Adding Carbon Nanotubes Research Articles

Исследование свойств смесей дизельного топлива с углеродными нанотрубками и характеристик его распыливания

The fuel economy and exhaust emissions of diesel engines can be improved by adding carbon nanotubes to petroleum diesel fuel. Carbon nanotubes, used as a promising nanoscale additive for diesel fuel, have high thermal conductivity and a large surface area to volume ratio. The thermophysical properties of these fuels, which depend on the composition of the mixtures, are analyzed in this study. Findings of research show that carbon nanotubes added to diesel fuel have little effect on its dynamic viscosity and thermal conductivity. By means of numerical models, we simulated the process of atomization and evaporation of diesel fuel with the different carbon nanotubes content in a constant volume combustion chamber. The accuracy of the calculations is confirmed by the good agreement between the calculated and experimental data. Simulation of mixture atomization showed that the jet length linearly depends on the carbon nanotubes content in diesel fuel. The more carbon nanotubes are in the mixture, the smaller the droplet Sauter mean diameter and the angle of the jet cone opening are. The presence of carbon nanotubes in diesel fuel insignificantly affects the fuel vapor content in it.

Boosting Mechanical Properties of Orthoses - Foot Ankle by Adding Carbon Nanotube Particles

In this process, optimum laminating properties were used in producing prosthesis and orthoses were researched and selected based on high yield, ultimate stresses, stresses of bending and fatigue properties. The process of the optimal selection is the Response Surface Methodology (RSM), which has been used to reach two parameters: reinforcement perlon fiber and percent of multi-strand carbon MWCNT nanotube combined with the matrix resin. The response surface methodology is a combination of mathematician and statistic techniques which are used for experimental model building and analysis of problems. This technique revealed 13 separate laminations samples with a percentage of separate Perlon layers No. and MWCNT Wt %. Tests were conducted for all lamination materials as defined in RSM methods and rendered by vacuum system, including fatigue tests for the ideal laminating material as opposed to laminations developed in the prior study (three Tensile test, Bending test and Fatigue tests according to the ASTM D638 and D790 respectively). Tests from the system version 10.0.2 of Design Expert found lamination (10 perlon layers and 0.75% of MWCNTs) to be the best according to overall yield, ultimate and bending loads in the 12 other laminations. Fatigue eventually revealed that constraints were applied to the stamina tension (2,66, 1,66) for optimum lamination, relative to ten perlon lamination layers and 424 lamination respectively.

Effect of adding carbon nanotubes into the matrix material on the buckling behavior of glass/epoxy composite plates: An experimental study

In this research, buckling of polymer matrix composite plates containing unidirectional glass fibers under in-plane pressure load is investigated. Moreover, the effect of adding carbon nanotubes as reinforcement into the matrix material on the critical buckling load of composite plates is studied. Using hand lay-up method, rectangular glass/epoxy composite plates with and without carbon nanotubes were fabricated. 0.25, 0.5 and 1.0 weight percent of carbon nanotubes were added to the epoxy resin and composite plates were subjected to the longitudinal in-plane pressure load. The plates were tested under fix ended boundary conditions utilizing Instron hydraulic universal testing machine. Based on the results, adding 0.5 weight percent of carbon nanotubes has the most influence on the critical buckling load of the plates. Results show that adding 0.5 weight percent of carbon nanotubes into the matrix material increases the critical buckling load of the carbon nanotubes /glass/epoxy plate more than two times with respect to that of glass/epoxy composite plate. Furthermore, when the carbon nanotubes weight percent reaches 1 %, because of carbon nanotubes agglomeration, carbon nanotubes are not dispersed well into the epoxy resin and the critical buckling load of the composite plate decreases. To validate the results, buckling analysis of glass/epoxy composite plate was done in Abaqus finite element software. Finite element models confirm the experimental results obtained.

