CNT Content Research Articles

Fracture analysis of CNT reinforced FG structures under thermo-mechanical loading using XIGA framework

This paper discusses the fracture analysis of FG structures reinforced by CNT exposed to thermo-mechanical load by means of the XIGA framework. The equivalent properties of functionally graded structures reinforced by CNT (SWCNT & MWCNT) are computed using micro-mechanics models. The volume fraction of CNT has an impact on the mechanical and thermal properties. Then, a preexisting crack is considered in the CNT reinforced FG square structure to perform the fracture analysis. The SIFs are calculated by the interaction integral method. It is noted that delaying of the fracture is possible with the increase of CNT content in FG structure.

A novel carbon nanotubes doped natural rubber nanocomposite with balanced dynamic shear properties and energy dissipation for wave energy applications

Mechanical characterizations of natural rubber filled with carbon-based nanomaterials were extensively studied in tensile and tear modes whereas fewer attempts have been conducted on a dynamic shear condition using a double-bonded shear test piece. This is of importance since natural rubbers are widely used as flexible membranes for wave energy harvesting devices. Therefore, this study was aimed to explore the microstructural, rheological, and dynamic viscoelastic characteristics of natural rubbers filled with different Multi-Walled Carbon Nanotubes (MWCNTs) contents. A combined compounding approach was employed to ensure a homogenous CNT dispersion was achieved. Transmission electron microscopy (TEM) was performed for the materials characterization while the processability and curing parameters of the compounds were investigated using the Mooney viscosity and rheometry test. Dynamic shear properties were compared using a cyclic test performed on a double-bonded shear test piece. TEM images showed that an optimum CNTs dispersion was reached at 3 phr MWCNTs loading whereas increasing CNT content resulted in further inhomogeneity. The addition of CNTs into the natural rubber not only improved the curing properties of the compound, i.e., low scorch and curing times, but it also increased the Mooney viscosity, the rheological properties, and the dynamic shear properties of the nanocomposite compared to the pristine rubber. The Payne and Mullins effects were also observed for all compounds manifesting dependency on the CNTs content and applied strain amplitude. Finally, MWCNT enhanced the dissipated energy of the nanocomposites with respect to the neat rubber in which an increase of 1040 % in energy dissipation for 10 phr MWCNTs compared to the control at a strain amplitude of 200 % was achieved.

Effect of carbon nanotube incorporation on the evolution of morphology, phase and compositional homogeneity, surface oxide chemistry and corrosion behaviour of electrodeposited FeCuMnNiCo-carbon nanotube composite coatings

The effect of addition of various concentration of Multi-walled Carbon Nanotubes (0.05, 0.1, 2.5, 5.0, 15.0, 25.0 mg/L) on the corrosion resistance of FeCuMnNiCo high-entropy alloy composite coatings synthesized by electrodeposition method was investigated. The idea behind the reinforcement of CNTs into High Entropy Alloy (HEA) coatings was to utilise the chemical inertness and hydrophobic nature of CNTs which could enhance corrosion resistance behaviour. The experimental results reveal that concentration of CNT had a major effect on microstructure, composition and roughness ultimately influencing electrochemical behaviour of coatings. Owing to the uniform dispersion, till the optimum concentration, CNT played a vital role in homogenizing the composition, making the composite coating surface more smooth, fine-grained, compact with enhanced hydrophobicity (contact angle from 81.250 to 144.70) .Beyond this threshold, non-uniformly dispersed, agglomerated CNTs led to formation of surface defects thus adversely affecting corrosion resistance by promoting galvanic coupling. It was noticed that the nature of passive oxide layer formed on the coating surface had a direct corelation with the corrosion behaviour. As compared to FeCuMnNiCo, the one with 12.50 mg/L CNT had more protective oxides formed in form of stable Feox+2,Ni+2 and Co+3 oxides which led to an increase in protection efficiency by 87.14%.

