Buckypaper Composites Research Articles

High-strength carbon nanotube buckypaper composites as applied to free-standing electrodes for supercapacitors

Buckypaper is an attractive candidate material for free-standing electrodes in supercapacitors due to its high electrochemical performance, light weight, and thin dimensions. At present, however, free-standing buckypapers exhibit severe limitations in terms of product quality, especially mechanical properties, which hinder their commercial applications. We here report a new method of co-packaging buckypaper with conducting polymer and thermosetting resin to fabricate cellular SWNT buckypaper materials with excellent mechanical properties, high electrical conductivity, and enhanced electrochemical properties. This new fabrication method involves wrapping of the as-prepared buckypaper with a uniform coaxial coating of polypyrrole (PPy) on the individual SWNT or SWNT bundle surfaces via a pulsed electrochemical deposition method, followed by further packaging with cyanate ester resin via a full dip infiltration. The resulting material exhibits a significant improvement in mechanical properties (improvement over unmodified buckypaper of about 400% in tensile modulus and strength) and enhanced electrochemical performance (320 F g−1 at a current density of 1 A g−1) without sacrificing electrical and thermal properties. This material is a promising candidate for use as a free-standing electrode material in small-size, light-weight, and high-temperature supercapacitors.

In situ small angle X-ray scattering investigation of the thermal expansion and related structural information of carbon nanotube composites

In-situ thermal expansion tests on a series of carbon nanotube bucky-paper composites were performed with direct heating within a synchrotron SAXS source. The impact of the samples density and morphology as well as the chemistry and degree of decoration of the carbon nanotubes on the scattering patterns were investigated and correlated to the materials macro-properties. The results demonstrate that simple densification techniques, such as acetone dipping or gold electroless deposition, could reduce greatly the displacements of the carbon nanotubes within the structure and lead to more thermally stable material.

Influence of oxidation and distribution of carbon nanotube on mechanical properties of buckypaper/epoxy composites

In order to elucidate the effects of carbon nanotube surface modification and carbon nanotube distribution on mechanical properties of the buckypaper composites, two oxidation processes were developed to prepare functionalized buckypapers. The tube geometries, the entanglement, and stacking state of the carbon nanotubes were characterized by scanning electron microscope, transmission electron microscope, and atom force microscopy. Surface morphology and volume density of the buckypapers indicate that denser and homogeneous carbon nanotube skeletons are achieved by acidification on carbon nanotube powders, while only slight change can be observed from the oxidized buckypaper. The contact angles suggest that both oxidation and carbon nanotube distribution can affect the wettability of buckypapers with epoxy at 120°C, in which homogeneous and dense carbon nanotube skeleton exhibits relatively low wettability. The tensile moduli and strengths of the functionalized buckypaper composites are increased by 20–37% and 42–68%, respectively, with respect to the pristine buckypaper composite. Further analysis demonstrates that the mechanical property improvement is caused by dense carbon nanotube network and strong adhesion of oxidized carbon nanotube to the matrix. Moreover, dynamic mechanical analysis shows that the order of magnitude of storage moduli is consistent with that of the tensile Young’s moduli for different buckypaper composites.

Manufacturing, characterization and thermal conductivity of epoxy and benzoxazine multi-walled carbon nanotube buckypaper composites

The preparation procedure of epoxy and benzoxazine multi-walled carbon nanotube buckypaper composites is described. The morphology of the buckypaper is characterized by scanning electron microscopy and porosimetry, revealing a non-uniform porous structure. The wetting behavior of epoxy and benzoxazine resins in the buckypaper surface is studied by contact angle measurements. Scanning electron microscopy photographs of the composites obtained by infiltration of the buckypaper with epoxy and benzoxazine resins and subsequent curing reveal that a good impregnation is achieved. Thermal conductivity results reveal higher values for pristine buckypaper than for the composites, which is explained by the extremely small thermal conductance of the nanotube–polymer interface. The thicker resin layer surrounding the nanotubes observed in the buckypaper/epoxy composite justifies its lower conductivity, as compared with the buckypaper/benzoxazine composite.

A Preliminary Study on the Effect of Macro Cavities Formation on Properties of Carbon Nanotube Bucky-Paper Composites.

In this study, we focus on processing and characterizing composite material structures made of carbon nanotubes (CNTs) and reproducibly engineering macro-pores inside their structure. Highly porous bucky-papers were fabricated from pure carbon nanotubes by dispersing and stabilizing large 1 μm polystyrene beads within a carbon nanotube suspension. The polystyrene beads, homogeneously dispersed across the thickness of the bucky-papers, were then either dissolved or carbonized to generate macro cavities of different shape and properties. The impact of adding these macro cavities on the porosity, specific surface area and Young’s modulus was investigated and some benefits of the macro cavities will be demonstrated.

Control of porosity and pore size of metal reinforced carbon nanotube membranes.

Membranes are crucial in modern industry and both new technologies and materials need to be designed to achieve higher selectivity and performance. Exotic materials such as nanoparticles offer promising perspectives, and combining both their very high specific surface area and the possibility to incorporate them into macrostructures have already shown to substantially increase the membrane performance. In this paper we report on the fabrication and engineering of metal-reinforced carbon nanotube (CNT) Bucky-Paper (BP) composites with tuneable porosity and surface pore size. A BP is an entangled mesh non-woven like structure of nanotubes. Pure CNT BPs present both very high porosity (>90%) and specific surface area (>400 m2/g). Furthermore, their pore size is generally between 20–50 nm making them promising candidates for various membrane and separation applications. Both electro-plating and electroless plating techniques were used to plate different series of BPs and offered various degrees of success. Here we will report mainly on electroless plated gold/CNT composites. The benefit of this method resides in the versatility of the plating and the opportunity to tune both average pore size and porosity of the structure with a high degree of reproducibility. The CNT BPs were first oxidized by short UV/O3 treatment, followed by successive immersion in different plating solutions. The morphology and properties of these samples has been investigated and their performance in air permeation and gas adsorption will be reported.

Mechanical modelling of carbon nanomaterials from nanotubes to buckypaper

A combination of molecular structural mechanics and finite element method is used to mechanically model graphene, single-walled and multi-walled carbon nanotubes, nanotube bundles, buckypaper, and buckypaper composites. The mechanical model developed is used to determine the elastic properties of these nanostructures including elastic and shear moduli. In each step, different parameters are investigated including length and orientation of graphene sheets, chirality, diameter, number of walls and length of nanotubes, number of nanotubes in bundles, porosity of buckypaper and alignment of bundles in a buckypaper composite. The results are in good agreement with both the experimental results and those reported by other researchers either experimentally or theoretically.