Preparation of Very Active Metal Powders

The irradiation of various catalytic powders with power ultrasound causes dramatic changes in particle aggregation, surface morphology, and thickness of the surface oxide coating. Sometimes, but by no means always, this is reflected in their catalytic activity. 

Boudjouk et al reported the application of ultrasound to the hydrosilylation of styrene over a Pt/C catalyst yielding 95% of the addition product over 2 h at room 

The effects of ultrasound on the reactivity of copper metal as a stoichiometric reagent have been documented in the literature in two cases, the Ullmann coupling 2 and the reaction with salicylidene-aniline to form uncharacterized copper complexes.33 These reactions are discussed in Ch. 5 (pp. 171 and 208). In addition, ultrasound has been used to enhance the reduction of Cu salts by alkali metals to form highly reactive copper dispersions.  

To conclude this section, some papers dealing with the preparation of zinc powder can be mentioned. S In this case the change in powder reactivity is explained by a dramatic change in morphology. In particular, the initially smooth and spherical metal particles become noticeably roughened upon sonication. 

---