Effect Of Multi-walled Carbon Nanotubes Concentration Research Articles

Studying the Incorporation of Multi-Walled Carbon Nanotubes in High-Performance Concrete

The current work aimed to study nanomodified HPC with multi-walled carbon nanotubes (MWCNT). The effect of MWCNT concentration, from 0% to 0.6% of cement weight, was evaluated on HPC multi-level output properties, namely, the flowability, mechanical strength, electrical resistivity, and microstructure. In addition, a tentative, simplified, and more cost-effective method based on dispersion of a high-pH solution of hydroxide was also adapted to disperse the MWCNT before incorporation in fresh HPC mixtures. Adding 0.2–0.6% MWCNT reduced HPC workability even with a higher superplasticiser dosage. The electrical resistivity was 484.58 Ω m for the HPC without MWCNT at 28 days of curing, while the samples with 0.2%, 0.4%, and 0.6% MWCNT presented 341.41 Ω m, 363.44 Ω m, and 360.34 Ω m, respectively. The use of 0.2–0.6% MWCNT in HPC decreased the flexural and compressive strength by 20% and 30%, respectively. The HPC performance decrease with MWCNT seemed to be related to relatively significant agglomerations of the long MWCNTs, namely, in HPC-0.6% samples. New developments are needed to state a simple and cost-effective dispersion method for MWCNT incorporation in HPC. In addition, smaller dosages of MWCNT are suggested for future research works.

The Effect of Multi-Walled Carbon Nanotubes on the Compressive Strength of Cement Mortars

In this work, multi-walled carbon nanotubes (MWCNTs) have been synthesized using a modified method of solid-phase pyrolysis. The MWCNTs are effectively dispersed using a simple and facile method such as ultrasonic energy without and with surfactant for two different sonication times (15 min and 40 min). In the present study, the effect of MWCNT concentration (0.001, 0.01, 0.05, 0.1 wt.%) on the compressive strengths of cement mortars has been investigated. Compressive tests were carried out on an automatic pressure machine (C089) with a loading rate of 0.5 kN/s at the age of 7 days and 28 days. It is shown that the optimal value of the nanotubes’ concentration does not exist in the case of 15 min of sonication time, whereas the optimal value for 40 min of sonication time without and with surfactant is 0.01%. Moreover, in the absence of surfactants, the strength of the specimen over 7 days of hardening increased by 13%, and by 19.5% in the presence of surfactants. The compressive strength for a curing period of 28 days increased by 6.3% and 13.8%, respectively.

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.

Morphology, Barrier, Mechanical and Electrical Conductivity Properties of Oil-Extended EPDM/MWCNT Nanocomposites

Oil- extended ethylene propylene diene monomer (EPDM) elastomer nanocomposites have been made by using multiwalled carbon nanotube (MWCNT) nanofiller as a reinforcing agent. The effect of MWCNT concentration on morphology, bound rubber, swelling, and mechanical properties have been studied. EPDM/MWCNT interactions have been studied by scanning electron microscopy (SEM) and high- resolution transmission electron microscopy (HR-TEM) techniques. From the studies, it is observed that at lower MWCNT concentration (up to 4%), nanofillers are well separated and dispersed, but at higher loadings (6%) formation of agglomerates takes place. Hence it is expected that percolation limit of MWCNT in oil-extended EPDM occurs at around 4% concentration. The extent of reinforcement of MWCNT in EPDM matrix has been calculated in form of bound rubber (BdR) content and degree of swelling when exposed to solvents. BdR values of EPDM nanocomposites increase with MWCNT concentration hence confirmed the reinforcing nature of filler. Physico-mechanical properties like tensile strength, modulus and toughness of EPDM nanocomposites increases up to 4% MWCNT concentration, beyond which the effects are very marginal or decreases as filler-filler interactions exceed polymer-filler interactions. This confirmed the percolation threshold of MWCNT at 4% concentration. In addition to above, electrical conductivity of EPDM/MWCNT nanocomposites have been obtained as a function of frequency to measure the capability of a material to conduct electric current and it shows both frequency independent (DC) and dependent (AC) characteristic which increases exponentially in the applied field. AC conductivity of EPDM/MWCNT nanocomposites increases with filler concentration due to conductive nature of nanotube and a decrease in the mean free path of nanoparticles.

Multi-walled carbon nanotube doped PVA membrane for desalination

Abstract In this study, multi-walled carbon nanotubes (MWCNT) loaded polyvinyl alcohol (PVA) membranes were synthesized and applied for desalination by means of pervaporation technique. Membranes were characterized using scanning electron microscope (SEM). Sorption studies were carried out to determine the degree of swelling of the MWCNT/PVA membranes into different types of salt solution. Pervaporation experiments were carried using the pristine and MWCNT loaded membranes. The effect of MWCNT concentration and salt concentration on the swelling, flux and salt rejection were investigated at the constant temperature of 40 °C. As a result, greater than 92% of rejections were obtained using all membrane. The highest flux was obtained using 0.3 wt% MWCNT loaded membrane with the highest rejection of 98.8%. SEM analysis confirmed that the excess amount of particles caused agglomeration and negatively affected the desalination performance.

