Carbon Nanotubes In Solution Research Articles

The Stability of UV-Defluorination-Driven Crosslinked Carbon Nanotubes: A Raman Study.

Carbon nanotubes (CNTs) are often regarded as semi-rigid, all-carbon polymers. However, unlike conventional polymers that can form 3D networks such as hydrogels or elastomers through crosslinking in solution, CNTs have long been considered non-crosslinkable under mild conditions. This perception changed with our recent discovery of UV-defluorination-driven direct crosslinking of CNTs in solution. In this study, we further investigate the thermal stability of UV-defluorination-driven crosslinked CNTs, revealing that they are metastable and decompose more readily than either pristine or fluorinated CNTs under Raman laser irradiation. Using Raman spectroscopy under controlled laser power, we examined both single-walled and multi-walled fluorinated CNTs. The results demonstrate that UV-defluorinated CNTs exhibit reduced thermal stability compared to their pristine or untreated fluorinated counterparts. This instability is attributed to the strain on the intertube crosslinking bonds resulting from the curved carbon lattice of the linked CNTs. The metallic CNTs in the crosslinked CNT networks decompose and revert to their pristine state more readily than the semiconducting ones. The inherent instability of crosslinked CNTs leads to combustion at temperatures approximately 100 °C lower than those required for non-crosslinked fluorinated CNTs. This property positions crosslinked CNTs as promising candidates for applications where mechanically robust, lightweight materials are needed, along with feasible post-use removal options.

Effect of Carbon Nanotubes on Chloride Diffusion, Strength, and Microstructure of Ultra-High Performance Concrete.

This study delved into the integration of carbon nanotubes (CNTs) in Ultra-High Performance Concrete (UHPC), exploring aspects such as mechanical properties, microstructure analysis, accelerated chloride penetration, and life service prediction. A dispersed CNT solution (0.025 to 0.075 wt%) was employed, along with a superplasticizer, to ensure high flowability in the UHPC slurry. In addition, the combination of high-strength functional artificial lightweight aggregate (ALA) and micro hollow spheres (MHS) was utilized as a replacement for fine aggregate to not only reduce the weight of the concrete but also to increase its mechanical performance. Experimental findings unveiled that an increased concentration of CNT in CNT1 (0.025%) and CNT2 (0.05%) blends led to a marginal improvement in compressive strength compared to the control mix. Conversely, the CNT3 (0.075%) mixture exhibited a reduction in compressive strength with a rising CNT content as an admixture. SEM analysis depicted that the heightened concentration of CNTs as an admixture induced the formation of nanoscale bridges within the concrete matrix. Ponding test results indicated that, for all samples, the effective chloride transport coefficient remained below the standard limitation of 1.00 × 10-12 m2/s, signifying acceptable performance in the ponding test for all samples. The life service prediction outcomes affirmed that, across various environmental scenarios, CNT1 and CNT2 mixtures consistently demonstrated superior performance compared to all other mixtures.

Upscaling Thermoelectrics: Micron-Thick, Half-a-Meter-Long Carbon Nanotube Films with Monolithic Integration of p- and n-Legs.

In order for organic thermoelectrics to successfully establish their own niche as energy-harvesting materials, they must reach several crucial milestones, including high performance, long-term stability, and scalability. Performance and stability are currently being actively studied, whereas demonstrations of large-scale compatibility are far more limited and for carbon nanotubes (CNTs) are still missing. The scalability challenge includes material-related economic considerations as well as the availability of fast deposition methods that produce large-scale films that simultaneously satisfy the thickness constraints required for thermoelectric modules. Here we report on true solutions of CNTs that form gels upon air exposure, which can then be dried into micron-thick films. The CNT ink can be extruded using a slot-shaped nozzle into a continuous film (more than half a meter in the present paper) and patterned into alternating n- and p-type components, which are then folded to obtain the finished thermoelectric module. Starting from a given n-type film, differentiation between the n and p components is achieved by a simple postprocessing step that involves a partial oxidation reaction and neutralization of the dopant. The presented method allows the thermoelectric legs to seamlessly interconnect along the continuous film, thus avoiding the need for metal electrodes, and, most importantly, it is compatible with large-scale printing processes. The resulting thermoelectric legs retain 80% of their power factor after 100 days in air and about 30% after 300 days. Using the proposed methodology, we fabricate two thermoelectric modules of 4 and 10 legs that can produce maximum power outputs of 1 and 2.4 μW, respectively, at a temperature difference ΔT of 46 K.

