Untangling the role of the carbon matrix in the magnetic coupling of Ni@C nanoparticles with mixed FCC/HCP crystal structures

• Type: Article in International Scientific Journal
• Date: 2023

Authors

Fadel, M (Author) Other; Martin Jimeno, FJ (Author) Other; Fernandez Garcia, MP (Author) Other; Suarez Garcia, F (Author) Other; Paredes, JI (Author) Other; Belo, JH (Author) FCUP; Araujo, JP (Author) Other; Adawy, A (Author) Other; Martinez Blanco, D (Author) Other; Alvarez Alonso, P (Author) Other; Blanco, JA (Author) Other; Gorria, P (Author) Other

Journal

Title: Journal of Materials Chemistry C

Vol. 11

Pages: 4070-4080

ISSN: 2050-7526

Publisher: Royal Society of Chemistry

Indexing

ISI Web of Knowledge - 6 Citations

Scopus - 7 Citations

Other information

Authenticus ID: P-00Y-444

DOI: 10.1039/d3tc00257h

Abstract (EN): Nowadays, Ni@C nanostructured materials are attracting a great deal of attention due to their multiple catalytic or magnetic functionalities. In this article we report on the investigation of the correlation between the microstructure and magnetic properties of Ni nanoparticles embedded in a carbon matrix. The samples were obtained following a two-step procedure that ensures protection against nanoparticle oxidation, and was carried out in the following way: (i) the synthesis of a nickel-imidazole-based metal-organic framework (MOF) by a simple method in an aqueous medium at moderate temperature (95 degrees C); and (ii) carbonization of the MOF at different temperatures between 400 and 600 degrees C to obtain a carbon-supported hybrid material, containing Ni nanoparticles with an artichoke-like morphology, where a Ni-FCC core is surrounded by bracts of Ni-HCP and Ni3C. The average size of the nanoparticle slightly changes from 7 to 10 nm as the carbonization temperature is increased, but the Ni-FCC core diameter ranges from 3 to around 6 nm. We show how the information obtained on the evolution of the magnetic behaviour with carbonization temperature, using X-ray diffraction and electron microscopy, complements each other by providing consistent structural and magnetic characteristics of the investigated Ni@C nanoparticles. In fact, this joint analysis allows us to explain the formation and transformation of different Ni-based crystalline phases along the synthesis process, including Ni3C and Ni with both hexagonal and cubic crystalline structures. The amount of conventional Ni-FCC is below 10 wt% for the sample treated at 400 degrees C and it can reach up to 50 wt% for that treated at 600 degrees C. Finally, based on our current findings we propose an explanation for understanding the magnetic properties of Ni@C, in which the Ni-FCC core spins mainly govern the magnetic coupling of the whole system.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11