ARMANDO CIRILO DE SOUZA
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Artigo IPEN-doc 28172 Microstructural evolution of the refractory WCuNi metallic alloy2021 - SOUZA, ARMANDO C.; ROSSI, JESUALDO L.; TSAKIROPOULOS, PANOS; ARISTONE, FLAVIOScience and technology of materials are widely interested in the development of new alloys involving tungsten due to its large applicability to the domain of nuclear material transportation. Tungsten is a refractory material and it has many applications in the nuclear industry due to its mechanical properties and excellent cross-section for thermal neutrons, being widely used for shielding of high-energy radiation. Some of the main elements added to tungsten forming alloys are Nb, Cr, Cu, Fe, Ni, Mo, Co, Sn, Ti, and Ta, which are responsible for modifications of the physical and chemical properties of the resulting alloy, interfering on the attenuation of gamma radiation. The main goal of this paper is to present a refractory alloy based on tungsten with embedded infiltrating elements like copper (Cu) and nickel (Ni) and characterize the microstructural evolution of different sintering process during its formation. Such a refractory alloy is submitted to the following characterization process: X-rays diffractometry, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy, and energy dispersive spectroscopy. The diffractometry exhibit typical standard results for the precursor powders: W, Cu, and Ni demonstrating high degrees of purity accordingly to the crystallographic determined parameters. The TGA for the powder W demonstrated thermal stability until 360 ºC, after an increase of mass due to the process of oxidation. The DSC analyze present two endothermal processes at temperatures 350 °C and 450 °C. The microstructural evolution of WCuNi samples presents the absence of oxidation, homogeneous morphology and stability of the binary phase α–β (W and CuNi respectively) for different sintering. These results shall be taken into consideration for future works, particularly on the study of shielding and gamma radiation attenuation.Artigo IPEN-doc 23717 A Study of Production of Tungsten Copper Alloy by Powder Metallurgy, Applied to Radioactive Shielding of Transport Equipment for Pharmaceutical Products2015 - CIONE, FRANCISCO C.; SOUZA, ARMANDO C. de; SENE, FRANK F.; RIZZUTTO, MARCIA de A.; ROSSI, JESUALDO L.Safety is of paramount importance for the storage and transportation of radiopharmaceutical products, being directly dependent on the radiation shielding material used in specific devices. The focus of present work, part of a larger project, is to minimize the use of harmful materials, as lead and depleted uranium, in such devices construction. The radioactive energy reduction varies according to density of material used as shielding. Because Tungsten has a high density and, implicitly, good shielding properties without to be harmful, but has poor workability, researches were focused on Tungsten - copper heavy alloys. The objective of the performed research was the optimization of alloy composition in order to achieve the best linear absorption coefficient. The studied compositions were 15, 20 and 25 wt.% copper. The linear absorption coefficient was similar either for the green and sintered compacts, thus the porosity level did not have measurable effect on the radiation attenuation.