Gate Capacitance Coupling of Double-Gate Carbon Nanotube Network Transistors.

Carbon nanotube (CNT) network channels constructed using a high-purity CNT solution for use in CNT thin-film transistors have the advantages of the possibility of requiring a low-temperature process and needing no special equipment. However, there are empty spaces between individual CNTs, resulting in unexpected effects. In this study, double-gate (DG) CNT network transistors were fabricated and measured in four different configurations to observe the capacitive coupling effects between the top gate (TG) and bottom gate (BG) in the DG structure. As a result, the electrical characteristics measured with the BG with a thicker gate oxide while floating the TG were similar to those measured with the TG with a thinner gate oxide. A comparison of the measured transfer curves showed that TG and BG were strongly coupled through the empty spaces in the channels. In addition, we evaluated the capacitance coupling effect due to changes in the CNT density, which is closely related to the empty space of the network channel. Finally, we proposed a method to determine the effective gate capacitance by considering the empty spaces between CNTs, which enabled the accurate evaluation of mobility. The effects of these materials were demonstrated by fabricating transistors using Al2O3, HfO2, and ZrO2 as TG oxide materials. By focusing on considerations based on the properties of CNT materials, our study provides valuable insights into accurate electrical modeling and potential advancements in CNT-based devices.

Mapping the Morphology of DNA on Carbon Nanotubes in Solution Using X-ray Scattering Interferometry.

Single-walled carbon nanotubes (SWCNTs) with adsorbed single-stranded DNA (ssDNA) are applied as sensors to investigate biological systems, with potential applications ranging from clinical diagnostics to agricultural biotechnology. Unique ssDNA sequences render SWCNTs selectively responsive to target analytes such as (GT)n-SWCNTs recognizing the neuromodulator, dopamine. It remains unclear how the ssDNA conformation on the SWCNT surface contributes to functionality, as observations have been limited to computational models or experiments under dehydrated conditions that differ substantially from the aqueous biological environments in which the nanosensors are applied. We demonstrate a direct mode of measuring in-solution ssDNA geometries on SWCNTs via X-ray scattering interferometry (XSI), which leverages the interference pattern produced by AuNP tags conjugated to ssDNA on the SWCNT surface. We employ XSI to quantify distinct surface-adsorbed morphologies for two (GT)n ssDNA oligomer lengths (n = 6, 15) that are used on SWCNTs in the context of dopamine sensing and measure the ssDNA conformational changes as a function of ionic strength and during dopamine interaction. We show that the shorter oligomer, (GT)6, adopts a more periodically ordered ring structure along the SWCNT axis (inter-ssDNA distance of 8.6 ± 0.3 nm), compared to the longer (GT)15 oligomer (most probable 5'-to-5' distance of 14.3 ± 1.1 nm). During molecular recognition, XSI reveals that dopamine elicits simultaneous axial elongation and radial constriction of adsorbed ssDNA on the SWCNT surface. Our approach using XSI to probe solution-phase morphologies of polymer-functionalized SWCNTs can be applied to yield insights into sensing mechanisms and inform future design strategies for nanoparticle-based sensors.

Manufacturing Scalable Carbon Nanotube-Silicone/Kevlar Fabrics.

Carbon nanotube (CNT) hybrid composites were formed by combining a CNT and silicone elastomer solution with Kevlar yarn, Kevlar fabric, and Kevlar veil materials. The integration of a CNT-silicone matrix with Kevlar yarn and fabric materials produced a composite with moderate electrical and thermal conductivity due to CNT fabric combined with the strength of Kevlar fabric or yarn. In the material synthesis, a notable difficulty was that the CNT-silicone did not bond strongly to the Kevlar. The composites passed the Vertical Flame Test ASTM D6413 and the Forced Air Oven Test NFPA 1971. These hybrid composites can have multiple applications in areas requiring favorable conductivity, strength, and flame and heat resistance. The application areas include firefighter apparel, military equipment, conductive/smart structures, and flexible electronics. The synthesis process used to manufacture CNT-silicone/Kevlar composites yielded composite sheets with an area of 2250 cm2. The process is scalable and customizable for the synthesis of CNT composites with tailored properties. Improvements in the bonding of CNT-silicone to Kevlar are being investigated.