Evaluating Tensile Strength in Butt Fusion and Electrofusion Joints in Nanocomposite HDPE Pipes

In this paper, high-density polyethylene (HDPE) composite pipes, reinforced with glass fibers (GF) and carbon nanotubes (CNTs), are manufactured using a novel extruder and multiple molten reprocessing cycles in a screw cylinder barrel. Moreover, the study investigates the tensile strength of the junction of these composite pipes. The results indicate that the Young’s modulus and the ultimate tensile strength of the fabricated nanocomposite pipes increase by 150 and 163 %, compared to the conventional polyethylene pipes, respectively, using 2 wt% carbon nanotubes and two reprocessing iterations in the cylinder barrel. The effects of adding carbon nanotubes to HDPE and the number of reprocessing cycles on the fracture mechanism of the nanocomposite pipes have been explored based on SEM images and DSC testing. The pipes are joined using the two most common available methods; namely, butt fusion and electrofusion, and their respective tensile strengths are compared. The results demonstrate an 82 % and a 37 % decrease in the tensile strength for the welded pipes, compared to the non-welded pipes, using butt fusion and electrofusion, respectively. However, the tensile strength in the welding of the GFRP nanocomposite pipes can be enhanced by increasing the interconnection between the fibers at the junction. Nevertheless, butt fusion is not recommended for joining FRP composite pipes, while electrofusion can be utilized with some modifications.

Carbon nanotubes films in glass fiber polymer matrix forming structures with high absorption and shielding performance in X-Band

Thin films based on carbon nanotubes materials are used to form layered structures for electromagnetic absorption and shielding applications over X-Band. Measurements in a WR-90 waveguide with a Vector Network Analyzer are carried out to determine the dielectric characteristics of the materials. Samples of graphene and carbon nanotubes are constructed in an epoxy resin polymeric matrix as a one-layer structure. A two-layer structure based on epoxy resin and glass fiber combined with carbon nanotubes films is also examined. Films have a thickness of around 70 μm and have a significant effect in the attenuation of the electromagnetic field. A decrease of more than 20 dB in the Transmission Coefficient can be achieved even with few carbon nanotubes films placed intermediately in a glass fiber polymer matrix. Simulated results compared to measurements of the waveguide setup show satisfactory agreement. Planar layers composed of the above materials are also examined for electromagnetic absorption and shielding performance. A one-layer planar structure that consists of the above carbon nanotubes films in a glass fiber polymer matrix and has a total thickness of 2.7 mm is proposed. It is intended for high shielding effectiveness applications presenting a shielding effectiveness variating between 27 dB and 42 dB over X-Band. However, for both high shielding and absorption applications, a two-layer planar structure with a total thickness of 5.7 mm is designed. The structure consists of successive carbon nanotubes films in a glass fiber polymer matrix as the bottom layer and carbon nanotubes in an epoxy resin matrix as the top layer. The structure presents a shielding effectiveness between 27 dB and 40 dB over X-Band while absorption can reach 95% around 10 GHz. As shown, adding carbon nanotubes in film structure, even with a thickness in the order of μm, inside a polymer matrix can greatly increase the electromagnetic shielding and absorption performance showing also a high attenuation of electromagnetic field.

Poly(ionic liquid)-crosslinked graphene oxide/carbon nanotube membranes as efficient solar steam generators

Graphene oxide (GO) is regarded as a promising candidate to construct solar absorbers for addressing freshwater crisis, but the easy delamination of GO in water poses a critical challenge for practical solar desalination. Herein, we improve the stability of GO membranes by a self-crosslinking poly (ionic liquid) (PIL) in a mild condition, which crosslinks neighbouring GO nanosheets without blemishing the hydrophilic structure of GO. By further adding carbon nanotubes (CNTs), the sandwiched GO/CNT@PIL (GCP) membrane displays a good stability in pH = 1 or 13 solution even for 270 days. The molecular dynamics simulation results indicate that the generation of water nanofluidics in nanochannels of GO nanosheets remarkably reduces the water evaporation enthalpy in GCP membrane, compared to bulk water. Consequently, the GCP membrane exhibits a high evaporation rate (1.87 kg m−2 h−1) and displays stable evaporation rates for 14 h under 1 kW m−2 irradiation. The GCP membrane additionally works very well when using different water sources (e.g., dye-polluted water) or even strong acidic solution (pH = 1) or basic solution (pH = 13). More importantly, through bundling pluralities of GCP membrane, an efficient solar desalination device is developed to produce drinkable water from seawater. The average daily drinkable water amount in sunny day is 10.1 kg m−2, which meets with the daily drinkable water needs of five adults. The high evaporation rate, long-time durability and good scalability make the GCP membrane an outstanding candidate for practical solar seawater desalination.

