Concentrations Of Multi-walled Nanotubes Research Articles

Synthesis, characterization and study of optical property of (PANI)1-x(MWCNT)x nanocomposites

The present paper deals with study of (PANI)1-x(MWCNT)x nanocomposites to find its materialistic possibilities in the application field of actuators, sensors, electronic devices and supercapacitors. The effect of doping concentration of multi walled nanotube (MWCNT) on surface morphology, structural and chemical properties of polyaniline (PANI), samples has been characterized by SEM and FTIR. SEM images show the appearance of lumps and holes into smooth PANI samples by addition of MWCNT nanoparticles. FTIR spectra also confirm the formation of PANI/ MWCNT nanocomposites. UV–VIS–NIR spectrophotometer is used to study the absorption spectra of the composite samples. The band gap energy (Eg) of the nanocomposites is determined using Tauc’s relationship. It has been observed that the increasing the MWCNT concentration in composites reduces the optical band gap which attributes the enhancement in electron delocalization along the polymer chain. Also, the increment in protons with MWCNT concentration extends the density of states more into visible region of EM spectra.

Investigation of the Relaxation Mechanical Properties of Nanocomposites Based on High-Density Polyethylene

The effect of nanotubes and nanofibres on the stress relaxation of nanocomposites based on high-density polyethylene (HDPE) was studied. It was found that a very low concentration of multiwall nanotubes (0.1 wt%) leads to a significant increase in the relaxing stresses over the entire period of relaxation. Generalised curves of the relaxation process were plotted, and it was found that the greatest reinforcing effect is rendered by the multiwall nanotubes with the greatest specific surface.

Investigating the Limiting Mechanical Properties of Nanocomposites Based on High-Density Polyethylene

The effects of nanotubes and modifiers on the elastic modulus and forced elasticity limit of high-density polyethylene were studied. It was found that a very low concentration of multiwalled nanotubes (0.1 wt%) leads to a considerable (twofold) increase in the elastic modulus and a certain increase in the forced elasticity limit. This is connected with the experimentally found increase in the degree of crystallinity of polyethylene when it is filled with the given nanoparticles.

Polyester-based thermoplastic elastomer/MWNT composites: Rheological, thermal, and electrical properties

Polyester-based thermoplastic elastomer (Hytrel®) was melt-compounded with multi-walled nanotubes (MWNTs) using an internal mixer and the changes in the thermal, electrical and rheological properties were investigated using a range of nanotube contents (from 0.1 to 7 wt%). Even at nanotube concentrations as low as 0.1 wt%, the crystallization temperature was remarkably elevated by 15 °C and it increased further up to 22 °C with a 5 wt% loading. On the contrary, the melting temperature increased by 2 °C with 0.1 wt% MWNTs and it was slightly decreased by further additions of MWNTs. Electrical conductivity measured by the four probe method was detected from the 1 wt% MWNTs, indicative of electrical percolation. In addition, MWNTs starting from 4 wt% and above had no significant effect on the electrical conductivity, while it rapidly increased with nanotube contents below 4 wt%. Dynamic rheological properties were measured using a strain controlled rotational rheometer. The complex viscosity increased with MWNT contents giving an abrupt increase between 0.5 and 1 wt% loadings. In addition, the storage and loss modulus increased in a different manner depending on the range of the nanotube concentration. In the Cole-Cole plot, the slope of the nanocomposites decreased from 1.63 to 0.74 with increasing nanotube contents. In the Casson plot, the addition of MWNTs up to 0.5 wt% did not show any yield behavior giving an extremely low value for the yield stress, but further additions of nanotubes increased it notably. The presence of nanotubes in the elastomer increased the relaxation time with nanotube contents and their effect became weak as the frequency increased.

High-performance Supercapacitor cells with Activated Carbon/MWNT nanocomposite electrodes

