Three-dimensional (3D) chrysanthemum-like carbon nanofiber (CCNF) foam architectures were synthesized on highly porous nickel foam via a one-step ambient pressure chemical vapor deposition process by introducing a mixture of precursor gases (H2 and C2H2). The as-synthesized 3D foam architectures were characterized by scanning electron microscopy and transmission electron microscopy, which demonstrate high porosity and a densely packed nature of the hierarchical carbon nanostructures. Symmetrical electrochemical double-layer capacitors were fabricated using electrodes based on the CCNF foam architectures. Cyclic voltammetry, charge–discharge measurements, and electrochemical impedance spectroscopy were conducted to determine the performance metrics. The supercapacitors (SCs) demonstrate a high areal capacitance of 1.37 F/cm2 (gravimetric specific capacitance: 23.83 F/g), which leads to superior values for per area energy density (0.19 Wh/cm2) and power density (141.77 W/cm2). In addition, capacitance retention of ∼100% over 13,000 charge–discharge cycles demonstrates the high electrochemical stability of this type of carbon nanostructure foam for high areal capacitance SCs.

We describe the synthesis and fabrication of a graphene oxide (GO) and single-walled carbon nanotube (SWCNT) composite ink (GO–SWCNT ink) for electrochemically stable supercapacitors. Atomic force microscopy and scanning electron microscopy studies demonstrate that the obtained GO flakes are single layer with size distribution from 100 nm to 20 μm. SWCNTs are dispersed using a GO aqueous solution (2 mg/mL) with sonication support to achieve a SWCNT concentration of 12 mg/mL, the highest reported value so far without surfactant assistance. Raman spectroscopy studies indicate that the full-width at half-maximum of the G band increases with the mixing of SWCNT and GO indicating that electronic structure changes via π–π interactions of GO sheets and SWCNTs. Paper-based electrodes of supercapacitor were conveniently fabricated with GO–SWCNT composite ink via a dip casting method. By using different concentrations of SWCNT in the ink, the paper electrodes provide different capacitance values. The highest value of specific capacitance reaches 295 F/g at a current density of 0.5 A/g with a GO/SWCNT weight ratio of 1:5. The cycling stability for the GO–SWCNT paper electrode supercapacitors indicates capacitance retention of 85% over 60,000 cycles.

Multiwalled carbon nanotubes (MWNTs), due to their unique electrical conductivity and mechanical properties, have led to our interest in their application of water splitting process. This carbon nanotube-based electrode, synthesized by plasma ehanced chemical vapor deposition (PECVD), provides a ∼6 times enhancement of hydrogen production via water electrolysis compared to a graphite electrode in acidic electrolyte. Our PECVD-grown vertically aligned carbon nanotubes show good adhesion to the graphite substrate and long-term sustainability in a strong acid solution without the need for any complicated and expensive pretreatment. Furthermore, the neutral potassium phosphate solution electrolyte (KPi electrolyte) using cobalt salt as the catalyst, as was reported recently, has been used to demonstrate the long-term compatibility of the MWNTs electrode under different electrolyte. MWNTs from thermal chemical vapor deposition growth technique were also fabricated and compared with the PECVD-grown samples.

In an attempt to study the thermal transport at the interface between nanotubes and graphene, vertically aligned multiwalled carbon nanotubes (CNTs) were grown on graphite thin film substrates. A systematic cross-sectional probing of the materials’ morphology of the interface by scanning electron microscopy and high-resolution transmission electron microscopy revealed that an excellent bond existed between the nanotubes and the substrate along some fraction of interface. Imaging and electron diffraction analyses performed at the boundary reveal a polycrystalline interfacial structure. Compositional probing along the interface by energy dispersive x-ray spectroscopy revealed that there were no catalyst particles or other impurities present. The estimated interfacial thermal resistance of lower than 5–7.5 (mm2K)/W suggests that this type of CNT/graphite interface could open up multiple routes toward the designing and development of advanced thermal interface materials for aerospace and nano-/microelectronics applications.

We present results of a molecular dynamics study using adaptive intermolecular reactive empirical bond order interatomic potential to analyze thermal transport in three-dimensional pillared single-walled carbon nanotube (SWCNT)–graphene superstructures comprised of unit cells with graphene floors and SWCNT pillars. The results indicate that in-plane as well as out-of-plane thermal conductivity in these superstructures can be tuned by varying the interpillar distance and/or the pillar height. The simulations also provide information on thermal interfacial resistance at the graphene–SWCNT junctions in both the in-plane and out-of-plane directions. Among the superstructures analyzed, the highest effective (based on the unit cell cross-sectional area) in-plane thermal conductivity was 40 W/(m K) with an out-of-plane thermal conductivity of 1.0 W/(m K) for unit cells with an interpillar distance Dx = 3.3 nm and pillar height Dz = 1.2 nm, while the highest out-of-plane thermal conductivity was 6.8 W/(m K) with an in-plane thermal conductivity of 6.4 W/(m K) with Dx = 2.1 nm and Dz= 4.2 nm.

