title: Hierarchical Assembly of Tungsten Spheres and Epoxy Composites in Three-Dimensional Graphene Foam and Its Enhanced Acoustic Performance as a Backing Material.
abstract: Backing materials play important role in enhancing the acoustic performance of an ultrasonic transducer. Most backing materials prepared by conventional methods failed to show both high acoustic impedance and attenuation, which however determine the bandwidth and axial resolution of acoustic transducer, respectively. In the present work, taking advantage of the structural feature of 3D graphene foam as a confined space for dense packing of tungsten spheres with the assistance of centrifugal force, the desired structural requirement for high impedance is obtained. Meanwhile, superior thermal conductivity of graphene contributes to the acoustic attenuation via the conversion of acoustic waves to thermal energy. The tight contact between tungstate spheres, epoxy matrix, or graphene makes the acoustic wave depleted easily for the absence of air barrier. The as-prepared 3DG/W80 wt %/epoxy film in 1 mm, prepared using ∼41 μm W spheres in diameter, not only displays acoustic impedance of 13.05 ± 0.11 MRayl but also illustrates acoustic attenuation of 110.15 ± 1.23 dB/cm MHz. Additionally, the composite film exhibits a high acoustic absorption coefficient, which is 94.4% at 1 MHz and 100% at 3 MHz, respectively. Present composite film outperforms most of the reported backing materials consisting of metal fillers/polymer blending in terms of the acoustic impedance and attenuation.
authors.affiliation: State Key Laboratory of Robotics and System (HIT) , Harbin 150080, P.R. China.
authors.forename: Yunfeng
authors.initials: Y
authors.lastname: Qiu
authors.affiliation: State Key Laboratory of Robotics and System (HIT) , Harbin 150080, P.R. China.
authors.forename: Jingjing
authors.initials: J
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Robotics and System (HIT) , Harbin 150080, P.R. China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Condensed Matter Science and Technology Institute, Harbin Institute of Technology , Harbin 150080, China.
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.affiliation: Department of Mathematics and Materials Research Institute, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
authors.forename: Wenwu
authors.initials: W
authors.lastname: Cao
authors.affiliation: State Key Laboratory of Robotics and System (HIT) , Harbin 150080, P.R. China.
authors.forename: PingAn
authors.initials: P
authors.lastname: Hu
keywords: acoustic attenuation; acoustic impedance; backing material; centrifugation-assisted method; three-dimensional graphene