High Multi-walled Carbon Nanotubes Research Articles

Dielectric, low‐frequency noise and mechanical properties of hybrid carbon nanotubes/graphene nanoplatelets epoxy composites

AbstractThis study analyzes the electrical, microwave (26–37 GHz), low‐frequency (20 Hz–10 kHz) noise, and mechanical properties of epoxy hybrid composites filled with multi‐walled carbon nanotubes (MWCNT) and graphene nanoplatelets (GNP). The system's percolation threshold was around 0.25 vol.% MWCNT, while the electromagnetic properties were almost independent of GNP concentration. The composites are shown to be suitable for electromagnetic shielding in the 26–37 GHz range, with microwave absorption increasing as the total nanocarbon concentration rises. The electrical transport in these composites is governed by one‐dimensional Mott hopping at low temperatures (below 245 K) and redistribution effects above room temperature. The low‐frequency voltage noise spectra of the composites are predominant of the 1/f component, with noise spectral density proportional to Ub, where the exponent b is close to 2, indicating noise caused by resistance fluctuations. The optimal electromagnetic properties are near 0.5 vol.% MWCNT and 0.25 vol.% GNP concentrations. The tensile elastic modulus and yield strength showed the highest increases at 0.25/0.25 loading, with gains of 40.43% and 16.77%, respectively, compared to neat epoxy. Fracture toughness and energy release rate increased with adding 0.25 vol.% GNP, while Charpy impact strength improved with higher MWCNT loading.Highlights Percolation threshold in hybrid MWCNT/GNP composites is close to 0.25 vol.% MWCNT Low‐frequency voltage noise spectra of the composites are 1/f type

Conversion of municipal sewage sludge into biogenic multi-walled carbon nanotubes and hydrogen using X-Mo/MgO (X = Co, Fe, Ni) catalysts through pyrolysis-chemical vapor deposition process

Utilization of municipal sewage sludge as a feedstock for synthesizing biogenic multi-walled carbon nanotubes (MWCNTs) and recovering H2 via pyrolysis-chemical vapor deposition (CVD) was explored. The research centered on investigating the impact of X-Mo/MgO catalysts (X = Co, Fe, Ni, and X: Mo: MgO mass ratio of 3:1:6) on the conversion of pyrolysis gases from the sludge at the CVD temperatures of 600–––800 °C. The results demonstrate that the catalyst efficiency is enhanced when CO2 is captured from pyrolysis gas prior to the CVD reactor (here, with a calcium-based sorbent). The three X-Mo/MgO catalysts showed the highest MWCNT and H2 yields at 700 °C compared to other temperatures. The Co-Mo/MgO catalyst exhibited the highest MWCNT production (2.9 wt% per feedstock) and H2 yield (140.7 mL per g of sludge) at 700 °C. The higher yield could be related to the smaller size of the metal particles of the spent catalyst. Furthermore, Co-Mo/MgO at 700 °C grown MWCNTs had more uniform diameter distribution and larger BET surface area. Notably, the produced MWCNTs were doped by N and S heteroatoms due to the presence of these elements in the sludge and the doping extent could be managed by controlling the CVD temperature, opening the pathway for customization of MWCNT properties. The highest doping levels were observed for MWCNTs grown on Fe-Mo/MgO at 600 °C (N − 3.4 at% and S – 2.3 at%) by XPS. According to these results, the pyrolysis-CVD process could be a feasible technique for the conversion of municipal sewage sludge into valuable biogenic MWCNTs and H2. The use of Co-Mo/MgO and Ni-Mo/MgO catalysts exhibited some advantages (e.g., high MWCNTs and H2 yields) compared to Fe-Mo/MgO catalysts.

