Percentage Of Multi-walled Carbon Nanotubes Research Articles

Tribological effects of carbon nanotubes on magnesium alloy AZ31 and analyzing aging effects on CNTs/AZ31 composites fabricated by stir casting process

Abstract The tribological behavior of AZ31 Mg alloy reinforced with multiwall carbon nanotubes (MWCNTs) was studied through experiments on a ring-on-block wear testing apparatus against 45C steel. The composites were successfully fabricated using stir-casting processing with different percentages of MWCNTs and then age hardened for 10 h. The effect of the various concentrations of MWCNTs on the microstructures, tribological properties, and wear mechanisms of the composites were systematically examined by scanning electron microscopy (SEM). With increasing percentage content of MWCNTs, the wear rate and the coefficient of friction decreased, which is attributed to the microhardness and self-lubricating properties of the MWCNTs. The microstructure characterization results established different mechanisms—specifically, abrasion, oxidation, and delamination—and very small plastic deformation.

Impact and bending analysis of composite scarf adhesive joints modified with MWCNTs at room and hot temperatures

Scarf adhesive joints (SAJs) have attracted an increasing attention in joining/repairing of carbon-fiber reinforced epoxy (CFRE) composite structures due to their zero eccentricity, which provides better aerodynamic surfaces. This study evaluated for the first time, the performance of SAJs in CFRE composites under thermo-mechanical impact loads. The adhesive was modified with optimum percentage of multi-walled carbon nanotubes (CNTs). The impact tests were performed at room temperature of +25°C, +50°C and +75°C. The residual flexural properties of the unfailed impacted joints were measured using three-point bending test. Results from impact tests at temperature of 25°C, 50°C and 75°C showed improvement in the impact bending stiffness of the modified SAJs with CNTs by 8.3%, 7.4% and 11.8% and maximum contact force by 15.6%, 21.3% and 18.9%, respectively. The energy at failure of the CNT-SAJs was increased by 15.2% and 16.4% respectively at temperatures of 25°C and 50°C. At test temperature of 75°C the SAJs have hysteresis load-displacement behavior and energy-time curve with rebound energy of 35% and absorbed (damage) energy of 65%. The residual flexural strength of the modified and unmodified SAJs is 98.2% and 86.1% respectively, while their residual moduli have remarkable decrease to 71.7% and 81.3%.

Experimental analysis of composite scarf adhesive joints modified with multiwalled carbon nanotubes under bending and thermomechanical impact loads

Scarf adhesive joints have attracted an increasing attention in joining/repairing of carbon fiber reinforced epoxy composite structures due to their zero eccentricity, which provides lower stress distribution across the adhesive layer and better aerodynamic surfaces compared to other bonded joints. The main objective of this study is to evaluate the performance of the scarf adhesive joints in carbon fiber reinforced epoxy composites under thermomechanical impact loads, which is very important for the aerospace and automotive industries. The adhesive was modified with optimum percentage of multiwalled carbon nanotubes. The impact tests were performed at 25 ℃, 50 ℃, and 75 ℃. The residual flexural properties of the unfailed impacted joints were measured using three-point bending test. Results from impact tests at 25 ℃, 50 ℃, and 75 ℃ showed improvement in the impact bending stiffness of the modified scarf adhesive joints by 8.3%, 7.4%, and 11.8% and maximum contact force by 15.6%, 21.3%, and 18.9%, respectively. The energy at failure of the modified scarf adhesive joints with multiwalled carbon nanotubes was improved by 15.2% and 16.4% respectively at 25 ℃ and 50 ℃. At test temperature of 75 ℃, the scarf adhesive joints have hysteresis load–displacement behavior and energy–time curve with rebound energy of 35% and absorbed (damage) energy of 65%. The residual flexural strength of the modified and unmodified scarf adhesive joints is 98.2% and 86.1% respectively, while their residual moduli have remarkable decrease to 71.7% and 81.3%.

