Strain-dependent electrical resistance of multi-walled carbon nanotube/polymer composite films

The strain-dependent electrical resistance characteristics of multi-walled carbon nanotube (MWCNT)/polymer composite films were investigated. In this research, polyethylene oxide (PEO) is used as the polymer matrix. Two representative volume fractions of MWCNT/PEO composite films were selected: 0.56?vol% (near the percolation threshold) and 1.44?vol% (away?from the percolation threshold) of MWCNT. An experimental setup which can measure electrical resistance and strain simultaneously and continuously has been developed. Unique and repeatable relationships in resistance versus strain were obtained for multiple specimens with different volume fractions of MWCNT. The overall pattern of electrical resistance change versus strain for the specimens tested consists of linear and nonlinear regions. A resistance change model to describe the combination of linear and nonlinear modes of electrical resistance change as a function of strain is suggested. The unique characteristics in electrical resistance change for different volume fractions imply that MWCNT/PEO composite films can be used as tunable strain sensors and for application into embedded sensor systems in structures.     

Electrochemical preparation and electrochemical behavior of polypyrrole/carbon nanotube composite films

Polypyrrole/multiwalled carbon nanotube (MWNT) composite films were electrochemically deposited in the presence of an ionic surfactant, sodium dodecyl sulfate (SDS), acting as both supporting electrolyte and dispersant. The effects of the surfactant and the MWNT concentrations on the structure of the resulting composite films were investigated. The electrochemical behavior of the resulting polypyrrole/MWNT composite film was investigated as well by cyclic voltammogram. The effect of the additional alternating electric field applied during the constant direct potential electrochemical deposition on the morphology and electrochemical behavior of the resulting composite film was also investigated in this study.     

Synthesis of polyaniline/multi-walled carbon nanotube nanocomposites in water/oil microemulsion

A water/oil microemulsion system having been successfully used for synthesizing polyaniline(PANi) nanoparticles, was employed for preparing PANi/multi-walled carbon nanotube (MWCNT) nanocomposites via in situ chemical oxidative polymerization. The structures and the electrical property of PANi/MWCNT nanocomposites were also studied. The studies showed that PANi could coat MWCNTs to form nanocables with core-shell structure, and the backbone structure of PANi was not damaged by the introduction of MWCNTs. The conductivities of PANi/MWCNT nanocomposites were higher than that of PANi. Moreover, a model was supposed to be used for describing a PANi/MWCNT nanocable formation by in situ microemulsion polymerization.     

Thermoelectric properties of porous multi-walled carbon nanotube/polyaniline core/shell nanocomposites

Porous polyaniline (PANI)-coated multi-walled carbon nanotube (MWNT) core/shell nanohybrids were fabricated through in situ polymerization and subsequently assembled into macroscopic composites. N(2) adsorption/desorption analysis indicated that the volume of nanopores increased significantly, which could make a significant contribution to phonon scattering. Thermal annealing was also carried out to improve the Seebeck coefficient of the as-produced nanocomposites. The optimal sample showed electrical conductivity of 14.1?S?cm(-1), a Seebeck coefficient of 79.8?μV K(-1) and thermal conductivity of 0.27?W?mK(-1), resulting in a highest figure of merit (ZT) of 0.01 at a very low loading of MWNTs (<1?wt%). These results will provide a potential direction to enhance thermoelectric performance of organic materials and also facilitate the application of organic materials in thermal energy harvesting or cooling.     

低温聚苯胺/碳纳米管复合材料的制备

采用原位聚合法合成出了具有较高导电性的聚苯胺及聚苯胺 /碳纳米管复合材料 ,考察了不同碳纳米管添加量对聚苯胺 /碳纳米管复合材料表面形态、材料结构及导电性的影响并进行了表征。结果证实 ,制备出的复合聚苯胺的电导率比所见报道值提高了 1～ 2个数量级 ,为高电导率聚苯胺的合成开辟了更广阔的前景。     

Electrical properties of polyaniline and multi-walled carbon nanotube hybrid fibers

We have fabricated for the first time one-dimensional multiwalled carbon nanotube (MWNT) nanocomposite fibers with improved electrical properties using electrospinning. Polyaniline (PANi) and poly(ethylene oxide) (PEO) were used as a conducting and a nonconducting matrix, respectively, for hybrid nanofibers including MWNTs. The hybrid nanofibers fabricated by electrospinning had a length of several centimeters and a diameter ranging from approximately 100 nm to approximately 1 microm. Transmission electron microscopic analysis confirmed that the MWNTs were successfully oriented along the fiber axis without any severe aggregation during electrospinning. The hybrid nanofibers showed an enhanced electrical conductance with increasing MWNT content up to 0.5 wt%, and compared to PANi/PEO fibers, they also showed a stable linear ohmic behavior. These hybrid conducting nanofibers can be applied to chemical and biosensors that require a high sensitivity.     

