Weight Ratio Of Multi-walled Carbon Nanotubes Research Articles

Effects of MWCNT and Sodium Dodecyl Sulfate (SDS) contents on the electrical conductivity and sensor properties of thermoplastic polyurethane nanosurfaces

Recently, strain sensors have significant areas of usage with their strain, stretching and wearable features for various applications such as personal health monitoring, joint movement detection, robotics, etc. To achieve this, various studies are conducted to optimize the production of MWCNT-based nanocomposites. In the present study, a total of 12 solutions were formulated by introducing Multi-Walled Carbon Nanotubes (MWCNT) and Sodium Dodecyl Sulfate (SDS) at different concentrations and ratios into the Thermoplastic Polyurethane (TPU) solution, and then nanocomposite surfaces were produced from these solutions through an electrospinning process. These samples were subjected to resistance changes due to elongation, gauge factor changes due to elongation to evaluate the sensor property and cycle tests to evaluate the sustainability of the sensor feature. According to the results, the best sensor properties were obtained in the samples with SDS added at a rate of 1/20 (MWCNT:SDS) for 0.3 MWCNT and 0.5 MWCNT; on the other hand 1/26 weight ratio of MWCNT:SDS for 0.7 MWCNT.

Smart wearable triboelectric nanogenerator for self-powered bioelectronics and therapeutics

With the development of Triboelectric Nanogenerators (TENGs), the field of energy harvesting has experienced a new era of revolution following the trend to configure innovative materials, design, integrated sensing and high triboelectric output. Here, we investigated the electricity-generation process of TENG by conducting its finite-element analysis using COMSOL Multiphysics software. Further, the effect of different weight concentrations (0%, 2%, 4%, 6%) of multi-walled carbon nanotubes (MWCNT) into the Polydimethylsiloxane (PDMS) matrix was investigated. It has enabled us to find the optimal weight ratio of MWCNT and increase surface charge density, thereby enhancing triboelectric performance for realising smart wearable triboelectric nanogenerators (SW-TENG). On the other hand, a novel dynamic test platform was developed for automated tapping on TENG for quantified performance analysis of SW-TENG. The results indicate that 4 wt% is the optimal weight ratio for fabrication of MWCNT-PDMS based TENG as it recorded the highest open circuit voltage of 195.4 V revealing ∼79% enhancement in triboelectric output as compared to pure PDMS based TENG. Furthermore, SW-TENG was integrated with a bridge rectifier and 10 μF capacitor in order to power bioelectric devices such as a digital thermometer and a pulse sensor. Besides serving as a power source, the SW-TENG shows innovative sensing capabilities for delivering self-powered rehabilitation therapy augmenting the next generation healthcare systems.

Wide-Range Flexible Capacitive Pressure Sensors Based on Dielectrics with Various Porosity.

Wide-range flexible pressure sensors are in difficulty in research while in demand in application. In this paper, a wide-range capacitive flexible pressure sensor is developed with the foaming agent ammonium bicarbonate (NH4HCO3). By controlling the concentration of NH4HCO3 doped in the polydimethylsiloxane (PDMS) and repeating the curing process, pressure-sensitive dielectrics with various porosity are fabricated to expand the detection range of the capacitive pressure sensor. The shape and the size of each dielectric is defined by the 3D printed mold. To improve the dielectric property of the dielectric, a 1% weight ratio of multi-walled carbon nanotubes (MWCNTs) are doped into PDMS liquid. Besides that, a 5% weight ratio of MWCNTs is dispersed into deionized water and then coated on the electrodes to improve the contact state between copper electrodes and the dielectric. The laminated dielectric layer and two electrodes are assembled and tested. In order to verify the effectiveness of this design, some reference devices are prepared, such as sensors based on the dielectric with uniform porosity and a sensor with common copper electrodes. According to the testing results of these sensors, it can be seen that the sensor based on the dielectric with various porosity has higher sensitivity and a wider pressure detection range, which can detect the pressure range from 0 kPa to 1200 kPa and is extended to 300 kPa compared with the dielectric with uniform porosity. Finally, the sensor is applied to the fingerprint, finger joint, and knee bending test. The results show that the sensor has the potential to be applied to human motion detection.

Flexible Piezoresistive Tactile Sensor Based on Polymeric Nanocomposites with Grid-Type Microstructure

