Best Paper Award for Varatharaja Nallathambi

Tuning 3D-printed magnets for electrification

January 07, 2026

At a glance

Award: CENIDE Best Paper Award 2025 for Varatharaja Nallathambi
Research topic: Tuning the coercivity of 3D-printed Nd-Fe-B permanent magnets by modifying the powder feedstock
Key finding: Adding 1 wt% silver nanoparticles increases coercivity by up to 17% without loss of remanence or additional post-processing
Relevance: Resource-efficient permanent magnets for electric motors and electrification technologies
Approach: Additive manufacturing combined with targeted microstructural design

Four persons standing next to each other. Two of them are holding certificates in their hands. — Varatharaja Nallathambi (third person from the left), PhD researcher at the Max Planck Institute for Sustainable Materials and at the University of Duisburg-Essen, and Philipp Gabriel (second from the left), PhD researcher at the University of Duisburg-Essen, were awarded with the CENIDE Best Paper Award 2025 in the category “Magnetic Materials”.

© CENIDE, University Duisburg-Essen

Varatharaja Nallathambi (third person from the left), PhD researcher at the Max Planck Institute for Sustainable Materials and at the University of Duisburg-Essen, and Philipp Gabriel (second from the left), PhD researcher at the University of Duisburg-Essen, were awarded with the CENIDE Best Paper Award 2025 in the category “Magnetic Materials”.

© CENIDE, University Duisburg-Essen

The Center for Nano-Integration Duisburg-Essen (CENIDE) has awarded Varatharaja Nallathambi, PhD researcher at the Max Planck Institute for Sustainable Materials and at the University of Duisburg-Essen, with a CENIDE Best Paper Award 2025 in the category “Magnetic Materials”. The award recognises his publication in the journal of Advanced Science that demonstrates how the magnetic properties of additively manufactured permanent magnets can be enhanced by surface nano-modification of the powder feedstock. Nallathambi shares the award with Philipp Gabriel, PhD researcher at the University of Duisburg-Essen, who is a co-leading author of the study.

Permanent magnets for electrification

Permanent magnets are a key component in electric motors and power generation systems, rendering them essential to the ongoing electrification of mobility, energy infrastructure, and industrial sectors. Today’s highest-performing permanent magnets are predominantly based on rare-earth elements, such as neodymium, as in Nd–Fe–B magnets. With the rapidly growing demand for electric motors and thus magnetic materials, reducing rare-earth material use while maintaining or improving the performance of existing magnets has become a central challenge.

In this context, additive manufacturing, or 3D printing, offers new, promising opportunities. Compared to conventional production routes, it allows magnets to be shaped directly according to functional requirements, reducing material waste and offering substantial geometric flexibility. At the same time, controlling the magnetic properties of 3D-printed magnets remains challenging, as they are highly sensitive to their microstructure. This challenge simultaneously presents an opportunity to strategically optimize the microstructure and hence the magnetic properties by modifying the surface of the powder feedstock using silver nanoparticles.

Tuning coercivity through microstructure design

“We were able to demonstrate that a very small change in composition can significantly enhance coercivity, while preserving other key magnetic properties,” explains Nallathambi. In their publication, Nallathambi and his colleagues investigated how targeted surface modification of the commercially available Nd-lean powder feedstock influence the magnetic performance of 3D-printed Nd–Fe–B magnets. They showed that adding just 1 wt% of silver nanoparticles to the feedstock surface increases the coercivity by up to 17%, without compromising remanence or requiring additional post-processing steps. In the surface-modified sample, silver forms nanophase regions during solidification, facilitating heterogeneous nucleation and thereby altering the microstructure to refined, equiaxed grains of the Nd₂Fe₁₄B primary phase and a Ti-Zr-B-enriched intergranular phase, in contrast to the unmodified counterpart. This observed change in microstructure contributes to enhanced domain wall pinning and coercivity.

In a follow-up study, the researcher team examined the interplay between silver surface nano-modification and in-process heat treatment in 3D-printed magnets using transmission electron microscopy (TEM) and atom probe tomography (APT). The silver-containing nanophase regions and Ti-Zr-B-enriched intergranular phase in the modified sample result in significantly finer magnetic domain structure with enhanced domain wall pinning as evidenced by Lorentz TEM. Overall, surface nano-modification enables microstructure manipulation beyond conventional processing capabilities, yielding improved magnetic properties.

Recognition by CENIDE

The CENIDE Best Paper Award honours outstanding scientific publications of early-career researchers in six categories. Out of 41 nominated publications of 2024–25, six were selected, one for each research field covered by CENIDE. The awards are each endowed with 500 euros.

Awarded publication

Philipp Gabriel, Varatharaja Nallathambi, Jianing Liu, Franziska Staab, Timileyin Oyedeji, Yangyiwei Yang, Nick Hantke, Esmaeil Adabifiroozjaei, Oscar Recalde-Benitez, Leopoldo Molina-Luna, Ziyuan Rao, Baptiste Gault, Jan Sehrt, Franziska Scheibel, Konstantin Skokov, Bai-Xiang Xu, Karsten Durst, Oliver Gutfleisch, Stephan Barcikowski, and Anna Ziefuss, "Boosting Coercivity of 3D Printed Hard Magnets through Nano-Modification of the Powder Feedstock," Advanced Science 11 (46), 2407972 (2024).

MPG.PuRe

DOI

Follow-up publication

Varatharaja Nallathambi, Philipp Gabriel, Xinren Chen, Ziyuan Rao, Konstantin Skokov, Oliver Gutfleisch, Stephan Barcikowski, Anna Ziefuss, and Baptiste Gault, "Effect of Ag nano-additivation on microstructure formation in Nd-Fe-B magnets built by laser powder bed fusion," Acta Materialia 297, 121353 (2025).