Dispersion Of Multi-walled Carbon Nanotubes Research Articles

Role of Solvent Polarity on Dispersion Quality and Stability of Functionalized Carbon Nanotubes

Dispersion of carbon nanotubes (CNT) in solvents and/or polymers is essential to reach the full potential of the CNTs in nanocomposite materials. Dispersion of CNTs is especially challenging due to the van-der-Waals attraction forces between the CNTs, which let them tend to re-bundle and/or re-aggregate. This paper presents a brief analysis of the quality and stability of functionalized multiwalled carbon nanotubes (fMWCNT) dispersion on polar solvents. A comparative study of functionalized CNT dispersion in water, methyl, and alcohol-based organic solvents has been carried out and the dispersion has been characterized by UV-VIS spectroscopy, electrochemical characterization such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Visual analysis of the dispersion has been investigated for up to 14 days to assess the dispersion’s stability. Based on the material characterization, it was observed that the degree of affinity fMWCNT with -COOH group highly depends on the polarity of the solvent, where the higher the polarity, the better the interaction of fMWCNT with solvents.

Synthesis of a Composite Based on Humic Acid Tuned to Sorbed Copper Ion

We obtained modified humic acid-based cross-linked composite pre-tuned to the sorbed copper ion. The composite synthesis had three stages. At first, we obtained prepolymerization complex using humic acids iso-lated from Shubarkol deposit oxidized coals and multi-walled carbon nanotubes (MWCNTs) with template (CuSO4). We used ultrasonic activation for uniform dispersion of multi-walled carbon nanotubes. Second stage comprised copolymerization in the presence of amine and cross-linker; here the prepolymerization composite complex with the template was fixed in certain nodes of polymer network. At the third stage, acid hydrolysis destroyed the bonds of the template with the composite macromolecules, the template was re-moved, and imprints complementary to the template in shape, size, and functionality were formed and re-tained “molecular memory”. Such tuning forms adsorption centers in the polymer network of the composite, which can repeatedly and highly specifically interact with the template, and highly selectively extract target molecules from solution, leading to significant increase in sorbent capacity. The reaction was controlled by direct and back titration, and added amine, which was determined using Elementar Unicube elemental ana-lyzer. The crosslinked composite can be used as a selective sorbent tuned to a specific metal ion.

Improving the dispersion of multiwalled carbon nanotube in polypropylene using controlled extensional flow

The use of controlled extension flows associated with processing with predominant shear flows can bring gains in the dispersive capacity of nanofillers during the processing of nanocomposites. In this work, we use a controlled flow device coupled to the matrix of a single-screw extruder to process PP matrix composites containing 0.5% and 2.5% (v/v) of MWCNT. The nanocomposites were evaluated by optical microscopy and oscillatory rheological analysis. The clusters size analysis showed that in PP/0.5MWCNT-el, 70.5% of all its clusters were below 1µm2 while its analog processed without the extensional flow showed 59.8% of its clusters below this value. The rheological analysis allowed to verify that the compositions processed with the presence of the extensional flow have their crossover frequencies shifted to lower values, that is, longer relaxation times corroborating that improved degrees of dispersion were achieved.

Helically aligned fused carbon hollow nanospheres with chiral discrimination ability.

While the functions of carbon materials with precisely controlled nanostructures have been reported in many studies, their chiral discriminating abilities have not been reported yet. Herein, chiral discrimination is achieved using helical carbon materials devoid of chiral attachments. A Fe3O4 nanoparticle template with ethyl cellulose (carbon source) is self-assembled on dispersed multiwalled carbon nanotubes (MWCNTs) fixed in a lamellar structure, with helical nanoparticle alignment induced by the addition of a binaphthyl derivative. Carbonization followed by template removal produces helically aligned fused carbon hollow nanospheres (CHNSs) with no chiral molecules left. Helicity is confirmed using vacuum-ultraviolet circular dichroism spectroscopy. Chiral discrimination, as revealed by the electrochemical reactions of binaphthol and a chiral ferrocene derivative in aqueous and nonaqueous electrolytes, respectively, is attributable to the chiral space formed between the CHNS and MWCNT surfaces.