Coupled effect of MWCNTs concentration and induced pore structures on compressive performance and elastic modulus of ultra-high toughness cementitious composites: Experimental and theoretical studies

Due to the superior mechanical properties and electrical conductivity of multi-walled carbon nanotubes (MWCNTs), their integration into cementitious composites can improve compressive strength and self-sensing capabilities. However, balancing high mechanical strength with high conductivity is challenging as high MWCNT dosages can impede strength development. We addressed this by studying the effect of MWCNTs concentration (0–1.1 wt% of cementitious binders) and induced pore structures on the compressive performance and elastic modulus of ultra-high toughness cementitious composites (UHTCC), both experimentally and theoretically. It was found that as the MWCNTs concentration increased, the porosity continued to increase, while the compressive strength fluctuated. Two failure patterns were identified, i.e., quasi-brittle failure and ductile failure. Analysis showed MWCNTs could promote cement binder hydration, increasing matrix density but the strength development was curbed by increased porosity. A balance was achieved at 0.7 wt% MWCNTs. Further investigations using the Eshelby-Mori-Tanaka method discussed how MWCNT concentration, mechanical properties, distribution, porosity, and pore geometry influenced the elastic modulus. Ultimately, we developed a UHTCC-MWCNT composite with 1.1 wt% MWCNTs, which exhibited substantial improvements in compressive strength (44.85 MPa) and conductivity (9.78✕10−3 S/m), showing increases of 22.18 % and 18,132.6 % respectively, compared to the reference group.

MWCNTs dispersion adopting GA and its application towards copper tailings-based cementitious materials

Hydrophobic carbon nanotubes are hardly to disperse in water and prone to agglomerate when poured with Copper Tailing-Based Cementitious Material (CTCM). Multi-walled carbon nanotubes (MWCNTs) + Arabic Gum (GA) dispersions were prepared by a novel method of synergistic optimization of concentration, controlling low-frequency ultrasonic time and setting the ambient temperature with non-toxic anionic surfactant GA as surfactant. The results of UV–Vis spectroscopy showed that the high stability MWCNTs + GA dispersion with low aggregation area (< 1.2%) and low aggregation beam size (< 219 nm) have been prepared by using 1.7 mmol/l GA. The effects of highly stable MWCNTs dispersion on the mechanical properties, microstructure and durability of CTCM were studied. The 28 days compressive strength increased by 21.5%, and the flexural strength increased by 20.5%, almost reaching the mechanical level of the control group. The results of SEM, XRD and EDS showed that GA significantly enhanced the dispersion of MWCNT in aqueous solution at a suitable concentration (mass ratio of GA:CNTs = 1:1). The microstructure of the prepared CTCM by high stability MWCNTs dispersion was optimized obviously, and the mechanical properties and durability were improved significantly. This method solves the dual problem of MWCNTs not being fully dispersed in aqueous solution and being easily re-agglomerated in cementitious materials, as well as finding a breakthrough for the low cost and industrialization of tailings cement-based composite cementitious materials.

Synergistic effect of Mn2+ with unzipped carbon nanotubes on enhancement of mechanical properties of polyamide 66

Multi-walled carbon nanotubes (MWCNTs) are widely recognized for their exceptional mechanical properties and potential to reinforce composite materials. However, the requirement for high MWCNT concentration remains a challenge in achieving effective reinforcement. In this study, using unzipped multi-walled carbon nanotubes (uMWCNTs) and transition metal filler as a means to significantly enhance the mechanical properties of polyamide 66 (PA66) and incorporating 0.2% w/w of uMWCNTs-Mn as filler allowed us to increase PA66's tensile strength by over 74% and its Young's modulus by over 100%. The structural and functional integrity of uMWCNTs-Mn and PA66 matrix were investigated in detail. This work reveals that the enhancement of mechanical properties is mainly due to the interfacial interaction between uMWCNTs-Mn sheets and the PA66 matrix, the coupling effect of manganese ions, and increases the crystallinity and reduces the size of microcrystals. This work's findings provide a novel approach to the preparation of high-performance composites with low concentrations of carbon nanostructures, which holds significant implications for the development of advanced materials.

