Percentage Of Carbon Nanotubes Research Articles

Influence of discontinuities on the fracture behaviour of CNT reinforced composites subjected to thermo-mechanical load using XIGA

This paper is aimed to investigate the fracture behaviour of carbon nanotube (CNT) reinforced composite exposed to the thermo-mechanical environment in the presence of discontinuities using the extended isogeometric analysis (XIGA) method. The study focuses on finding the effects of discontinuities present in a finite plate with a pre-existing crack, on the stress intensity factors (SIFs). The mandatory equivalent mechanical and thermal properties are assessed with the help of various micromechanics models. Two types of CNTs are assumed to be reinforced in the epoxy-matrix: single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT). The CNT reinforced composite is examined for varying volume percentages of CNTs reinforcement. A comparative study is provided to see the influence of mechanical and coupled thermo-mechanical load on SIFs. Adiabatic crack is taken into account for the computational simulation for thermal loading condition. The interaction integral method is used for the extraction of SIFs. The findings of the test reveal that with the rise in the volume percentage of CNTs, the properties such as fracture energy and fracture toughness also rise. Moreover, the fracture of CNT reinforced composites is delayed with the increased content of CNT. The results establish the profound influence of holes on SIFs than the inclusions.

Microstructural and mechanical properties of CNT-reinforced ZrO2-Y2O3 coated boiler tube steel T-91

The main purpose of this study was to fabricate carbon nanotubes (CNTs) reinforced zircon­nium yttrium coatings on boiler tube steel and to investigate the microstructural and mechanical properties of these coatings. Plasma sprayed conventional ZrO2-Y2O3, ZrO2-Y2O3 and 1 wt.% CNT and ZrO2-Y2O3 and 4 wt.% CNT were prepared and deposited successfully on boiler tube steel material T-91 (ASTM SA-213) by plasma thermal spray technology. Microhardness, porosity, XRD (X-ray diffraction), SEM/EDAX (scanning elec­tron microscopy/energy dispersive X-ray spectroscopy), X-ray mapping and cross-sectional analyses were used to analyse the specimens. The hardness of CNT reinforced ZrO2-Y2O3 increased with the increase in the percentage of CNT, whereas the porosity of the composite coatings decreased with the increase in the CNT percentage. The observed increase in hardness may be attributed to the content of CNT in the composite coating. The present research gives important information related to the fabrication and physical characteristics of CNT-reinforced ZrO2-Y2O3 coatings deposited on T-91 boiler tube steel.

Electrospun Carbon Nanotube-Based Scaffolds Exhibit High Conductivity and Cytocompatibility for Tissue Engineering Applications.

Carbon nanotubes (CNTs) are known for their excellent conductive properties. Here, we present two novel methods, “sandwich” (sCNT) and dual deposition (DD CNT), for incorporating CNTs into electrospun polycaprolactone (PCL) and gelatin scaffolds to increase their conductance. Based on CNT percentage, the DD CNT scaffolds contain significantly higher quantities of CNTs than the sCNT scaffolds. The inclusion of CNTs increased the electrical conductance of scaffolds from 0.0 ± 0.00 kS (non-CNT) to 0.54 ± 0.10 kS (sCNT) and 5.22 ± 0.49 kS (DD CNT) when measured parallel to CNT arrays and to 0.25 ± 0.003 kS (sCNT) and 2.85 ± 1.12 (DD CNT) when measured orthogonally to CNT arrays. The inclusion of CNTs increased fiber diameter and pore size, promoting cellular migration into the scaffolds. CNT inclusion also decreased the degradation rate and increased hydrophobicity of scaffolds. Additionally, CNT inclusion increased Young’s modulus and failure load of scaffolds, increasing their mechanical robustness. Murine fibroblasts were maintained on the scaffolds for 30 days, demonstrating high cytocompatibility. The increased conductivity and high cytocompatibility of the CNT-incorporated scaffolds make them appropriate candidates for future use in cardiac and neural tissue engineering.

The Effect of Agglomeration on the Electrical and Mechanical Properties of Polymer Matrix Nanocomposites Reinforced with Carbon Nanotubes.

