NOE GABRIEL PINHEIRO MACHADO
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Artigo IPEN-doc 30367 Development of a pulsed laser deposition system suitable for radioactive thin films growth2024 - 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.Artigo IPEN-doc 26440 Evaluation of a metal-organic composite (tungsten-lignin) for attenuation of gamma radiation2019 - 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.Artigo IPEN-doc 25869 Study of a metal-organic composite (Wx%Lig) for the gamma radiation attenuation2018 - SOUZA, ARMANDO C. de; ROSSI, JESUALDO L.; CIONE, FRANCISCO C.; MACHADO, NOE G.P.; SILVA, ALINE C. da; SILVA, WALLACE F. daThe 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.Artigo IPEN-doc 25742 Boron film laser deposition by ultrashort pulses for use as neutron converter material2019 - 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.