Vapor-grown Carbon Fiber Content Research Articles

Characterization of polypropylene/magnesium oxide/vapor-grown carbon fiber composites prepared by melt compounding

Abstract In this paper, we discussed the characteristics and properties of polypropylene (PP)/magnesium oxide (MgO) composites prepared by melt compounding. In addition, we also discussed the effect of adding vapor-grown carbon fiber (VGCF) to PP/MgO composite on the properties of the composites. The thermal conductivity of PP/MgO increased with MgO content. In the region of MgO content of more than 30 vol%, the thermal conductivity of PP/MgO with MgO-10 (particle size of 10 μm) is the largest by comparison of other PP/MgO with different MgO sizes. The thermal conductivity of PP/MgO became increased by adding VGCF in PP/MgO. According to the estimation of thermal conductivity using Bruggeman’s equation, no synergistic effect was observed by adding VGCF into the PP/MgO composite. The surface resistance of PP/MgO significantly decreased by adding VGCF at a content of more than 3 vol%. At VGCF content of 1 vol%, the surface resistance of the composite became large, and the value was more than 109 Ω/sq. In addition, the Non-Newtonian property of PP/MgO composite melt was enhanced by the addition of VGCF into the composite.

Effect of vapor grown carbon fiber content on microstructure and tensile properties of Ti64/TiC composite fabricated by powder metallurgy method

Ti-6%Al-4%V (Ti64) alloy powder coated with vapor grown carbon fibers was consolidated to fabricate titanium matrix composites by spark plasma sintering, followed by hot extrusion process. Four compositions of the additive vapor grown carbon fibers were 0.1, 0.2, 0.3 and 0.4 wt. %. The microstructure was changed from the full lamellar of monolithic Ti64 alloy to the bimodal structure by addition of vapor grown carbon fibers to Ti64 alloy. The changing of microstructure was attributed by an α-stabilize effect of carbon (vapor grown carbon fiber). Almost all the vapor grown carbon fibers reacted with Ti and result in formation of Ti6C3.75 carbide phases detected by x-ray diffractometer and energy dispersive spectrometer. Hardness was improved by effect of solid solution strengthening of carbon in the Ti matrix and reached the maximum value of 495.8 Hv. 0.2%YS and UTS were significantly increased by addition of 0.1 wt. % vapor grown carbon fiber. However, they were not much improved when more vapor grown carbon fiber content was applied. Ductility of the sample was affected by a change in microstructure when 0.1 wt. % of vapor grown carbon fibers was added because the bimodal structure shows higher ductility compared to the full lamellar structure. The carbide precipitation in TMCs was not much contributed in improving of strength and decreased a ductility of material.

Facile fabrication of superhydrophobic conductive graphite nanoplatelet/vapor-grown carbon fiber/polypropylene composite coatings

Abstract The fabrication of superhydrophobic surfaces with mechanical durability is challenging because the surface microstructure is easily damaged. Herein, we report superhydrophobic conductive graphite nanoplatelet (GNP)/vapor-grown carbon fiber (VGCF)/polypropylene (PP) composite coatings with mechanical durability by a hot-pressing method. The as-prepared GNP/VGCF/PP composite coatings showed water contact angle (WCA) above 150° and sliding angle (SA) less than 5°. The superhydrophobicity was improved with the increase of VGCF content in the hybrid GNP and VGCF fillers. The more VGCFs added in the GNP/VGCF/PP composite coating, the higher porosity on the surface was formed. Compared to the GNP/PP and VGCF/PP composite coatings, the GNP and VGCF hybrid fillers exhibited more remarkable synergistic effect on the electrical conductivity of the GNP/VGCF/PP composite coatings. The GNP/VGCF/PP composite coating with GNP:VGCF = 2:1 possessed a sheet resistance of 1 Ω/sq. After abrasion test, the rough microstructure of the GNP/VGCF/PP (2:1) composite coating was mostly restored and the composite coating retained superhydrophobicity, but not for the VGCF/PP composite coating. When the superhydrophobic surface is mechanically damaged with a loss of superhydrophobicity, it can be easily repaired by a simple way with adhesive tapes. Moreover, the oil-fouled composite surface can regenerate superhydrophobicity by wetting the surface with alcohol and subsequently burning off alcohol.

