Multi-walled Carbon Nanotubes Weight Research Articles

Effectiveness of multi‐walled carbon nanotube on the improvement of tensile, flexural, and low‐velocity impact properties of hybrid Kevlar/carbon fiber reinforced epoxy‐based composites

AbstractIn this study, the effects of hybridizing carbon fibers with Kevlar fibers and incorporating multiwalled carbon nanotube (MWCNT) particles on low‐velocity impact, tensile, and flexural performance were evaluated experimentally. A manual lay‐up procedure followed by vacuum bag molding was used to construct hybrid composites (carbon and Kevlar) with and without MWCNTs, as well as hybrid composites with varying MWCNT weight ratios of carbon and Kevlar fiber reinforcements. When 0.1 wt% of MWCNT was added to the epoxy to enhance absorbed energy and peak load, the maximum improvements observed were 31% and 28%, respectively. The addition of MWCNTs by 0.5 wt% to the epoxy enhanced the flexural strength and flexural modulus by 66% and 41%, and by 5% with 0.1 wt% and 12.3% with 0.5 wt% MWCNT for tensile strength and tensile modulus, respectively. These improvements were observed in both tensile strength and tensile modulus. As for (C5K10C5), the maximum improvements in absorbed energy and peak load were observed to be 11.2% and 31%, respectively, corresponding to a 0.1 wt% MWCNT addition, whereas the maximum improvement in flexural strength and flexural modulus was 12.28% and 44%, respectively, with a 0.1 wt% MWCNT. These improvements in mechanical properties are primarily attributed to the enhanced stress transfer properties from fibers and nanoparticles to the matrix. This enhancement is a result of the strong interfacial interactions between epoxy and MWCNT nanoparticles.Highlights MWCNT inclusion effects on mechanical properties of carbon/Kevlar hybrid composites. MWCNT inclusion effects on low‐velocity impact properties of Carbon/Kevlar hybrid composites. The effects of Kevlar and carbon stacking sequence with MWCNT incorporation were investigated.

Fabrication and Characterization of Electrically Conductive 3D Printable TPU/MWCNT Filaments for Strain Sensing in Large Deformation Conditions

AbstractThis study investigates the development of thermoplastic polyurethane (TPU) filaments incorporating multi‐walled carbon nanotubes (MWCNT) to enhance strain‐sensing capabilities. Various MWCNT reinforcement ratios are used to produce customized feedstock for fused filament fabrication (FFF) 3D printing. Mechanical properties and the piezoresistive response of samples printed with these multifunctional filaments are concurrently evaluated. Surface morphology and microstructural observations reveal that higher MWCNT weight percentages increase filament surface roughness and rigidity. The microstructural modifications directly influence the tensile strength and strain energy of the printed samples. The study identifies an apparent percolation threshold within the 10–12 wt.% MWCNT range, indicating the formation of a conductive network. At this threshold, higher gauge factors are achieved at lower strains. A newly introduced Electro‐Mechanical Sensitivity Ratio (ESR) parameter enables the classification of composite behaviors into two distinct zones, offering the ability to tailor self‐sensing structures with on‐demand properties. Finally, flexible structures with proven application in soft robotics and shape morphing are fabricated and tested at different loading conditions to demonstrate the potential applicability of the custom filaments produced. The results highlight a pronounced piezoresistive response and superior load‐bearing performance in the examined structures.

Quasi-static puncture shear loading behaviour MWCNT/glass fibre epoxy laminates with various indenters

Investigation was performed to evaluate the puncture resistance of multi-walled carbon nanotubes (MWCNTs)/glass fibre epoxy laminate composites using different indenters (conical, elliptical, flat, and hemispherical). For the puncture tests, MWCNT weight percentage and indenter type were varied. Furthermore, the impact of MWCNT on tensile, flexural, and interlaminar shear strength was evaluated. Ultrasonic C-scan provided insights into the damage evolution and failure mechanisms of the laminates under puncture. The results indicate that the flat indenter exhibits prolonged indentation time and enhanced energy absorption, resulting in a disc-shaped failure pattern. On the other hand, the conical indenter demonstrates rapid penetration due to its smaller contact surface area. The elliptical indenter generates higher frictional energy, leading to bulging damage. The hemispherical indenter showed an even distribution of force across the impacted surface, minimizing force concentration and reducing the extent of damage. These findings shed light on the puncture mechanisms of MWCNT/Glass fibre epoxy laminate composites, paving the way for more precise glass fibre laminate composite design and optimisation in practical applications such as aerospace, automotive, and sporting goods, where puncture loading is a critical consideration.

