Effect Of Multi-walled Carbon Nanotube Content Research Articles

Effects of MWCNTs content and dry density on hydro-structural characteristics of bentonite during drying and wetting

Bentonite has been an essential component of geosynthetic clay liners due to its low hydraulic conductivity, which has been used as a barrier against hazardous pollutants in landfills. During the drying and wetting processes caused by high temperatures and leachate in landfills, the hydro-structural characteristics of bentonite vary as the moisture content change. This article investigates the effect of dry density and multi-walled carbon nanotubes (MWCNTs) content on the soil shrinkage characteristic curve (SSCC), the soil free-swelling characteristic curve (SFSCC), the soil water characteristic curve (SWCC), and microstructure of bentonite during the drying and wetting processes. Experimental results indicate that the addition of MWCNTs can slow down the volume variation of bentonite at the normal shrinkage stage and at the initial swelling stage and improve the water retention capacity in the low suction range. Meanwhile, reducing bentonite’s dry density can increase the void ratio during drying, decrease the void ratio during wetting, and improve the water retention capacity in the low suction range. Dry density and MWCNTs content both have no influence on the SSCC at the residual shrinkage stage and the zero shrinkage stage, the SFSCC at the residual swelling stage, and the SWCC at the high suction range.

Fabrication of electrically conductive poly(styrene-b-ethylene-ran-butylene-b-styrene)/multi-walled carbon nanotubes composite fiber and its application in ultra-stretchable strain sensor

Although flexible polymer composites based strain sensors have been widely studied, it is still a challenge to obtain flexible strain sensors with large working range, high sensitivity and reliable stability. In this research, a flexible strain sensor based on poly(styrene-b-ethylene-ran-butylene-b-styrene) (SEBS)/multi-walled carbon nanotubes (MWCNTs) composite fiber was prepared through the wet spinning method. In particular, the effects of MWCNTs content and aspect ratio (L/D) on the morphology, and mechanical, electrical and electromechanical properties of the composite fiber were studied. The results showed that with the increase of MWCNTs content, the tensile strength and elongation at break of the composite fiber decreased, while the electrical conductivity and the strain sensing range increased. For the same MWCNTs content, the composite fiber filled with MWCNTs of the lowest L/D ratio (1.25/15) showed the highest tensile strength and elongation at break; whereas the composite fiber filled with MWCNTs of the highest L/D ratio (20/15) showed the highest electrical conductivity, strain sensing range (0–506%) and sensitivity (gauge factor of 58.274 at 0%–275% strain, and of 197.944 at 275%–506% strain). The fabricated composite fiber could be formed into a knitted fabric and had the ability of detecting various human motions.

Effect of MWCNT content on the mechanical and piezoelectric properties of PVDF nanofibers

In this study, the mechanical properties and morphology of aligned and random polyvinylidene fluoride (PVDF) fibers as well as the morphology and mechanical, piezoelectric, and thermal properties of PVDF fibers with different multi-walled carbon nanotubes (MWCNT) contents were analyzed. Although electrospun piezoelectric PVDF-based nanofibers have been extensively studied for application in wearable devices, they do not have sufficient flexibility and strength for practical application. Therefore, in this study, the effects of various experimental parameters, such as MWCNT content and fiber orientation, on the mechanical and piezoelectric properties of PVDF nanofibers were investigated in depth. Scanning electron microscopy analysis revealed that the average diameter of the PVDF nanofibers decreased with an increase in degree of orientation, while transmission electron microscopy analysis revealed the uniform dispersion of MWCNTs in the PVDF nanofibers. The PVDF nanofibers containing 0.008 wt% MWCNTs exhibited an excellent tensile strength. Furthermore, Fourier transform infrared spectroscopy analysis revealed that the β-phase fraction increased with increasing MWCNT content. The thermal stability of the nanofibers increased with an increase in β-phase fraction, as evidenced by the increase in melting and initial decomposition temperatures and decrease in weight loss determined by differential scanning calorimetry and thermogravimetric analysis.

