Different materials have been shown to "catalyze" carbon nanotube (CNT) growth in chemical vapor deposition (CVD) when they become nano-sized particles. Catalysts, which act as a kind of "seed" for CNT growth, show two types of behavior in the CVD method; precipitation of carbon atoms from the eutectic alloy forming a kind of alloy with carbon; the fact that the catalyst remains as a solid phase and forms a carbon surface layer during the CVD process. This study examines the relationship between the iron-group and non-iron-group catalyst types and the catalyst concentration and growth time of CVD-based CNT growth via emphasizing growth mechanisms. The novelty of this work is to compare and evaluate the effects of catalyst type, concentration, and growth time, which are three critical CVD parameters, on the final nanotube morphology. It was utilized five different catalysts ( Fe2O3, Fe3O4, Nb2O5, Au, and Pt), three different growth durations (3, 5, and 7 min), and three different catalyst concentrations (2, 4, and 6 wt%) to explore the morphological differences on CNT synthesis by CVD under the same process parameters. The results demonstrated that catalyst type is the most influential parameter in CVD-based CNT synthesis, while catalyst concentration and growth time are indispensable elements for the uniformity and small diameter in the final morphology.

Acrylonitrile–butadiene–styrene (ABS) terpolymer was compounded with short carbon fiber (CF) and carbon nanotube (CNT) using a micro-extruder followed by the injection molding process. Composite samples were fabricated with loading ratios of 20 wt.% CF and 0.1, 0.5 and 1.0 wt.% of CNT. Mechanical, electrical, thermo-mechanical, thermal, melt-flow, and structural investigations of ABS-based composites were conducted by performing tensile, impact, hardness, and wear tests, conductive atomic force microscopy (AFM), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA), melt flow rate test (MFR), scanning electron microscopy (SEM) characterization techniques, respectively. According to mechanical test data of resultant composites including tensile and impact test findings, CNT additions led to the remarkable increase in tensile strength and impact resistance for CF reinforced ABS composites. The formation of synergy between CNT nanoparticles and CF was confirmed by electrical conduction results. The conductive path in ABS/CF composite system was achieved by the incorporation of CNT with different loading levels. SEM micrographs of composites proved that CNT nanoparticles exhibited homogeneous dispersion into ABS matrix for lower loadings.

We investigated the electronic and mechanical properties of single-walled carbon nanotubes (SWCNTs) with different tube diameters using density functional theory (DFT) and molecular dynamics (MD) simulation, respectively. The carbon nanotubes’ electronic properties were derived from the index number ( n 1 , n 2 ), lattice vectors, and the rolled graphene sheet orientation. For (6,1) SWCNT, ( n 1-n 2)/3 is non-integer, so the expected characteristic is semiconducting. We have considered (6,1) Chiral SWCNT with different diameters ‘d’ (4.68 Å, 4.90 Å, 5.14 Å, 5.32 Å, 5.53 Å) corresponds to respective bond lengths ‘  ’ (1.32 Å, 1.38 Å, 1.45 Å, 1.50 Å and 1.56 Å) and then analyze the electronic properties from the Linear Combination of Atomic Orbitals (LCAO) based on DFT. We have used both the DFT-1/2 and GGA exchange energy correlation approximations for our calculation and compared the results. In both cases, the energy bandgap is decreasing order with the increase in bond lengths. The lowest value of formation energy was obtained at the bond length  = 1.45 Å ( d = 5.14 Å). For the mechanical properties, we have calculated Young’s modulus using molecular dynamics (MD) simulations. From our calculation, we have found that the (6,1) SWCNT with bond length 1.45 Å ( d = 5.14 Å) has Young’s modulus value of 1.553 TPa.

