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Open AccessArticle

The Effect of Processing Parameters on the Formation and Properties of Al/Ni Core-Shell Pigments via a Galvanic Displacement Method

1
Key Laboratory of Fluid and Power Machinery of Ministry of Education, School of Materials Science and Engineering, Xihua University, Chengdu 610039, China
2
National Engineering Research Center of Electromagnetic Radiation Control Materials, UESTC, Chengdu 610054, China
*
Author to whom correspondence should be addressed.
Coatings 2018, 8(6), 200; https://doi.org/10.3390/coatings8060200
Received: 18 April 2018 / Revised: 18 May 2018 / Accepted: 22 May 2018 / Published: 24 May 2018
(This article belongs to the Special Issue Binders, Pigments, Dyes and Additives)
Al/Ni bimetallic core-shell pigments with flake Al particle as core and metallic Ni as shell were synthesized via a galvanic displacement method and studied with X-ray diffraction, scanning electron micrograph (SEM), specific surface area analysis (BET), thermogravimetry-differential thermalanalysis (TG/DSC), and visible-near infrared-infrared reflectance spectroscopy. The influence of reactant ratio (Al:Ni2+) and order of addition on phase structure, surface morphology, optical properties, and high temperature oxidation resistance properties were studied systematically. The results show that the local concentration of Ni2+ at solid-liquid interfaces can be effectively modulated by adjusting the reactant ratio and order of addition. A high local concentration of Ni2+ improves the rate of displacement reaction resulting in more metallic Ni on the surface of the flake Al powders. This increases the relative content of Ni in the shell. The change of displacement reaction rate also leads to a different surface morphology and roughness of the Ni shell. The thick and rough Ni shell has a strong absorption extinction due to the intense light scattering and absorption-this substantially reduces the spectral reflectance of the flake Al core. Infrared reflectance in particular is influenced by light scattering and absorption of the rough surface. In addition, the Ni shell can enhance the high temperature oxidation resistance of the Al core by preventing contact between the metallic Al substrate and oxygen. The oxidation resistance is also associated with the processing parameters of the galvanic displacement reaction. View Full-Text
Keywords: flake aluminum; core-shell structure; galvanic displacement; nickel shell flake aluminum; core-shell structure; galvanic displacement; nickel shell
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Yuan, L.; Zhou, M.; Wang, C.; Zhang, Q.; Weng, X.; Deng, L. The Effect of Processing Parameters on the Formation and Properties of Al/Ni Core-Shell Pigments via a Galvanic Displacement Method. Coatings 2018, 8, 200.

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Coatings, EISSN 2079-6412, Published by MDPI AG
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