Small Amount Of Carbon Nanotubes Research Articles

Facile synthesis of graphitic mesoporous carbon materials from sucrose

A one-step catalytic carbonization approach has been developed to prepare graphitic mesoporous carbon, using iron (III) nitrate as the graphitization catalyst and the template for creating pores. The porosity, degree of graphitization, and morphology of the resultant carbon products have been investigated as a function of the carbonization temperature and the dosage of iron (III) nitrate. The results showed that graphitic mesoporous carbon with a Brunauer–Emmett–Teller surface area of 198 m2/g and a high degree of graphitization was prepared at a carbonization temperature of 700 °C with a molar ratio of iron (III) nitrate to sucrose of 1.0. Moreover, a small amount of carbon nanotubes could be observed in the graphitic mesoporous carbon. The origin of the mesopores and the formation of graphitic carbon are discussed in terms of the evolution of CO2, CO, H2, and CH4, produced during the carbonization process.

Carbon Nanotubes with Carbon Blacks as Cofillers to Improve Conductivity and Stability.

In this study, a simple solution-mixing method is used to develop a kind of excellent flexible, electrically conductive adhesives (ECAs). Carbon nanotubes (CNTs) and carbon blacks (CBs) as cofillers were added into Ag-based pastes. The use of the two fillers is due to the consideration that these two materials may provide positive synergistic effects for improving the conductivity of ECAs. The conductivity, flexibility, cyclability, and oxidation resistance of ECAs with different contents of carbon fillers were studied. It was found that a small amount of CNTs or CBs can dramatically improve the ECAs’ conductivity. Solution-mixing method brings excellent carbon nanofiller dispersion in polymer matrix. Highly dispersed CNTs and CBs among the Ag flakes formed three-dimensional conducting networks to improve the conductivity of ECAs. The conductivity of ternary hybrid ECAs (with addition of 3 wt % CNTs and 2 wt % CBs) with a low content of 55 wt % Ag flakes is higher than that of the ECAs filled with only the Ag content over 65 wt %. Meanwhile, by selecting thermoplastic polyurethane resin as the matrix, the ECAs exhibited excellent mechanical compliance. The resistivity did not change when the ECAs were bended at a 60% flexural strain or pressed under 1200 kPa. Additionally, the adhesion strength of the new composited ECAs is better than that of a commercial ECA (Abletherm 3188). Further, no obvious conductivity change was observed when the sample was stored in ambient air condition at 80 °C and 60% relative humidity (60%) for 15 days.

Enhanced thermoelectric properties of the Lu-doped and CNT-dispersed Bi2Te3 alloy

Bi2Te3 and Lutetium-doped Lu0.1Bi1.9Te3 nanopowders were prepared by the hydrothermal method. Different amounts of carbon nanotubes (CNTs) were dispersed into Lu0.1Bi1.9Te3 nanopowders and hot pressed into bulk samples with nominal chemical formula of Lu0.1Bi1.9Te3 + xwt% CNT (x = 0, 0.05, 0.1, 0.5, 1) to assess the effects of lutetium doping and CNT dispersing on the thermoelectric properties. The electrical resistivity decreased because of the increase of the carrier concentration and carrier mobility at a low CNTs content. Herein, a small amount of CNTs were used as conducting filler to provide a free path of carriers which would lead to an increase of carrier mobility, though a large number of CNTs mainly played an energy-filtering effect. The thermal conductivity of Lu0.1Bi1.9Te3 + xwt% CNT nanocomposite showed an evident decrease, which resulted from the enhanced phonon scattering by the point defects caused by Lu doping and the interfaces between Lu0.1Bi1.9Te3 and CNTs. Due to the decrease in the electrical resistivity and thermal conductivity, the figure of merit (ZT) of Lu0.1Bi1.9Te3 + 0.05 wt% CNT nanocomposite was higher than that of Bi2Te3 and Lu0.1Bi1.9Te3 when the temperature was below 473 K.