Multi-walled carbon nanotubes (MWCNTs) grown by chemical vapor deposition retain the residual catalyst particles from which the growth occurred, which are considered a detriment to MWCNTs’ performance, especially electrical conductivity. The first direct measurements have been made of the electrical transport through the catalyst cap into the MWCNT using nanoscale 2-point-probe to determine the effects of the catalyst particle’s size and the diameter ratio with its associated MWCNT on the electrical transport through the catalyst cap as compared to the inherent conductivity of the MWCNT. The MWCNT diameter is independent of the catalyst size, but the ratio of the catalyst cap diameter to MWCNT diameter (DC/DNT) determines the conduction mechanism. Where DC/DNT is greater than 1 the resulting I–V curve is near ohmic, and the conduction through the catalyst ( RC+NT) approaches that of the MWCNT (RNT); however, when the DC/DNT < 1 the I–V curves shift to rectifying and RC+NT > > RNT. The experimental results are discussed in relation to current crowding at the interface between catalyst and nanotube due to an increased electric field.

In this study, Fe–Mo–MgO catalysts for the synthesis of carbon nanotubes (CNTs) were prepared using the combustion method and CNTs were synthesized through catalytic chemical vapor deposition. The combustion time was controlled to 0.5, 1, 2, 3, 5, 10, and 24 h in the catalyst preparation stage. The residual carbon contents after the combustion stage and the morphologies of synthesized CNTs were also analyzed. The diameter, yield, and crystallinity of the synthesized CNTs were found to remarkably vary according to the combustion time in the catalyst preparation process. The amount of residual carbon in the catalyst considerably affects the purity, crystallinity, diameter and its distribution, and wall number of CNTs. Based on the yield and crystallinity, CNTs synthesized using the catalyst with a combustion time of 3 h were determined to be the most appropriate for application in field emitters

Carbon nanotube (CNT) structures reported in the literature often have a black color with low reflectance and matt surface appearance. Only a few papers reported the high reflectance and glossy appearance of the CNT surface on a substrate. To our knowledge, no one has reported the glossy appearance of freestanding CNT. Herein, we have successfully fabricated a freestanding multi-walled CNT sheet with a glossy or mirror-like surface appearance. Raman spectroscopy confirmed that both matt and glossy freestanding CNT sheets have the same chemical composition. We found that the glossy freestanding CNT sheet has a relatively flat surface morphology compared to matt freestanding CNT sheet, as seen in the atomic force microscopy results. We attributed the glossy appearance due to a relatively flat surface morphology of the freestanding CNT sheet.

Carbon nanotube (CNT) grafted with hyperbranched poly(amidoamine) (PAMAM) dendrimer (CNTD) were used as a multifunctional curing and composite agent of polyurethane (PU) terminated with epoxy units. Amino-functionalized CNT was used as the core for grafting the first generation of PAMAM dendrimer by sequential addition of methyl acrylate and ethylenediamine. Two different epoxy-terminated PUs (PUB and PU-PMDA) were prepared from the reaction of poly(ethylene glycol), excess amounts of hexamethylene diisocyanate, and different chain extenders (1,4-butanediol for PUB and pyromellitic dianhydride (PMDA) for PU-PMDA), and subsequent end group transformation of the isocyanate groups to epoxy functionalities using glycidol. Fourier transform infrared spectra and thermogravimetric analysis (TGA) results showed that CNTD was successfully prepared. TGA thermograms revealed that thermal decomposition of composites were carried out in two main steps related to the soft and hard segments. In addition, char content and thermal stability of the composites were increased with increasing the CNTD content. Most importantly, the PMDA chain extender resulted in high thermal stability of the epoxy-terminated PU composites. X-ray diffraction and scanning and transmission electron microscopies presented morphological and structural properties of nanotubes and hybrid composites.

