Navegação Eventos - Resumos por Autores IPEN "GARCIA, RAFAEL H.L."

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  • IPEN-DOC 24852

    SOUSA, THAINA S. ; JACOVONE, RAYNARA M.S. ; SOARES, JAQUELINE J.S. ; RODRIGUES, DEBORA F.; SILVA, FLAVIA R. de O. ; GARCIA, RAFAEL H.L. ; ZAIM, MARCIO H.; SAKATA, SOLANGE K. . Antimicrobial activity of Graphene Oxide/Silver nanocomposite obtained by Electron Beam. In: PAN AMERICAN CONGRESS OF NANOTECHNOLOGY, 1st, 27-30 de novembro, 2017, Guarujá, SP. Abstract... 2017.

    Abstract: Graphene oxide is a carbon-based nano material that has a high specific surface area, high chemical stability, excellent electrical and thermal conductivities, high mechanical resistance, the oxygen groups facilitate dispersion in polar solvents and its functionalization. In the literature, is described several methods of metal incorporation on graphene oxide surface using toxic reagents or with long periods of reaction. The objective of this work is to develop an innovative and sustainable method of incorporating silver into graphene oxide that does not involve toxic reagents or generated residues. in a short reaction time at room temperature beyond the use of the as an alternative process to the chemical processes traditional.A silver solution in the complex form was added to a dispersed graphene oxide in water/isopropanol solution. The mixture wassubmitted to a dose of radiation ranged from 150 to 400 KGy using a electron beam acelerator. The nanocomposite GO/Ag characterization was performed by thermogravimetry analysis (TGA), X-ray diffraction (XDR), scanning transmission electron microscope coupled to the energy dispersive X-ray spectrometry (TEM/EDS). The antimicrobial activity of GO/Ag was observed by Escherichia coli, a Gram negative bacterium and Bacillus subtilis a Gram positive bacterium in solid culture medium. The minimum inhibitory concentration of GO/Ag was 50 mg/L. .It is noteworthy that the incorporation of silver occurred at the same time the reduction of graphene oxide without the generation of toxic chemical residues.

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  • IPEN-DOC 28095

    VIEIRA, ANA C.D.; KODAMA, YASKO ; OTUBO, LARISSA ; SANTOS, PAULO S. ; VASQUEZ, PABLO A.S. ; GARCIA, RAFAEL H.L. . Application of gamma irradiation to conservation: effects of ionizing radiation on the color of featherwork. In: ICOM-CC TRIENNIAL CONFERENCE, 19th, May 17-21, 2021, Beijing, China. Abstract... Paris, France: International Council of Museums, 2021.

    Abstract: Featherwork is one of the most remarkable categories of material culture produced by Brazilian indigenous peoples due to its technical qualities and aesthetic beauty. Weapons, baskets, and musical instruments are frequently decorated with feathers, which are also used in body adornments that, in addition to their aesthetic purpose, are intended to convey information about the wearer, their position within a group, and the cultural values that they wish to transmit. The preservation of this type of artifacts is demanding given the biological cycle of the organic materials that compose them, which are inevitably subject to various stages of deterioration. In addition to the damage resulting from their use and perishable materials, these ethnographic objects are exposed to a new environment when they are incorporated into museum collections, where their existence must be prolonged. Since Brazil’s tropical climate often leads to pest proliferation, their degradation can be exacerbated by the action of insects such as moths and microorganisms such as fungi with irreversible consequences, making their conservation a daily challenge. Although the art of featherwork is still practiced by indigenous communities, the scarce supply of raw materials and contact with the tribes involved has reduced the scale of production. The preservation of this material heritage is thus very important, particularly in ethnographic museums. The use of gamma radiation for the disinfestation of cultural heritage artifacts and archived materials has been shown to be a safe process and an excellent alternative to traditional methods, which usually involve toxic chemical pesticides. Ionizing radiation has been used for more than 40 years and, since 2004, the Multipurpose Irradiator at the Institute of Energy and Nuclear Research (IPEN), a pioneering technology developed in Brazil, has made its application to cultural heritage a reality. With more than 20,000 cultural artifacts irradiated, IPEN is currently the national and international reference center for the use of radiation technology applied to the preservation of cultural heritage collections. Several studies have been conducted to determine the optimal dose required to eliminate contamination by biological agents in organic materials such as wood, leather, and feathers.A maximum dose of 10 kGy is recommended for featherwork in order to avoid affecting the physical and chemical properties of this type of material. This poster reports on the results of the effects of ionizing radiation on the color and morphological properties of a featherwork from the Museum of Archaeology and Ethnology at the University of São Paulo (MAE/USP). Samples of feathers were selected and irradiated with gamma rays at the Multipurpose Gamma Irradiation Facility, applying absorbed doses of between 0.5 and 200 kGy. The samples were chosen according to the color of the feathers and then photographed and analyzed using colorimetry based on the CIELAB 1976 color space scale before and 48 hours after irradiation and scanning electron microscopy. There were no significant changes in morphological and color properties within the disinfestation range applied.

