Amount Of Carbon Nanofibers Research Articles

The Effect of Carbon Nanofibers on the Mechanical Performance of Epoxy-Based Composites: A Review.

This review is a fundamental tool for researchers and engineers involved in the design and optimization of fiber-reinforced composite materials. The aim is to provide a comprehensive analysis of the mechanical performance of composites with epoxy matrices reinforced with carbon nanofibers (CNFs). The review includes studies investigating the static mechanical response through three-point bending (3PB) tests, tensile tests, and viscoelastic behavior tests. In addition, the properties of the composites' resistance to interlaminar shear strength (ILSS), mode I and mode II interlaminar fracture toughness (ILFT), and low-velocity impact (LVI) are analyzed. The incorporation of small amounts of CNFs, mostly between 0.25 and 1% by weight was shown to have a notable impact on the static and viscoelastic properties of the composites, leading to greater resistance to time-dependent deformation and better resistance to creep. ILSS and ILFT modes I and II of fiber-reinforced composites are critical parameters in assessing structural integrity through interfacial bonding and were positively affected by the introduction of CNFs. The response of composites to LVI demonstrates the potential of CNFs to increase impact strength by reducing the energy absorbed and the size of the damage introduced. Epoxy matrices reinforced with CNFs showed an average increase in stiffness of 15% and 20% for bending and tensile, respectively. The laminates, on the other hand, showed an increase in bending stiffness of 20% and 15% for tensile and modulus, respectively. In the case of ILSS and ILFT modes I and II, the addition of CNFs promoted average increases in the order of 50%, 100%, and 50%, respectively.

Sensing mechanisms of nanomodified Portland cement composites

Mortar sensors were fabricated as beams incorporating different amounts of carbon nanofibers (CNFs) synthesized in-situ on cement particles. Changes in electrical resistivity were measured and compared to recorded changes in compressive stress, temperature, and humidity. Sensing mechanisms and corresponding models were developed. The findings of the study indicate that the piezoresistive effect is influenced by the critical concentration of CNFs inside the composite matrix and the tunneling effect. In addition, water absorption and desorption, as well as the amount of chemically bound water played an important role in humidity sensing. Thermal fluctuation-induced tunneling conduction was dominant for the temperature sensitivity.

Formation and stability of the conducting cluster in the composite filaments based on polylactide and carbon nanofibers

AbstractComposite threads based on polylactide (PLA) containing up to 20 wt% carbon nanofibers (CNF) were produced using melt technology. The formation of a percolation cluster was studied in composite filaments with various morphologies (non‐oriented, subjected to isothermal crystallization, and oriented by six times). By adding 20 wt% CNF, a specific resistance of 100 Ohm m was achieved in the PLA filament. With orientation stretching, the specific resistance was 107 Ohm m, regardless of the CNF concentration. The scanning electron microscopy study showed poor adhesion between PLA and CNF. Threads containing 1 wt% CNF demonstrated stable conductive characteristics under dynamic loading for 24 h (50% of their breaking load). Studies of the creep of composite fibers have shown that small amounts of CNFs promote the sliding of polymer fibrils. In vivo tests showed that the addition of 5 wt% CNF led to an increase in the rate of bioresorption of PLA filaments. Additionally, the conductive properties were maintained for 12 months after implantation. The prepared filaments can be used in flexible electronics for biomedical applications.

