Reparation and characterization of carbon nanotubes coated on expanded perlite as sound absorption composite materials

A sound absorption perlite brick coated with carbon nanotubes (CNTs)/perlite slurry was prepared by two kinds of Chemical Vapor Deposition (CVD) methods (one-step method and two step method) to develop an efficient sound absorption composite material in full frequency. The characterization results indicated that CNTs delivered by two-step method are denser and purer than that delivered by one-step method. Moreover, the grain sizes played an important role in the acoustic performance of sound absorption perlite brick. The average sound absorption coefficient of sound absorption perlite bricks decreased steadily and significantly with incremental grain size. In addition, the effects of CNTs on the acoustic performance of the materials were explored. The results showed that the sound absorption coefficients of the bricks coated with CNTs/perlite slurry were all over 0.7 when the frequency was above 500 Hz, and the highest value reached 0.96, indicating a positive influence of the CNTs coatings.