A persistent ultrasound-assisted hydrothermal method has been developed to prepare cobalt oxide incorporated nitrogen-doped graphene (Co3O4/N-GO) hybrids. The electrochemical behaviors and catalytic activity of the prepared hybrids have been systematically investigated as cathode materials for Al-air battery. The results show that ultrasonication can promote the yield ratio of Co3O4 from 63.1% to 70.6%. The prepared Co3O4/N-GO hybrid with ultrasonication exhibits better ORR activity over that without ultrasonication. The assembled Al-air battery using the ultrasonicated Co3O4/N-GO hybrid exhibited an average working voltage of 1.02 V in 4 M KOH electrolyte at 60 mA∙cm-2, approximately 60 mV higher than that using hybrid without ultrasonication. This should be attributed to large number density of fine Co3O4 particles growing on the dispersed GO sheets under the persistent ultrasonication. The related ultrasonic mechanism has been discussed in details.

In this work, ultrasound has been employed to help prepare Al-Sc alloys using the molten salt electrolysis. The effects of synergetic ultrasound on the Sc content and primary Al3Sc particles of Al-Sc alloys are specifically investigated. Ultrasound can strongly promote the Sc content of the electrolytic Al-Sc alloy and transform the large Al3Sc phase clusters into fine cubic particles. Meanwhile, it also homogenizes the distribution of Al3Sc phase. The Sc content increases by 74.4% up to 1.43 wt% when applying ultrasound during both electrolysis and solidification process. It also transforms the molten salts/liquid Al interface by enhancing the wettability. The huge primary Al3Sc phase clusters transform into fine cubic particles by ultrasound. The average particle size reduces from 77 ± 36 μm down to 21 ± 8 μm. The concerned mechanism have been discussed in detail.