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

Abstract

Three-dimensional (3D) macroporous graphene foam based multifunctional epoxy composites are developed in this study. Facile dip-coating and mold-casting techniques are employed to engineer microstructures with tailorable thermal, mechanical, and electrical properties. These processing techniques allow capillarity-induced equilibrium filling of graphene foam branches, creating epoxy/graphene interfaces with minimal separation. Addition of 2 wt % graphene foam enhances the glass transition temperature of epoxy from 106 to 162 °C, improving the thermal stability of the polymer composite. Graphene foam aids in load-bearing, increasing the ultimate tensile strength by 12% by merely 0.13 wt % graphene foam in an epoxy matrix. Digital image correlation (DIC) analysis revealed that the graphene foam cells restrict and confine the deformation of the polymer matrix, thereby enhancing the load-bearing capability of the composite. Addition of 0.6 wt % graphene foam also enhances the flexural strength of the pure epoxy by 10%. A 3D network of graphene branches is found to suppress and deflect the cracks, arresting mechanical failure. Dynamic mechanical analysis (DMA) of the composites demonstrated their vibration damping capability, as the loss tangent (tan δ) jumps from 0.1 for the pure epoxy to 0.24 for ∼2 wt % graphene foam-epoxy composite. Graphene foam branches also provide seamless pathways for electron transfer, which induces electrical conductivity exceeding 450 S/m in an otherwise insulator epoxy matrix. The epoxy-graphene foam composite exhibits a gauge factor as high as 4.1, which is twice the typical gauge factor for the most common metals. Simultaneous improvement in thermal, mechanical, and electrical properties of epoxy due to 3D graphene foam makes epoxy-graphene foam composite a promising lightweight and multifunctional material for aiding load-bearing, electrical transport, and motion sensing in aerospace, automotive, robotics, and smart device structures.

Stretchable and multifunctional strain sensors based on 3D graphene foams for active and adaptive tactile imaging

“…As a result, the MSR/ GrF/Ecoflex composite ruptures at a stress of 186.8 kPa and a stretch of 601.7%. It is reported that the GrF aids in load-bearing, increasing the ultimate tensile strength and ductility while composited with the elastic polymer [27]. Therefore, the stretchability and strength of the assembled device are combination of the two elastomer and closer to Ecoflex.…”

A Facile and Scalable Approach in the Fabrication of Tailored 3D Graphene Foam via Freeze Drying

“…The pristine freestanding GrF shown in Figure 3c offers filler properties such as ultra-low density (<4 mg/cm 3 ), enhanced surface area (~850 m 2 /g), and improved electron and phonon conduction due to reduced inter Gr sheet contact resistance [21][22][23][24]. As a result, 3D GrF has been used in producing several composite materials for applications such as scaffolds [21], strain sensors [16], vibration dampeners [12,25], supercapacitors [26], fracture-resistant materials [27], and thermal interfacing [28]. The pristine 3D GrF is often fabricated via a template-directed chemical vapor disposition (CVD) technique [24][25][26][27][28].…”

“…As a result, 3D GrF has been used in producing several composite materials for applications such as scaffolds [21], strain sensors [16], vibration dampeners [12,25], supercapacitors [26], fracture-resistant materials [27], and thermal interfacing [28]. The pristine 3D GrF is often fabricated via a template-directed chemical vapor disposition (CVD) technique [24][25][26][27][28]. Since its advent in 2011, from the trend analysis of scientific publications on CVD GrF (Figure 4, data from the web of science), it is evident that there is a tremendous interest in tapping into intrinsic properties of graphene arranged in a 3D hierarchical structure.…”

Highly sensitive strain sensors based on hollow packaged silver nanoparticle-decorated three-dimensional graphene foams for wearable electronics

“…15,16 In addition, due to the exibility and biocompatibility, graphene can be a promising material for high-performance, multifunctional wearable electronics and biomedical applications. 17,18 However, the application of graphene in practical wearable electronics is challenging due to its electrical properties under high tensile conditions. 7,15,19 Chen et al manufactured 3D interconnected graphene networks by chemical vapor deposition, embedding these networks in a polydimethylsiloxane (PDMS) matrix to produce strain sensors capable of withstanding tensile strains up to 95% and providing a gauge factor of 2.…”