Synthesis of Multi Wall Carbon Nanotubes based Electronic Sensors for Internet of Things (IoT)

The Internet of Things (IoT) refers to advance devices other than computers that are connected to the Internet and can send and receive information. IoT is a new paradigm that has transformed traditional lifestyles into high-tech ones. It is the notion of a ubiquitous computer environment in which custom-sized electronics are effortlessly implanted into common things. Electronic sensors at the heart of the IoT detect physical/environmental occurrences, translate these measurements into electrical signals, and wirelessly transfer the data for remote computation. Indeed, the 5G communication and cloud computing stimulate the research in applications of carbon nanotubes in electronic devices. CNTs have demonstrated potential applications in electronics, biosensing, artificial intelligence and the Internet of ThingsIn present study, we report the synthesis of Multi Wall Carbon Nanotubes (MWCNTs) by Chemical Vapour Deposition (CVD) at 600C on Zinc Oxide (ZnO) catalyst coated silicon substrate by thermal evaporation technique. As-grown MWCNTs are characterized by Scanning Electron Microscope (SEM). High density growth of MWCNTs have been confirmed by SEM image. Catalyst nanoparticles play very important roles in the decomposition of the hydrocarbon source and to provide nucleation site for growth of MWCNTs. High MWCNT density is required for IoT-based sensors with high performance, sensitivity, selectivity, and distant sensing. Because IoT not only provides services but also creates massive amounts of data. Hence, this study would be helpful for the next generation 5G communication and cloud computing stimulate to enhance living style.

Unravelling the sensory capability of MWCNT-reinforced nanocomposites: Experimental and numerical investigations

Multifunctional nanocomposite strain sensors, especially those that contain dispersed multiwall carbon nanotubes (MWCNTs), are known to possess exceptional electrical conductivity. These nano-reinforced composites can be used for structural health monitoring. It is with this in mind that we focus our attention on calibrating the electromechanical behaviour of MWCNT-reinforced epoxy nanocomposites both numerically and experimentally. In particular, our main objective is to unravel the coupled electromechanical behaviour of the conducting composite prior to failure. In the numerical effort, we adopted the effective-medium homogenization and Mori-Tanaka method to account for tunnelling resistance and to predict the sensory capability of the newly developed composite. In the experimental effort, a conductive epoxy nanocomposite containing high quality MWCNTs randomly dispersed within liquid neat epoxy system was developed. The conducting domains of the developed nanocomposite were characterized using atomic force microscope (AFM) measurements. Electromechanical characterisation of the MWCNT-reinforced nanocomposites was also performed using controlled uniaxial tensile tests to evaluate its sensory capability against load. The results of our work reveal: (i) excellent agreement with the micromechanical model, and (ii) the dramatic influence of the concentration of the MWCNTs, their agglomeration and aggregation on the sensory sensitivity of the MWCNT-reinforced epoxy nanocomposite. Interestingly, an increase in the MWCNT filler loading led to a decrease in the sensory sensitivity of the nanocomposite as measured by uniaxial strain gauge factor. The work was further extended to highlight the sources of errors that could lead to erroneous results in developing and calibrating electrically conducting pathways in polymer nanocomposites.

Miniature vacuum sensor based on gas adsorptions from carbon nanotube field emitters

A mini-type vacuum sensor based upon current enhancement from gas adsorption for multi-walled carbon nanotube (MWNT) field emitters is developed. The current increase rates in low emission state are proportional to gas pressures in nitrogen, hydrogen, and mixed gas environments. The field emission energy distribution (FEED) measurement demonstrated the reductions of electron tunneling energy barriers in H2 and N2 ambiences. The first-principles simulation indicates that the energy barrier reduction, which is related to the surface energy well from nitrogen adsorption, is attributed to the sensing effect for nitrogen. Both experiments and first-principles simulation affirmed that the high MWNT crystallinity benefits the sensing performance. The miniature sensor in millimeter dimensions based on MWNT field emitter with simple diode configuration can operate in a wide vacuum range from 10−7 to 10−2 Pa. The sensor was assembled inside the X-ray tube to measure the in-situ device vacuum, showing great potentials for vacuum electronic device applications.

