Effect Of CNT Content Research Articles

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.

Effect of annealing and carbon nanotube infill on the mechanical and electrical properties of additively manufactured polyether-ether-ketone nanocomposites via fused filament fabrication

The light-weight, high-strength poly-ether-ether-ketone (PEEK) and its composite materials are the ideal candidate for a plethora of engineering applications. However, the inherent high viscosity and melting temperature of PEEK pose great challenges for the extrusion-based 3D printing process, leaving a wide knowledge gap on the properties and functionalities of novel PEEK-based composites. In this work, the PEEK/CNT composite filaments with different CNT content ranging from 1 to 7 wt% are prepared by single-screw extruder and subsequently printed with a custom-made high temperature 3D printer. The effects of CNT content and annealing on the mechanical strength and electrical conductivity of the 3D printed parts are investigated in detail. The tensile test result shows that the presence of CNT significantly enhances the mechanical strength of the composite. With 7 wt% CNT content, the maximum tensile strength and elastic modulus reaches 107.7 MPa and 1908.0 MPa, respectively, which amounts to a rise of 27.4% and 17.0% compared with the neat PEEK sample. The annealing treatment is similarly effective in strengthening the printed composites. The addition of CNT is also found to greatly improve the electrical conductivity to the PEEK, reaching 101 S/m for 7 wt% CNT. With such superior electrical conductivity, the printed PEEK/CNT composite sample exhibits outstanding electromagnetic interference (EMI) shielding performance, reaching 32.4 dB. However, additional annealing treatment decreases the electrical conductivity as wells as EMI shielding performance. Such decrease is mainly attributed to the growth of the crystals during annealing, which expels the CNTs to the grain boundaries and leads to remarkable agglomeration, which disconnects the pervasive conductive networks. The finding in this work can provide insights on the new designs of PEEK composite feedstock materials and cultivate new 3D printing strategies targeted specifically for highly-functional, high-strength novel composites.

Mechanical Properties, Melting and Crystallization Behaviors, and Morphology of Carbon Nanotubes/Continuous Carbon Fiber Reinforced Polyethylene Terephthalate Composites.

Carbon nanotube/continuous carbon fiber reinforced poly(ethylene terephthalate) (CNT/CCF/PET) composites are prepared by melt impregnating. The effects of CF and CNT content on the mechanical properties, melt and crystallization behaviors, and submicroscopic morphology of CNT/CCF/PET composites are studied. The tensile test results show that the increase of CF and the addition of appropriate amount of CNT improved the tensile strength and tensile modulus of the composites. When the content of CNT is 1.0 wt% and the content of CF is 56 wt%, the properties of the composites are the best, with tensile strength of 1728.7 MPa and tensile modulus of 25.1 GPa, which is much higher than that of traditional resin matrix composites. The results of dynamic mechanical analysis (DMA) show that the storage modulus of the composites increased with the increase of CF and CNT content. In particular, the addition of CNT greatly reduced the loss modulus of the composites. Morphological analysis show that the addition of CNT improved the fiber–matrix interface of the composite, which changes from fiber pull-out and fracture failure to fiber matrix fracture failure, and the fiber matrix interface is firmly bonded. In addition, there are polymer coated CNT protrusions on the surface of the fiber was observed. The results of differential scanning calorimetry (DSC) show that the melting temperature and crystallization temperature of the composites increased with the increase of CF content. The addition of CNT had little effect on the melting temperature of the composites, but it further improved the crystallization temperature of the composites. The effect of CNT content on the crystallization kinetics of the composites is studied. The non-isothermal crystallization kinetics of the composites is described by Jeziorny’s improved Avrami equation. The results show that CNT has a great influence on the crystallization type of the composites. As a nucleating agent, CNT has obvious heterogeneous nucleation effect in the composites, which improves the crystallization rate of PET.

Selective laser sintering of carbon nanotube–coated thermoplastic polyurethane: Mechanical, electrical, and piezoresistive properties

Flexible and electrically conductive carbon nanotube/thermoplastic polyurethane (CNT/TPU) nanocomposites have been herein fabricated by selective laser sintering (SLS) for the applications of wearable electronics and strain sensors. CNT/TPU nanocomposite powders were systematically developed by a latex-based technique. The effects of CNT content on the SLS processability of nanocomposite powders and the mechanical, electrical, and piezoresistive properties of SLS-printed specimens were investigated. It was found that the CNT improved the electrical conductivity and strain sensing performance of the printed parts, but excessively high CNT content led to high melt viscosity, deteriorated sintering behavior, and hence degraded mechanical properties. The 2.0 wt% CNT/TPU nanocomposite fabricated by SLS exhibited enhanced electrical conductivity (seven orders of magnitude higher than the neat TPU), high piezoresistive sensitivity (gauge factor of 60 at a tensile strain of 20%), and a wide sensing range (0‒130% strain). A mathematical model based on the tunneling theory was established to describe and predict the strain sensing performance of the printed nanocomposites. This study provides profound insights into the development of multi-functional nanocomposites by SLS for their applications in flexible strain sensors.