Piezoresistive tactile sensors made using nanocomposite polymeric materials have been shown to possess good flexibility, electrical performance, and sensitivity. However, the sensing performance, especially in the low-pressure range, can be significantly improved by enabling uniform dispersion of the filler material and utilization of effective structural designs that improve the tactile sensing performance. In this study, a novel flexible piezoresistive tactile sensor with a grid-type microstructure was fabricated using polymer composites comprising multi-walled carbon nanotubes (MWCNTs) as the conductive filler and polydimethylsiloxane (PDMS) as the polymeric matrix. The research focused on improving the tactile sensor performance by enabling uniform dispersion of filler material and optimizing sensor design and structure. The doping weight ratio of MWCNTs in PDMS varied from 1 wt.% to 10 wt.% using the same grid structure-sensing layer (line width, line spacing, and thickness of 1 mm). The sensor with a 7 wt.% doping ratio had the most stable performance, with an observed sensitivity of 6.821 kPa−1 in the lower pressure range of 10–20 kPa and 0.029 kPa−1 in the saturation range of 30–200 kPa. Furthermore, the dimensions of the grid structure were optimized and the relationship between grid structure, sensitivity, and sensing range was correlated. The equation between pressure and resistance output was derived to validate the principle of piezoresistance. For the grid structure, dimensions with line width, line spacing, and thickness of 1, 1, and 0.5 mm were shown to have the most stable and improved response. The observed sensitivity was 0.2704 kPa−1 in the lower pressure range of 50–130 kPa and 0.0968 kPa−1 in the saturation range of 140–200 kPa. The piezoresistive response, which was mainly related to the quantum tunneling effect, can be optimized based on the dopant concentration and the grid microstructure. Furthermore, the tactile sensor showed a repeatable response, and the accuracy was not affected by temperature changes in the range of 10 to 40 °C and humidity variations from 50 to 80%. The maximum error fluctuation was about 5.6% with a response delay time of about 1.6 ms when cyclic loading tests were performed under a normal force of 1 N for 10,200 cycles. Consequently, the proposed tactile sensor shows practical feasibility for a wide range of wearable technologies and robotic applications such as touch detection and grasping.

Mechanical properties improvement of bi-directional functionally graded laminated MWCNT reinforced composite beams using an integrated tailoring–optimization approach

Many leading technologies are introduced to enhance mechanical structures’ capabilities. Promising materials are also explored, such as nanocomposites, functionally graded, and smart materials. This research discusses one of these encouraging proposals named Bi-Directional Functionally Graded Multi-Walled Carbon Nanotubes (MWCNT) Reinforced Composite (BDFG-CNTRC). Therefore, a simple cantilever beam consists of ten MWCNT/polymer layers is proposed. Each layer has its own different MWCNT weight ratio and axially grading to conduct Bi-directional property. It is assumed to contain 1% of MWCNT weight as a fixed reinforcement ratio. This assumption preserves beam constant weight. Consequently, a finite element model based on previous studies is modified to cope with the presented beam material and geometric properties. The obtained results are compared to published numerical and experimental optimized findings and have shown high accuracy. After that, a new tailoring–optimization approach is introduced and applied for the chosen beam. Significant improvements are obtained in beam mechanical properties and response. It is found that effective elastic modulus remarkably enhances by 114.93%. Fundamental natural frequency increases by 55.08%. Moreover, beam tip deflection reduces by 53.47%.

Properties of light weight multi walled carbon nano tubes (MWCNTs) nano-composites

The researchers are applying different methods to increase the performance of nanocomposites. There are some techniques that will used to increase the properties of epoxy resins for example attachment of functional groups to the carbon nanotubes, better dispersal techniques to disperse the nanofillers into the polymer matrices and so on. In this research, we made a comparative study on epoxy with different weight ratio of MWCNTs. Based on observation and experiment, developing an experimental relation between changes in different types of properties. For this purpose, a combination of epoxy resin (Araldite® LY 5052) and hardeners (Aradur® HY 5052) was dispersed into the matrix, and then the effect of this epoxy based matrix was investigated after dispersing p-MWCNTs and f-MWCNTs.

The alkaline synthesizing method for improved thermal characteristics of CNT/alumina nanocomposite

The multi-walled carbon nanotubes (MWCNTs) and Alumina (Al2O3) (CNT/Alumina) have been synthesized by two different simple methods including mechanical and chemical fabrication. The effect of the weight ratio of MWCNTs to Alumina on dispersion characteristic and thermal conductivity has been studied. To confirm that it is the success process, the morphological and structural investigations were carried out using transmission electron microscopy (TEM), Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), Raman spectroscopy. The whole results indicated that the chemical synthesized CNT/Al2O3 (c-CNT/Al2O3) were possessed good dispersion as compared to mechanical synthesized CNT/Al2O3 (m-CNT/Al2O3). However, for the dispersion stability, although c-CNT has higher value than m-CNT, m-CNT/Al2O3 were higher than c-CNT/Al2O3 for the nanofluid. The highest thermal conductivity enhancement was revealed when the weight ratio of (1:1) for the nanocomposite. The results were indicated that the synthesis methods were simple, environmentally-friendly and it has very effective characteristics than other chemical treatment.