Multiwalled carbon nanotubes reinforced flexible blend nanocomposites membranes for pervaporation separation of aromatic-aliphatic mixtures

Multiwalled carbon nanotubes (MWCNT) reinforced NR-NBR blend nanocomposite membranes were prepared and potentially employed for the pervaporation separation of aliphatic – aromatic mixtures. For a 50 wt% benzene feed, the blend nanocomposite membranes had a total flux of 1.265 kgm−2h−1 and separation factor of 1.59 at room temperature. The blend membranes exhibited aromatic selectivity for the separation of aromatic – aliphatic mixtures. 2 phr MWCNT/blend nanocomposite membranes exhibited similar trend for the separation of 10 wt% feed toluene mixture. Trasmission electron microscopy (TEM) images of the blend nanocomposites revealed the well dispersion and distribution of MWCNT in the polymer matrix. The well dispersed MWCNT/blend membranes selectively separate aromatic components from aliphatic – aromatic mixtures.

Evaluation of MWCNT Particles-Reinforced Magnesium Composite for Mechanical and Catalytic Applications.

Aluminum, magnesium, and copper materials must have increased mechanical strength with enhanced wear and corrosion resistance. Substantial research focused on reinforcing hard particles into low-strength materials using stir casting or powder metallurgy. This work is intended to develop the magnesium hybrid matrix with the dispersion of boron carbide (B4C) and multiwall carbon nanotubes (MWCNTs). Hybrid magnesium composites are prepared, although the powder metallurgy route considers different process parameters. Statistical analysis such as Taguchi L16 orthogonal array is involved in this work. It is used to find the magnesium hybrid samples' minimum and maximum wear, corrosion, and microhardness levels. Powder metallurgy parameters are B4C (3%, 6%, 9%, and 12%), MWCNT (0.2%, 0.4%, 0.6%, and 0.8%), ball milling (1, 2, 3, and 4 h), and sintering (3, 4, 5, and 6 h). The ball milling parameters are extremely influenced in the wear test analysis. Minimum wear losses are obtained as 0.008 g by influencing the 4 h ball milling process. Similarly, 3 h of sintering time offered a minimum corrosion rate of 0.00078 mm/yr. In microhardness analysis, the percentage of MWCNTs is highly implicated in narrow hardness resulting in the hardness value of 181. The hardness value is recorded using 0.2% MWCNTs in the magnesium alloy AZ80.

DIC analysis of nano concrete using functionalized and dispersed carbon nanotubes

Digital Image Correlation (DIC) method is considered as a powerful tool to capture material behavior for improved precision. This paper deals with effect of dispersion and functionalization of multiwall carbon nanotubes (MWCNTs) on fracture mechanics properties such as fracture energy and stress intensity factor. Fracture mechanics properties were found out using DIC technique and also by experimentally using a clip gauge and linear variable differential transformers (LVDT). The experiment was conducted under crack mouth opening displacement (CMOD) controlled manner and rate of loading was set as 0.0005 mm/s. MWCNTs were taken in a proportion of 0.1%, 0.2%, 0.3%, 0.4% and 0.5% by weight of cement and Nano silica and Nano alumina were considered as 3% and 2% by weight of cement respectively. The compressive strength is increased by 45.28% and tensile strength and flexural strength increased by108.26% and 53.249% respectively. It was seen that displacements measured by DIC and by experimentally were in the same line and also Load vs CMOD graphs plotted with both the methods are having similar behavior. Size effect was considered for preparation of all the specimens and by the results it can be seen that all specimens follow Bazant’s Size effect law.