Applying the Taguchi to Optimization the densification, and flexural strength of ZrB2–SiC–ZrC-CNFs

The purpose of this research is to optimize the densification, microstructure and flexural strength of ZrB2-25 vol% SiC composites reinforced by carbon nano fibers (CNFs) and zirconium carbide (ZrC). Spark Plasma Sintering (SPS) was applied for composites consolidation. Taguchi orthogonal array L9 as the design of statistical experiments (DOE) was evaluated to optimize the additives, as well as SPS parameters (temperature and time). Three levels were defined for each factor. The relative density (R.D%) and flexural strength of the samples were calculated based on Archimedes' law and the three-point bending test. Moreover, analysis of variance (ANOVA) was utilized to determine the importance of effective parameters and to optimize the SPS variables and compounds (the amount of CNFs and ZrC). The microscopic structure of surfaces was examined through field emission scanning electron microscopy equipped with energy dispersive spectroscopy (FE-SEM, EDS). The results showed that the best output of relative density and flexural strength was equal to 99.8% and 610 MPa, respectively, with an average ZrB2 grain size of 9.6 μm in a composite containing 15 vol% CNFs and 10 vol% ZrC and SPSed at 1875 °C for 7 min.

Application of Carbon Nanofiber-Modified Concrete in Industrial Building Design.

In order to explore the influence law and action mechanism of carbon nanofibers on the basic mechanical properties of concrete, the author proposes the mechanical properties and microscopic mechanism of carbon nanofiber-modified concrete. Concrete was prepared with different dosages of carbon nanofibers, and the compressive strength, flexural strength, and splitting strength of carbon nanofiber-modified concrete were tested, and the modification mechanism was explored. Experimental results show that an appropriate amount of carbon nanofibers can improve the mechanical properties of concrete. When the dosage is 0.3%, the mechanical properties of carbon nanofiber-modified concrete are the best, and its compressive strength, flexural strength, and split tensile strength are increased by 9.2%, 13.2%, and 17.5%, respectively, compared with plain concrete. Carbon nanofibers can form a three-dimensional network structure inside the concrete, which can improve the microscopic morphology of the concrete, enhance the toughness and integrity of the concrete, fill the pore defects inside the concrete, refine the pore size distribution, and consume part of the fracture failure energy when the concrete is damaged.

Microstructure and mechanical properties of aluminium matrix boron carbide and carbon nanofiber reinforced hybrid composites

In this study, aluminium matrix boron carbide (B4C) and carbon nanofiber (CNF) reinforced hybrid composite was produced by powder metallurgy method and their microstructure and mechanical properties were investigated. The samples were produced at 6 percentage volume ratios using hot pressing technique. Microstructure examination, hardness measurement, transverse rupture test, and wear tests were carried out in order to determine the mechanical properties of the samples. Also three-point bending test was performed to determine their transverse rupture strength (TRS). Wear tests were carried out based on the ball on disc method. The microstructure examination revealed that the reinforcing elements were relatively homogeneously distributed in the aluminium matrix. In addition, the fracture was brittle due to the notch effect and agglomeration occurred with increasing amount of CNF. As the CNF amount of the samples increased, their hardness values increased but their TRS values decreased. Results of the wear test indicate that the increased amount of CNF increased the wear resistance. The friction coefficient values of the samples varied between 0.535 and 0.646. When the hardness was examined together with TRS and wear test results, the most suitable sample was determined to be Al-7%B4C-1%CNF

Hygrothermal aging behavior and aging mechanism of carbon nanofibers/epoxy composites

In this study, carbon nanofibers (CNFs)/epoxy composites incorporating different contents of CNFs were fabricated and immersed in distilled water for 180 days. Water absorption test, tensile tests, scanning electron microscopy (SEM) observation, dynamic mechanical analysis (DMA), and Fourier transform infrared (FTIR) spectroscopy were performed to evaluate the effect of CNFs content on hygrothermal aging behavior of CNFs/epoxy composites, and to reveal the hygrothermal aging mechanism of such composites. Test results showed that the addition of CNFs into pure epoxy resin could obviously improve its hygrothermal aging behavior. The CNFs/epoxy composites had better resistance to water absorption than pure epoxy because CNFs improved the water barrier properties of the composites. The improvements of glass transition temperature and the storage modulus of the composites before and after aging were attributed to the fact that the addition of CNFs limited the loosening of molecular chains and increased the second cross-link density of epoxy resin. FTIR spectroscopy showed that the number of –OH functional groups of CNFs/epoxy composites was decreased, which revealed that CNFs inhibited the hydrolysis of epoxy resin and water absorption. This study demonstrates that adding appropriate amount of CNFs into epoxy resin has potential to improve the long-term durability of epoxy-based composites in hygrothermal environment.

