Title: Literature Review of Nb Electroplating
Author: Dmytro Chirkov
Institution: Legnaro National Laboratories of INFN
Abstract: The main aim of this work is try to understand if expensive techniques of niobium coating could be replaced by cheaper electroplating method.
Nowadays electrochemical surface treatment is one of the most used approaches in industry.
Aqueous solutions has been the most widely used process mainly because of advantages such us low cost, non-flammability, high solubility of electrolytes, high conductivities resulting in low ohmic losses, high solubility of metal salts and high rates of mass transfer. However, despite these advantages there are several limitations in using aqueous solutions such as limited potential windows, gas evolution processes that can result in hydrogen embrittlement, passivation of substrates, electrodes and deposits, and the necessity for hazardous complex agents such as cyanide, causing environmental contamination. These are the reasons why new non-aqueous solutions to electrodeposit niobium have been researched.
One of the main limitations in using aqueous solutions is their narrow electrochemical window. The major reason for carrying out electrodeposition in non-aqueous electrolytes (such as conventional organic solvents, ionic liquids and molten salts) is water and air stability and the wide electrochemical window of these media.
Alternatively, also high temperature molten salts have been used extensively for niobium electrodeposition. They have wide potential windows, high conductivities and high solubility for metal salts. In fact, they have most of the advantages of aqueous solutions and overcome most of the limitations of aqueous solutions, but their one major limitation is the very high temperature (more than 750 °C).
Therefore, the alternative to high temperature molten salts was an ionic substance that melts at a low temperature. Over the last few decades, room temperature ionic liquids have been widely studied in various scientific fields due to their interesting properties, such as negligible vapour pressures, high chemical and thermal stability, acceptable intrinsic ionic conductivity and wide potential window.
Ionic liquids are molten salts with melting points below 100 °C and they consist entirely of cations and anions. The development of ionic liquids, especially air and water stable types, has attracted extensive attention since they have outstanding physical properties.
The aim of this work will be the analysis of available literature data in order to have precise knowledge about niobium behavior in the different electrolytes and to get new information about possible electrolytes based on ionic liquids.