High-mechanical-strength polyimide aerogels crosslinked with 4, 4′-oxydianiline-functionalized carbon nanotubes

Polyimide (PI) aerogels are among the most promising organic aerogels as thermal insulation materials, but brittle compressive strength severely limits their practical applications. Herein, we develop a novel procedure to prepare lightweight and strong PI aerogels crosslinked with 4,4′-oxydianiline (ODA)-functionalized carbon nanotubes (CNTs). PI gels could be produced by cross-linking anhydride capped polyamic acid oligomers, followed by chemical imidizing. CNTs, treated through ODA functionalization, not only provide affinity with solvents, but also react with terminal anhydride groups of PAA to form strong covalent bonding with polymer chains. These modified CNTs could serve both as rigid crosslinker and linear reinforcement, which can effectively suppress the shrinkage of aerogels during preparation process. The obtained aerogels possess developed mesoporous structure with density as low as 0.107–0.121 g cm−3. The addition of only a small amount of CNTs could increase the mechanical properties of PI aerogels drastically, e.g. a 19-fold increase in Young's modulus and 15-fold increase in yield strength. The addition of CNTs could also improve thermal stability, with only a slight increase in thermal conductivity from 0.018 W m−1 K−1 to 0.023 W m−1 K−1 at room temperature. These high-mechanical-strength aerogels with high thermal stability and low thermal conductivity render them potential candidates for various aerospace applications.

Flutter of delaminated three-phase nano-composite beam-plates

ABSTRACTIn this article the supersonic flutter instability of delaminated carbon nanotube reinforced three-phase composite plate is investigated. The classical laminate plate theory and piston aerodynamic theory are developed to construct the governing equation of delaminated three-phase nano-composite plates. The effective material properties are obtained using Halpin-Tsai relation and rule of mixture. The effects of different parameters including carbon nanotubes (CNTs) weight percentage, fiber volume fraction, CNTs aspect ratio and different fiber orientation on flutter pressure of delaminated reinforced composite plates are considered. According to the results, appending small amount of CNTs (4% wt) into the matrix epoxy can improve the flutter critical pressure by 33% in comparison to the neat matrix epoxy.

CNTs-added PMNT/PDMS flexible piezoelectric nanocomposite for energy harvesting application

ABSTRACTThe flexible piezoelectric nanocomposites based on lead magnesium niobate titanate [Pb(Mg1/3Nb2/3)0.65Ti0.35O3; PMNT] particles in polydimethylsiloxane (PDMS) matrix were fabricated and characterized. PMNT powders are synthesized using the columbite precursor method. PMNT/PDMS flexible nanocomposites are then prepared by spin casting technique, where a small amount of carbon nanotubes (CNTs) is added into the PMNT/PDMS composite to enhance cross-links between PMNT particles and PDMS matrix. The phase and microstructure of the nanocomposite are investigated by using X-ray diffraction and scanning electron microscope (SEM). The electromechanical behavior is evaluated by using an autonomous pneumatic actuator. The flexible composite, occupying approximately 300 mm2, is capable of generating an open-circuit voltage (Voc) of 2.83 ± 0.24 V and a short-circuit current (Isc) signal of 0.33 ± 0.01 µA across 10 Ω resistor under mechanical load of 300 N. The generated electrical charges are 29026 pC. The relative dielectric constant is measured at 10 kHz and found to be 6.76 ± 1.15. The piezoelectric PMNT/PDMS composite can potentially be used in a variety of applications such as wearable sensors, actuators, and energy harvesting for converting kinetic energy into useful electrical energy.

