Electrochemical Behavior of Tantalum in Anhydrous Ethanol

Abstract

The electrochemical behaviors of Ta in Et4NCl ethanol solutions were investigated using potentiodynamic polarization, cyclic voltammetry, and potentiostatic current–time transient techniques, complemented with a scanning electron microscope (SEM). The potentiodynamic anodic polarization curves did not exhibit an active dissolution region due to the presence of a thin oxide film on the electrode surface, which was followed by pitting corrosion as a result of passivity breakdown by the aggressive attack of Cl− anions. SEM images confirmed the existence of pits on the electrode surface. The pitting potential (Enormalb) decreased with the increase in solution temperature, but increased with increasing potential scan rate. The potentiostatic current–time transients showed that the incubation time slightly decreased with increasing Et4NCl concentrations. The pitting growth current density agreed well with Hills’s model.

Anodic Dissolution Behavior of Zirconium in n-Butanol Solutions Containing Buⁿ₄NBr

“…The increase in pitting susceptibility with an increase in potential could be explained on the basis that an increase in the applied potential may increase the electric field across the passive film and therefore enhances the adsorption of the aggressive Br ¹ anions on the passive electrode surface. Similar results were also reported by Yang et al 6 and Ono and Habazaki. 29 Figure 4 presents the effects of scan rate (v) on the cyclic voltammetry curves of Zr in n-butanol with 0.08 M Bu n 4 NBr.…”

“…The cathodic current probably corresponds to hydrogen evolution. 6,19 The anodic current density increases from E corr to 0.2 V vs. SCE and then attains a plateau value about 115-135 µA/cm 2 until 1.2 V vs. SCE. The low limiting current density indicates that zirconium does not exhibit active dissolution in the potential region of 0.2 to 1.2 V vs. SCE.…”

“…4,5 The most commonly used, technically simple and economically viable preparation of zirconium alkoxide generally proceeds from zirconium tetracholoride with ethyl formate and dry ammonia. 6 However, this method consumes large amount of organic solvents and liberates harmful NH 3 gas. In addition, the yield is low.…”

Electrochemical Synthesis of Zirconium n-Butoxide

“…7 The common route to synthesize zirconium alkoxide is based on zirconium tetracholoride with ethyl formate and dry ammonia. 8 The process has the disadvantage that HCl gas is liberated, leading to severe corrosion of reaction apparatus. And the reaction is performed using large amounts of organic solvents which have to be costly disposed of.…”

The Electrosynthesis of Tantalum Ethoxide

“…In 1972 the electrochemical synthesis of tantalum ethoxide by anodic dissolution of tantalum in ethanol in the presence of NH 4 Cl as an electroconductive additive was patented. 19 Hereafter, tantalum ethoxide was prepared by Shreider, 20 Turova 21 and Yang [22][23][24][25][26] using the electrochemical method. When tantalum oxide is used as an electronic material for dielectrics, it is required to reduce the quantity of impurities such as transition metals typified by iron, alkali metals, e.g.…”