A rapid and scalable fabrication of flexible P/C-CNTs anodes for sodium-ion battery

Flexible sodium-ion batteries (SIBs) are a prior energy supply for the future wearable electronic devices. And red phosphorus (P) with high theoretical capacity (2596 mAh/g) is regarded as an optimal candidate for SIB anode. However, the huge volume expansion of red P during the sodiation/desodiation process deteriorates the structural integrity of electrodes, resulting in the rapid capacity fading, which hinders the successful deployment of red P in the flexible SIB anodes. Herein, we propose a rapid and scalable method to fabricate the flexible P-based electrodes, which is similar with the common blade-coating method. The three-dimensional carbon nanotubes (CNTs) matrix from monodispersed CNT solution with robust mechanical strength ensures the structural integrity of the flexible electrode during the long cyclic process. As a result, the flexible P/C-CNTs electrode using as SIB anode delivers a reversible capacity (calculated based on the whole mass of the electrodes, 35 wt% P in electrode) of 442 mA h g−1 at 0.5 A g−1 after 100 cycles, together with 83 % capacity retention. And this work could propel the practical application process of flexible SIB.

Influence of carbon nanotube on the mechanical and electrical characteristics of concrete – A review

Conventional concrete, which is composed of cement, coarse aggregate, fine aggregate, water, and superplasticizer, has the disadvantages of low maximum split tensile strength and low ductility, which can lead to sudden failure. However, the use of carbon nanotubes (CNT) can improve the binding to detect cracks in the structure before it collapses, as well as increase the maximum split tensile strength and ductility. The CNT is utilized to improve the mechanical characteristics of concrete, including its compressive strength, split tensile strength, and flexural strength. In addition to self-sensing, researchers examined the impact of carbon fiber and CNT particles on the mechanical characteristics of beam specimens with the suggested reinforcement arrangement. In this review, mechanical tests such as compressive strength, split tensile strength, and flexural strength are examined to determine the impact percentage of CNT that is beneficial for enhancing the strength of concrete. The study also further reviewed the resistivity of self-sensing CNT concrete. The review explored that CNT also improves electrical properties, such as resistivity and conductivity, and thermal conductivity of cement composites. To increase the electrical conductivity of beams, CNT and chopped carbon fibers (CF) were utilized. As a Nano-material, CNT may be widely distributed in the concrete through a proper mixing strategy. Due to their high modulus of elasticity, tensile strength, and yield strain, CNTs are an appealing material for concrete reinforcement. Using ultrasonication and a superplasticizer, a solution of dispersed CNTs with exceptional workability in concrete was made because the accumulation of CNTs significantly decreased the electrical resistance. The purpose of adding CNT to concrete for the Structure Health Monitoring technique is to detect building fractures using self-sensing concrete (SHM). The research finally concludes that CNT is highly beneficial to enhance compressive strength, flexure strength, and split tensile strength.

Improved Electrical and Thermal Conductivities of Graphene–Carbon Nanotube Composite Film as an Advanced Thermal Interface Material

Thermal management has become a crucial issue for the rapid development of electronic devices, and thermal interface materials (TIMs) play an important role in improving heat dissipation. Recently, carbon−based TIMs, including graphene, reduced graphene oxide, and carbon nanotubes (CNTs) with high thermal conductivity, have attracted great attention. In this work, we provide graphene−carbon nanotube composite films with improved electrical and thermal conductivities. The composite films were prepared from mixed graphene oxide (GO) and CNT solutions and then were thermally reduced at a temperature greater than 2000 K to form a reduced graphene oxide (rGO)/CNT composite film. The added CNTs connect adjacent graphene layers, increase the interlayer interaction, and block the interlayer slipping of graphene layers, thereby improving the electrical conductivity, through−plane thermal conductivity, and mechanical properties of the rGO/CNT composite film at an appropriate CNT concentration. The rGO/CNT(4:1) composite film has the most desired properties with an electrical conductivity of ~2827 S/cm and an in−plane thermal conductivity of ~627 W/(m·K). The produced rGO/CNT composite film as a TIM will significantly improve the heat dissipation capability and has potential applications in thermal management of electronics.

