Electrical Properties Of Carbon Research Articles

The effect of graphene oxide on thermal, electrical, and mechanical properties of carbon/epoxy composites: Towards multifunctional composite material

AbstractThe focus of this research work is to investigate the influence of graphene oxide (GO) on the mechanical, thermal, and electrical properties of carbon fiber‐reinforced polymer (CFRP) composites. The solvent mixing method with the new addition of a mixing stage is introduced for uniform distribution of graphene oxide in polymer. Different weight percentages of graphene oxide (1%, 1.5%, and 2%) were incorporated into the epoxy matrix, and the resulting composites were subjected to electrical conductivity, thermal conductivity, and interlaminar shear strength (ILSS) testing. The findings revealed a positive influence on material properties with the percentage of GO. Especially, the electrical conductivity and ILSS values reached up to 7.05 S/m and 11.03 MPa, respectively, when 1.5% GO by weight of the resin was added. The improvement in ILSS reported by 40% compared to the neat CFRP, and this increment was attributed to enhanced bonding between the epoxy matrix and carbon fabric. Maximum thermal conductivity of 1.04 W/m°K obtained at 1% GO filler, which is 15% higher than neat epoxy composite. Overall, these results illustrate the potential of GO as a promising filler to improve the electrical, thermal, and mechanical properties of CFRP composites. Proper optimization of graphene content in a polymer is needed to achieve the best multifunctional composite materials.Highlights The new solvent mixing method is introduced for uniform distribution of graphene oxide in polymer. Maximum thermal and electrical conductivity obtained at different percentages of graphene content in composite. Positive improvement is observed in mechanical, thermal, and electrical at a specific percentage of graphene in the composite. Proper optimization of nanofiller content in composite is needed to assess for maximum performance.

Mechanical and electrical properties of carbon nanotube/epoxy/glass‐fiber composites intended for nondestructive testing

AbstractIn this study, ternary polymer composites sheets comprising glass fiber (GF) reinforced epoxy with various fractions of carbon nanotubes (CNT) were manufactured using hot‐pressing technology. A multiscale morphology analysis was presented using scanning electron microscopy. The thermal behavior of the glass fiber reinforced polymer (GFRP) was investigated using thermogravimetric analysis, DSC, and DMA, which indicated an application temperature up to 71°C for the composites. Mechanical uniaxial stretching and three‐points bending tests showed that the addition of 0.1–0.2 wt% CNT decreased the dissipated energy of the specimen by 50% and increased the Young's modulus by more than 100%. During all stretching and bending measurements, the relative change in electrical resistance (RCR) was recorded as function of strain, revealing a relationship between the electrical signal and the applied deformation of the GFRP. Finally, the standard equation for fitting RCR versus strain was optimized, reducing the number of fitting parameters from five to three. The electrical and mechanical properties of the CNT/GF/epoxy composites show that they are suitable sensoring materials for wind‐turbine blades and other glass‐fiber reinforced epoxy constructions, especially for nondestructive testing.

Magnetic and electrical properties of carbon nanotube/epoxy composites

Composites based on epoxy resin filled with carbon nanotubes (obtained on metal catalysts: cobalt, iron and bimetallic iron -– cobalt) were prepared. The influence of carbon nanotubes on the electrical conductivity and magnetic properties of the obtained composites was examined. Magnetic resonance spectra of the studied samples were dominated by a single, intense, broad and asymmetrical line, which is typical for ferromagnetic resonance (FMR) spectra of strongly interacting iron and cobalt nanoparticles forming agglomerates. The FMR spectra of the modified carbon nanotubes in epoxy were satisfactory fitted by using two components of the Lorentzian lineshape. Magnetization processes had a strong influence on all parameters of FMR spectra. The surface anisotropy is assumed to be the most important contribution to the overall magnetic anisotropy. Electric properties of all composites were improved and composite containing carbon nanotubes obtained on iron – cobalt catalyst exhibited the highest value of electrical conductivity.

