Electrochemical Phase Formation of Metals and Alloys at Chemically Identical Solid or Liquid Cathode: Part 1. Metals

Electrochemical Polymorphic Phase Formation in Metals

“…The last two years were marked by new experimental results proving the existence of the phenomenon of the electrochemical phase formation in metals and alloys via a supercooled liquid state stage. Relying on the data obtained, it was found that the discussed phenomenon is proved by the following experimental facts: -(1) electrochemical phase formation in metals resulting in phases with amorphous structure typical of a solidified metallic liquid when crystallization is hindered in the course of deposition [28]; -(2) the formation enhancement of intermetallic compounds involving metallic cathode elements and the electrodepositing metal plus evolvement of additional intermetallics enriched in cathode elements, on replacing a solid cathode with a chemically identical liquid one [29]; -(3) the formation of intermetallics between solid metallic cathode elements and the solvent in the alloy electrodepositing as substitution solid solution, as well as enhancement of these processes accompanied by the development of additional intermetallics enriched in cathode elements on replacing a solid cathode with a chemically identical liquid one [30]; -(4) with alloys electrodepositing as substitution solid solution at a solid metallic cathode, the formation of intermetallics including cathode elements and the alloy solute element building no distinct phase [30]; -(5) on replacing a solid cathode with a chemically identical liquid one, intermetallics formation is enhanced involving metallic cathode elements and the electrodepositing alloy solute, building no distinct phase, plus additional intermetallics enriched in cathode elements emerge [30]; -(6) with alloys electrodepositing as intermetallic compounds at a solid metallic cathode, formation of intermetallics involv-ing components of the depositing alloy and, in parallel, cathode elements and alloy components is observed [31]; - (7) on replacing a solid cathode with a chemically identical liquid one for alloys electrodepositing as intermetallic compounds, additional intermetallics enriched in the major alloy component and cathode elements are formed [31]. The aim of the work was the further experimental verification of the existence of the phenomenon in point.…”

Review—Electrochemical Phase Formation via a Supercooled Liquid State Stage: Metastable Structures and Intermediate Phases

“…Replacing a solid cathode with a chemically identical liquid one thus increases the ion cathodic reduction rates for depositing metals/alloys. 169 This experimental finding was a proof that the phenomenon of electrochemical phase formation in metals and alloys via a supercooled liquid state stage does exist.…”

“…168 It is seen from Table V that the rate constants k L for reactions at a liquid cathode are much in excess of corresponding k S values pertaining to a solid cathode of the same chemical composition. 169 Among the metals and alloys investigated, the highest k L /k S ratios are observed with Co (76.6) and Fe-Cr (19.9).…”

“…Should the electrochemical reduction be accelerated following replacement of a solid cathode to a chemically identical liquid one, this will be an argument for the phenomenon in point. 169 The experimentation involved a cathode of Wood's alloy having melting point at 68.5 °С and containing 50% bismuth, 25% lead, 12.5% tin and 12.5% cadmium. The electrocrystallization of some metals (Ni, Co, Fe) and alloys (Fe-Сr, Fe-Сr-Ni) was carried out at 65 °C with a solid cathode and at 75 °C with a liquid one.…”

“…168 Therefore, if the phenomenon in point exists, a change from a solid to a chemically identical liquid cathode should lead not only to an acceleration of intermetallics formation at the cathode/electrodepositing metal interface but also to development of additional intermetallics richer in elements contained in the cathode. 171,170 There are good grounds to assume such behavior. A liquid metal diffusion coefficient is known to be several times that of a solid metal because the atoms in a liquid metal are in an excited state.…”