We report the comparative study of electronic and optical properties of (6,1) SWCNT from GGA and DFT-1/2 methods. (6,1) SWCNT is a low-bandgap semiconductor, which falls within ( n1 − n2)/3≠ integer. The calculated bandgaps are 0.371 eV and 0.462 eV from GGA and DFT-1/2, respectively. Thus, DFT-1/2 enhanced the electronic bandgap by 24.52%. From both GGA and DFT-1/2 approaches (6,1) SWCNT exhibits an indirect bandgap along Γ − Δ symmetry. However, the percentage change in direct–indirect bandgap is negligibly small, i.e., 4.1% and 3.7% from GGA and DFT-1/2, respectively. The refractive index measured along x-axis ( n x ) approaches unity, indicating transparent behaviour, while that along z-axis ( n z ) goes as high as ∼3.82 for photon energy 0.0 − 0.15 eV, exhibiting opaque behaviour. Again, the value of n z drops below unity at photon energy ∼0.18 eV and again approaches ∼ 1 for higher energy ranges. The optical absorption is highly anisotropic and active within the infrared region.

최근 ICT 산업의 기술혁신이 일어남에 따라 생체신호을 인식하고 이에 대해 대응을 하기 위한 웨어러블 센싱 장치에 대한 수요가 증가하고 있다. 이에 따라 본 연구에서는 단순한 함침과정을 통해 3차원 스페이서(3D spacer)직물 을 단일벽 탄소나노튜브(SWCNT)분산용액에 함침공정을 진행해 단일층(monolayer) 압전 저항형 압력 센서 (piezoresistive pressure sensor)를 개발하였다. 3D 스페이서 원단에 전기전도성을 부여하기 위해 시료를 SWCNT 분 산용액에 함침공정을 진행한 후 건조하는 과정을 거쳤다. 함침된 시료의 전기적 특성을 파악하기 위해 UTM (Universal Testing Machine)과 멀티미터를 이용해서 압력의 변화에 따른 저항의 변화를 측정하였다. 또한 센서의 전기적 특성의 변화를 관찰하기 위해 분산용액의 농도, 함침횟수, 시료의 두께를 다르게 해서 시료의 센서로서의 성능을 평가했다. 그 결과 wt0.1%의 SWCNT 분산용액에 함침공정을 2번 진행한 시료가 센서로서 가장 뛰어난 성능 을 나타냄을 알 수 있었다. 두께별로는 7mm 두께의 센서가 가장 높은 GF를 보이고 13mm 두께의 센서가 작동범위가 가장 넓음을 확인했다. 본 연구를 통해 3D spacer 원단으로 제작한 스마트 텍스타일 센서는 공정과정이 단순하면서도 센서로서 성능이 뛰어나다는 장점을 확인할 수 있었다.

In this study, a new method of rapid preparation of carbon nanotube (CNT) solution with highly dispersed morphology by free arc excitation is proposed, which shortens the time of the preparation of CNT solution with low concentration. The principle is that the high-energy flow density heat generated by the free arc makes the vaporizable substance coated on the surface of CNTs vaporize rapidly, and then generates the bulk increasing motion, which makes the CNTs aggregates dispersed, and finally forms the CNTs gas-phase dispersion monomer with high dispersion or the cross-linking morphology of few CNTs. In this paper, the influence of gum Arabic (GA) and deionized water (DI water) contents in CNTs mixed electrode on the dispersion of CNTs in different environments (gas phase and liquid phase) is explored. In the limited case of this work, the dispersion effect is better when the mass ratio of CNTs, GA and DI water is 1:0.04:3.96 in the liquid-phase environment. The preparation method reported in this work is expected to be a rapid way to obtain low-concentration nanodispersion.

In this research, carbon nanotubes(CNT) and graphene nanoplates(GnP) are deposited on the surface of carbon fibers(CF) at once. Investigating the effect between CNT and GnP on increasing the interfacial and mechanical properties of carbon fiber reinforced epoxy composites(CFRP). The cross section of the CFRP composites indicates that the GnPs/CNTs hybrid coating exhibits significantly higher mechanical performance in all coating samples. The interlayer shear strength of the GnPs/CNT hybrid coated CFRP composite was 90% higher than that of the uncoated CF composite. The flexural and tensile strength of CFRP composites using GnPs /CNT hybrid coatings were improved by 52% and 70%, respectively, compared to uncoated CF.