Effect of amine-functionalized dispersant on cure and electrical properties of carbon nanotube/epoxy nanocomposites

Abstract The efficient dispersion of carbon nanotubes, CNTs in epoxy resin is a challenging task to reach the final properties of the competent nanocomposite. In this study, the CNT/epoxy nanocomposite was fabricated by solution mixing process using an amine-functionalized dispersant. The dispersion of CNTs in organic solvent was further improved using an ultrasonic horn. According to the data obtained from UV–vis spectroscopy, a minimum ultrasonication time of 10 min is necessary to obtain proper dispersion of CNTs in organic solvent. The cure behavior of epoxy resin containing different CNT loadings was investigated by dynamic DSC thermograms. The higher CNT loading lowers the initial curing temperature and the peak temperature mainly due to high thermal conductivity of CNT. The SEM micrographs of the fractured surfaces showed the effect of dispersant on proper dispersion of CNTs in epoxy. The electrical percolation threshold was measured at about 0.5 wt% of CNT. However, the conductivity results revealed the adverse effect of dispersant on the nanocomposite electrical properties, mainly due to dispersant adsorption and hence screening the CNTs surface charges.

Manipulating microstructures and electrical properties of carbon fiber/reduced graphene oxide/nickel composite textiles with electrochemical deposition techniques

Since graphene and their composites play significant roles in the catalysts, energy storage, electronics and other fields, where electron transport is highly critical, here, we introduce reduced graphene oxide (RGO) interfaces in the carbon fiber (CF) networks for preparing a novel lightweight carbon fiber/reduced graphene oxide/nickel (CF-RGO-Ni) composite textile. Upon the charaterizations on the microscopic morphologies, electrical and magnetic properties, and density, the presence of RGO nanosheets and nickel nanoparticles would substantially influence the related physical properties in the resulting composite textiles. Furthermore, the key parameters, including RGO loading, deposition time, current density and annealing temperature of carbon matrices, have been studied to understand their effects on the electrochemical deposition of nickel nanoparticles. Implication of the results suggests that the RGO interface is a unique medium for essentially promoting the electrochemical deposition kinetics and active sites for growing nickel nanoparticles, which indicates a universal approach for preparing advanced lightweight composites with the presence of graphene naonstructures.

Structural characterization and electrical properties of carbon nanotubes/epoxy polymer composites

ABSTRACTThe purpose of this study is to identify the relationship between the electrical and structural characteristics of multiwalled carbon nanotubes dispersed into the polymer matrix of a resin. In a first step, the composites were characterized by small‐angle neutron scattering, which provide information about the bulk dispersion of nanotubes in the matrix and form three‐dimensional networks with a surface fractal behavior. In the second step, a dielectric and electrical study was carried out in the frequency range between 1 Hz and 10 MHz at room temperature. We have found that the electric and dielectric behavior of these composites can be described by Jonscher's universal dielectric response. We show that the critical exponents describing the concentration dependence of the conductivity and the dielectric constant, obtained in the vicinity of the percolation threshold, are in good agreement with the theoretical values. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44514.

Investigation on the mechanical and electrical properties of carbon nanotube/epoxy composites produced by resin transfer molding

For industrial application of carbon nanotube/polymer composites, it is critical to produce composites in an efficient way. In this study, large size carbon nanotube buckypaper, which is directly produced by floating catalyst chemical vapor deposition method, was used to reinforce epoxy through conventional resin transfer molding process. The infiltration behavior of resin was analyzed, indicating that efficient carbon nanotube-epoxy interface has been formed near the surface of the composites. With 26.87% weight fraction of carbon nanotubes, the composites show a great enhancement in mechanical properties, that the failure strength and Young’s moduli increase from 45 MPa and 2.5 GPa to 254.39 MPa and 6.69 GPa with a large failure strain over 15%. In addition, the composite film is electrically conductive with a conductivity of 220 S/cm. It also shows linear piezoresistive effect with a gage factor tested to be 2.68, indicating a great potential in multifunctional smart structure applications.

