Aerogel two ways: Towards ultralight noise absorbers

Abstract

Aerogels are a class of synthetic materials that are derived by using supercritical drying to extract the liquid component of a gel and replacing it with gas. This process results in the formation of an ultra-lightweight nanoporous solid composed of up to 99.98% air by volume. In this talk, we explore the possibility of developing aerogel-based ultralightweight sound absorbers in two different forms. First, we focus on the acoustic characterization of aerogel granules. The absorption properties of four different aerogels with granule diameters ranging from 2 to 4000 μm and granule densities ranging 120 to 180 kg/m3 are presented. Next, we discuss the additive manufacturing of aerogel-based sound absorbers using a freeze casting method. This novel method allows the fabrication of solid aerogel structures with controlled microstructural properties. The sound absorption and transmission loss properties of 3-D printed aerogel samples are measured using an impedance tube setup. We demonstrate that such structures can provide significantly higher absorption and transmission loss properties as compared with current passive noise reduction materials. [Work Sponsored by NASA EPSCoR.]