Carbon nanotube-adsorptive dynamic membrane (CNT-ADM) for water purification

Membrane technology plays an important role in water purification, but there are some significant challenges such as membrane fouling and deep purification efficiency. The work proposes a carbon nanotube-adsorptive dynamic membrane (CNT-ADM), including carbon nanotube (CNT) and membrane module, to solve these problems with low operating cost and high removal efficiency. Above all, on the basis of physical adsorption and membrane separation, a CNT-ADM was prepared by applying “forward filtration” of a CNT solution on an ultrafiltration membrane surface. Then, the effects of preparation time, CNT loading amount, transmembrane pressure (TMP) and shear stress on the morphology and permeability were analyzed to evaluate the preparation performance. Pore blocking models were utilized to explain the influence of CNT loading amount on membrane fouling mechanism. The best optimized condition for CNT-ADM preparation was: agitation speed of 50 rpm, TMP of 1 bar, CNT loading amount of 55 g/m2 and preparation time of 10 min. Furthermore, the optimized CNT-ADM was employed to treat the micro-polluted water. The effects of treatment condition on the micropollutant removal rate and flux were investigated with various shear stresses, TMPs, the amounts of micropollutant and CNT. Compared with the new membrane (below 10 %), CNT-ADM displayed a significant improvement for the micropollutant removal (above 95 % for three cycles), due to the synergy of membrane separation (sustaining CNT layer, separating micropollutant and increasing adsorption time) and adsorption removal (forming CNT layer and adsorbing micropollutant). On the other hand, the adsorption behavior also could effectively reduce the direct contact between membrane and micropollutant, then decreasing membrane fouling. Afterwards, the backwash cleaning was also successfully applied to alter the adsorption saturated CNT and generate the new CNT layer. In final, the implications for CNT-ADM application were discussed. Overall, CNT-ADM exhibits the desirable micropollutant removal and strong anti-fouling capacity, and has a great potential application in the sustainable water purification.

Mixing carbon nanotubes with asphalt binder through a foaming process toward high-performance warm mix asphalt (WMA)

ABSTRACT This paper investigates mixing carbon nanotubes (CNTs) with asphalt binder through a foaming process to produce high-performance warm mix asphalt (WMA). Two different solvents of ethanol and a water-based surfactant are used to disperse the multi-walled CNTs. Initial morphological assessment of the two CNT solutions showed that a more homogenous dispersion of the CNTs was achieved using the water surfactant solution. The foaming performance, thermal, and rheological properties of the foamed asphalt mixed with different percentages of CNTs are further investigated. The test results showed that a very small amount of CNTs (0.06% ∼ 0.1% in weight of the binder) can effectively enhance the foaming performance for bubble stability without tangibly increasing the rheological properties of the foamed asphalt. The specific heat capacity of the foamed samples was smaller than the neat binder, whereas the glass transition temperature of the foamed samples shifted to a lower temperature as compared to that of the neat binder. The thermal conductivity of the 6% CNTs sample (0.24% wt. in asphalt binder) was improved by two-fold compared with the foamed unmodified asphalt, which indicates the potential of using CNTs in the binder for enhancement of thermal properties in asphalt pavements.

