A novel Gradient-Pore Structure SiO2/SiCnw Ceramic Composite Nanofibrous Aerogels for Efficient Low-Frequency Noise Reduction and Thermal Insulation

The rapid development of industry and transportation has given rise to serious noise pollution, which posing serious threats to the social economy and human physical and mental health. However, commonly existing fibrous noise absorption materials with single pore-structure are limited by their large density, poor sound absorption ability, which are difficult dissipation of noise at low frequency. Herein, gradient-structured fire-resistance elastic ceramic nanofiber aerogels with dual scale structure at micro and macro levels are success-fully structured through step-by-step directional freeze-casting technology. The macro gradient pore structure improved the noise injection, and self-assembly nano network constructed by SiCnw improved the acoustic contact area of aerogel. In addition, the good thermal conductivity of SiCnw helps to convert sound energy into heat energy and quickly dissipate heat, further improving the sound absorption effect. The noise reduction coefficient of the obtained ceramic fibrous aerogels reaches 0.55, and the maximum value of the sound absorption coefficient can be close to 1. In addition, the hydrophobic group in the binder gives the aerogel good mechanical properties (60% compressibility) and super hydrophobic properties (water contact angle ≈136°). The successful construction of lightweight, hydrophobic, fire-resistant gradient structure aerogel will provide a new prospect for the upgrading of the next generation noise absorber.