The mechanical and electrical properties of carbon nanotube‐grafted polyimide nanocomposites

ABSTRACTPolyimide (PI)‐based nanocomposites containing aminophenyl functionalized multiwalled carbon nanotubes (AP‐MWCNTs) obtained through a diazonium salt reaction was successfully prepared by in situ polymerization. PI composites with different loadings of AP‐MWCNTs were fabricated by the thermal conversion of poly(amic acid) (PAA)/AP‐MWCNTs. The mechanical and electrical properties of the AP‐MWCNTs/PI composites were improved compared with those of pure PI due to the homogeneous dispersion of AP‐MWCNTs and the strong interfacial covalent bonds between AP‐MWNTs and the PI matrix. The conductivity of AP‐MWNTs/PI composites (5:95 w/w) was 9.32 × 10−1 S/cm which was about 1015 times higher than that of Pure PI. The tensile strength and tensile modules of the AP‐MWCNTs/PI composites with 0.5 wt % of AP‐MWCNTs were increased by about 77% (316.9 ± 10.5 MPa) and 25% (8.30 ± 1.10 GPa) compared to those of pure PI, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 960–966

Rheological and electrical properties of carbon black‐based poly(vinylidene fluoride) composites

Carbon black (CB)–filled poly(vinylidene fluoride) composites (PCBp) were prepared by melt compounding. The linear rheology was then studied in detail. The composites show typical solid‐like response in the low‐frequency region, which is attributed to the percolation of CB particles. However, the transient percolated CB network is temperature dependent during the small amplitude oscillatory shear flow. Therefore, the principle of time–temperature superposition is invalid on the dynamic rheological responses of those percolated PCBp. A two‐phase viscoelastic model was then used to further describe the linear responses of PCBp to relate hierarchical structures of CB particles to flow responses of composites. In addition, the electrical and dielectric properties of PCBp were also investigated, aiming at further exploring the percolation behavior of CB. POLYM. ENG. SCI., 53:2541–2548, 2013. © 2013 Society of Plastics Engineers

Influence of filler alignment in the mechanical and electrical properties of carbon nanotubes/epoxy nanocomposites

In this work, we report the mechanical and electrical properties of carbon nanotubes/epoxy composites prepared with aligned and randomly oriented nanotubes as filler. The samples are disks of 30mm in diameter and 3mm in thickness. To obtain the carbon nanotubes alignment, an external electric field (250 VAC; 50Hz) was applied through the thickness of the sample during all the cure process. The AC electrical current was measured, during the cure, as a strategy to determine the optimum time in which the alignment reaches the maximum value. DC conductivity measured after the cure shows a percolation threshold in the filler content one order of magnitude smaller for composites with aligned nanotubes than for composites with randomly oriented filler (from 0.06 to 0.5wt%). In the percolation threshold, the achieved conductivity was 1.4×10−5Sm−1. In both cases, aligned and randomly distributed carbon nanotube composites, the wear resistance increases with the addition of the filler while the Rockwell hardness decreases independently of the nanotubes alignment.

A simulation study on the effects of shear flow on the microstructure and electrical properties of carbon nanotube/polymer composites

We employ a fiber-level simulation technique to simulate carbon nanotube (CNT)/polymer composites in simple shear flow. This model incorporates CNT flexibility, irregular CNT equilibrium shapes and CNT interactions. Electrical conductivity of the composites is determined using a resistor network algorithm. Tunneling resistance of the insulating matrix film between nanotubes is also considered. We show that the rate of imposed shear flow influences the composite conductivity by facilitating the formation or destruction of the conductive aggregates. In addition, the conductivity evolution during shearing for different concentrations is investigated. At low concentration, percolating clusters form and break simultaneously which causes large conductivity fluctuations during the simulations. When sufficiently large concentrations are reached, percolating clusters persist during shearing and the conductivity fluctuations decrease. In agreement with previous research we determine that increasing the shear rate causes alignment of the nanotubes in the flow direction. We show that upon shearing at constant shear rate, the system attains a state with substantially constant electrical conductivity, nanotube orientation and agglomerate size that is a function of the applied shear rate. The state reached for a given shear rate is independent of the initial state of orientation and aggregation.