Electrochemical and electromechanical properties of carbon black/carbon fiber composite polymer actuator with higher performance than single-walled carbon nanotube polymer actuator

The electrochemical and electromechanical properties of poly(vinylidene fluoride-co-hexafluoropropylene) based actuators using carbon black (CB)/vapor grown carbon fiber (VGCF)/ionic liquid (IL) composite gel electrodes formed without ultrasonication were compared with those of actuators using only CB or VGCF. The double-layer capacitance of the CB/VGCF/IL electrodes was larger than that of the CB/IL electrodes and increased with VGCF content. The amount of strain exhibited by the CB/VGCF/IL actuators was also larger than that for the CB/IL actuators, with the highest strain being produced for an actuator with a CB:VGCF ratio of 1:1. This was slightly larger than that for a polymer actuator using single-walled carbon nanotubes (SWCNTs), indicating that the proposed actuators exhibit sufficiently high performance for real-world applications without the need for expensive SWCNTs. Furthermore, the frequency dependence of the displacement response of the CB/VGCF/IL polymer actuators was successfully simulated using an electrochemical kinetic model similar to that for SWCNT-based actuators. The results yielded the strain in the low-frequency limit and the time constant of the response.

The effect of vapor-grown carbon fiber (VGCF) content on the mechanical properties and abrasion resistance of VGCF/PTFE composites

The effect of vapor-grown carbon fiber (VGCF) content on the mechanical properties and abrasion resistance of a VGCF/polytetrafluoroethylene (PTFE) composite was investigated. A resin powder of PTFE of 50 μm in diameter was used as the matrix. The resin and VGCF were mixed by a blender mill with the VGCF content in the range 0–3 wt%. Tensile testing was performed on an Instron type tensile testing machine at a crosshead speed of 10 mm/min (strain rate: 6 × 10 −3 /s), using smooth and V-notched tensile specimens. Thermal conductivity ( λ ) was measured using the laser flash method. The coefficient of dynamic friction ( μ ′) was measured using the ball-on-disc method. The results show that the tensile strength of VGCF/PTFE composites was lower than that of the PTFE matrix and decreased as the VGCF content increased due to the weak bonding between the VGCF and PTFE matrix. The abrasion resistance of PTFE was enhanced by the addition of VGCF-H. [TANSO 2013 (No. 259) 255–60.]

気相成長炭素繊維(VGCF)/PTFEコンポジットの機械的性質および耐摩耗性に及ぼすVGCF添加率の影響

The effect of vapor-grown carbon fiber (VGCF) content on the mechanical properties and abrasion resistance of a VGCF/polytetrafluoroethylene (PTFE) composite was investigated. A resin powder of PTFE of 50 µm in diameter was used as the matrix. The resin and VGCF were mixed by a blender mill with the VGCF content in the range 0-3 wt%. Tensile testing was performed on an Instron type tensile testing machine at a crosshead speed of 10 mm/min (strain rate: 6×10-3/s), using smooth and V-notched tensile specimens. Thermal conductivity (λ) was measured using the laser flash method. The coefficient of dynamic friction (μ′) was measured using the ball-on-disc method. The results show that the tensile strength of VGCF/PTFE composites was lower than that of the PTFE matrix and decreased as the VGCF content increased due to the weak bonding between the VGCF and PTFE matrix. The abrasion resistance of PTFE was enhanced by the addition of VGCF-H.

Electric Capacity Characteristic of Nanofiber/Vulcanized Rubber

Rubber material generally behaves as an electrical insulator, and vapor grown carbon fiber (VGCF) has excellent electrical conductivity. In our study, we mixed carbon nanofiber (VGCF) into styrene–butadiene rubber and investigated the relationship between strain and the electric capacitance of vulcanized rubber filled with VGCF, of which the hardness was not changed. The electric capacitance of the rubber filled with VGCF increased with VGCF content but decreased with increasing tensile strain. We confirmed that the change rate of electric capacitance is related to the VGCF content of the fillers. In order to investigate the relationship between strain and electric capacitance of rubber with VGCF, it is feasible to apply rubber composites filled with VGCF as a strain sensor.

ナノ繊維充てんゴムのひずみに伴う電気容量の変化

It is well known that a rubber material generally behaves as an electrical insulator and the vapor-grown carbon fiber (VGCF) has excellent electrical conductivity. In our study, we mixed carbon nanofiber (VGCF) into styrene-butadiene rubber, and investigated the relationship between strain and the electric capacitance of vulcanized rubber filled with VGCF, of which the hardness was not changed at all. The electric capacitance of the rubber filled with VGCF increased with the VGCF content, but decreased with the increasing tensile strain. It was confirmed that change rate of the electric capacitance is related to the VGCF contents of the fillers. In order to investigate the relationship between strain and electric capacitance of rubber with VGCF, the rubber composites filled with VGCF is feasible to apply as a strain sensor.