Detection of VOCs and Nitrogen Containing Gaseous Molecules By Utilizing Carbon Nanotubes (CNTs) As Sensing Materials

Carbon nanomaterials are increasingly attractive as potential candidates to make new generation of sensors due to their unique nanostructures that grant their promising electrical, chemical, and physical properties. Among the group of carbon materials, carbon nanotube (CNT) is one of the most encouraging materials because of its features of high surface-to-volume ratio and unique electronic structure. These features enable CNTs the potential to become a highly sensitive sensing material. Since our project aims on detecting bio-marks from human breath, of which the concentrations are extremely low, the nature of our sensor R&D becomes extremely challenging. Consequently, using CNTs as the sensing materials ought to be our obvious choice at this stage. This choice of carbonous materials as sensing media is also on the hope to simplify the sensor’s instability problems in our R&D effort because carbon itself is very chemically inert toward many chemicals.This presentation will serve as a report of the preliminary results from a lab experiment setting to detect several human breath related bio-marks. Sensors were chemiresistive typed and constructed through drop casting on interdigitated sensor circuit. Each sensor chip contains 8 sensor pixels, and the test bed can host maximum of 16 sensor chips simultaneously. In other words, our sensor testing chamber can embed up to 128 sensors at the same time. We then performed the sensor testing against several gases. As expected, the application of nanotechnology in using CNTs enabled us to approach high sensitivity towards to several gaseous analytes, ranging from sub-ppb to sub-ppm. Noticed that, the previous study from our lab revealed that the sensitivity of sensors could be promoted by illuminations of UV light.1 It was approved that the detection limit of nitric oxides is about 27 ppm, providing reliable and stable sensitivity. To simplify the sensor fabrication and miniaturization as well as to reduce power consumption of final sensor units, in this work, we employed an external thermal power to improve the reversibility of the sensors. Two external 375W IR bulbs were used as the heating source in this setting. A dimmer and temperature control circuitry were integrated to maintain the intended operating temperatures. Moreover, we employed our test protocols and methods by functionalizing the CNTs with carboxylic group, besides utilizing the pristine CNTs. It was resulted that this sensor array was able to detect various gaseous species, including NH3, Isoprene, acetone, etc., with relatively high sensitivity.The existence of surfactants in the CNT sensing layer lowered the conductivity of sensor pixels by a great magnitude and resulted in much reduced sensors’ sensitivities. Therefore, removing surfactants in the CNT solution was made, which dramatically improved the sensors’ electric conductivities and boosted sensors’ sensitivities. However, CNT solutions with diluted surfactants destabilize the CNTs’ aqueous suspension, and lead to the non-uniform CNTs layers. The sensor pixels fabricated by using this surfactant deficient CNTs resulted in the formation of CNT bundles or clusters. The gathering of CNTs in a non-uniform fashion could dramatically reduce the sensor’s sensitivity because the bundles would short the interdigitated circuit and disable the CNTs’ sensing capability in most other area of the sensor film. We, therefore, increased the amount of surfactant in the CNT solutions. The sensors fabricated with excess amount of surfactant exhibited highly electric resistance or even non-conductance with very low or no sensitivity. A simple washing process was then developed to wash out the surfactant, which partially resolved the non-uniformity problem. The method to completely prevent the CNT bundles from formation in sensor film is in progress.In conclusion, we developed a gas sensor array that can detect various VOCs and certain nitrogen containing gas molecules with an extremely high or reasonably high sensitivities. Through applying pristine, modified CNTs or mixtures of both into sensor fabrication, the sensing properties were enhanced under an external heating source in comparison with illumination of UV light. The best sensitivity of the sensors is achieved by removing the surfactants in the sensing films. The application of external thermal energy to help on sensors’ performance gets approved. The benefit of using thermal energy vs. UV light is also discussed. G. Chen, T. M. Paronyan, E. M. Pigos, and A. R. Harutyunyan, Scientific Reports 2, 343 (2012).

Pillar[n]arene-Mimicking/Assisted/Participated Carbon Nanotube Materials.

The recent progress in pillar[n]arene-assisted/participated carbon nanotube hybrid materials were initially summarized and discussed. The molecular structure of pillar[n]arene could serve different roles in the fabrication of attractive carbon nanotube-based materials. Firstly, pillar[n]arene has the ability to provide the structural basis for enlarging the cylindrical pillar-like architecture by forming one-dimensional, rigid, tubular, oligomeric/polymeric structures with aromatic moieties as the linker, or forming spatially “closed”, channel-like, flexible structures by perfunctionalizing with peptides and with intramolecular hydrogen bonding. Interestingly, such pillar[n]arene-based carbon nanotube-resembling structures were used as porous materials for the adsorption and separation of gas and toxic pollutants, as well as for artificial water channels and membranes. In addition to the art of organic synthesis, self-assembly based on pillar[n]arene, such as self-assembled amphiphilic molecules, is also used to promote and control the dispersion behavior of carbon nanotubes in solution. Furthermore, functionalized pillar[n]arene derivatives integrated carbon nanotubes to prepare advanced hybrid materials through supramolecular interactions, which could also incorporate various compositions such as Ag and Au nanoparticles for catalysis and sensing.