Enhancement of Electrical Conductivity of Polyaniline Synthesized by using Carbon Nanofiber

Carbon nanofiber (CNF) is a very useful additive for improving the performance of polymer matrix composites, but the performance has sometimes been interrupted by limits appear within composite processing. Recently, CNF based polymer composites are intensely considered as promising materials in many application fields, such as electrical devices, electrode materials for batteries, supercapacitors, sensors, etc. Among these, the electrical conductivity is always the first priority need to be considered. Polyaniline (PANI) and PANI-CNF composites are synthesized by chemical oxidative polymerization of aniline monomers in acidic media. The electrical conductivity of PANI-CNF composites were found varies with the degree of amount of CNF under the effect of multiple factors such as the concentration of aniline monomer, reaction media, oxidant, reaction temperature, reaction time, etc. The maximum electrical conductivity was found 3.7131 S/cm of the PANI-CNF composite coming from the polymerization of aniline with 0.05 g CNF. The results of the synthesis also demonstrated that CNF can be an effective material to prepare electrically conducting polymer composites with ordered nanostructures.

Hygrothermal ageing behavior and mechanism of carbon nanofibers modified flax fiber-reinforced epoxy laminates

This study investigated the effects of carbon nanofibers (CNFs) content on hygrothermal ageing behaviors and mechanisms of flax fiber-reinforced epoxy (FFRE) laminates. CNFs/FFRE laminates containing 0.25–2.0 wt% CNFs were fabricated and immersed in distilled water for 180 days. Water absorption and tensile as well as thermodynamic properties were investigated. The research results showed that CNFs played a significant role in the improvement of hygrothermal properties of FFRE laminates. The water uptake of CNFs/FFRE laminates was significantly decreased because CNFs improved water barrier properties of the laminates. The improvements of tensile and thermodynamic properties of CNFs/FFRE laminates were attributed to the fact that CNFs strengthened the interface bonding and enhanced the matrix’s stability. This study demonstrates that adding appropriate amount of CNFs into FFRE laminates is beneficial to improving the hygrothermal durability of FFRE laminates.

Role of Carbon Nanofiber on the Electrical Resistivity of Mortar under Compressive Load

A nanomodified cement consisting of particles with in situ synthesized carbon nanofibers was developed to introduce a strong load-sensing capability of the hydrated binder matrix. The material was produced using chemical vapor deposition. The nanomodified cement contained 2.71 wt% of carbon nanofibers (CNFs). The electrical properties of the composite were determined. Several mortar samples were prepared by partially substituting ordinary Portland cement with 2, 4, 6, 8, and 10 wt% of the nanomodified cement. Additionally an ordinary Portland cement mortar was used as reference. The results show that the strongest piezoresistive response and therefore the best load-sensing was obtained for the mortar containing the highest amount of CNFs. This mortar contained 10 wt% of nanomodified cement. The fractional change in electrical resistivity of this mortar was 82% and this mortar had a compressive strength of 28 MPa.

