Influence Of Multi-walled Carbon Nanotubes Research Articles

The influence of multi-walled carbon nanotube doping on liquid crystalline phase transitions of a smectogen octylcyanobiphenyl: A high-resolution birefringence study

High-resolution optical birefringence measurements are reported on the weakly first order nematic-isotropic (N–I) and the continuous nematic-smectic A (N–Sm A) phase transitions in smectic liquid crystal 8CB (octylcyanobiphenyl) doped with both pristine multi-walled carbon nanotubes (p-MWCNTs) and carboxyl group (-COOH) functionalized MWCNTs (f-MWCNTs). It has been observed that the inclusion of MWCNTs substantially decreases both the N–I and the N–Sm A transition temperatures compared to 8CB host while the order of the transitions remains the same being the I–N weakly first-order and the N-SmA continuous for all 8CB-MWCNT composites regardless of the surface functionalization. The optical birefringence data have been used to probe the temperature behavior of the nematic order parameter S(T) in the vicinity of both the N–I and the N–Sm A transitions. Sufficiently far away from the Sm A phase, the average value of the critical exponent β characterizing the limiting behavior of S(T) near the N–I transition was found to be 0.245±0.002 This value of β seems to be in accord with the tricritical nature (TCH) of the N–I transition. Thus, concluded is the fact that the nature of the N–I transition of nanomaterial-based composites dispersed in liquid crystals remains tricritical up to at least the reported dopant contents and within the experimental resolution. The pre-transitional smectic behavior has also been noted to continue up to 4.3K on average above TNA for all 8CB-MWCNT composites. From the detailed inspection of S(T) data in the immediate vicintiy of the N–Sm A transition TNA, we have then obtained the upper limits for a possible latent heat ΔHNA across TNA for all 8CB-MWCNT composites. A slight change in ΔHNA has been observed due to the inclusion of MWCNTs as compared to 8CB host. By exploiting the fact that the temperature derivative of the order parameter S(T) near TNA exhibits the same power law divergence as the specific heat capacity, we have also extracted the effective critical exponent α values characterizing the critical fluctuations near the N-SmA transition for all 8CB-MWCNT composites. From both α and ΔHNA values, we have concluded that the nematic and smectic fluctuations remain essentially bulk-like for both 8CB-p-MWCNT and 8CB-f-MWCNT composites and thus the fact that the coupling between the N and the Sm A order parameters for all composites are comparable to that of 8CB host has been documented.

Microstructure and transport properties of multiwall carbon nanotube-reinforced barium zirconium titanate ceramics

The influence of multiwall carbon nanotubes (MWCNTs) reinforced on microstructures and their transport properties on pure and cerium-substituted barium zirconium titanate (BZT) ceramics are reported in this study. The MWCNTs were prepared by a low-temperature sonochemical/hydrothermal method using dichloromethane as a carbon source. These MWCNTs were mixed with the as-prepared ceramic powders before heat treatment to obtain a reinforced product. The scanning electron micrographs reveal the successful incorporation of carbon nanotubes in BZT ceramics. The temperature-dependent direct current (dc)-resistivity was less for MWCNT-reinforced ceramics in contrast to that of pure ceramics. The decrease in the dc resistivity was due to the superior electrical behaviour of MWCNTs, which act as a connector between ceramic grains. The Seebeck coefficient of cerium-substituted-BZT improved after reinforcing the MWCNTs.

