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

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. Disponível em: http://repositorio.ipen.br/handle/123456789/32019. Acesso em: $DATA.

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Abstract: The preparation of novel triply-doped bifunctional Fe3O4/ZnS@LaF3:xCe3+,xGd3+,yTb3+ (x = 5; y = 5, 10 and 15 mol%) nanocomposites with efficient optical and magnetic features has been reported. The ZnS semiconductor functionalized Fe3O4 particles were coated with LaF3:RE3+ materials via a chitosanassisted co-precipitation method. The size of iron oxide B7.2 nm and trigonal structures of bifunctional nanostructures were confirmed through X-ray diffraction and high-resolution transmission electron microscopy. The static magnetic measurements supported and manifested the superparamagnetic behavior of the materials at 300 K. A broad emission band was observed in the blue region (400–550 nm) due to the sulphur vacancy on the surface of the Fe3O4/ZnS nanocomposite. For a triply doped bifunctional nanostructure, the excitation spectra revealed broad absorption bands centered at around 270 nm, which were attributed to the 4f(7F7/2) - 5d interconfigurational transition of the Ce3+ ion accompanied by narrow absorption lines arising from the 4f–4f intraconfigurational transitions of the Tb3+ ion. The emission spectra of the nanocomposites showed characteristic narrow emission lines assigned to the 5D4 - 7FJ transitions (J = 6–0) of the Tb3+ ion. The energy transfer process from the Ce3+ - Gd3+ - Tb3+ ions has also been presented and discussed. Furthermore, the structural, photoluminescence and magnetic properties of Fe3O4/ZnS@LaF3:RE3+ suggested that it may be an efficient candidate for magnetic light-converting molecular devices (MLMCDs) and high energy radiation detection.

Palavras-Chave: fluorescence; nmr imaging; iron oxides; buildings; building materials; nanoparticles; zinc sulfides; lanthanum fluorides; cerium ions; gadolinium ions; terbium ions; nanocomposites

SHRIVASTAVA, NAVADEEP; KHAN, L.U.; KHAN, Z.U.; VARGAS, J.M.; MOSCOSO-LONDONO, O.; OSPINA, CARLOS; BRITO, H.F.; JAVED, YASIR; FELINTO, M.C.F.C.; MENEZES, A.S.; KNOBEL, MARCELO; SHARMA, S.K. Building block magneto-luminescent nanomaterials of iron-oxide/ZnS@LaF3:Ce3+,Gd3+,Tb3+ with green emission. Journal of Materials Chemistry C, v. 5, n. 9, p. 2282-2290, 2017. DOI: 10.1039/c6tc05053k. Disponível em: http://repositorio.ipen.br/handle/123456789/27861. Acesso em: $DATA.

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Abstract: In this work was studied the effect of nanoparticle incorporation in the dimensional stability of elastomer matrix. To avoid excessive swelling and consequently dimensional instability in the films, crosslinking has been shown to be an efficient and simple method for achieve the reducing membrane swelling and improving mechanical stability. The elastomer used was a fluorinated type, with 70% of fluor in its composition and commercial clay (Cloisite®) was the nanofiller used. The nancomposites with 0.5, 1 or 2% (wt%) of nanoclay were prepared in a open two roll mill. The fluoroelastomer was a type of Viton® (DuPont) which has low fuel permeation and suitable for use as sealant mainly for o-ring production. The incorporation of clay in the polymer matrix aimed to avoid excessive swelling and to maintain the material dimensional stability. The nanocomposites were characterized by stress–strain test to evaluated elongation and tension at break, by rheometry to analyzed maximum and minimum torques, and degree of swelling to follow dimensional size modification of nanocomposites films. There were a decreasing of the elongation at break and of degree of swelling values what can be correlated to an increase of crosslinking, and consequently formation of a networking in the nanocomposites matrix in the films evaluated

Palavras-Chave: nanocomposites; clays; silicate minerals; elastomers; fluorine; polymerization

ZEN, HELOISA A.; LUGAO, ADEMAR B. Effect of clay incorporation in the dimensional stability of FKM nanocomposite. Revista Matéria, v. 22, n. 2, 2017. DOI: 10.1590/S1517-707620170002.0178. Disponível em: http://repositorio.ipen.br/handle/123456789/28507. Acesso em: $DATA.

