Hierarchically maze-like structured nanofiber aerogels for effective low-frequency sound absorption.

Noise has been regarded as an environmental pollutant that greatly affects people's physical and psychiatric health. Fibrous sound absorption materials are widely used to release the annoyance that brought by noise pollution, however, the fibrous materials are limited by poor sound absorption ability in low-frequency, heavyweight, and excessive thickness. Herein, composite nanofiber aerogels are designed with a hierarchical maze-like microstructure, which is fabricated by interweaving the cellulose nanocrystal lamellas with polyacrylonitrile electrospun nanofiber networks through the freeze-casting technique. The designed maze-like structure shows obvious enhancement in the low-frequency sound absorption band compared to the fiber aerogels made by the network structure. Moreover, through carefully regulating the maze structure, composite nanofiber aerogels with excellent sound absorption performance (with an NRC of 0.58) and lightweight property (11.05 mg cm) can be fabricated. In addition to the superior sound absorption ability, the hierarchical nature of the maze-like structure also guarantees the nanofiber aerogels with robust mechanical properties, which can be tailored to various shaped objects on a large scale. These favorable characters present that the composite nanofiber aerogels potential choice for sound absorption in the fields of vehicles, buildings, and indoor reverberation.