CNTs Content Research Articles

Carbon nanotube heat absorber for efficient direct-heating of liquid tin in a solar receiver

A new approach that use vertically-aligned carbon nanotubes (VACNT) as heat absorbers is proposed for efficient direct solar heating of liquid tin in a solar receiver integrated with beam-down optics. Plate-type CNT heat absorbers were prepared by adjusting the concentration of CNTs in the processing solvent m-cresol. The prepared CNT absorber exhibited an increase in bulk density and the formation of a densely packed nanotubes skeleton with a higher CNT concentration in m-cresol. Thermal conductivity, a key design factor for solar absorbers, showed a stronger correlation with skeletal density than with bulk density. Heat absorption characteristics of the solar liquid tin receiver (50 mm-i.d., 60 mm-high) with the CNT absorbers integrated with a Fresnel lens (0.98 m i.d.) were determined. The tin temperature in the receiver with the CNT absorber reached a maximum of 728 °C. Bare tin exhibited system efficiency of 27.7 % and receiver efficiency of 38.3 %, but tin heating through the CNT plates exhibited system efficiency of up to 48.4 % and receiver efficiency of 64.3 %, showing a system heat absorption rate 1.75 times higher. The thermal absorption efficiency was proportional to the skeletal density of the plates, and the thermal absorption of the system was dominated by the efficient transfer of absorbed heat in the energy absorption region. The energy flow and heat loss in the receiver system were analyzed. Although the bare tin receiver exhibited a high heat loss of 27.1 % owing to the low emissivity or high reflectivity of the tin surface, the heat loss in the CNT absorber plates with high absorptivity was only 0.9 %. The flat plate-shaped transmission window in the receiver caused significant reflective heat loss and convective heat loss owing to head-on wind. Based on the energy flow analysis, improvement approaches for enhancing the thermal efficiency of the proposed receiver system are suggested.

Reinforcing biomimetic cementitious composites by aligned hierarchical carbon fibers

Cementitious composites reinforced by carbon-based fibers of varied length scales still face limitations of a single dimension, anisotropic alignment, smooth surface, or poor dispersion. In this study, we developed a bioinspired, hierarchical reinforcing structure that enables multiscale coupling of mechanical properties and directional fiber alignment, significantly improving the load-bearing capacity of cementitious composite. The aligned hierarchical reinforcing structure was synthesized by grafting CNTs onto microscale CFs-COOH via an esterification reaction and a nozzle-injected technique. Parameters for synthesizing the CNTs grafted aligned CF (ACF-CNTs) were optimized considering oxidation solutions, grafting techniques, CNTs geometry, and CNTs concentrations. The chemical bond between CF and CNTs was examined by Laser Raman Spectrometer (LRS), Fourier Transform Infrared Spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS), respectively. Results indicate that CNTs are uniformly and densely grafted onto CF via ester linkage, forming a hierarchical reinforcing structure. Mechanical measurements show that 1 wt% ACF-CNTs results in a maximum flexural strength of 34.76 MPa and a maximum improvement of 297.12 % (compared to plain cement paste) in the biomimetic cementitious composites. Analysis based on fiber alignment, interface transition zone, and failure mode of CF-CNTs/CNTs suggests that multiscale coupling of mechanical properties and directional fiber alignment are the main reinforcing mechanisms.

Effect of CNTs concentration on the microstructure and properties of B, Ni, CNTs co-doped diamond like carbon films