Computational analysis of the effects of carbon nanotubes on the bending, buckling, and vibration characteristics of carbon fabric/polymer hybrid nanocomposite plates

In this paper, the effects of adding carbon nanotubes (CNTs) on the bending, buckling and free vibration characteristics of carbon fabric/polymer hybrid nanocomposite plates (HNCPs) are investigated using a computational approach. First, a hierarchical finite element micromechanics approach is proposed to estimate the hybrid composite properties. The formation of interfacial region due to the non-bonded van der Waals interactions among the CNTs and polymer is considered. Then, finite element analysis is carried out to compute the mechanical responses of the CNT/carbon fabric hybrid composite structures. It is found that incorporating the CNTs into the carbon fabric-reinforced polymer materials results in an enhancement of buckling capacity and natural frequencies of the HNCPs. The maximum deflection of the traditional carbon fabric/polymer composite plates is decreased by adding the CNTs. A parametric study is accomplished to evaluate the influences of amount and aspect ratio of CNTs, material properties and thickness of interfacial region as well as the thickness and various shapes of plate on the flexural deformation, buckling and vibration characteristics of the HNCPs. The predictions are compared with those available in the literature to verify the validity of the presented computational model.

Tailoring of Thermo-Mechanical Properties of Hybrid Composite-Metal Bonded Joints.

Metallic substrates and polymer adhesive in composite-metal joints have a relatively large coefficient of thermal expansion (CTE) mismatch, which is a barrier in the growing market of electric vehicles and their battery structures. It is reported that adding carbon nanotubes (CNTs) to the adhesive reduces the CTE of the CNT-enhanced polymer adhesive multi-material system, and therefore when used in adhesively bonded joints it would, theoretically, result in low CTE mismatch in the joint system. The current article presents the influence of two specific mass ratios of CNTs on the CTE of the enhanced polymer. It was observed that the addition of 1.0 wt% and 2.68 wt% of multi-walled CNTs (MWCNTs) decreased the CTE of the polymer adhesive from °C (pristine level) to °C and °C, respectively, by 22% and 41% reductions.

Development of nanomodified multifunctional protection systems for wood structures

Introduction. Nowadays multi-storey buildings, composed of wood structures, are built in different countries. The durabi-lity of structures depends to a large extent on the protection systems used. The most effective ones are multifunctional protection systems that rise the fire protection ability, hydrophobicity, and biostability of structural materials. The application of carbon nanotubes is expected to improve the uniformity of a protective layer and the coating performance. The purpose of the project is to develop a multifunctional protection system designated for wood structures. This system must ensure their fire resistance and hydrophobicity without deteriorating the mechanical properties of wood.
 Materials and methods. Pine wood samples were used in the research. Carbon nanotubes were used as nano-modifiers. Wood samples, surface-modified with methylphosphonic (MPH) and nitrilo-trimethylphosphonic (NPH) acids, were used to develop multifunctional protection systems. Integrated protection systems were developed by adding carbon nanotubes. Fire hazard properties were assessed pursuant to GOST 27484-87, water absorption properties were analyzed pursuant to GOST 16483.20-72, mechanical properties were addressed with reference to GOST 16483.11-72 and 16483.10-73. Hydrophobicity was evaluated using the wetting angle method. The character of the sample surface and its chemical composition were studied using the double-beam scanning electron-ion microscope FEI Quanta 3D FEG with an EDAX Octane select attachment needed for the energy dispersion analysis.
 Results. All studied coating systems belong to the first group of the fire retardant efficiency, the best of them reduce weight loss in the course of combustion of samples: Δweight = 3.7 – 1.34 %. Wood develops hydrophobic properties; its water absorption reduces 1.5-fold, while its across-fiber mechanical compressive strength goes up 1.6-fold. The assessment of the wood surface and its chemical composition shows that high fire resistance correlates with higher phosphorus content in the char layer formed during combustion.
 Conclusions. Surface modification of wood by protection systems is recommended as an effective means of rising the durability of structures.