Carbon nanotube-based benzyl polymethacrylate composite monolith as a solid phase extraction adsorbent and a stationary phase material for simultaneous extraction and analysis of polycyclic aromatic hydrocarbon in water

A composite of multi-walled carbon nanotubes incorporated into a benzyl methacrylate-co-ethylene dimethacrylate porous monolith was prepared, characterized and used as solid phase adsorbent and as stationary phase for simultaneous extraction and separation of ten polycyclic aromatic hydrocarbons, followed by nano-liquid chromatography analysis. The extraction and chromatographic parameters were optimized with regard to the extraction efficiency and the quality of chromatographic analytes separation. Under the optimized conditions, all PAHs were separated in 13 min with suitable resolution values (Rs = 1.74–3.98). Addition of a small amount of carbon nanotubes (0.1% with respect to monomers) to the polymerization mixture increased the efficiency for the separation column to over 41,700 plates m−1 for chrysene at flow rate of 0.5 μL min−1. The method showed a wide linear range (1–500 μg L−1 with R2 more than 0.9938), acceptable extraction repeatability (RSDs < 6.4%, n = 3) and reproducibility (RSDs < 12.6%, five parallel-made solid phase extraction cartridges) and satisfactory detection limits (0.02–0.22 μg L−1). Finally, the proposed method was successfully applied to the detection of polycyclic aromatic hydrocarbons in environmental water samples. After a simple extraction procedure with preconcentration factor equal to 100, the average recovery values in ultra-pure, tap and sea water samples were found to be in the range 81.3–95.4% with %RSD less than 6.4. Again, the presence of carbon nanotubes (0.3% relatively to monomers) in native polymer enhanced the extraction performance for the solid phase adsorbent up to 78.4%. The application of the monoliths modified with CNTs in extraction and nano-scale liquid chromatography for analysis of environmental samples offered several advantages; it demonstrated an acceptable precision, low detection limits, good reproducibility, satisfying recoveries and wide dynamic linear ranges.

Design of micro-nanostructured Mn2O3@CNTs with long cycling for lithium-ion storage

Micro-nanostructured Mn2O3@CNTs materials have been successfully synthesized via a carbonate precursor route: MnCO3 ellipsoids precursor were first prepared via a facile hydrothermal approach, and treated by KMnO4 and HCl solutions, then a mesoporous intermediate obtained, followed by heat-decomposition at 500 or 700 °C. After mixed with a small amount of carbon nanotubes, Mn2O3@CNTs materials were used as anodes for lithium ion batteries. The sample annealed at 700 °C exhibits a micro-nanostructured architecture which shows superior electrochemical performance, ex., 802 mA h g−1 after 200 cycles at a current density of 200 and 486 mA h g−1 after 1000 cycles at 1000 mA g−1. This long-term cycling performance depends on the micro-nanoscaled structure that mixed excellent with carbon nanotubes which powers electrolyte penetration and Li+ transport.

Carbon nanotubes induced microstructure and property changes of polycarbonate/poly(butylene terephthalate) blend

Polycarbonate/poly(butylene terephthalate) (PC/PBT) blends exhibit wide applications in many fields. However, the blends usually exhibit poor mechanical and thermal properties because of the transesterification reaction occurred between molecules of the blend components. In this work, a small quantity of carbon nanotubes (CNTs) was introduced into the PC/PBT blend to prepare the ternary blend composites with balanced macroscopic properties. The dispersion of CNTs in the blend composites and the microstructural changes induced by CNTs were comparatively investigated. The results demonstrated that CNTs exhibit relatively homogeneous dispersion in the blend composites. Specifically, at relatively high content, CNTs form the percolated network structure. The crystallization ability of the PBT component is greatly enhanced with the aid of the nucleation effect of CNTs. Mechanical property measurements showed that CNTs exhibit strengthening and toughening effects on the PC/PBT blend, especially incorporating 2 wt% CNTs leads to the dramatic increase of tensile ductility. Further results showed that the blend composites also exhibit excellent antistatic performance. It is believed that the simultaneously improved fracture toughness and antistatic performance endow the blend composites with more potential applications.