B, Ni, and CNTs co-doped diamond-like carbon (B, Ni, CNTs co-doped DLC) films were synthesized on the surface of AZ91D magnesium alloy by electrodeposition with low cost. The effect of CNTs concentration on the microstructure, microhardness, tribological properties and corrosion behavior of B, Ni, CNTs co-doped DLC films were evaluated. Results revealed that the B, Ni, CNTs co-doped DLC films were hydrogenated amorphous carbon films. Raman spectra showed that the D and G peaks of DLC films appear near 1330 cm−1 near 1580 cm−1, respectively. When the concentration of CNTs was 0.25 g/L, the CNTs were evenly distributed, making the structure of co-doped DLC films uniform, dense and flat. At this time, since the combined synergistic effect of reticulation of CNTs and the network-like structure of DLC films, the microhardness of the co-doped DLC films reached the maximum of 248.3 HV. The tubular structure of CNT supports and lubricates the substrate, which weakens the frictional resistance between the friction partners and reduces the friction coefficient to the lowest value of 0.128. The wear loss was the minimum with 0.1 × 10−5 kg/m, which is the result of CNTs exerting their self-lubricating properties to improve the wear resistance of the DLC film so that less wear occurs during the repeated friction process. Meanwhile, the positive corrosion potentials of B, Ni, CNTs co-doped DLC films indicate that the three elements co-doped DLC films can improve the corrosion resistance of magnesium alloy substrates.

Versatile Lamellar Wrap-Structured PVDF/PZT/CNTs Piezoelectric Sensor for Road Traffic Information Sensing, Monitoring, and Energy Harvesting

Active monitoring and accurate sensing of road traffic information provide crucial data for road managers and traffic law enforcement. However, current sensors and monitoring systems struggle to capture comprehensive vehicle information simultaneously. In the study, a novel piezoelectric sensor using PVDF/PZT/CNTs composites was developed for actively monitoring road traffic information and explored for energy harvesting suitability. Piezoelectric composites with a lamellar wrapped structure and excellent localized conductive networks were prepared through solution blending, non-solvent-induced phase separation, and layered hot pressing. The results revealed that this structural design improves the proportions, crystallinity, and content of the β-phase crystals in the composites, while significantly enhancing their piezoelectric properties, dielectric properties, and electronegativity. When the content of CNTs was 3.0 wt%, the proportion and content of β-phase crystals in the composites reached the highest values (91.36 % and 62.34 %), respectively. Additionally, the open-circuit voltage (Voc) and the short-circuit current (Isc) were 3.36 and 6.16 times higher, respectively, than those of the undoped CNTs composites. The developed piezoelectric sensor shows a wide pressure monitoring range (0.1 MPa–2.1 MPa), excellent sensitivity (6.94 MPa−1 at (<0.6 MPa) and 12.35 MPa−1 at (0.6–2.1 MPa)). As a vehicle non-stop weighing sensor, it presents extremely fast response (15 ms) and recovery (16 ms) speeds with long-term stability of 500,000 cycles. The most important feature of the developed piezoelectric sensor is its dual function as both a sensor and an energy harvester. Furthermore, the developed piezoelectric sensor can actively monitor vehicle axle weight, speed, and wheelbase while capturing energy from vehicle movement. This work opens up innovative solutions for road traffic monitoring and vehicle movement energy harvesting, with promising applications in intelligent transportation.

Enhancement of thermal–mechanical performances via a selective CNTs configuration in laminated CNTs/AZ31B composite

Magnesium alloy is an excellent lightweight material. While the alloying process improves mechanical properties, it often reduces material thermal conductivity. An effective way to balance these two properties is to add CNTs. In this paper, a novel laminated CNTs/AZ31B composite was fabricated by introducing CNTs with selective configuration. First, the specific configuration of CNTs was built onto AZ31B sheets with a reticle mask using the electrophoretic deposition process. Then, the CNTs/AZ31B composite was obtained by the hot-pressing process. The effect of deposition factors on composite forming quality was studied to seek a satisfactory interlayer binding. Finally, the mechanical and thermal properties of CNTs/AZ31B composites with different CNTs content and deposition orientations were tested. The results show that the mechanical and thermal properties of CNTs/AZ31B composites were noticeably anisotropic. By adding 0.5 wt% CNTs, the tensile strength and Young’s modulus of the CNTs/AZ31B composite were effectively enhanced by 30.3 % and 10.5 %, respectively. Meanwhile, the thermal conductivity of the composites increased to 84.2 W/ (m·K) when adding 0.25 wt% CNTs, with heat conduction and dissipation performance enhanced. The studies of tensile fracture and CNT-Mg interfaces of CNTs/AZ31B composite show that CNTs can act as a shortcut of heat flow and load transfer.