In this work, we investigated the effect of carbon nanotubes addition and agglomeration formation on the mechanical and electrical properties of CNT–polymer-based nanocomposites. Six specimens with carbon nanotubes (CNTs) fractions of 0%, 0.5%, 1%, 2%, 4% and 5% were manufactured and characterized by dynamic mechanical analysis (DMA) and four-probe method. The stress–strain curves and electrical conductivity properties were obtained. Scanning electron microscopy (SEM) was used to characterize both agglomeration and porosity formation. By employing micromechanics, through representative volume element (RVE), finite element analysis (FEA) and resistor network model (RNM), the Young’s modulus and electrical conductivity values were calculated. The samples’ elastic moduli showed an increment, reaching the maximum value at a CNTs fraction of 2%, thereafter an adverse effect was caused in the high CNT percentage samples. The final electrical conductivity seemed greatly altered with the addition of CNTs, reaching the percolation threshold at 2%. The unavoidable formation of CNT agglomerates appeared to influence the final physical properties. The CNT agglomerates adversely affect the mechanical performance of high-CNT-percentage samples. Conversely, an exponential increment in the electrical conductivity was presented as the agglomerates formed networks allowing the transport of electrons through the tunnelling effect. These phenomena were experimentally and numerically confirmed, showing a good correlation.

Experimental investigation on mechanical behavior of fiber–metal laminates reinforced by hybrid carbon nanotubes and nanosilica under quasi-static pressure load

In this study, the effect of carbon nanotubes (CNT) and silica nanoparticles on quasi-static behavior of fiber–metal laminates (FML) has been experimentally scrutinized. FML consists of two layers of aluminum alloy plates and four composite layers including CNT/nanosilica-reinforced epoxy resin and glass fibers. The effect of weight percentage of carbon nanotube and nanosilica incorporated and their weight ratio in resin epoxy on the performance of FMLs against quasi-static compressive load has been considered. Furthermore, the design of experiments method and response surface methodology have been put into practice to develop an accurate mathematical relationship between the input parameters and the response variable. After designing and performing the experiments based on analysis of variance, a mathematical model corresponding to the real process is obtained. Moreover, the presented model has been validated by statistical methods. The results of this study indicate that the energy absorption capacity of these materials significantly increase through adding CNT to the FML, the highest failure force of 11.64 kN was obtained for FLMs comprising 0.6 wt.% of CNT and 3 wt.% of SiO2. An improvement of 27.88% and 45.86% in the absorbed energy and failure force was achieved, respectively, by adding 3 wt.% of SiO2 and 0.6 wt.% of CNT to FLM compared to pristine FLM.

A Flexible Pressure Sensor Based on PDMS-CNTs Film for Multiple Applications

With the fast development of electronic skin, there is a great demand for wearable sensing devices. Herein, a piezoresistive sensor has been fabricated comprising a conductive film of Polydimethylsiloxane (PDMS)-carbon nanotubes (CNTs) sandwiched by two protection films of PDMS. A simple and low-cost manufacturing method has been proposed to wrap CNTs inside the flexible PDMS to obtain a soft sensor with excellent conductivity, high sensitivity, and fast response to various pressures. Additionally, films with different percentages of CNTs were compared. The results show that the film with 7% CNTs has higher conductivity and sensitivity. Moreover, the surface morphologies and microstructures of the superior PDMS-CNTs film were studied by scanning electron microscope, and sensing properties of the pressure sensor were tested. Furthermore, applications of single sensor and sensor array were studied. The results exhibit that the as-prepared pressure sensor successfully detected different human motions and recognized Morse code and words, indicating that the portable sensor can be potentially applied in wide areas such as smart devices and flexible robotics.