Rheological properties of silicon oil-based magnetic fluid with magnetic nanoparticles (MNPs)-multiwalled carbon nanotube (MWNT)

In order to research the influence of multiwalled carbon nanotube (MWNT) on the rheological properties of magnetic fluid, silicon oil-based magnetic fluid with or without MWNT was prepared in the present investigation. Magnetic nanoparticles (MNPs) were synthesized by chemical coprecipitation with a certain amount of MWNT (0, 0.5 wt%). Then, Siliane coupling agents N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was used to modify the MNPs. The morphologies, microstructures and magnetic properties of the particles were characterized by transmission electron microscopy, fourier transform infrared spectroscopy and vibrating sample magnetometer. The effect of MWNT on rheological properties was investigated by the rotational rheometer, such as viscosity-temperature, viscosity-magnetism. Therefore, the results showed that the addition of MWNT significantly increases the viscosity of the magnetic fluid, and the viscosity increases with the magnetic field strength and decreases with increasing temperature. In addition, the shear stress increases with increasing shear rate, while the viscosity decreases with increasing shear rate. The rheological properties of magnetic fluid with or without MWNT are consistent.

Parametric analysis of delamination in GFRP composite profiles by performing rotary ultrasonic drilling approach: Experimental and statistical study

Application of glass fiber reinforced polymers (GFRP) has been appreciably increased in recent decades because of their admirable properties. Thus, various investigations are focused in machinability of GFRPs. Delamination is one of the major damages in drilling of GFRPs. Rotary ultrasonic drilling (RUD) is a state-of-the-art drilling operation that has been noticeably considered in composites machining industry. In this paper, delamination of GFRPs in RUD process is examined. To reach the goal, appropriate ultrasonic system was established and using a HSS tool, the experiments were carried out. Then, the influence of multi-walled carbon nanotube (MWCNT) addition, thermal fatigue and drilling parameters on delamination were investigated. Additionally, statistical analysis was performed. The results showed that the delamination quality can be well optimized by increase of the cutting velocity. It was also established that thermal fatigue condition results in delamination deterioration. In contrary, addition of nanoparticles enhances the delamination state.

Modeling the thermomechanical behaviors of shape memory polymers and their nanocomposites by a network transition theory

Nanocomposites based on a shape memory polymer matrix are emerging smart materials of great application potential due to their high deformability and good shape memory performance as well as decent mechanical properties. In the paper, a detailed theoretical study on the thermoviscoelastic behaviors and shape memory effects of multiwall carbon nanotubes (MWCNT) reinforced epoxy nanocomposites is presented. Different from the traditional shape memory cycle procedure, both the loading and memory processes in the study are programmed below the glass transition temperature, which is so-called cold deformation. A novel network transition constitutive model incorporated with a micro-mechanics model to determine the effective properties of the nanocomposites is proposed to study the underlying stress relaxation and shape memory mechanisms. The involved parameters are determined from standard thermomechanical experiments. Then we implement the model into Mathematica to predict the thermomechanical behaviors of both the neat and filled shape memory polymers subjected to different programming conditions, and the simulation results show good agreement with the experimental results. Moreover, the shape memory properties of the material as well as the influence of MWCNT on the material behavior are discussed in detail.

Thermal and Physical and Mechanical Properties of Polysulfone Composites with Carbon Nanotubes

The influence of multiwalled carbon nanotubes (MWNTs) on the thermal and physical and mechanical properties of polysulfone (PSU) nanocomposites is studied in this work. It is found that adding MWNTs (up to 5 wt %) to the compounds with PSU leads to an insignificant increase in the tensile modulus and a growth in the dynamic modulus of PSU/MWNTs at room temperature. Thermal and thermo-oxidative degradation of PSU/MWNTs nanocomposites is studied via TGA. The influence of addition of MWNTs on the formation and high-temperature stabilization of char residue under the conditions of thermo-oxidative degradation of PSU/MWNTs nanocomposites is found.

Assessing the Damage Tolerance of Out of Autoclave Manufactured Carbon Fibre Reinforced Polymers Modified with Multi-Walled Carbon Nanotubes.