Electrodeposition of Pb-0.6 %Sb/α-PbO2/β-PbO2-CNTs electrodes: Investigation focusing on co-deposition modification mechanism and energy consumption

The present study investigated the electrodeposition of Pb-0.6 %Sb/α-PbO2/β-PbO2-Carbon Nanotube (CNTs) energy-saving electrodes with different proportions of co-deposited CNTs and compared the application with industrial Pb-0.8 wt%Ag anodes in a long-period zinc electrodeposition process. When the concentration of CNTs was 3 g·L−1, the charge transfer resistance Rct of the oxygen-evolution reaction reached the minimum value (6.140 Ω·cm2), while the corrosion resistance achieved the maximum value (Ecorr 1.3255 V, Icorr 2.06 × 10−4 A). CNTs co-deposition considerably refined the grain size and enhanced the electrocatalytic activity. Additionally, the co-deposition modification mechanism of CNTs and β-PbO2 was elucidated. During the long period zinc electro-deposition process, Pb-0.6 %Sb/α-PbO2/β-PbO2-CNTs energy-saving electrodes reduced the cell voltage and power consumption by 299 mV and 373.97 kWt/(t·Zn) compared with industrial Pb-0.8 wt%Ag anodes, respectively. The overall energy conservation effect was remarkable.

Photocatalytic Activity and Antibacterial Properties of ZnO/CNTs Composites

Photocatalytic technology is one of the promising technologies for wastewater treatment. Herein, zinc oxide/multi-walled carbon nanotubes (ZnO/CNTs) photocatalyst was successfully prepared by hydrothermal method with combining in-situ synthesis technology. The micro-morphology, crystalline structure, surface chemical elements, and optical properties were characterized by SEM, TEM, XRD, FTIR, UV-Vis, and DRS technologies. The ZnO/CNTs photo-catalyst exhibited enhancement photo activity for degradation of organic pollutants under simulated light irradiation. Specifically, the photo-catalytic activity of the ZnO/CNTs catalysts improved with the rise of CNTs content in the composites. Investigation on the photo-degradation mechanism verified that the presence of CNTs in the catalyst not only optimized the band structure of ZnO semiconductor but also contributed to the transfer of photo-generated electrons and reducing the recombination of electron-hole pairs due to its excellent conductivity. Moreover, the active radical groups such as superoxide radical (O-2), hole (h+), and hydroxyl radical (·OH) played the dominated role for the pollutants degradation under the simulated sunlight irradiation. In addition, ZCT20 catalysts and light irradiation had synergistic effects on antibacterial activity, whose antibacterial rates against E. coli and S. aureus were up to 99.96% and 99.94%, respectively. Investigation on antibacterial mechanisms revealed that the existence of ROS and the continuous release of Zn2+ played an important role for improving the antibacterial activity of the ZCT20 catalyst under the simulated sunlight irradiation.

Wear resistance of extruder parts in the production of polymer nanomodified products

Extrusion equipment is widely used in the production of polymer materials. One of the urgent questions that arises when studying the processes of obtaining polymer products by the extrusion method is the question of studying abrasive wear, which may depend on the efficiency of the equipment, the duration and reliability of its work. In the context of abrasive wear, the process that needs attention is the extrusion of polymer materials with carbon nanotubes. The purpose of this work is to develop a numerical method for determining the evolution of abrasive wear of the equipment of the extruder working area in the process of processing nanomodified polymer granules and determining the life cycle of this equipment with in order to increase the parameters of their durability. The specific objectives of the study include: 1) Determination of the influence of the content of CNTs in PVC on the rate of wear of the steel surface of the extruder; 2) Analysis of the dependence between friction and the content of CNTs in the polymer composite; 3) Establishing optimal extrusion conditions to minimize abrasive wear of the steel surface; 4) Comparison of simulation results with experimental data to check the reliability of the model. The work is aimed at understanding the processes that occur during the extrusion of nanocomposites and their impact on the wear resistance of equipment materials, which can contribute to the improvement of technological processes and ensure longer and more efficient operation of extruders in production conditions. It has been established that the processes of extrusion processing of polymer nanoreinforced composites can be effectively studied by developing and implementing numerical models that take into account the interaction of all physical and mechanical parameters of a representative volume of the contact zone of the equipment with the polymer and the nanotube with the adhesive layer. In this work, a model for determining the physical and mechanical properties of the interface layer between the CNT and the polymer array is constructed and implemented. The technique for determining the properties of the nanotube-polymer interface is integrated into the APROKS system for analyzing the stress-strain state of nanomodified polymer materials. Based on a multilayer isoparametric FE, a series of numerical experiments were carried out to simulate the process of abrasive wear of the material of equipment elements in the extruder working area. The possibility of a detailed study of the processes of nonlinear contact interaction of nanotubes with an interface layer with equipment elements of the extruder working area based on multilayer FE has been confirmed. Diagrams were obtained that determine the service life of equipment in the working area of the extruder depending on the volume concentration of carbon nanotubes in the polymer at different levels of operating pressure in the “nanotube – polymer – equipment” contact system. It is advisable to use the proposed methodology in the development of information support systems for the life cycle of operation of equipment in the working area of extruders intended for the production of nanomodified polymer products.

