Single-walled Carbon Nanotube Fibers Research Articles

Synergistic effects of single-walled carbon nanotube and carbon fiber on performance of conductive mortar

Single-walled carbon nanotube (SWCNT) and carbon fiber (CF) have been demonstrated to be conducive to an improved electrical conductivity of cement-based composites. However, there have been few studies on the possible hybrid use of SWCNT and CF to further promote the electrical conductivity and perhaps also other performance attributes. In this study, a trial to utilise both SWCNT and CF to produce conductive mortar was launched. A series of 20 mortar mixes featuring varying water-to-cement ratios, SWCNT contents and CF contents were tested to reveal their combined effects on fresh workability, mechanical strength, dimensional stability, electrical conductivity and microstructure. Test results exhibited that the co-addition of SWCNT and CF derived adverse effect on workability, but remarkable beneficial effects on strength, dimensional stability and electrical conductivity, and more interestingly, some combinations of SWCNT and CF showed synergistic effects. From the microscopic morphology, the agglomeration of SWCNT is an important causation for the decline in strength and dimensional stability of mortar. Finally, some mix proportions suitable for conductive mortars are proposed.

Investigation of electromagnetic interference shielding performance of ultra-high-performance mortar incorporating single-walled carbon nanotubes and steel fiber

For security amenities and key infrastructure, construction materials with extraordinary mechanical, durability, and electromagnetic interference (EMI) shielding performance are essential. This study investigates the EMI shielding performance of ultra-high performance mortar (UHPM) incorporating single-walled carbon nanotubes (SWCNT) and steel fibers. Currently, no such work is present in the existing literature. Eight mixtures were prepared with varying SWCNT dosages (0%–0.03 % by weight of cement) and steel fiber additions (1.2 % of the volume of the UHPM mixture). The performance of UHPM incorporating SWCNT and steel fibers was evaluated through flow diameter, compressive strength, flexural strength, Schmidt hardness, ultrasonic pulse velocity, EMI shielding performance, and scanning electron microscopy analysis tests. It is observed that increasing the SWCNT content enhances the compressive strength, flexural strength, ultrasonic pulse velocity, and Schmidt hardness of UHPM. The addition of steel fibers further enhances compressive (up to 22 %) and flexural (up to 92 %) strengths. In terms of the transmittance behavior, the improved EMI shielding performance of UHPM with the increasing SWCNT content is observed prominently at high electromagnetic frequencies (i.e., 2500 MHz–5100 MHz). However, the improved shielding performance is observed to be quite low, limited to 10 dB. Moreover, combining steel fibers and SWCNT enhances the EMI shielding performance of UHPM in terms of the transmittance behavior. As a result, UHPM incorporating SWCNT and steel fibers behaves as an absorbent material, shielding a significant amount of energy, approximately 45 dB, at a frequency of 5000 MHz. Based on the results, UHPM incorporating SWCNT and steel fibers can be used effectively as EMI shielding material. The findings of this study will enhance the practical applications of UHPM incorporating SWCNT and steel fibers.

Evaluating SWCNT assembly properties from the temperature dependence of electrical resistivity

We developed a theoretical model to describe the electrical resistivity in films and fibers made of single-walled carbon nanotubes (SWCNTs). The proposed model considers the formation of randomly oriented bundles of metallic and semiconducting nanotubes and takes into account the influence of temperature, while separating contributions of SWCNTs and their junctions to the total resistivity. To verify the model, we applied a powerful experimental tool – measurements of the temperature dependence of electrical resistivity of the investigated macroscopic SWCNT assemblies (pristine and doped SWCNT fibers). This allowed us to estimate various parameters of the material, such as the average length of SWCNT bundles, the acoustic phonon scattering length, and the bundle contact resistance, which are difficult to evaluate experimentally for entangled SWCNTs. The study highlights the importance of understanding the relationship between structural characteristics and electrical properties in SWCNT assemblies. The findings provide insights into optimizing the conductivity of these materials and offer a quick estimation method of the SWCNT network properties based on varying temperature measurements for future fiber and film-based applications.

Strong Connection of Single-Wall Carbon Nanotube Fibers with a Copper Substrate Using an Intermediate Nickel Layer.