The present study aims to investigate the influence of multi-walled carbon nanotubes (MWCNTs) on the damage tolerance after impact (CAI) of the development of Out of Autoclave (OoA) carbon fibre reinforced polymer (CFRP) laminates. The introduction of MWCNTs into the structure of CFRPs has been succeeded by adding carbon nanotube-enriched sizing agent for the pre-treatment of the fibre preform and using an in-house developed methodology that can be easily scaled up. The modified CFRPs laminates with 1.5 wt.% MWCNTs were subjected to low velocity impact at three impact energy levels (8, 15 and 30 J) and directly compared with the unmodified laminates. In terms of the CFRPs impact performance, compressive strength of nanomodified composites was improved for all energy levels compared to the reference material. The test results obtained from C-scan analysis of nano-modified specimens showed that the delamination area after the impact is mainly reduced, without the degradation of compressive strength and stiffness, indicating a potential improvement of damage tolerance compared to the reference material. SEM analysis of fracture surfaces revealed the additional energy dissipation mechanisms; pulled-out carbon nanotubes which is the main reason for the improved damage tolerance of the multifunctional composites.

Influence of multi-walled carbon nanotubes reinforcements on hardness and abrasion behaviour of porous Al-matrix composite processed by cold pressing and sintering

Carbon nanotubes (CNTs) are normally used as reinforcements in metallic matrix composites due to their ultrahigh elastic modulus and ultrahigh strength combined with low weight. In the present study, porous Al matrix composites were fabricated using different concentrations (0.1, 0.25, 0.5, 1 and 2 wt%) of multi-walled carbon nanotubes (MWCNTs) in pure aluminum by ultrasonic mixing, cold pressing and sintering. The microstructures were analyzed by optical microscopy, scanning electron microscopy (SEM) and Raman spectroscopy. Vickers hardness was performed in order to check the effect of the MWCNTs on the strength of the composite. Also, abrasion tests were carried out in order to qualitatively check the correlation with hardness measurements. It was found a good correlation between both properties and it was evidenced the optimized value of MWCNTs is 0.25 wt% for this type of porous composite processing. Above this concentration, hardness and abrasion resistance tend to decrease due to processing difficulty.

Simultaneous effect of nanoparticles and surfactant on emulsion liquid membrane: Swelling, breakage and mean drop size

In this study, the effect of multi-walled carbon nanotubes (MWCNTs) and Span-85 as a surfactant on drops breakup and coalescence rates of emulsion liquid membrane (ELM) due to hydrodynamic parameters was investigated which was not reported before. A single stage horizontal mixer-settler extractor with two 4-pitched blade turbine impellers with 45° inclined blades on one shaft was employed. The influences of MWCNTs, Span-85 and both of them at the same time on membrane swelling and breakage were studied in batch mode and dispersion Sauter mean diameter (D32) was compared to pure system for continuous mode experiments. Results indicated that simultaneous presence of MWCNTs and surfactant enhanced the ELM stability and the membrane swelling and breakage decreased about 46% and 63%, respectively. Also, it has the most influence on drop size compared to the presence of Span-85 and MWCNTs alone, respectively. Presence of MWCNTs and Span-85 at the same time caused to reduction in enhancing rate of D32 with dispersed phase volume fraction about 65.5%. Additionally, decreasing rate of D32 with impeller agitation speed diminished about 1.4%. Furthermore, in order to predict a mean drop size for all systems (with and without inorganic particles), a new modified correlation was proposed for the first time where the surfactant and nanoparticles concentrations were introduced as new independent parameters.

Pressure-sensitive polymer nanocomposites: Carbon nanofiber-reinforced MWCNT-coated PMMA microbeads

ABSTRACTA unique, thermoplastic polyurethane (TPU)-based, pressure-sensitive nanocomposites were prepared by the solution mixing method. Poly (methyl methacrylate) (PMMA) microbeads (10µm) were coated with multiwall carbon nanotubes (MWCNT) and dispersed in TPU matrix dissolved in tetrahydrofuran. 1, 2, and 5 wt. % of carbon nanofiber (CNF) were also added to the TPU matrix. The influence of MWCNT coated PMMA-microbeads along with different CNF contents on the pressure sensing properties were studied. Electrical and thermal conductivities were measured at different external loads. The prepared nanocomposites showed repeatable and reliable electric response with increasing external load and are suitable as pressure sensors.