현대에 사용되는 콘크리트는 혼화재료 적용을 통하여 워커빌리티와 구조적 성능을 향상시킬 수 있고 극한 환경에서 적용 가능한 기능성 콘크리트로 개발되었으나 외부 요인에 의한 부식, 인장력에 취약한 구조적 한계는 콘크리트의 활용 범위를 제한하였다. 이러한 콘크리트의 단점을 해결하는 방안으로 신소재로써 각광받고 있으며 고유의 기능을 부여할 수 있는 Smart material을 활용하고자 하며 Smart material 중 하나인 탄소나노튜브는 콘크리트의 보강재 중 하나인 철근보다 더 뛰어난 역학적 성능을 보이므로 콘크리트 내 적용을 통해 콘크리트의 향상된 구조성능을 기대할 수 있다. 또 다른 Smart material중 하나인 자기치유 혼화재는 콘크리트 균열면의 앙금 반응을 통해 균열을 메움으로써 콘크리트의 균열 부분 및 내부 배근재의 부식을 최소화하고자 한다. 탄소나노튜브는 시멘트 질량의 0.1, 0.3, 0.5%, 자기치유 콘크리트는 시멘트 질량의 6, 8, 10%만큼 혼입된 콘크리트 복합체의 역학적 거동을 검토하기 위해서 압축강도 시험과 휨시험을 수행하였으며 휨시험이 종료된 시편을 수중에 넣어 0,3,7,14,21,28,56,84일간 자기치유 성능을 검토하였다. 휨시험의 경우 OPC시편과 비교하여 동일 변위에 대해 높은 하중 변화를 보였으나 취성도가 증가하였다. 자기치유 실험의 경우 탄소나노튜브의 경우 일반 OPC 시편보다 약간 향상된 자기치유 성능을 보였으나 혼입량 증가에 따른 경향성을 보이지 못하였다. 자기치유 혼화재의 경우 OPC 또는 탄소나노튜브 혼입 콘크리트보다 초기 속도면에서 느린 회복률을 보였으나 최종 회복률에서 더 우수한 결과를 보였으며 이러한 현상은 혼입율의 증가에 따라 해당 경향이 더 뚜렷히 보였다.

Although flame synthesis promises economic benefit and rapid synthesis of carbon nanotube (CNT), the lack of control and understanding of the effects of flame parameters (e.g., temperature and precursor composition) impose some challenges in modelling and identifying CNT growth region for obtaining better throughput. The present study presents an investigation on the types of carbon precursor that affect CNT growth region on nickel catalyst particles in an ethylene inverse diffusion flame. An established CNT growth rate model that describes physical growth of CNT is utilised to predict CNT length and growth region using empirical inputs of flame temperature and species composition from the literature. Two variations of the model are employed to determine the dominant precursor for CNT growth which are the constant adsorption activation energy (CAAE) model and the varying adsorption activation energy (VAAE) model. The carbon precursors investigated include ethylene, acetylene, and carbon monoxide as base precursors and all possible combinations of the base precursors. In the CAAE model, the activation energy for adsorption of carbon precursor species on catalyst surface E a,1 is held constant whereas in the VAAE model, E a,1 is varied based on the investigated precursor. The sensitivity of the growth rate model is demonstrated by comparing the shifting of predicted growth regions between the CAAE model and the VAAE model where the CAAE model serves as a control case. Midpoint-based and threshold-based techniques are employed within each model to quantify the predicted CNT growth region. Growth region prediction based on the midpoint-VAAE approach demonstrates the importance of acetylene and carbon monoxide to some extent towards CNT growth. Ultimately, the threshold-VAAE model shows that the dominant precursor for CNT growth is the mixture of acetylene and carbon monoxide. A simplified reaction mechanism is proposed to describe the surface chemistry for precursor reactions with nickel catalyst where decomposition of the ethylene fuel source into acetylene and carbon monoxide is accounted for by chemisorption.