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  • IPEN-DOC 10690

    GARCIA, RAFAEL H.L.; SALIBA SILVA, ADONIS M.; LIMA, NELSON B. de. Choosing the best preferred orientation model for Ritveld refinement of XRD data of uranium silicide. In: REUNIÃO DE TRABALHO SOBRE FISICA NUCLEAR NO BRASIL, 38., 8-12 de setembro, 2014, Maresias, SP. Resumo... 2014.

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  • IPEN-DOC 24836

    MOURA, TIAGO S. ; GOTO, PAULA T. ; GARCIA, RAFAEL H.L. ; SALVADOR, PABLO A.V. ; SANTOS, PAULO S. ; SOARES, JAQUELINE J.S. ; NODA, LUCIA; SAKATA, SOLANGE K. . Gamma radiation assisted reduction of graphene oxide in unoxidized environment. In: PAN AMERICAN CONGRESS OF NANOTECHNOLOGY, 1st, 27-30 de novembro, 2017, Guarujá, SP. Abstract... 2017.

    Abstract: Graphene is a honeycomb like structure of carbon atoms of sp2 hybridization, with remarkable physical and chemical properties. Perhaps, the most desirable properties of a such material is the quasi-ballistic electronic transport and its excellent thermal conductivity that make graphene an excellent alternative to build electronic devices related to silicon, for instance. However, the lack of organic functions and the strong bonds between carbons in graphene nano-sheets make them unable to undergo functionalization reactions, that is important for many applications such as gas and biochemical sensors or nanoparticles decoration. So, in order to allow the functionalization of graphene nano-sheets and make possible a variety of new applications it was developed a nanomaterial based on the oxidation and exfoliation of graphite: the graphene oxide. This new material has epoxide and hydroxyl groups in the basal planes, with carboxyl groups in the borders, improving the hydrophilic properties and potential for chemical functionalization. Graphene oxide also serves as a starting material to graphene production by reduction routes. Partial reduction of graphene oxide leads to reduced graphene, a nanomaterial that combines both proprieties of graphene and graphene oxide: an excellent electrical and thermal conductivity, high superficial area and remaining oxygen groups that allow its functionalization. In the literature is described different ways to produce reduced oxide graphene from graphene oxide, such as chemical reduction using hydrazine hydrate or NaBH4, thermal reduction using high temperatures and plasma hydrogenation. Here in it is described a sustainable process to reduce graphene oxide in sodium bisulfite solution using gamma radiation. Exfoliated Graphene oxide (1-100mg/L) with NaHSO3 under inert medium was submitted to gamma radiation. The radiation dose ranged from 50 to 500 kGy and the product was centrifuged and analyzed by X-ray diffraction (XRD), Raman and infra-red (FT-IR) spectroscopies. It was observed that depending on the dose total or partial reduction was achieved. This methodology does not produce any toxic residue.

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  • IPEN-DOC 26553

    KODAMA, YASKO ; RODRIGUES JUNIOR, ORLANDO ; GARCIA, RAFAEL H.L. ; OTUBO, LARISSA ; SANTOS, PAULO S. ; VASQUEZ, PABLO A.S. . Kinetics of Free Radicals Decay Reactions in Cellulosic Based Heritage Materials Disinfected by Gamma Radiation. In: VASQUEZ, PABLO A.S. (Ed.); NAGAI, MARIA L.E. (Coord.) INTERNATIONAL SYMPOSIUM ON GAMMA IONIZATION: TECHNOLOGY FOR PRESERVATION OF CULTURAL HERITAGE, 1st, October 25, 2019, São Paulo, SP. Abstract... São Paulo, 2019.

