Acoustically active articles

A method of forming an article including porous inorganic agglomerates, the method comprising:

• providing metal oxide powders having an average particle size in a range from 100 nm to 10 microns;
• mixing the metal oxide powders with one or more reactive monomers or polymers containing carbon or silicon and water to form a mixture;
• polymerizing the mixture to form a plurality of composite beads, the composite beads each comprising the metal oxide powders distributed inside a polymeric binder, and the composite beads having an average size in a range from about 50 microns to about 2 mm;
• and
• heating the composite beads at an elevated temperature in a range from about 400 to about 1000° C. to form the porous inorganic agglomerates,
• wherein the article comprises:
• the porous inorganic agglomerates having an average dimension in a range from about 50 microns to about 2 mm, the porous inorganic agglomerates each including a network of carbon or silica, and metal oxide particles embedded in the network,
• wherein the article comprises 5 to 25 wt % carbon or silica, and 95 to 75 wt % metal oxide particles.