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- 저자 : E. A. S. Marques (검색결과 3 건)
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R. Beygi,R. Carbas,A. Queiros,E. A. S. Marques,R. Shi,L. F. M. da Silva 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.8
Steel (St) and aluminum (Al) have a high affinity to each other and form intermetallic compounds (IMCs) when bonded byfriction stir welding (FSW). Understanding the effect of alloying elements of steel on the formation of IMCs will help todesign joints in which the formation of IMCs is controlled. In this study, two kinds of steel, carbon steel (CS) and austeniticstainless steel (SS) with 3 mm thickness, were selected to be welded to aluminum by FSW under similar conditions. Theeffect of the rotation speed of the FSW tool was also examined in the range of 850–1300 RPM. The morphology, thickness,and composition of IMCs in the interfaces were studied by various characterization techniques. It was observed that theIMC layers in the SS/Al joints were much thinner than the ones in CS/Al joints (0.1–0.7 μm in SS/Al and 2–6 μm in CS/Al). Moreover, the thickness of IMC layer in CS/Al joints increased with increasing the rotation speed while in SS/Al jointsit began to decline by exceeding a certain rotation speed. In order to explain these differences, diffusion-based equationswere used to calculate the interdiffusion coefficients in both SS/Al and CS/Al couples. It was found that the interdiffusioncoefficient in SS/Al was lower than CS/Al. This was attributed to the alloying elements of SS such as Ni and Cr which candiffuse to IMC layer and hinder the growth rate of IMCs. It was also observed that some form of liquation occurred in SS/Al joints at high rotation speed of FSW due to the formation of a low-melting multielement compound of Al–Fe–Cr–Ni. The decline of IMC thickness in SS/Al joints at high rotation speed was attributed to this multielement compound whichwas melted during FSW and reduced the nucleation rate of Al–Fe IMCs. Finally, the fracture of the specimens and the effectof IMC formation on the joint establishment were elaborated. It was concluded that the alloying elements of steel have abeneficial effect on controlling the growth of IMCs.
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Lee, S.E.,Chang, H.J.,Rizvi, A.,Hadamitzky, M.,Kim, Y.J.,Conte, E.,Andreini, D.,Pontone, G.,Volpato, V.,Budoff, M.J.,Gottlieb, I.,Lee, B.K.,Chun, E.J.,Cademartiri, F.,Maffei, E.,Marques, H.,Leipsic, J C. V. Mosby Co 2016 American Heart Journal Vol.182 No.-
<P>Background The natural history of coronary artery disease (CAD) in patients with low-to-intermediate risk is not well characterized. Although earlier invasive serial studies have documented the progression of atherosclerotic burden, most were focused on high-risk patients only. The PARADIGM registry is a large, prospective, multinational dynamic observational registry of patients undergoing serial coronary computed tomographic angiography (CCTA). The primary aim of PARADIGM is to characterize the natural history of CAD in relation to clinical and laboratory data. Design The PARADIGM registry (ClinicalTrials. gov NCT02803411) comprises >= 2,000 consecutive patients across 9 cluster sites in 7 countries. PARADIGM sites were chosen on the basis of adequate CCTA volume, site CCTA proficiency, local demographic characteristics, and medical facilities to ensure a broad-based sample of patients. Patients referred for clinically indicated CCTA will be followed up and enrolled if they had a second CCTA scan. Patients will also be followed up beyond serial CCTA performance to identify adverse CAD events that include cardiac and noncardiac death, myocardial infarction, unstable angina, target vessel revascularization, and CAD-related hospitalization. Summary The results derived from the PARADIGM registry are anticipated to add incremental insight into the changes in CCTA findings in accordance with the progression or regression of CAD that confer prognostic value beyond demographic and clinical characteristics.</P>
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Room temperature photoluminescence of BCT prepared by Complex Polymerization Method
F.V. Motta,A.P.A. Marques,J.W.M. Espinosa,P.S. Pizani,E. Longo,J.A. Varela 한국물리학회 2010 Current Applied Physics Vol.10 No.1
It was used the Complex Polymerization Method to synthesize barium calcium titanate powders (BCT). Crystalline Ba0.8Ca0.2TiO3 perovskite-type phase could be identified by X-ray diffraction and confirmed by Raman spectroscopy in the powders heat treated at 600 C. Inherent defects, linked to structural disorder,facilitate the photoluminescence emission. The photoluminescent emission peak maximum was around of 533 nm (2.33 eV) for the Ba0.8Ca0.2TiO3. The photoluminescence process and the band emission energy photon showed dependence of both the structural order–disorder and the thermal treatment history. The results revealed that Ba0.8Ca0.2TiO3 (BCT20) is a highly promising candidate material for optical applications.
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