INSTITUTO DE PESQUISAS ENERGÉTICAS E NUCLEARES
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Navegação Periódicos - Artigos por Agências de fomento "Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)"

Navegação Periódicos - Artigos por Agências de fomento "Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)"

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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 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 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 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 27125

    BELLEZZO, MURILLO ; FONSECA, GABRIEL P.; VONCKEN, ROBERT; VERRIJSSEN, AN-SOFIE; VAN BEVEREN, CELINE; ROELOFS, ERIK; YORIYAZ, HELIO ; RENIERS, BRIGITTE; VAN LIMBERGEN, EVERT J.; BERB EE, MAAIKE; VERHAEGEN, FRANK. Advanced design, simulation, and dosimetry of a novel rectal applicator for contact brachytherapy with a conventional HDR 192Ir source. Brachytherapy, v. 19, n. 4, p. 544-553, 2020. DOI: 10.1016/j.brachy.2020.03.009

    Abstract: PURPOSE: Dose escalation yields higher complete response to rectal tumors, which may enable the omission of surgery. Dose escalation using 50 kVp contact x-ray brachytherapy (CXB) allow the treatment of a selective volume, resulting in low toxicity and organs-at-risk preservation. However, the use of CXB devices is limited because of its high cost and lack of treatment planning tools. Hence, the MAASTRO applicator (for HDR 192Ir sources) was developed and characterized by measurements and Monte Carlo simulations to be a cost-effective alternative to CXB devices. METHODS AND MATERIALS: A cylindrical applicator with lateral shielding was designed to be used with a rectoscope using its tip as treatment surface. Both the applicator and the rectoscope have a slanted edge to potentially allow easier placement against tumors. The applicator design was achieved by Monte Carlo modeling and validated experimentally with film dosimetry, using the Papillon 50 (P50) device as reference. RESULTS: The applicator delivers CXB doses in less than 9 min using a 20375 U source for a treatment area of approximately 20 20 mm2 at 2 mm depth. Normalized at 2 mm, the dose falloff for depths of 0 mm, 5 mm, and 10 mm are 130%, 70%, and 43% for the P50 and 140%, 67%, and 38% for the MAASTRO applicator, respectively. CONCLUSIONS: The MAASTRO applicator was designed to use HDR 192Ir sources to deliver a dose distribution similar to those of CXB devices. The applicator may provide a cost-effective solution for endoluminal boosting with clinical treatment planning system integration.

    Palavras-Chave: brachytherapy; monte carlo method; rectal administration; iridium 192; dose rates; radiation sources; simulation; radiotherapy; neoplasms; film dosimetry

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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 27704

    OLIVEIRA, DANIEL C.F. dos S.; MONTILLA-ROSERO, ELENA; LOPES, FABIO J. da S. ; MORAIS, FERNANDO G. ; LANDULFO, EDUARDO ; HOELZEMANN, JUDITH J.. Aerosol properties in the atmosphere of Natal/Brazil measured by an AERONET Sun-photometer. Environmental Science and Pollution Research, v. 28, n. 8, p. 9806-9823, 2021. DOI: 10.1007/s11356-020-11373-z

    Abstract: We analyzed data measured by a Sun-photometer of the RIMA-AERONET network with the purpose to characterize the aerosol properties in the atmosphere over Natal, state capital of Rio Grande do Norte, at the coast of Northeast Brazil. Aerosol Optical Depth, Ångström Exponent, Volume Size Distribution, Single Scattering Albedo, Complex Refractive Index, Asymmetry Factor, and Precipitable Water were analyzed from August 2017 to March 2018. In addition, MODIS and CALIOP observations, local Lidar measurements, and modeled backward trajectories were analyzed in a case study on February 9, 2018, that consistently confirmed the identification of a persistent aerosol layer below 4 km agl. Aerosols present in the atmosphere of Natal showed monthly mean Aerosol Optical Depth at 500 nm below 0.15 (~ 75%), monthly means of the Ångström Exponent at 440–670 nm between 0.30 and 0.70 (~ 69%), bimodal Volume Size Distribution is dominantly coarse mode, Single Scattering Albedo at 440 nm is 0.80, Refractive Index - Real Part around 1.50, Refractive Index - Imaginary Part ranging from 0.01 to 0.04, and the Asymmetry Factor ranged from 0.73 to 0.80. The aerosol typing during the measurement period showed that atmospheric aerosol over Natal is mostly composed of mixed aerosol (58.10%), marine aerosol (34.80%), mineral dust (6.30%), and biomass burning aerosols (0.80%). Backward trajectories identified that 51% of the analyzed air masses over Natal originated from the African continent.