Electrical Conductivity of VGCF/ Aluminum Composites Fabricated by Electro Spark Sintering

Vapor grown carbon fiber (VGCF) was sleaved in acetone with ultrasonic vibration. Then pure aluminum powders with 3 μm in average diameter was poured into VGCF containing acetone and mixed with ultrasonic vibration. The composites were fabricated by electro spark sintering. The strength, rigidity, electrical conductivity and microstructure of the composites was investigated. VGCF was distributed uniformly and no pores was observed in composite. As increasing the volume fraction of VGCF in composites, the strength of composites increased gradually but the elongation decreased. The electrical resistivity of the composites increased as increasing VGCF content, constantly. The theoretical resistivity of composites without residual stress is lower than that of experimental results. It seems that is caused by the high dislocation density and strain introduced by big difference of thermal expansion between VGCF and pure aluminum.

Study of piezo‐damping properties of CPE/ZKF/VGCF composites

AbstractThe electrical and damping behaviors of chlorinated polyethylene (CPE)/2,2′‐methylene‐bis‐(4‐methyl‐6‐cyclohexylphenol) (ZKF)/vapor‐grown carbon fiber (VGCF) have been investigated. CPE/ZKF/VGCF systems exhibit typical percolation characteristics of filled conductive polymer composites. For CPE/ZKF/VGCF composites, dynamic mechanical analysis (DMA) shows that, at the glass transition temperature (Tg) of CPE/ZKF system, the values of loss factor increase with the increasing VGCF content. Within the temperature range of 60–75°C, the values of loss factor for CPE/ZKF/VGCF samples are higher than that of CPE/ZKF and present a peak at 16 vol% VGCF content. This implies that the piezo‐damping effect is directly related to the conductive network formation in the composites, and the piezo‐damping effect can be regulated by regulating the VGCF content. Therefore, the composite of CPE/ZKF/VGCF is a good damping material with a high and broad loss factor that can be regulated according to practical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3181–3185, 2006

Electrical and damping behaviors of CPE/BaTiO3/VGCF composites

The electrical and damping behaviors of chlorinated polyethylene (CPE)/barium titanate (BaTiO3)/vapor-grown carbon fiber (VGCF) composites have been investigated. CPE/BaTiO3/VGCF composites exhibit a lower percolation threshold compared to the CPE/VGCF two-component system. This can be attributed to the presence of BaTiO3 particles, which increases the effective concentration of VGCF in the composites. For CPE/BaTiO3/VGCF composites, the dynamic mechanical analysis shows that, at the glass transition temperature of CPE, the values of loss factor decrease with increasing VGCF content. However, within the room temperature region (around 25 °C), the values of loss factor for CPE/BaTiO3/VGCF samples are higher than that of CPE/BaTiO3 and present a peak at 8 vol.% VGCF content, which corresponds to the beginning of the second percolation stage. This may imply that the piezo-damping effect is directly related to conductive network formation in the composites and a new damping material with both a higher loss factor value and efficient stiffness in the region of practical temperature can be obtained by changing the composition of the CPE/BaTiO3/VGCF composites.

LPB용 MCMB 부극 도전재로 VGCF를 첨가한 부극의 특성 연구

An investigation upon the characterization of MCMB anodes with different vapor grown carbon fiber (VGCF) content for application in lithium polymer battery(LPB) was carried out. When VGCF material was used as conducting agent with MCMB active material, the impedance and the initial coulombic efficiency of test cells were found to decrease with the increasing amount of VGCF. On the other hand, as a function of added VGCF the discharge capacity and the utilization linearly with increased. Impedance of test cell with MCMB anode containing VGCF exhibited the lowest value whereas the impedance of VUF contained anode was similar to that of MCMB anode without VGCF. Interestingly, VUF contained anode showed the best battery characteristics. Internal resistance and rate capacity of the cell were. respectively, at 2C. Generally, rate capability and the cycleability of MCMB based test cells with VGCF content exhibited better results than the other cells. In the case of VGCF containing anode, the discharge capacity of the cell faded slowly with an ultimate charge-discharge cycling capacity of 178mAh/g at the 100th cycle. Thereafter, the discharge capacity faded negligibly and the utilization of the cell at the 100th cycle was more than . The effect of addition of VGCF is discussed in detail.