The purpose of this work was to investigate and improve the performance of supercapacitor cells with carbon-based nanocomposite electrodes. The electrode structure comprised activated carbon (AC), four types of multi-wall nanotubes (MWNTs) and two alternative polymer binders, Polyvinyl alcohol (PVA) or Polyvinylidene fluoride (PVDF). Electrode fabrication involved various stages of mixing and dispersion of the AC powder and carbon nanotubes, rolling and coating of the AC/MWNT/binder paste on an aluminium substrate which also served as current collector. The organic electrolyte utilised was 1M tetraethylammonium tetrafluoroborate (TEABF4) fully dissolved in propylene carbonate (PC). All devices were of the electrochemical double layer capacitor (EDLC) type, incorporating four layers of tissue paper as separator material. The surface topography of the so fabricated electrodes was investigated with scanning electrode microscopy (SEM). Overall cell performance was evaluated with a multi-channel potentiostat/galvanostat/impedance analyser. Each supercapacitor cell was subjected to Cyclic Voltammetry (CV) at various scan rates from 0.01 V/s to 1 V/s, Charge-Discharge at a fixed current steps (2 mA) and Electrochemical Impedance Spectroscopy (EIS) with frequency range from 10 mHz to 1 MHz. It was established that an AC-based supercapacitor with 0.15%w/w MWNT content and 30 μm roll-coated, nanocomposite electrodes provided superior energy and power and energy densities while the cells was immersed in the electrolyte; well above those generated by the AC-based EDLC cells.

Spectroscopic Investigations on Epoxy—Multiwall Carbon Nanotubes Composites

Room temperature electron spin resonance spectra of epoxy resins loaded with various concentrations of multiwalled carbon nanotubes of various lengths are analyzed. The resonance spectrum near the free electron line position is dominated by a single almost symmetric line assigned to delocalized electrons residing on multiwalled carbon nanotubes. The experimental research shown that: (1) The dependence of the g-factor on nanotubes length is controlled by the distortions of multiwalled carbon nanotubes. (2) The dependence of the g-factor on the concentration of multi-walled nanotubes reflects the interactions between electrons localized on different nanotubes. In insulating composites, the resonance line width broadens as the length and the concentration of multiwalled carbon nanotubes is increased. (3) For conducting composites, the dependence of the electron spin resonance line width on the length and concentration of multiwalled carbon nanotubes is controlled by Elliott contribution and exchange interactions, respectively. (4) The concentration of conduction electrons increases as the length and the concentration of multiwalled carbon nanotubes are increased.

Electrical Enhancement of Polyurethane Composites Filled with Multiwalled Carbon Nanotubes by Controlling their Dispersion and Damage

Dispersion of the functionalized multiwalled nanotubes (MWNT) in the polyurethane (PU) matrix and DC conductivity of the MWNT/PU composites are investigated with the oxidation conditions, the kind of surfactants and their content. First, the most optimal surfactant type and its critical micelle concentration in the MWNT suspension are determined as a cationic surfactant, benzalkonium chloride (BKC) of 0.6 wt.% to the MWNT content from DEA and FESEM results. All the MWNT oxidized under several conditions are negatively charged and functionalized with carboxylic group, whereas the degree of damage is different from oxidation conditions. In addition, each MWNT/PU composite derived from several oxidation conditions shows different DC conductivity at a characteristic MWNT content. It is found that in order to enhance DC conductivity of the polymeric composites containing the oxidized MWNT the better dispersion of MWNT should be obtained by effective functionalities and surfactant adsorption with preserving the intrinsic geometry of pristine MWNT.

Enhancement of the surface and bulk mechanical properties of polystyrene through the incorporation of raw multiwalled nanotubes with the twin‐screw mixing technique

AbstractIn this article, we present the effects of incorporated multiwalled nanotubes (MWNTs) on a metal surface and the bulk mechanical properties of as‐synthesized polystyrene (PS)–MWNT composites prepared with the twin‐screw mixing technique. The MWNTs used for preparing the composites were raw compounds that were not treated with any surface modifications. The morphology for the dispersion capability of the MWNTs in the PS matrix was subsequently characterized with transmission electron microscopy. Surface mechanical property studies (i.e., wear resistance and hardness) showed that the integration of MWNTs led to a distinct increase in the wear resistance and also the micro/nanohardness with up to a 5 wt % MWNT loading in the composites. Moreover, the enhancement of the wear resistance of the as‐prepared composites, in comparison with pure PS, was further identified with scanning electron microscopy observations of the surface morphology after testing. On the other hand, for bulk mechanical property studies (i.e., the tensile strength and flexural strength), the composites containing a 3 wt % concentration of MWNTs in the PS matrix exhibited the best performance with respect to the tensile strength and flexural strength. This means that this composition of MWNTs exhibited good compatibility with the PS matrix, and this can be attributed to the π–π interacting forces existing between the aromaticity of the MWNTs and PS matrix. Furthermore, at higher MWNT loadings (e.g., 5 wt %), raw MWNTs were aggregated in the polymer matrix, as observed by transmission electron microscopy. Also, this led to an obvious decrease in the tensile strength and flexural strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Optical Transmission and Conductivity of Nematic Liquid Crystals Containing Dispersed Multiwall Nanotubes

