NANOSTRUCTURED SOUND-ABSORBING FOAM MATERIALS

摘要

This paper presents an approach to control the noise protection features of materials with open pores. The conventional foamed materials with few hundreds micron size pores were used as a matrix. The pores were impregnated by the suspension of silica or magnetite nanopowder in water-alcohol liquid. After drying the matrix had been filled with grits. The last consisted of bounded nanoparticles and had open 50 % porosity with pore size of about 20 nm estimated by scanning electron microscopy. The BET method, optical and transmission electron microscopy and tomography were employed to investigate nanopowders itself and dried composite samples for specific surface, primary nanoparticles' size, the pores' size and 3D distribution of grits in matrix. The samples were tested as noise protection materials using acoustics procedure, as separately as in layered compositions with each other. The transfer matrix method and the original acoustic duct system were consumed to measure the values of sound absorption ratio and transmission loss. The results show that this approach provides additional appearance in the foam material of the sound-energy absorbing and scattering points to control range and level of the noise protection. The effective range of the protection was extended from the high frequencies, 2.0-6.3 kHz, to the lower ones, 0.5-1.6 kHz what can help to create wide frequency band protective materials. The absorption ratio was increased by 60-100% irrelative of the filler type and thickness of the layered material, and the transmission loss was increased by 20-22 dB. The main reason of sound energy loss in hybrid materials studied is the special regime of sound wave propagation in nanopores. This research was supported by a 2017 grant of the Russian Science Foundation, project no. 17-19-01389.