Developing a steady state wear equation for AA7050 hybrid composites/steel interface at elevated temperature

ABSTRACT In this research work, an attempt was made to reinforce AA7050/5Gr composites with multi-walled carbon nanotube (MWCNT) of varying weight percentages processed through stir casting route. SEM with EDS mapping revealed that the particles were uniformly distributed over the composites. Hardness reduces with increasing MWCNT weight percentage owing to the inverse hall petch effect and increment in void content. A third-body abrasion, which happens when the CNT in the aluminium matrix material detaches from the surface and erodes material from the composites pin as well as the counter face, causes the wear resistance to rise with the addition of CNT particles. A mechanically mixed layer, which avoids direct metal-to-metal contact and thus increases wear resistance, was created at the abraded surface and at high temperature, where the reduction of wear rate was due to the development of oxide protective layer. A steady-state wear equation for the contacting surface at high temperature (R = 1/Y √(ln W/2X)) for AA7050 hybrid composites–steel interface was developed. The enhancement in wear resistance was directly proportional to the proportion of ferrous content present on the surface, which was confirmed on the elemental analysis. Pock marks, micropits, craters and cracks were the features observed on the worn surface morphology, whereas delamination and plasticisation were the observed modes of wear mechanism.

A Comparative Evaluation of Flexural and Impact Strength of Polymethyl Methacrylate (PMMA) Reinforced With Graphene and Multi-Walled Carbon Nanotubes: An In Vitro Study.

Background and objective Low flexuralstrength (FS) and impact strength (IS) are major drawbacksin removable prostheses made from polymethyl methacrylate (PMMA). Attempts to enhance the strength and longevity of theseprostheses have been of keen interest among researchers. Nanofillers are new and advanced reinforcements that can chemically modify PMMA. Graphene and multi-walled carbon nanotubes (MWCNTs) were used in this study to evaluate FS and IS when added to polymer and monomer individually. Method Four groups were created based on the addition of nanofillers: no nanofillers - control; 0.5% by weight of graphene; 0.5% by weight of MWCNT; and 0.25% by weight of both. These groups were further subdivided into two according to the nanofiller being added to polymer and monomer each. The samples were then subjected to a 3-point bending test to assess FS, and an Izod impact tester was used to test IS. Results Decreased FS and FS were seen in all groups with the addition of nanofillers in the polymer (p<0.001). With the addition of nanofillers in monomer, increased FS and IS were seen in groups with MWCNTs whereas a decrease was seen with the addition of graphene (p<0.001). Conclusion Nanofillers should be added to the monomer of heat-cure PMMA instead of polymer; 0.5% by weight of MWCNT has shown the highest FS and IS when added to the monomer.

Multi-objective optimization of mechanical and microstructural characteristics in a stir casting process of MWCNTs/Al6082 composites using neutrosophic TOPSIS and GRA

ABSTRACT The objective of this paper is to find optimum process parameters of stir casting process for multi-walled carbon nanotubes (MWCNTs) reinforced Al6082 composites in a multi-objective optimization context. In this work, output parameters include ultimate tensile strength (UTS), hardness, compressive strength (CS), and uniform distribution of MWCNTs. Among these, first three parameters can be measured, and data can be obtained in quantitative terms. However, uniformity of distribution of MWCNT is a qualitative variable, and hence neutrosophic sets are used in this work. Each of the four input process parameters, such as fraction weight of MWCNTs, stirring speed, furnace temperature, and stirring time, are taken at three levels each, and experiments are designed using Taguchi L27 array. Information entropy method is used to compute the weights of output parameters. TOPSIS method is used to normalize the quantitative data, and neutrosophic TOPSIS is applied for normalizing the data related to uniformity. It is found that MWCNT’s percentage of 0.9, speed of 450 rpm, temperature of 800°C, and time of 10 minutes, yield best output parameters. Neutrosophic gray relational analysis is also used to find optimum solution for above case, and the optimum values obtained from both methods are compared.