Effect of MWCNT content and thickness of photoanode on microcracks in QDSCs

Multi-walled carbon nanotubes (MWCNTs) were introduced into titanium dioxide (TiO2) photoanode films in quantum dot sensitized solar cells (QDSCs) to modify the microcracks structure that produced during the sintering process. The effect of different mass fractions (0%, 0.01%, 0.05%, 0.1% and 0.3%) of MWCNTs and photoanode film thickness on the performance of QDSCs was investigated. BET test verified that MWCNTs after acid treatment possess a higher specific surface area. Above-mentioned photoanodes were sensitized with CdS/ZnS quantum dots (QDs) and then assembled to the QDSC sample with polysulfide electrolytes and CuS counter electrodes. The results showed that the cell with 0.05 wt% MWCNTs photoanode in 11.60 μm thickness exhibited the optimum photoelectric performance and its power conversion efficiency (PCE) increased by 73.3% compared with bare TiO2 photoanode QDSCs. The results of sensitized photoanodes microstructure characterization, electrochemical impedance (EIS) and current–voltage (J-V) curves were combined to investigate the synergetic effect of MWCNT mass fraction and photoanode film thickness on the photovoltaic performance of different QDSCs quantitatively.

Effects of multiwall carbon nanotubes on dielectric and mechanical properties of CaCu3Ti4O12 composite

This work reports the synthesis of calcium copper titanate (CaCu3Ti4O12)/multiwall carbon nanotubes (MWCNT) composites using ultrasonic technique followed by sintering in a high vacuum furnace. The effect of MWCNT content (0.05, 0.1, 0.15, and 0.2 wt%) on the structural, dielectric, and mechanical properties of CaCu3Ti4O12 (abbreviated as CCTO) were investigated by TEM, XRD, FTIR, FESEM-EDAX, dielectric measurement, as well as tensile strength and flexural strength tests. XRD patterns revealed that the MWCNT loading did not affect the phase structure; however, the average crystallite size (D) was reduced from 60.88 nm to 40.79 nm. The samples had porous structures and the porosity reduced from 45.57% to 40.73% with MWCNT loading. The dielectric and mechanical properties of CCTO were enhanced with an increase in MWCNT loading. An important observation was that the CCTO mixed with 0.2 wt% MWCNT exhibited the highest dielectric permittivity (εr = 27,768) and the lowest dielectric loss (tan δ = 0.52) at 1 kHz. With the addition of 0.2 wt% MWCNT, the values of load, tensile, and flexural strength increased to 10.38 kN, 101.88 MPa, and 275.07 MPa, respectively, due to improvement in densification. These outcomes have values for the fabrication of CCTO and the optimization of its performance for electronic devices such as capacitors and antennas.

Effect of MWCNT content on thermal and shape memory properties of epoxy nanocomposites as material for morphing wing skin

In the present study, a shape memory epoxy polymer (SMEP) system was prepared from commercially available EPON 826 and NGDE, and then, 0.5%, 1.0% and 1.5% mass percentage of multi-walled carbon nanotubes (MWCNTs) were incorporated into it so as to prepare nanocomposites. The inclusion of the nanofiller into the SMEP system was expected to enhance its properties. Then, experimental analyses were conducted to study the effect of incorporating different amounts of MWCNTs on the thermal properties of the obtained nanocomposites, namely dynamic mechanical analysis, thermogravimetric analysis (TGA) and shape memory cyclic testing. It was found that the increasing content of MWCNTs in the SMEP system decreased the glass transition temperature of the developed nanocomposites (SMEPCs). TGA results indicated that the incorporation of MWCNTs into the SMEP decreased its thermal stability. The authors explained these results by the lack of interaction between the MWCNTs and the epoxy matrix. In consideration of the use of the SMEP for morphing applications, the increment in MWCNT content was found to improve the shape recovery properties of the SMEP. Thus, the study demonstrates that the incorporation of a MWCNT nanofiller can help enhance the properties of the SMEP system and overcome its limitations, revealing the high potential of the developed shape memory composite materials to be used for various industrial applications.