Assessing the electrical property of carbon nanotube reinforced oxide ceramic matrix composites produced by ceramic injection moulding

Owing to its remarkable properties, multiwalled carbon nanotubes (MWCNTs) are attracting the interest for realization of sensors. The potential of MWCNTs for high temperature sensing applications was investigated by integration within reinforced aluminium oxide ceramic composite. MWCNTs up to 2 wt% were mixed with reinforced aluminum oxide ceramic composite using solution mixing method to ensure good homogeneilty of the oxide ceramic composite powders. Specimens were realized using ceramic injection moulding process (CIM) followed by debinding and sintering procedures. The topography of specimens were examined using atomic force microscopy (AFM). Electrical measurements were also carried out. The results show good demouldability at high MWCNTs concentration and homogenous distribution of the MWCNTs within the oxide ceramic matrix. AFM images illustrate the reduction of surface roughness by increasing the MWCNTs content which demonstrates the role of MWCNTs to improve the fracture resistance of the oxide ceramic matrix composite. As well, the electrical resistance of the feedstocks were reduced sharply. After sintering process, the resistance range drops enormously from M Ω to reach 12.1 Ω at low MWCNTs content; which make them suitable to be as electrode with high temperature capability. The electrical resistance temperature dependency shows a negative temperature coefficient behaviour with negligible resistance change.

Fine-tuning the catalytic cracking-assisted synthesis of plastic-derived MWCNTs-supported metal oxides for methanol electrooxidation

• High performance MWCNTs-supported metal oxides have been successfully synthesized using plastics. • The combination between catalytic cracking process and catalytic chemical vapor deposition (CCVD) allows improving the efficiency of MWCNTs-supported metal oxides. • The FER zeolite is the efficient catalyst for catalytic cracking process, eventually enhancing the quality of MWCNTs-supported metal oxides. • MWCNTs-supported metal oxides exhibit outstanding properties in methanol electrooxidation. Multi-walled carbon nanotubes (MWCNTs) have been successfully fabricated using waste plastics via the two-stage process combining between catalytic cracking with the aid of an acid zeolite, and chemical vapor deposition (CVD) using transition metals supported on zeolites as catalysts. By fine-tuning the catalytic cracking process with an appropriate zeolite, the small carbon intermediates can be produced from starting plastics. Subsequently, transition metals supported on zeolites were used as catalytic templates in the CVD process to efficiently produce uniform structured and high qualified MWCNTs with a very high yield (96%) from cracked products. Interestingly, the fabricated materials exhibit the significantly improved electrocatalytic oxidation of methanol up to 8 to 14-fold advantage with respect to the one obtained by a traditional synthesis. These findings open up new opportunities to fine-tune the performance of synthesized CNTs from plastics in an electrocatalysis. The high performance CNTs-supported metals have been successfully fabricated using the catalytic cracking-assisted synthesis of waste plastics by two-stage process. By fine-tuning the appropriate catalytic cracking catalyst in the first stage to produce the facile hydrocarbons for the transformation towards CNTs in the second stage, the high performance CNTs has been obtained with the outstanding electrochemical properties for methanol electrooxidation.

Study on the effect of tailoring the hard copolymer polyurethane on the thermal, mechanical and electrical properties of hard copolymer polyurethane/multi-walled carbon nanotubes nanocomposites

This study focusses on the effect of the addition of multi-walled carbon nanotubes (MWCNTs) on the morphology and thermal, rheological and electrical properties of hard copolymer polyurethane (HCPU) using 1,5 pentane-diols as a chain extender, containing 85% of hard segment blocks. Step-growth polymerisation was used to synthesise a HCPU polymer matrix, followed by melt compounding to prepare the nanocomposites. SEM investigation of the neat HCPU structure and its nanocomposites indicated the uniform dispersion of MWCNTs within the polymer matrix; further TEM morphology investigation showed some agglomeration regions, attributed to the high MWCNT content (2 wt%). An XRD test confirmed a homogeneous distribution of MWCNTs by observing the remaining location of the highest peaks of MWCNTs and amorphous peaks of the HCPU matrix. Analysis of the melt rheology test results showed an improvement in complex viscosity combined with an increase in the G’ and G” of nanocomposites from those of pure HCPU due to the presence of MWCNTs. Finally, electrical conductivity of nanocomposites demonstrated a significant improvement in its value at high loading of MWCNTs from that of pure HCPU matrix.