Vibration analysis of multiwalled carbon nanotube-reinforced composite shell: An experimental study

In the present study, the vibration analysis of a multiwalled carbon nanotubes (MWCNTs)-reinforced composite shell is performed to investigate the enhancement in natural frequencies and damping of polymer composite structure. Initially, the material characterization of MWCNT-reinforced polymer resin was performed using scanning electron microscope, transmission electron microscope, and energy-dispersive X-ray analysis to identify the bonding behavior of MWCNT with resin, structure of MWCNTs, structural integrity, and chemical purity of MWCNT. The mechanical characterization of MWCNT-reinforced polymer composites was performed using universal testing machine to identify the enhancement in tensile properties of the composites with MWCNT reinforcement. Laminated composite shell samples were then fabricated with the different weight fraction of the MWCNT to study the effect of weight percentage of MWCNT on the composite shells on enhancement of natural frequencies and damping. Significant increase in tensile characteristics of the composites could also be identified with the addition of MWCNT in polymer composites. It was also observed that the fundamental natural frequency and damping factor of the hybrid composite could be increased by 20% and 7%, respectively, with 1 wt% reinforcement of MWCNT in the polymer resin.

Investigation of Tensile Properties of Carbon/Epoxy Composite Joints with and without Carbon Nano-Tubes

The intent of this project is to determine the tensile strength of CFRP lap joint with and without introduction of multiwall carbon nano tubes (MWCNT). Specimens with lap joint were prepared by Adhesive bonding. The dimensions of the specimens were kept according to the ASTM standard D-5868. An experimental work along with FEA analysis was undertaken to identify the ultimate tensile strength and modes of failure in two different categories of adhesively bonded specimen, firstly with inclusion of different percentages of MWCNT and secondly without inclusion of MWCNT. MWCNT of 0.1% and 0.3% by weight was added to the adhesive used in creating the joint. The adhesively bonded specimens with inclusion of MWCNT showed better load bearing capacity, the highest being 86% for 0.3% MWCNT. An increment of 27% was observed in the tensile strength with the increase in percentage of MWCNT. Further the FEA analysis was carried out which proved the experimental results are well within the error range of 1%.

Effect of MWCNT content on thermal and shape memory properties of epoxy nanocomposites as material for morphing wing skin

In the present study, a shape memory epoxy polymer (SMEP) system was prepared from commercially available EPON 826 and NGDE, and then, 0.5%, 1.0% and 1.5% mass percentage of multi-walled carbon nanotubes (MWCNTs) were incorporated into it so as to prepare nanocomposites. The inclusion of the nanofiller into the SMEP system was expected to enhance its properties. Then, experimental analyses were conducted to study the effect of incorporating different amounts of MWCNTs on the thermal properties of the obtained nanocomposites, namely dynamic mechanical analysis, thermogravimetric analysis (TGA) and shape memory cyclic testing. It was found that the increasing content of MWCNTs in the SMEP system decreased the glass transition temperature of the developed nanocomposites (SMEPCs). TGA results indicated that the incorporation of MWCNTs into the SMEP decreased its thermal stability. The authors explained these results by the lack of interaction between the MWCNTs and the epoxy matrix. In consideration of the use of the SMEP for morphing applications, the increment in MWCNT content was found to improve the shape recovery properties of the SMEP. Thus, the study demonstrates that the incorporation of a MWCNT nanofiller can help enhance the properties of the SMEP system and overcome its limitations, revealing the high potential of the developed shape memory composite materials to be used for various industrial applications.

Multiscale material modelling and analysis of carbon fiber/MWCNT/epoxy composites to predict effective elastic constants

Abstract In the current work, the effect of weight percentage and orientation of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties of unidirectional (UD) carbon fiber (CF)/MWCNT/epoxy composites was studied by using multiscale material modelling and finite element analysis (FEA). Nanoscale representative elementary volume (RVE) consisting of MWCNTs and microscale RVE consisting of carbon fibers were generated using DIGIMAT FE Software. The equivalent elastic properties obtained from MWCNT/epoxy composites were used to estimate effective elastic constants of UD carbon fiber/MWCNT/epoxy composites. The weight percentage of MWCNTs was varied 0%–5%, while MWCNTs were orientated at 0°, 30°, 45°, 60° and 90°. It was found that the E1, E2, G12, υ12 and υ23 increased by 1.79%, 6.14%, 2.83%, 8.8% and 5% at 5 wt% addition of MWCNTs respectively. It was also found that except transverse young's modulus (E2) all other elastic constants decreased by increasing the orientations and at 90° the transverse Young's modulus (E2) increased by 16.57% compared to 0° orientation at 1 wt% addition of MWCNTs. The multiscale FE analysis results were compared by multiscale micromechanics model.

