Synthesis of MWCNT/Inconel 718 composite powder through mild surface functionalization and High-Energy Ball Milling for subsequent use in additive manufacturing of MMC parts--颗粒学报PARTICUOLOGY

Synthesis of MWCNT/Inconel 718 composite powder through mild surface functionalization and High-Energy Ball Milling for subsequent use in additive manufacturing of MMC parts

Prasenjit Patra^{a b}, Saikat Nandi^{a b}, Saurav Misra^b, Partha Saha^b *, Pranab K. Dan ^a

a Rajendra Mishra School of Engineering Entrepreneurship, Indian Institute of Technology Kharagpur, India
b Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, India

10.1016/j.partic.2025.12.017

Volume 109, February 2026, Pages 99-116

Received 16 October 2025, Revised 28 November 2025, Accepted 19 December 2025, Available online 2 January 2026, Version of Record 7 January 2026.

E-mail: psaha@mech.iitkgp.ac.in

Highlights

• Explored the role of mild functionalization in reduction of agglomeration in MWCNTs.

• Mild functionalization done by stirring in H₂SO₄ and HNO₃, then sonication in H₂O₂.

• Overoxidation leading to fragmented tubes and graphene nanosheets.

• Up to 2 wt% of uniformly dispersed MWCNT/Inconel 718 composite powder is prepared.

• Minimal in-flight segregation after passing through the LDED experimental setup.

Abstract

This study presents a systematic methodology for producing multi-walled carbon nanotubes (MWCNTs)/Inconel 718 composite powder, especially for the Laser Directed Energy Deposition (LDED) process. This approach integrates mild oxidative functionalization of MWCNTs to reduce agglomerations and High-Energy Ball Milling (HEBM) to enhance dispersion over the Inconel 718 powder. The MWCNTs were functionalized through a two-step chemical treatment: (1) magnetic stirring in a 3:1 H₂SO₄ and HNO₃ solution, using two distinct acid concentrations (3 M and 8 M), followed by (2) an ultrasonic bath in H₂O₂ solution. Structural defects were characterized using Raman spectroscopy (RS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM), while X-ray photoelectron spectroscopy (XPS) quantified the amount of oxygen-containing functional groups. Among the six functionalization processes, the treatment condition involving 4 h of magnetic stirring, then 2 h in the sonication bath, emerged as optimal, yielding a relatively high functional group attachment (11.47 %) with lower surface defects and without compromising uniformity in mixing. The FESEM analysis of the functionalized MWCNTs (up to 2 wt%)/Inconel 718 composite powder, collected from the LDED machine bed, confirmed uniform dispersion, validating the functionalization strategy. Although developed for LDED, this strategy is also suitable for MMC production processes that use powder as feedstock.

Graphical abstract

Keywords

Multi-walled carbon nanotubes (MWCNTs); Inconel 718; Laser directed energy deposition (LDED); Surface functionalization; X-ray photoelectron spectroscopy (XPS)

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