REVIEW ENHANCEMENT OF THERMAL CONDUCTIVITY AND HEAT TRANSFER USING CARBON NANOTUBE FOR NANOFLUIDS AND IONANOFLUIDS

This paper attempts to present a clearer picture, a detailed and up to date review of the heat transfer enhancement and thermal conductivity improvement for conventional fluids by adding carbon nanotubes or hybrid carbon nanotubes in the base fluid to obtain nanofluids or ionanofluid. Carbon nanotubes have attracted the interest of different researchers because of their high thermal conductivity that exceeds other equivalent types of nanoparticles. In view of this, the effect of different key factors like concentration, temperature and shape type of nanoparticles on the thermal conductivity improvement in nanofluids were reviewed. Moreover, the effect of surfactant stabilizers on the carbon nanotubes nanofluids distribution was evaluated. The results that have been obtained from the valuable studies have been analyzed and some gaps have been found that need to be re-reviewed by the researchers

Synthesis and thermodynamic characterization of poly(methyl methacrylate)/multiwall carbon nanotube nanocomposite

In the first part of this study, poly(methyl methacrylate) (PMMA)/multiwall carbon nanotube (MWCNT) nanocomposite was synthesized by adding carbon nanotube before polymerization with bulk polymerization. Surface morphology of the PMMA/MWCNT nanocomposite and the PMMA/MWCNT nanocomposite with Chromosorb W was characterized by scanning electron microscopy (SEM). Surface and thermodynamic properties of the PMMA/MWCNT nanocomposite were investigated by inverse gas chromatography (IGC). The surface acid base character and dispersed surface energy of the PMMA/MWCNT were determined at infinite dilution. The entropy of adsorption, ∆SS, the specific free energy of adsorption, ∆GS, and the enthalpy of adsorption, ∆HS, of selected polar solvents were determined on the PMMA/MWCNT nanocomposite. The values of ∆HS were correlated with both the acceptor and donor numbers of the solvents to determine the Lewis acidic constant KA and the Lewis basic constant KD of the PMMA/MWCNT nanocomposite. The PMMA/MWCNT nanocomposite selectivity was investigated using the acetate and alcohol isomers by IGC at temperatures between 393.2 and 403.2 K. Glass transition temperature (Tg) was determined using differential scanning calorimetry (DSC) and IGC method.The interactions between the PMMA/MWCNT nanocomposite and 12 solvents were propped at a temperature range (423.2–448.2 K). The Flory–Huggins interaction parameter, and the weight fraction activity coefficient, of the PMMA/MWCNT nanocomposite solvent system were estimated at temperatures between 423.2 and 448.2 K. The solubility parameter of the PMMA/MWCNT nanocomposite, δ2, was calculated as 14.0 (cal/cm3)1/2.

Multi-walled carbon nano-tubes for enhancing the performance of cementitious composites

Due to exceptional properties, multi-walled carbon nano-tubes (MWCNTs) are designated as a promising reinforcing material for the nano-modified cementitious composites. The performance of cementitious composites with MWCNTs on the mechanical, durability, and microstructure properties was investigated in this study. The MWCNTs were effectively dispersed by the sonication method using high-frequency ultrasonic waves. The flexural strength, compressive strength, density, porosity, and stress-strain curves of cementitious composites reinforced with different concentrations (0.1, 0.2, 0.3, 0.4, and 0.5 wt%) of MWCNTs were studied. The enhanced flexural and compressive strength demonstrates the exceptional reinforcing behaviour of the MWCNTs. Additionally, density outcome indicates that as the percentage of MWCNTs in the matrix increases, density increases, and the optimum content was obtained as 0.3 wt%. The pores of cementitious composites can be reduced by adding carbon nano-tubes, which was perceived through a microstructural study using SEM micrographs. Study outcomes establish that in addition to the advantages provided by the nano-tube reinforcement in augmenting strength, nano-tubes can also help in reducing the porosity of the composites. The effectiveness of this promising nanomaterial related to its field application is also highlighted.

Theoretical and experimental researches of operating properties of bitumen reinforced with carbon nanotubes

The current level of economic development requires numerous road transport, which is constantly increasing, as a result, the roadbed is destroyed quite quickly. To maintain the durability of the road surface, various modifications are used to improve the physical properties. During the research, theoretical calculations and experimental confirmation of changes in the properties of bitumen when adding carbon nanotubes were carried out. Three concentrations of carbon nanotubes were tested: 0.1%, 0.01%, 0.001% in the bituminous mixture, as well as a reference sample without adding carbon nanotubes to compare changes in indicators. Based on the research carried out in the course of this work, it can be argued that the proposed method of strengthening the asphalt concrete coating by reinforcing the main component of the coating (bitumen) improves its physical and mechanical properties and, accordingly, increases the service life of the roadbed.