Influence of processing condition and carbon nanotube on mechanical properties of injection molded multi‐walled carbon nanotube/poly(methyl methacrylate) nanocomposites

ABSTRACTIn this work, multi‐walled carbon nanotubes (MWCNT) and poly(methyl methacrylate) (PMMA) pellets were compounded via corotating twin‐screw extruder. The produced MWCNT/PMMA nanocomposite pellets were injection molded. The effect of MWCNT concentration, injection melt temperature and holding pressure on mechanical properties of the nanocomposites were investigated. To examine the mechanical properties of the MWCNT/PMMA nanocomposites, tensile test, charpy impact test, and Rockwell hardness are considered as the outputs. Design of experiments (DoE) is done by full factorial method. The morphology of the nanocomposites was performed using scanning electron microscopy (SEM). The results revealed when MWCNT concentration are increased from 0 to 1.5 wt %, tensile strength and elongation at break were reduced about 30 and 40%, respectively, but a slight increase in hardness was observed. In addition, highest impact strength belongs to the nanocomposite with 1 wt % MWCNT. This study also shows that processing condition significantly influence on mechanical behavior of the injection molded nanocomposite. In maximum holding pressure (100 bar), the nanocomposites show highest tensile strength, elongation, impact strength and hardness. According to findings, melt temperature has a trifle effect on elongation, but it has a remarkable influence on tensile strength. In the case of impact strength, higher melt temperature is favorable. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43738.

PREPARATION OF PMMA/MWNTS NANOCOMPOSITE MICROCELLULAR FOAMS BY IN-SITU GENERATION OF SUPERCRITICAL CARBON DIOXIDE

Nanocomposites containing poly(methyl methacrylate) (PMMA) and surface functionalized Multi-Walled Carbon Nanotubes (MWNTs) were synthesized. The dispersion of MWNTs in PMMA was characterized using Transmission Electron Microscopy (TEM).The synthesized nanocomposites were successfully foamed using a simple method based on the in-situ generation of supercritical carbon dioxide (CO2). This method in contrast with conventional methods exempted from high-pressure pump and separated CO2 tank. The effect of MWNTs concentration, saturation temperature and saturation pressure on cellular morphology of the prepared microcellular foams were studied by Scanning Electron Microscopy (SEM), and average cell size and cell density of the prepared foams were studied by image analysis. An increase in cell density, as well as a reduction of cell size, was observed with an increase in the concentration of carbon nanotubes. It was also observed that an elevation of saturation temperature from 90 °C to 100 °C, at constant saturation pressure, leads to a higher cell density and a lower average cell size. Furthermore, an increase in saturation pressure results in a decrease in average cell diameter as well as an increase in cell density. However, the effects of MWNTs concentration on both of average cell size and cell density were proved to be more striking than those of saturation pressure.

The effect of MWNTs concentration and nanofiber orientation on mechanical properties of PAA nanocomposite nanofibrous web

In this research, nanocomposite nanofibrous webs of poly(acrylic acid) (PAA)/multi‐walled carbon nanotubes (MWNTs) were obtained via electrospinning. The effect of MWNTs concentration on the morphology and mechanical properties of PAA/MWNTs nanofibers was investigated by changing the MWNTs content from 0 to 5 wt%. The results showed that average diameter of nanofibers increased with increasing the MWNTs concentration and presence of MWNTs led to the enhancement of mechanical properties. Also, the results revealed that the strength, modulus, and elongation at break of samples increased 3.22, 2.70, and 4.27 fold, respectively, after adding 3 wt% of MWNTs. In addition, the effect of rotating speed of collector on the orientation of PAA nanofibers and its effect on mechanical properties was investigated. Scanning electron microscopy (SEM) studies demonstrated that the degree of nanofibers orientation increased with the augmentation of drum speed to 25 rps. Moreover, the average nanofibers diameter decreased with the increase of drum speed. Improvement of nanofiber orientation resulted in superior mechanical properties that is, higher strength and modulus of aligned nanofiber layers were obtained in comparison to nonaligned layers (12.6 and 26.6 fold, respectively). POLYM. COMPOS., 37:3149–3159, 2016. © 2015 Society of Plastics Engineers

Comparison on the Properties of Glass Fiber/MWCNT/Epoxy and Carbon Fiber/MWCNT/Epoxy Composites

A hand lay-up and vacuum bagging method was used in this study to fabricate glass fiber/epoxy laminated composites and carbon fiber/epoxy composite laminates with multi-walled carbon nanotube (MWCNT). The density, flexural properties, and burning rate of the laminated composites incorporated with different concentration of MWCNT (0.5, 1.0, and 1.5 vol%) were investigated and analyzed. Trend in the density, flexural and burning rate of glass fiber composite laminates were compared to those of carbon fiber composite laminates. Effect of MWCNT concentration on glass fiber composites properties varies from carbon fiber composite laminates. Incorporation of 0.5vol% of MWCNT has increased flexural strength by 54.4% compared to 5-ply glass fiber composite laminates. Nonetheless addition of 1vol% of MWCNT has only increased flexural strength by 34% compared to 5-ply carbon fiber laminated composites. Incorporation of MWCNT has successfully reduced the burning rate of the glass fiber composites as well as the carbon fiber laminated composites.

