Electrochromic materials can be used in self-powered electrochemical sensors to display quantitative information without the need for silicon-based electronics or external instrumentation.

The effect of changing the distance of an ultrasonic horn tip from a stationary platinum disk electrode on limiting current density at various electroanalyte concentrations, ultrasonic frequencies (20 and <mml:math display="inline"><mml:mrow><mml:mn>40</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>kHz</mml:mi></mml:mrow></mml:math>40kHz ), and ultrasonic intensities was studied in an attempt to find the optimum position required for maximum sonoelectrochemical effect in “face-on” mode. Our findings were compared to mathematical models available in the literature, for the mass transport of electroactive species to the electrode under hydrodynamic flow conditions normal to the ultrasonic horn. A good fit with experimental results was found and confirmed the dependence of limiting current to operating parameters such as ultrasonic power, electrode-to-horn distances and electroactive species diffusion coefficient, and also highlighting the importance of ultrasonic frequency. From mass balance equations, it was then possible to develop an approach by analogy to an electrode subjected to pure hydrodynamic flow. A Levich-like equation relating the limiting current density, the square root of ultrasonic intensity, and the inverse square root of the electrode-horn distance was generated for ultrasonic frequencies of 20 and <mml:math display="inline"><mml:mrow><mml:mn>40</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>kHz</mml:mi></mml:mrow></mml:math>40kHz , allowing the generation of an “equivalent” flow velocity under sonication, an important and useful parameter in chemical engineering.

This paper is devoted to zinc corrosion and oxidation mechanism in an ultrasonically stirred aerated sodium sulfate electrolyte. It follows a previous study devoted to the influence of 20 kHz ultrasound upon zinc corrosion in NaOH electrolytes [Ultrason. Sonochemis. 8 (2001) 291]. In the present work, various ultrasound regimes were applied by changing the transmitted power and the wave frequency (20 and 40 kHz). Unlike NaOH electrolyte which turns the zinc electrode into a passive state, Na2SO4 saline media induces soft corrosion conditions. This allows a study of the combined effects of ultrasonically modified hydrodynamic and mechanical damage (cavitation) upon the zinc corrosion process. A series of initial experiments were carried out so as to determine the transmitted power and to characterize mass transfer distribution in the electrochemical cell. Zinc corrosion and oxidation process were subsequently studied with respect to the vibrating parameters. When exposed to a 20 kHz ultrasonic field, and provided that the electrode is situated at a maximum mass transfer point, the corrosion rate reaches values six to eight times greater than in silent conditions. The zinc oxidation reaction, in the absence of competitive reduction reactions, is also activated by ultrasound (20 and 40 kHz) but probably through a different process of surface activation.

This paper is devoted to the electroless plating of non-conductive substrates under ultrasound at 530 kHz. The ultrasonic irradiation is applied to the activation and to the plating steps. Effects are measured by following the final copper thickness obtained in 1 h of plating time, easily correlated to the average plating rate. It appears that ultrasound has a strong influence on the plating rates enhancement, and assumptions can be made that this increase could be linked to the catalyst cleaning. This is confirmed by XPS measurements.