Enhancing the tensile properties of PA6/CNT nanocomposite in selective laser sintering process

AbstractThe aim of present study is to enhance the tensile strength, elongation at break and tensile modulus of polyamide 6/carbon nanotube (PA6/CNT) nanocomposite prepared by selective laser sintering. For this purpose, the optimal values of laser power, scanning speed and CNT content were estimated to enhance the tensile properties of PA6/CNT nanocomposite by using the response surface methodology and desirability function. The microstructure of specimens was observed using the scanning and transmission electron microscopy. It was observed that an increase in laser power from 5 to 10 W improved the tensile strength (21%) and elongation at break (11.4%) of the nanocomposite due to uniform dispersion of CNTs, while the further increase of laser power reduced the tensile strength (5.2%), elongation at break (5.8%) and tensile modulus (5.3%) due to thermal degradation of PA6 polymer. A rise of the scanning speed from 1000 to 2000 mm/s was associated with a reduction in the tensile strength, elongation at break and tensile modulus by about 8.3%, 13% and 3.3% respectively, which was due to lower heat input and consequently incomplete densification of the nanocomposite. The addition of CNTs up to 5 wt% can enhance the tensile properties of PA6/CNT nanocomposite, but needs increasing the laser power. The best combination of tensile properties was achieved at laser power of 7.3 W, scanning speed of 1000 mm/s and CNT content of 1.8 wt%. Moreover, the addition of CNTs up to 5 wt% showed a slight influence on thermal stability and crystallinity of the sintered nanocomposite.

Durable photocatalytic membrane of PAN/TiO2/CNT for methylene blue removal through a cross-flow membrane reactor

ABSTRACT PAN/TiO2/CNT and PAN/TiO2/CNT-PVA composite nanofibrous membranes with photocatalytic activity were successfully synthesized using electrospinning. The effect of CNT concentration and PVA coating on the membrane surface toward the membrane performances was investigated. TiO2 anatase phase was exist on the respective membranes. SEM morphological investigation revealed the random orientation of the nanofibers with beads decorated in each strand. The PAN/TiO2/CNT composite nanofiber membrane exhibited high performance for the removal of cationic organic dye methylene blue (MB) in a cross-flow photocatalytic membrane reactor under low power visible light of LED lamp (14.5 W) and a constant pollutant flow rate of 0.21 L/min. The presence of TiO2/CNT photocatalyst was proven to prolong the lifetime of the photocatalytic membrane and retard membrane fouling to the maximum extent. PAN/TiO2/CNT membrane has displayed 100% MB rejection for the first 8 h of operation. Both, PAN/TiO2/CNT and PAN/TiO2/CNT-PVA maintained their membrane performances and did not show major flux decline even after five recycling uses. The incorporation of TiO2/CNTs on PAN nanofibers has resulted in a durable photocatalytic membrane for the effective removal of dye waste using a cross-flow membrane reactor.

Construction and Adsorption Performance Study of GO-CNT/Activated Carbon Composites for High Efficient Adsorption of Pollutants in Wastewater.

Based on the increasing application requirements for the efficient adsorption of wastewater pollutants, graphene oxide-carbon nanotube/activated carbon (GO-CNT/AC) composites are constructed from the optimal microstructure matching of GO, CNTs, and AC materials by solution impregnation and freeze-drying methods. Three-dimensional structures with nano-micro hierarchical pores are established, with GO and CNTs uniformly dispersed on the AC surface, effectively restrain the agglomeration. The added CNTs played a "spring" role, supporting the gap between the GO sheets and AC matrix. Meanwhile, stable links are formed between GO, CNTs, and AC, realizing the synergistic matching of the microstructure, which provides abundant active absorption sites beneficial for improving the adsorption performance. The influences of the CNT contents, adsorbent amounts, methylene blue (MB) concentrations, and pH values on the adsorption property of GO-CNT/AC composites are systematically investigated. The results show that when the pH value of the MB solution is 13, the CNT concentration is 3 mg/mL and the MB concentration is 200 mg/L, the adsorption property of the composite is the best, with an adsorption capacity of 190.8 mg/g and a removal percentage of 95.4%. Compared with the raw AC, the adsorption capacity and removal percentage of the composites are increased by 73.9% and 72.8%, respectively. The GO-CNT/AC composites exhibit excellent cyclic adsorption performance, with a cyclic stability of 91.8% after six rounds of adsorption-desorption cycles. The kinetic analysis shows that the adsorption process conforms to the PSO kinetic model. By fitting of the IPD model, the adsorption mechanisms of the GO-CNT/AC composites are divided into two adsorption stages and described respectively. This study provides a new way to achieve highly efficient adsorption of pollutants in wastewater.

Multisensory Systems Based on Perfluorosulfonic Acid Membranes Modified with Functionalized CNTs for Determination of Sulfamethoxazole and Trimethoprim in Pharmaceuticals.