Synthesis and characterization of externally doped sulfonated polyaniline/multi-walled carbon nanotube composites

Composites of carbon nanotubes with attached carboxylic groups (c-MWCNTs) and water-soluble externally doped sulfonated polyaniline (ED-SPANI) were prepared by solution mixing of c-MWCNT and ED-SPANI aqueous colloids. Fourier-transform infrared spectroscopy, Raman spectroscopy, ultraviolet–visible (UV–Vis) absorption spectroscopy, field-emission scanning and high-resolution transmission electron microscopy were used to characterize their structure and morphology. Raman and UV–Vis spectra revealed the presence of electrostatic interaction between the C–N⁺ species of the ED-SPANI and the COO⁻ species of the c-MWCNTs. The addition of c-MWCNT to ED-SPANI can improve its thermal stability. The conductivity of 3 wt.% ED-SPANI/c-MWCNT composites at room temperature is sixteen times higher than that of ED-SPANI. These results demonstrate that the addition of a small number of c-MWCNTs to an ED-SPANI matrix can form a conducting network in well dispersed composites, thus increasing their electrical conductivity.     

Electrochemical behaviour and voltammetric determination of sulphadiazine using a multi-walled carbon nanotube composite film-glassy carbon electrode

The anodic oxidation of sulphadiazine (SD) was investigated at a glassy carbon electrode modified by multi-walled carbon nanotube (MWCNT–GCE), using cyclic voltammetry and chronoamperometry. The results indicate that MWCNT-modified GCEs show an efficient and selective electrocatalytic activity towards the anodic oxidation of SD among biologically important compounds in buffered solutions at pH?=?7. It was found that oxidation of SD at the surface of MWCNT–GCE occurs at a potential less positive than that of unmodified GCE (about 100?mV). The diffusion coefficient of SD was also estimated using chronoamperometry. The kinetic parameters such as the electron transfer coefficient between SD and modified electrode, α, and the charge transfer rate constant, k_s , for oxidation of SD at the MWCNT–GCE surface were determined according to the Laviron procedure. The dissociation constants of oxidised and reduced acid–base species of SD can be obtained from the E _1/2 versus pH curves. The linear dependence of the peak current on the concentration was observed in the range 10–2000?µmol?L^?1 with a detection limit of 7.1?µmol?L^?1. The method was also applied to determinate the SD in human blood plasma and urine samples.     

Near-superhydrophobic behavior of multi-walled carbon nanotube thin films

Thin films of multi-walled carbon nanotubes created by standard drop and dry methodology are reported here to give water contact angles of ~ 138° accessing an intermediate region between smooth, apolar materials and superhydrophobic surfaces. Their near-superhydrophobic nature is attributed to hierarchical nanoscale roughness leading to the formation of Cassie-Baxter interfaces. While complete quantitative determination of surface energy parameters was prevented due to the porous nature of the films, the dispersive component of nanotube surface energy was found to be in the range of 39.1-47.8 mJ/m².     

管径相关的多壁碳纳米管膜的压阻效应

利用三点弯曲法研究了不同管径的碳纳米管膜的压阻效应,实验结果表明,管径较小的碳纳米管膜与管径大的碳纳米管膜相比具有更显著的压阻效应,并对电阻随应力变化的机制作了详细的讨论.     

Preparation and characterisation of PE films of carbon nanotube/polyaniline (PAN) composite mixture

ABSTRACT

Polyaniline (PAN) composites filled with nanotube were prepared by twin-screw extruder in order to study the influence of PE reinforcing effect on the mechanical behaviour of the nanotube/polyaniline (PAN) composites. The mechanical property tests of the composites with and without PE were performed. The tensile and flexural strength of nanotube/polyaniline (PAN) composites with polyethylene (PE) was improved. In conclusion, the addition of PE favoured the improvement of the higher interface strength and so had good effect on improving the tensile and flexural properties of the composites. The dielectric strength was slightly increased with the PE content increasing and then decreased gradually. The hybrid film with 2 wt.% of PE shows the dielectric strength of 199 MV/m, which is about 6% higher than that of nanotube/polyaniline (PAN) film (188 MV/m).     