Fabrication method of flexible strain sensors with CNTs and solvents

Flexible strain sensors have received a lot of attention for their various applications, such as electronic skins, healthcare devices, and human-machine interactions. In many studies of manufacturing flexible strain sensors using carbon nanotubes (CNTs), various solvents are used to disperse CNTs. However, most studies lack explanation of the rationale for using specific solvent, which is mainly used to disperse CNTs and make CNT solution. There are studies dealing with the degree of dispersion in specific solvent of CNTs, but these studies lack information on solvents in the sensor manufacturing process. Therefore, researchers have difficulty in determining which solvent to use for CNT dispersion in their process because solvent selection varies depending on the sensor manufacturing method. Thus, the dispersion stability of CNT solutions with several solvents and the characteristics of CNT sheets made from each CNT solution were quantitatively compared. Then, the solvent suitable for an acrylic mold as well as having high dispersion stability was selected. Moreover, the flexible CNT strain sensor is developed by transferring CNTs to a flexible substrate. This sensor can be stretched up to 150% (linearity R=0.998), and the gauge factor was 26.7. It is expected to be used in various research of wearable sensors or human motion monitoring using CNT dispersion.

Precise Deposition of Carbon Nanotube Bundles by Inkjet-Printing on a CMOS-Compatible Platform.

Carbon nanotubes (CNTs) are ultimately small structures, attractive for future nanoelectronics. CNT-bundles on Si nanostructures can offer an alternative pathway to build hybrid CMOS-compatible devices. To develop a simple method of using such CNT-bundles as transistor channels, we fabricated semiconductor single-walled CNT field-effect transistors using inkjet printing on a CMOS-compatible platform. We investigated a method of producing stable CNT solutions without surfactants, allowing for CNT debundling and dispersion. An inkjet-printing system disperses CNT-networks with ultimately low density (down to discrete CNT-bundles) in Al source-drain gaps of transistors. Despite the small number of networks and random positions, such CNT-bundles provide paths to the flow current. For enhanced controllability, we also demonstrate the manipulation of CNT-networks using an AFM technique.

(Invited) Comprehensive Analysis of Electronic Properties of Carbon Nanotube Fibers

The electronic properties of various carbon nanotube (CNT) fibers that were produced by dry spinning from multi-walled CNT (MWCNT) forests, direct spinning from a CVD furnace and wet spinning of CNTs, are systematically investigated. The electrical conductivity of the fibers is significantly correlated with the effective CNT length [1], yarn density, and CNT alignment in the yarns. In contrast, the tensile strength depends more on the yarn density and the CNT alignment. The temperature dependence of the electronical properties of the CNT fibers are also investigated. Even though the constituent CNTs are very similar, the CNT fibers produced by the wet spinning of the acid treated CNT dispersion and the micelle CNT solution show different temperature dependences in the lower temperature region. The difference can be explained by the different conduction paths in the two wet-spinning fibers. Further, the iodide doping effect on the electronic property of the wet-spinning fiber produced by the acid treated dispersion is also discussed. This work was supported by a project (JPNP16010) commissioned by the New Energy and Industrial Technology Development Organization (NEDO).[1] T. Morimoto et al., ACS Nano, 8, 9897–9904 (2014).

Versatile acid solvents for pristine carbon nanotube assembly.

