NOE GABRIEL PINHEIRO MACHADO

NOE GABRIEL PINHEIRO MACHADO

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Development of a pulsed laser deposition system suitable for radioactive thin films growth
2024 - MACHADO, N.G.P.; GENEZINI, F.A.; RAELE, M.P.
Radioactive thin films have a direct application in the development of beta-voltaic batteries. The main advantage of that kind of nuclear battery is its durability, which can range from a hundred years, depending on the half-life of the radioisotope used. In this context, Pulsed Laser Deposition (PLD) is an important tool. A relevant aspect of a system using this technique is that the main equipment is outside the chamber where the material is processed. Consequently, this feature allows the growth of radioactive thin films, as it enables the development of an arrangement where the contaminated area is controlled. In this way, the present work proposed the development of a PLD system for the growth of radioactive thin films. The PLD system was then implemented and radioactive copper targets were processed for 60 min and 120 min, resulting in radioactive thin films with an average thickness of (167.8 ± 3.7) nm and (313.5 ± 9.2) nm, respectively. Then, a study was performed about the radioactive contamination spread in the PLD system in order to prove if the filtering implemented was effective in retaining the contamination inside the vacuum chamber. Thus, it is demonstrated for the first time the feasibility of using the PLD technique in the growth of radioactive thin films, making its use possible in future studies on the development of beta-voltaic nuclear batteries.
Study on the potential of laser ablation to decontaminate radioactive waste
2022 - COSTA, PRISCILA; STIPP, WAGNER; VICENTE, ROBERTO; MACHADO, NOE G.P.; RAELE, MARCUS P.
Laser is a promising tool to decontaminate radioactive waste that is impregnated with radionuclides on its surface, the decontamination process has no chemical inputs, and the pollutants can be fixed in HEPA filters. The current study aimed to test a wide range of samples using 10 different materials and fluences ranging from 1 to 10 J/cm2.
Femtosecond production of gold nanoparticles suitable for nanobrachytherapy
2022 - MACHADO, NOE G.P.; ROSERO, WILMMER A.A.; ROSSI, WAGNER de; RAELE, MARCUS P.
The present work approaches the production of AuNPs through femtosecond laser ablation of a solid in a liquid media. Aiming at oncological applications, the stabilization of the colloidal solution was performed with non-cytotoxic material.
Desenvolvimento de um sistema baseado em deposição por laser pulsado para o crescimento de filmes finos radioativos
2019 - MACHADO, NOE G.P.
Filmes finos radioativos possuem aplicação direta no desenvolvimento de baterias betavoltaicas e alfavoltaicas. Sendo que, a principal vantagem dessas baterias nucleares é a sua durabilidade que pode variar de dezenas a até uma centena de anos, dependendo da meia-vida do radioisótopo utilizado. Nesse contexto, a Deposição por Laser Pulsado (PLD) apresenta-se como uma importante ferramenta. Um aspecto relevante de um sistema que utiliza essa técnica, é que os principais equipamentos ficam fora da câmara onde o material é processado. Logo, tal característica viabiliza o crescimento de filmes finos radioativos, pois possibilita o desenvolvimento de um arranjo onde a área contaminada, devido o processamento de um alvo radioativo, seja controlada. Dessa maneira, o presente trabalho aborda o desenvolvimento de um sistema PLD destinado ao crescimento de filmes finos radioativos. Assim, no que concerne à obtenção da câmara de vácuo e montagem das peças, o sistema foi em grande maioria projetado em um software CAD 3D. Posteriormente, as peças que estariam sujeitas à contaminação por material radioativo foram usinadas e também obtidas através de impressão 3D, sendo assim, de fácil reposição. Como no processo de ablação há a formação de material particulado, um filtro com capacidade para retenção de 99,95% de partículas com até 0,3 µm foi acoplado à câmara, para que o material radioativo não fosse disperso para o restante dos equipamentos de vácuo. O sistema foi então implementado e alvos de Cobre radioativo foram processados durante 60 min e 120 min, resultando em filmes finos radioativos com espessura média de (167,81 ± 3,67) nm e (313,47 ± 9,17) nm, respectivamente. Dessa forma, foi realizado um estudo acerca da dinâmica de contaminação do sistema, em que o filtro utilizado mostrou-se eficiente na retenção do material radioativo, possibilitando que a contaminação ficasse retida na câmara de vácuo. Portanto, demonstra-se pela primeira vez a viabilidade da utilização da técnica PLD no crescimento de filmes finos radioativos, sendo então, possível a utilização desta em estudos futuros acerca do desenvolvimento de baterias nucleares betavoltaicas e alfavoltaicas.