Lightweight carbon nanotube fibers (CNTFs) with high electrical conductivity and high tensile strength are considered to be an ideal wiring medium for a wide range of applications. However, connecting CNTFs with metals by soldering is extremely difficult due to the nonreactive nature and poor wettability of CNTs. Here we report a strong connection between single-wall CNTFs (SWCNTFs) and a Cu matrix by introducing an intermediate Ni layer, which enables the formation of mechanically strong and electrically conductive joints between SWCNTFs and a eutectic Sn-37Pb alloy. The electrical resistance change rate (ΔR/R0) of Ni-SWCNTF/solder-Cu interconnects only decreases ∼29.8% after 450 thermal shock cycles between temperatures of -196 and 150 °C, which is 8.2 times lower than that without the Ni layer. First-principles calculations indicate that the introduction of the Ni layer significantly improves the heterogeneous interfacial bond strength of the Ni-SWCNTF/solder-Cu connections.

Single-Walled Carbon Nanotube/Copper Core-Shell Fibers with a High Specific Electrical Conductivity.

Carbon nanotube (CNT)/Cu core-shell fibers are a promising material for lightweight conductors due to their higher conductivity than pure CNT fibers and lower density than traditional Cu wires. However, the electrical properties of the hybrid fiber have been unsatisfactory, mainly because of the weak CNT-Cu interfacial interaction. Here we report the fabrication of a single-walled CNT (SWCNT)/Cu core-shell fiber that outperforms commercial Cu wires in terms of specific electrical conductivity and current carrying capacity. A dense and uniform Cu shell was coated on the surface of wet-spun SWCNT fibers using a combination of magnetron sputtering and electrochemical deposition. Our SWCNT/Cu core-shell fibers had an ultrahigh specific electrical conductivity of (1.01 ± 0.04) × 104 S m2 kg-1, 56% higher than Cu. Experimental and simulation results show that oxygen-containing functional groups on the surface of a wet-spun SWCNT fiber interact with the sputtered Cu atoms to produce strong bonding. Our hybrid fiber preserved its integrity and conductivity well after more than 5000 bending cycles. Furthermore, the current carrying capacity of the coaxial fiber reached 3.14 × 105 A cm-2, three times that of commercial Cu wires.

Efficient Fabrication of High-Quality Single-Walled Carbon Nanotubes and Their Macroscopic Conductive Fibers.

High-purity and well-graphitized single-walled carbon nanotubes (SWCNTs) with excellent physiochemical properties are ideal building blocks for the assembly of various CNT macrostructures for a wide range of applications. We report the preparation of high-quality SWCNTs on a large scale using a floating catalyst chemical vapor deposition (FCCVD) method. Under the optimum conditions, the conversion rate of the carbon source to SWCNTs reached 28.8%, and 20.4% of the metal nanoparticles were active for SWCNT growth, which are 15% and ∼400 times higher than those previously reported for FCCVD synthesis, respectively. As a result, the prepared SWCNTs have a very low residual catalyst content of ∼1.9 wt % and a high rapid oxidation temperature of 717 °C. Using these high-quality SWCNTs, we spun macroscopic SWCNT fibers by a wet-spinning process. The resulting fibers had a high electrical conductivity of 6.67 MS/m, which is 32% higher than the best value previously reported for SWCNT fibers.

Mild acid-based surfactant-free solutions of single-walled carbon nanotubes: Highly viscous, less toxic, and humidity-insensitive solutions

