To ensure effective adhesion of a coating to its substrate it is essential to form strong physical and chemical bonds between them. To achieve this, the substrate is often roughened or textured in a process frequently referred to as surface modification. One major user of surface modification is the electronics industry. Traditional manufacturing techniques for such surface modification often use hazardous chemicals e.g. hot alkaline permanganate for polymer composites and hydrofluoric acid for ceramics both of which are hazardous chemicals to work with. We have found that quite often the use of power ultrasound and water with no added chemicals can produce similar surface modifications.
The ability of ultrasound to clean and activate surfaces is one of the first applications in sonochemistry. It is, for example, an excellent method of initiating Grignard reactions thus avoiding the addition of other chemicals such as iodine.
Examples of surface activation and cleaning include the ultrasonic cleaning of membranes, electrodes and analytical probes. The efficiencies of both homogeneous and heterogeneous catalytic systems have been significantly enhanced by sonication, eg, the rate of isomerization of 1-alkenes using metal carbonyls in the presence of ultrasound is over 105 higher than that observed in its absence. A similar enhancement factor is observed with the catalytic efficiency of ultrasonically treated metal catalysts for hydrogenation. Thus, ultrasound can be used for both materials processing and enhancing the rates of chemical reactions.