MWCNT Filled Banana-Rice Husk Epoxy Hybrid Natural Fiber Polymer Composites

Natural fiber composites are prepared by combining two varying fiber/filler contents with a single matrix material. Hybrid polymer composite material made with synthetic agents (Thermosetting polymer) and natural fiber/filler contents. The current study focuses on hybrid polymer composite Multi Walled Carbon nanotubes (MWCNT)-filled Banana fiber/Rice husk filler-reinforced composites that have been assessed for mechanical responses. The banana fiber mat has been in the constant piling mode and altering the MWCNT and rice husk percentage in volume. Vacuum lay-up technique was used to construct the hybrid polymer composite and MWCNT was included with the help of ultrasonic probe sonicator instrument. Mechanical testing is performed accordance to the ASTM standards. The integration of MWCNT, as well as the constant piling order of banana fiber layers, has a stronger impact on mechanical properties. The three samples are prepared at the extremities 5% Banana fiber mat uniform loading and rice husk proportions are 10%, and 15% along with MWCNT filler (0.5% and 1%) for BRME2 and BRME3. The exhibited mechanical testing of the hybrid polymer composite to identify the conventional enhancement of hardness, tensile, impact, flexural, and compressive properties. Scanning Electron Microscope (SEM) is used to examine the fractograph of the tensile sample prepared with BRME3. BRME2 polymer composite with 1% weight of MWCNT was identified higher mechanical properties compare to BRME3 and BRME1 (Tensile, Flexural Strength, and Shore-D Hardness: 46.5 MPa, 59.7 MPa, and 88.5). Furthermore, the impact strength of BRME3 was significantly higher than BRME2 and BRME1.

(Digital Presentation) Evaluating the Performance of Multi-Walled Carbon Nanotube Composite Microporous Layers Deposited on Carbon Felt Gas Diffusion Layers

Electrochemical energy storage devices (EESDs) such as metal-air batteries (MABs) and alkaline electrolyte membrane fuel cells (AEMFCs) have begun to gain vast amounts of attention due to their high theoretical energy densities and open-circuit voltage values. Although these devices present promising aspects for the environment and sustainability, they suffer from the slow reaction kinetics and degradation effects that occur at the catalyst layer interface of the air electrode. Typically, these effects are due to the accumulation of molecular species such as water or oxygen at catalyst active sites because of poor electrode hydrophobicity and fluid management. Herein, we perform experimentation to mitigate these effects by implementing mixed carbon composite microporous layers onto porous carbon felt based air electrodes. This adaptation of the air cathode was predominantly based on the aforementioned downfalls and the lack of availability of commercial carbon felts that have adequate wet proofing and conductivity like some of the related carbon paper gas diffusion layers. Microporous layers (MPLs) enhance electrical conductivity, surface area, and adhesion at the catalyst layer and gas diffusion layer interface. These layers typically consist of a hydrophobic polymer such as polytetrafluoroethylene (PTFE) and a conductive carbon black substrate such as Ketjen Black 600JD (KJB). The incorporation of multi-walled carbon nanotube (MWCNT) and carbon black composites into the structure of the MPLs drastically decreases ohmic polarization with minimal increases in specific resistance. The electrical resistance of the synthesized carbon substrate decreases at high rates of MWCNT dispersion, which corresponds directly to a low MWCNT weight percentage within the composite. The MPL increases the mass transport through the electrode by mitigating flooding effects that typically occur within the pores near the surface of the catalyst layer, ultimately aiding in charge transfer between the gas diffusion layer and catalyst active sites. Preliminary data from AEMFC symmetric cell tests suggests that a microporous layer consisting of a 10 wt.% MWCNT/KJB (m/m) substrate is the optimal loading of carbon nanotubes and leads to better cell performance. There is an increase in current density of 60 mA/cm2 compared to an air electrode with no MPL within the ohmic region of the polarization curve corresponding to approximately 0.7 V, while only an increase of 18 mA/cm2 is seen for an MPL consisting of a 30 wt.% MWCNT/KJB (m/m) carbon substrate. The increase of charge transfer by the 10 wt.% synthesized carbon substrate MPL was attributed to the ability of the nanotubes at high rates of dispersion to act as molecular wires within the electrode. Additionally, zinc-air battery tests using the optimally configured air electrode, determined from previous experiments, show that the current density at an operating voltage of 1.1 V was increased by 2.3 times that of an electrode without an MPL using the same catalyst material and loading. Significantly, this research will lead to a better understanding of optimization of the air electrode used within electrochemical devices and how to eliminate some of the adverse effects associated with it. Figure 1