Owing to their exceptional physical properties, single-walled carbon nanotubes (SWNTs) are widely applicable if translated into macroscopically assembled SWNT materials. The assembly method involves SWNT solutions prepared using surfactants or superacids. As both variations of the method are difficult to industrialize, a novel SWNT solution is prepared herein using mild polyphosphoric acid (PPA) without surfactant. Although the dissolution of SWNTs in PPA is thermodynamically unfavorable because of lower acidity compared to superacids, high viscosity kinetically contributes to phase stabilization when SWNTs are de-bundled upon high shearing. Interestingly, the SWNT/PPA solution is humidity-insensitive, which is beneficial for handling. In the 0.01–2.0 wt% range, the critical concentration and saturation point, at which phase transitions of isotropic-liquid crystalline (LC) and LC-gel states occur, are observed at 0.1 and 1.0 wt%, respectively. According to the steady shear rheology, the optimal concentrations for fiber spinning are 0.3–0.7 wt%. Polarized Raman and WAXD analyses show that the wet-spun SWNT fibers from the 0.5 wt% solution exhibit the highest fiber orientation, correlating with the lowest extrusion shear stress of the solution. The KevlarTMp-aramid dissolved in PPA and blended with SWNTs shows a negligible effect on the solution rheology but higher fiber modulus at high fractions.

Effects of Different Factors on the Heat Conduction Properties of Carbon Films and Fibers

The increasing popularity of carbon nanotubes has created a demand for greater scientific understanding of the characteristics of thermal transport in nanostructured materials. However, the effects of impurities, misalignments, and structure factors on the thermal conductivity of carbon nanotube films and fibers are still poorly understood. Carbon nanotube films and fibers were produced, and the parallel thermal conductance technique was employed to determine the thermal conductivity. The effects of carbon nanotube structure, purity, and alignment on the thermal conductivity of carbon films and fibers were investigated to understand the characteristics of thermal transport in the nanostructured material. The importance of bulk density and cross-sectional area was determined experimentally. The results indicated that the prepared carbon nanotube films and fibers are very efficient at conducting heat. The structure, purity, and alignment of carbon nanotubes play a fundamentally important role in determining the heat conduction properties of carbon films and fibers. Single-walled carbon nanotube films and fibers generally have high thermal conductivity. The presence of non-carbonaceous impurities degrades the thermal performance due to the low degree of bundle contact. The thermal conductivity may present power law dependence with temperature. The specific thermal conductivity decreases with increasing bulk density. At room temperature, a maximum specific thermal conductivity is obtained but Umklapp scattering occurs. The specific thermal conductivity of carbon nanotube fibers is significantly higher than that of carbon nanotube films due to the increased degree of bundle alignment.

Karbon nanotüplerin ve fiberlerin ısı iletim özellikleri üzerine yapı, saflık ve hizalamanın etkileri

The increasing popularity of carbon nanotubes has created a demand for greater scientific understanding of the characteristics of thermal transport in nanostructured materials. However, the effects of impurities, misalignments, and structure factors on the thermal conductivity of carbon nanotube films and fibers are still poorly understood. Carbon nanotube films and fibers were produced, and the parallel thermal conductance technique was employed to determine the thermal conductivity. The effects of carbon nanotube structure, purity, and alignment on the thermal conductivity of carbon films and fibers were investigated to understand the characteristics of thermal transport in the nanostructured material. The importance of bulk density and cross-sectional area was determined experimentally. The results indicated that the prepared carbon nanotube films and fibers are very efficient at conducting heat. The structure, purity, and alignment of carbon nanotubes play a fundamentally important role in determining the heat conduction properties of carbon films and fibers. Single-walled carbon nanotube films and fibers generally have high thermal conductivity. The presence of non-carbonaceous impurities degrades the thermal performance due to the low degree of bundle contact. The thermal conductivity may present power law dependence with temperature. The specific thermal conductivity decreases with increasing bulk density. At room temperature, a maximum specific thermal conductivity is obtained but Umklapp scattering occurs. The specific thermal conductivity of carbon nanotube fibers is significantly higher than that of carbon nanotube films due to the increased degree of bundle alignment.