Impedance Analysis and Noise Measurements on Multi Walled Carbon Nanotube Networks.

The electrical impedance characteristics of multi-walled carbon nanotube (MWCNTs) networks were studied as a function of CNT concentrations in the frequency range of 1 kHz–1 MHz. The novelty of this study is that the MWCNTs were not embedded in any polymer matrix and so the response of the device to electrical measurements are attributed to the CNTs in the network without any contribution from a polymer host matrix. Devices with low MWCNT packing density (0.31–0.85 µg/cm2) exhibit a frequency independent plateau in the low-frequency regime. At higher frequencies, the AC conductivity of these devices increases following a power law, characteristic of the universal dynamic response (UDR) phenomenon. On the other hand, devices with high MWCNT concentrations (>1.0 µg/cm2) exhibit frequency independent conductivity over the entire frequency range (up to 1 MHz), indicating that conduction in these devices is due to direct contact between the CNTs in the network. A simple single-relaxation time electrical equivalent circuit with an effective resistance and capacitance is used to describe the device performance. The electrical noise measurements on devices with different MWCNT packing densities exhibit bias-dependent low-frequency 1/f noise, attributed to resistance fluctuations.

Low-cost synthesis of multi-walled carbon nanotubes using red soil as catalyst

Low-cost catalysts are of great significance for the batch synthesis of carbon nanotubes. In this study, the low-cost red soil was directly used as a natural catalyst to catalyze the growth of multi-walled carbon nanotubes (MWCNTs). The results of SEM, TEM, Raman, TG and carbon yields of the products consistently showed that 400 °C calcined red soil lead to high quality MWCNTs growth, the Raman IG/ID of the product is 1.66, which indicates that the product has exceeded the graphitization of many industrially synthesized MWCNTs. The high catalyzation efficiency may be attributed to the fact of composition characteristics that red soil lacks alkali metals and alkaline earth metals but is rich in iron and aluminum oxide, making the composition of red soil similar to the catalyst composition used in the synthesis of carbon nanotubes by common chemical vapor deposition method. Meanwhile the impurity content is less than other natural catalytic materials. The porous structure formed after proper calcination has also played a positive role to the catalytic growth of MWCNTs, which improved catalyst utilization by facilitating the gas phase diffusion. We explored a technique for synthesis of high-quality MWCNTs at low cost using soil as a catalyst.

Влияние облучения ионами аргона на фильтрационные свойства многостенных углеродных нанотрубок

The wettability and filtration efficiency of multi-walled carbon nanotubes (MWCNT) under irradiation with Ar+ ions with an energy of 100 keV have been investigated. Energy dispersive X-ray spectroscopy, Raman spectroscopy, and scanning electron microscopy were used to study the residual manganese content in the filter, as well as to study the structure of irradiated MWCNTs. High fluence irradiated MWCNT (HR-MWCNT) filters showed an improvement in Mn removal of up to 99.6% at a Mn concentration of 10 ppm. HR-MWCNT based filters are extremely hydrophilic, with a 66° wetting angle and high absorption capacity. The efficiency of manganese removal from an aqueous medium has been studied as a function of pH, initial concentration, and mass of MWCNT.

