Unusual "chemical" mechanism of carbon co-deposition in Cr-C alloy electrodeposition process from trivalent chromium bath

Breaking barriers in electrodeposition: Novel eco-friendly approach based on utilization of deep eutectic solvents

This review article provides a comprehensive examination of the innovative approaches emerging from using deep eutectic solvents (DESs) in electrodeposition techniques. Through an in-depth exploration of fundamental principles, the study highlights the advantages of DESs as electrolytes, including reduced toxicity, enhanced control over deposition parameters, and specific influences on morphology. By showcasing specific studies and experimental findings, the article offers tangible evidence of the superior performance of DES-based electrodeposition methods. Key findings reveal that DESs utilization enables eco-friendly electrodeposition of noble metal and transition metal coatings, coatings of their alloys and composites, as well as electrodeposition of semiconductor and photovoltaic alloy coatings; while also addressing challenges such as hydrogen evolution in conventional electrolytes. Notably, DES-based electrolytes facilitate the formation of electrodeposits with unique nanostructures and improve the stability of colloidal systems for composite coatings. The article contains invaluable tables detailing electrolyte compositions, electrodeposition conditions, and deposition results for a diverse array of metals, alloys, and composites, serving as a practical handbook for researchers and industry practitioners. In conclusion, the review underscores the transformative impact of DESs on electrodeposition techniques and emphasizes the prospects for future advancements in surface modification and material synthesis.

Synthesis and thermal reaction of stainless steel nanowires

Due to the perfection of microelectronics fabrication, silicon is presently the preferred base material in the design of micromechanical devices. By contrast, steels are the dominating construction materials in macroscopic engineering. So, it is appealing to explore the potential of stainless steel nano objects. To this aim, we developed an electrochemical method for and investigated the fabrication of FeCr(C) nanowires and study their thermal reaction to design the microstructure. Wires, 50 to 150 nm in diameter, are produced by template-assisted electro-deposition. Under thermal annealing, they develop first a core-shell structure of an Fe-rich core and a dense Cr-rich carbide shell. The shell thickness is well controllable via the initial composition of the wires. In a later, second reaction stage, wires with rather thin shells (about 8 nm thickness) demonstrate a 'stacking inversion' that finally leads in a self-driven reaction to the formation of hollow carbide tubes decorated with iron rich clusters on their outer surface.

'Green' Cr(iii)-glycine electrolyte for the production of FeCrNi coatings: electrodeposition mechanisms and role of by-products in terms of coating composition and microstructure

The electrodeposition of stainless steel-like FeCrNi alloys for miniaturised devices is appealing as it would allow combining excellent material properties (e.g. corrosion resistance, hardness, biocompatibility) at low-cost. However, conventional baths often contain hazardous hexavalent chromium. Cr-based alloys electrodeposited from environmentally friendly trivalent chromium electrolytes are crucial for industrial application for facilitating the transition towards sustainable and ecological production and processing. Nevertheless, this process has not been comprehensively studied or understood in depth: especially the role of organic agents (common additives for improving Cr(iii)-based plating; e.g. glycine) in terms of material properties of the electrodeposits. The aim of this work was to investigate the electrodeposition of FeCrNi coatings from a ‘green’ Cr(iii)–glycine electrolyte. Novel information was attained by analysing films developed under various conditions and characterising them using a combination of advanced techniques. The evolution of microstructure (from amorphous to nanocrystalline) in correlation with film composition (i.e. metals ratio and presence of impurities) and elemental 3D spatial distribution was achieved for coatings produced from different anode materials and thermal post-treatment. The influence of Cr(iii) and glycine in terms of coating atomic contents (i.e. Fe–Cr–Ni–O–C–N–H) was evaluated for films in which both the applied current density and electrolyte composition were varied. These results, together with a thorough analysis on metals speciation/complexation allowed us to propose various Cr(iii)-based electroreduction mechanisms, and to observe, upon annealing, segregation and distribution of impurities, as well as of oxides and metals with respect to microstructure variation, providing an explanation for the amorphisation process.

Electrodeposition mechanisms of a ‘green’ FeCrNi Cr(iii)–glycine electrolyte and their correlation with coatings' composition (metals/impurities), microstructure and elemental distribution variations.

Anneal-Hardening Behavior of Cr-Fe-C Alloy Deposits Prepared in a Cr3+-Based Bath with Fe2+ Ions

Cr-Fe-C alloy deposits were successfully prepared on high-carbon tool steel in a Cr³⁺-based electroplating bath containing Fe²⁺ ions and suitable complex agents. A Cr-based alloy deposit was obtained with an electroplating current density higher than 25 Adm⁻², and a Fe-based alloy deposit was obtained using a current density of 20 Adm⁻². Following electroplating, these alloy deposited specimens were annealed via rapid thermal annealing (RTA) at 500 °C for different periods up to 30 s. The experimental results show that Cr- and Fe-based alloy deposits could be significantly hardened after RTA at 500 °C for a few seconds. The maximum hardness was that of the Cr-Fe-C alloy deposit annealed at 500 °C for 10 s. The maximum hardness of 1205 Hv was detected from the annealed Cr-based alloy deposit prepared with 30 ASD. The hardening mechanism of annealed Cr- and Fe-based alloy deposits is attributed to the precipitation of C-related membranes. The hardness values of the annealed Cr- and Fe-based alloy deposits increase with the increasing degree of crystallization of the C-related membranes.