Influence of multiwalled carbon nanotube on progressive damage of epoxy/carbon fiber reinforced structural composite

AbstractThe present work aims to demonstrate the effect of multiwalled carbon nanotube (MWCNT) on mechanical behavior and damage of woven carbon fiber/epoxy composites through experimental characterizations and multi‐scale modeling. Tensile tests were conducted for MWCNT/epoxy nanocomposites, and carbon nanotube (CNT) reinforced laminated open hole composites with different MWCNT weight ratios. The tensile modulus in CNT/epoxy nanocomposite was enhanced by 15.0%, 37.86%, and 22.86% for MWCNT reinforcement of 0.5%, 1.0%, and 1.5% wt, respectively. The corresponding improvement of tensile modulus for woven composites was 3.45%, 10.25%, and 1.53%; whereas tensile strength was increased by 19.76%, 25.78%, and 6.70%. The enhancement of tensile modulus and strength was less for 1.5% wt MWCNT laminates due to the formation of MWCNT agglomeration. The effective elastic isotropic/orthotropic properties for nanocomposite/woven composite were estimated through Mori‐Tanaka approach and numerical homogenization. The finite element simulations were performed with Hashin's damage model and extended finite element method‐based crack growth study. The delaminations between layers have been demonstrated through cohesive zone modeling. Damage propagation, interface delamination, and fiber/matrix failure were demonstrated by numerical simulations in line with scanning electron microscope observations.

Fracture and energetic strength scaling of epoxy-resins toughened with multi-walled carbon nanotubes

The paper studies the toughening effect of multi-walled carbon nanotubes (MWCNTs) as nanofiller on epoxy resins. We use the size-effect testing methodology to prepare geometrically similar epoxy specimens with varying MWCNT weight fractions. We tested 72 single-edge notched samples and 72 unnotched samples in tensile loading. The addition of MWCNTs resulted in a non-negligible fracture process zone (FPZ). A size-dependent strength is observed and is modeled using type-II energetic scaling law. The mode-I fracture toughness and the FPZ size increased with the MWCNT content, peaked at optimum weight fraction, and then decreased at higher weight fraction. Fractography showed the growth of nanoclusters with an increase in the MWCNT content. We speculate this reduction in the fracture toughness at higher weight fractions is due to failure occurring in the nanoclusters instead of the nanofiller-reinforced matrix.

Flexible Electromagnetic Shielding Material Using Multi-Walled Carbon Nanotube Coated Cotton Fabric

The present work focuses on the development of cotton fabric with multi-walled carbon nanotube coating (CMC) through a dip and dry process. The influence of multi-walled carbon nanotubes (MWCNTs) concentration on transmission, reflection, and absorption properties, which leads to an estimation of electromagnetic interference (EMI) shielding, was also studied. The merits of MWCNTs coating on the cotton fabric were evaluated using field-emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and surface resistivity. The Fourier transform infrared (FTIR) spectroscopy result supports the bonding between MWCNTs and cotton fabric. The significant increase of 98.9&#x0025; of EMI shielding for the highest MWCNTs weight percentage (22.23 wt&#x0025;) was attributed due to the well-interconnected network of MWCNTs. The shielding mechanism in the high wt&#x0025; MWCNTs samples is dominated by both reflection and absorption properties.