Mechanical properties of asphalt concrete modified with carbon nanotubes (CNTs)

Three different percentages of carbon nanotubes (CNTs) (0.1%, 0.5%, and 1% by mass of asphalt cement) were used to modify conventional asphalt cement (60/70) in this study. Mechanical properties of modified asphalt cement and mixture were evaluated. Penetration grade, kinematic viscosity, softening point and dynamic shear rheometer test were measured to evaluate physical properties of modified asphalt cement. The results exhibited that modifying asphalt cement with CNTs decreased its penetration and increased its kinematic viscosity and softening point. Rutting parameter increased with CNTs at the given temperature for both unaged and RTFOT-aged samples. Marshall stability tests, low temperature cracking tests, indirect tensile tests and wheel tracking tests were conducted to assess the mechanical performance of modified hot asphalt mixture. The Marshall stability increased with CNTs but no significant difference at 0.5 and 1.0 wt%, while Marshall flow decreased with CNTs. The results of wheel tracking test showed that rut depth decreased by 45% upon adding 0.5% CNTs by weight of asphalt cement; also, this percentage of CNTs endowed improvement in low temperature cracking and indirect tensile strength of the asphalt concrete. This study underlines that adding CNTs into asphalt cement enhances the performance of asphalt concrete pavement in both hot and cold weather, which in turn prolongs the pavement’s service life and saves maintenance expenses.

Electrical properties in polyester resins: comparison of the use of carbon nanotubes (CNT) and carbon black (CB)

This work presents a comparison in the production of electrical conductivity polyester resins by doping it with two types of carbonous fillers; carbon nanotubes (CNT) and carbon black (CB). These polyester resins are used to obtain electrical conductivity powder gel coat. This type of coating reduces cycle times in the manufacture of composites due to the fact that significantly decrease curing time of the gel coat and eliminate secondary operations for the application of the final coating in the composite. Electrical conductivity with different fillers content and percolation thresholds obtained in the simulation phase are detailed. The results obtained in the simulation are validated at the pilot plant level taking into account the influence of the loading percentage on the resin processing. Finally, a comparison between the results obtained with the different percentage of CNT and CB is made. The results of the simulation show that the value of the percolation threshold is much lower in the case of CNT (about 3% in the case of CNT versus 35% in the case of CB). The experimental results indicate the strong dependence of the electrical properties on the production process obtaining variations of up to two orders of magnitude in the experimental results using the same percentage of CNT but different type of polyester resin.

Experimental and modelling of temperature-dependent mechanical properties of CNT/polymer nanocomposites

Polymer-matrix composites (PMC) reinforced with nanofillers are in constant demand in various industrial applications. Among nano reinforcements, carbon nanotubes (CNT), show a unique combination of physical properties. Often, PMC/CNT composites perform under harsh operating and environmental conditions ranging from aggressive chemical attacks to high temperatures. Material characterization is critical for correct implementation in multifunctional systems. In this study, we have developed two Representative Volume Elements based on the formation of agglomeration above 2 wt% percentage of CNTs. Using finite element analysis (FEA) we studied the mechanical properties of the nanocomposites as a function of temperature. The viscoelastic properties of different percentages of nanofillers (i.e., 0.5, 1, 2, 4, 5 wt%) were derived. Experimental validation was performed with the samples containing the percentages of nanofillers. The samples were tested using Dynamic Mechanical Analysis (DMA) equipment employing the three-point bending method at a fixed frequency. The data shows that the nanofillers drastically influenced the storage, loss modulus and loss factor with a small addition of carbon nanotubes. The viscoelastic properties are presented from temperatures ranging from 40 ℃ to 120 ℃. Finally, a good agreement between the numerical and experimental approaches was found.

Comparison and identification of efficient nanoparticles to improve the impact resistance of glass/epoxy laminates: Experimental and numerical approaches

This research has studied the low-velocity impact (LVI) response of glass-epoxy composite laminates reinforced with different percentage of carbon nanotube (CNT) and nanoclay particles. The obtained results facilitate industrialists’ decision-making on selection of high-performance and cost-effective nanoparticles. Through quasi-static indentation (QSI) tests, the optimal percentages of nanoclay, and CNT were identified, and the impact test was performed on them at wide range of energies. Three key indexes were presented to evaluate the composite resistance against impact loads. The results indicate that both types of nanoparticles have contributed to an improvement in impact resistance. Moreover, a finite element analysis was performed using Abaqus/Explicit package, in which the results were in good agreement with experimental values.

