Departamento de Física
URI permanente desta comunidadehttps://repositorio.fei.edu.br/handle/FEI/785
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3 resultados
Resultados da Pesquisa
- Using TRIM-SRIM code simulations to determine defect density produced in HOPG irradiated with high energy heavy ions(2022) AVANZI, L. H.; AGUIAR, V. A. P.; COSTA, K. M.; SANTARELLI, T. O.; MEDINA, N. H.; OLIVEIRA, J. R. B.; CAPPUZZELLO, F.; IAZZI, F.; CAPIROSSI, V.; PINNA, F.; CAVALLARO, M.; Marcilei Aparecida Guazzelli© 2022 Institute of Physics Publishing. All rights reserved.This work is part of the NUMEN Project (NUclear Matrix Elements for Neutrinoless double beta decay), which, among other goals, aims to measure cross-section of double charge exchange reactions (DCE). In the experiments to be carried out at the Laboratori Nazionali del Sud, in Catania, Italy, a target deposited on a carefully chosen backing (substrate) will be irradiated with a high energy ion beam and, importantly, neither the target nor the substrate will be allowed to overheat as this would affect their structures and its properties, which are special for the experiment. Within this context, highly oriented pyrolytic graphite (HOPG) was chosen as a substrate for the deposition of target elements that will be irradiated by ions such as 12C, 18O and 20Ne, with energies ranging from 15 MeV/u to 60 MeV/u. HOPG is considered a semimetal structured in layers, being composed of a stack of graphene sheets with a small and very subtle disorientation (less than 1°), which makes it to approach to a single crystal. With its specific flat hexagonal molecular structure, consisting only of carbon atoms, HOPG has good thermal conductivity in these sheets, making it an excellent candidate as a heat sink. However, for the HOPG to act with thermal energy dissipation functionality during the experiments proposed by the NUMEN project, it is necessary to verify whether possible changes caused by exposure to the radiation beam have a direct or indirect influence on its mechanical and thermal properties. Regarding the thermal conductivity, vacancies produced during irradiation is one of the factors that considerably decrease such property. As the production of vacancies during irradiation is one of the factors that considerably decrease thermal conductivity, in this work it was used the SRIM/TRIM code simulations to investigate the mechanisms of vacancy production in the target plus HOPG backing system. In the simulations, it was considered different types and doses of incident ion beams as well as different target thickness. From the results it was possible to estimated how long a target-HOPG system can be irradiated before the HOPG high heat conductivity property is lost.
- Bridging experiment and theory: Morphology, optical, electronic, and magnetic properties of MnWO4(2022-01-05) ASSIS, M.; TELO, A. C. M.; ABUD, F. S. A.; NEGRE, P.; RIBEIRO, L. K.; RIBEIRO,R. A. P.; S. H. Masunaga; LIMA, A. E. B.; LUZ JUNIOR, G. E.; JARDIM, R. F.; SILVA, A. B. F.; ANDRES, J.; LONGO, E.© 2022 The AuthorsManganese tungstate (MnWO4) compounds have gathered tremendous interest in the research community due to their wide range of applications. Herein, we show a comprehensive experimental, theoretical and computational study aimed at providing an in-depth understanding of the morphology as well as optical, electronic and magnetic properties of monoclinic MnWO4. In order to evaluate such properties together with the geometry and vibrational frequencies of these materials, first-principles calculations were used at the DFT level. The synthesis and analysis of these properties were then featured by (i) the composition, geometry, and electronic and magnetic structure of the exposed surfaces at the morphology based on the different numbers of unsaturated superficial Mn and W cations (local coordination, i.e., clusters) of each surface, and (ii) the determination of the energy profiles associated with the transformation process between different morphologies. Additionally, we used a combination of theories and simulations to link experimental results to a prediction of the corresponding properties. These system-specific findings at the atomic level provide a powerful insight for understanding and tuning optical/electronic/magnetic properties of MnWO4-based materials.
- Computational Simulation of Duplex Stainless Steel Continuous Cooling Transformation Curves Using DICTRA®(2022-01-05) ANDRADE R. A.; Rodrigo Magnabosco© 2022 Universidade Federal de Sao Carlos. All rights reserved.Despite of their excellent combination of high mechanical strength, toughness and corrosion resistance, duplex stainless steels (DSS) are susceptible to sigma phase formation, negatively affecting their superior properties. Sigma formation continuous cooling transformation (CCT) diagrams can be a useful tool to avoid sigma formation during cooling from solution treatment temperatures; however, non-isothermal information about sigma formation in DSS are scarce in literature. This work presents a methodology to simulate CCT diagrams in DICTRA® software, showing excellent adherence to literature data. The methodology here presented was also able to describe sigma phase formation behaviour for different DSS compositions.