Chlorosulfonic acid and oleum are ideal solvents for enabling the transformation of disordered carbon nanotubes (CNTs) into precise and highly functional morphologies. Currently, processing these solvents using extrusion techniques presents complications due to chemical compatibility, which constrain equipment and substrate material options. Here, we present a novel acid solvent system based on methanesulfonic or p-toluenesulfonic acids with low corrosivity, which form true solutions of CNTs at concentrations as high as 10 g/liter (≈0.7 volume %). The versatility of this solvent system is demonstrated by drop-in application to conventional manufacturing processes such as slot die coating, solution spinning continuous fibers, and 3D printing aerogels. Through continuous slot coating, we achieve state-of-the-art optoelectronic performance (83.6 %T and 14 ohm/sq) at industrially relevant production speeds. This work establishes practical and efficient means for scalable processing of CNT into advanced materials with properties suitable for a wide range of applications.

Carbon nanotube/glass fabric composites for radar absorption

ABSTRACT Synthesized carbon nanotubes (CNTs)/glass fabrics (GFs) composites using an interface design strategy is an effective method to fabricate radar absorbing structures. In this work, CNTs/GFs composites were prepared by the electrophoretic deposition (EPD) method, and the influence of deposition voltage, deposition time, and the concentration of CNTs solution on the microstructure, electromagnetic parameters, and absorbing properties of CNTs/GFs composites was studied. The results indicated the deposition content of CNTs can be controlled by the EPD parameters and thereby realizing the regulation of absorbing performance of the CNTs/GFs composites. The minimum reflection loss (RL) of the synthesized composites can reach – 69.3 dB with the thickness of 2.3 mm when the concentration of CNTs was 1 g/L, the deposition voltage was 16 V and deposition time was 4 min. Such good absorbing performance demonstrate that the CNTs/GFs composites can be applied as a promising candidate for radar absorbing structures.

Cost-effective method for fabricating carbon nanotube network transistors by reusing a 99% semiconducting carbon nanotube solution

Carbon nanotubes (CNTs) are one-dimensional materials that have been proposed to replace silicon semiconductors and have been actively studied due to their high carrier mobility, high current density, and high mechanical flexibility. Specifically, highly purified, pre-separated, and solution-processed semiconducting CNTs are suitable for mass production. These CNTs have advantages, such as room-temperature processing compatibility, while enabling a fast and straightforward manufacturing process. In this paper, CNT network transistors were fabricated on a total of five 8 inch wafers by reusing a highly purified and pre-separated 99% semiconductor-enriched CNT solution. The results confirmed that the density of semiconducting CNTs deposited on the five selected wafers was notably uniform, even though the CNT solution was reused up to four times after the initial CNT deposition. Moreover, there was no significant degradation in the key CNT network transistor metrics. Therefore, we believe that our findings regarding this CNT reuse method may provide additional guidance in the field of wafer-scale CNT electronics and may contribute strongly to the development of practical device applications at an ultralow cost.

Optimization of Surfactant Concentration in Carbon Nanotube Solutions for Dielectrophoretic Ceiling Assembly and Alignment: Implications for Transparent Electronics.

Surfactants such as sodium dodecyl sulfate (SDS) are used to improve the dispersity of carbon nanotubes (CNTs) in aqueous solutions. The surfactant concentration in CNT solutions is a critical factor in the dielectrophoretic (DEP) manipulation of CNTs. A high surfactant concentration causes a rapid increase in the solution conductivity, while a low concentration results in undesirably large CNT bundles within the solution. The increase in the solution conductivity causes drag velocity that obstructs the CNT manipulation process due to the electrothermal forces induced by the electric field. The presence of large CNT bundles is undesirable since they degrade the device performance. In this work, mathematical modeling and experimental work were used to optimize the concentration of the SDS surfactant in multiwalled carbon nanotube (MWCNT) solutions. The solutions were characterized using dynamic light scattering (DLS) and ultraviolet–visible spectroscopy (UV–Vis) analysis. We found that the optimum SDS concentration in MWCNT solutions for the successful DEP manipulation of MWCNTs was between 0.1 and 0.01 wt %. A novel DEP configuration was then used to assemble MWCNTs across transparent electrodes. The configuration was based on ceiling deposition, where the electrodes were on top of a droplet. The newly proposed configuration reduced the drag velocity and prevented the assembly of large MWCNT bundles. MWCNTs were successfully assembled and aligned across interdigitated electrodes (IDEs). The assembly of MWCNTs from aqueous solutions across transparent electrodes has potential use in future transparent electronics and sensor devices.