Influence of sprayed multi-walled carbon nanotubes on mode I and mode II interlaminar fracture toughness of carbon fiber/epoxy composites

Unidirectional carbon fiber/epoxy prepregs were sprayed over their surfaces with different multi-walled carbon nanotubes (MWCNTs) concentrations in order to evaluate their effect on interlaminar fracture toughness of composite laminates under modes I and II loading and the influence in fracture mechanisms. To this aim, determination of the mode I and mode II interlaminar fracture toughness of composite laminates reinforced with sprayed MWCNTs were experimentally investigated using double cantilever beam and end notched flexure tests. Composite laminates without MWCNTs were also fabricated as a reference material. MWCNT characterization using Fourier Transform Infrared and Raman spectroscopy was also carried out in order to evaluate their functional groups and structural defects. The results show that the mode I and mode II interlaminar fracture toughness of the composite laminates can be moderately increased as MWCNT concentrations varying from 0.05 to 0.2 wt.%. Scanning electron microscope images of fracture surfaces provide evidence that the MWCNTs bridged and pulled out at the interface of composite laminates. It was also demonstrated that the optimum weight percentage of MWCNTs needed to improve the mode I and mode II interlaminar fracture toughness was 0.05%, due to the fact that higher concentrations promote the agglomeration of MWCNTs weakening the laminate interfaces.

Voltammetric monitoring of linezolid, meropenem and theophylline in plasma

Treatment of healthcare associated Pneumonia (HCAP) caused by Methicillin-resistant Staphylococcus aureus (MRSA) requires therapeutic protocols formed of linezolid (LIN) either alone or in combination with meropenem (MERO) and theophylline (THEO). The inter-individual pharmacokinetic variations require the development of reliable therapeutic drug monitoring (TDM) tools especially in immunocompromised patients. A sensitive square wave voltammetric sensor using multiwalled carbon nanotubes (MWCNTs) modified carbon paste electrode in Britton-Robinson buffer was developed and validated. Experimental parameters such as pH, percentage of MWCNTs, and pre-concentration time were optimized. The sensor was employed at pH 11.0 for the determination of LIN in plasma within a concentration range of 2.5 × 10−8 - 8.0 × 10−6 mol L−1without interference from co-administered medications. On the other hand, simultaneous monitoring of LIN, MERO and THEO in plasma was feasible at pH 3.0 over concentration ranges of 4.0 × 10−7- 9.0 × 10−5, 8.0 × 10−7- 9.0 × 10−5 and 8.0 × 10−7 - 9.0 × 10−5 mol L−1, respectively. The performance of the proposed sensor was validated and the applicability for TDM has been demonstrated in plasma of healthy volunteers.

Fabrication and Characterization of AA7075 Metal Matrix Composite Reinforced With MWCNT

Many engineering applications requires components with light weight property as well as good mechanical properties, this requirement can be served by the Metal Matrix Composites (MMCs) of Aluminum due to its outstanding performance. In the current research work an attempt has been made to fabricate the Aluminum metal matrix composite by liquid route i.e. stir casting. Aluminum Alloy (AA) 7075 is used as a matrix which is reinforced with Multi Walled Carbon Nanotubes (MWCNT) with varying percentage (0wt%, 0.25wt%, 0.5wt%, 0.75wt%). Experiments were carried out to analyze microstructure, micro hardness and the other mechanical properties like tensile strength and Impact strength. Also the samples were studied under Optical microscope and Scanning Electron Microscope (SEM) to investigate the dispersion of MWCNT in AA7075. Microscopic study of 0.25wt%, 0.5wt% & 0.75wt% samples shows a good dispersion of MWCNT into AA7075. Hardness of material increases by 6%, 12% and 25% for 0.25wt%, 0.5wt%, 0.75wt% respectively thus hardness increase with increase of MWCNT percentage. Ultimate tensile strength of material increases with increase in percentage of MWCNT and%Elongation reduces. Impact strength of material increases with increase in percentage of MWCNT.

