Microcellular Ceramic Foams: Manufacturing and Study of Acoustical Properties

A novel processing method for fabricating high porosity microcellular ceramic foams for sound absorption applications has been developed. The strategy for fabricating the ceramic foams involves: (i) forming some shapes using a mixture of preceramic polymer and expandable microspheres by a conventional ceramic forming method, (ii) foaming the compact by heating, (iii) cross-linking the foamed body, and (iv) transforming the foamed body into ceramic foams by pyrolysis. By controlling the microsphere content and that of the base elastomer, it was possible to adjust the porosity with a very high open-cell content (ranging between 43 - 95%), high microcellular cell densities (9 × 10⁸ - 1.6 × 10⁹ cells/cm³) and desired expansion ratios (3 - 6 folds). Sound absorption testing has been performed using ASTM C-384 standard test. The preliminary results show that ceramic foams are candidate sound absorption materials.