Effect of MWCNT content on conductivity and mechanical and wear properties of copper foam/resin composite

Multi-walled carbon nanotube (MWCNT) and carbon fiber and flaky graphite reinforced copper foam/furan resin composite for a novel sliding contact material was fabricated using an acid purify and ultrasonic dispersion technology, followed by a mold pressing process. The microstructure, electrical resistivity, impact strength and current-carrying friction performances of the composites were measured to investigate the effect of the different MWCNT contents. The results showed that the MWCNTs had a good dispersion state in the composite and the percolation threshold was approximate 0.074–0.185 vol%. As addition of the MWCNTs, the impact strength and wear resistance of the composites could be raised by 45% and 22%, respectively.

Effect of MWCNT content on the mechanical and strain-sensing performance of Thermoplastic Polyurethane composite fibers

Stretchable conductive fibers have attracted significant attention due to their ability to be directly woven into or stitched onto fabrics, making them ideal for use in the design of integrated wearable strain sensors. Here, we report on a highly stretchable multi-walled carbon nanotube (MWCNT)/Thermoplastic Polyurethane (TPU) fiber produced via a wet spinning process. The effects of MWCNT content and alignment on the structural, mechanical, electrical and strain-sensing properties of the composite fibers were investigated. The highest conductivity (6.77 S cm−1), tensile strength (28 MPa) and maximum elongation at break (565%) were obtained by controlling the MWCNT content. Gauge factor (GF) values were also affected by the content and MWCNT alignment in the composite fibers, as these parameters determine the change in the effective contact area and number of conductive paths available during stretching. The well-aligned MWCNT/TPU fiber showed a high GF value of 5200. Wearable strain sensors capable of obtaining real-time mechanical feedback for various human motion detections with different GFs and working strain ranges could be realized by controlling the MWCNT concentrations in the TPU matrix.

Microstructure and Properties of Nb/Nb5Si3 Composites Strengthened with Multiwalled Carbon Nanotubes by SPS

Multiwalled carbon nanotubes (MWCNTs) were modified noncovalently with cetyltrimethylammonium bromide. The Nb/Nb5Si3 in situ composite material that was strengthened with MWCNTs was prepared by SPS. The effect of MWCNT content on the microstructure and properties of Nb/Nb5Si3 in situ composites was investigated. The results showed that the composites consisted of Nb, α-Nb5Si3 and β-Nb5Si3 phases. With the addition of over 2 wt% MWCNT, a new Nb4C3 phase was formed in the composites. The properties of the Nb/Nb5Si3 in situ composites were affected by MWCNT addition. The relative density, Vickers hardness and fracture toughness increased with increasing MWCNT addition. When the MWCNT addition was 2 wt%, the relative density and Vickers hardness reached a maximum and increased by ~ 1.4% and ~ 18%, respectively (relative to 0 wt% MWCNT addition). When the MWCNT content exceeded 2 wt%, the relative density and the Vickers hardness decreased. However, the fracture toughness of the Nb/Nb5Si3 composites with 3 wt% MWCNTs reached a maximum (an increase of ~ 68% relative to 0 wt% MWCNT addition). Scanning electron micrographs of the fractography showed brittle cleavage and partial intercrystalline composite fracture. The composite toughening mechanisms arose mainly because of MWCNT removal and bridging.

The effects of agglomerate on the piezoresistivity of conductive carbon nanotube/polyvinylidene fluoride composites

Conductive polymer composites are prepared with a polyvinylidene fluoride (PVDF) matrix and multiwalled carbon nanotube (MWCNT) as filler. The mechanical properties, electrical conductivity and piezoresistivity of the composites are investigated as a function of MWCNT volume fraction. An optimal combination of ductility and piezoresistivity is found in the composite slightly above the electrical percolation threshold, showing a maximum fracture strain ∼ 4 times higher than the pure PVDF samples, as well as an outstanding sensitivity of piezoresistive response. Increasing further the MWCNT volume fraction leads to deterioration of both ductility and piezoresistivity. The effects of MWCNT content on piezoresistivity and fracture strain can be understood based on the microstructure observations. In particular, by incorporating two characteristic microstructural features identified in the materials, i.e., the filler random distribution and the filler agglomerate, into a simple statistical network model, the experimental measurements of piezoresistivity can be successfully fitted and understood in a semi-quantitative manner.