Study of the Electical Conductivity of Oil Palm Fiber Carbon

The physical properties of carbon from natural fibers are strongly influenced by the conditions of carbonization process. Temperature carbonization process of natural fibers affects the structure and electrical properties of carbon. This research studied the influence of carbonization process to the electrical conductivity and the microstructure of carbon from oil palm fibers. Oil palm fiber carbonization process has been carried out at the temperature of 500°C and 900°C for 1 hour in the atmosphere of inert gas (nitrogen) and at a temperature of 1300°C performed using a Spark Plasma Sintering (SPS). Structure of oil palm fiber carbon analyzed using XRD and SEM, electrical conductivity measurements carried out using LCR meter. XRD data analysis showed that the carbon structure is amorphous, and carbonization process up to 1300°C cause increase of the degree of crystallinity, that are 36.92%, 39.07% and 42.48% for 500°C, 900°C and 1300°C respectively. Increase of carbonization temperature also causes the electrical conductivity of carbon that are (3.3 x10-6) S/m – (4.8 x10-6) S/m for carbon 500°C, 1.29 S/m – 1.3 S/m for carbon 900°C, and (1.4 x10) S/m – (1.7 x10) S/m for carbon 1300°C.

Mechanical and Electrical Properties of Carbon Nanotube/Cu Nanocomposites by Molecular-Level Mixing and Controlled Oxidation Process

A molecular-level mixing and controlled oxidation process is proposed as a novel fabrication technique for the production of CNT/Cu nanocomposite powders. The fabricated CNT/Cu2O nanocomposite powders showed microstructures with homogeneous dispersion of implanted CNTs in a Cu2O matrix. The CNT/Cu2O nanocomposite powders were reduced to CNT/Cu nanocomposite powders with H2 gas and then the as-prepared CNT/Cu nanocomposite powders were spark plasma sintered to fabricate CNT/Cu nanocomposites. The mechanical properties of the Cu and the CNT/Cu nanocomposites were characterized by tensile testing before and after hot compression. Before hot compression, the CNT/Cu nanocomposites were brittle, but after hot compression both yield strength and elongation were increased, while the yield strength of the Cu was decreased after hot compression. Hot compression enhanced the ductility and strength of the CNT/Cu nanocomposites due to alignment of Cu grains and CNTs. Electrical conductivity was also enhanced due to a reduced scattering of electrons because of the alignment of the CNTs and Cu grains as well as the annealing effects of the Cu matrix.

Experimental study of mechanical and electrical properties of carbon nanofiber/epoxy composites

Epoxy nanocomposites of different content of carbon nanofibers up to 1 wt.% have been fabricated under room temperature and refrigerated curing conditions. The composites were studied in terms of mechanical and electrical properties. Flexural modulus and hardness were found to increase significantly in refrigerated samples due to prevention of aggregates of nanofibers during cure condition. Increase and shifting in G-band by Raman spectra of these samples confirmed stress transfer and reinforcement between epoxy matrix and carbon nanofiber. Electrical conductivity improved by 3–6 orders after infusing carbon nanofibers in insulating epoxy. Room temperature samples acquired higher conductivity that was attributed to network formation by aggregates of nanofibers along the fiber alignment direction as revealed by electron microscopic studies.