Sequential and selective shape memory by remote electrical control

Shape memory (SM) materials have been widely investigated for several years. Most polymers present SM behaviour based on their thermo-mechanical properties. However, they are usually stimulated by an external heating source, hindering their industrial application. The addition of carbon nanotubes (CNT) allows turning conventional SM polymers into electro-active actuators. In this regard, the resistive heating by the Joule effect is considerably fast with a low energy cost.The most used epoxy resins cured at high temperature are based on diglycidyl ether of bisphenol A (DGEBA) cured with aromatic amine hardeners, such as diaminodiohenylsulfone (DDS) and 4,4′diamine-diphenylmetane (DDM). In this work, they were synthesised with modification of the epoxy/amine ratio to vary the crosslinking density of networks so as to build up different viscoelastic properties in order to tailor their SM behaviour. Electrically conductive nanocomposites were manufactured by adding a CNT percentage above the percolation threshold.A comparison of SM behaviour stimulated by traditional convection and resistive heating was carried out, confirming the higher recovery ratio, speed, and applicability of the electrical stimuli. In addition, the configuration of electrodes allows the design of self-deployable materials with remote control. In this way, the most common dual-shape SM polymers (one permanent shape and one temporary shape) can easily develop several stable temporary shapes. Moreover, the electrical remote control provides sequential and selective actuators, enhancing their performance for developing smart structures with shape memory capability.

Experimental Investigation on Mechanical Properties of Carbon Nanotube-Reinforced Epoxy Composites for Automobile Application

Carbon nanotubes are established as a superior form of carbon. These have superior characteristics in terms of mechanical and chemical properties when compared to the other fibres available. High-strength fibres can be employed in a composite in a short form and mass-produced to fulfil high demands in composite applications. These composites can meet the strength requirements of nonstructural and structural components in a wide range of industries. Because of their light weight and excellent strength-to-weight ratio, these composites can be used in a wide range of applications. With Young’s modulus as high as 1 TPa and tensile strength up to 63 GPa, they are among the stiffest and strongest fibres. There is currently a lot of interest in using carbon nanotubes in a matrix to take advantage of these features. There have been a variety of polymer matrices used, and nanotube/ceramic and nanotube/metal composites are gaining popularity. The study of these materials is an ongoing process, as researchers and design engineers have yet to realize their full potential. Carbon nanotubes (CNTs) are used in this study to create the composite with the resin. The percentage of CNT used as a filler material in the composite is varied from 1 to 4 percent, with the best percentage chosen for optimal mechanical properties.

Iron encapsulated carbon nanotube composites embedded in alumina with enhanced magnetic properties

Alumina is an essential ceramic insulator, while carbon nanotubes (CNTs) have intriguing mechanical, thermal, electrical, and magnetic properties. We report on the synthesis of CNTs/Al2O3 nanocomposites using the chemical vapor deposition (CVD) process using iron as a catalyst. The as-prepared composite's structure and morphology are characterized by transmission electron microscope, scanning electron microscope, X-ray diffractometer, thermogravimetric analyzer, and Mössbauer spectroscopy. The experimental results show that these composites contain CNTs of an average diameter of 40 nm distributed homogenously within the alumina matrix. The percentage of CNTs within the composites is at 7%. The CNT/Al2O3 nanocomposites demonstrate a dramatic enhancement of ferromagnetic properties during vibrating sample magnetization measurements. As compared to the magnetization of 0.03 e.m.u./g at an applied field of 1.5 T for the Fe-catalyzed Al2O3, the saturation magnetization of CNT/Al2O3 is 1.78 e.m.u./g, which represents an increment of ∼5800%. The coercivity of CNTs/Al2O3 composites increased from 0.036 T at 300 K to 0.285 T at 5 K. This study provides a relatively simple approach to blending the magnetic properties with potential thermoelectric materials.