Detection of illegal dyes in foods using a polyethersulfone/multi-walled carbon nanotubes composite membrane as a cleanup method

In this paper, a polyethersulfone (PES)/multi-walled carbon nanotubes (MWCNTs) composite membrane was prepared using phase inversion. The surface morphology and internal structure of the membrane were observed by scanning electron microscopy (SEM). The effects of MWCNTs content on various aspects of membrane performance such as porosity, water flux, and antifouling characteristics were investigated. Results showed that proper addition of MWCNTs would improve the properties of the membrane. MWCNTs had a strong adsorption capacity for industrial dyes and the composite membrane could be used as an effective method to identify and clean up illegal dyes in foods. In addition, this new method for identifying dyes is rapid: the cleanup procedure in the determination of illegal dyes in foods by the composite membrane was shortened to 30 min or less compared to 6–8 h for traditional methods.

Tensile and Morphological Properties of Microcellular Polymeric Nanocomposite Foams Reinforced with Multi-walled Carbon Nanotubes

Polyamide 6 (PA6) is used in many applications due to its advantages and improving its properties seems essential. For this purpose in the present study, PA6 was melt compounded with various multi-walled carbon nanotubes (MWCNTs) contents and then was foamed using Azodi carbon amide (ACA) as blowing agent under different injection molding conditions. Morphological properties were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests. The results demonstrated that an appropriate distribution of MWCNTs was observed in polymeric matrix and 0.85, 0.94 and 1 A increase in distance between walls of CNTs was observed. Also, the SEM results illustrated that microcellular structure was achieved in all samples. The results illuminated that mean cell size was improved about 34% in samples containing 1 wt% MWCNT. The tensile properties of samples were investigated and the effect of MWCNTs content was studied on specific tensile and yield strengths. The results indicated that specific tensile strength and yield strength were significantly increased almost 164% and 147% by addition of 1 wt% of MWCNTs, respectively.

The effect of MWCNT content on electropolymerization of PPy film and electromechanical behavior of PPy electrode-based soft actuators

This study investigates the effects of multi-walled carbon nanotubes (MWCNTs) content on the electropolymerization potential of polypyrrole (PPy) on both surfaces of carbon nanoparticle/MWCNT (CN/M)-coated Nafion membranes and on the electrical, electrochemical and electromechanical properties of PPy- electrode based soft actuators. SEM analysis revealed that the surface morphology of actuators changes considerably by altering the MWCNT content and the most porous PPy films formed in actuator comprising of 25wt% MWCNT. The electrochemical characteristics of the prepared actuators were compared in terms of double layer capacitance (Cdl), pseudo capacitance (CF) and ionic conductivity (σ). The capacitive nature of the prepared actuators was followed by waveform analysis of applied voltage and output current. Cdl and σ increased by increasing the MWCNT content up to 25wt% and afterward decreased considerably, while a reverse trend was observed for CF. The electrochemical impedance spectroscopy (EIS) measurements confirmed that this sample had the highest surface roughness. These data were in good agreement with the data obtained from water uptake (WUP) and ion exchange capacity (IEC) measurements. The electro-chemo-mechanical performances of the actuators were followed by studying the maximum tip displacement and IV curves. The largest tip displacement was obtained in actuators comprising of 25wt% MWCNT which showed to have the highest capacitive characteristic (243.52 mF. cm−2). The specific electro-mechanical energy efficiency (1.18) and the maximum tip displacement (25mm) of these metal-free actuators were 18% and 9% higher than that considered for Pt-based actuators, respectively. This strategy is therefore of considerable interest for increasing the applicability of low cost carbon-based soft actuators in medicine and robotics.

