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Fabrication of Metal Matrix Composite by Laser Metal Deposition—A New Process Approach by Direct Dry Injection of Nanopowders

by Briac Lanfant, Florian Bär, Antaryami Mohanta and Marc Leparoux

Materials 2019, 12(21), 3584; https://doi.org/10.3390/ma12213584 - 31 Oct 2019

Cited by 7 | Viewed by 5973

Abstract

Laser Metal Deposition (LMD) offers new perspectives for the fabrication of metal matrix nanocomposites (MMnCs). Current methods to produce MMnCs by LMD systematically involve the premixing of the nanopowders and the micropowders or require in-situ strategies, thereby restricting the possibilities to adjust the nature, content and location of the nano-reinforcement during printing. The objective of this study is to overcome such restrictions and propose a new process approach by direct injection of nanoparticles into a metallic matrix. Alumina (n-Al₂O₃) nanoparticles were introduced into a titanium matrix by using two different direct dry injection modes in order to locally increase the hardness. Energy dispersive X-ray spectroscopy (EDS) analyses validate the successful incorporation of the n-Al₂O₃ at chosen locations. Optical and high resolution transmission electron microscopic (HR-TEM) observations as well as X-ray diffraction (XRD) analyses indicate that n-Al₂O₃ powders are partly or totally dissolved into the Ti melted pool leading to the in-situ formation of a composite consisting of fine α₂ lamellar microstructure within a Ti matrix and a solid solution with oxygen. Mechanical tests show a significant increase in hardness with the increase of injected n-Al₂O₃ amount. A maximum of 620 HV was measured that is almost 4 times higher than the pure LMD-printed Ti structure. Full article

(This article belongs to the Special Issue Metal Matrix Composites: Experimental and Simulation)

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15 pages, 5144 KB

Open AccessArticle

Thermal Plasma Synthesis of Crystalline Gallium Nitride Nanopowder from Gallium Nitrate Hydrate and Melamine

by Tae-Hee Kim, Sooseok Choi and Dong-Wha Park

Nanomaterials 2016, 6(3), 38; https://doi.org/10.3390/nano6030038 - 24 Feb 2016

Cited by 15 | Viewed by 10686

Abstract

Gallium nitride (GaN) nanopowder used as a blue fluorescent material was synthesized by using a direct current (DC) non-transferred arc plasma. Gallium nitrate hydrate (Ga(NO₃)₃∙xH₂O) was used as a raw material and NH₃ gas was used as a nitridation source. Additionally, melamine (C₃H₆N₆) powder was injected into the plasma flame to prevent the oxidation of gallium to gallium oxide (Ga₂O₃). Argon thermal plasma was applied to synthesize GaN nanopowder. The synthesized GaN nanopowder by thermal plasma has low crystallinity and purity. It was improved to relatively high crystallinity and purity by annealing. The crystallinity is enhanced by the thermal treatment and the purity was increased by the elimination of residual C₃H₆N₆. The combined process of thermal plasma and annealing was appropriate for synthesizing crystalline GaN nanopowder. The annealing process after the plasma synthesis of GaN nanopowder eliminated residual contamination and enhanced the crystallinity of GaN nanopowder. As a result, crystalline GaN nanopowder which has an average particle size of 30 nm was synthesized by the combination of thermal plasma treatment and annealing. Full article

(This article belongs to the Special Issue Plasma Nanoengineering and Nanofabrication)

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