Evaluation of a metal-organic composite (tungsten-lignin) for attenuation of gamma radiation
2019 - SOUZA, ARMANDO C. de; CIONE, FRANCISCO C.; SILVA, ALINE C. da; GOUVEA, ADRIANA de F.G.; MACHADO, NOE G.P.; RAELE, MARCUS P.; ROSSI, JESUALDO L.
The objective of this work was to use tungsten and lignin as precursors to obtain a metal-organic composite tungsten-lignin (W-Lig) using different sintering temperatures. Tungsten is a refractory metal and it was selected for the composite since it is widely used for high-energy radiation shielding as it has an excellent absorption cross section for thermal neutrons. Lignin extracted from lignocelluloses biomass and it was selected to be the organic precursor for the composite due to its multiple applications. Analysis of the composite was performed after sintering processes, using a 3D optical surface profiler and measurement of the gamma radiation attenuation coefficient using cobalt source (Co-60). Metalorganic composites in ratios of W2.5%Lig and W5%Lig (in mass % of lignin) were used. The gradient of the attenuation coefficient differed when standard tungsten and the composites of W2.5%Lig and W5%Lig were compared. Therefore, the attenuation coefficient between unobstructed free radiation and the W5%Lig 90 ºC composite showed a gradient of about 43% in the two characteristic Co-60 energy peaks, with a sample thickness of 0.679 cm the calculated linear attenuation coefficient was 0.832 cm-1.
Study of a metal-organic composite (Wx%Lig) for the gamma radiation attenuation
2018 - SOUZA, ARMANDO C. de; ROSSI, JESUALDO L.; CIONE, FRANCISCO C.; MACHADO, NOE G.P.; SILVA, ALINE C. da; SILVA, WALLACE F. da
The objective of this work was to use tungsten and lignin as precursors to produce a metal-organic composite (Wx%Lig) using different sintering processes. Tungsten is a refractory metal and was selected for the composite due to its superior physical and mechanical properties (mechanical strength, high melting point, and excellent cross section with thermal neutrons). Its choice is also justified because it is widely used for high-energy radiation shielding. Lignin extracted from lignocellulosic biomass was selected to be the organic precursor for the composite because it has multiple applications; it is used in the production of aromatics, adhesives, and as a phenolic resin replacement. Analysis of the composite was performed after sintering processes using a Nexview 3D optical surface profiler and analyse the gamma radiation attenuation coefficient using cobalt source (Co-60). Metal-organic composites in ratios of W5%Lig and W2.5%Lig were produced after different heat treatment processes. Then, the gamma attenuation coefficients of the composite samples in these rations were analysing. The gradient of the attenuation coefficient differed when standard tungsten and the composites of W5%Lig and W2.5%Lig were compared with free source Co-60.
Boron film laser deposition by ultrashort pulses for use as neutron converter material
2019 - COSTA, PRISCILA; RAELE, MARCUS P.; MACHADO, NOE G.P.; SILVA, ANDRE F.; VIEIRA JUNIOR, NILSON D.; GENEZINI, FREDERICO A.; SAMAD, RICARDO E.
This study investigated the production of boron films by femtosecond pulsed laser deposition (PLD) to be used as converters on bulk semiconductor neutron detectors. The ablation threshold of metallic boron was determined and the film growth was studied as a function of deposition time (5–90 min) and laser pulse energy (35–530 μJ). The films were characterized by scanning electron microscopy (SEM), revealing a flaky morphology, optical profilometry, which determined the films thicknesses (from 80 nm up to 4 μm), Ion Beam Analysis (IBA) that assessed their elemental composition and X-ray diffraction (XRD), which revealed an amorphous structure. In addition, a thermal load study was performed to evaluate the heat flux onto the substrate during deposition process. Stable boron films obtained show that the femtosecond PLD process is reliable and reproducible for the fabrication of thick boron coatings.
Caracterização de ligas a base de tungstênio para atenuação da radiação gama
2018 - SOUZA, A.C.; ROSSI, J.L.; CIONE, F.C.; SILVA, W.F. da; PEREIRA, M.F.; MACHADO, N.G.P.