Carbon Nanofibers Loaded with Carbon Nanotubes and Iron Oxide as Flexible Freestanding Lithium-Ion Battery Anodes

We demonstrate the fabrication of flexible electrospun carbon nanofibers (CNFs) containing uniformly distributed carbon nanotubes (CNTs) and iron oxide (FeOx) nanoparticles (NPs) as a composite material for lithium-ion battery (LIB) anodes. The uniform incorporation of CNTs and FeOx NPs within the CNFs was confirmed by transmission electron microscopy. Embedding even a small amount of CNTs (0.1wt%) in the CNFs increased the LIB performance by a factor of two compared with pure CNFs. The specific capacity was also increased, by 25%, when an iron source (iron (III) acetylacetonate) was added at a concentration of 2wt%. The FeOx-CNT/CNF electrode maintained a capacity of 1008 mAh∙g−1 at a current density of 100 mA∙g−1 after 100 cycles. Further, the high-performance anode material was freestanding, flexible, and lightweight. This makes it suitable for next-generation LIBs, which must deliver high power over long periods while also being light and flexible.

Co-production of hydrogen and carbon nanotubes from the decomposition/reforming of biomass-derived organics over Ni/α-Al2O3 catalyst: Performance of different compounds

Four types of biomass-derived organics (toluene/1-methylnaphthalene/phenol/ethanol) were catalytically decomposed and steam reformed over Ni/α-Al2O3 for co-production of hydrogen and carbon nanotubes (CNTs). In the decomposition reaction, the oxygen functional group in phenol and ethanol promoted the co-production of hydrogen and CNTs, while a small amount of toluene and 1-methylnaphthalene were cracked to hydrogen and amorphous carbon. In the reforming reaction, the yields of hydrogen and CNTs sharply increased. More than 2000mmol/(g-cata∗h) of H2 and 260mg/(g-cata∗h) of CNTs were produced after the reforming of toluene and ethanol. However, 1-methylnaphthalene was difficult to be reformed and small amount of CNTs were formed. The organics with low molecular weight and low degree of unsaturation conduced to the formation of hydrogen and CNTs. The growth of CNTs on Ni/α-Al2O3 mainly follows the tip-growth mechanism. The diameter distribution of CNTs is not only influenced by Ni particle size, but also related to the different organics and steam addition.

Carbon nanotube-graphene nanosheet conductive framework supported SnO2 aerogel as a high performance anode for lithium ion battery

Tin oxide (SnO2) based materials are considered promising anodes for high-energy lithium ion batteries (LIBs). However, significant challenges including low initial coulombic efficiency, poor cycling stability and low rate capability are still hindering their practical applications. Effectively constructing a conductive material structure plays a vital role in improving the electrochemical performance of tin based composite anodes for LIBs. In this work, we utilize carbon nanotube-graphene nanosheet with 3D conductive framework to fabricate a SnO2/carbon nanotube-graphene nanosheet (SnO2/CNT-GN) aerogel composite, in which a small amount of carbon nanotube is introduced to increase the electronic transportation by interconnecting the independent porous graphene structure. In addition, the synergistic interplay between high mechanical property of CNT and flexibility of graphene significantly enhance the stability of SnO2/CNT-GN composite. As a result, the SnO2/CNT-GN composite exhibit a very decent cycling stability, retaining a stable specific capacity of 809mAhg−1 (87% capacity retention) after 100 cycles at 0.2Ag−1, as well as an excellent rate capability, delivering 787mAhg−1 even at a high current density of 5Ag−1.

Constructing a continuous amorphous carbon interlayer to enhance dielectric performance of carbon nanotubes/polyvinylidene fluoride nanocomposites