Sulfamethoxazole and trimethoprim are synthetic bacteriostatic drugs. A potentiometric multisensory system for the analysis of sulfamethoxazole and trimethoprim combination drugs was developed. Perfluorosulfonic acid membranes containing functionalized CNTs were used as the sensor materials. The CNTs' surface was modified by carboxyl, sulfonic acid, or (3-aminopropyl)trimethoxysilanol groups. The influence of the CNT concentration and the properties of their surface, as well as preliminary ultrasonic treatment of the polymer and CNT solution before the casting of hybrid membranes, on their ion-exchange capacity, water uptake, and transport properties was revealed. Cross-sensitivity of the sensors to the analytes was achieved due to ion exchange and hydrophobic interactions with hybrid membranes. An array of cross-sensitive sensors based on the membranes containing 1.0 wt% of CNTs with sulfonic acid or (3-aminopropyl)trimethoxysilanol groups enabled us to provide the simultaneous determination of sulfamethoxazole and trimethoprim in aqueous solutions with a concentration ranging from 1.0 × 10-5 to 1.0 × 10-3 M (pH 4.53-8.31). The detection limits of sulfamethoxazole and trimethoprim were 3.5 × 10-7 and 1.3 × 10-7 М. The relative errors of sulfamethoxazole and trimethoprim determination in the combination drug as compared with the content declared by the manufacturer were 4% (at 6% RSD) and 5% (at 7% RSD).

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.

Carbon nanotubes boosts the toughness and conductivity of wet-spun MXene fibers for fiber-shaped super capacitors

Mechanically strong and electrically conducting fibers, particularly those with high specific capacitances, are promising fiber-shaped electrodes for fiber- and textile-based energy storage devices like fiber-shaped supercapacitors (FSCs). However, a high loading of fillers or bridging agents is commonly required to fabricate fiber electrodes with good mechanical strength, which compromises electrical conductivity and energy storage performance. Herein, an easily scalable wet-spinning strategy is reported to fabricate multifunctional Ti3C2Tx MXene/carbon nanotubes (MXene/CNT) hybrid fibers from a harmonious mixture of MXene and CNT in water and using acetic acid as a coagulation bath. The hybrid fiber achieved high strength (61 ± 7 MPa), good conductivity (1142.08 ± 40.04 S cm−1) and excellent energy storage performance (∼295 F g−1 at 5 mV s−1) at a very low CNT content of ∼1 wt%. When CNT loading increased to ∼9 wt%, the maximum strain at broken reached 161 ± 19 MPa and conductivity further increased to 1715 ± 22 S cm−1. The excellent mechanical performance allows hybrid fibers to be knitted into textiles for energy storage textiles. The assembled FSCs exhibit energy and power densities of ∼6.08 mW h cm−3 and ∼6440 mW cm−3, respectively. The excellent performance of MXene/CNT fiber and good feasibility for scalable production will open up new opportunities for the development of wearable and textile-based devices in the near future.

Development of a TPU/CNT/Cu Composite Conductive Filament with a High CNT Concentration

Development of a TPU/CNT/Cu Composite Conductive Filament with a High CNT Concentration

Bio-based formulation of an electrically conductive ink with high potential for additive manufacturing by direct ink writing

In this work, a new ink formulation based on the use of a fully bio-based thermosetting resin as a binder, cellulose powders as rheology modifiers, and carbon nanotubes as conductive fillers was developed, and its potential as a functional material for additive manufacturing by direct ink writing was demonstrated. Electrical and rheological characterization of the nanocomposite at increasing CNT and cellulose concentrations was conducted in order to determine the optimal processing conditions and the printability window for the system. In addition, the resulting nanocomposite was further carbonized to yield a carbon-carbon nanocomposite with a better electrical conductivity. The results of the present study open the possibility of either integrating conductive circuits in a 3D-printed structure, or the printing of a bulk semi-conductive complex structure using a low-cost DIW 3D printing technique and mostly cost-effective renewable raw materials.

