Yanshan University

About: Yanshan University is a education organization based out in Qinhuangdao, China. It is known for research contribution in the topics: Microstructure & Control theory. The organization has 19544 authors who have published 16904 publications receiving 184378 citations. The organization is also known as: Yānshān dàxué.

Pore formation and evolution in wire + arc additively manufactured 2319 Al alloy

Abstract: Given its detrimental influence on mechanical properties, porosity defect is a major problem for wire + arc additively manufactured (WAAM) Al components. We performed X-ray computed tomography, optical microscopy, and scanning electron microscopy to observe the spatial distribution, size, and shape of micropores and reveal their formation and evolution mechanisms during the deposition and heat treatment of the WAAM 2319 Al alloys. Key findings demonstrated that thehydrogenmicropores and solidification microvoids existed in as-deposited alloys. The amounts and morphologies of hydrogen micropores and solidification microvoids varied from the top, middle, and bottom of the wall sample because of the distinct microstructure and second-phase distribution in each section. After the heat treatment, a significant variation in micropores involving three main evolution mechanisms, namely, hydrogen micropore precipitation, phase particle dissolution, and micropore growth, was observed. The hydrogen content analysis verifies that the evolution of micropores from each section of the wall was dominated by different mechanisms. Results of this research may provide a solid foundation for the safe application of WAAM Al alloy structures.

Ultrafine FePd Nanoalloys Decorated Multiwalled Cabon Nanotubes toward Enhanced Ethanol Oxidation Reaction.

Abstract: Ultrafine iron-palladium (FePd) nanoalloys deposited on γ-Fe2O3, FePd–Fe2O3, further anchored on carboxyl multiwalled carbon nanotubes (MWNTs–COOH), FePd–Fe2O3/MWNTs, were successfully synthesized by a facile one-pot solution based method as thermally decomposing palladium acetylacetonate (Pd(acac)2) and iron pentacarbonyl (Fe(CO)5) in a refluxing dimethylformamide solution in the presence of MWNTs–COOH. A 3.65 fold increase of peak current density was observed in cyclic voltammetry (CV) for ethanol oxidation reaction (EOR) compared with that of Pd/MWNTs after normalizing to Pd mass. The greatly enhanced tolerance stability toward poisoning species and largely reduced charge transfer resistance were also obtained in chronoamperometry and electrochemical impedance spectroscopy due to the downward shifted d-band center of FePd alloy, easily formed oxygen containing species on Fe2O3, and the stabilizing role of the MWNTs.