Strain sensing in polymer/carbon nanotube composites by electrical resistance measurement

In this work multiwall carbon nanotubes (MWCNTs) dispersed in a polymer matrix have been used for strain sensing of the resulting nanocomposite under tensile loading. This was achieved by measuring the relative electrical resistance change (ΔR/R0) in conductive polyvinylidenefluoride (PVDF)/MWCNTs nanocomposites prepared by melt-mixing with varying filler content from 0.5wt.% to 8wt.%. Two main parameters were systematically studied. The PVDF/MWCNTs mixing procedure that results in a successful MWCNTs dispersion, and the effect of MWCNTs content on material’s sensing behaviour. The samples were subjected to tensile loading and the longitudinal strain was monitored together with the longitudinal electrical resistance. The results showed that MWCNTs dispersed in insulating PVDF matrix have the potential to be used as a sensitive network to monitor the strain levels in polymer/carbon nanotube nanocomposites as the deformation level of each sample was being reflected by the resistance changes.

MWCNTs decorated Mn0.8Zn0.2Fe2O4: Synthesis, characterization and compositional effect on the structural and magnetic properties

Abstract In the present study, Mn0.8Zn0.2Fe2O4 nanoparticles, synthesized from spent Zn–C batteries extract, were successfully used for decoration of multi-walled carbon nanotubes (MWCNTs). This MWCNTs/Mn0.8Zn0.2Fe2O4 magnetic nano-composites were prepared by the addition of MWCNTs during the preparation of the entire ferrite using sucrose combustion method. The effect of MWCNTs content (0–70%) on the structural, morphological and magnetic properties of entire ferrite was investigated and discussed. The results showed that high purity Mn0.8Zn0.2Fe2O4 nano-crystallites were completely decorated on the sidewalls of the MWCNTs up to 30% content and the decoration behavior, shape and density are dependent on the composition. The saturation magnetization was observed to decrease with increasing MWCNTs content while coercivity showed a particle size dependent behavior. The composition with 70% MWCNTs was examined as adsorbent for methylene blue dye (MB) from aqueous media based on its relatively high surface area and the capability of removing the nano-composite after adsorption process using normal magnet. The nano-composite showed a very high adsorption capacity and the kinetic as well as the thermodynamics of adsorption/removal process were investigated and discussed. Repeated testing showed the applicability of the nano-composite for the removal of MB from aqueous solution frequently with acceptable efficiencies.

Temperature dependent microwave attenuation behavior for carbon-nanotube/silica composites

SiO2-matrix composites filled with 2, 5 and 10wt.% multiwalled carbon nanotubes (MWCNTs) were prepared to evaluate the dielectric properties and microwave attenuation performances over the full X-Band (8.2–12.4GHz) at a wide temperature ranging from 100 to 500°C. On the basis of the conductivity induced by the structure of the MWCNT, the transport of migrating and hopping electrons in the MWCNT micro-current network has been discussed, and the effects of MWCNT content and temperature on the electronic transport and conductivity have been investigated. These effects also have great influences on the dielectric properties, electromagnetic wave propagating and microwave attenuation performances of the composites. The behavior of electromagnetic interference (EMI) shielding and microwave absorption provide the technical direction for the design of microwave attenuation materials and also indicate that CNT-based composites could be promising candidates for microwave attenuation application.

Shape memory properties of multi-walled carbon nanotube/polyurethane composites prepared by in situ polymerization

A high strength multi-walled carbon nanotube (MWCNT)/shape memory polyurethane composite (SMPC) was prepared by in situ polymerization. The effect of MWCNT content and its dispersion on the microstructure, mechanical, and shape memory property of the SMPC were studied by scanning electron microscopy, universal testing machine, and dynamic mechanical analysis. The results showed that MWCNTs can be well dispersed in the composites and the composites with homogeneous dispersion of MWCNTs exhibited superior mechanical properties for MWCNTs supplied cross-link netpoints in the composites. And the materials with 97 % of recovery ratios (Rr) and 94 % of fixing ratios (Rf) indicated that this SMPC is a prominent potential candidate for smart actuator.