Lyocell/多壁碳纳米管复合纤维的制备及性能

将多壁碳纳米管(MWCNTs)水悬浮液、N-甲基吗啉-N-氧化物(NMMO)溶液及纤维素共混得到纺丝液,通过干湿法制备了Lyocell/MWCNT复合纤维。采用X-衍射仪(WAXD)、扫描电镜(SEM)、透射电镜(TEM)、强度仪等分析了所得纤维的结构和性能。WAXD图谱显示复合纤维仍然具有纤维素II晶型的结构,同时还保留了MWCNTs的特征衍射峰;二维X衍射结果表明:MWCNTs质量分数为5%的复合纤维中,MWCNTs与纤维轴的取向角为±15.2°,说明复合纤维中MWCNTs基本沿着纤维轴取向。SEM结果显示复合纤维中MWCNTs在Lyocell基体中分布均匀。对纤维的力学性能分析进一步表明:添加适量的MWCNTs可使复合纤维的力学性能提高,MWCNTs质量分数为1%的复合纤维的初始模量和强度分别比Lyocell纤维增加49.4%和15.7%。     

Inkjet printing of multi-walled carbon nanotube/polymer composite thin film for interconnection

In this paper, multi-walled carbon nanotube (MWCNT) ink was selectively patterned by inkjet printing on substrates to form conductive traces and electrodes for interconnection application. MWCNT was firstly functionalized using concentrated acid and dispersed in deionized water to form a colloidal solution. Various concentrations of MWCNT were formulated to test the stability of the solution. The printability of the MWCNT ink was examined against printing temperature, ink concentration and ink droplet pitch. Rheological properties of the ink were determined by rheometer and sessile drop method. The electrical conductivity of the MWCNT pattern was measured against multiple printing of MWCNT on the same pattern (up to 10 layers). While single layer printing pattern exhibited highest resistance, the CNT entangled together and formed a random network with more printed layers has higher conductivity. The electrical properties of the printed film was compared to a composite ink of CNT and conducting polymer (CNT ink was mixed with conductive polymer solution, Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate) (PEDOT:PSS)). Scanning electron microscopy (SEM) was used to observe the surface structure and atomic force microscopy (AFM) was used to study the morphology of the printed film under different conditions.     

Fabrication and characterization of a zirconia/multi-walled carbon nanotube mesoporous composite

A zirconia/multi-walled carbon nanotube (ZrO₂/MWCNT) mesoporous composite was fabricated via a simple method using a hydrothermal process with the aid of the cationic surfactant cetyltrimethylammonium bromide (CTAB). Transmission electron microscopy (TEM), N₂ adsorption–desorption, Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques were used to characterize the as-made samples. The cubic ZrO₂ nanocrystallites were observed to overlay the surface of MWCNTs, which resulted in the formation of a novel mesoporous–nanotube composite. On the basis of a TEM analysis of the products from controlled experiment, the role of the acid-treated MWCNTs and CTAB was proposed to explain the formation of the mesoporous–nanotube structure. The as-made composite possessed novel properties, such as a high surface area (312 m² · g^? 1) and a bimodal mesoporous structure (3.18 nm and 12.4 nm). It was concluded that this composite has important application value due to its one-dimensional hollow structure, excellent electric conductivity and large surface area.     

Preparation of titania covered multi-walled carbon nanotube thin films

The aim of this work was to investigate the effects of relative humidity on the formation of titania layers on the surface of multi-walled carbon nanotubes under regulated conditions in a sealed system. Reactive precursor compounds such as titanium (IV) oxychloride hydrochloric acid and titanium (IV) bromide were used as precursor to cover the surface of multi-walled carbon nanotubes (MWCNTs) under solvent conditions. The mixtures of MWCNTs and titania compounds were not stirred or sonicated. The effect of relative humidity was influenced using the mixture of sulphuric acid and water in desiccators. As-prepared titan-dioxide (TiO₂) layers were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TG), X-ray diffraction (XRD) and Raman spectroscopy. Our results revealed that TiO₂ layers with different thicknesses can be obtained using this simple sealed system. These TiO₂ covered multi-walled carbon nanotube films can be ideal candidates for different kinds of applications (e.g. sensors, virus filtration or catalysts).     

