Surfactant-wrapped separation methods of metallic and semiconducting single-walled carbon nanotubes (SWCNTs) can result in large changes in intrinsic physical and chemical properties due to electronic interactions between a nanotube and a surfactant. Our approach to synthesize SWCNTs with an electronic feature relied on utilizing carbon nanorings, [n] cycloparaphenylenes ([n]CPPs), which are the fundamental unit of armchair type SWCNTs (a-SWCNTs) that possess a metallic feature without any surfactants. To obtain long tubular structures from [n]CPPs, the host-guest complexes formed with well-aligned [n]CPP hosts and various fullerene guests on a silicon substrate were pyrolyzed under an ethanol gas flow at a high temperature with focused-ultraviolet laser irradiation. The pyrolyzed [n]CPPs were observed to transform from nanorings to tubular structures with 1.5–1.7 nm diameters corresponding to the employed diameter of [n]CPPs. Our approach suggests that [n]CPPs are useful for structure-controlled synthesis of SWCNTs.

We carried out a dynamic instability assessment of carbon nanotube reinforced composite (CNTRC) and carbon nanotubes/fiber/polymer composite (CNTFPC) skew plates based on the high-order shear deformation plate theory (HSDT). The multiscale interactions between carbon nanotube (CNT) ratios and skew angles on the dynamic instability for various length-thickness ratios are studied using a two-dimensional finite element model developed for this study. The results were verified by those reported in the literature show the interactions between the CNT reinforcement and skew angles in the skew laminate. Numerical examples show the importance of CNT reinforcement when assessing the dynamic instability of CNTRC and CNTFPC skew plates.

Carbon chain inserted carbon nanotubes (CNTs) have been experimentally proven having undergone pronounced property change in terms of electrical conductivity compared with pure CNTs. This paper simulates the geometry of carbon chain inserted CNTs and analyzes the mechanism for conductivity change after insertion of carbon chain. The geometric simulation of Pt doped CNT was also implemented for comparison with the inserted one. The results indicate that both modification by Pt atom on the surface of CNT and addition of carbon chain in the channel of the tube are effective methods for transforming the electrical properties of the CNT, leading to the redistribution of electron and thereby causing the conductivity change in obtained configurations. All the calculations were obtained based on density functional theory method.

We demonstrated the sensitivity of optically active single-walled carbon nanotubes (SWCNTs) with a diameter below 1 nm that were homogeneously dispersed in cement composites under a mechanical load. Deoxyribonucleic acid (DNA) was selected as the dispersing agent to achieve a homogeneous dispersion of SWCNTs in an aqueous solution, and the dispersion state of the SWCNTs were characterized using various optical tools. It was found that the addition of a large amount of DNA prohibited the structural evolution of calcium hydroxide and calcium silicate hydrate. Based on the in-situ Raman and X-ray diffraction studies, it was evident that hydrophilic functional groups within the DNA strongly retarded the hydration reaction. The optimum amount of DNA with respect to the cement was found to be 0.05 wt%. The strong Raman signals coming from the SWCNTs entrapped in the cement composites enabled us to understand their dispersion state within the cement as well as their interfacial interaction. The G and G’ bands of the SWCNTs sensitively varied under mechanical compression. Our results indicate that an extremely small amount of SWCNTs can be used as an optical strain sensor if they are homogeneously dispersed within cement composites.

The formation mechanism and photocatalytic properties of a multiwalled carbon nanotube (MWCNT)/TiO2- based nanotube (TNTs) composite are investigated. The CNT/TNT composite is synthesized via a solution chemical route. It is confirmed that this 1-D nanotube composite has a core-shell nanotubular structure, where the TNT surrounds the CNT core. The photocatalytic activity investigated based on the methylene blue degradation test is superior to that of with pure TNT. The CNTs play two important roles in enhancing the photocatalytic activity. One is to act as a template to form the core-shell structure while titanate nanosheets are converted into nanotubes. The other is to act as an electron reservoir that facilitates charge separation and electron transfer from the TNT, thus decreasing the electronhole recombination efficiency.

In the present work, we apply a technique that has been used for the expansion of graphite to multiwall carbon nanotubes (MWCNT). The nanotubes are rapidly heated for a short duration, followed by immersion in acid solution, so that they undergo expansion. The diameter of the expanded CNTs is 5-10 times larger than that of the asreceived nanotubes. This results in considerable swelling of the CNTs and opening of the tube tips, which may facilitate the accessibility of lithium ions into the inner holes and the interstices between the nanotube walls. The Li-ion storage capacity of the expanded nanotubes is measured by using the material as an anode in Li-ion cells. The result show that the discharge capacity of the expanded nanotubes in the first cycle is as high as 2,160 mAh/g, which is about 28% higher than that of the un-treated MWCNT anode. However, the charge/discharge capacity quickly drops in subsequent cycles and finally reaches equilibrium values of ~370 mAh/g. This is possibly due to the destruction of the lattice structures by repeated intercalation of Li ions.

