  Foaming metals modulates their physical properties, enabling attractive
applications where lightweight, low thermal conductivity or acoustic isolation
are desirable. Adjusting the size of the bubbles in the foams is particularly
relevant for targeted applications. Here we provide a method with a detailed
theoretical understanding how to tune the size of the bubbles in aluminium
melts in-situ via acoustic pressure. Our description is in full agreement with
the high-rate three-dimensional X-Ray radioscopy of the bubble formation. We
complement our study with the intriguing results on the effect of foaming on
electrical resistivity, Seebeck coefficient and thermal conductivity from
cryogenic to room temperature. Compared to bulk materials the investigated foam
shows an enhancement in the thermoelectric figure of merit. These results
herald promising application of foaming in thermoelectrics materials and
devices for thermal energy conversion.

Materials Science