Powder metallurgy and hardness of the Ll-10Mg alloy reinforced with carbon nanotubes

In this work, the multi-walled carbon nanotubes (MWCNTs) were purified with an acid treatment and subsequently dispersed using ultrasound and a nonionic surfactant solution of ethoxylated lauric alcohol 7 moles of ethylene oxide (E7E). Then, carbon nanotubes (CNTs) were used as a reinforcement phase (0.4 wt.% and 0.8 wt.%) in the Al- 10Mg alloy. The high-energy ball milling was employed for the nanocomposites processing, and the resulting powders consolidate by uniaxial pressure. Measurements of Vickers microhardness, nanohardness, displacement, and Young's modulus were carried out on the compacts. The samples were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FT-IR), and Raman spectroscopy (RS). Good dispersion of MWCNTs was achieved using 0.5 mg/ml of the E7E surfactant. The CNTs were dispersed in the Al-10Mg matrix using 0.25 h of milling. After powders compaction, the Al-10Mg/0.4MWCNTs nanocomposite presented a microhardness of 190 HV, nanohardness of 3.5 GPa, and Young's modulus 116 GPa.

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

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

Interfacial, electrical, and mechanical properties of MWCNT in polyurethane nanocomposite coating via 2D electrical resistance mapping for aircraft topcoat

Interfacial, electrical, and mechanical properties of polyurethane (PU)-type aircraft topcoat layers for LSP (Lightning Strike Protection) was evaluated by 2-D electrical resistance (ER) mapping with different oxidation times. Multi-wall carbon nanotubes (MWCNT) were treated using hydrogen peroxide to improve dispersion. Mechanical property of MWCNT/PU topcoat was determined via thin film tensile test, and oxidation degree was determined using TGA and EDS. Static contact angle measurements were used to evaluate work of adhesion between MWCNT and PU coating layer. Interfacial adhesion between MWCNT and PU coating layer was obtained via pull-out test and both results were consistent with different MWCNT oxidation times. Electrical properties of MWCNT/PU topcoats were evaluated by surface ER. Surface ER was the lowest at 5 days oxidation times. Higher tensile strength of MWCNT/PU topcoat could contribute to higher interfacial adhesion. Visualization was used to determine MWCNT dispersion and verified successfully using the color variation of 2D ER mapping.

Dynamic mechanical analysis, electrical properties and water sorption behaviour, of phenol formaldehyde nanocomposite reinforced with multiwalled carbon nanotubes

The goal of this research is to synthesise Phenol-formaldehyde nanocomposites containing pure multiwalled carbon nanotubes using an in-situ polymerisation process. The impact of filler loadings (MWCNT) with various weight percentages in the composite was explored in this research. The visco-elastic, electrical, morphological, and water sorption behaviour of the nanocomposites were investigated. The influence of MWCNT loading on the dynamic mechanical analysis, water uptake, electrical behaviour was examined. Using in-situ polymerisation, an effort was made to generate non agglomerated and homogenius dispersion of multiwalled carbon nanotubes (MWCNT) in the PF composite. The influence of MWCNT dispersion on the viscoelastic characteristics, electrical, morphological, and water sorption behaviour of PF-MWCNT nanocomposites has been thoroughly investigated. When compared to neat PF, lower filler loading (0.05 wt%, 0.08 wt percent) resulted in greater AC conductivity. According to DMA investigation of PF-MWCNT, 0.15 wt% has a greater storage modulus and 0.05 has a higher glass transition temperature. The addition of MWCNT has effectively reduced the water uptake of the entire nanocomposite.

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

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

Enhanced dielectric and thermal properties of thermoplastic polyurethane/multi-walled carbon nanotube composites

Thermoplastic polyurethane (TPU) composites embedded with multi-walled carbon nanotube (MWCNT) of different loadings as a filler were synthesized by melt mixing method. These composites were characterized by Fourier Transform infrared spectroscopy (FTIR) and X-Ray diffraction (XRD) technique. A considerable peak shift in FTIR was not seen, proving the absence of a chemical interaction between the matrix and the filler. The crystallinity of the composite almost doubled with that of neat as evidenced by XRD analysis. The morphological characterization of composites was done by scanning electron microscope (SEM) which proved the fine dispersion of MWCNT on TPU at lower loadings up to 3 w% while agglomeration started on further increase in the filler loadings. Dielectric studies of the composites showed a significant increase in dielectric properties which is due to the increased mobility of polymer chains. The ac conductivity of the composites also showed a gradual increase with an increase in filler loadings. Thermogravimetric analysis (TGA) revealed a considerable increase in the thermal stability of composites up to 3% MWCNT in comparison with neat.