The Research of the Effect of Single-Walled Carbon Nanotubes on the Properties of Epichlorohydrin Rubber

The development of frost-resistant elastomeric materials with high performance characteristics remains one of the topical issues. Solving this issue will significantly improve the reliability of machines and mechanisms operating under extremely low temperatures. The influence of multi-walled carbon nanotubes on the performance properties of epichlorohydrin rubber was investigated. This rubber of unique frost resistance has low glass transition temperature (Tg = -60 °C).

Comparison of the accumulation and metabolite of fluoxetine in zebrafish larva under different environmental conditions with or without carbon nanotubes

Few studies have focused on the influence of environmental conditions on the bioavailability of pollutants interacted with nanomaterials in organisms. In this study, we primarily compared the influence of multiwalled carbon nanotubes (MWCNTs) on the bioavailability of fluoxetine in zebrafish (Danio rerio) larva under different environmental conditions: natural organic matter (NOM) and salinity. The results showed that fluoxetine accumulated in the larvae and then transformed into the metabolite norfluoxetine, with the metabolic rates from 2.8 to 3.5. Following co-exposure to MWCNTs, the accumulation of fluoxetine and norfluoxetine were further enhanced, suggesting a superior carrier of MWCNTs for fluoxetine, especially the functional MWCNTs. The consistent increase in the fluoxetine and norfluoxetine accumulation highlights the bioavailability of absorbed fluoxetine on MWCNTs in zebrafish larvae. The presence of NOM promoted the accumulation of fluoxetine and norfluoxetine in zebrafish, but alleviated the carrier effects of MWCNTs, acting as a natural antidote. Salinity negatively influenced the bioavailability of fluoxetine in the larvae, and further reversed the enhancements caused by MWCNTs. These findings provide a new insight into the influence of environmental conditions on the interactions between nanomaterials and pollutants in organisms.

Influence of Multiwalled Carbon Nanotubes as Additives in Biomass-Derived Carbons for Supercapacitor Applications.

Glucose-derived carbon/carbon nanotube (CNT) hybrid materials were prepared by hydrothermal carbonization of glucose in the presence of CNTs and subsequent carbonization, physical activation, or chemical activation. The proportion of CNTs added during the hydrothermal polymerization of glucose was varied to ascertain the optimum dose to maximize the performance of the carbon hybrids in supercapacitor applications. Both the thermal treatment applied and the addition of CNTs lead to changes in the textural and chemical properties of the activated carbons. It was observed that samples bearing CNTs exhibit higher number of nucleation centers for glucose oligomers to polymerize, and consequently, the behavior of the hydrothermal carbon toward activation differs according to the activating agent employed. Moreover, the initial chemical speciation dominated by acidic groups shifts to more basic functionalities (quinones and carbonyl groups) with the addition of CNTs. The effect of the different physicochemical properties of the prepared carbons on their electrochemical behavior was evaluated. The addition of 2 wt % of CNTs and subsequent chemical activation leads to electrode materials yielding 206 F g-1 and 78% of capacitance retention up to 0.8 V and 20 A g-1 and high rate cyclability (97% after 5000 cycles). The outstanding performance is ascribed to the high surface area, narrow mesopores, and phenol/carbonyl surface functionalities, which enhance molecular diffusion, the amount of stored energy, and electronic transportation, respectively.

Dynamic properties of elastomer composites filled with multiwalled carbon nanotubes

The paper studies the influence of multiwalled carbon nanotubes (MWCN) on vulcanizing and dynamic properties under shear and oscillating load. It was found that, despite the lack of preliminary preparation of MWCN, when their concentration increase the dynamic properties also increase under an oscillating load in highly elastic state. Thus, it is possible to use MWCN producing elastomer materials with improved properties.