Electromechanical impedance-based embeddable smart composite for condition-state monitoring

In the present study, an alternating current (AC) based electro-mechanical impedance (EMI) technique was employed to evaluate the performance of smart cementitious composite-based impedance sensor (SCC- i S) over a frequency range, and then was employed as embeddable sensor for monitoring and assessing the health of concrete structure. For this purpose, a method for developing SCC-iS by reinforcing the carboxylic group (COOH-) multi-walled carbon nanotube (COOH-MWCNT) in the cementitious composite matrix is described. The optimal CNT concentration in SCC- i S was obtained based on the AC impedance measurement technique over a specified frequency range. After finding the optimal CNT concentration in SCC- i S, their piezoresistive behaviour (in terms of change in electrical impedance or electrical conductance) was examined using an electro-mechanical impedance measurement approach under uniaxial compressive loading. Finally, the developed sensor is employed as an embedded sensor for damage monitoring of structures under flexural loading. The acquired electrical impedance- and conductance- responses from the SCC- i S were utilized to evaluate the occurrence and progression of damage in real-time. The damage metric and the shift in frequency band were used to quantify the level of damage in the structures. From the experimental study, 0.50 wt% CNT concentration is found to be optimum for developing the efficient SCC- i S. Under the uniaxial compressive loading, the electrical variation in impedance (EVZ) and electrical variation in conductance (EVC) in SCC- i S exhibit excellent correlation with compressive strain and are capable of detecting the damage. The acquired signals from embedded SCC- i S show the effectiveness and sensitivity (in both qualitative and quantitative terms) for damage monitoring of structures; even they are capable of tracing the early-stage damage initiation in concrete structures. The electrical conductance spectra within a specified frequency range show a leftward shift, indicating the degradation in stiffness of concrete structure. Overall, the developed SCC- i S is the first of its kind and is found to be very effective and durable for real-time monitoring of structures, especially in the aggressive environment. • Development of smart nanoengineered composite using functionalized CNT. • Embedded sensors for capturing the electro-mechanical impedance (EMI) signature. • Sensor characterization and evaluation of piezoresistive behavior in frequency bands. • Demonstration for damage monitoring of structures under flexural loading. • Damage metric and shift in frequency band for accurate damage quantification.

High temperature erosion behaviour of high-velocity oxy-fuel sprayed CNT/NiCr-Cr3C2 composite coatings

In the present work, the effect of different weight percentages of carbon nanotubes on the high-temperature erosion behaviour of NiCr-Cr3C2 composite coatings is demonstrated. The high-velocity oxy-fuel (HVOF) spraying process was employed for the deposition of coatings on ferritic low-alloy steel (SA-213 T12). The solid particle erosion test of the coating with and without carbon nanotubes was conducted at a temperature of 600 °C with 30, 45, 60, and 90° impact angles using Al2O3 erodent particles. This work exhibited high erosion resistance for composite coatings with the highest CNT content of 7 %. However, as the impact angle was increased from 30° to 90°, the erosion rate of all coatings, irrespective of CNT content, increased. An Optical 3-Dimensional Profilometer was used to estimate lower crater depths for lower impact angles and deeper crater depths for higher impact angles observed through surface topography. The effect of the addition of CNTs in NiCr-Cr3C2 coatings resulted in a reduction in weight loss and erosion rate at different angles of impingement working under high temperatures. The outstanding mechanical properties of CNTs impart improved erosion resistance.

Facial Preparation of Segregated Poly(butylene succinate)/Carbon Nanotubes Composite Foams with Superior Conductive Properties via Synergistic Effect of High Pressure Solid Phase Molding and Supercritical Fluid Foaming

AbstractConductive polymer composites (CPCs) have been demonstrated to have many advantages. However, agglomeration of conductive fillers or segregation of conductive networks in CPCs always results in weak mechanical properties and limited conductivity. To address this issue, four types of poly(butylene succinate)/multiwalled carbon nanotube (PBS/CNT) CPC with different conductive network structures are prepared: PBS/CNT‐I: melt mixing with hot pressing (145 °C, 10 MPa), PBS/CNT‐II: solution mixing with hot pressing (145 °C, 10 MPa), PBS/CNT‐III: solution mixing with hot pressing (100 °C, 10 MPa), PBS/CNT‐IV: solution mixing with hot pressing (100 °C, 60 MPa). The results show that PBS/CNT‐IV CPC has the highest mechanical properties, conductivity, and thermal conductivity. Tensile strength, elongation at break and Young's modulus of PBS/CNT‐IV are 119%, 58%, and 37% higher than that of PBS/CNT‐III CPC, respectively. Subsequently, PBS/CNT‐IV CPCs with different CNT contents are prepared. The mechanical, crystallization, electrical and thermal conductivities, and rheological properties as well as foamability are studied. Compared with PBS/5.0 wt.% CNT‐IV CPC, the foamed specimen shows 97% enhancement in conductivity. In general, this work offers a simple, environmentally‐friendly approach for manufacturing CPC with high conductivity and good mechanical property and is instructive for construction of a segregated network structure in low‐melt‐viscosity semi‐crystalline polymer.