Effect of multi-walled carbon nanotubes on extractability of Sb and Cd in contaminated soil

The interaction between multi-walled carbon nanotubes (MWCNTs) and soil heavy metals was rarely studied. With the convenience of detecting multiple metal elements by ICP-AES, this paper examined the potential effectiveness of MWCNTs on extractability of antimony (Sb) and cadmium (Cd) in contaminated soil. Three-step sequential extraction procedure, toxicity characteristic leaching procedure, bioaccessibility and CaCl2 single extraction were employed to evaluate Sb and Cd speciations and their extractabilities. According to our results, only at low Sb content level of 100 mg/kg, antimony bioavailability reduced with MWCNTs addition of 0.3% and 0.9% by 22.97% and 20.74%, respectively, which might due to the increase of adsorption point, nevertheless, the excess Sb(OH)6- was not adsorbed more efficiently. Secondly, due to the difference in effective specific surface area, only under the condition of high content level and MWCNTs addition of 0.1%, the mild acid-soluble fraction increased at most by 15.40% for Sb and 9.40% for Cd, respectively. However, in terms of TCLP-extractable Sb and Cd and CaCl2-extractable Sb and Cd, no significant, continuous, regular extractability pattern were found. Overall, MWCNTs were selective on extractability of soil heavy metals due to mechanisms of physical adsorption. This paper provides data reference for the interaction between MWCNTs and soil heavy metals extractability.

Carbon fiber coating with MWCNT in the presence of polyethyleneimine of different molecular weights and the effect on the interfacial shear strength of thermoplastic and thermosetting carbon fiber composites

The effect of multi-walled carbon nanotubes (MWCNT) coating in the presence of polyethyleneimine (PEI) of different molecular weights (MW) on the interfacial shear strength (IFSS) of carbon fiber/acrylonitrile–butadiene–styrene (ABS) and carbon fiber/epoxy composites was investigated. The IFSS between the carbon fiber and the polymer was evaluated by means of single fiber microbonding test. The results indicated that uses of the carbon fibers uncoated and coated with pristine, low MW PEI-treated, and high MW PEI-treated MWCNT significantly influenced the IFSS of both thermoplastic and thermosetting carbon fiber composites as well as the carbon fiber surface topography. The incorporation of low MW (about 1300) PEI into the carboxylated MWCNT was more effective not only to uniformly coat the carbon fiber with the MWCNT but also to improve the interfacial bonding strength between the carbon fiber and the polymer than that of high MW (about 25,000) PEI. In addition, carbon fiber/epoxy composite exhibited the IFSS much higher than carbon fiber/ABS composite due to the chemical interactions between the epoxy resin and amine groups existing in the PEI-treated MWCNT.

Role of inflammation in the malignant transformation of pleural mesothelial cells induced by multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) are one of the most widely used types of novel nano-fiber materials. The aim of this study was to establish an experimental system based on actual exposure dosage and environments and explore the roles and mechanisms of inflammation in the malignant transformation of pleural mesothelial cells induced by MWCNTs after low doses and long-term exposure. Here, we established an in vitro system by co-culturing macrophages and mesothelial cells and exposing these cells to high aspect ratio MWCNTs (0.1 μg/mL) for three months. Results indicated that IL-1β, secreted by macrophages stimulated by MWCNTs, may significantly enhance the release of inflammatory cytokines, such as IL-8, TNF-α, and IL-6, from mesothelial cells. Results obtained from proliferation, migration, invasion, colony formation, and chromosomal aberration studies indicated that MWCNTs may promote malignant transformation of mesothelial cells after long-term and low-dose exposure via inflammation. Furthermore, the obtained results demonstrated that the NF-κB/IL-6/STAT3 pathway was active in the malignant transformation of Met 5A cells, induced by MWCNTs, and played an important role in the process. In conclusion, our results showed that the NF-κB (p65)/IL-6/STAT3 molecular pathway, which was mediated by inflammation, played an important role in the malignant transformation of pleural mesothelial cells induced by MWCNTs. These findings also provide novel ideas and references for the treatment of mesothelioma and offers options for the occupational safety of nanomaterial practitioners.