Nonlinear static analysis of CNT/nanoclay particles reinforced polymer matrix composite plate using secant function based shear deformation theory

ABSTRACT The mechanically induced nonlinear statical assessment of the bending response of single-walled carbon nanotubes (CNTs) fibers on nanoclay-particle-reinforced polymer hybrid laminated composite plate is explored under static loading conditions. A numerical approach is used to find the mechanical properties of CNT-reinforced hybrid laminated plates prepared by involving nanoclay particles in the existing CNT-reinforced epoxy composites. The transverse nonlinear central deflection of a hybrid nanocomposite subjected to mechanical loading based on the Halpin–Tsai approach is evaluated. For the fundamental formulation, a secant-function-based shear deformation theory (SFSDT) and von Kármán nonlinearity are implemented. The influence of CNT/nanoclay particles over the nonlinear bending responses of the hybrid laminated plate under various loading circumstances is studied in detail. A Newton–Raphson method based on nonlinear finite element technique is used for the hybrid nanocomposite plate. Furthermore, the impact of different design parameters, such as thicknesses of CNT fibers, different interphases along with aspect ratios, stacking sequences under different boundary conditions, and the types of loads on the nonlinear transverse central deflection of CNT/nanoclay-reinforced polymer hybrid composite plate, has been investigated. The effectiveness of the suggested model has been confirmed by comparing it to deflection reactions found in the literature.

Effects of Carbon Nanotube Structure, Purity, and Alignment on the Heat Conduction Properties of Carbon Films and Fibers

The increasing popularity of carbon nanotubes has created a demand for greater scientific understanding of the characteristics of thermal transport in nanostructured materials. However, the effects of impurities, misalignments, and structure factors on the thermal conductivity of carbon nanotube films and fibers are still poorly understood. Carbon nanotube films and fibers were produced, and the parallel thermal conductance technique was employed to determine the thermal conductivity. The effects of carbon nanotube structure, purity, and alignment on the thermal conductivity of carbon films and fibers were investigated to understand the characteristics of thermal transport in the nanostructured material. The importance of bulk density and cross-sectional area was determined experimentally. The results indicated that the prepared carbon nanotube films and fibers are very efficient at conducting heat. The structure, purity, and alignment of carbon nanotubes play a fundamentally important role in determining the heat conduction properties of carbon films and fibers. Single-walled carbon nanotube films and fibers generally have high thermal conductivity. The presence of non-carbonaceous impurities degrades the thermal performance due to the low degree of bundle contact. The thermal conductivity may present power law dependence with temperature. The specific thermal conductivity decreases with increasing bulk density. At room temperature, a maximum specific thermal conductivity is obtained but Umklapp scattering occurs. The specific thermal conductivity of carbon nanotube fibers is significantly higher than that of carbon nanotube films due to the increased degree of bundle alignment.

Integrated, Highly Flexible, and Tailorable Thermoelectric Type Temperature Detectors Based on a Continuous Carbon Nanotube Fiber.

As possible alternatives to traditional thermoelectric (TE) materials, carbon nanomaterials and their hybrid materials have great potential in the future application of flexible and lightweight temperature detection. In this work, an integrated, highly flexible, and tailorable TE temperature detector with high performance has been fabricated based on a continuous single-walled carbon nanotube (SWCNT) fiber. The detector consists of more than one pairs of thermocouples composed of p-type SWCNT fiber and n-type SWCNT hybrid fiber in situ doped by polyethylenimine. Due to the node contact mechanism of the detection, the sensitivity of the detector can be improved with the increase of the number of p-n thermocouples, independent of the length of the thermocouple. The temperature detection process of the detector has been studied in detail. In particular, the integrated and flexible detector can be divided into several sub-detectors easily by cutting, illustrating the prospect of large-scale preparation of this kind of novel temperature detectors. Its high flexibility ensures the detector to maintain excellent detection performance after 15000 bending circles. Furthermore, the as-designed TE type temperature detector demonstrates a great application promise for real-time temperature detection and temperature change sensing even in complex surface and harsh environment.

Highly flexible and excellent performance continuous carbon nanotube fibrous thermoelectric modules for diversified applications* *Project supported by the National Key Research and Development Program of China (Grant No. 2018YFA0208402), the National Natural Science Foundation of China (Grant Nos. 11634014, 51172271, and 51372269), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA09040202).