3D printing of ABS Nanocomposites. Comparison of processing and effects of multi-wall and single-wall carbon nanotubes on thermal, mechanical and electrical properties

• Multi-Wall and Single-Wall carbon nanotubes affect thermoelectrical behavior. • Fuse Filament Fabrication of conductive nanocomposites at selected low resistivity. • 3D manufactured nanocomposites with applications for thermoelectric devices/sensors. • Anisotropy in electro-mechanical behaviour of multilayer nanocomposites. • Conductivity of CNT composites depends on filler content, process and geometry. The following paper reports on a comparative study of the effects of two types of carbon nanotubes, namely multiwall (MWCNT) and single-wall (SWCNT) carbon nanotube, on the properties of 3D-printed parts produced with acrylonitrile-butadiene-styrene (ABS) nanocomposites with various CNT loadings of 5-10 wt.%. Quasi-static tensile properties and Vicat softening temperature of 3D-printed parts were enhanced with the increasing CNT content. The highest enhancement in tensile properties was observed for the ABS/CNT nanocomposites at 10 wt.% filler loading. 3D-printed ABS/SWCNT composites showed higher tensile modulus, better creep stability and higher Vicat temperature. However, the strength of ABS/SWCNT 3D samples is relatively lower than that of ABS/MWCNT. In addition, 3D-printed parts exhibited anisotropic electrical conductive behaviour, which has a conductivity of through-layer of about 2-3 orders of magnitude higher than cross-layer. The highest conductivity of 3D-printed samples reached 25.2 S/m, and 9.3 S/m for ABS/MWCNT and ABS/SWCNT composites at 10 wt.%, respectively. The results obtained, i.e. the successful fuse filament fabrication and the consequent electromechanical properties, confirm that these 3D printable nanocomposite could be properly utilized for the production, and application up to about 90 °C, of thermoelectric devices and/or resistors for flexible circuits.

Multiwalled Carbon Nanotubes Alter the PSII Photochemistry, Photosystem-Related Gene Expressions, and Chloroplastic Antioxidant System in Zea mays under Copper Toxicity.

A critical approach against copper (Cu) toxicity is the use of carbon nanomaterials (CNMs). However, the effect of CNMs on Cu toxicity-exposed chloroplasts is not clear. The photosynthetic, genetic, and biochemical effects of multiwalled carbon nanotubes (50-100-250 mg L-1 CNT) were investigated under Cu stress (50-100 μM CuSO4) in Zea mays chloroplasts. Fv/Fm and Fv/Fo were suppressed under stress. Stress altered the antioxidant system and the expression of psaA, psaB, psbA, and psbD. The chloroplastic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione S-transferase (GST), and glutathione peroxidase (GPX) increased under CNT + stress, and those of hydrogen peroxide (H2O2) and lipid peroxidation decreased. CNTs were promoted to the maintenance of the redox state by regulating enzyme/non-enzyme activity/contents involved in the AsA-GSH cycle. Furthermore, CNTs inverted the negative effects of Cu by upregulating the transcriptions of photosystem-related genes. However, the high CNT concentration had adverse effects on the antioxidant capacity. CNT has great potential to confer tolerance by reducing Cu-induced damage and protecting the biochemical reactions of photosynthesis.

Carboxymethylcellulose-polyaniline/carbon nanotube (CMC-PANI/CNT) film as flexible and highly electrochemical active electrode for supercapacitors

Herein, we demonstrate a flexible, structural robust and highly electrochemical active film electrode based on evenly distributed carboxymethylcellulose-polyaniline/carbon nanotube (CMC-PANI/CNT) for supercapacitors. In this process, vertically aligned PANI nanoparticles grow in an orderly manner on CMC fibers. The highly dispersed CNT nanomaterials are then introduced by simple layer-by-layer assembly, eventually forming an interwoven network structure. Mechanical tests have shown that the obtained CMC-PANI/CNT film exhibit excellent robustness and flexibility, and can be used directly as electrodes without any conductive additives and binders. The CMC-PANI/CNT electrode with optimal CMC, PANI and CNT contents demonstrates an excellent area specific capacitance of 3106.3 mF cm−2 at 5 mA cm−2 and a gravimetric specific capacitance of 348.8 F g−1 at 0.5 A g−1. Furthermore, the symmetric supercapacitor (SSC) assembled with CMC-PANI/CNT exhibits a high energy density of 99.89 μW h cm−2 at a power density of 400.02 μW cm−2, and a good cycling stability (with capacitance retention of 89.2 % after 5000 cycles). The cost-effective and eco-friendly preparation method of free-standing CMC-PANI/CNT film electrodes provide a novel insight for developing flexible energy storage devices.

