An efficient fabrication method of lightweight aramid nanofibrous aerogels for high-efficient sound absorption and thermal properties

Abstract The aramid nanofibrous aerogels (ANFs) have various application prospects due to their ultra-light, high porosity and excellent properties of aramid fibers. However, the preparation of ANFs requires long preparation time and their ultra-dense pore structure leads to poor sound penetration and high sound energy reflectivity, which ultimately makes the overall sound absorption performance of ANFs poor. Therefore, a strategy for synthesis of ANFs is designed to achieve light weight, excellent thermal insulation performance and significantly improve sound absorption properties. This strategy combines cell pulverizing, pump-filtration molding, and directional freezing to ensure structural strength of the aerogel without the addition of cross-linking agents, and this process enables the ANFs to introduce in macro-pores while keeping nano-pores. The structure of multi-layered pores effectively reduces the reflectivity of incident acoustic energy and improves the sound absorption coefficient. The interconnected macro-pores and interlaced small pores of ANFs provide good sound absorption performance (noise reduction coefficient (NRC) = 0.348), excellent flame retardant and thermal insulation properties (thermal conductivity=0.0635W/(m*K)) with ultralight (density=40.5 mg/cm3) in a thinner thickness (15 mm), which extend the potential of ANFs in areas of noise control and thermal insulation. In addition, the structure of multi-scaled pores can also be formed inside other aerogels by using the method of cell pulverization and filtration preparation, which can be helpful for improving their properties of thermal insulation and sound absorption.