Evaluation of the effect of MWCNT amount and dispersion on bending fatigue properties of non-crimp CFRP composites

Multi-walled carbon nanotubes (MWCNTs) have many unique features that improve composite material properties, including a large surface area, thermal and chemical stability, and thermal and electrical conductivity. Our study aimed to examine the influence of MWCNT weight percentage on the fatigue characteristics of a polymer matrix composite strengthened with carbon fiber in fabric form. This study aimed to explore the additional properties and functions of these MWCNTs. For the experiments, MWCNTs were prepared by mixing them in solution with epoxy in three different weight percentages (0.5 %, 1.0%, and 1.5%) using a surfactant, and at 0.5 wt% without a surfactant. The prepared solutions were injected into four-axis non-crimp carbon fiber fabric plates via the vacuity mixture method and then cured for 48 h to produce nanocomposite plates. Using five types of composites, fatigue tests were carried out at six different amplitudes and a fixed frequency. Fatigue test specimens were subjected to detailed SEM analysis of their fatigue fracture surfaces. The investigational results revealed that the 0.5 wt% MWCNT epoxy solution had been homogeneously dispersed and exhibited the highest absorbance spectrum. The 0.5 wt% MWCNT specimen achieved the highest value in the fatigue life experiments. In addition, electron microscopy studies of the fracture surfaces of the test specimens determined that individual COOH-MWCNTs interrelated with the fibers and formed a bridge between fiber and matrix, whereas agglomerations caused weak bonding between the reinforcement fibers and matrix, making the material more brittle.

Theoretical and experimental investigation of MWCNT dispersion effect on the elastic modulus of flexible PDMS/MWCNT nanocomposites

Abstract In this article, Young’s modulus of a flexible piezoresistive nanocomposite made of a certain amount of multiwalled carbon nanotube (MWCNT) contents dispersed in polydimethylsiloxane (PDMS) has been investigated using theoretical and experimental approaches. The PDMS/MWCNT nanocomposites with the governing factor of MWCNT weight fraction (e.g., 0.1, 0.25, and 0.5 wt%) were synthesized by the solution casting fabrication method. The nanocomposite samples were subjected to a standard compression test to measure their elastic modulus using Instron Universal testing machine under force control displacement mode. Due to the costs and limitations of experimental tests, theoretical predictions on the elasticity modulus of such flexible nanocomposites have also been performed using Eshelby–Mori–Tanaka (EMT) and Halpin–Tsai (HT) approaches. The theoretical results showed that HT’s approach at lower MWCNT contents and EMT’s approach at higher MWCNT contents have a better agreement to experimental results in predicting the elastic modulus of PDMS/MWCNT nanocomposites. The experimental results indicated that the inclusion of MWCNT in the PDMS matrix resulted in a noticeable improvement in Young’s modulus of PDMS/MWCNT nanocomposite at small values of MWCNT contents (up to w f = 0.25%); however, exceeding this nanofiller content did not elevate Young’s modulus due to the emergence of MWCNT agglomerations in the nanocomposite structure.

Concentration dependent debundling and single tube dispersions of pristine multiwalled carbon nanotubes functionalized with double tail phospholipids

Multiwalled carbon nanotubes (MWNTs) exist as aggregates of highly entangled tubes due to large aspect ratios and strong Van der Waals interactions among them in their native states. In order to render them suitable for any application, MWNTs need to be separated and dispersed uniformly in a solvent preferably as individual tubes. In the present work, it is demonstrated that a double tail lipid such as 1, 2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) is capable of dispersing MWNTs in ethanol. Ultra-stable suspensions were obtained by optimizing two key parameters: DPPE to MWNT weight ratio (ε) and MWNT concentration (c). Stability of the suspensions increased with the increasing ε value up to an optimum point (ε = 1.8) and then decreased drastically beyond that. CNT dispersions with ε = 1.8 were extremely stable (with a Zeta potential of 108.26 ± 2.15 mV) and could be retained in suspended form up to 3 months. Effect of MWNT concentration on disaggregation was very significant and stable suspensions could be formed for MWNT concentrations only below 0.14 mg ml−1. Above this concentration, no stable dispersions could be obtained even with ε = 1.8. Compression isotherms of Langmuir monolayers of the DPPE functionalized MWNTs spread at the air water interface were highly repeatable, suggesting that the MWNTs in dispersion were present as separate tubes coated with phospholipids. SEM micrographs of the Langmuir–Blodgett (LB) films, deposited at high surface pressures on silicon wafers, show that MWNTs remain as single nanotubes with no signs of reaggregation. TEM micrographs of MWNT suspensions indicated random adsorption of DPPE on MWNTs. Our work makes it possible to explore potential applications of LB films of MWNTs (stabilized by DPPE) in the development of conducting thin films for sensor applications or as supports to immobilize catalysts for heterogenous reactions.