Carbon nanotubes (CNTs) based percolative polymer nanocomposites own a high dielectric constant at a small amount of CNTs. However, CNTs are easy to connect with each other directly in the vicinity of percolation threshold (fc), which unavoidably leads to an abrupt increase in dielectric loss. Herein, we propose a facile way to fabricate core-shell structured CNTs@amorphous carbon (CNTs@AC) hybrids by chemical vapor deposition (CVD). The CNT@AC hybrids were subsequently integrated into polyvinylidene fluoride (PVDF) matrix to fabricate CNTs@AC/PVDF dielectric nanocomposites by the combination of solution casting and extrusion-injection procedures. The uniform AC shell provides an insulative interlayer for the adjacent CNTs, which not only hinders the direct contact of CNTs but also improves the dispersibility of CNTs in PVDF matrix. Compared with pristine CNTs (P-CNTs)/PVDF nanocomposites, the fc increases from 7.16 vol % to 11.81 vol % and the dielectric loss decreases from 83.66 to 1.35 for the CNTs@AC-60/PVDF nanocomposites, which indicates that the percolation behavior is delayed. The results indicate that the influence of AC interlayer on the dielectric performance of the nanocomposites after percolation is much more evident than that before percolation. All these results demonstrate that this strategy is effective to enhance the dielectric performance of polymer nanocomposites and the design concept could be extended to other carbon hybrids materials.

PREPARATION AND CHARACTERIZATION OF NATURAL GLUES WITH CARBON NANOTUBES

The data presented in this work has been obtained from experimental research aiming towards the usage of natural resources of the National Park of Sila in Calabria, Southern Italy. Such resources are: Laricio pine resin, beeswax, mineral inert and charcoal to make natural glues. Furthermore, research has been done to find out if by using small quantities of carbon nanotubes, the strength of adhesion of prepared glues improves. Raw materials were characterized by physico chemical techniques. In particular, the Laricio pine resin was characterized through the NMR techinique. The data obtained have shown that each utilized component plays a specific role: the pine resin on the fundamental binding properties, the beeswax on the plasticity of the material, the coal and the mineral inert on raising the melting temperature, the carbon nanotubes on improvement of the adhesion resistance.

An Overview of Processing and Properties of CU/CNT Nano Composites

Carbon nanotubes (CNTs) are known for their extraordinary mechanical, electrical and thermal properties. These properties make them ideal reinforcements in the metal matrix. Particularly, the combination of Cu/CNT is interesting in view of excellent thermal, electrical and physical properties of copper. In this overview, the reports on Cu/CNT composites are critically analyzed with respect to the process techniques, mechanical and tribological properties. Powder metallurgy coupled with spark plasma sintering is found to be a most widely used process to fabricate Cu/CNT composites. Comparatively, a small amount of CNTs is sufficient to improve the properties of composites as against the conventional micron size particle reinforced composites. The strength, wear resistance and corrosion resistance of the composites increase significantly with an increase of volume fraction of CNTs. The density and thermal conductivity reduce with an increase of CNTs. There exists a critical volume fraction above that both the mechanical properties and the thermal conductivity are drastically reduced due to the problems of CNTs agglomeration and the increase of process related defects such as porosity, delamination and so on. Fracture surface features of Cu/CNT composites show that the fracture mode transits from ductile to brittle fracture with an addition of CNTs.

Carbon nanotubes induced brittle-ductile transition behavior of the polypropylene/ethylene-propylene-diene terpolymer blends

Brittle-ductile transition is a well-known phenomenon in the elastomer-toughened polymer blends, and it is usually used to value the toughening efficiency of the elastomers. In this work, a small quantity of carbon nanotubes (CNTs) were introduced into the polypropylene/ethylene-propylene-diene terpolymer (PP/EPDM) blends to investigate the effect of CNTs on the brittle-ductile transition of the blends. The mechanical properties, morphologies and the crystallization behaviors of samples were comparatively investigated. The results showed that CNTs not only enhanced the impact strength of the materials but also promoted the occurrence of brittle-ductile transition at relatively low EPDM content. The crystallization and melting behaviors of PP matrix were not apparently influenced by CNTs, which could be attributed to the selective localization of CNTs in the EPDM component. Further results demonstrated that the toughening efficiency of CNTs in the blend composites was dependent upon the matrix ligament thickness (τ), and there was an appropriate range of τ (0.85–1.15 μm), at which CNTs exhibited high toughening efficiency. This work provides new insight on the toughening effect of CNTs in the immiscible polymer blends.