Electrical and dynamic mechanical behavior of BaTiO3/VGCF/LDPE composite

The electrical and dynamic mechanical behavior of barium titanate (BaTiO3)/vapor-grown carbon fiber (VGCF)/Low Density Polyethylene (LDPE) composites has been studied. The measurement of electrical conductivity exhibits a lower percolation threshold and a more distinct two-stage percolation region, especially with a wide plateau between the two stages, for BaTiO3/VGCF/LDPE composites compared to the two-component system of VGCF/LDPE. This can be attributed to increase of the effective concentration of VGCF and the obstruction of BaTiO3 particles on VGCF networks. The dynamic mechanical spectra of BaTiO3/VGCF/LDPE composites present a distinctive α relaxation region with its peak value nearly remaining constant at its high temperature side in contrast to the abrupt decrease of LDPE. Moreover, the loss factor in the α relaxation region reaches its largest value for the composite of 8 vol% VGCF content. This means that the piezo-damping effect really functions in BaTiO3/VGCF/LDPE composites and only in certain conditions can this effect have practical significance. Further examination of the damping behavior in a different relaxation region demonstrates that the piezo-damping effect is directly related to the relaxation behavior of the polymeric matrix. Also, the piezo-damping effect is highly temperature and frequency dependent. The dielectric measurements suggest that, before the formation of a certain critical conducting state, the energy dissipation approach of the piezo-damping effect may be mainly determined by the interfacial polarization effect in the composite. Thus, it may be inferred that the piezo-damping effect also contributes to the dramatic increase of the loss factor at the high temperature side of the α relaxation peak for the BaTiO3/LDPE composite and functions practically even if there is no presence of VGCF.

Morphology and electrical properties of short carbon fiber-filled polymer blends: High-density polyethylene/poly(methyl methacrylate)

Morphology and electrical properties of short carbon fiber-filled high-density polyethylene (HDPE)/poly(methyl methacrylate)(PMMA) polymer blends have been studied. The percolation threshold of HDPE50/PMMA50 blends filled with vapor-grown carbon fiber (VGCF), 1.25 phr VGCF content, is much lower than those of the individual polymers. The SEM micrographs verified that the enhancement of conductivity could be attributed to the selective location of VGCF in the HDPE phase. A double percolation is the basic requirement for the conductivity of the composites, i.e., the percolation of carbon fibers in the HDPE phase and the continuity of this phase in the blends, which hereby are defined as the first percolation and the second percolation, respectively. The SEM micrographs also showed that the short carbon fibers could affect the morphology of the blends. With the increase of VGCF content, the HDPE domains are elongated from spherical into strip shape, finally develop to a continuous structure. As a result, the second percolation threshold of the blends filled with 2.5 phr VGCF, 20 wt % HDPE, is lower than that of the blends filled with 1.5 phr VGCF, 30 wt % HDPE. The influence of molding temperature and time on the second percolation threshold has also been investigated. For the composites molded at a lower temperature, the second percolation threshold is shifted to a higher VGCF content, but there is little influence of molding time on the second percolation threshold. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1813–1819, 1998

Selective location and double percolation of short carbon fiber filled polymer blends: high-density polyethylene/isotactic polypropylene

The percolation threshold of high-density polyethylene (HDPE)/isotactic polypropylene (iPP) blends filled with vapor-grown carbon fiber (VGCF), 1.25 parts per hundred parts resin (phr) VGCF content, is much lower than those of the individual polymers. SEM micrographs verified that the improvement of electrical conductivity can be attributed to the selective location of VGCF in the HDPE phase. A double percolation is the basic requirement for the conductivity of the composites, i.e., the percolation of carbon fibers in the HDPE phase, and the continuity of this phase in the polymer blends. Short carbon fibers may affect the morphology of the polymer blends.

Electrical conductivity of short carbon fiber filled HDPE/PMMA blends: effect of molding temperature and time

The effect of molding temperature and time on the electrical conductivity of Vapor Grown Carbon Fiber (VGCF) filled High Density Polyethylene (HDPE)/Poly(methylmethacrylate) (PMMA) blends has been investigated. The dispersion state of short carbon fibers in polymeric matrix is affected not only by the volume fraction of filler, but also by the preparation conditions, such as pressing temperature and time. At a given VGCF content, the electrical conductivity of the composites, which were molded at a temperature higher than the melting temperature of HDPE, was measured as a function of pressing time. As a result of aggregation of VGCF, the networks facilitating electrical conduction were formed, and a percolation-like transition in conductivity was observed at a characteristic time, which was defined as the percolation time (tp). It was found that tp decreased with increasing VGCF content and molding temperature. The effect of molding time can be converted with that of molding temperature. From the plot of the logarithmic shift factor αt to the reciprocal temperature, a good linear relationship between them was observed, and the activation energy can be evaluated. Because the conductivity depended on the double percolation, i.e. the percolation of VGCF in HDPE phase and the continuity of this phase in the blends, the effect of molding time and temperature on the double percolation was also studied.