MWCNTS-YSZ coating deposited by plasma thermal spray on INCONEL 738 low carbon substrate

The surface of Inconel 738 LC samples has been coated with carbon nanotube and yttria stabilized zirconia utilizing the plasma thermal spray method. Various percentages of carbon nanotubes and yttria stabilized zirconia were utilized in the coating (100 percent nano YSZ, 96 percent nano YSZ +4 percent CNTs, 94 percent nano YSZ +6 percent CNTs, and 92 percent nano YSZ +8 percent CNTs). After coating, a cyclic hot corrosion testing has been conducted, followed by SEM and XRD on all samples. SEM cross-section micrographs were utilized to quantify coating thickness. After 50 hrs of corrosion in 67 percent wt. V2O5 +33 percent wt. Na2SO4 at 950 degree centigrade, the changing weight of absence and coated specimens was measured. The cumulative weight change per surface area of coated specimens at temperatures of 950 °C was found to be 0.0095, 0.0075, 0.006, and 0.0057 mg.cm–2, (E,F,G,H) respectively. The best coating to resist hot corrosion was showed by specimens coated with 92% wt. yttria +8%wt. carbon nanotube. There are no oxides in the base specimens, according to X-rays of coated samples. Images of scanning electron microscopy for the surface layer revealed that it has a significant porosity and that some of the layer of coating s had microcracks.

Impact resistance of short carbon fibre-carbon nanotube-polymer matrix hybrid composites: A stochastic multiscale approach

A multiscale approach is used here to investigate the impact properties of carbon fibre/carbon nanotube-reinforced polymer. For this purpose, the mechanical properties of the carbon nanotubes (CNTs) are obtained by molecular dynamics simulations. Then, they are included in the polyethene matrix, and the mechanical properties of CNT-reinforced polyethene are computed using a stochastic approach. Considering the CNT-reinforced polyethene as the matrix, the effect of adding the carbon fibres on its mechanical properties is investigated in the next step. Finally, utilizing a stochastic method, the macro-scale mechanical properties of carbon fibre/carbon nanotube-reinforced polymer are computed. Thereafter, the impact test is applied on the models. The finite element method is used to investigate the mechanical and impact properties of representative volume elements. The effects of waviness, volume percentage and aspect ratio of the carbon fibre and CNT on the mechanical properties of the multiscale composite are evaluated. It is shown that reinforcing the polyethene matrix by carbon fibres and CNTs significantly increases its impact resistance. Adding 3% and 5% volume percentages of CNT into 3%-carbon fibre/polyethene and 5%-carbon fibre/polyethene respectively, resulted in 26% and 47% improvement in the impact resistance of the composite.

Bonding performances of epoxy coatings reinforced by carbon nanotubes (CNTs) on mild steel substrate with different surface roughness

This paper investigated the bonding performances of epoxy coatings reinforced by carbon nanotubes (CNTs) as additives on mild steel substrates. Pure epoxy and CNT-reinforced epoxy coatings on four different surface roughness of steel substrate were tested using single lap shear (SLS) tests. The SLS experimental results indicated that, on rougher substrates, the addition of a small percentage of CNTs (0.75% by weight) could significantly improve the bonding performance and change the failure mode from adhesion fracture to partly cohesive failure by improving the toughness of coatings and the interfacial adhesion between the coatings and substrates. In addition, the contact angle tests and the surface characterizations using scanning electron microscopy (SEM) analysis before and after fracture indicated that the wettability of coatings on steel substrates improved significantly with the increase of surface roughness and mechanical interlocking was the main reinforcing mechanism on rougher substrates.