Controlling distribution of multi-walled carbon nanotube on surface area of Poly(ε-caprolactone) to form sandwiched structure for high-efficiency electromagnetic interference shielding

Electromagnetic interference (EMI) shielding composites with high efficiency, low conductive fillers and easy available have been attracted the wide attention. Herein, the multi-walled carbon nanotubes (MWCNT) were confined distribution in the surface area of poly (ε-caprolactone) (PCL) to achieve the sandwiched composites by a two-step melt compression. First, thin PCL/MWCNT (PCLNT) conductive layers and pure PCL layers with different thickness were melt-compressed, respectively. Second, two PCLNT layers at two sides and one PCL layer in the middle were melt-compressed again to form the composites with MWCNTs distribution in the surface area. The sandwiched composites exhibited higher EMI shielding effectiveness (SE) than the conventional PCLNT composites with random distribution of MWCNTs. For example, the EMI SET of the C(15/0/15)-T(0.1/1.0/0.1) composites with 3.5 wt% MWCNTs in the whole composites was 67% and 9% higher than that of the conventional composites with 3.5 wt% and 15 wt% MWCNTs, respectively. Furthermore, the EMI shielding performance of the sandwiched composites depended on the thickness of the conductive surface area and the concentration of MWCNTs. The excellent EMI shielding was found in the composites with thick surface area and high MWCNT loadings on a whole. In addition, the asymmetrically sandwiched composites which the surface area in two sides had the different concentration of MWCNTs were fabricated to investigate the effect of the conductivity in front layers on EMI shielding. The higher reflection loss happened in the composites with the higher conductivity in front layer, which resulted in the higher EMI shielding performance.

Tuning rigidity and negative electrostriction of multi-walled carbon nanotube filled poly(lactic acid)

Multi-walled carbon nanotubes (MWCNTs) were utilized as an effective filler and dibutyl phthalate (DBP) as a plasticizer in the electro-responsive poly (lactic acid) matrix. Under on and off electric field, the MWCNT/PLA/DBP composites showed electromechanical recoverability with typical fast response times less than 1 min. The 0.1%v/v MWCNT-1200/PLA/DBP possessed the highest positive storage modulus sensitivity value of 1.95 at the electric field strength of 1.5 kV/mm. The storage modulus response with a value close to zero was observed at a MWCNT content between 0.8 and 0.9 %v/v. At high MWCNT concentrations, the storage modulus response became negative definite at high electric field strengths. This negative electrostriction behavior was in contrast to the positive definite electrostrictive responses of other materials. In the bending experiments, the 0.1%v/v MWCNT-2100/PLA/DBP produced relatively higher bending responses and dielectrophoresis forces at electric field strengths below 300 V/mm. At higher electric field strengths and higher MWCNTs contents, the dipole moment interaction was screened resulting in the decreases in the electrostriction, bending response and dielectrophoresis force. Thus, it has been demonstrated here that the MWCNTs induced the negative electrostriction in the plasticized PLA, possibly through the physical screening and free volume.

Preparation of MWCNT/PDMS Conductive Micro-Patterned Nanocomposites

Conductive multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) nanocomposites were prepared via solution method and their conductive micro-patterns were made using the doctor blade technique. The prepared patterns were characterized via scanning electron microscopy (SEM), cyclic voltam-metry, and four-point probe conductivity meter. SEM images of the cross-sections of micro-patterns revealed that by increasing MWCNT concentration from 5 to 10%, while the dense and smooth bulk structure converted to a brittle one, their conductivities raised from 0.07 up to 0.33 S/cm. These micro-patterns preserved their conductivities under high bending cycles except for high MWCNT loading which loses almost half of its conductivity. The cyclic voltammetry analyses showed that MWCNT/ PDMS conductive micro-patterns had supercapacitor properties. The specific capacitance of the composite containing 10 wt% of MWCNT was 0.35 F/g These nanocomposites can be used in cochlear implants due to their high conductivities. Their low working voltages ensure the safety of the neural tissues.