an article of manufacture comprises a carbon - containing matrix . the carbon - containing matrix may comprise at least one type of carbon material selected from the group comprising graphite crystalline carbon materials , carbon powder , and artificial graphite powder . in addition , the carbon - containing matrix comprises a plurality of pores . the article of manufacture also comprises a metal component comprising al , alloys of al , or combinations thereof . the metal component is disposed in at least a portion of the plurality of pores . further , the article of manufacture comprises an additive comprising at least si . at least a portion of the additive is disposed in an interface between the metal component within the pores and the carbon - containing matrix . the additive enhances phonon coupling and propagation at the interface .