Hot rolling of MWCNTs reinforced Al matrix composites produced via spark plasma sintering

Aluminum/CNT nanocomposite sheets, with appropriate dispersion and interfacial bonding, were fabricated by a combination of powder metallurgy, spark plasma sintering (SPS), and hot rolling. The effects of CNT content as well as plastic deformation, on the microstructure and mechanical properties of the obtained nanocomposite, were investigated. The composite reinforced by 0.5 wt.% CNTs showed an optimal dispersion of CNTs into the aluminum matrix after both SPS and hot rolling. Minimum CNT damage and minimum carbide formation were observed after hot rolling. The best comprehensive mechanical properties corresponded to the sheet of Al-0.5 wt.% CNT nanocomposite thanks to the strong interfacial bonding between Al and CNTs, full densification of the nanocomposites as well as the uniform dispersion of the CNTs into the aluminum matrix. Hardness measurements showed that the maximum hardness was obtained for sheets containing 1.5 wt.% CNTs in both the as-SPS and the as-hot rolled conditions. Load transfer, Orowan, and grain size strengthening mechanisms could affect the increase of strength as well as the combination of strength and ductility of the sheets of Al-CNT nanocomposites.

Binary and Ternary Manganese Dioxide Composites Cathode for Aqueous Zinc‐ion Battery

AbstractMnO2 is a traditional cathode material for aqueous zinc‐ion battery (ZIB). However, its extensive use is limited by its poor conductivity and cycling performance. Design of binary or ternary MnO2 composites is a useful way to enhance the performance of MnO2. At first, a series of binary MnO2/carbon nanotube (CNT) composites with different CNT contents were synthesized by a facile co‐precipitation method. The effect of CNT content on the properties of binary composites was investigated. In addition, the ternary MnO2/CNT/polyaniline (PANI) composites were prepared to investigate the effect of unitary, binary and ternary composites on the MnO2. The results show that an appropriate content of CNT decreases the charge transfer resistance of the composite leading to a good electrochemical performance. The addition of PANI stabilizes the cycle performance of the composite at a cost of a slight decrease in the specific capacity.

Polyaniline/Carbon nanotube Electrochromic Films: Electrochemical Polymerization and characterization

Polyaniline/Carbon nanotube (PANI/CNT) composite films doped with dodecyl-benzene sulfonic acid were synthesized by cyclic voltammetry on an ITO-coated glass substrate. FTIR, XRD and electrochemical analyzer were used to characterize the micro-morphology, chemical structure, crystallinity and electrochromic behavior of the films, respectively. The effect of CNT content on the properties of the films was investigated. Results show that the introducing CNTs make aniline polymerize easier than before. Within a range, the conductivity and crystallinity of PANI/CNT composites improves with CNT content increasing. The electrochromic device made from the PAN/CNT film with a CNT content of 2.5wt% presents a reflectance contrast of 38.8%, a mean response time of 2.3s and a coloration efficiency of 386.4cm2/C at 540nm. The PAN/CNT film shows better electrochromic behaviors due to some interaction between CNTs and the PANI backbones than PANI film.

Effect of multi-walled carbon nanotubes on the physical properties and crystallisation of recycled PET/TPU composites.

Thermoplastic polyurethane (TPU) was blended with recycled polyethylene terephthalate (rPET) to prepare rPET/thermoplastic polyurethane (TPU) composites. Meanwhile, multiple-walled carbon nanotubes (MWCNTs) were employed as a reinforcing filler to study the synergistic effect between CNTs and rPET/TPU composites. The effect of CNT content on the morphology and micro-structure of the composites was investigated using a scanning electron microscope (SEM) and X-ray diffraction (XRD). The thermal properties were characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The mechanical properties were investigated using tensile tests and hardness measurements. The results showed that TPU was compatible with rPET. The existence of rPET changed the crystalline phase and affected the glass transition and crystallisation temperature of the TPU matrix. The rPET/TPU composites displayed poor thermal stability and tensile properties when compared to pure TPU. The addition of CNTs had no effect on the crystalline phase of the rPET/TPU composites. Due to the occurrence of interfacial adhesion between the CNTs and rPET, the CNTs displayed an offset effect on the reaction of rPET and decreased the rigidity of the molecular chain in the rPET/TPU composites. The thermal stability and tensile strength of the CNTs/rPET/TPU composites improved with an increase in CNT content.

The preparation and characteristic of maleic anhydride grafted polyethylene (PE-g-MA) filled CNT/PMMA composite film

ABSTRACTIn order to improve the tribological properties of PMMA, the PMMA composites incorporated with CNT powders were prepared. The effect of CNT content on tribological properties of the composites was investigated. When CNT content is 0.5 wt%, the friction coefficients of the 0.5%CNT/PMMA composite are the smallest, which are about 0.15 and are 67% less than those of the pure PMMA composite, and its wear resistance remains the same as the pure PMMA composite. Incorporating 0.5 wt% CNT into the PMMA composite may develop a continuous transferred film on the worn surface. As a result, the friction coefficients of the composite are reduced and its wear mechanism is mainly fatigue spalling. The addition of PE-g-MA improved the friction and wear properties of CNT/PMMA composite.