    Abstract: In this study, contemporary paper samples were irradiated using gamma radiation from Co-60 with different absorbed doses. The absorbed dose range was chosen taking into account the effective values to promote insect eradication, fungal disinfection and sterilization. The kinetics of decay of the cellulose free radicals induced by irradiation was analyzed using Electron Paramagnetic Resonance. Several spectra were obtained at room temperature for each applied absorbed dose immediately after irradiation as reference measurements. In order to understand the decay process of free radicals, additional spectra were obtained for different decay times up to almost 50 days after irradiation. De-noising treatment of the original obtained spectra signals were performed using wavelets. By integrating the electron paramagnetic resonance curves were calculated the area values and correlated to concentration, it is equivalent to spin concentration. Comparison of spectra was done by normalization of calculated area corresponding to cellulose spin concentration, considering the first measurement after irradiation as 100%. Further analyses and calculations were made to study the half-life and the kinetics models of the free radicals created. X-ray diffraction was carried out to identify crystalline phases and the effect of ionizing radiation on the crystalline structure of cellulose in paper. Scanning electron microscopy and Scanning Electron Microscopy Energy Dispersive Spectrometry were performed to analyze structure modifications by ionizing radiation, identifying cellulose fiber agglomeration zones and to quantify chemical elements. Likewise, samples were analyzed by infrared spectroscopy to determinate changes on the carbonyl groups. Results shown that for sterilization dose, 80% of the cellulose free radicals induced by ionizing radiation disappear in almost 40 days and for disinfection dose in 8 days. It can be concluded that if no significant modifications (side-effects) appear in the irradiated material after the radical decay time, the material will stay stable for the remaining lifetime. Proposed method using electron paramagnetic resonance results showed suitably to study the behavior of radicals on cellulosic based cultural heritage materials.

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  • IPEN-DOC 23240

    SOUSA, THAINA S. ; JACOVONE, RAYNARA M.S. ; SOARES, JAQUELINE J.S. ; RODRIGUES, DEBORA F.; SILVA, FLAVIA R. de O. ; GARCIA, RAFAEL H.L. ; FELIX, FABIANA S.; ANGNES, LUCIO; SAKATA, SOLANGE K. . Synthesis of reduced graphene oxide/nickel (rGO/NiO) nanocomposite via electron beam. In: IUPAC WORLD CHEMISTRY CONGRESS, 46th; ANNUAL MEETING OF THE BRAZILIAN CHEMICAL SOCIETY, 40th, July 07-14, 2017, São Paulo, SP. Abstract... Durham, NC, USA: International Union of Pure and Applied Chemistry, 2017.

    Abstract: Introduction Electron Beam is a flow of electrons with energy that has been used mainly for sterilization and to cross-link polymers. However, little is known about graphene based /metal nanocomposites generated by electron beam metal nanoparticles on graphene-based surfaces produces new materials with wide application in optics, electronics and catalysis 1. The aims of this work are to syntheze and characterize reduced graphene oxide/nickel oxide (rGO/NiO) via electron beam to generate conductive materials. Method, Results and discussion Dispersed graphene oxide was mixed with nickel in the complex form in water-isopropanol (1:1) solution. The mix was submitted to a dose of radiation varying between 150 and 400 KGy. The nanocomposite rGO/NiO characterization was performed by thermogravimetry analysis (TGA), X-ray diffraction (XDR), cyclic voltammetry (CV) and scanning transmission electron microscope coupled to the energy dispersive X-ray spectrometry (TEM/EDS). The TGA curve showed that the incorporation amount of Ni was 20% (w/w) and the presence of Ni was confirmed by TEM/EDS and nanoparticle size was 20 nm. The nanocomposite crystalline structure was confirmed by XRD as well as the number of layers of rGO, which are four. From the XDR pattern of the rGO/NiO, a peak corresponding to the rGO at 2θ=9.10°. These results indicate the incorporation of Ni nanoparticles to the rGO. The electrochemical characterization of rGO/NiO was performed by CV. From the voltammetric profile, current peaks were observed at 0,45 V (vs.Ag/AgCl) and correspond to 0,75 A/mol/cm2 in ascorbic acid media and pH = 5.0. According to the data obtained, it was possible to observe that the rGO/NiO showed a higher current density compared to graphene oxide at the same conditions. Conclusions The analysis demonstrated that it is possible to apply electron beam in the synthesis of rGO/NiO and as confirmed by the characterization results. It is noteworthy that the incorporation of NiO occurred at the same time the reduction of graphene oxide. The voltammetric results showed that the presence of rGO/NiO facilitated the transfer of charge during the electrooxidation of ascorbic acid. This study allowed the generation of a conductive nanocomposite that can be widely used in the electrochemical area.