Electrical anisotropy in multiscale nanotube/fiber hybrid composites

This letter reports an experimental and theoretical study on the electrical properties of carbon nanotube/glass fiber composites. Experimental measurements on unidirectional glass fiber composites with nanotubes dispersed in the polymer matrix show a high degree of anisotropy. The composites, manufactured with a vacuum infusion technique, do not show any significant process-induced anisotropy. Theoretical modeling reveals that the microstructure of the fiber composite plays a dominant role in the electrical behavior due to alteration of percolating paths in the carbon nanotube network.

Effects of surface modification of carbon nanotubes on the microstructure and electrical properties of carbon nanotubes/rubber nanocomposites

Effects of the surface modification of multi-walled carbon nanotubes (MWCNTs) by surfactant, hexadecyltrimethylammonium bromide (CTAB) and coupling agent, gamma-aminopropyltriethoxy silane (KH550), on the microstructure and electrical properties of rubber composites loaded with MWCNTs were studied. The results show that the CATB can improve the dispersion of MWCNTs, but it cannot improve the interfacial interaction remarkably between MWCNTs and rubber. While the use of KH550 is benefit of the dispersion of MWCNTs and induces the strong interfacial interaction, which often hinders electron transport in the composites. These results are further confirmed by the temperature and pressure dependencies of the electrical properties of the composites.

Effects of strain and temperature on the electrical properties of carbon black‐filled alternating copolymer of ethylene‐tetrafluoroethylene composites

AbstractCarbon black (CB)‐filled alternating copolymers of ethylene‐tetrafluoroethylene (ETFE) composites were prepared by the melt‐mixing method. The effects of strain and temperature on the electrical resistivity of the composites were elucidated in detail. Our results indicated that the CB content and CB particle size are the two main factors that influence the electrical resistance of the composites when they are subjected to strain. The large particle size CB‐filled ETFE composites with a low CB content show a significant increase in electrical resistivity as a function of strain. A linear relationship between the logarithm of the electrical resistivity of the composites and strain was observed, indicating that tunneling conduction plays an important role when the composites are subjected to strain. The tensile testing results indicated that the CB‐filled ETFE composites have reasonably good tensile properties.

Electrical property investigations of carbon, lubricant, and alternative overcoats of magnetic discs using mercury probe

This paper describes the results on the electrical properties of carbon, lubricants, and alternative overcoats of magnetic discs using mercury probe. Our data show that resistivity of the carbon overcoat is highly dependent upon carbon composition and process condition. For DC-magnetron sputtered carbon, C:H carbon has much higher resistivity than C:H:N carbon. On the other hand, ion beam deposited carbon has higher resistivity than sputtered carbon. This effect is more pronounced for C:H:N type carbon. The DC break-down voltage of carbon overcoat is a function of film thickness. Thicker carbon has a higher break down voltage, Z-dol lubricant is nonconducting and has very low break-down voltage. Resistivity of SiN and AlN overcoats on Al and glass substrates is also reported.

Fabrication and electrical properties of carbon/ polyesterimide thick resistive films

The preparation, morphology and basic electrical properties of carbon/polyesterimide (PEI) thick film resistors are presented. SEM observations have been used for microstructure investigation. The influence of carbon (conductive carbon black (CB) or graphite (G)) and the effect of an inorganic filler (TiO 2) on sheet resistance, normalized temperature dependence of resistance, durability to thermal shocks and moisture behaviour of two- and three-component systems are discussed.

MOMBE GROWTH OF CARBON DOPED p-TYPE GaAs AND InGaAs

The growth and electrical properties of carbon doped p-type GaAs and InGaAs grown by metal-organic molecular beam epitaxy (MOMBE) using trimethylgallium (TMG), solid arsenic and solid indium as source materials have been studied systematically. The experimental results show that the growth rate and hole concentration of the samples are affected strongly by growth temperature and molecular beam fluxes,especially for InGaAs epilayers. The mechanism of carbon incorporation and its influence on the properties of the samples were also analysed based on the experimental results. It is shown that the changes in growth rate and hole concentration are mainly due to the dependence of TMG decomposition process on the growth condition.