Effects of multi-wall carbon nanotubes on structural and mechanical properties of poly(3-hydroxybutyrate)/chitosan electrospun scaffolds for cartilage tissue engineering

Poly(3-hydroxybutyrate) (PHB)/chitosan electrospun scaffold was recently prepared for cartilage tissue engineering purpose. The drawback of this scaffold was its low mechanical properties. This study was carried out to see if addition of multi-wall carbon nanotubes (MWNTs) to PHB/chitosan polymeric blend can show better mechanical and structural properties. To do this, three different amounts of MWNTs (0.5, 0.75 and 1 wt%) were added to PHB/chitosan solution. Then, the prepared solution was electrospun. The fibre’s diameter and uniformity were assessed by SEM. The solution components entity authenticity was approved by FTIR. The porosity assessment was illustrated by a porous structure with 81–83% porosity. Water contact angle (WCA) test showed the decrease in contact angle with the increase in MWNTs. Mechanical property results showed the strength of about 4–10 MPa for composites with different percentages of MWNTs, while PHB/chitosan showed the strength of 3 MPa. Actually, the mechanical properties of composite showed higher values when compared to polymeric blend scaffold. All the results reveal that the addition of 1 wt% of MWNTs to the polymeric solution is the most optimal percentage whose values are close to cartilage properties.

Thermally stable superhydrophobic polymethylhydrosiloxane nanohybrids with liquid marble-like structure

We prepared novel hybrid materials by in situ self-hydroxylation and condensation of polymethylsiloxane (PMHS) with multi-walled carbon nanotubes (MWCNTs). The hybrid material showed superhydrophobic and non-stick properties, mesoporous structure, and liquid marble-like non-stick water droplet behavior. Moreover, we found that the in situ addition of MWCNTs to the PMHS would increase the thermal stability of the hybrid material. Thermal stability of the hybrid is enhanced by increasing the percentage of MWCNTs to the PMHS. The superhydrophobic hybrid powder covered non-stick water droplet showed anti-icing behavior for long time. The hybrids also showed oils sorption behavior and easy reusable property. The obtained results suggest that the thermally stable superhydrophobic hybrid mesoporous materials with anti-icing, oils sorption properties can be easily synthesized and used for various applications.

Fabrication of solid alginate particles containing functionalized MWCNTs using a microfluidic technique

A series of solid alginate particles containing different amounts of functionalized multi-walled carbon nanotubes (MWCNTs) have been successfully prepared by microfluidic technique. The influence of MWCNTs doping on the surface morphology, structure and properties of calcium alginate (CA) particles has been investigated using SEM, FTIR, XRD, TGA and UV-Vis spectra. SEM indicates that the obtained hybrid particles are of good morphological characteristics, and its color changes from yellow to black which proves MWCNTs is successfully dispersed in CA particles. Moreover, the particles surface changes rough from smooth after MWCNTs doping. FTIR results verify the interactions between functional groups of CA and MWCNTs. Besides, the incorporation of MWCNTs to CA particles can efficiently enhance the thermal stability of CA particles at high temperatures, which is ascribed to the better thermal stability of MWCNTs as well as the interactions between MWCNTs and CA particles. The removal efficiency of CA particles doped with a lower percentage of MWCNTs (0.06 wt. %) for methylene blue is 96.38%, which is much higher than that of pure CA particles (61.21 %).

