Frontier technology : carbon-nanomaterial-filled multifunctional nanocomposites

An innovative technology, which enables homogeneous dispersions of carbon nanomaterials in various matrices, led to the development of multifunctional nanocomposites with outstanding performance. This technology is fundamental platform from which to design new materials that can overcome the performance limitations of conventional materials

Article  |  Fall 2018

Carbon nanomaterials, such as graphene and carbon nanotubes, exhibit superior mechanical, electrical, chemical, and thermal properties, which attract academic interest with practical applications for researchers in the fields of science and engineering. Owing to their unique and outstanding properties, carbon nanomaterials are ideal fillers for composite materials. Nevertheless, incorporation of carbon nanomaterials within monolithic materials has been limited due to their agglomeration resulting from molecular interaction.

The Composite Materials Laboratory led by Prof. Soon Hyung Hong in the Department of Material Science Engineering at KAIST has developed homogeneous dispersion technologies to overcome key issues to fabricate carbon nanomaterial filled nanocomposites. The researchers developed an innovative technology called a “Molecular Level Mixing Process”, which induces ideal homogeneous dispersion of carbon nanomaterials in matrices and strong bonding at interfaces between fillers and matrices through functionalization. Based on the innovative technology, they have developed metal, ceramic, and polymer matrix nanocomposites filled with carbon nanomaterials having significantly enhanced properties compared to conventional composites.

The scientific concept of the molecular-level mixing process is based on the homogeneous mixing and chemical bond between the nano-sized filler and the matrix phases, which result in extraordinary high-performance nanocomposites. The molecular-level mixing process is based on four steps: functionalization, chemical bonding, homogeneous mixing, and finally, formation of a filler/matrix nanostructure, as shown in Fig. 1.

 

The molecular-level mixing process resulted in significant improvement in the properties of nanocomposites when compared to those of the monolithic matrices, as shown in Fig. 2. The mechanical properties of the Graphene/Cu nanocomposites, fabricated by the molecular-level mixing process, were highly enhanced due to uniform dispersion of graphene in a Cu matrix with high adhesion energy. The elastic modulus and the yield strength of the 3 vol% Graphene/Cu nanocomposite were 137 GPa and 309 MPa, respectively, which were ≈35% and ≈93% higher than the values for pure Cu. Moreover, the nano-sized fillers of conductive graphene and ferromagnetic Ni nanoparticles in PMMA matrix were fabricated by the molecular-level mixing process for EMI shielding. The enhancement of conductivity and interfacial area between the filler and matrix improved the EMI shielding effectiveness of the graphene/Ni/PMMA nanocomposites up to 65 dB, which drastically exceeded that of metallic foil.

 

Using the innovative concept of the molecular-level mixing process, various nano-sized fillers, such as nanoparticles (0-D), carbon nanotubes (1-D), graphene and boron nitride nanoplatelets (2-D), can be dispersed homogeneously within a wide range of matrices of metals, ceramics, and polymers to synthesize the innovative multifunctional nanocomposites. The multifunctional nanocomposites could be applied in a wide scope of applications such as strong and tough structural materials, EMI shielding materials, flexible and stretchable conductors, electrodes for energy storage devices, and sensors, as shown in Fig. 3