Synergistic hybrid effect of nano fillers on the structure and properties of asphalt composites

ABSTRACT The CNTs/nano ZnO/SBS/asphalt composites with different CNTs content were prepared by solution casting method. The morphology of the composite shows that the dispersion of SBS is improved by the synergistic hybrid effect of CNTs and nano ZnO. Good dispersion is beneficial for enhancing the adsorption of lightweight components, thereby effectively improving the temperature range of asphalt use. At the same time, the increase in the proportion of asphaltene leads to an increase in the number of honeycomb structures, the surface roughness of composite materials, as well as the water contact angle.

Lightweight broadband electromagnetic wave absorption achieved by a like-clustered CNTs spheres modified SiC nanowires

Developing lightweight, broadband, and highly absorptive electromagnetic (EM) wave absorption materials by effectively utilizing the agglomeration effect of one-dimensional nanowires is challenging. In this work, a SiCnws/CNTs aerogel with a like-clustered CNTs sphere-modified SiCnws structure was prepared via simple freeze-drying and heat treatment techniques, where the CNTs content was controlled to adjust the quantity and volume of the CNTs spheres. This allows for effective regulation of the impedance matching characteristics and dielectric loss capability. Specifically, the SiCnws/CNTs aerogel exhibited remarkable dissipation of EM waves through the enhancement of the interface and dipole polarization, achieved by significantly increasing the presence of multiple interfaces and defects. Moreover, the aerogel structure induces conduction loss and amplifies multiple reflections and scattering, facilitating efficient dissipation of EM wave energy across multiple levels. The minimum reflection loss (RLmin) of the SiCnws/CNTs aerogel (SN-3 sample) achieves −43.4 dB at 11.2 GHz with a matching thickness of 2.6 mm. Its effective absorption bandwidth (EAB) spans from the C band to the Ku band (7.4–18 GHz) at thicknesses ranging from 2.1 to 4.4 mm. Additionally, when the matching thickness is 3.4 mm, the broadened EAB extends up to 9.8 GHz (covering the whole X and Ku bands). Furthermore, CST simulations clearly demonstrate a remarkable suppression of the incident EM wave by the samples under real-world conditions, with a substantial reduction of 42.5 dBm2 in the RCS. Considering this, SiCnws/CNTs aerogel materials pave the way for new opportunities in lightweight, broadband, and high-absorption materials.

Effect of thiol-modified carbon nanotubes on curing, mechanical, and thermophysical properties of poly(ethylene trisulfide)