    Palavras-Chave: satellite atmospheres; sun; photometers; optical radar; optical systems; aerial monitoring; atmospheres; optical properties; dusts; environment; environmental impacts; physical properties; biomass; brazil; africa; climatic change

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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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  • IPEN-DOC 27575

    LICHTENTHALER, R.; APPANNABABU, S.; ALVAREZ, M.A.G.; RODRIGUEZ-GALLARDO, M.; LEPINE-SZILY, A.; PIRES, K.C.C.; SANTOS, O.C.B.; UMBELINO, U.; FARIA, P.N. de; GUIMARAES, V.; ZEVALLOS, E.O.N.; SCARDUELLI, V.; ASSUNCAO, M.; SHORTO, J.M.B. ; BARIONI, A.; ALCANTARA-NUNEZ, J.; MORCELLE, V.; SERRA, A.. Alpha-particle production in the 6He+120Sn collision. Journal of Physics: Conference Series, v. 1643, p. 1-6, 2020. DOI: 10.1088/1742-6596/1643/1/012093

    Abstract: Alpha particle energy distributions in the 6He+120Sn collision have been measured at 7 bombarding energies above the Coulomb barrier. A phenomenological analysis of the centroids of the experimental distributions was performed and compared with the expected alpha-particle energies from breakup and neutron transfer reactions. Q-optimum conditions were determined using the Brinks formula for the di-neutron transfer reaction. A comparison of the measured alpha-particle production cross-sections with Continuum Discretized Coupled Channels (CDCC) calculations for breakup is presented.

    Palavras-Chave: alpha particles; helium 6; energy spectra; elastic scattering; neutron transfer; coupled channel theory; angular momentum

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  • IPEN-DOC 27841

    BERGAMO, EDMARA T.P.; CARDOSO, KARINA B.; LINO, LUCAS F.O.; CAMPOS, TIAGO M.B.; MONTEIRO, KELLI N.; CESAR, PAULO F.; GENOVA, LUIS A. ; THIM, GILMAR P.; COELHO, PAULO G.; BONFANTE, ESTEVAM A.. Alumina-toughened zirconia for dental applications: physicochemical, mechanical, optical, and residual stress characterization after artificial aging. Journal of Biomedical Materials Research Part B: Applied Biomaterials, v. 109, n. 8, p. 1135-1144, 2021. DOI: 10.1002/jbm.b.34776

    Abstract: To characterize the physicomechanical properties of an alumina-toughened zirconia (ATZ). ATZ synthesis consisted of the addition of alumina particles in an yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) matrix. Specimens were obtained by uniaxial and isostatic pressing ATZ and 3Y-TZP powders and sintering at 1600°C/1 h and 1550°C/1 h, respectively. Crystalline content and residual stress were evaluated using X-ray diffraction (XRD). Microstructure was characterized by scanning electron microscopy (SEM). Optical properties were determined by reflectance test. Mechanical properties were assessed by biaxial flexural strength test. All analyses were performed before and after aging (134°C, 20 h, 2 bar). XRD and SEM revealed a typical ATZ and 3Y-TZP crystalline content, chiefly tetragonal phase, with a dense polycrystalline matrix, though a smaller grain size for ATZ. Aging triggered a similar monoclinic transformation for both systems; however, ATZ exhibited higher residual compressive stresses than 3Y-TZP. While as-processed 3Y-TZP demonstrated significantly higher characteristic strength relative to ATZ, no significant difference was observed after aging (~215 MPa increase in the ATZ strength). ATZ presented significantly higher opacity relative to 3Y-TZP, although aging significantly increased the translucency of both systems (increase difference significantly higher in the 3Y-TZP compared to ATZ). ATZ physicomechanical properties support its applicability in the dental field, with a lower detrimental effect of aging relative to 3Y-TZP.

    Palavras-Chave: zirconium; dentistry; ceramics; composite materials; optical properties; aging

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  • IPEN-DOC 28503

    BASSO, LUANA S.; MARANI, LUCIANO; GATTI, LUCIANA V. ; MILLER, JOHN B.; GLOOR, MANUEL; MELACK, JOHN; CASSOL, HENRIQUE L.G.; TEJADA, GRACIELA; DOMINGUES, LUCAS G. ; ARAI, EGIDIO; SANCHEZ, ALBER H.; CORREA, SERGIO M.; ANDERSON, LIANA; ARAGAO, LUIZ E.O.C.; CORREIA, CAIO S.C. ; CRISPIM, STEPHANE P.; NEVES, RAIANE A.L.. Amazon methane budget derived from multi-year airborne observations highlights regional variations in emissions. Communications Earth & Environment, v. 2, n. 1, p. 1-13, 2021. DOI: 10.1038/s43247-021-00314-4