Electrospun poly (lactic-co-glycolic acid)/ multiwalled carbon nanotubes composite scaffolds for guided bone tissue regeneration

A series of poly (lactic-co-glycolic acid) (PLGA)/multiwalled carbon nanotubes (MWNTs) composite scaffolds was prepared by electrospinning for tissue engineering applications. The effect of MWNTs content on the structure and properties of composite scaffolds was characterized by scanning electron microscopy (SEM), X-ray diffractrometry (XRD), thermogravimetric analysis (TGA), and universal testing machine (UTM). The attachment ability and viability of rat bone marrow-derived mesenchymal stem cells (BMSCs) in the presence of the scaffolds were also investigated. Morphological characterization showed that the addition of different amounts of MWNTs increased the average fiber diameter; for instance, from 717 nm (neat PLGA) to 2193 nm at 1.0% MWNTs. Thermal characterization showed that the incorporation of MWNTs into the PLGA matrix increased the thermal stability of the composite scaffolds. The analysis of mechanical properties of the PLGA/MWNTs composites revealed great improvement over pure PLGA scaffold. The attachment and proliferation of BMSCs were significantly increased in the PLGA/MWNTs scaffolds compared with the PLGA control. Therefore, the PLGA/MWNTs composite scaffolds fabricated by electrospinning may be potentially useful in tissue engineering applications, particularly as scaffolds for bone tissue regeneration.

라텍스 기법으로 제조한 폴리스티렌/다중벽 탄소나노튜브 나노복합재료의 나노튜브 길이가 유변학적 특성에 미치는 영향

라텍스 블렌딩 기법을 이용하여 폴리스티렌(PS)/다중벽 탄소나노튜브(MWCNT) 나노복합재료를 제조하여 나노튜브 길이에 따른 나노복합재료의 유변학적 특성을 고찰하였다. 나노복합재료 제조에 사용된 단분산 PS 입자는 무유화제 유화중합으로 제조하였고 NWCNT는 불순물 제거와 분산성 향상을 위해 표면개질 과정을 거친 후 사용하였다. 최종적인 나노복합재료는 단분산 PS 입자와 개질한 MWCNT를 초음파 교반조에서 분산시킨 후 동결건조 과정을 거쳐 제조하였다. 나노복합재료의 MWCNT 함량과 나노튜브 길이에 따른 유변학적 특성은 소진폭 진동 전단유동을 부과시켜 평가하였다. 본 연구에서 고찰한 PS/MWCNT 나노복합재료는 MWCNT의 함량이 증가할수록, 나노튜브 길이가 길수록 유변물성 향상 효과가 뚜렷하였다. 이는 MWCNT 함량이 증가할수록 나노복합재료의 유변학적 특성이 액체적 특성에서 점차 고체적 특성으로 변화하기 때문이며. 나노튜브 길이가 길수록 네트워크 구조를 달성하는 임계 농도가 직아 지지 때문인 것으로 판단된다.

Solar photocatalytic decomposition of two azo dyes on multi-walled carbon nanotubes (MWCNTs)/TiO2 composites

Multi-walled carbon nanotubes (MWCNTs)/TiO2 composite photocatalysts with high photoactivity were prepared by sol-gel process and further characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), and UV-vis absorption spectra. Compared to pure TiO2, the combination of MWCNTs with titania could cause a significant absorption shift toward the visible region. The photocatalytic performances of the MWCNTs/TiO2 composite catalysts were evaluated for the decomposition of Reactive light yellow K-6G (K-6G) and Mordant black 7 (MB 7) azo dyes solution under solar light irradiation. The results showed that the addition of MWCNTs enhanced the adsorption and photocatalytic activity of TiO2 for the degradation of azo dyes K-6G and MB 7. The effect of MWCNTs content, catalyst dosage, pH, and initial dye concentration were examined as operational parameters. The kinetics of photocatalytic degradation of two dyes was found to follow a pseudo-first-order rate law. The photocatalyst was used for seven cycles with photocatalytic degradation efficiency still higher than 98%. A plausible mechanism is also proposed and discussed on the basis of experimental results.