A highly flexible and continuous fibrous thermoelectric (TE) module with high-performance has been fabricated based on an ultra-long single-walled carbon nanotube fiber, which effectively avoids the drawbacks of traditional inorganic TE based modules. The maximum output power density of a 1-cm long fibrous TE module with 8 p–n pairs can reach to 3436 μW ⋅ cm−2, the power per unit weight to 2034 μW ⋅ g−1, at a steady-state temperature difference of 50 K. The continuous fibrous TE module is used to detect temperature change of a single point, which exhibits a good responsiveness and excellent stability. Because of its adjustability in length, the flexible fibrous TE module can satisfy the transformation of the temperature difference between two distant heat sources into electrical energy. Based on the signal of the as-fabricated TE module, a multi-region recognizer has been designed and demonstrated. The highly flexible and continuous fibrous TE module with excellent performance shows a great potential in diversified applications of TE generation, temperature detection, and position identification.

Electromechanical properties of fibers produced from randomly oriented SWCNT films by wet pulling technique

We examined a fiber formation from pristine and modified single-walled carbon nanotube (SWCNT) films using a recently developed wet pulling technique. Crucial phenomena in the wet pulling process are a folding of a solvent soaked SWCNT film due to the liquid surface tension and fiber densification during the solvent evaporation. It is shown that electrical characteristics of the as-produced fibers are determined by the type of the liquid employed in their formation, which defines the SWCNT packing degree. The obtained specific strength (0.6–0.8 N/tex), toughness (up to 127 J/g) and specific conductivity (0.5–1.2 kS·m2/kg) are in many cases comparable with published data for fibers produced by more resource-consuming methods. These, in combination with the simplicity of our method and high piezoresistive gauge factor of 14 (for untwisted fibers at a 1% elongation), make SWCNT fibers promising components in future applications of stretchable electronics and robotics.

Superwetting TiO2-decorated single-walled carbon nanotube composite membrane for highly efficient oil-in-water emulsion separation

With the advantages of one-dimensional hollow structure, high porosity and prominent mechanical strength, single-walled carbon nanotubes (SWCNTs) have been extensively utilized to improve conventional filtration membranes for oil/water separation. Their intrinsic hydrophobicity, however, adversely affects the anti-fouling performance of the SWCNT membrane. Herein, a super-hydrophilic and underwater super-oleophobic hierarchical modified membrane with enhanced permeability and anti-fouling property was fabricated using the vacuum-assisted filtration technique by synergistically assembling SWCNTs and titanium dioxide (TiO2) nanoparticles on a cellulose acetate membrane. Highly dispersed SWCNTs were obtained by carboxylating treatment of agglomerate SWCNTs. The controlled stacking of SWCNTs fibers and a controllable amount of TiO2 rendered a modified membrane with high porosity and hierarchical structure, leading to an ultrahigh water flux up to 4,777.07 L·m−2·h−1, and excellent separation performance with efficiency greater than 99.47%. Most importantly, the membrane exhibited excellent anti-fouling ability during ten cycles with the aid of the super-wetting property of TiO2 nanoparticles. The results indicated that coating TiO2 nanoparticles on SWCNTs modified the surface topography of the obtained SWCNT/TiO2 membrane, which improved hydrophilicity, permeability and anti-fouling property, manifesting attractive potential applications in oil/water separation.

Band gap tuning of TiO2 NP–SWCNT nanocomposite materials using surfactant synthesis techniques

Optimizing photocatalysts to function within the visible region offers enhanced economics considering that 40% of the sun’s energy is in the visible region, compared to just 4% in the UV region. To better utilize available solar flux, nanocomposite materials using TiO2 nanoparticles and single walled carbon nanotubes (SWCNTs) have been studied. Separating the SWCNT bundles using surfactants combined with a photo-assisted sol–gel preparation produced low band gap (<0.5 eV) materials. Infrared analysis showed the formation of Ti-O-C bonds that are attributed to photoactivity in the visible spectrum (i.e. red shift). The π–π stacking interactions between the benzene ring of the sodium dodecyl benzenesulfonate surfactant and the SWCNTs provided greater separation of the SWCNT fibers, increasing the coverage of TiO2 to SWCNT surfaces.