Experimental Investigation on Cement Mortar Blended with HNC and CNTs’ [Hallyosite nanoclay and Carbon Nanotubes]-Taguchi’s Approach

This research focuses on the results of experimental investigation of the compressive strength of CementMortar cubes blended with Multi walled Carbon Nanotubes (MWCNTs) and Hallyosite Nanoclay (HNC’s).The percentage of MWCNTs and HNC’s was fixed to 0.5%, 0.75% and 1% by weight of cement. In thisresearch, experiments were conducted on the 3 different grades of mortar( MM-3,MM-5,MM-7.5 ) and 3different size of cube specimens (25x25x25, 50x50x50 and 75x75x75), out of which 50mm cube is the sizeas per IS 2250-1981 and remaining two (25 mm and 75mm) are trial mixes. Casted specimens were testedon 7th, 14th and 28th day of curing. Compressive strengths obtained from these experiments are analyzedthrough Taguchi’s method of Optimization and ANOVA (Analysis of Variance) with the help of Commercialsoftware MINITAB-16. Statistical Analysis is conducted to find the interaction of the factors and their effecton strength of mortar. Regression analyses are employed to obtain the optimal process parameters. Out of0.5%, 0.75%and 1% of HNC added to the conventional cement mortar 0.75% resulted in OptimumCompressive Strength for 50mm size of cube specimen as per experiments and Regression Analysis. Also, itis observed that when MWCNTs are mixed, compressive strength increases as percentage increases

A nanostructured suitable platform based on multi wall carbon nanotubes and graphene nano sheets composite for determination of mefenamic acid

A mefenamic acid sensor was prepared by the modification of a glassy carbon electrode (GCE) with graphene nano-sheets (Gr) and multi wall carbon nanotubes (MWCNT). The designed sensor (MWCNT/Gr/GCE) indicated an electrocatalytic behaviour when applied for mefenamic acid (MFA) oxidation due to good conductivity, low electron transfer resistance and catalytic effect. The suggested sensor revealed a lower overvoltage and enhanced current compared with bare GCE for the oxidation of MFA. The observations indicated that the oxidation potential of MFA is decreased more than 200 mV using the designed sensor. The percentages of MWCNTs and Gr nano materials, and pH solution were optimized. Under the optimum conditions, some kinetic parameters, such as surface coverage in a 0.5 mM [Fe(CN)6]3-/4- solution was obtained by cyclic voltammetric method. The diffusion coefficient of MFA (D) was calculated to be 2.88?10-6 cm2 s-1 by chronoamperometeric technique. The MWCNT/Gr/GCE sensor exhibited a linear dynamic range for MFA (2? 100 ?M) with a detection limit of 0.66 ?M by differential pulse voltammetry (DPV) technique. This sensor revealed a suitable applicability for determination of MFA in real samples (drug samples and serum solutions).

Facile fabrication of carbon nanotubes/polystyrene composite nanofibers for high-performance electromagnetic interference shielding

Polystyrene (PS) composites with nanofibrous structure consisting of multi-walled carbon nanotubes (MWCNTs) with 0-10 wt.% of nanofiller have been fabricated via electrospinning technique. The surface morphology and thermal properties of the composites were evaluated by scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA). The SEM analysis of the composite nanofibers samples revealed that the average diameter of the nanofibers increases with increasing MWCNTs content. The resultant MWCNTs/PS composite nanofibers diameters were in the range of 391±63 to 586±132 nm. The thermal stability of composites was increased after addition of MWCNTs to PS matrix. The electrical conductivity of the composites with different weight percentage of MWCNTs was investigated at room temperature. Electrical conductivity of MWCNTs/PS composite nanofiber followed percolation theory having a percolation threshold Vc= 0.45 vol% (~0.75 wt. %) and critical exponent q=1.21. The electrical conductivity and thermal properties confirmed the presence of good dispersion and alignment MWCNTs encapsulated within the electrospun nanofibers. The electromagnetic interference (EMI) shielding effectiveness of the MWCNTs/PS composites was examined in the measurement frequency range of 8.2-12.4 GHz (X-band). The total EMI shielding efficiency of MWCNTs/PS composite nanofibers increased up to 32 dB. The EMI shielding results for MWCNTs/PS composite nanofibers showed that absorption loss was the major shielding mechanism and reflection was the secondary mechanism. The present study has shown the possibility of utilizing MWCNTs/PS composite nanofibers as EMI shielding/absorption materials.