Chemically Coupled Multiwall Carbon Nanotubes with Leaf-Like Nanostructures of NiO for Sensitive and Selective Determination of Uric Acid

The chemical coupling of NiO nanostructures with thermally treated multiwall carbon nanotubes (MWCNTs) is not reported as it provides an enhanced dispersion of composite material in water. The dispersion of MWCNTs has been considered a big challenge. For this purpose, we first thermally treated MWCNTs at 1000°C in air for 30 min. Then, thermally treated MWCNTs were chemically coupled with NiO nanostructures by a hydrothermal method. The material characterization in terms of structure, morphology, and composition is well studied by different analytical techniques. The NiO composite (sample 2) with highest weight of MWCNTs had a leaf-like morphology and it exhibits a cubic phase of NiO. Cyclic voltammetry (CV) was used to study the electrochemical activity of prepared composite material towards the oxidation of uric acid in the phosphate buffer solution of pH 7.0. Sample 2 showed a well-behaved anodic peak with enhanced peak current and exhibited a linear range from 0.01 mM to 2.5 mM for uric acid with a low limit of detection 0.001mM. Sample 2 was found to be very selective under the environment of competing interferents such as urea, glucose, lactic acid and ethanol. This sample exhibits significant stability, thus it is a potential protocol for the monitoring of uric acid from real samples. This study provides a low-cost platform for the fabrication of efficient materials for various applications such as batteries, fuel cells and water splitting.

Mechanical properties improvement of bi-directional functionally graded laminated MWCNT reinforced composite beams using an integrated tailoring–optimization approach

Many leading technologies are introduced to enhance mechanical structures’ capabilities. Promising materials are also explored, such as nanocomposites, functionally graded, and smart materials. This research discusses one of these encouraging proposals named Bi-Directional Functionally Graded Multi-Walled Carbon Nanotubes (MWCNT) Reinforced Composite (BDFG-CNTRC). Therefore, a simple cantilever beam consists of ten MWCNT/polymer layers is proposed. Each layer has its own different MWCNT weight ratio and axially grading to conduct Bi-directional property. It is assumed to contain 1% of MWCNT weight as a fixed reinforcement ratio. This assumption preserves beam constant weight. Consequently, a finite element model based on previous studies is modified to cope with the presented beam material and geometric properties. The obtained results are compared to published numerical and experimental optimized findings and have shown high accuracy. After that, a new tailoring–optimization approach is introduced and applied for the chosen beam. Significant improvements are obtained in beam mechanical properties and response. It is found that effective elastic modulus remarkably enhances by 114.93%. Fundamental natural frequency increases by 55.08%. Moreover, beam tip deflection reduces by 53.47%.

Production of Multi-Walled Carbon Nanotube and Graphene Doped Thermoplastic Polyurethane Fiber and Investigation of Mechanical Properties

Nowadays nanofibers are used in many areas. Nanofibers produced by electrospinning are required to be porous, large surface area, lightweight and cost effective. In addition to being lightweight, nanofibers must also have sufficient strength to withstand the applied forces. In this study; 3 different fibers were produced. Undoped TPU fiber, 1% by weight of multi-walled carbon nanotubes (MWCNTs) doped TPU fiber and 1% by weight of graphene doped TPU fiber were obtained seperatally by electrospin method. The morphological structures of the produced nanofibers were determined by SEM. Tensile test was performed to determine the mechanical strength of the nanofibers produced and compared with each other. Cardboard plate mouthpieces are attached to the beginning and end of the samples prepared in accordance with the standards thus the jaws can hold the samples. According the results; the maximum average tensile value of MWCNTs doped TPU nano fibers is 7.85 MPa. This value was found to be higher than pure and graphene doped TPU nano fibers. It has been concluded that MWCNTs additive has a strength increasing effect on TPU nano fibers.

