Hierarchical
Assembly of Tungsten Spheres and Epoxy Composites in Three-Dimensional
Graphene Foam and Its Enhanced Acoustic Performance as a Backing Material
posted on 2016-06-28, 00:00authored byYunfeng Qiu, Jingjing Liu, Yue Lu, Rui Zhang, Wenwu Cao, PingAn Hu
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.