Preparation and arc erosion behavior of AgNi10 contact material with different allotropes of carbon addition

AgNi10 contact materials adding carbon nanotubes (CNTs), nanographene sheets (GNPs), and graphite(Gr) were fabricated via powder metallurgy method. To investigate the influence of different allotropes of carbon addition on microstructure and properties of AgNi10 contacts, the arc erosion behavior was tested under a DC resistive load of 24V/20A. The results indicate that uniformly dispersed CNTs and GNPs present obvious strengthening effect while Gr leads to strength reduction of AgNi10 contacts. The contacts adding CNTs and GNPs show well-scattered and stable arc. Material transfer from cathode to anode was observed but the mass change is less than that of the contact without addition. The contacts with CNTs and GNPs addition show smooth surface without deep crater on the cathode or sharp tip on the anode. Moreover, no obvious splash of molten Ag and Ni was observed. Anti-welding performance is improved with all the carbon allotropes. The contact added GNPs presents the best arc erosion performance with average arc time as 14.7 ms, average contact resistance as 4.51mΩ, and maximum welding force as 38cN.

Cyclic heating and mechanical properties of CNT reinforced cement composite

The heating performance of cement composites can be improved by adding carbon nanotubes (CNTs); however, cyclic heating by CNTs can reduce the heating and mechanical properties of CNT-reinforced cement composite in the long term. This study investigated the cyclic heating and mechanical properties before and after the heating of CNT-reinforced cement composites. Paste specimens were fabricated using the 0.1–0.5 wt% content of CNT as the major variable, and a cyclic heating experiment was performed for applied voltages of 50 and 100 V. The compressive strength before and after cyclic heating were measured and compared. In addition, microstructural changes of the CNT-reinforced cement composite after cyclic heating was evaluated by thermogravimetric analysis, mercury intrusion porosimetry, and scanning electron microscopy. As the dosage of CNT increased, the temperature of the specimen increased, and as the heating cycle increased, the heating performance tended to decrease. This seems to be attributed to the occurrence of microcracks by the different thermal expansion coefficients, and by the additional hydrates generated by the increased temperature of the specimen.

Bending performance enhancement by nanoparticles for FFF 3D printed nylon and nylon/Kevlar composites

Fused filament fabrication (FFF) has been a major 3D printing technique for making thermoplastic products for decades. However, FFF printing for thermoplastic composites with aligned continuous fibers has been reported with limited success for only several years. In this study, we introduce an enhanced FFF-based approach by incorporating nanoparticles to the thermoplastic composites with continuous fibers. Our investigation focuses on the bending properties of FFF-printed fiber reinforced composites with and without nanoparticles. With Nylon 6 (PA 6) being the matrix material, nanocomposite filaments are obtained by adding carbon nanotubes (CNTs), graphene nano platelets (GNPs), or amino (NH2-) functionalized GNPs. Various PA 6 matrix nanocomposite filaments are prepared through mixing and filament extrusion process. The nanocomposite filaments are then 3D printed with or without continuous Kevlar fiber prepreg filaments. For 3D printed pure PA 6, the addition of 1 wt% GNP-NH2 increases the flexural strength and bending modulus by 334% and 315%, respectively. For 3D printed PA 6/Kevlar composite, the addition of 1 wt% GNP-NH2 increases the flexural strength and bending modulus by 195% and 35%, respectively. However, the addition of CNTs or GNPs (up to 1 wt%) is less effective as compared with GNP-NH2. The underlying mechanisms are discussed based on the matrix/fiber interfacial analysis.

