Nanotechnology of nanoparticle colloids based on high-entropy alloys using ionic liquids

A. Dvurečenskij, A. Cigáň, , M. Škrátek, M. Majerová, J. Maňka

In colloids of metal nanoparticles based on high-entropy alloys (HEA-High Entropy Alloys) in imidazolium-based ionic liquids, the properties of three objects meet: ionic liquids, HEA alloys and nanoparticles. Each of them separately exhibits unique properties that have attracted considerable attention in recent decades due to their significant impact on emerging applications with high potential, e.g. for new “green” technologies in the field of production of new materials, equipment, in the field of environmental protection, energy savings, etc. Ionic liquids have unique physico-chemical properties such as high ionic conductivity, non-flammability, high thermal and chemical stability. HEAs are alloys that contain at least five elements in equal concentration. HEAs are used for extreme temperature, functional thermoelectric, superconducting, magnetic or magnetocaloric materials. They exhibit slow diffusion under stress leading to the so-called “self-healing”. The structural and magnetic properties of colloidal CoCrCuFeNi HEA nanoparticles in ionic liquid [BMIM.BF4] obtained by magnetron sputtering were studied. Colloids contain ultra-small monocrystalline nanoparticles (2–3) nm in size. These nanocolloids (NK) exhibit complex magnetic properties that are a function of temperature, applied magnetic field, and mass content of nanoparticles in the colloids, in Fig. The obtained results indicate significant magnetic interactions between the ionic liquid and the HEA nanoparticles and the structure. They are among the first to show a significant change in magnetic properties with temperature, e.g. of [BMIM.BF4] itself and on the competing nature of the diamagnetic and paramagnetic components.

Mass magnetization Ma [BMIM.BF4] HEA NK-L and NK-H as a function of the applied magnetic field H at a temperature of 2 K. Arrows indicate the direction of increase or reduction of the applied magnetic field of the main magnetization loops of both nanocolloids with low and high concentration of nanoparticles, starting from zero field.

Related projects: VEGA 2/0141/21 and APVV-16-0263. The result was achieved in cooperation with the SAV Electrotechnical Institute, the Center for Energy Research, the Hungarian Academy of Sciences and the SAV Institute of Polymers.

Publication in CC magazine:

• DVUREČENSKIJ, Andrej – CIGÁŇ, Alexander – LOBOTKA, P. – RADNÓCZI, G. – ŠKRÁTEK, Martin – BENYÓ, J. – KOVÁČOVÁ, E. – MAJEROVÁ, Melinda – MAŇKA, Ján. Colloids of HEA nanoparticles in an imidazolium-based ionic liquid prepared by magnetron sputtering: Structural and magnetic properties. In Journal of Alloys and Compounds, 2022, vol. 896, art. no. 163089. ISSN 0925-8388. (6.371 – IF2021) Q1. Best JCI PERCENTILE, 2021: 92.86 %.