dos; LANDGRAF, FERNANDO J.G.; LUZ, MACIEL S.. Additivity of optical emissions applied to neodymium and praseodymium quantification in metallic didymium and (Nd,Pr)-Fe-B alloy samples by low-resolution atomic emission spectrometry: an evaluation of the mathematical approach used to solve spectral interferences. Analytica Chimica Acta, v. 1085, p. 21-28, 2019. DOI: 10.1016/j.aca.2019.07.049

    Abstract: In this work, the effectiveness of a mathematical approach to solve the spectral interferences involved in the optical emission of two chemical species (neodymium and praseodymium) when using monochromators with low-resolution in atomic spectrometry is evaluated. Although recent technological advances have promoted spectrometers equipped with high-resolution monochromators, which have a great instrumental capability in the separation of nearby lines and consequently avoid spectral interferences, many laboratories still have old spectrometers installed with insufficient resolution to overcome such interferences. In order to evaluate a mathematical approach based on Lambert-Beer's Law, the optical emissions of neodymium and praseodymium were monitored on a low-resolution (200 pm) flame atomic emission spectrometry (F-AES). These two elements were strategically chosen as an application model because they exhibit similar physicochemical properties, joint occurrence in nature and because they are increasingly used in the manufacture of super-magnets, a material increasingly required by the high technology industry. The effectiveness of the mathematical approach was evaluated in three different ways: (i) by recovery of the analytes in synthetic mixtures containing known quantities of the species; (ii) by spike and recovery trials on a representative blend of dissolved samples and (iii) by comparing the results obtained with another analytical method: Inductively coupled plasma optical emission spectrometry (ICP-OES) with a higher spectral resolution. The results indicate the effectiveness of this simple mathematical approach, allow the “survival” of instruments equipped with low-resolution monochromators and demonstrate the applicability of this approach to spectral correction. In addition, this work contributes an analytical method for the quantification of neodymium and praseodymium in metallic alloy samples involved in the production of super-magnets, aiding in the strict quality control of these materials.

    Palavras-Chave: additives; emission; absorption spectroscopy; neodymium; praseodymium; spectra; interference; atoms

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  • IPEN-DOC 12314

    BOTTA, SERGIO B.; ANA, PATRICIA A. da; ZEZELL, DENISE M. ; POWERS, JOHN M.; MATOS, ADRIANA B.. Adhesion after erbium, chromium: yttrium-scandium-gallium-garnet laser aplication at three different irradiation conditions. Lasers in Medical Science, v. 24, n. 1, p. 67-73, 2009.

    Palavras-Chave: erbium; chromium; yttrium; scandium; gallium; garnets; laser radiation; teeth; caries; tissues; cooling; water; bonding

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  • IPEN-DOC 24415

    SANTOS, SILAS C. ; RODRIGUES, ORLANDO ; CAMPOS, LETICIA L. . Advances in colloidal processing of rare earth particles. Current Smart Materials, v. 3, p. 1-18, 2018. DOI: 10.2174/2405465802666171012143956

    Abstract: Abstract: Background: New insights into materials science provide development of smart nano/micro structured materials for advanced applications. Rare earth includes a set of chemical elements (from La to Lu, including Sc and Y) with unique properties, the use of which is evidenced by luminescence applications. Colloidal processing offers great possibilities to obtain smart materials by controlling inter-particle forces, as well as their evolution during ceramic processing. The present article reports a review on colloidal processing with emphasis on rare earth powders. A general view about rare earths properties, including scientific investigations and applications are also presented. Methods: General view on rare earth sources, classification, properties, studies, and applications are reported. Besides, a review on colloidal processing covering particle characteristics, inter- particle forces, dispersion methods, rheology of suspensions, shaping process, drying-sintering stage, and microstructure formation is reported. Results: Yttria is the most used rare earth oxide in phosphors applications (70%). Synthesis routes imply on powder properties. Particle characteristics as size, shape, density, and surface area are important parameters for colloidal processing. The control of inter- particle forces by zeta potential evaluation and using dispersion methods provide conditions to prepare stable suspensions. Consolidation of colloidal particles into a desired shape depends on both viscosity and rheological behavior of suspensions. Drying-sintering conditions are effective on microstructure formation and component characteristics. Bio-prototyping is a low cost method, which provides components with complex shape and cellular architecture. Conclusion: Rare earths exhibit remarkable properties, being applied in diverse technological end-use. Colloidal processing provides opportunities to form smart materials since synthesis of colloids until development of complex ceramic components by shaping methods and thermal treatment. Even though colloidal processing is quite mature, investigations on rare earths involving inter- particle forces, shaping, drying-sintering stage, and microstructure formation are very scarce.