    Abstract: Atmospheric methane concentrations were nearly constant between 1999 and 2006, but have been rising since by an average of ~8 ppb per year. Increases in wetland emissions, the largest natural global methane source, may be partly responsible for this rise. The scarcity of in situ atmospheric methane observations in tropical regions may be one source of large disparities between top-down and bottom-up estimates. Here we present 590 lower-troposphere vertical profiles of methane concentration from four sites across Amazonia between 2010 and 2018. We find that Amazonia emits 46.2 ± 10.3 Tg of methane per year (~8% of global emissions) with no temporal trend. Based on carbon monoxide, 17% of the sources are from biomass burning with the remainder (83%) attributable mainly to wetlands. Northwest-central Amazon emissions are nearly aseasonal, consistent with weak precipitation seasonality, while southern emissions are strongly seasonal linked to soil water seasonality. We also find a distinct east-west contrast with large fluxes in the northeast, the cause of which is currently unclear.

    Palavras-Chave: methane; emission; ecological concentration; climates; amazon river

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  • IPEN-DOC 27964

    GATTI, LUCIANA V. ; BASSO, LUANA S.; MILLER, JOHN B.; GLOOR, MANUEL; DOMINGUES, LUCAS G. ; CASSOL, HENRIQUE L.G.; TEJADA, GRACIELA; ARAGAO, LUIZ E.O.C.; NOBRE, CARLOS; PETERS, WOUTER; MARANI, LUCIANO; ARAI, EGIDIO; SANCHES, ALBER H.; CORREA, SERGIO M.; ANDERSON, LIANA; VON RANDOW, CELSO; CORREIA, CAIO S.C. ; CRISPIM, STEPHANE P.; NEVES, RAIANE A.L.. Amazonia as a carbon source linked to deforestation and climate change. Nature, v. 595, n. 7867, p. 388-393, 2021. DOI: 10.1038/s41586-021-03629-6

    Abstract: Amazonia hosts the Earth’s largest tropical forests and has been shown to be an important carbon sink over recent decades. This carbon sink seems to be in decline, however, as a result of factors such as deforestation and climate change. Here we investigate Amazonia’s carbon budget and the main drivers responsible for its change into a carbon source. We performed 590 aircraft vertical profiling measurements of lower-tropospheric concentrations of carbon dioxide and carbon monoxide at four sites in Amazonia from 2010 to 2018. We find that total carbon emissions are greater in eastern Amazonia than in the western part, mostly as a result of spatial differences in carbon-monoxide-derived fire emissions. Southeastern Amazonia, in particular, acts as a net carbon source (total carbon flux minus fire emissions) to the atmosphere. Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends. We explore the effect of climate change and deforestation trends on carbon emissions at our study sites, and find that the intensification of the dry season and an increase in deforestation seem to promote ecosystem stress, increase in fire occurrence, and higher carbon emissions in the eastern Amazon. This is in line with recent studies that indicate an increase in tree mortality and a reduction in photosynthesis as a result of climatic changes across Amazonia.

    Palavras-Chave: climatic change; burns; carbon sources; emission; deforestation; troposphere; temperature measurement; environmental impacts; amazon river

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  • IPEN-DOC 29949

    LOPES, ISABELA S.; SILVA, FLAVIA R. de O. ; COURROL, LILIA C.. Aminolevulinic acid coated—silver, copper, and silver–copper nanoparticles: synthesis, characterization, and application in seed nanopriming. Journal of Plant Growth Regulation, v. 42, n. 9, p. 5842–5854, 2023. DOI: 10.1007/s00344-023-10969-2

    Abstract: Seed priming is a potential tool for improving productivity under diferent environmental conditions. Aminolevulinic acid (ALA) priming can enhance plant tolerance to abiotic stresses, such as salinity, drought, and extreme temperatures. Nanopriming, priming with nanoparticles, can increase seed germination, growth, and plant development. The goal of this work was to compare the germination, growth, and development of sunfower seeds primed at 25 °C for 24 h with fve treatments: water, ALA, silver, copper, and copper-silver nanoparticles (ALANPs) using a two-way analysis of variance. ALANPs were prepared by the photoreduction process (ALA as stabilizing/capping agent) and characterized by UV–Vis, transmission electron microscopy, FTIR, and Zeta potential. The germination percentage, shoot length, root length, seedling vigor index (Vi), and allometric coefcient were obtained on the 3rd, 6th, and 10th days after the priming process. The fuorescence spectra of chlorophyll extract of the whole seedling or directly in the cotyledons were measured. According to the results, seed priming with ALANPs enhanced sunfower seed germination capacity, seed growth, and increased chlorophyll production compared to water and ALA-primed seeds.