Design of a multiwalled carbon nanotube–Nafion–cysteamine modified tyrosinase biosensor and its adaptation of dopamine determination

In this work, a multiwalled carbon nanotube (MWCNT)–Nafion–cysteamine (CA) modified tyrosinase biosensor brings a new and original perspective to biosensor technology intended for the development of dopamine determination. Dopamine measurements were done at 0.2V with the amperometric method by the developed biosensor system. In addition, in this study dopamine determination was carried out by using the differential pulse voltammetry method between potentials of 0.4 and −0.15V. In the optimization studies of the biosensor, some parameters such as optimal pH, optimal temperature, optimal enzyme amount, and effect of MWCNT concentration were investigated. Afterward, in the characterization studies, some parameters such as linearity and reproducibility were determined. In the reproducibility experiment, an average value of 1.026μM, a standard deviation of ±0.03975, and a coefficient of variation of 3.8% were determined for a 1-μM dopamine concentration (n=15). Determination of dopamine was carried out in drug samples by the developed biosensor.

Viscosity and thermal conductivity of dispersions of gum arabic capped MWCNT in water: Influence of MWCNT concentration and temperature

Experiments were carried out on the measurement of viscosity and thermal conductivity of multi-walled carbon nanotubes (MWCNT)-water nanofluids prepared using gum arabic as dispersant. The influence of temperature (28–60°C), MWCNT concentration (0.14–0.24vol%) on viscosity and effective thermal conductivity has been investigated. Our results on the effect of MWCNT concentration on relative viscosity and thermal conductivity ratio are in qualitative agreement with those reported in literature. Thermal conductivity ratios increase strongly with temperature, especially above 45°C. Relative viscosities too increased with temperature above 45°C at relatively higher MWCNT concentration indicating the potential role of Brownian motion.

Optimization, characterization and nanofiltration properties test of MWNTs/polyester thin film nanocomposite membrane

MWNTs/polyester thin film nanocomposite (TFN) membranes were prepared through an improved process by interfacial polymerization of triethanolamine (TEOA) and trimesoyl chloride (TMC) on the polysulfone (PSf) supporting membrane in the presence of multi-walled carbon nanotubes (MWNTs). The effect of MWNTs concentration and surfactant species in the aqueous phase as well as the reaction time of interfacial polymerization on the membrane properties were investigated. The water permeability increased as the MWNTs concentration in aqueous phase increased up to 0.5mg/mL, reaching a maximum which was nearly double that of the thin film membrane without MWNTs, while the membrane rejection kept increasing dramatically. Compared with cationic (CTAB) and non-ionic (Triton X-100) surfactants, anionic (SDS) surfactant was more suitable for the preparation of TFN membrane. The reaction time determined the extent of interfacial polymerization and the integrality of surface skin layer. Furthermore, the nanofiltration properties of the MWNTs/polyester TFN membrane were tested by examining the separation performance of different feed solutions, feed concentrations, feed pHs at 0.6MPa operating pressure. Additionally, the MWNTs/polyester TFN membrane exhibited a good long-term stability.

Behavior of mixed multi-walled carbon nanotube/P3HT monolayer at the air/water interface

The sidewall structure of multi-walled carbon nanotubes (MWNTs) was successfully functionalized with poly(3-hexylthiophene) (P3HT) by a non-covalent bond method. P3HT plays an important role in dispersing MWNTs, and assists them to have a stable existence at the air/water interface. The behavior of mixed MWNT/P3HT monolayer at the air/water interface was investigated after obtaining a homogeneously dispersed solution. The effect of MWNT concentration on the mixed MWNT/P3HT monolayer was investigated using the pressure–area ( π– A) isotherm, relaxation curve and transmission electron microscopy (TEM). The mixed MWNT/P3HT monolayer was transferred onto a solid substrate using the Langmuir–Blodgett (LB) technique with horizontal or vertical deposition. The multilayer film was delicately fabricated by repeated deposition of the ultra-thin film. Scanning electron microscopy (SEM) images revealed non-uniformity in morphology of the ultra-thin MWNT/P3HT films. The absorption intensity at 250 nm by UV/vis spectroscopy illustrates that a uniform formation of mixed MWNT/P3HT monolayer into multilayer film was successfully obtained by horizontal deposition. The current–voltage characteristic of the ultra-thin MWNT/P3HT film shows that the current increases linearly with the increasing voltage, which indicates that MWNT/P3HT film forms an ohmic contact with gold. And, the electric current was estimated to be mainly contributed by MWNTs.