Electrodeposition of Magnetic SmCo Films from Deep Eutectic Solvents and Choline Chloride-Ethylene Glycol Mixtures

Abstract

Suitability of mixtures based on ethylene glycol and choline chloride is evaluated for the electrodeposition of magnetic SmCo alloys. Deep eutectic solvents (DES) are characterized by a wide electrochemical window, allowing the electrodeposition of metallic elements having a highly negative reduction potential. Electrodeposition of unconventional metals with reduction potential well below hydrogen evolution one is, in principle, feasible (e.g. Sm). Moreover, the limited presence of water during the growth of SmCo alloys may reduce oxidation and consequently improve the magnetic properties with respect to the employment of an aqueous bath. Deposits composition is strongly affected by process parameters and bath composition. Increasing choline chloride concentration and/or adding glycine to the solution allows to achieve higher Sm content in the deposit. Potentiostatic electrodeposition has been carried out in a conventional three electrodes cell, with potential interval selected from −0. The role of non-aqueous electrolytes is gaining importance due to their ability to overcome limitations normally observed in the electrodeposition processes from aqueous media. In particular, this is true for the metal elements having reduction potential well below hydrogen evolution one. Ionic liquids are in fact characterized by wider electrochemical windows limiting the onset of secondary processes suppressing the metal reduction one.1-3 One practical example is the electrodeposition of rare earth metals and their alloys (e.g. SmCo). Gomez et al. and Cojocaru et al. proposed a study on the electrodeposition of SmCo from a deep eutectic solvent (DES) based on choline chloride and urea (1ChCl:2U). [4][5][6] The suitability of such a system for the electrodeposition of both single metals (Sm and Co) and alloy (SmCo) was verified. Deposits were characterized by a high Sm content, i.e. 46-79 wt% Sm, while the optimal composition for the best magnetic performances is 23-25 wt% Sm, corresponding to the Sm 2 Co 17 phase. [7][8][9] In literature, works on this alloy from both waterbased 10-16 and non-aqueous solution are reported. 17 In the former case, fundamental is the employment of glycine as complexing agent as shown by Wei et al. [13][14][15] However, in-plane coercivities in the order of H c|| = 100 Oe were observed with the formation of SmO, Sm(OH) 3 and Co(OH) 2 .14 These values are referred to films produced by electrodeposition, an interesting technique from the fabrication point of view but with a huge limitations in terms of compositional and purity control with respect to traditional methods as casting or sputtering through which hard SmCo magnets are obtained (H c|| ∼ kOe).This work consists in the study of different mixtures based on ethylene glycol and choline chloride (1ChCl:2EG and 1ChCl:4.5EG) in order to evaluate the effect of ChCl concentration on SmCo codeposition and its magnetic properties. Studies on the physical properties of solutions with different ChCl:HBD (Hydrogen Bond Donor) molar ratio are reported in ...

Zinc electrodeposition from a chloride-free non-aqueous solution based on ethylene glycol and acetate salts

“…As a consequence, the elimination or substitution of choline chloride is an option to be considered. In a previous work, we investigated the effect of changing the choline chloride/ethylene glycol molar ratio in the bath on film composition, fixing the other electrodeposition parameters [32]. In more recent times, we have demonstrated the possibility to obtain high purity films [33] from a simple ethylene glycol solution containing the precursor salt, limiting the concentration of chlorides of about one/two orders of magnitude with respect to 1ChCl:2EG DES.…”

In Search of Magnetic Properties of Samarium Cobalt (Sm2Co17) within a Low-Temperature Sintering Process

“…The results also called by nonhysteresis condition with zero coercivity and retentivity, which indicated that the sample ex-hibits an isotropic characteristic without a preferential axis [27]. Moreover, it indicates that under a normal sintering temperature, the material temperatures of 500 °C and 400 ℃ exhibit ferromagnetic properties with a magnetic saturation of 0.219 and 0.239 emu/g [27][28][29]. In the magnetic nanoparticles, the particle size significantly influences the magnetic strength [18].…”

Zinc Nanoparticles Electrodeposited on TiO2Nanotube Arrays Using Deep Eutectic Solvents for Implantable Electrochemical Sensors

“…20 DESs are characterized by their excellent solvation properties (i.e., capability to dissolve a wide range of compounds such as metal salts) and wide electrochemical window (ECW), which allows the electrodeposition of metallic elements having a highly negative reduction potential (e.g., unconventional metals with reduction potential well below hydrogen evolution). 21,22 Compared to gas-based metal deposition techniques such as physical vapor deposition, DESs provide a simple, high-throughput, low-cost, and environmentally friendly method for the development of nanostructures at laboratory and industrial scales. 20,23 Choline chloride (ChCl) is one of the most commonly used HBAs (organic salt) in DES preparation due to its low cost and nontoxicity as well as its biodegradability.…”