Herein, we performed grafting of thiol groups to the surface of multi-walled carbon nanotubes. Then, using them (CNTS), zinc oxide (ZnO), ethylene dichloride, and sodium trisulfide (Na2S3), poly(ethylene trisulfide) (PETS) nanocomposites were synthesized via in situ polymerization. After that, the samples were cured at 170°C using a rheometer. The structural characteristics of CNTS were identified by Fourier transform infrared (FTIR), Raman spectroscopies, and X-ray diffraction (XRD). The PETS characteristics were investigated by FT-IR, Raman, X-ray diffraction (XRD), and proton nuclear magnetic resonance (1H NMR). Also, the samples were studied using scanning electron microscopy (SEM), Shore A, tensile tests, and differential scanning calorimetry (DSC). The results showed that CNTS has a significant effect on the curing time of the nanocomposites, so that the curing time decreases with increasing CNTS content. Moreover, the nanocomposites had improved mechanical properties, indicating that they are more resistant to deformation and fracture. In addition, after the curing process, the melting temperature (Tm ) was not observed, and by increasing CNTS in composites, the glass transition temperature (Tg ) occurs at higher temperatures. Furthermore, the hardness of the samples showed a slight increase with higher CNTS content.

Constructing salt-resistant 3D foams with hierarchical interconnected channels by vacuum casting method for efficient solar evaporation of hypersaline water

Solar interfacial water evaporation is an environmentally friendly and potential approach to producing fresh water. Herein, a PAN/CNTs-foam (PCF) evaporator with high porosity, hierarchical pore structure, and excellent solar absorption was successfully prepared by the vacuum casting method. The PCF prepared with a CNTs content of 17 % and NaCl particle size of 150–300 μm possessed an evaporation rate of 2.04 kg m−2 h−1 for pure water under 1 sun illumination. The PCF-2 showed a maximum evaporation rate of 5.60 kg m−2 h−1 for real seawater in outdoor experiments, and the quality of the produced clean water was also demonstrated. The purification ability of PCF for organic dyes further confirmed the potential usage in wastewater treatment. Particularly, the PCF-2 exhibited efficient and stable desalination performance for hypersaline water even in 25 wt% simulated brine due to the hierarchical interconnected channels. Our work offers a robust method for the construction of a 3D foam evaporator with hierarchical interconnected channels for efficient and sustainable hypersaline water desalination.

High-performance electromagnetic wave absorption of NiS/Ni0.96S@multi-walled carbon nanotube composites

In this work, composites of heterogeneous nickel sulfide with multi-walled carbon nanotubes (MWCNTs) were prepared by a simple hydrothermal method. The dielectric loss capacity of composite materials is enhanced with the introduction of CNTs. Meanwhile, with the increase of CNTs content, the particle size of nickel sulfide decreases and the specific surface area increases, which is beneficial to enhance the microwave absorption capacity of the sample. The composite with the best microwave absorption performance was obtained by changing the NiS/Ni0.96S@MWCNTs mass ratio. By adjusting the NiS/Ni0.96S@MWCNTs mass ratio to 6:1, the effective absorption bandwidth is 3.76 GHz, corresponding to a thickness of 1.3 mm. Besides, the minimum reflection loss (RL) value was as high as –35.5 dB at 10.0 GHz with the thickness of 2.0 mm. The above results show that the prepared NiS/Ni0.96S@MWCNTs composite has the advantages of thin thickness, light weight, strong absorption and simple preparation, and is a microwave absorbing material with promising applications.

1D CNTs assembled MOF-derived hollow CoSe2@N-doped carbon constructed high-efficiency electromagnetic wave absorbers

Optimizing impedance matching is crucial to achieve high-efficiency electromagnetic wave (EMW) absorption performance. In this work, Hollow CoSe2@N-doped Carbon/Carbon Nanotube-x (HCSC/CNTs-x) with unique three-dimensional conduction network was synthesized by using protection etching and high-temperature selenization strategies. The conductivity of HCSC/CNTs-x was regulated by varying the content of CNTs, and the extended three-dimensional electron transport pathway resulted in enhanced conduction and multiple reflection loss, while also optimizing impedance matching. Hollow CoSe2@N-doped carbon (HCSC) further facilitates the optimization of impedance matching. The abundant heterogeneous interfaces and defects induce strong interface polarization and dipole polarization, and the multiple loss mechanisms work in concert to confer excellent EMW absorption performance to HCSC/CNTs-x. The RLmin of HCSC/CNTs-30 reaches −41.68 dB, and the EABmax is 4.92 GHz at only 2.0 mm. The design strategy of three-dimensional conduction network of HCSC/CNTs-x provides an effective way to achieve the impedance matching optimization of CoSe2-based EMW absorption materials.