Influence of CNTs addition on structural and superconducting properties of mechanically alloyed MgB<sub>2</sub>

The result of adding carbon nanotubes (CNTs) to the lattice parameters, critical temperature and electrical resistivity of the MgB2 superconductors is reported. Structurally, the addition of CNTs was found to decrease the a-lattice from 3.086 Ã… of CNTs free sample to 3.078 Ã… and 3.074 Ã… of 5% and 10% CNTs added samples due to a substitution of C at the B site which presence in the form of Mg(B1-xCx)2 main phase. The doping level x of CNTs added samples were 2.25 at% and 3.75 at% respectively. The unreacted CNTs presence as the second phase and further acting as the suppression agent for crystallite growth. The addition of CNTs is also to refine the grain size and improves the grain connectivity. Samples show a metallic behavior which observed only at temperatures above ~41 K, below which, a sharp transition of resistivity occurred toward zero resistivity, confirming the superconductivity behavior. This study concluded that the effect of CNTs addition affects the structural parameters and superconducting properties. The addition of the CNTs to 5% and 10% has changed the zero critical temperature of the sample material to respectively 39.20 and 38.02 K from 39.31 K of CNTs free sample.

Characterizing delamination toughness of laminated composites containing carbon nanotubes: Experimental study and stochastic multi-scale modeling

The influence of adding carbon nanotubes (CNTs) to matrix on the delamination resistance of laminated composites is evaluated experimentally and theoretically. A proper multi-scale modeling technique is developed for estimating the interlaminar fracture toughness of laminated composites containing CNTs. Therefore, all involved scales and corresponding parameters are taken into account. Non-bonded interaction is considered between CNT and polymer using adapted cohesive laws resembling CNT-polymer adhesion. The developed modeling is implemented stochastically to take into account the manufacturing-induced inconsistencies. CNT lengths, agglomeration, waviness patterns and orientations are all treated as random variables and thus a full stochastic multi-scale modeling procedure is conducted. Laminated composites with uni-directional glass fibers and epoxy resin reinforced with different portions of CNTs are fabricated for experimental analysis. The specimens are subjected to Mode-I loading and the delamination toughness of the specimens is measured. Considerable improvements are observed due to incorporating CNT as a novel technique to increase the delamination resistance of laminated composites. The outputs of the modeling procedure are in a very good agreement with conducted experimental study.

Influence of CNTs addition on structural and superconducting properties of mechanically alloyed MgB 2

The result of adding carbon nanotubes (CNTs) to the lattice parameters, critical temperature and electrical resistivity of the MgB 2 superconductors is reported. Structurally, the addition of CNTs was found to decrease the a -lattice from 3.086 A of CNTs free sample to 3.078 A and 3.074 A of 5% and 10% CNTs added samples due to a substitution of C at the B site which presence in the form of Mg(B 1-x C x ) 2 main phase. The doping level x of CNTs added samples were 2.25 at% and 3.75 at% respectively. The unreacted CNTs presence as the second phase and further acting as the suppression agent for crystallite growth. The addition of CNTs is also to refine the grain size and improves the grain connectivity. Samples show a metallic behavior which observed only at temperatures above ~41 K, below which, a sharp transition of resistivity occurred toward zero resistivity, confirming the superconductivity behavior. This study concluded that the effect of CNTs addition affects the structural parameters and superconducting properties. The addition of the CNTs to 5% and 10% has changed the zero critical temperature of the sample material to respectively 39.20 and 38.02 K from 39.31 K of CNTs free sample.

Hybrid Microencapsulated Phase-Change Material and Carbon Nanotube Suspensions toward Solar Energy Conversion and Storage

In this study, a new type of functional hybrid suspension for solar energy conversion and thermal energy storage was prepared by adding carbon nanotube (CNT) and microencapsulated phase-change material (MEPCM) into deionized water. MEPCM with octadecane as the core material and titania (TiO2) as the shell material was synthesized by the sol–gel method. The MEPCMs were spherical particles with diameters of 2–4 μm, and the thickness of the shell was about 100 nm. The MEPCM achieved better thermal stability and thermal conductivity than the pure octadecane due to the TiO2 shell. The melting and solidification latent heats of the MEPCM were about 154.24 and 154.26 J/g, respectively. The encapsulation efficiency of octadecane was calculated to be 65.84%. Most of all, the novel hybrid CNT and MEPCM suspensions exhibited remarkable dispersion stability owing to the stable reticular structure composed of CNT in the suspension. Compared with pure water, the thermal conductivity, specific heat of the MEPCM/CNT suspension improved by 34.48 and 43.57%, respectively and the photo-thermal conversion efficiency reached a high value of 86.0%. This work provided a new type of hybrid functional suspension towards direct absorption solar collector for solar energy conversion and storage.