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Abstract: This study had as its main objective to evaluate the flexural properties (strength and modulus) and degree of conversion of a dimethacrylate resin containing different amounts of nanoparticulated clay Montomorillonite (MMT) as filler. A series of composites containing similar amounts (in volume) of barium glass particles was also tested as control data. Eight formulations with polymeric matrix-based BisGMA/TEGDMA (Bisphenol A Bis(2-hydroxy-3 methacryloxypropyl)Ether/ Triethyleneglycol Dimethacrylate), four added with MMTand four added with barium glass in the volume concentration of 20, 30, 40 and 50 vol% were studied. The degree of conversion was determined using near-IR spectroscopy. Elastic modulus and flexural strength were determined by the three-point bending test. The dispersion of MMT nanoparticles was determined by means of X-ray diffraction and transmission electron microscopy analysis. The fillers montomorillonite and barium glass interacted with polymer matrix-based BisGMA/TEGDMA in a distinct manner. Although the addition of montomorillonite nanoparticles resulted in similar degree of conversion and higher elastic modulus values at all concentrations tested, only at the 20 vol% the flexural strength was statistically higher, compared to the control groups filled with barium glass. This could be related to the need of concentration optimization of montomorillonite for each type of polymer matrix in order to adjust or improve mechanical properties. The addition of low concentrations (<l 20% vol) of montomorillonite nanoparticles in dental composites resins – such as additive or hybrid filler – should be studied, aiming to the reduction of polymerization shrinkage, better mechanical properties and improvement of a new technology for future applications.

Palavras-Chave: evaluation; montmorillonite; nanoparticles; clays; nanocomposites; mechanical properties; flexural strength; x-ray diffraction; transmission electron microscopy; scanning electron microscopy

CAMPOS, LUIZA M.P.; BOARO, LETICIA C.; SANTOS, TAMIRIS M.R.; MARQUES, PAMELA A.; ALMEIDA, SONIA R.Y.; BRAGA, ROBERTO R.; PARRA, DUCLERC F. Evaluation of flexural modulus, flexural strength and degree of conversion in BISGMA/TEGDMA resin filled with montmorillonite nanoparticles. Journal of Composite Materials, v. 29, p. 1-11, 2016. DOI: 10.1177/0021998316656925. Disponível em: http://repositorio.ipen.br/handle/123456789/26970. Acesso em: $DATA.

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Abstract: Interfacial or separate phase location of carbonaceous nanofillers (graphene and carbon nanotubes) in polymer blends with co-continuous phases can lead to double percolation behavior, significantly increasing rheological and electrical properties. The prediction of the morphology and the location of the nanofillers has been used as a tool to evaluate the proprieties of co-continuous polymer blends. This work aims to highlight the superior conductivity levels achieved using a low amount of carbon-based fillers, by the proper selection in a multiphase polymer matrix as a template for controlled dispersion and spatial distribution of the nanoparticles, offering a compromise between easy processability and enhanced performance. Here, two polymers (linear low-density polyethylene [LLDPE] and ethylene-co-methylacrylate [EMA]) and their cocontinuous blend (LLDPE/EMA) were loaded with nanofillers (few-layer graphene [FLG], few-walled carbon nanotube [FWCNT]) via continuous melt mixing in twin-screw extrusion, separate and simultaneously. It was observed that the addition of the nanofillers changed the co-continuity of the blend, with the probable migration of the nanofillers from the EMA (hydrophilic) phase to the LLDPE (hydrophobic) phase. Rheological percolation occurred preferentially in blends containing FWCNT and FLG/FWCNT. Electrical conductivity was observed in all compositions, with higher electrical conductivity being noticed in hybrids.

Palavras-Chave: nanocomposites; hybridization; nanotechnology; polyethylenes; polymers; electric conductivity; carbon nanotubes; graphene

NUNES, MARIO A.B.S.; MATOS, BRUNO R. de; SILVA, GLAURA G.; ITO, EDSON N.; MELO, TOMAS J.A. de; FECHINE, GUILHERMINO J.M. Hybrids nanocomposites based on a polymer blend (linear low-density polyethylene/poly(ethylene-co-methyl acrylate) and carbonaceous fillers (graphene and carbon nanotube). Polymer Composites, v. 42, n. 2, p. 661-677, 2021. DOI: 10.1002/pc.25856. Disponível em: http://repositorio.ipen.br/handle/123456789/31940. Acesso em: $DATA.

