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.

Three-Dimensional Graphene Foam Induces Multifunctionality in Epoxy Nanocomposites by Simultaneous Improvement in Mechanical, Thermal, and Electrical Properties

“…Consequently, graphene foam is a promising filler material for developing advanced multifunctional nanocomposites. Graphene foam–polymer composites have been synthesized for a wide range of potential applications, such as strain sensors, − supercapacitors, electrochemical biosensors, fuel cells, electromagnetic interference shielding, , biocompatible scaffolds, , thermal interface materials, damping, and acoustic backing materials …”

“…Graphene foam−polymer composites have been synthesized for a wide range of potential applications, such as strain sensors, 25−28 supercapacitors, 29 electrochemical biosensors, 30 fuel cells, 31 electromagnetic interference shielding, 32,33 biocompatible scaffolds, 34,35 thermal interface materials, 36 damping, 37 and acoustic backing materials. 38 This study aims to harness desirable properties of graphene foam for developing epoxy-based composites which exhibit simultaneous improvement in thermal, mechanical, and electrical properties. It has been demonstrated that the 3D interconnected network of graphene in the epoxy matrix leads to an improvement in electrical conductivity, flexural modulus, flexural strength, and fracture toughness.…”

Harnessing Three Dimensional Anatomy of Graphene Foam to Induce Superior Damping in Hierarchical Polyimide Nanostructures

“…Graphene foam has attracted attention as a highly efficient nanofiller for polymers to enhance their properties and performance . Graphene foam based polymer composites have been fabricated for a variety of applications, such as strain sensors, supercapacitors, electrochemical biosensors, biocompatible scaffolds, electromagnetic shielding, fuel cells, microwave shielding, thermal interface materials, and as acoustic backing material . These studies clearly demonstrate the potential of GrF for developing multifunctional materials.…”

Three-Dimensional Graphene Foam Reinforced Epoxy Composites

“…GrF-polymer fuselage and wing coatings would protect against extreme weather conditions such as lightning strikes and freezing rain encountered during flight due to their superior electrical and thermal conductivities. GrF-polymers are known to be shock, vibration, and noise dampening materials leading to safer and more comfortable transit [10] . Polymer composites commonly used for commercial aircraft vehicles [11] .…”

“…Centrifugal stirring, application of vacuum force, and a type of mold casting was employed to synthesize 3D GrF-tungsten-epoxy (GrF-W-Ep) composites. Qiu et al [10] used centrifugal mixing to enhance infiltration of epoxy polymer containing tungsten spheres as a secondary nanofiller into GrF's cellular structure [10] . Epoxy was placed in the bottom of a test tube to create a smooth, flat surface on which the 3D GrF was to be placed.…”