Effect of processing methods on electrical percolation and electromagnetic shielding of PC/MWCNTs nanocomposites

Nanocomposites of polycarbonate (PC)/multiwalled carbon nanotubes (MWCNTs) containing 0.5–3 wt% of MWCNTs were prepared via two methods of melt mixing and solution mixing. The effect of CNT content and processing methods on electrical and electromagnetic properties of nanocomposite samples were investigated. TEM microphotographs revealed that the PC/MWCNT composites prepared by the solution method, have better dispersion and distribution of CNTs in the PC matrix. Electrical measurements indicated an electrical percolation threshold of less than 1 wt% of CNTs for this system. Also, it was found that PC/MWCNT composites prepared by the solution method, exhibit higher electrical conductivity and lower electrical percolation threshold. The electromagnetic interference shielding effectiveness (EMI SE) measurements in the X‐band (8.2–12.4 GHz) indicated that EMI SE is increased by increasing the amount of CNTs in the samples, and also the thickness of specimens. In addition, the results showed that the composites prepared by the solution method, have higher SE values. Finally, in order to reach an acceptable value for commercial applications of EMI shielding materials (20 dB), thicker samples were produced and it was found that the 3.5 mm thick samples containing 2 wt% CNTs, have a 19.6 dB shielding effectiveness. POLYM. COMPOS., 38:E269–E276, 2017. © 2016 Society of Plastics Engineers

Effects of carbon nanotube content and annealing temperature on the hardness of CNT reinforced aluminum nanocomposites processed by the high pressure torsion technique

In this paper, the microstructure and hardness of CNT reinforced aluminium (CNT/Al) nanocomposites prepared by the advanced powder metallurgy method and subsequently processed by the high pressure torsion (HPT) technique are studied. The effects of CNT content and annealing temperature on the hardness of the nanocomposites are investigated. The results show that annealing materials at temperatures below 150°C leads to secondary hardening, while annealing at higher temperatures soften the nanocomposites. HPT-processed CNT/Al nanocomposites with 1.5wt.% of CNTs are shown to have the highest hardness in comparison with other composites containing CNTs from 0 up to 2wt.%. Microstructures, CNT distribution and the phase composition of CNT/Al nanocomposites are investigated by transmission and scanning electron microscopy and X-ray diffraction techniques.

Mechanical and tribological performances of polypropylene composites containing multi-walled carbon nanotubes

Polypropylene (PP)-based composites filled with as-received carbon nanotubes (ASCNTs) and purified carbon nanotubes (PCNTs) at different weight percentages were prepared using twin-screw extrusion and injection moulding. The effects of CNT content and purification procedure on the mechanical properties and wear resistance were examined. The results showed that microhardness, Young’s modulus, tensile strength, and wear resistance values of the composites increased after purification procedure compared to the ASCNT-based composites, due to the fact that the enhanced interactions between CNT and PP improved the load transfer efficiency from PP to CNTs. For the composites prepared with both ASCNT and PCNT, as the loading of the CNTs increased, improved mechanical properties and wear resistance were observed. However, the mechanical properties and wear resistance decreased when the CNT content exceeded 0.8 wt.% due to agglomeration of CNTs.

Carbon nanotube reinforced shape memory polyurethane foam

Multiwalled carbon nanotube (MWCNT)/polyurethane (PU) foams have been synthesized from polypropylene glycol and 2,4/2,6-toluene diisocyanate following the one-shot foaming method in the presence of water as the chemical blowing agent. The effects of CNT content on the performances of the foams have been analyzed in terms of reactivity, mechanical and dynamic mechanical properties, and shape memory properties of the foams. It was found that the cream time, rise time, tensile, and compressive strengths at room temperature, glassy and rubbery state moduli, glass-transitional temperature (T g), and shape fixity and shape recovery increased with the addition and increasing amount of MWCNT.

Age Hardening Behavior of Carbon Nanotube Reinforced Aluminum Nanocomposites

In the present work, age hardening behavior of CNT reinforced Al6061 and Al2124 nanocomposites, prepared by ball milling and spark plasma sintering, was investigated. The effect of CNT content, annealing time and temperature on the age hardening behavior of the nanocomposites was evaluated and compared to the monolithic alloys prepared and age hardened under the same conditions. It was found that CNTs have a negative influence on the age hardening of the alloys. The alloys displayed standard age hardening behavior i.e. a sharp increase in hardness during initial aging followed by a steady decrease in hardness. Whereas the nanocomposites did not only display initial softening during aging but also showed reduced age hardening efficiency. The hardening efficiency was found to decrease with increasing CNT content. The complicated behavior of nanocomposites was explained in terms of dislocation recovery, large thermal mismatch between matrix and CNTs and bulk microstructure of the composites.