Analysis of mechanical and thermal properties of epoxy multiwalled carbon nanocomposites

The main objective of this study was to investigate the efficiency of the sonication process and of multi-walled carbon nanotubes (MWCNTs) content on the mechanical and thermal properties of an epoxy matrix. Three different sonication powers (25, 50 and 75 W) were used to disperse the MWCNTs (0.2%, 0.4% and 0.6% wt.) in the epoxy matrix. Tensile tests were performed to determine the mechanical properties of the nanocomposites, while the thermal properties were determined by the thermogravimetric analysis (TGA) and the Differential Exploratory Calorimetry (DSC). Finally, a SEM analysis was used to investigate the morphology of the tensile fractured surface and the dispersion of the nanotubes in the polymeric matrix, since the quality of dispersion influences the mechanical and thermal properties of nanocomposites. It was found that the addition of carbon nanotubes to the epoxy matrix and the parameters of the sonication process affect the mechanical and thermal properties of nanocomposites. An increase of approx. 14% in tensile strength and 15% of Young’s modulus, when compared to the pure epoxy matrix was found for 75 W sonication power output and 0.6% MWCNTs weight percentage. The thermal analysis indicated that the presence of MWCNTs increased the Tonset of the nanocomposites when compared to pure epoxy resin. Finally, increasing the sonication power output leads to higher Tg of the nanocomposites studied here.

Toxicity effects of multi-walled carbon nanotubes (MWCNTs) nanomaterial on the common carp (Cyprinus carpio L. 1758) in laboratory conditions

Over the past decade, the usages of carbon nanotubes in various industries have been increased. Multi-walled carbon nanotubes (MWCNTs) are special form of carbon nanotubes which are used as nano-absorbents for various purposes of different industries due to their high surface to volume ratio. In aquatic environments these active nano-agents can easily absorb and accumulate in animal cells and tissues due to their tiny sizes and induce toxicity effects on bio-organisms mainly via pro-oxidants production. The present study assayed MWCNTs toxicity effects on anti-oxidative enzymes activities, serum hormonal and biochemical stress biomarkers, hematology parameters, histopathology and growth performance of the common carp Cyprinus carpio. Experiment was conducted in five treatments including 0 (control), 5, 10, 15, 20 mg/l MWCNTs in triplicate and each of the experimental tanks consisted of a 400-l recirculating system, stocked with, 20 fish (12 ± 2 g) for 28 days. The results indicated that by increasing the concentrations of the MWCNTs weight gain, specific growth rate and survival rate parameters were decreased. The findings showed that cortisol secretion, blood glucose level and anti-oxidative enzymes activities were increased with the increase of MWCNTs concentrations in the treatments. Histopathology results depicted that 15 and 20 mg/l MWCNTs caused hyperplasia, telangiectasia, apoptosis, and necrosis damages in gills and also, apoptosis, sinusoidal spaces, fibrosis, hepatocyte degeneration and necrosis in the liver of C. carpio. Despite these findings, further researches on effects of nanomaterials on aquatic organisms and ecosystems are essential to protect these environments against the newly found nanomaterials hazards.

Effects of Multi-walled Carbon Nanotubes on the Microwave Absorbing Properties of Magnetorheological Elastomers

The microwave absorbing properties of carbonyl iron particles (CIPs) based magnetoheological elastomer (MRE) filled with multi-walled carbon nanotubes (MWCNTs) were examined. Absorbents including the CIPs and MWCNTs were mixed and added to the silicone rubber (SR) matrix for further compression molding and vulcanization. The complex permittivity and complex permeability were measured over a frequency range of 2-18GHz. As the MWCNT weight percentage increased, the reflection loss (RL) of the MRE composites changed significantly, which is attributed to the impedance mismatch. The MRE composites containing 28 wt% CIPs and 0.1 wt% MWCNTs with a thickness of 3 mm display dual resonance peaks with a maximum RL of -53 dB and the effective frequency bandwidth (RL<-10dB) reaches 7.7 GHz. This suggests that the MRE composites could serve as a potential candidate for absorbing incident microwave with excellent flexibility.