Effect of CNT content on the microstructure and friction characteristics of DED-fabricated CNTs-Ni60/WC coatings

The microstructure and tribological behavior of CNTs-reinforced Ni60/WC composites fabricated by directed energy deposition (DED) are studied. The effect of CNTs content is investigated and compared to that of a CNTs-free composite sample. The improvement of hardness, thermal stability, and wear resistance caused by microstructural refinement is observed in the CNTs reinforced composites. Different additions of CNTs may be responsible for the aforementioned performances. The microstructure and micro-protrusions growth characteristics are investigated using SEM and AFM, linked to the CNTs content, which refines the microstructure. The hardness, TG/DSC, and friction coefficient curves establish 1.5 wt% CNTs as the optimal addition amount. Additionally, the tribological characteristics are discussed based on the wear behavior and wear scar EDS analysis. The main friction mechanisms of the composites are abrasive wear and adhesive wear. The wear loss reduction peaked at 67.9 % in the 1.5 wt% CNTs-Ni60/WC composites. The mechanical properties of the coating are improved by CNTs. This clearly demonstrates the guiding significance of CNTs-reinforced composites for tribological development.

Synergistic effects of multitype carbon doping and oxygen vacancies in TiO2/CNTs composite fabricated via nonthermal plasma for formaldehyde removal

Formaldehyde as one of the typical indoor pollutants has long been concerned as it can pose a threat to human health. TiO2/CNTs composite with oxygen vacancies and multitype carbon doping (C–TiO2/CNTs) was fabricated using nonthermal plasma for the photocatalytic degradation of formaldehyde. The maximum degradation rate of formaldehyde was 93% and 83% via the new catalyst (with 5% CNTs content) under solar and visible light, respectively. The characterization of the catalyst confirmed the in-situ multitype carbon doping and oxygen vacancies: interstitial carbon doping and oxygen vacancies could dramatically reduce the bandgap and contribute to the improved absorption capability of formaldehyde and electrons. Interfacial carbon doping in the form of C–O–Ti bonds provided a migration channel, whereby photogenerated electrons could efficiently transfer from CNTs to TiO2 and then quench the holes left in the VB of TiO2. Therefore, the multitype carbon doping and oxygen vacancies can expand the light response as well as promote the separation of photo-generated electron/hole pairs. EPR results and experiment section indicated that O2·− plays the most significant role in formaldehyde removal due to the reverse transfer of the electrons. This work advances the understanding of photo-degradation of TiO2/CNTs composite and provides a new route for the abatement of formaldehyde.

High-efficient adsorption for versatile adsorbates by elastic reduced graphene oxide/Fe3O4 magnetic aerogels mediated by carbon nanotubes

Fabrication of highly elastic three-dimensional aerogel adsorbents with outstanding adsorption capacities is a long pursuit for the treatment of industrial contaminated water. In this work, a magnetic reduced graphene oxide (rGO)/Fe3O4/carbon nanotubes (CNTs) aerogel material was constructed by the electrostatic attraction between the negatively charged GO and positively charged CNTs following a one-pot water bath treatment. The as-synthesized aerogel demonstrated high compressive stress (28.4 kPa) and lower density (24.11 mg/cm3) with exceptional adsorption capacities for versatile adsorbates which are attributed to CNTs and magnetic Fe3O4 nanoparticles. The effect of pH, initial concentration of adsorbates (dyes, Cd (ІІ) ions, organic solvents, and pump oil), content of CNTs and cyclic times on the adsorption capacities of the aerogel were investigated in detail. Furthermore, from simulation, the adsorption kinetics, and thermodynamics of the aerogel for adsorbates were more satisfied by endothermic quasi-second-order kinetic model with characteristic physical adsorption. Thus, the optimized rGO/Fe3O4/CNTs-10 aerogel adsorbent can be used as a powerful and versatile tool to deal with contaminated industrial or domestic wastewater.