For nematic liquid crystals (LC) with small (0.01–0.15 wt%) concentration of multiwall nanotubes (NT) dispersed therein, optical transmission and electric conductivity were measured as a function of temperature. Characteristic changes in transmission at the nematic-isotropic phase transition temperature have been noted, suggesting that NT dispersed in the LC matrix behave in a manner similar to that of the conventional non-mesogenic dopants. This picture is supported by the electrical conductivity data. The electrical conductivity increased noticeably within ∼0.01–0.1 wt% range of NT concentrations in the LC matrix, and a marked difference in the measured electrical conductivity values for the LC matrices of different polarity (e.g., cyanobiphenyl and azoxy) was observed.

Thermal Degradation Study of Functionalized MWNT Reinforced Segmented Polyurethane Membrane

The thermal degradation of polytetramethylene glycol (PTMG, Mn 1/42900) based polyurethane (PU), along with four different weight contents (such as 0.25, 0.50, 1.0, and 2.5 wt%) of functionalized multiwalled nanotube (MWNT) reinforced PUs are studied in air as well as in nitrogen atmosphere. The degradation results are reported in 10 and 50% weight loss and derivative of thermogravimetry (DTG). As expected, PUs are thermally more stable in nitrogen than in air. However, the influence of MWNT content on thermal stability is unclear. At 0.25 and 0.50 wt% of MWNT content, thermal stability declined and a further increase of MWNT improved the thermal stability of PU. Fourier-transform infrared (FTIR) analysis is also performed for untreated and heat treated films in order to understand the degradation at different temperatures. Free C1/4O stretching neck dimension increases with increasing temperature which signifies breaking of H-bonding detected by FTIR measure ments.

Mechanical behavior of phenolic-based composites reinforced with multi-walled carbon nanotubes

Two types of carbon nanotubes (CNTs), the network multi-walled nanotubes (MWNTs) and the dispersed MWNTs, were used for fabricating MWNTs/phenolic composites. The MWNTs were synthesized using the floating catalyst method through the chemical vapor deposition process. The effects of the MWNT content on the mechanical properties of the composites were investigated. Modified Halpin–Tsai equation was proposed to evaluate the Young’s modulus and tensile strength of the MWNTs/phenolic composites by adopting an orientation factor and an exponential shape factor in the equation. It is found that the results obtained from the modified Halpin–Tsai equation on tensile strengths and Young’s moduli fit successfully the experimental ones. The tensile fracture surfaces of MWNTs/phenolic composites were examined using field emission scanning electron microscope to study the failure morphologies of the MWNTs/phenolic composites.

Magnetic birefringence in a suspension containing carbon nanotubes

We have studied the magnetic birefringence in aqueous suspensions prepared from cathode deposits containing up to 5% of multi-walled carbon nanotubes and in suspensions of some other carbon materials. The magnetooptical effect observed in the suspensions of materials with nanotubes can be considered as a superposition of two contributions, one being related to the presence of graphite and graphitelike structures in suspension and the other, to the multi-walled nanotubes. The magnetic birefringence technique can be used to determine the content of multi-walled nanotubes and to obtain carbon materials enriched with nanotubes.

Structure of carbon fiber obtained from nanotube-reinforced mesophase pitch

Flow-induced orientation of discotic mesophase precursor typically leads to a center-origin, radial microstructure in the resulting carbon fibers. In the present study, we report the microstructure of carbon fibers that were derived from mesophase pitch that was modified using carbon multi-wall nanotubes (MWNTs). For an MWNT content as low as 0.1 wt.%, the microstructure was found to be fairly random (rather than radial).

Mechanical Properties Of Polyaniline / Multi-walled Carbon Nanotube Composite Films

ABSTRACTHigh molecular weight polyaniline / multi-walled carbon nanotube composite films were fabricated using solution processing. Composite films with various weight percentages of multiwalled carbon nanotubes were fabricated. Physical properties of these composites were analyzed by thermogravimetric analysis, tensile testing, and scanning electron microscopy. These results indicate that the addition of multiwalled nanotubes to polyaniline significantly enhances the mechanical properties of the films. In addition, metal–semiconductor (composite) (MS) contact devices were fabricated, and it was observed that the current level in the films increased with increasing multiwalled nanotube content. Furthermore, it was observed that polyaniline containing one weight percent of carbon nanotubes appears to be the most promising composition for applications in organic electronic devices.