A ciência e tecnologia de materiais têm um grande interesse no desenvolvimento de novos compósitos de tungstênio, devido sua grande aplicabilidade na área de transporte de material nuclear, o qual representa ainda um grande problema para o Brasil, considerando que o País não possui um equipamento de fabricação nacional para esse fim. Na indústria nuclear o tungstênio possui muitas aplicações, devido às suas boas propriedades mecânicas, alto ponto de fusão e excelente seção de choque com nêutrons térmicos, sendo usado para blindagem de radiação de alta energia. Alguns dos principais elementos de liga adicionados ao tungstênio são Nb, Cr, Cu, Fe, Ni, Mo, Co, Sn, Ti e Ta, sendo os responsáveis pelas mudanças das propriedades físicas e químicas do material, principalmente sua blindagem a radiação. A finalidade deste trabalho é realizar o processamento de pós metálicos para a obtenção de uma nova liga metálica para atenuação da radiação gama, usando como matriz o tungstênio e os elementos infiltrantes cobre e níquel. O material será caracterizado utilizando as técnicas de difratometria de raios X, microscopia eletrônica de varredura (MEV), com energia dispersiva (EDS) e as medidas de atenuação da radiação gama, usando como fonte radioativa o Co-60 com picos característicos de 1173 e 1332 MeV. Os resultados mostraram que foi possível obter as novas ligas e determinar os coeficientes de atenuação da radiação gama na ordem de 16% menor, quando comparado com o elemento padrão de W. O trabalho contribuirá diretamente no processo de fabricação de um embalado que possa transportar substância com alta atividade nuclear com tecnologia nacional pertencente ao IPEN.
Analysis of temperature on microscope slide by a boron pulsed laser deposition process
2018 - SILVA, ANDRE F.; COSTA, PRISCILA; MACHADO, NOE G.P.; SAMAD, RICARDO E.; ZEZELL, DENISE M.; RAELE, MARCUS P.; ZAMATARO, CLAUDIA B.
A boron thin ¯lm can be used for neutrons conversion and in electrically charged particles and further detection. Since boron has a high evaporation temperature and the thickness of the boron layer needs to have few microns, pulsed laser deposition also known as PLD can be used. When producing thin ¯lms with the PLD technique, the target absorbs energy promoting the material ablation creating a plasma plume that deposits material on a substrate, thus creating a thin ¯lm. Since all the deposition occurs in a vacuum chamber, the residual heat of the plasma that condensate at the substrate can build up, thus potentially source of concern if the substrate sensitive to temperature somehow. This work reports the analysis of the variation of temperature in a microscope slide (substrate) as a function of the energy of femtosecond laser pulses. For measuring the substrate temperature a type-K thermocouple was used together with associated electronics. The thermocouple was ¯xed to the back of substrate with thermal grease for vacuum and connected to the microchip using a feed through in the vacuum chamber. Was detected the increase of the substrate+¯lm starting at 6oC from initial temperature (room) for the minimal laser energy 100 microjoules (25 femtoseconds).
Femtosecond pulsed laser deposition of a boron thin film aiming at the development of a low-cost neutron detector
2018 - COSTA, PRISCILA; RAELE, MARCUS P.; SAMAD, RICARDO E.; MACHADO, NOE G.P.; VIEIRA JUNIOR, NILSON D.; GENEZINI, FREDERICO A.
Boron thin films were produced using femtosecond pulsed laser deposition aiming at the development of a neutron detector. As neutrons have no charge, in order to detect this particle converter materials are applied, promoting nuclear reactions that result in the emission of charged particles, allowing the neutrons presence to be indirectly inferred. Among the possible conversion materials, 10B has a considerable cross section for thermal neutrons and accessible cost. Furthermore, the nuclear reaction produces easily detectable alpha particles, making it a rational option to develop a low cost and portable neutron detector. The boron ablation threshold fluence has been measured by the Diagonal Scan (Dscan) technique that resulted in the minimum laser energy value of 17.7 (6) μJ and fluence of 5.63(19) J/cm2. Boron deposition was performed varying the pulse energy and deposition duration. The growth rate, morphological and physical aspects of the boron pulsed laser deposition were characterized by a Scanning Electron Microscope and an optical profilometer. The films surfaces have a flaky aspect with eventual droplets which had decayed overtime to a more smooth surface. The studied parameters allowed producing a boron coating with the optimal thickness in order to minimize self-absorption effect in the film, thus increasing efficiency.