Influence of Soft Phase and Carbon Nanotube Content on the Properties of Hierarchical AZ61 Matrix Composite with Isolated Soft Phase.

Carbon nanotube-reinforced magnesium matrix (CNTs/Mg) composite has great application potential in the transportation industry, but the trade-off between strength and ductility inhibits its widespread application. In order to balance the strength and plasticity of the composite, in this work, on the basis of the AZ61 matrix composite homogeneously reinforced by Ni-coated CNTs (hard phase), 30 vol.% large-size AZ61 particles are introduced as an isolated soft phase to fabricate hierarchical CNTs/AZ61 composites. The compression tests show the fracture strain and compressive strength of this composite increases by 54% and 8%, respectively, compared with homogeneous CNTs/AZ61 composite. During deformation, the hard phase is mainly responsible for bearing the load and bringing high strength, due to the precipitation of the Mg17Al12 phase, uniformly dispersed CNT and strong interfacial bonding of the CNTs/Mg interface through nickel plating and interfacial chemical reaction. Furthermore, the toughening of the soft phase results in high ductility. With the increase in CNT content, the compressive strength of composites is nearly unchanged but the fracture strain gradually decreases due to the stress concentration of CNT and its agglomeration.

Multiscale hybrid CNT and CF reinforced PEEK composites with enhanced EMI properties

Due to ever increasing use of telecommunication and electronic devices in offshore and stealth technology sectors, developing highly-efficient electromagnetic interference (EMI) shielding materials with good thermal resistance are urgently required. In this paper, the effect of MWCNTs incorporation on the mechanical, interlaminar bonding and EMI performance of MWCNT/CF/PEEK composites were firstly studied. The introduction of interlaminar MWCNTs did not affect the tensile strength and modulus significantly at low loadings whilst slight decrease in them was seen beyond a MWCNT content of 2.5 g/m2 due to the presence of CNT clusters. Improvement in the flexural strength and modulus as well as interlaminar bonding were achieved, reaching the peak values at an interlaminar MWCNT content of 1.5 g/m2. This is because the existence of inter-ply CNTs improves the stiffness and strength of the interlaminar region in shear when the material is subjected to bending moment. EMI shielding effectiveness of the laminates was markedly enhanced by 76% at an interlaminar CNT content as low as 2.5 g/m2 (equivalent to 0.53 wt.%). For the first time, this work has demonstrated the effectiveness and high efficiency of utilizing a multilayer structural design with the CNTs spray coated at the interlaminar region to improve the EMI shielding performance of CF/PEEK composites.

Stability of Carboxyl-Functionalized Carbon Nanotubes in Simulated Cement Pore Solution and Its Effect on the Compressive Strength and Porosity of Cement-Based Nanocomposites

The application of carbon nanotubes to produce cementitious composites has been extensively researched. However, the dispersion of this nanomaterial remains a technical limitation for its use. Thus, initially, this study assessed the stability of carboxyl-functionalized CNT on aqueous suspensions and simulated cement pore solution for 6 h through UV–visible spectroscopy. Subsequently, a CNT content of 0.1% by cement weight was incorporated into the cement pastes, and the compressive strength after 7, 14, 28, and 91 days was evaluated. In addition, the porosity of the CNT cementitious composites at 28 days of hydration was investigated by mercury intrusion porosimetry (MIP), and the microstructure was evaluated via scanning electron microscopy (SEM). The simulated cement pore solution’s alkaline environment affects the CNT stability, progressively reducing the dispersed CNT concentration over time. CNT reduced the cementitious matrix pores < 50 nm by 8.5%; however, it resulted in an increase of 4.5% in pores > 50 nm. Thus, CNT incorporation did not significantly affect the compressive strength of cement pastes. SEM results also suggested a high porosity of CNT cementitious composites. The CNT agglomeration trend in an alkaline environment affected the CNT performance in cement-based nanocomposites.