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Abstract Carbon nanotubes (CNT) and graphene have been recognized as superior nanomaterials for high-performance, lightweight and multifunctional composites. However, non-uniform CNT/graphene dispersion within the polymer matrix, imperfect interphase between CNT/graphene and polymer matrix have hindered significant improvements in composite performance. In this study, we present a water-based grafting approach to produce polyvinyl alcohol (PVA) incorporated CNT buckypaper and CNT-graphene hybrid buckypaper composites with enhanced mechanical performance (tensile and fracture) and electrical conductivity. Our approach provides a wide range of composition for CNT (5–77 wt.%) and PVA matrix (23–95 wt.%) without compromising the uniformity of CNT dispersion and polymer matrix homogeneity. The composite buckypapers have lightweight with a density of 168 mg/cc (lighter than daily use copy papers having a density of 740 mg/cc). They show an electrical conductivity of 82 S/cm which is five orders higher than the neat PVA films (10−5 S/cm) and three orders higher than the previous reports. Overall, 600% improvement in the Young's modulus and 80% improvement in the tensile strength with an optimum PVA loading is observed. They also exhibit a strong linear piezoresistive response. The water absorption changes their mechanical (tensile and Mode I fracture), electrical and piezoresistive performance. The cross-sectional fracture SEM images are used to understand the failure mechanisms. The results suggest that the developed approach would be an effective method for the fabrication of high-performance, lightweight, multifunctional composite buckypaper. [ABSTRACT FROM AUTHOR]

It is common for as-prepared carbon nanotube (CNT) and graphene samples to contain remnants of the transition metals used to catalyze their growth; contamination may also leave other trace elemental impurities in the samples. Although a full quantification of impurities in as-prepared samples of carbon nanostructures is difficult, particularly when trace elements are intercalated or encapsulated within a protective layer of graphitic carbon, reliable information is essential for reasons such as quantifying the adulteration of physico-chemical properties of the materials and for evaluating environmental issues. Here, we introduce a microwave-based fusion method to degrade single- and double-walled CNTs and graphene nanoplatelets into a fusion flux thereby thoroughly leaching all metallic impurities. Subsequent dissolution of the fusion product in diluted hydrochloric and nitric acid allowed us to identify their trace elemental impurities using inductively coupled plasma optical emission spectrometry. Comparisons of the results from the proposed microwave-assisted fusion method against those of a more classical microwave-assisted acid digestion approach suggest complementarity between the two that ultimately could lead to a more reliable and less costly determination of trace elemental impurities in carbon nanostructured materials. [ABSTRACT FROM AUTHOR]

A microemulsion polymerization method was used to achieve better compatibility between polystyrene (PS)/multiwalled carbon nanotubes (MWCNTs) nanocomposites and the host PS matrix to form films with excellent electrical and thermal properties. The films were prepared by embedding the PS/MWCNTs nanocomposite into the PS matrix. The MWCNTs were functionalized with PS nanoparticles to avoid the phase separation problem between the filler and host matrix and to enhance the good dispersibility of MWCNTs in the PS host matrix. The confirmation of the synthesis was analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and Raman spectroscopy. The variation effect of the PS-linking density on the MWCNT was revealed by scanning electron microscopy and transmission electron microscopy. An enhancement of the thermal and mechanical properties was revealed by thermal gravimetric analysis, differential scanning colorimetric analysis, and dynamic mechanical analysis. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Abstract: Vertically aligned carbon nanotubes (CNTs) grown by water-assisted chemical vapor deposition have revealed differences in structure and morphology depending on the deposition rate of the Al buffer layer. Rearrangement of the Fe catalyst during CNT growth is mainly influenced by the buffer layer topography, which in turn depends on the buffer layer deposition rate. A higher deposition rate makes the substrate rougher and causes the growth of more aligned, low diameter CNTs with greater height. In contrast, slow deposition results in a smooth surface, which grows misaligned, large diameter CNTs with less height. Based on the results, a CNT growth model has been proposed. [Copyright &y& Elsevier]

Abstract: Self-assembled graphene/carbon nanotube (CNT)/polystyrene hybrid nanocomposites were prepared by water-based in situ microemulsion polymerization. The resulting nanocomposites were used as filler in a host polystyrene matrix to form composite films. An admixture of the two types of carbon fillers provided better improvement in the thermal and mechanical properties compared to the neat polymer. The sheet resistance decreased progressively due to the formation of an extended conjugation network with the CNT bridging the gap between the graphene sheets coated with polymer nanoparticles. The details of the analysis are presented. [Copyright &y& Elsevier]

Abstract: Aligned carbon nanotubes (CNTs) were grown on an aluminum foil laminated on a flexible stainless steel (SS) substrate. Lamination was carried out under a pressure of 10MPa with simultaneously heating at 400°C. The laminated Al foil was spray-coated with an iron chloride catalyst precursor solution and the CNTs were grown using water-assisted chemical vapor deposition at 810°C. The CNTs grew as vertically aligned forests, approximately 600μm in height, within 600s without crumpling of the Al foil. The Al foil acts as a sacrificial barrier layer to grow the CNTs. The CNTs had 2–30 walls with an inner diameter of 3–8nm. Thermogravimetric and field emission analysis of the CNTs revealed a degradation temperature and turn-on field of 643.5°C and 0.46V/μm, respectively. Transmission electron microscopy and X-ray photoelectron spectroscopy were used to analyze the Al–SS interface and chemical states. After removing the CNTs, the flexible SS substrate could be cleaned, recoated with Al and reused for CNT growth. Overall, this process is a repeatable and continuous roll-to-roll processable method that can be scaled up for industrial production. [Copyright &y& Elsevier]