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  • IPEN-DOC 29478

    GARCIA, RAFAEL H.L. ; CARNEIRO, FELIPE W. ; JACOVONE, RAYNARA M.S. ; SAKATA, SOLANGE K. ; ANGNES, LUCIO. The influence of gamma radiation doses on rGO/Ni for energy storage applications. In: INTERNATIONAL CONFERENCE ON APPLICATIONS OF RADIATION SCIENCE AND TECHNOLOGY, 2nd, August 22-26, 2022, Vienna, Austria. Abstract... Vienna, Austria: International Atomic Energy Agency (IAEA), 2022.

    Abstract: Metallic nanoparticles (MN) have been the subject of intense research in the last decades because of their high catalytic activity, associated with its large surface-to-volume ratio. However, it is difficult to obtain pure active metal nanoparticles surfaces, since its contamination and aggregation frequently result in deactivation and loss of catalytic activities. MN immobilization can minimize these effects. Thermal, mechanical, and electrical properties of reduced graphene oxide (rGO) make this material an excellent candidate for MN support for batteries and supercapacitors. The production of metallic nanoparticles on rGO surface based on gamma radiation allows less formation of residual impurities, absence of reducing agents, uniform mass production, no aggregation and low costs. Herein, we demonstrated a green and efficient one-step, gamma radiation-based method for Ni/rGO production. Graphene oxide (GO) was prepared by modified Hummers method. Ni+2 and graphene oxide reduction were performed in water/isopropanol solution (1:1) under inert medium. Samples were irradiated in the Multipurpose Gamma Irradiation Facility at CETER/IPEN/CNEN-SP, a category IV gamma irradiator by the IAEA classification, in radiations doses of 20, 40, and 80 kGy, at 10 kGy/h. From X-ray diffraction, the correlation between radiation doses and crystallite size was evaluated. For supercapacitor studies, cyclic voltammetry was carried out in a screen printed carbon electrode (SPCE) in K₄[Fe(CN)₆]. The working electrode was modified with produced rGO-Ni 80 kGy, Pt wire was used as counter and Ag/AgCl as reference electrode. Experiments were performed in KOH 1.0 M. Results showed that produced Ni/rGO has good potential to be used in electrochemical devices such as supercapacitors or batteries.

    Palavras-Chave: nanoparticles; graphene; gamma radiation; radiation doses

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  • IPEN-DOC 24851

    SOBRINHO, LUIZA F. ; GOTO, PAULA T. ; GARCIA, RAFAEL H.L. ; FRANCISCO, DANIEL; ANGNES, LUCIO; SAKATA, SOLANGE K. . The study of chemical and physical properties of Polyaniline-Graphene Oxide and Palladium Polyaniline-Graphene Oxide composites. In: PAN AMERICAN CONGRESS OF NANOTECHNOLOGY, 1st, 27-30 de novembro, 2017, Guarujá, SP. Abstract... 2017.

    Abstract: A Polyaniline (PANI)-Graphene Oxide (GO) composite was studied for the electrical activities. The GO was obtained by modified Hummers method. For the palladium nanoparticles (Pd-NPs) incorporation, it was established an environmentally friendly approach based on electron beam reduction. The chemical characterization was performed by Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetry (TG), X-ray Diffraction (XRD) and for the electrical properties Cyclic Voltammetry (CV) in alkaline medium and conductivity measurements. The FTIR spectroscopy and TG were used to obtain the composition of the synthesized materials, while XRD pattern indicated polymerization quality and the crystallization degree of the samples. The CV and conductivity measurements indicated the electrical activity of the composite. The results showed the GO amount was directly proportional to the resistivity of PANI, and when the Pd (Pd-Pani-GO) was present, the CV showed a larger current than the Pd-GO. The high electrochemical performance of the Pani-GO electrode could be due the increasing active sites for the deposition of polyaniline provided by large surface areas of graphene oxide sheets and the synergistic effect between polyaniline and GO. These results demonstrated the importance and great potential of graphene oxide in the development of high-performance conductivity system based on polyaniline.

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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.

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.