    Palavras-Chave: rare earths; processing; dispersions; particles; rheology; sintering; colloids

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  • IPEN-DOC 27790

    DRESCH, MAURO A. ; MATOS, BRUNO R. ; GODOI, DENIS R.M.; LINARDI, MARCELO ; FONSECA, FABIO C. ; VILLULLAS, HEBE de las M.; SANTIAGO, ELISABETE I. . Advancing direct ethanol fuel cell operation at intermediate temperature by combining Nafion-hybrid electrolyte and well-alloyed PtSn/C electrocatalyst. International Journal of Hydrogen Energy, v. 46, n. 24, p. 13252-13264, 2021. DOI: 10.1016/j.ijhydene.2021.01.123

    Abstract: The advancement of direct ethanol fuel cell (DEFC) represents a real challenge to electrochemical science because ethanol changes significantly the triple phase boundary properties such as the redox reactions and the proton transport. Ethanol molecules promote poor fuel cell performance due to their slow oxidation rate, reduction of the proton transport due to high affinity of ethanol by the membrane, and due to mixed potential when the ethanol molecules reach the cathode by crossover. DEFC performance has been improved by advances in the membranes, e.g., low ethanol crossover polymer composites, or electrode materials, e.g., binary/ternary catalysts. Herein, high temperature (130 °C) DEFC tests were systematically investigated by using optimized electrode and electrolyte materials: Nafion-SiO2 hybrid electrolyte and well-alloyed PtSn/C electrocatalyst. By optimizing both the electrode and the electrolyte in conjunction, DEFCs operating at 130 °C exhibited a threefold increase on performance as compared to standard commercially available materials.

    Palavras-Chave: direct ethanol fuel cells; electrocatalysts; hybridization; electrolytes; nanocomposites

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  • IPEN-DOC 27786

    RAMOS, LUIZ D.; MANTOVANI, MARIANA C. ; SARTORI, ADRIANO; DUTRA, FERNANDO; STEVANI, CASSIUS V.; BECHARA, ETELVINO J.H.. Aerobic co-oxidation of hemoglobin and aminoacetone, a putative source of methylglyoxal. Free Radical Biology and Medicine, v. 166, p. 178-186, 2021. DOI: 10.1016/j.freeradbiomed.2021.02.023

    Abstract: Aminoacetone (1-aminopropan-2-one), a putative minor biological source of methylglyoxal, reacts like other α-aminoketones such as 6-aminolevulinic acid (first heme precursor) and 1,4-diaminobutanone (a microbicide) yielding electrophilic α-oxoaldehydes, ammonium ion and reactive oxygen species by metal- and hemeprotein-catalyzed aerobic oxidation. A plethora of recent reports implicates triose phosphate-generated methylglyoxal in protein crosslinking and DNA addition, leading to age-related disorders, including diabetes. Importantly, methylglyoxal-treated hemoglobin adds four water-exposed arginine residues, which may compromise its physiological role and potentially serve as biomarkers for diabetes. This paper reports on the co-oxidation of aminoacetone and oxyhemoglobin in normally aerated phosphate buffer, leading to structural changes in hemoglobin, which can be attributed to the addition of aminoacetone-produced methylglyoxal to the protein. Hydroxyl radical-promoted chemical damage to hemoglobin may also occur in parallel, which is suggested by EPR-spin trapping studies with 5,5-dimethyl-1-pyrroline-N-oxide and ethanol. Concomitantly, oxyhemoglobin is oxidized to methemoglobin, as indicated by characteristic CD spectral changes in the Soret and visible regions. Overall, these findings may contribute to elucidate the molecular mechanisms underlying human diseases associated with hemoglobin dysfunctions and with aminoacetone in metabolic alterations related to excess glycine and threonine.

    Palavras-Chave: hemoglobin; electron transfer; amino acids; acetone; glyoxal; peroxy radicals

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  • IPEN-DOC 27164

    BENALCAZAR JALKH, E.B.; BERGAMO, E.T.P.; MONTEIRO, K.N.; CESAR, P.F.; GENOVA, L.A. ; LOPES, A.C.O.; LISBOA FILHO, P.N.; COELHO, P.G.; SANTOS, C.F.; BORTOLIN, F.; PIZA, M.M.T.; BONFANTE, E.A.. Aging resistance of an experimental zirconia-toughened alumina composite for large span dental prostheses: optical and mechanical characterization. Journal of the Mechanical Behavior of Biomedical Materials, v. 104, p. 1-9, 2020. DOI: 10.1016/j.jmbbm.2020.103659