多壁碳纳米管／硅橡胶复合材料的湿度敏感特性

采用多壁碳纳米管和硅橡胶制备多壁碳纳米管／硅橡胶复合材料。研究了该复合材料的导电网络和湿敏特性。通过透射电镜观察经过化学修饰和未修饰的多壁碳纳米管的表面形貌,扫描电镜观察多壁碳纳米管／硅橡胶复合材料形成的导电网络结构;分析该复合材料的导电机理,研究多壁碳纳米管／硅橡胶感湿特性。结果表明,相对湿度在11％-98％的范围,...     

Synthesis of multi-walled carbon nanotube/silica nanoparticle/polystyrene microsphere/polyaniline based hybrids for EMI shielding application

Novel polystyrene microsphere (PSMS)-based PSMS/Si and polystyrene/silica nanoparticle/multi-walled carbon nanotube (PS/Si/MWCNT) nanocomposite has been prepared using in situ sol-gel and chemical amalgamation methods. Aniline monomer was introduced by in situ route to form PSMS/PANI, PSMS/PANI/Si and PSMS/PANI/Si/MWCNT nanocomposite. FESEM of nanocomposite indicated core-shell spherical and tubular morphology. Glass transition temperature (T_g) and maximum decomposition temperature (T_max) of PSMS/PANI/Si/MWCNT nanocomposite were found as 295°C and 524°C, respectively, which were higher than the PSMS/PANI (T_g = 245°C; T_max = 387°C) and PSMS/PANI/Si (T_g = 257°C; T_max = 388°C) nanocomposite. For nanocomposite dispersion, tetrahydrofuran was studied as fine solvent. XRD depicted amorphous nature of PSMS/Si and PSMS/PANI/Si; however MWCNT reduced amorphous character of PSMS/PANI/Si/MWCNT. Electromagnetic interference (EMI) shielding effectiveness improved from 0.1 dB (PSMS) to 12.3 dB (PSMS/PANI/Si) to 24.5 dB (PSMS/PANI/Si/MWCNT). The increase in EMI shielding effectiveness was also observed with variation in log of conductivity from ?14 mho m^?1 (PSMA) to 1.17 mho m^?1 (PSMS/PANI/Si/MWCNT).     

Study on the infrared property of polyaniline/multi-wall carbon nanotube composite

Composites of polyaniline (PANI) and multi-wall carbon nanotube (MWNT) were synthesized by in situ polymerization with different MWNT content. The composites were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The SEM photos indicated that a mass of MWNT was enchased into PANI matrix when the content of MWNT was low. With the MWNT content increases, the surface of MWNT was covered with PANI and formed the core-shell structure. From the FT-IR spectroscopy of the composites, it can be confirmed that there was interaction between PANI and multi-wall carbon nanotube. The composites had better thermal stability than pure PANI. Infrared emission property of the composites was analyzed by an IR-II infrared emissivity instrument and an infrared camera. It was found that infrared emission of the composites was lower than pure PANI in all wavelength range and infrared emissivity value was related to the content of MWNT in the composites.     

Electrochemical deposition of precious metal on carbon nanotube for methanol oxidation

Precious metal nanoparticles were prepared on carbon nanotube (CNT) by sequential and simultaneous deposition methods for the electrocatalytic study of methanol oxidation. All electrochemical measurements were carried out in a three-electrode cell. A Platinum wire and Ag/AgCl were used as auxiliary and reference electrodes, respectively. Suspension of the CNT and Nafion were mixed and dropped on glassy carbon as a working electrode. Cyclic voltammograms in H₂SO₄ electrolyte solution are attributable to hydrogen adsorption and hydrogen desorption resulting in promising electrochemical performance of the prepared precious metal nanoparticles. Cyclic voltamograms of methanol electrooxidation studied in 2 M CH₃OH in 1 M H₂SO₄ show a distinguishing shape with a prominent oxidation wave in the anodic scan contributed to methanol oxidation while the cathodic scan is associated with the accumulation of carbonaceous species.