Navegando por Palavras-chave "X-Ray Diffraction"

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    Dosimetria ambiental de areia monazítica das praias do litoral norte de São Paulo
    (Universidade Federal de São Paulo, 2021-02-23) Teissiere, Luigi Leite [UNIFESP]; Tatumi, Sonia Hatsue [UNIFESP]; http://lattes.cnpq.br/5410340106554020; http://lattes.cnpq.br/2287413815393341; Universidade Federal de São Paulo (UNIFESP)
    Algumas praias do litoral norte de São Paulo apresentam areias monazíticas, que são areias que contêm terras raras e isótopos radioativos, deste modo, é possível afirmar que emite radiação gama. Quando o ser humano é exposto a doses de radiação, pode resultar em alguns danos celulares, podendo evoluir para um câncer. O objetivo deste trabalho é estabelecer uma análise da dose de radiação gama emitida pela areia e comparar com os limites estabelecidos pelos órgãos reguladores. Foi utilizado o Detector de Germânio Puro de Camberra e a Rigaku MiniFlex 300 para as análises de dose anual das areias colhidas e as suas estruturas cristalinas. As doses das amostras da Praia da Mococa foram as que mais se aproximaram do limite natural de 10 mSv/ano estabelecido pela CNEN. E também foram encontradas estruturas de terras raras com o método de Difração de Raios X.
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    Processamento Das Ligas De Alta Entropia Crcufenizn, Crcufe(Nb)Xnizn (X = 0,5 ; 1) Por Moagem De Alta Energia E Sinterização Spark Plasma
    (Universidade Federal de São Paulo (UNIFESP), 2017-06-21) Bepe, Andre Mello [UNIFESP]; Cardoso, Kátia Regina [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    High-entropy alloys (HEAs) are designed based on selecting elements that will form solid solution phases when combined at near-equiatomic concentrations (5 – 35 at.%). In this study, the selected alloys CrCuFeNiZn, CrCuFeNb0.5NiZn and CrCuFeNbNiZn were processed by hours 40 hours of Mechanical Alloying (M.A) and subsequently consolidated by SPS at 850o C and 50 MPa of uniaxial pressure. The microstructural analysis of both the powder and the sintered alloy samples was carried out using X ray diffractrometry (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). Vickers microhardness testing was conducted to measure the hardness of the produced alloys. The microstructures of the as-milled alloys consist of a disordered face centered cubic (FCC) solid solution phase and a minor percentage of disordered body centered cubic solid solution (BCC) phase. Nb additions were responsible for reducing considerably the crystallite size and inducing partial amorphization in the CrCuFeNb0.5NiZn and CrCuFeNbNiZn alloys. After SPS, both major FCC phase and BCC structures are still present and a new Cu-Ni-Zn rich disordered FCC phase was formed. The formation of the Laves phase (Fe2Nb) in CrCuFeNb0,5NiZn and CrCuFeNbNiZn was observed. Vickers microhardness analysis indicate that the powder samples of CrCuFeNiZn alloy has an average hardness of 533 ± 10 HV while Nb addition further increased the hardness of CrCuFeNb0,5NiZn and CrCuFeNbNiZn alloys to 606 ± 17 HV and 655 ± 18 HV. The sintered alloys present hardness values of 524 ± 9 HV, 602 ± 11 HV, 672 ± 16 HV, respectively. The alloys produced in this study have complex microstructures and high hardness which offers the possibility for them to be a target for future investigations aiming structural applications.