In this study, we investigate the effect of the diffusion barrier and substrate temperature on the length of carbon nanotubes. For synthesizing vertically aligned carbon nanotubes, thermal chemical vapor deposition is used and a substrate with a catalytic layer and a buffer layer is prepared using an e-beam evaporator. The length of the carbon nanotubes synthesized on the catalytic layer/diffusion barrier on the silicon substrate is longer than that without a diffusion barrier because the diffusion barrier prevents generation of silicon carbide from the diffusion of carbon atoms into the silicon substrate. The deposition temperature of the catalyst and alumina are varied from room temperature to 150°C, 200°C, and 250°C. On increasing the substrate temperature on depositing the buffer layer on the silicon substrate, shorter carbon nanotubes are obtained owing to the increased bonding force between the buffer layer and silicon substrate. The reason why different lengths of carbon nanotubes are obtained is that the higher bonding force between the buffer layer and the substrate layer prevents uniformity of catalytic islands for synthesizing carbon nanotubes.

Carboxylated multi-wall carbon nanotubes (MWCNTs-COOH) have been used as efficient adsorbents for the removal of picric acid from aqueous solutions under stirring and ultrasound conditions. Batch experiments were conducted to study the influence of the different parameters such as pH, amount of adsorbents, contact time and concentration of picric acid on the adsorption process. The kinetic data were fitted with pseudo-first order, pseudo-secondorder, Elovich and intra-particle diffusion models. The kinetic studies were well described by the pseudo-second-order kinetic model for both methods. In addition, the adsorption isotherms of picric acid from aqueous solutions on the MWCNTs were investigated using six two-parameter models (Langmuir, Freundlich, Tempkin, Halsey, Harkins-Jura, Fowler- Guggenheim), four three-parameter models (Redlich-Peterson, Khan, Radke-Prausnitz, and Toth), two four-parameter equations (Fritz-Schlunder and Baudu) and one five-parameter equation (Fritz-Schlunder). Three error analysis methods, correlation coefficient, chi-square test and average relative errors, were applied to determine the best fit isotherm. The error analysis showed that the models with more than two parameters better described the picric acid sorption data compared to the two-parameter models. In particular, the Baudu equation provided the best model for the picric acid sorption data for both methods.

In this study, Fe-Ni bimetallic catalyst supported on kaolin is prepared by a wet impregnation method. The effects of mass of kaolin support, pre-calcination time, pre-calcination temperature and stirring speed on catalyst yields are examined. Then, the optimal supported Fe-Ni catalyst is utilised to produce multi-walled carbon nanotubes (MWCNTs) using catalytic chemical vapour deposition (CCVD) method. The catalysts and MWCNTs prepared using the optimal conditions are characterized using high resolution transmission electron microscope (HRTEM), high-resolution scanning electron microscope (HRSEM), electron diffraction spectrometer (EDS), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), and X-ray diffraction (XRD). The XRD/EDS patterns of the prepared catalyst confirm the formation of a purely crystalline ternary oxide (NiFe2O4). The statistical analysis of the variance demonstrates that the combined effects of the reaction temperature and acetylene flow rate predominantly influenced the MWCNT yield. The N2 adsorption (BET) and TGA analyses reveal high surface areas and thermally stable MWCNTs. The HRTEM/HRSEM micrographs confirm the formation of tangled MWCNTs with a particle size of less than 62 nm. The XRD patterns of the MWCNTs reveal the formation of a typical graphitized carbon. This study establishes the production of MWCNTs from a bi-metallic catalyst supported on kaolin.

The reportedly synergistic effects of carbon nanotubes (CNTs) and graphene hybrids have prompted strong demand for an efficient modifier to enhance their dispersion. Here, we investigated the ability of poly(acrylonitrile) (PAN) to overcome the van der Waals interaction of multi-walled CNTs (MWCNTs) and graphene by employing a simple wrapping process involving ultrasonication and subsequent centrifugation of PAN/MWCNT/graphene solutions. The physical wrapping of MWCNTs and graphene with PAN was investigated for various PAN concentrations, in an attempt to simplify and improve the polymer-wrapping process. Transmission electron microscopy analysis confirmed the wrapping of the MWCNTs and graphene with PAN layers. The interaction between the graphitic structure and the PAN molecules was examined using proton nuclear magnetic resonance, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and Raman spectroscopy. The obtained results revealed that the cyano groups of the PAN molecules facilitated adhesion of the PAN molecules to the MWCNTs and graphene for polymer wrapping. The resulting enhanced dispersion of MWCNTs and graphene was verified from zeta potential and shelf-life measurements.

본 연구에서는 유연성을 갖는 전극 제조를 위해 환원된 그래핀 옥사이드/단일벽 탄소나노튜 브 복합체를 금이 코팅된 PET 기판 위에 스프레이 코팅하였다. 제조된 플렉시블한 전극의 전기 용량 값 은 1 M의 황산 전해질과 100 mV s-1 의 주사속도에서 82 F g-1 으로 측정 되었으며, 이 용량 값은 500 번의 굽힘 시험 후에 38 F g-1 로 감소되는 현상을 확인 하였다. 또한, 이러한 결과는 정전류 충 방전과 전기화학 임피던스법을 포함한 전기화학적 분석 결과와도 부합하는 결과를 나타내었다. 유연성을 갖는 환원된 그래핀 옥사이드/단일벽 탄소나노튜브 복합체 전극은 500회의 반복적인 굽힘 시험 후에도 대략 50%의 초기 전기 용량 값을 유지 할 수 있었으며, 이러한 여러 가지 전기화학적 특성을 고려하여 볼 때 미래 개발 가능한 플렉시블한 에너지 저장 매체로써의 적용이 가능 하다는 점을 확인 할 수 있었 다.