Structural and Infrared Spectroscopy of Polyvinylpyrrolidone/Multi-walled Carbon Nanotubes Nanocomposite

In this work, polyvinylpyrrolidone (PVP)/ Multi-walled carbon nanotubes (MWCNTs) nanocomposites were prepared with two concentrations of MWCNTs by casting method. Morphological, structural characteristics and electrical properties were investigated. The state of MWCNTs dispersion in a PVP matrix was indicated by Field Effect-Scanning Electron Microscopy (FESEM) which showed a uniform dispersion of MWCNTs within the PVP matrix. X-ray Diffraction (XRD) indicate strong bonding of carbonyl groups of PVP composite chains with MWCNTs. Fourier transfer infrared (FTIR) studies shows characteristics of various stretching and bending vibration bands, as well as shifts in some band locations and intensity changes in others. Hall effect was studied to test the type of charge carriers which was shown to be P-type. The electrical conductivity was shown increased for the pure PVP and pure MWCNT from (2.047×10-5) (Ω.cm)-1 and (3.683×101) (Ω.cm)-1 to (2.51×102 and 2.36×102) (Ω.cm)-1for both concentrations of nanocomposites, which indicate the conductivity was enhancement by using the carbon nanotubes.

Influence of blending protocol on the mechanical, rheological, and electromagnetic properties of PC/ABS/ABS‐g‐MAH blend‐based MWCNT nanocomposites

AbstractPolycarbonate (PC)/acrylonitrile‐butadiene‐styrene copolymer (ABS) blend‐based multi‐wall carbon nanotubes (MWCNT) nanocomposites is an attractive alternative for the manufacture of electronics housing as it can have the mechanical and electromagnetic properties required for this application. The preferred location of MWCNT in PC/ABS blend is an important parameter to obtain better mechanical and electromagnetic properties. In this way, three different blending protocols (BP) were used to obtain PC/ABS/maleic anhydride‐grafted ABS (ABS‐g‐MAH) (85/10/5) blend‐based MWCNT nanocomposites with the addition of 0.5 and 1 wt% of MWCNT in a twin‐screw extruder. Specimens were evaluated by thermal (thermogravimetric analysis—TGA and differential scanning calorimetry—DSC), mechanical (Izod impact strength and tensile tests), dynamic mechanical analysis (DMA), electrical, and rheological properties, which were correlated with the nanocomposites morphology evaluated by high‐resolution scanning electron microscopy. The BP associated with the addition of a compatibilizer agent influenced the MWCNT distribution and location in the polymeric matrix. The one‐step extrusion process results in MWCNT mostly at the interface of the PC/ABS blend and agglomerates, leading to lower mechanical and thermal properties. The BP in which a PC/MWCNT masterbatch was first prepared and then diluted in ABS and ABS‐g‐MAH achieves the higher mechanical properties, increasing Young's modulus and the ultimate tensile strength. The third BP in which MWCNT was added in a second step in the blend already processed resulted in a homogeneous dispersion of MWCNT on both phases and a lower electrical resistivity.

Ultraviolet light crosslinked graphene/multi-walled carbon nanotube hybrid films for highly robust, efficient and flexible electrothermal heaters

Based on the Joule heat effect, graphene can transfer electrical into heat energy with fast response times and high efficiencies. Despite intensive researches, facile strategies for preparing polymer-based graphene electrothermal materials remain highly desirable. We herein report a strategy for preparing poly (tetra fluoroethylene) (PTFE)-supported high-performance hybrid electrothermal films from liquid-phase exfoliated graphene by combining with multi-walled carbon nanotubes (MWCNTs). The graphene and MWCNT dispersions can be obtained by sonicating graphite and MWCNTs, respectively, in chloroform with an ultraviolet (UV) light reactive dendritic polymer, HBPE@Py@Acryl, as stabilizer. Further, a series of PTFE-supported, UV cross-linked graphene/MWCNT hybrid films were successfully prepared from the dispersions by vacuum filtration and UV irradiation. It is found that the existence of MWCNTs in the films results in porous structure, making the hybrid films denser than the single graphene system. Meanwhile, the MWCNTs can effectively bridge graphene nanosheets to form perfect hybrid networks, jointly imparting the films with significantly enhanced electrothermal performance. In addition, the UV crosslinking of the HBPE@Py@Acryl adsorbed on the graphene and MWCNT surfaces makes the films exhibit excellent service stability. As an example, after being alternately folded 1800 times or scraped for 90 cycles, the film with 20% MWCNTs remains exhibiting stable, well controllable electrothermal performance. This research provides a guideline for producing high-performance polymer-based graphene electrothermal materials, potentially useful in wearable devices and intelligent actuators, from liquid-phase exfoliated graphene through simple process.

