Layered and Scrolled Nanocomposites with Aligned Semi-Infinite Graphene Inclusions at the Platelet Limit

Technology

The first fabrication method described by this invention uses polycarbonate (PC) as the polymer matrix and chemical vapor deposition (CVD) of graphene to generate up to 320 layers of aligned graphene/polycarbonate (G/PC) composites of 0.032 to 0.11 mm thickness. The composites have high optical transmittance, ranging from 90% at nine layers of G/PC to 58% at 36 layers and PC matrix reinforcement is the result of direct load transfer to the graphene filler, not stiffening of the PC polymer matrix. The second fabrication method uses transverse shear scrolling of single G/PC films to generate spiral nanocomposite fibers of 0.10 to 0.16 mm diameter. These fibers have elasticity and tensile strength 30 times greater than Kevlar.

Both fabrication methods described by this invention generate composites with volume fractions ranging from 0.003-0.185% and materials with substantial increase in uniaxial tensile strength and loss moduli; however, the shear scrolling method is even further capable of generating composites with volume fractions as high as 2.5%. Fibers generated using the shear scrolling method can exceed the stiffness and damping of the matrix polymer at negligible increases in weight of the G/PC composite material. This allows the shear scrolling method to generate lightweight, mechanically reinforced G/PC fibers. Finally, graphene electrical continuity is maintained during stacking and folding of the G/PC material, overcoming the electrically insulating property of the PC polymer matrix. As a result, each layer within the G/PC composite can be addressed electrically, allowing the formation of complex circuits within the material.

Problem Addressed

Inserting closely spaced and distinctly separated nanoparticles within a material, which is the fundamental requirement for strengthening materials, has proven to be exceedingly difficult. For a platelet filler such as graphene, a closely-spaced stack of aligned, semi-infinite plates of nanometer or atomic thickness is calculated to approach the limit of maximal mechanical reinforcement. Only recently has the development of methods to generate nanometer or atomic thickness films allowed for the testing of this limit of maximal mechanical reinforcement. Utilizing thin layers of molecular thickness, this invention develops two fabrication methods to generate new composite materials with the electrical and optical properties of their filler material, graphene. 

Advantages

• New composite materials combine and maintain the electrical and optical properties of their filler material
• Relatively miniscule addition of filler needed to generate materials with new combinations of mechanical reinforcement, electrical, and optical properties
• Graphene spiral fibers have 30 times greater elasticity and tensile strength than Kevlar