Optimization of processing parameters of medium density fiberboard using response surface methodology for multiwalled carbon nanotubes as a nanofiller

In the present work, medium density fiberboard (MDF) panels were produced using multiwalled carbon nanotubes (MWCNT) reinforced urea formaldehyde resin. Response surface methodology was employed to optimize the relationship between the three variables, viz. pressing time, percentage of UF resin and percentage of MWCNT, used in the fabrication of MDF, and the influence of variables on the internal bonding (IB) and modulus of rupture (MOR) was studied. The optimum conditions based on the IB strength were determined as 8.18 % of UF resin, pressing time of 232 s, and MWCNT of 3.5 %. Similarly, the optimized conditions for MOR are also reported in this paper.

Characterization of magnetic and microwave absorption properties of multi-walled carbon nanotubes/Mn-Cu-Zr substituted strontium hexaferrite nanocomposites

The nanocomposites of multi-walled carbon nanotubes (MWCNT)/SrMnxCuxZr2xFe12-4xO19 (x=0.0, 0.2, 0.3, 0.4 and 0.5) were fabricated. The X-ray diffraction patterns (XRD) confirmed the formation of M-type hexaferrites crystal structure. Fourier transform infrared (FTIR) spectroscopy has been used to consider the chemical bonds in the nanocomposites. From field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), the fabrication of the nanocomposites has been confirmed. The vibrating sample magnetometer (VSM) was used to investigate magnetic properties of the nanocomposites. Microwave absorption properties have been investigated by the vector network analyzer. It is found that the nanocomposites with x⿥0.3 and 7% weight percentage of MWCNT possess the wide bandwidth of 6GHz. The nanocomposite with the chemical composition of SrMn0.4Cu0.4Zr0.8Fe10.4O19-MWCNT has the highest reflection loss, and as a result, it is the most appropriate material among these samples to be used as an electromagnetic wave absorber.

Mechanical Properties and Durability of Ultra High Strength Concrete Incorporating Multi-Walled Carbon Nanotubes.

In this work, the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and durability of ultra high strength concrete (UHSC) is reported. First, the MWCNTs were dispersed by a nano sand-mill in the presence of a surfactant in water. The UHSC specimens were prepared with various amounts of MWCNTs, ranging from 0% to 0.15% by weight of cement (bwoc). Results indicated that use of an optimal percentage of MWCNTs (0.05% bwoc) caused a 4.63% increase in compressive strength and a 24.0% decrease in chloride diffusion coefficient of UHSC at 28 days curing. Moreover, the addition of MWCNTs also improved the flexural strength and deformation ability. Furthermore, a field-emission scanning electron microscopy (FE-SEM) was used to observe the dispersion of MWCNTs in the cement matrix and morphology of the hardened cement paste containing MWCNTs. FE-SEM observation revealed that MWCNTs were well dispersed in the matrix and no agglomerate was found and the reinforcing effect of MWCNTs on UHSC was thought to be pulling out and microcrack bridging of MWCNTs, which transferred the load in tension.

Improvement of toughness and shear properties of multiwalled carbon nanotubes/epoxy composites

In this work, Epocast 50‐A1/946 epoxy have been modified with different weight percentages (0.25, 0.5, 0.75, 0.1, 1.25, and 1.5 wt%) of multiwalled carbon nanotubes (MWCNTs). Because of Epocast epoxy was primarily developed for joining and repairing of composite aircraft structural components, the optimum weight percentage of MWCNTs must be determined based on trade‐offs between the optimum tensile, in‐plane shear and toughness properties of the developed MWCNTs‐composites, which is the objective of this study. The effect of MWCNTs on the toughness and in‐plane shear was studied using single‐edge notch tension and Iosipescu shear tests, respectively. The experimental results showed that the composite materials with 0.75 wt% MWCNTs has the highest improvement in the in‐plane shear properties compared to the neat epoxy. While the maximum improvements in the tensile and toughness properties were observed at 0.5 wt% MWCNTs. Eleven models were selected from an extensive literature survey, for predicting the in‐plane shear moduli of the developed MWCNTs‐composites. The modified rule of mixture can effectively predict the in‐plane shear moduli of the composites with MWCNTs up to 0.75 wt%. While the nonlinear behavior of the modified Halpin–Tsai model with exponential shape function is the closest to the experimental results up to 1.5 wt% MWCNTs. POLYM. COMPOS., 39:815–825, 2018. © 2016 Society of Plastics Engineers