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Abstract: Many studies report that nanocomposites obtained by dispersion of a small amount nanofiller into the polymer have remarkable improvements achieved in the mechanical and physical properties. However, in order to achieve this great improvement in properties, it is necessary that the nanofillers be dispersed homogeneously into the polymeric matrix. Often this dispersion is difficult to achieve due to the high interfacial energy of the nanoparticles present. This study reports the effect of gamma irradiation induced graft of glycidyl methacrylate (GMA) onto the surface of TiO2 and Clay nanofillers to improve their dispersion into the EVA matrix. The physical and mechanical properties of Ethylene-vinyl acetate copolymer (EVA) flexible films with these nanoparticles were studied. EVA nanocomposite with adding of the different amount of TiO2 and modified montmorillonite clay grafted and un-grafted with glycidyl methacrylate (GMA) using gamma irradiation have been prepared by melt extrusion. The nanocomposite flexible films were produced using a flat die extrusion process. The PGMA-grafted nanofillers were characterized by XRD and TEM analysis. The flexible films were characterized by Tensile tests, ATR–FTIR, UV–VIS, XRD, TG, and FE-SEM analysis to understand the nature of the interaction between the nanofillers and EVA matrix. The results showed that the addition of PGMA-grafted TiO2 and Clay nanofillers into EVA matrix improved the bonding between the nanofillers and matrix. It was also found that the PGMA-grafted nanofillers could be well dispersed into an EVA matrix in contrast to that of un-grafted. The tensile strength and modulus of the resulting EVA/TiO2-PGMA enhanced in comparison to that of un-grafted TiO2. The EVA/Clay-PGMA had slightly decreased tensile strength comparable to that of EVA/Clay but had considerably improved elastic modulus. In addition, the flexible films based on TiO2 exhibited high UV–Vis light absorption with energy gap shifted to the visible region. The results demonstrated that TiO2 and Clay nanofillers grafted with GMA by gamma radiation can be used to prepare EVA flexible films with improved bonding between the nanofillers and matrix and, consequently, enhanced properties for food and cosmetic packaging application.

Palavras-Chave: dispersions; films; gamma radiation; irradiation; methacrylates; nanocomposites; physical properties; polymerization; titanium oxides; x-ray diffraction

BARTOLOMEI, SUELLEN S.; SANTANA, JULYANA G.; DIAZ, FRANCISCO R.V.; KAVAKLI, PINAR A.; GUVEN, OLGUN; MOURA, ESPERIDIANA A.B. Investigation of the effect of titanium dioxide and clay grafted with glycidyl methacrylate by gamma radiation on the properties of EVA flexible films. Radiation Physics and Chemistry, v. 169, p. 1-9, 2020. DOI: 10.1016/j.radphyschem.2018.08.022. Disponível em: http://repositorio.ipen.br/handle/123456789/31073. Acesso em: $DATA.

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Abstract: It is estimated that there are about 300,00 products named biomaterials that are used in the area of Health. Although they are widely used they have yet to be optimized for therapeutic use. Hence, the objective of this work was to develop nanocomposites hydrogels with poly (vinyl alcohol) (PVAl), glucantime, chitosan and synthetic clay Laponite RD, processed by gamma irradiation. To compare the behavior of drug release two systems were compared, PVAl / chitosan / clay and PVAl / clay. The morphology of the nanocomposites hydrogel was understood by using characterization techniques: X-ray diffraction, scanning electron microscopy (SEM) and atomic force microscopy (AFM) and gel fraction. The release kinetics was analyzed at 37 °C for period of 48 hours. It was observed that the slower release of the drug occurs in the delivery system composed by PVAl / chitosan / clay with correlation of the crosslink type formed by chitosan.

Palavras-Chave: nanocomposites; polymers; clays; hydrogels; polysaccharides; drugs

OLIVEIRA, MARIA J.A.; LUGAO, ADEMAR B.; PARRA, DUCLERC F. Nanocomposite polymer clay to support the release of drug. Materials Science Forum, v. 899, p. 335-340, 2017. DOI: 10.4028/www.scientific.net/MSF.899.335. Disponível em: http://repositorio.ipen.br/handle/123456789/28495. Acesso em: $DATA.

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