Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell

Additive manufacturing (AM), for example, directed energy deposition (DED), may allow the processing of self-healing metal–matrix composites (SHMMCs). The sealing of cracks in these SHMMCs would be achieved via the melting of micro-encapsulated low melting point particulates (LMPPs), incorporated in...

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Autores principales:	David Svetlizky, Noam Eliaz
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	electroless deposition boehmite alumina core–shell powder thermal barrier coating diffusion barrier Engineering (General). Civil engineering (General) TA1-2040
Acceso en línea:	https://doaj.org/article/1ce5f53cb64e41d5887956b08c3556b3
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spelling	oai:doaj.org-article:1ce5f53cb64e41d5887956b08c3556b32021-11-25T17:16:45ZSol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell10.3390/coatings111113892079-6412https://doaj.org/article/1ce5f53cb64e41d5887956b08c3556b32021-11-01T00:00:00Zhttps://www.mdpi.com/2079-6412/11/11/1389https://doaj.org/toc/2079-6412Additive manufacturing (AM), for example, directed energy deposition (DED), may allow the processing of self-healing metal–matrix composites (SHMMCs). The sealing of cracks in these SHMMCs would be achieved via the melting of micro-encapsulated low melting point particulates (LMPPs), incorporated into the material during AM, by heat treatment of the part during service. Zn-Al alloys are good candidates to serve as LMPPs, for example, when the matrix of the MMC is made of an aluminum alloy. However, such powders should first be encapsulated by a thermal and diffusion barrier. Here, we propose a sol–gel process for encapsulation of a custom-made ZA-8 (Zn92Al8, wt.%) core powder in a ceramic alumina (Al<sub>2</sub>O<sub>3</sub>) shell. We first modify the surface of the ZA-8 powder with (12-phosphonododecyl)phosphonic acid (Di-PA) hydrophobic self-assembled monolayer (SAM) in order to prevent extensive hydrogen evolution and formation of non-uniform and porous oxide/hydroxide surface layers during the sol–gel process. Calcination for 1 h at 500 °C is found to be insufficient for complete boehmite-to-γ(Al<sub>2</sub>O<sub>3</sub>) phase transformation. Thermal stability tests in an air-atmosphere furnace at 600 °C for 1 h result in melting, distortion, and sintering into a brittle sponge (aggregate) of the as-atomized powder. In contrast, the core/shell powder is not sintered and preserves its spherical morphology, with no apparent “leaks” of the ZA-8 core alloy out of the ceramic encapsulation.David SvetlizkyNoam EliazMDPI AGarticleelectroless depositionboehmitealuminacore–shell powderthermal barrier coatingdiffusion barrierEngineering (General). Civil engineering (General)TA1-2040ENCoatings, Vol 11, Iss 1389, p 1389 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	electroless deposition boehmite alumina core–shell powder thermal barrier coating diffusion barrier Engineering (General). Civil engineering (General) TA1-2040
spellingShingle	electroless deposition boehmite alumina core–shell powder thermal barrier coating diffusion barrier Engineering (General). Civil engineering (General) TA1-2040 David Svetlizky Noam Eliaz Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell
description	Additive manufacturing (AM), for example, directed energy deposition (DED), may allow the processing of self-healing metal–matrix composites (SHMMCs). The sealing of cracks in these SHMMCs would be achieved via the melting of micro-encapsulated low melting point particulates (LMPPs), incorporated into the material during AM, by heat treatment of the part during service. Zn-Al alloys are good candidates to serve as LMPPs, for example, when the matrix of the MMC is made of an aluminum alloy. However, such powders should first be encapsulated by a thermal and diffusion barrier. Here, we propose a sol–gel process for encapsulation of a custom-made ZA-8 (Zn92Al8, wt.%) core powder in a ceramic alumina (Al<sub>2</sub>O<sub>3</sub>) shell. We first modify the surface of the ZA-8 powder with (12-phosphonododecyl)phosphonic acid (Di-PA) hydrophobic self-assembled monolayer (SAM) in order to prevent extensive hydrogen evolution and formation of non-uniform and porous oxide/hydroxide surface layers during the sol–gel process. Calcination for 1 h at 500 °C is found to be insufficient for complete boehmite-to-γ(Al<sub>2</sub>O<sub>3</sub>) phase transformation. Thermal stability tests in an air-atmosphere furnace at 600 °C for 1 h result in melting, distortion, and sintering into a brittle sponge (aggregate) of the as-atomized powder. In contrast, the core/shell powder is not sintered and preserves its spherical morphology, with no apparent “leaks” of the ZA-8 core alloy out of the ceramic encapsulation.
format	article
author	David Svetlizky Noam Eliaz
author_facet	David Svetlizky Noam Eliaz
author_sort	David Svetlizky
title	Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell
title_short	Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell
title_full	Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell
title_fullStr	Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell
title_full_unstemmed	Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell
title_sort	sol–gel encapsulation of znal alloy powder with alumina shell
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/1ce5f53cb64e41d5887956b08c3556b3
work_keys_str_mv	AT davidsvetlizky solgelencapsulationofznalalloypowderwithaluminashell AT noameliaz solgelencapsulationofznalalloypowderwithaluminashell
_version_	1718412516319559680

Sol–Gel Encapsulation of ZnAl Alloy Powder with Alumina Shell

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