    Abstract: Purpose: To synthesize a zirconia-toughened alumina (ZTA) composite with 85% alumina matrix reinforced by 15% zirconia and to characterize its optical and mechanical properties before and after artificial aging, to be compared with a conventional dental zirconia (3Y-TZP). Material and methods: After syntheses, ZTA and 3Y-TZP powders were uniaxially and isostatically pressed. Greenbody samples were sintered and polished to obtain 80 disc-shaped specimens per group (12 x 1 mm, ISO 6872:2015). The crystalline content and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Optical properties were determined by the calculation of contrast ratio (CR) and translucency parameter (TP) using reflectance data. Mechanical properties were assessed by Vickers hardness, fracture toughness and biaxial flexural strength test (BFS). All analyses were conducted before and after artificial aging (20h, 134 °C, 0.22 MPa). Optical parameters and microhardness differences were evaluated through repeated-measures analysis of variance (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). Results: The synthesis of the experimental ZTA composite was successful, with 98% of theoretical density, as shown in the SEM images. XRD patterns revealed typical zirconia and alumina crystalline phases. ZTA optical properties parameters showed no effect of aging, with a high CR and low TP values denoting a high maskingability. 3Y-TZP presented lower masking-ability and aging significantly affected its optical properties. ZTA Vickers hardness, fracture toughness and Weibull parameters, including characteristic stress and Weibull modulus were not influenced by aging, while 3Y-TZP presented a significant decrease in characteristic stress and increase in fracture toughness after aging. The ZTA probability of survival for missions of 300 and 500 MPa was estimated at ~99% validating its use for 3-unit posterior fixed dental prostheses (FDP), and no different from conventional 3Y-TZP. At high-stress mission (800 MPa) a significant decrease in probability of survival was observed for aged 3Y-TZP (84%) and for immediate and aged ZTA (73 and 82% respectively). Conclusion: The ZTA composite presented a dense microstructure, with preservation of the crystalline content, optical and mechanical properties after artificial aging, which encourages future research to validate its potential use for large span FDP.

    Palavras-Chave: aluminium oxides; zirconium oxides; aging; ceramics; microstructure; optical properties; optical microscopes

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  • IPEN-DOC 27560

    JALKH, ERNESTO B.B.; MONTEIRO, KELLI N.; CESAR, PAULO F.; GENOVA, LUIS A. ; BERGAMO, EDMARA T.P.; LOPES, ADOLFO C. de O.; LIMA, ERICK; LISBOA-FILHO, PAULO N.; CAMPOS, TIAGO M.B.; WITEK, LUKASZ; COELHO, PAULO G.; BORGES, ANA F.S.; BONFANTE, ESTEVAM A.. Aging resistant ZTA composite for dental applications: microstructural, optical and mechanical characterization. Dental Materials, v. 36, n. 9, p. 1190-1200, 2020. DOI: 10.1016/j.dental.2020.05.011

    Abstract: Objective. To synthesize a zirconia toughened alumina (ZTA) composite with 70% aluminareinforced by 30% zirconia for dental applications and to characterize its microstructureand optical properties for comparison with the isolated counterpart materials and a first-generation 3Y-TZP.Methods. Disc-shaped specimens were divided in four groups (n = 70/material): (1) 3YSB-E(first generation 3Y-TZP), (2) Zpex (second generation 3Y-TZP), (3) alumina, and (4) ZTA-Zpex70/30. After synthesis, ceramic powders were pressed, and green-body samples sinteredfollowing a predetermined protocol. Specimens were polished to obtain a mirror surfacefinish. Apparent density was measured by Archimedes principle. X-ray diffraction (XRD)and scanning electron microscope (SEM) were used to characterize the crystalline contentand microstructure. Reflectance tests were performed to determine the contrast-ratio (CR)and translucency-parameter (TP). Mechanical properties were assessed by biaxial flexuralstrength (BFS) test. All analyses were conducted before and after artificial aging (20 h, 134◦C, 2.2 bar). Optical parameters were evaluated through repeated-measures analysis of variance and Tukey tests (p < 0.05). BFS data were analyzed using Weibull statistics (95% CI). Results. High density values (95–99%) were found for all ceramic materials and SEM images exhibited a dense microstructure. While XRD patterns revealed the preservation of crys- talline content in the ZTA composite, an increase in the monoclinic peak was observed for pure zirconias after aging. Significantly higher CR and lower TP values were observed for the ZTA composite, followed by alumina, 3YSB-E, and Zpex. The highest characteristic stress was recorded for 3YSB-E, followed by intermediate values between ZTA and Zpex, and the lowest for alumina. Aging affected the optical and mechanical properties of both zirconias, while remained stable for ZTA composite and alumina. Significance. The synthesis of experimental 70−30% ZTA composite was successful and its relevance for dental applications relies on its higher masking ability, aging resistance, and strength similar to zirconia.

    Palavras-Chave: composite materials; zirconium oxides; aluminium oxides; mechanical properties; optical properties; microstructure; dentistry; prostheses

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