Accumulation, metabolite and active defence system responses of fluoxetine in zebrafish embryos: Influence of multiwalled carbon nanotubes with different functional groups

Studies on the bioavailability of organic contaminants adsorbed to nanomaterials are increasing. In this study, we investigated the interaction between fluoxetine (FLX) and three multiwalled carbon nanotubes (MWCNTs) with different functional groups in zebrafish (Danio rerio) embryos, focusing on the FLX accumulation, the formation of the metabolite norfluoxetine (NFLX), and the active defence system responses. The accumulation of FLX in zebrafish was intensified by MWCNTs (46–99%), which simultaneously facilitated the formation of the metabolite NFLX by 23–167%. The consistent enhancement revealed that the absorbed FLX is bioavailable in zebrafish. Moreover, the coexisting MWCNTs further promoted the influences of FLX on the active defence system in zebrafish (e.g. antioxidant and metabolic function), eliciting the defence function. The influences of MWCNTs on the bioavailability of FLX in zebrafish could be ordered as OH-MWCNTs > COOH-MWCNTs > pristine MWCNTs. The release of FLX from MWCNTs in biofluids may partially contribute to these significant alterations. In particular, MWCNTs themselves may also modulate the bioavailability of FLX in zebrafish by downregulating the gene expression of membrane ATP-binding cassette transporter (abcb4). These findings demonstrated that MWCNTs increased the bioavailability of FLX in zebrafish, especially the functionalized MWCNTs. The production of metabolites may be a useful bio-endpoint to evaluate the bioavailability of adsorbed contaminants on nanomaterials.

Influence of multi-walled carbon nanotube (MWCNT) concentration on the thermo-mechanical reliability properties of solderable anisotropic conductive adhesives (SACAs)

In the present work, the influence of multi-walled carbon nanotube (MWCNT) concentration on the thermo-mechanical reliability properties of carbon nanotube (CNT)-filled solderable anisotropic conductive adhesives (SACAs) containing low-melting-point-alloy (LMPA) fillers was investigated. To measure the reliability-related properties of SACA assemblies, six types of SACAs with different MWCNT concentrations (from 0 to 2 wt%) were formulated, and two types of reliability tests, thermal shock (TS) and high-temperature and high-humidity (HTHH) tests, were conducted on these samples. All of the CNT-filled SACA assemblies with different MWCNT concentrations showed proper and stable electrical reliability during each aging test, due to the molten LMPA fillers forming a metallurgical interconnection between the corresponding metallization regions. Although the mechanical strength of the CNT-filled SACA joints degraded after aging tests due to excessive intermetallic compound (IMC) layer growth, the CNT-filled SACAs with an MWCNT concentration below 0.1 wt% exhibited better mechanical reliability properties than those of SACAs without MWCNTs due to the initially achieved high bonding strength of the SACA joints, enabled by the reinforcing effects of the MWCNTs within the polymer composites.

Wear behavior of silica and alumina-based nanocomposites reinforced with multi walled carbon nanotubes and graphene nanoplatelets

Spark plasma sintering (SPS) technique has been employed to fabricate silica (SiO2) and alumina (Al2O3) based nanocomposites having multiwalled carbon nanotubes (MWCNTs) and exfoliated graphite nanoplatelets (xGnPs) as reinforcement phase. The influence of MWCNTs and xGnPs on the wear behavior of the nanocomposites is analyzed. SiO2-MWCNT, SiO2-xGnP nanocomposites having 0.5, 3 and 5 vol% and Al2O3-MWCNT, Al2O3-xGnP nanocomposites having 0.2, 0.8, 3 and 5 vol% of the respective nanofiller were developed. SiO2-based nanocomposites were fabricated at 1350 °C under a pressure of 40 MPa whereas Al2O3-based nanocomposites were prepared at 1450 °C under a pressure of 50 MPa. Experimental results indicate that the wear behavior of various SiO2 and Al2O3-based nanocomposites improves with the introduction of carbonaceous nanofillers like MWCNTs and xGnPs. With the addition of these nanofillers, a continuous supply of graphitic reinforcement phase at the ceramic interface provided a better lubrication to the reinforced nanocomposites, which was not found in the case of monolithic SiO2 or Al2O3 samples. Both MWCNTs and xGnPs effectively withstand the applied stress during the wear test owing to their structural morphology once subjected to the wear strain. A remarkably varied wear behavior of both SiO2 and Al2O3 based nanocomposites was observed. SiO2 based nanocomposites depict narrower wear tracks with high wear rates whereas Al2O3 based nanocomposites were found to depict broader wear tracks with low wear rates.

