Effect of ultrasonic cavitation on the diffusivity of a point defect in the passive film on formed Nb in 0.5 M HCl solution

Abstract

This work primarily focused on the influence of ultrasonic cavitation on the transport property of the point defect in the passive film on formed Nb in 0.5M HCl solution via electrochemical techniques based on the point defect model (PDM). The influence of ultrasonic cavitation on the composition and structure of the passive film was detected by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The transport property of a point defect in the passive film was characterized by the diffusivity of the point defect (D0). The influences of the ultrasonic cavitation power, passivated time and the distance between horn bottom and sample surface on D0 were analyzed. The results demonstrated that the passive film formed on Nb was an n-type semiconductor with a donor density (ND) ranging from 10(19) cm(-3) to 10(20) cm(-3) in the case of static state, while the order of ND increased one to two times by applying ultrasonic cavitation during film formation. The diffusivity of the point defect (D0) in the passive film formed on Nb at 0.5 V for 1 h in a 0.5 M HCl solution in the static state was calculated to be 9.704×10(-18) cm(2) s(-1), and it increased to 1.255×10(-16) cm(2) s(-1), 7.259×10(-16) cm(2) s(-1) and 7.296×10(-15) cm(2) s(-1) when applying the 180 W, 270 W and 450 W ultrasonic cavitation powers during film formation. D0 increased with the increment of the ultrasonic cavitation power, and decreased with the increased in formation time and distance between the horn bottom and sample surface. AES results showed the film structure and composition were changed by applying the ultrasonic cavitation. XPS results revealed that the passive film was mainly composed of Nb2O5 in the static state, and the low valence Nb-oxide (NbO) appeared in the passive film except Nb2O5 in the case of applying a 270 W ultrasonic cavitation power.

Electrochemical Corrosion Behavior of Ta2N Nanoceramic Coating in Simulated Body Fluid

“…It can be seen that the Mott-Schottky plots can be decomposed into two linear regions over the entire potential range, and the slopes of two linear regions in each plot are always positive, which is characteristics of n-type semiconductors behavior. Such two linear regions located at low and high potentials have also been reported for other metal oxides in different media [46,47,48]. This phenomenon was attributed to a transition of passive film character from semiconducting behavior to dielectric behavior, as discussed in our recent work [49].…”

Early-Stage Deactivation of Platinum-Loaded TiO2 Using In Situ Photodeposition during Photocatalytic Hydrogen Evolution

“…There have been many reports about the formation of defects by either or both of these effects, such as oxygen vacancies in metal oxides by ultrasonic treatment (e.g., SiO 2 , , Nb 2 O 5 , MoO 3 , ZnO, ZrO 2 , Fe 2 O 3 , SnO 2 ). In particular, Osorio-Vargas et al showed that oxygen vacancies are formed during low-frequency US treatment of TiO 2 .…”

Synergetic Effect of Corrosion and Ultrasonic Cavitation Erosion on Leaded Brass

“…This is largely ascribed to the protective effect of the passivation film (Ref 36). Essentially, the electrochemical tests documented in (Ref [37][38][39] prove unanimously that electrochemical properties of the passivation film formed due to ultrasonic cavitation differ considerably from those of the film produced in quiescent liquid. Moreover, the passivation film can improve the resistance to cavitation erosion, as confirmed in (Ref 40).…”