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Donghua University has developed a lightweight, highly stable sound-absorbing material

Time : 2021-11-22 Hits : 15

With the development of transportation industry, traffic noise pollution has become a serious problem, which has become a potential killer of global economy, ecological environment and human health. Because the porous structure and bent channel of fiber materials can enhance the friction and dissipation of acoustic waves, many researches have used fiber materials as the core component of noise absorber. However, due to the inherent limitations of large fiber diameter and low porosity, it is difficult for traditional fiber noise reduction materials to have high absorption performance for low-frequency noise easily generated by vehicles. If the thickness or density of the fiber material is increased, the weight of the material will be large, and the energy consumption will be increased, which is contrary to the green and low-carbon concept. And the common polymer noise reduction materials have poor heat resistance, not only easy to lead to material decomposition failure, and even cause safety problems.

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In order to solve the above problems, Prof. Jianyong Yu and his team from Donghua University proposed to prepare flexible ceramic nanofiber sponge (FCNSs) with unique layered entanglement structure composed of flexible SiO2 nanofibers (SNF) and reduced graphene oxide (rGO) by combining directional freeze drying technology and ascorbate reduction. In order to meet the requirements of traffic sound absorption materials for noise reduction performance, structural stability and heat resistance, flexible SNF with good thermal stability was selected as the foundation for constructing fiber frame structure. At the same time, flexible TWO-DIMENSIONAL GO nanosheets were selected as adhesives and macroporous blockers to establish effective entanglements between SNF and block the pores in the fiber wall. Finally, a sandwich assembly structure is designed to realize the multiple dissipation of broadband acoustic waves. Different from previous methods of preparing noise-reducing materials, the simple preparation of SNF combined with the flexibility of directional freeze drying technology makes FCNS easy to prepare and structure-adjustable.

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Structural design and hierarchy of FCNSs

The mechanical properties of FCNSs are closely related to the content of SNFs and GO, and FCNS70 (content OF SNF: GO 10:7) was found to have the desired structural stability. The unique entanglement structure gives FCNS excellent buckling performance and can withstand large buckling deformation (80%) without fracture. The FCNS70 also showed good cyclic buckling performance, retaining more than 70% of the initial maximum stress after 1000 cycles of cyclic buckling. In addition, the FCNSs showed the required compression fatigue resistance, with the plastic deformation of FCNS70 being only 4.3% after 1000 cycles of compression under large strain (60%). In addition, FCNSs combines the structural properties of polymer materials with the high temperature resistance of ceramics, showing stable viscoelasticity and superelasticity at different ambient temperatures.

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Mechanical characteristics of FCNSs

The johnson-Champoux-Allard model was used to guide and optimize the design of the FCNS, explore the influence of acoustic parameters on the sound absorption performance of the FCNS, and further design the structural parameters of the FCNS to achieve wideband noise absorption. A sandwich structure with FCNS thickness direction was further constructed to effectively enhance the multistage reflection path of sound waves within the material, thus successfully increasing sound energy dissipation, showing high noise absorption (NRC 0.56) and ultralightness (280.8 g/m2).

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Noise absorption applications of sandwich FCNS

This method breaks the bottleneck of low frequency absorption of traditional noise absorber and provides a broader idea for developing efficient noise reduction materials. Related research is entitled Flexible ceramic nanofibrous sponges with Hierarchically Entangled graphene networks enable noise The title of ABSORPTION was published in Nature Communications.

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