We reported the synthesis of dendrite-like carbon nanotube-confined polymeric sulfur composite by modifying the surface of carbon nanotubes (CNTs) with trithiocyanuric acid (TTCA) and then copolymerizing with sulfur. DSC results show the successfully formation of robust chemical bonds between sulfur and TTCA modified CNTs, which effectively avoid the dissolution of polysulfide when used as cathodes for lithium–sulfur batteries. The composite with a high sulfur content of 78 wt% exhibits an initial charge capacity of 698 mAh g− 1 and the residual capacity of 553 mAh g− 1 after 1000 cycles at a rate of 1 C.

Carbonaceous materials are considered as potential adsorbents for organic dyes due to their unique structures which provide high aspect ratios, hydrophobic property, large efficient surface area, and easy surface modification. In this work, graphene nanoribbons (GNRs) were prepared by atomic hydrogen-induced treatment of single-walled carbon nanotube (SWCNTs), which inspire the idea of cutting and unzipping the SWCNTs carpets with the modified in molecules prevent because of the unfolding of the side-walls. The unfolded spaces and uniform vertical arrangement not only enhance the active surface area, but also promote the electrostatic and π–π interactions between dyes and GNRs. The improved adsorption capacity of GNRs beyond original SWCNTs can be determined by the adsorption kinetics and isotherm, which are evaluated through adsorption batch experiments of the typical cationic methylene blue (MB) and anionic orange II (OII) dye, respectively. It is shown that the adsorption kinetics follow a pseudo second-order model while the adsorption isotherm could be determined by Langmuir model. The results reveal that the maximum adsorption capacities of GNRs for MB and OII are 280 and 265 mg/g, respectively. The GNRs present the highly efficient, cost effective, and environmental friendly properties for the commercial applications of wastewater treatment.

Single C-vacancy and pyridine-like N3 defect are usually formed on the single-walled carbon nanotube (SWCNT) and they have unique properties for potential applications. In this paper, we use density functional theory to investigate the discrepancies of such two structures from the geometric and electronic aspects. Our results indicate that the existed single vacancy in the SWCNT can lead to somewhat electron localization because of the lone pair electrons; while the N3 embedded SWCNT ( N3-SWCNT) has stronger chemical reactivity and electron localization than the single vacancy SWCNT (SV-SWCNT) due to the great charge transfer between N3 group and C atom on the tube sidewall. Through the investigation of Ag-doping on the above two nano-structures, we found that the single Ag atom is much more stably adsorbed on the N3- SWCNT sidewall compared with SV-SWCNT, forming higher binding energy and higher electron transfer. Our calculation would shed light on the physicochemical property of SWCNT-based material and thus extend their potential applications in many fields.

Mechanically enhanced supramolecular carbon nanotube (CNT) films were prepared in water by employing the π-electronrich phenyl, naphthalenyl, and pyrenyl end-functionalized polyethylene oxides (PEOs) as supramolecular linkers, followed by vacuum filtration. Among them, the supramolecular CNT film produced by the pyrenyl end-functionalized PEO (PEOPy) exhibited the highest mechanical strength, which was ~ 1.5–2 times higher than that of the CNT films produced using the typical dispersant, Triton X-100, although the functionality of PEO-Py was lower than that prepared using other linkers, and the content of PEO-Py in the CNT films was lower than that obtained using Triton X-100. Fluorescence and UV–Vis spectroscopy demonstrated that the improved mechanical properties of the supramolecular CNT film result from the formation of π–π interactions between the CNT and the pyrene moieties of the PEO-Py linker. Finally, the supramolecular CNT film exhibited a 40–50 dB electromagnetic shielding efficiency through hybridization with silver nanowires.