Formation of Poly(vinyl alcohol)/SWNTs Fibers with Hierarchical Structure under High-Speed Shear Flow

This study introduces a facile method to prepare syndiotactic poly(vinyl alcohol) (s-PVA) fibers containing singlewalled carbon nanotubes (SWNTs) from the corresponding composite dispersions with tea polyphenols (TP) as dispersant under high-speed shear flow. The formation of the composite fibrous precipitates at high shear rate is largely facilitated by the SWNTs in the dispersions and slight flow resistance. Interestingly, the obtained s-PVA/SWNTs composite precipitates possess a three-level hierarchical structure, that is, a single fiber is assembled by fibrils which are composed of microfibrils of s-PVA-coated SWNTs. And the s-PVA fibrous precipitates containing high amounts of SWNTs could be obtained by shearing the dispersion with relatively low SWNTs loadings, as a result, the composite fiber containing 20.7 wt% SWNTs was prepared from the dispersion with 10.0 wt% SWNTs. In addition, with the increase of SWNTs loadings, the amount of the precipitates increases, but crystallinity of the precipitates decreases instead.

Semiconducting carbon nanotube fibers for electrochemical biosensor platforms

We report the fabrication of semiconducting single-walled carbon nanotube (sc-SWNT) fibers via wet-spinning for electrochemical biosensor platforms. SWNTs were purified using thermal and acid treatments and separated into metallic SWNTs and sc-SWNTs. The sc-SWNTs were then wet-spun into flexible fibers. Then, an enzyme capable of reacting with glucose was immobilized on the sc-SWNT fibers to investigate the utility of sc-SWNT fibers as an electrochemical biosensor platform. The enzyme-activated sc-SWNT fibers, which exhibited the field effects, were then configured into fiber-type glucose sensors capable of detecting the glucose in a solution, demonstrating the potential of sc-SWNT fibers as an electrochemical biosensor platform.

Rational design of highly efficient flexible and transparent p-type composite electrode based on single-walled carbon nanotubes

Transparent electrodes are of great importance in electronics and energy technologies. At present, transparent conductive oxides are mainly n-type conductors dominating the market and have restricted the technological advancements. Single-walled carbon nanotubes (SWCNTs) have recently emerged as promising p-type transparent conductor owing to their superior hole mobility, conductivity, transparency, flexibility and possibility to tune the work function. Here, we develop a novel rational design of p-type flexible transparent conductive film (TCF) based on SWCNTs combined with poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), molybdenum oxide and SWCNT fibers. In a configuration of SWCNTs-MoO3-PEDOT:PSS/SWCNT fibers, we achieved a record equivalent sheet resistance of 17 Ω/sq with a transmittance of 90% at 550 nm and a high degree of flexibility. We demonstrate that our solar cells developed on the basis of the proposed electrode and hydrogenated amorphous silicon (a-Si:H) yield an outstanding short-circuit current density of Jsc = 15.03 mA/cm2 and a record power conversion efficiency of PCE = 8.8% for SWCNTs/a-Si:H hybrid solar cells. We anticipate that this novel rationally designed p-type TCF opens a new avenue in widespread energy technologies, where high hole conductivity and transparency of the material are prerequisites for their successful implementation.

Molecular characterization of macroscopic aerogels of single-walled carbon nanotubes

Single-walled carbon nanotubes (SWCNT) can be assembled into various macroscopic architectures, most notably continuous fibers and films, produced currently on a kilometer-per-day scale by floating catalyst chemical vapor deposition and spinning from an aerogel of CNTs. An attractive challenge is to produce continuous fibers with controlled molecular structure with respect to the diameter, chiral angle and ultimately (n,m) indices of the constituent SWCNT “molecules”. This work presents an extensive Raman spectroscopy and high-resolution transmission electron microscopy study of SWCNT aerogels produced by the direct spinning method. By retaining the open structure of the SWCNT aerogel, we reveal the presence of both semiconducting and metallic SWCNTs and determine a full distribution of families of SWCNT grouped by optical transitions. The resulting distribution matches the chiral angle distribution obtained by electron microscopy and electron diffraction. The effect of SWCNT bundling on the Raman spectra, such as the G− line shape due to plasmons activated in the far-infrared and semiconductor quenching, are also discussed. By avoiding full aggregation of the aerogel and applying the methodology introduced, rapid screening of molecular features can be achieved in large samples, making this protocol a useful analysis tool for engineered SWCNT fibers and related systems.