Direct Synthesis of Elastic and Stretchable Hierarchical Structured Fiber and Graphene-Based Sponges for Noise Reduction.

Noise pollution, as one of the three major pollutants in the world, has become a great burden on people's health and the global economy. Most present noise absorbers suffer large weight and inevitable compromise between good low-frequency (usually <1000 Hz) and high-frequency (typically >1000 Hz) noise reduction performance. This study presents a scalable strategy to directly synthesize ultrafine fiber sponges with ultrathin graphene-based vibrators by the synchronous occurrence of humidity-assisted electrospinning and electrospraying. The unique physical entanglements between reduced graphene oxide (rGO) nanosheets and ultrafine fibers endow hierarchical vibration structured fiber sponges (VSFSs) with excellent mechanical properties, which could withstand large shear strain (60%) and tensile stress (6000 times its weight) without damage and almost have no plastic deformation after 1000 compressions. Attribute to the vibration effect of ultrathin graphene-based vibrators and the viscous friction effect of porous fiber networks, the VSFSs achieve both good low-frequency (absorption coefficient of 0.98 in 680 Hz) and high-frequency sound absorption (absorption coefficients above 0.8 in 2000-6300 Hz) simultaneously. Furthermore, the noise reduction coefficient (NRC) of lightweight VSFSs (thickness of 30 mm) reaches 0.63, which could reduce high decibel noise by 24.4 dB, providing potential solutions for developing ideal noise-absorbing materials.