Tensile properties of nanoprepreg/nanostitched 3D carbon/epoxy MWCNTs composites

Abstract The tensile strength and failure of multilayered stitched carbon/epoxy multiwall carbon nanotube prepreg composites were investigated. Stitching, nano and, both stitching and nano slightly decreased the tensile strength and modulus of stitched and stitched/nano composites. The degradation of tensile properties in using para-aramid stitching yarn was slightly significant compared to polyacrylonitrile carbon stitching yarn due to stitching fiber properties. Prepreg woven pattern did not influence the tensile properties of all stitched and stitched/nano composites. Moreover, the influence of multiwall carbon nanotube on the base/nano and stitched/nano structures was partly inconsistent. Tensile load in stitched/nano composites made severe matrix and warp and filling directional multiple fiber breakages. Nevertheless, delamination areas were arrested by stitching fibers. Brittle tensile breakages and filament pull-out in the stitched and stitched/nano composites were identified.

Lipid accumulation in multi-walled carbon nanotube-exposed HepG2 cells: Possible role of lipophagy pathway

Nanoparticle (NP) exposure might promote hepatic steatosis, but relatively few studies investigated the influence of multi-walled carbon nanotubes (MWCNTs) on lipid accumulation in hepatocytes in vitro. This study investigated lipid accumulation and the possible role of lipophagy (autophagic degradation of lipid droplets) in MWCNT-exposed HepG2 cells. Pristine (XFM19) and carboxylated MWCNTs (XFM21) were internalized, accompanying cytotoxicity, lysosomal destabilization, and intracellular reactive oxygen species (ROS) production. Compared with XFM21, XFM19 promoted lipid accumulation in HepG2 cells more effectively, which was further enhanced by pre-incubation with autophagy inhibitor NH4Cl. In addition, MWCNTs increased the expression of lipophagy genes PLIN2 and BECN1 but decreased that of ATG7. The expression of endoplasmic reticulum (ER) stress regulators, namely DDIT3, HSPA5, and XBP-1s, was also altered in MWCNT exposed HepG2 cells. Combined, these results suggested that MWCNT exposure might promote lipid accumulation in hepatocytes probably through the modulation of lipophagy pathway.

Surface characteristics and erosion phenomena in WEDM of alumina composites

ABSTRACTReinforcing the ceramic materials with a conducting filler allows the net electrical properties to increase. This makes the composites machinable by electrical discharge process. Present work identifies the influence of multi-walled carbon nanotubes (MWCNT) as conducting fillers toward the machined surface profile. Alumina composites with 5 and 10 vol. % MWCNTs are fabricated and machined by wire electrical discharge machining process. The spalling effect is found to be more dominant at lower MWCNT concentrations in the composites. Cracks, porosity, and oxidization of the surface materials are the main defects observed during the machining process. Also, a more intense cracks and porous behavior is observed at lower concentration of MWCNT (5 vol. %). A closer analysis of machined surface edges yielded some phenomena of mechanical erosion and chipping due to physical contact. This situation is brought forward by low electrical conductivity and high brittleness of the composites. The Energy Dispersive X-Ray (EDX) analysis confers toward actual dissociation and melting of the carbon nanotubes even at low concentration of MWCNTs (5 vol. %) though not readily visible.