본 연구에서는 유연성을 갖는 전극 제조를 위해 산 처리된 단일벽 탄소나노튜브 (Acid treated-SWCNTs)를 금이 코팅된 PET 기판 위에 스프레이 코팅하였다. 단일벽 탄소나노튜브가 가지는 단점을 보완하기 위하여 산 처리 공정을 이용하여 나노튜브에 작용기를 도입하여 분산성을 극대화 시켰 으며 전기화학적 특성을 향상 시켰다. 스프레이 기술을 이용하여 제조된 유연성을 갖는 단일벽 탄소나노 튜브 기반의 전극을 1 M의 황산 전해질에서 순환 전압 전류법, 임피던스 분광법 그리고 충·방전 시험을 통하여 전기화학적 특성을 분석 하였다. 그 결과, 응력을 가하지 않은 전극의 전기 용량값은 67 F․g-1로 측정 되었으며, 1000번의 충·방전 시험 후에는 전기 용량값이 63 F․g-1 (94 % 유지)로 감소하는 결과를 보였다. 이에 반하여, 탄소나노튜브 기반의 플렉시블 전극은 500번의 굽힘 시험 (bending test)과 6000 번의 충·방전 시험 후에는 초기의 전기 용량값 (67 F․g-1)이 유지되는 결과를 얻었다.

In this study, bulk nickel-carbon nanotube (CNT) nanocomposites are synthesized by a novel method which includes a combination of ultrasonication, electrical explosion of wire in liquid and spark plasma sintering. The mechanical characteristics of the bulk Ni-CNT composites synthesized with CNT contents of 0.7, 1, 3 and 5 wt.% are investigated. X-ray diffraction, optical microscopy and field emission scanning electron microscopy techniques are used to observe the different phases, morphologies and structures of the composite powders as well as the sintered samples. The obtained results reveal that the as-synthesized composite exhibits substantial enhancement in the microhardness and values more than 140 HV are observed. However an empirical reinforcement limit of 3 wt.% is determined for the CNT content, beyond which, there is no significant improvement in the mechanical properties.

The attachment of 2-aminobenzamide to carboxylated multi-wall carbon nanotubes (MWCNTs)- COOH was achieved through the formation of amide bonds. Then, the functionalized MWCNTs, MWCNT-amide, were treated by phosphoryl chloride to produce MWCNT-quin. The products were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, thermogravimetric analysis, derivative thermogravimetric, steady-state fluorescence spectroscopy, and solubility testing. MWCNT-quin showed photo-electronic properties, which is due to the attachment of the 4-hydroxyquinazoline groups to them as proved by steady-state fluorescence spectroscopy. This suggests intramolecular interactions between the tubes and the attached 4-hydroxyquinazoline. The toxicity of the samples was evaluated in human embryonic kidney HEK293 and human breast cancer SKBR3 cell lines, and the viable cell numbers were measured by 3-(4,5-dimethyl- 2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) after the cells were cultured for 24 h. Cellular investigations showed that the modified MWCNTs, particularly MWCNT- quin, have considerably significant toxic impact on SKBR3 as compared to HEK293 at the concentration of 5 μg/mL.

SKD11 (ASTM D2) tool steel is a versatile high-carbon, high-chromium, air-hardening tool steel that is characterized by a relatively high attainable hardness and numerous, large, chromium rich alloy carbide in the microstructure. SKD11 tool steel provides an effective combination of wear resistance and toughness, tool performance, price, and a wide variety of product forms. Adding of CNTs increased the performance of mechanical properties more. 1, 3 vol% CNTs was dispersed in SKD11 matrix by mechanical alloying. SKD11 carbon nanocomposite powder was sintered by spark plasma sintering process. FE-SEM, HR-TEM and Raman analysis were carried out for the SKD11 carbon nanocomposites.

Single-walled carbon nanotubes (SWNTs) was modified with various length of linear alkyl chains and passivated to form dielectric filler. The modified SWNTs embedded into epoxy matrix to fabricate a flexible composite with high dielectric constant. The dielectric behavior of the composite was significantly changed with various alkyl chain length(n) of pyrene. The dielectric constant of the epoxy/SWNTs composite significantly increased with respect to increase in length of alkyl chain at the frequency range from 10 to 105 Hz (n=12and18). We also found that the passivated epoxy/SWNTs composite with high dielectric constant presented low dielectric loss. The resulted dielectric performances corresponded to de-bundling of nanotubes and their distribution behavior in the matrix in terms of tail length of alkyl pyrene in the passivation layer.