VSe2/CNTs nanocomposites toward superior electromagnetic wave absorption performance

Electromagnetic radiation pollution has become a serious threat, which will harm human health and interfere with electronic devices. However, it is still a challenge to develop high-efficiency electromagnetic wave absorbers with wide frequency band and strong absorption, especially for realizing the features of multi-bands absorption. Herein, VSe2/CNTs nanocomposites were successfully synthesized with crosslinked CNTs distributed on VSe2 nanoclusters composed of nanosheets. Importantly, the electromagnetic properties and absorption performance of the VSe2/CNTs nanocomposites can be effectively tailored by changing the hybrid ratio of CNTs and VSe2 nanosheets (VSe2-NSs). The increase of CNTs content promotes the formation of a conductive network and leads to the increase of permittivity. The VSe2/CNTs nanocomposite with CNTs of 40 mg exhibits the best electromagnetic wave absorption performance, the minimum reflection loss (RL) reaches −57.53 dB at 5.52 GHz and is about 6 times more than VSe2-NSs. Meanwhile, the VSe2/CNTs nanocomposite with CNTs of 30 mg shows dual-bands absorption performance with a minimum RL value of −50.06 dB at 3.84 GHz and the total effective absorption bandwidth of 3.32 GHz. This result proves that VSe2/CNTs nanocomposites can be promising candidates as high-efficiency electromagnetic wave absorption material and provides a feasible idea for designing a high-performance electromagnetic wave absorber.

Effects of Orientation and Dispersion on Electrical Conductivity and Mechanical Properties of Carbon Nanotube/Polypropylene Composite.

The orientation and dispersion of nanoparticles can greatly influence the conductivity and mechanical properties of nanocomposites. In this study, the Polypropylene/ Carbon Nanotubes (PP/CNTs) nanocomposites were produced using three different molding methods, i.e., compression molding (CM), conventional injection molding (IM), and interval injection molding (IntM). Various CNTs content and shear conditions give CNTs different dispersion and orientation states. Then, three electrical percolation thresholds (4 wt.% CM, 6 wt.% IM, and 9 wt.% IntM) were obtained by various CNTs dispersion and orientations. Agglomerate dispersion (Adis), agglomerate orientation (Aori), and molecular orientation (Mori) are used to quantify the CNTs dispersion and orientation degree. IntM uses high shear to break the agglomerates and promote the Aori, Mori, and Adis. Large Aori and Mori can create a path along the flow direction, which lead to an electrical anisotropy of nearly six orders of magnitude in the flow and transverse direction. On the other hand, when CM and IM samples already build the conductive network, IntM can triple the Adis and destroy the network. Moreover, mechanical properties are also been discussed, such as the increase in tensile strength with Aori and Mori but showing independence with Adis. This paper proves that the high dispersion of CNTs agglomerate goes against forming a conductivity network. At the same time, the increased orientation of CNTs causes the electric current to flow only in the orientation direction. It helps to prepare PP/CNTs nanocomposites on demand by understanding the influence of CNTs dispersion and orientation on mechanical and electrical properties.

Carbon nanotubes for improving rheological and chemical properties of styrene–butadiene–styrene modified asphalt binder

ABSTRACT This paper studied the effects of CNTs on high-temperature rheological and chemical properties of SBS modified asphalt. Molecular dynamics simulation, DSR, BBR, and FTIR spectrometer were performed to evaluate the molecular motion state, rheological and chemical properties of CNTs and SBS composite modified asphalt binders at different aging states. The MD results indicated that CNTs could absorb components in SBS-modified asphalt and restrict the movement and diffusion of SBS and asphalt molecules, which enhanced the stability of SBS-modified asphalt. Meanwhile, the addition of CNTs could improve the rheological properties, temperature susceptibility, and rutting resistance of SBS-modified asphalt at high temperatures. The heterogeneity between CNTs and SBS-modified asphalt was demonstrated and it was the key to the high-temperature performance improvement. Besides, the low-temperature performance also could be improved by appropriate CNTs content. In addition, the FTIR results suggested that there was a lack of change in chemical functional groups with CNTs modification in asphalt binder. Moreover, the CNTs had a limited impact on delaying oxidation and played an active role in enhancing high-temperature performance under different aging conditions.