The Behavior of Carbon Nano-tubes (CNTs) as a Modifier to Resist Aging and Moisture Damage in Asphalt

Background: Moisture damage and aging take place together in asphalt binder as it is on road-pavement in service life and, therefore, quite challenging to overcome. Various techniques, such as crumb rubber, fibers, etc. have been applied to improve the behaviour of asphalt materials. The use of nanomaterials was found as one of the effective techniques to develop temperature performances of asphalt binder. Methods: This study investigated moisture damage and aging of asphalt binder mixing with the carbon nanotubes (CNTs) using Atomic Force Microscopy (AFM). The base binder was primarily modified with 4% SBS polymer. Later on, CNTs were mixed in different percentages (i.e. 0.5%, 1%, and 1.5%) by weight with the 4% styrene–butadiene–styrene (SBS) modified binders. A special functionalized (-NH3) AFM probe with spring constant 3.44 N/m was utilized to complete the study. Results: The results were compared with 4% SBS modified asphalt with and without CNT addition. The adhesion forces of dry samples were found smaller as compared to wet and aged asphalt samples of with and without CNT. However, the adhesion forces of wet and aged samples with the investigated percentage of CNT performed considerably better than those without CNT. Conclusion: This result indicated significant improvement of asphalt to overcome moisture damage and aging owing to exposure in the outdoor environment as a paving material. This study recommends any dosage (i.e. 0.5 to 1.5% by weight) of CNT with 4% SBS modified asphalt to resist moisture damage and aging in the field.

Fabrication and Characterization of Cold-Pressed and Sintered Aluminium - MWCNT Composites

In the present article aluminium matrix composites were fabricated by cold pressing and sintering technique. Multi-walled carbon nanotube (MWCNT) with various weight percentage 0.5, 1.0, 1.5 and 2.0 were added as a reinforcement to aluminium (Al) matrix. A planetary ball mill was used for mechanical alloying and even dispersion of carbon nanotubes (CNTs) in aluminium matrix. Tin (Sn) with 1.0 weight percent was used in composite to incite the sintering. The sintering was carried out at 500°C inside a tube furnace in an argon atmosphere. The morphology and structure of CNT and Al-Sn-CNT composite was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. The effect of MWCNT reinforcement on microhardness and wear properties of Al-Sn-CNT composite was investigated. The hardness of composites was improved significantly with increase in CNT fraction. The reduction in the coefficient of friction and improvement in the wear resistance of the Al-Sn-CNT composite was noticed with the increase in percentage of CNTs in the composite.

Determining Optimum Carbon Nanotubes Content for Asphalt Mixture in Road Pavements

Although small amount of binder in asphalt concrete mixture may commonly range from 3.5 to 5.5% of total mixture as per many international specifications, it has a significant impact on the total cost of pavement construction. Therefore, this paper investigated the effects of five carbon nanotubes contents of 0.05%, 0.1%, 0.15%, 0.2%, 0.25% by asphalt weight as an additive material for binder on performance characteristics of asphalt mixtures. Performance properties of CNTs modified asphalt mixtures were investigated through the Marshall stability (MS) test, indirect tensile (IDT) test, static modulus (SM) test, wheel tracking (WT) test. The results indicated that asphalt mixtures with CNT modified binder can improve both the rutting performance, IDT strength and marshall stability of tested asphalt mixtures significantly at higher percentages of carbon nanotubes. However, the issue that should be considered is the construction cost of asphalt pavement. Based on the asphalt pavement structural analysis and construction cost, it can be concluded that an optimum CNT content of 0.1% by asphalt weight may be used as additive for asphalt binder in asphalt mixtures.

Influence of CNTs on interface delamination resistance in broken ply carbon/CNT-epoxy composites

Ply break is often encountered in laminated fiber reinforced composites under impact loading and the interface of the broken ply and the adjacent intact ply acts as a preferential site for delamination initiation and propagation. Thus improving the resistance to delamination at the interface is important in design of such laminated composites. An attempt has been made to understand the influence of adding carbon nano tubes (CNTs) with epoxy in improving resistance to delamination at the interface of broken and intact plies in three phase carbon/CNT-epoxy laminated composites. Carbon/CNT-epoxy laminates with the central ply broken has been considered and three dimensional finite element analysis (FEA) has been carried out. Virtual crack closure integral (VCCI) and quadratic stress criterion (QSC) have been used to evaluate critical strain energy release rate (Gc ) as a measure of resistance against delamination. Considering different percentage of CNTs in epoxy, results show that addition of CNTs with the epoxy matrix up to a certain percentage leads to significant enhancement of Gc indicating the improvement in resistance to interfacial delamination.