Insulator-to-conductor transition in liquid crystal-carbon nanotube nanocomposites

A small quantity of carbon nanotubes (CNTs) was dispersed in a liquid crystal (LC) and the LC + CNT hybrid in the isotropic phase was found to exhibit an insulator-to-conductor transition when an external electric field was applied. This effect was probed by measuring the resistance of the system as a function of applied voltage across the LC cell. In an LC + CNT hybrid, the LC molecules self-assemble themselves at the CNT surface due to π-π electron stacking, creating pseudonematic domains (PNDs) surrounding the CNTs. These CNT-embedded PNDs interact with the external electric field even in the isotropic phase of the LC. When the external field is applied, the PND-encapsulated CNTs start to rotate along the field and form wires due to their natural tendency of entanglement. The CNT-wires eventually short the two electrodes of the LC cell, manifesting an insulator-to-conductor transition in the LC + CNT hybrid. Additional studies revealed that the cell spacing and the CNT-concentration had a significant impact on the threshold voltage across the LC cell for the insulator-to-conductor transition process.

Optimization of the sealing performance in transient conditions of rubber based hybrid nanocomposites by carbon nanotubes, as assessed by a tailored recovery test

A key property of rubbers for sealing applications is their ability to rapidly recover the deformation during a fast movement of the counterparts, occurring in a transient deformation phase. In this work, a simple experimental test method (recovery test) is put forward to mimic the transient phase and to get insight into the behavior of the material during such phase. The effect of the addition of small quantities of carbon nanotubes (CNT) to a carbon black filled nitrile butadiene rubber on the sealing ability of the material was studied. The recovery tests show that the overall recovery behavior is related mostly to the material stress relaxation behavior, while the recovery behavior at very short times, which is indicative of the performance during a transient deformation phase, is strongly influenced by the material elastic modulus and, therefore, it is improved by the presence of CNT in the elastomeric composite.

Hybrid network structure and thermal conductive properties in poly(vinylidene fluoride) composites based on carbon nanotubes and graphene nanoplatelets

A small quantity of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) were introduced into the poly(vinylidene fluoride) (PVDF)/GNP and PVDF/CNT composites, respectively, to prepare the corresponding ternary PVDF/CNT/GNP and PVDF/GNP/CNT composites. The results demonstrated that adding CNTs into the PVDF/GNP composites greatly promoted the formation of the hybrid network structure of fillers. This was much different from the scenario that adding GNPs into the PVDF/CNT composites. GNPs and CNTs exhibited excellent nucleation effects for the crystallization of PVDF matrix; however, the variation of the PVDF crystallinity was small. Adding CNTs into the PVDF/GNP composites greatly enhanced the electrical conductivity of the PVDF/CNT/GNP composites. This was also different from the scenario of the PVDF/GNP/CNT composites. Furthermore, the PVDF/CNT/GNP composites exhibit higher thermal conductivity and higher synergistic efficiency compared with the PVDF/GNP/CNT composites. The conductive mechanisms and the synergistic effects of the ternary composites were then analyzed.

Scaffolds based on hyaluronan and carbon nanotubes gels.

Physico-chemical and mechanical properties of hyaluronic acid/carbon nanotubes nanohybrids have been correlated with the proportion of inorganic nanophase and the preparation procedure. The mass fraction of -COOH functionalized carbon nanotubes was varied from 0 to 0.05. Hyaluronic acid was crosslinked with divinyl sulfone to improve its stability in aqueous media and allow its handling as a hydrogel. A series of samples was dried by lyophilization to obtain porous scaffolds whereas another was room-dried allowing the collapse of the hybrid structures. The porosity of the former, together with the tighter packing of hyaluronic acid chains, results in a lower water absorption and lower mechanical properties in the swollen state, because of the easier water diffusion. The presence of even a small amount of carbon nanotubes (mass fraction of 0.05) limits even more the swelling of the matrix, owing probably to hybrid interactions. These nanohybrids do not seem to degrade significantly during 14 days in water or enzymatic medium.