Impact of MWCNT in CFRP composite during end milling process

ABSTRACT Incorporation of nanofillers upto a certain weight percentage in polymeric matrix has been established to enhance the performance of composites. Machining is an integral part of any manufacturing process and the effect of machining on nanocomposites has been a subject of various studies. The present study investigates the influence of multi-walled carbon nanotube (MWCNT), spindle speed (SS), and feed rate (FR), on end milling performances, such as, delamination factor (DF) and surface roughness (Ra) by using the TOPSIS methodology. The investigation has showed that incorporation of MWCNTs in the CFRP composites optimizes the machining performances. The investigation, using multi-objective TOPSIS-based analysis of variance approach, showed that SS is the most governing factor, followed by FR and MWCNT wt%, which influence the overall performance of the composites. Field emission scanning electron microscope (FESEM) has been used to show the dispersion of MWCNT in the epoxy matrix. Improvisation on machining surface characteristics along with optimal performance parameters are accomplished successfully.

Models for sensing by nanowire networks: application to organic vapour detection by multiwall carbon nanotube—DNA films

Electronic sensors for volatile organic compounds have been prepared by drop-casting dispersions of multi-wall carbon nanotubes (MWCNTs) in aqueous solutions of λ-DNA onto Pt microband electrodes. The MWCNTs themselves show a metal-like temperature dependence of the conductance, but the conductance of DNA/MWCNT composites has an activated component that corresponds to inter-tube tunneling. The resistance of the composite was modelled by a series combination of a term linear in temperature for the nanotubes and a stretched exponential form for the inter-tube junctions. The resistance may increase or decrease with temperature according to the composition and may be tuned to be almost temperature-independent at 67% by mass of DNA. Upon exposure to organic vapours, the resistance of the composites increases and the time-dependence of this signal is consistent with diffusion of the vapour into the composite. The fractional change in resistance at steady-state provides an analytical signal with a linear calibration and the presence of DNA enhances the signal and adjusts the selectivity in favour of polar analytes. The temperature dependence of the signal is determined by the enthalpy of adsorption of the analyte in the inter-tube junctions and may be satisfactorily modelled using the Langmuir isotherm. Temperature and pressure-dependent studies indicate that neither charge injection by oxidation/reduction of the analyte nor condensation of analyte on the device is responsible for the signal. We suggest that the origin of the sensing response is an adsorption of the analyte in the inter-tube regions that modulates the tunneling barriers. This suggests a general route to tuning the selectivity of MWCNT gas sensors using non-conductive polymers of varying chemical functionality.

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.

Composite thin films based on multilayer carbon nanotubes and calcium phosphate with electrical conductive properties for bone tissue engineering

This work is aimed at developing of electrically conductive composite thin films based on calcium phosphates (CP) and multi-walled carbon nanotubes (MWCNT) for bone tissue engineering. A method based on the sputtering of an dispersion of CPs and MWCNTs on a substrate with subsequent exposure to a laser with different power values to form connected networks of nanotubes has been proposed. It is shown that the electrical conductivity of CP/MWCNT films reaches high values for dispersions with a MWCNT concentration of 1 mg/ml when exposed to laser radiation with a power of 2.1–3.0 W. It was found that ablation areas of CPs and MWCNTs as a result of exposure to a high-power laser are found in areas of the film with increased resistance.