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  • IPEN-DOC 29688

    ARAUJO, LEANDRO G. de ; MEDEIROS, VINICIUS L.; GUARNIERI, GUILHERME de P.; SILVA, DANILO A. da; WATANABE, TAMIRES ; MARUMO, JULIO T. ; NERY, JOSE G.. An adsorption agent based on chitosan–zeolite composite: environmental and radioactive liquid waste remediation. Environmental Science: Advances, v. 2, n. 3, p. 484–494, 2023. DOI: 10.1039/d2va00148a

    Abstract: In this article, we present a chitosan–zeolite composite, which was synthesized and used as an adsorbent material for caesium (Cs) removal from aqueous media and real liquid radioactive organic waste (LROW). The compound was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques. The physicochemical characterization indicates the production of a composite. Adsorption experiments were first performed using the prepared solutions contaminated with Cs using full factorial design with two variables of interest: initial Cs concentration (Cs0) and adsorbent dosage (mg L−1 ). The results indicated a high caesium removal rate with removal values above 93% and adsorption capacity of up to 10 mg g−1 . With the best experimental conditions according to our experimental domain, time was evaluated and equilibrium was reached in 180 min. Finally, the adsorbent material was tested as an adsorbent for Cs, Am, and U from LROW. When in contact with LORW, the removal rates (%) were 21.51 (137Cs), 26.39 (241Am), and 20.26 (U (total)). Although lower, this material indicated that it has the potential to be used for multi-elemental adsorption.

    Palavras-Chave: adsorption; chitin; zeolites; polysaccharides; radioactive wastes; liquid wastes; radioactive effluents

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A elaboração do projeto do RI do IPEN foi iniciado em novembro de 2013, colocado em operação interna em julho de 2014 e disponibilizado na Internet em junho de 2015. Utiliza o software livre Dspace, desenvolvido pelo Massachusetts Institute of Technology (MIT). Para descrição dos metadados adota o padrão Dublin Core. É compatível com o Protocolo de Arquivos Abertos (OAI) permitindo interoperabilidade com repositórios de âmbito nacional e internacional.

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O Repositório Digital do IPEN é um equipamento institucional de acesso aberto, criado com o objetivo de reunir, preservar, disponibilizar e conferir maior visibilidade à Produção Científica publicada pelo Instituto, desde sua criação em 1956.

Operando, inicialmente como uma base de dados referencial o Repositório foi disponibilizado na atual plataforma, em junho de 2015. No Repositório está disponível o acesso ao conteúdo digital de artigos de periódicos, eventos, nacionais e internacionais, livros, capítulos, dissertações, teses e relatórios técnicos.

A elaboração do projeto do RI do IPEN foi iniciado em novembro de 2013, colocado em operação interna em julho de 2014 e disponibilizado na Internet em junho de 2015. Utiliza o software livre Dspace, desenvolvido pelo Massachusetts Institute of Technology (MIT). Para descrição dos metadados adota o padrão Dublin Core. É compatível com o Protocolo de Arquivos Abertos (OAI) permitindo interoperabilidade com repositórios de âmbito nacional e internacional.

O gerenciamento do Repositório está a cargo da Biblioteca do IPEN. Constam neste RI, até o presente momento 20.950 itens que tanto podem ser artigos de periódicos ou de eventos nacionais e internacionais, dissertações e teses, livros, capítulo de livros e relatórios técnicos. Para participar do RI-IPEN é necessário que pelo menos um dos autores tenha vínculo acadêmico ou funcional com o Instituto. Nesta primeira etapa de funcionamento do RI, a coleta das publicações é realizada periodicamente pela equipe da Biblioteca do IPEN, extraindo os dados das bases internacionais tais como a Web of Science, Scopus, INIS, SciElo além de verificar o Currículo Lattes. O RI-IPEN apresenta também um aspecto inovador no seu funcionamento. Por meio de metadados específicos ele está vinculado ao sistema de gerenciamento das atividades do Plano Diretor anual do IPEN (SIGEPI). Com o objetivo de fornecer dados numéricos para a elaboração dos indicadores da Produção Cientifica Institucional, disponibiliza uma tabela estatística registrando em tempo real a inserção de novos itens. Foi criado um metadado que contém um número único para cada integrante da comunidade científica do IPEN. Esse metadado se transformou em um filtro que ao ser acionado apresenta todos os trabalhos de um determinado autor independente das variáveis na forma de citação do seu nome.