Stabilization of the aqueous dispersion of carbon nanotubes using different approaches

This paper presents experimental investigations on aqueous dispersion of multi-walled carbon nanotubes (MWCNTs). Three experimental approaches are considered to improve MWCNTs dispersion; through functionalization of MWCNTs (1) with surfactants, (2) with oxidative acid treatment and (3) with metal decoration. The first approach investigated the dispersion stability of MWCNTs using different surfactants. In the second approach, surface of MWCNTs is functionalized through nitric acid treatment to facilitate the dispersion of MWCNTs. In the third approach, MWCNTs are decorated with silver nanoparticles and their dispersion behavior is investigated. In the experiments with surfactant addition, the ideal surfactant type and concentration are found as acacia gum at 1 surfactant:MWCNTs weight ratio, which yielded the highest zeta potential value of 26.7 mV. The second approach yielded an improved dispersion stability by visual observation of the fluid over a period of three months with no trace of sedimentation. Visual observation of the fluids prepared using silver-decorated MWCNTs showed a weak dispersion behavior. Thermal conductivity enhancement of the nanofluids at 0.1 wt% nanoparticle loading are calculated as 5.84% for silver-decorated MWCNT nanofluids, 8.14% for acid-functionalized MWCNT nanofluids and 8.85% for surfactant-functionalized MWCNT nanofluids. Functionalization with surfactant and oxidative acid treatment are found as the two useful methods for the stability and enhanced thermal conductivity of MWCNT dispersions.

Electromagnetic Properties Performance of MWCNTs/Polyester Composites in X-band

In this paper presents nano-composites based on polyester (PE) matrix with multi-walled carbon nanotubes (MWCNTs) as fillers have been developed for microwave absorbing materials. The MWCNTs/PE composite samples were fabricated with different weight ratio of MWCNTs (3 wt%, 5 wt%, and 10 wt%). The electromagnetic properties of different MWCNTs/PE composite have been determined by using rectangular waveguide technique and Agilent material measurement software. Moreover, the reflection loss (microwave absorption) of MWCNTs/PE composite have been calculated based on the basis of transmission line theory. The performance of electromagnetic properties and microwave absorption of MWCNTs/PE composite were analyzed in X-band frequency. The dielectric loss properties of the composite are increse with increasing in MWCNTs weight ratio. The microwave absorption results show that such 3 wt% MWCNTs/PE composites sample with 4 mm thickness has achieved less than -10 dB values (< 90 % microwave absorption) of reflection loss.

Fabrication of Carbon Nanotube Polymer Actuator Using Nanofiber Sheet

Carbon nanotube polymer actuators were developed using composite nanofiber sheets fabricated by multi-walled carbon nanotubes(MWCNTs) and poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). Nanofiber sheets were fabricated by electrospinning method. The effect of flow rate and polymer concentration on nanofiber formation were verified for optimum condition for fabricating nanofiber sheets. We examined the properties of MWCNT/PVDF-HFP nanofiber sheets, as follows. Electrical conductivity and mechanical strength increased as the MWCNT weight ratio increased. We fabricated carbon nanotube polymer actuators using MWCNT/PVDF-HFP nanofiber sheets and succeeded in operating of our actuators.

Fabrication and characterization of closed-cell aluminum foams with different contents of multi-walled carbon nanotubes

Closed-cell aluminum foams with different contents of multi-walled carbon nanotubes (MWCNTs) were fabricated by using modified melt foaming method. In order to effectively disperse MWCNTs, orthogonal tests were utilized to determine the optimal ball-milling parameters. The existence forms of MWCNTs in aluminum foams and the compressive properties of the foams were investigated. Considered from the dispersion degree and structural changes of MWCNTs, the optimal parameters were obtained, the parameters mainly referred to weight ratio of MWCNTs to aluminum powder, weight ratio of ball to powder, milling rate and milling time, respectively. The results showed that MWCNTs mainly existed in three forms: totally embedded in cell wall, partly embedded in cell wall and totally exposed on cell wall surface, respectively. The reasons were mainly due to the existence of defects and amorphous carbon on the surface of MWCNTs, which promoted the wettability between the aluminum matrix and MWCNTs. In addition, with the MWCNT content increasing, the yield strength, structural stiffness and energy absorption capacity of the foams increased first and then decreased. Meanwhile, under the present conditions the foams with MWCNT content of 0.5% possessed the optimal comprehensive mechanical properties and the reasons were discussed.

The electrical conductivity of carbon nanotube/carbon black/polypropylene composites prepared through multistage stretching extrusion

We reported the design of a grape-cluster-like conductive network in a polypropylene (PP) matrix, where oriented multi-walled carbon nanotubes (MWCNTs) served as branches and provided charge transport over large distances while grape-like carbon black (CB) aggregates enriched around MWCNTs and linked these conductive tubes through charge transport over small distances. The key for construction of this grape-cluster-like conductive network was the extension and orientation of MWCNTs, which was achieved in this work by multistage stretching extrusion with an assembly of laminating-multiplying elements (LMEs, which divide and recombine polymer melts). The highest efficient grape-cluster-like conductive network was obtained at a CB:MWCNT weight ratio of 6. The experimental results showed that this novel grape-cluster-like conductive network provided a low percolation threshold for PP/CB/MWCNT composites due to the synergistic effect of CB and oriented MWCNTs. When the combined CB and MWCNT content was about 6.9vol%, the electrical resistivity of PP/CB/MWCNT composites prepared by multistage stretching extrusion with 6 LMEs decreased to only 0.63Ωcm.