Epitaxial graphene and carbon nanotubes (CNTs) grown on SiC have shown big potential in electronics. The motivation to produce faster and smaller electronic devices using less power opened the way to a study of how to produce controlled epitaxial graphene and CNTs on SiC. Since defects are among the important tools to control the properties of materials, the effects of defects on the carbon formation on SiC have been analyzed. In this study, the effects of defects on the carbon formation on SiC have been analyzed. We produced carbon films on the surface of four different SiC materials (polycrystalline sintered SiC disks, single crystalline SiC wafers, SiC whiskers, and nanowhiskers) by chlorination and vacuum annealing with the goal to understand the effects of surface defects on the carbon structure and the SiC decomposition rate. We have shown that grain boundaries, dislocations, scratches, surface steps, and external surfaces may greatly enhance the reaction rate and affect the final structure of carbon derived from SiC.

We report on the successful synthesis of a graphene–carbon nanotube (CNT) hybrid architecture by a parallel chemical vapor deposition (CVD) of the two carbon allotropes. The carbon hybrid is a three-dimensional (3D) nanostructure with tuneable architecture comprising vertically grown CNTs as pillars and a large-area graphene plane as the floor. The formation of CNTs and graphene occurs simultaneously in a single CVD growth that we describe as a synchronous synthesis method. Unique nature of the fabrication approach contributes significantly to the quality and composure of final nanohybrid. Detailed characterization elucidates the cohesive structure and robust contact between the graphene floor and the CNTs in the hybrid structure. The functionality of the synthesized graphene hybrid structure has been demonstrated by its incorporation into a supercapacitor cell. Our fabrication approach provides an attractive pathway for the fabrication of novel 3D hybrid nanostructures and efficient device integration.

Branched core–shell hybrids of tin nanowires and carbon nanotubes have been successfully obtained on silicon substrate via a self-assembly process by chemical vapor deposition. Structure characterization unveiled that the nanostructures are the hybrids of branched single-crystalline β-Sn nanowires coated with amorphous carbon nanotubes. Detailed investigation demonstrates that the amount of introduced ethylene plays a crucial role in triggering the morphology change of the product from freestanding core–shell hybrids to branched hybrids accompanying with a thickness and surface morphology change of carbon shell. Architecture of the branched core–shell hybrids has been categorized and the mechanism has been discussed. This kind of branched hybrids may find great potential applications in building multipath nanoelectronic components, lithium-ion battery electrodes, and enhanced superconducting nanodevices as well.

In this work, we have studied the superhydrophobicity and buoyancy of two types of nanostructured surfaces: the cabbage leaf and a vertically aligned carbon nanotubes (VACNTs) carpet. The wettability of these surfaces were characterized by contact angle, tilting angle, sliding volume and sliding speed measurements. The results were correlated to the related surface topologies, which were investigated by scanning electron microscopy. Buoyancy of different surfaces has been investigated through measurements of the forces acting on the surface. Finally, we demonstrate that cabbage leaves and VACNT carpets have some common features with the water strider’s leg, better understanding the mechanisms of buoyancy related to the structural shape and size of natural or artificial nanostructures.

We report the mechanical behavior of vertically aligned carbon nanotube films, grown on Si substrates using atmospheric pressure chemical vapor deposition, subjected to in situ large displacement (up to 70 μm) flat-punch indentations. We observed three distinct regimes in their indentation stress–strain curves: (i) a short elastic regime, followed by (ii) a sudden instability, which resulted in a substantial rapid displacement burst manifested by an instantaneous vertical shearing of the material directly underneath the indenter tip by as much as 30 μm, and (iii) a positively sloped plateau for displacements between 10 and 70 μm. In situ nanomechanical indentation experiments revealed that the shear strain was accommodated by an array of coiled carbon nanotube “microrollers,” providing a low-friction path for the vertical displacement. Mechanical response and concurrent deformation morphologies are discussed in the foam-like deformation framework with a particular emphasis on boundary conditions.

Carbon microspheres (CMSs) were oxidized by a mixture of concentrated sulfuric acid and nitric acid (ratio of 3:1 by volume) to improve their surface activity. Then, poly(3-hexylthiophene):CMSs (P3HT:CMSs) composite film was prepared by spin-coating method with oxidized CMSs and P3HT mixture chloroform solution. Energy levels of oxidized CMSs were investigated by cyclic voltammetry, the morphology of the composite films was characterized by atomic force microscopy, optical performance was analyzed by ultraviolet–visible spectrophotometry and fluorescent spectrometry, and microstructures of the products were characterized by Fourier transformation infrared spectrometry and x-ray diffraction. The results indicate that suspension concentration of 30 mg/mL and spinning rate of 2500 rpm were appropriate for fabricating P3HT:CMSs composite films. Optical properties of the P3HT:CMSs blends were changed by annealing. This lays an experimental foundation for fabricating active layer of polymer solar cells with high photoelectric conversion and low cost.

The material characteristics of single-walled carbon nanotubes (SWCNTs) influence the performance of SWCNT thin-film transistors (TFTs). In this study, a density gradient ultracentrifugation method was used to sort surfactant (sodium deoxycholate)-dispersed SWCNTs by length. SWCNTs of 150 ± 33 nm and 500 ± 91 nm long were fabricated into TFTs. The results show that the performance of SWCNT-TFTs is tube length dependent. TFTs fabricated using 500-nm long tubes have maximum on/off ratio around 105 with the mobility at ∼0.15 cm2/(V s), which is much higher than that of TFTs using 150-nm long tubes. Shorter tubes need higher tube density to form semiconducting paths, leading to lower on/off ratio and high contact resistance. Surfactant-wrapped SWCNTs will bundle into ropes of different size when tube density is high. It is critical to control tube length as well as surfactant residue content to build high performance SWCNT-TFTs.