NOE GABRIEL PINHEIRO MACHADO

NOE GABRIEL PINHEIRO MACHADO

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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.
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.
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.