Development of Carbon Nanofibers/Pt Nanocomposites for Fuel Cell Application

Carbon nanofibers (CNFs) were prepared via the deposition of acetylene gas on bimetallic catalyst (Fe–Co) supported on kaolin in a catalytic chemical vapour reactor. Carbon nanofibers/Pt nanocomposite (Pt catalyst) was synthesized by immobilization of potassium tetrachloroplatinate (IV) (K2PtCl4) onto the carbon nanofibers (CNFs) by a wet impregnation method. The effects of mass of carbon nanofibers (CNFs) (0.25–0.30 g) and deposition time (150–180 min) on the percentage of platinum (Pt) deposited on the nanofiber were investigated. The developed CNFs/Pt was characterized using different analytical tools such as HRSEM, EDS, HRTEM, BET, TGA, XRD, XPS and cyclic voltammetry (CV). The XRD patterns revealed the crystallite size of the Pt catalyst ranged between 5.54 and 6.69 nm, and the size decreased with increasing mass of support (CNFs). The HRTEM/HRSEM analysis of the CNFs/Pt catalyst showed that the dispersion and distribution pattern and the shape of the catalyst changes as the amount of CNFs increased from 0.25 to 0.3 g. However, deposition time did not influence the crystalline nature of the catalysts. XPS analysis demonstrated the existence of different oxidation states of Pt particles on the surface of CNFs. The CV analysis revealed that CNFs/Pt catalyst supports the oxygen reduction reaction and hydrogen oxidation reaction in the fuel cell. The platinum loading of 0.002–0.004 mgpt/cm2 in the fabricated electrodes using the developed CNFs/Pt nanocomposite was compared well with other electrodes (fabricated with other support materials) such as carbon black, carbon nanotubes, aerogel and titanium.

Experimental study on the effect of carbon nanofiber content on the durability of concrete

To study the effect of carbon nanofiber (CNF) content on the durability of concrete, the shrinkage test, freeze-thaw cycle test, penetration test and carbonation test of carbon nanofiber reinforced concrete (CNFC) with different volume fractions (0.1%, 0.2%, 0.3%, 0.4%, 0.5%) were carried out. In addition, the microscopic modification mechanism of carbon nanofibers (CNFs) to the durability of concrete was further explored by SEM test and MIP test. The results show that the microstructure of concrete can be improved and the pore structure can be refined by CNFs in two ways which are fiber bridging and pore filling, significantly improving the durability of concrete. The incorporation of appropriate amount of CNFs can significantly reduce the shrinkage rate, mass loss rate, compressive strength loss rate, seepage height, relative permeability coefficient and carbonation depth of concrete. When the volume fraction of CNFs is 0.3%, all the above indexes of CNFC are the smallest, therefore, the shrinkage resistance, frost resistance, carbonation resistance of CNFC are the best and the permeability is the lowest, which shows CNFC with a volume fraction of 0.3% performs the best durability. When the volume fraction of CNFs is more than 0.3%, the modification effect of CNFs on the durability of concrete is reduced, but the shrinkage resistance, frost resistance, and carbonation resistance of CNFC with a volume fraction of 0.5% are still evidently better than those of plain concrete (PC) and the permeability of it is lower than that of PC.

Effect of carbon nanofibers on the pore fractal law of concrete

In order to explore the effect of carbon nanofibers (CNFs) on the internal pore structure fractal law of concrete, carbon nanofiber reinforced concrete (CNFC) specimens with fiber content of 0%, 0.1%, 0.2%, 0.3% and 0.5% respectively are prepared, the internal pore structures of specimens in each group are analyzed by means of mercury intrusion porosimetry (MIP), and the pore fractal laws are further discussed by introducing fractal theory. The results show that, appropriate amount of CNFs can effectively reduce the total pore volume and the average pore size of concrete, and the inner pore size shows remarkable fractal characteristics, the fitting slope of ln(W n /r n 2) and lnQ n can be used as the fractal dimension D p of pore surface area; the D p decreased firstly then increased with the increase of CNFs content, and the larger D p is, the higher the large pore content and the larger the average pore size are.

Effect of Carbon Nanofibers on Strength and Pore Structural Characteristics of Concrete

In order to investigate the influence of carbon nanofibers (CNFs) on the strength and internal pore structural characteristics of concrete, the carbon nanofibers reinforced concrete (CNFC) specimens with the content of 0%, 0.1%, 0.2%, 0.3% and 0.5% were prepared. The characteristics of the internal pore structure of specimens in each group were analyzed by the method of mercury intrusion porosimetry (MIP). The results show that the appropriate amount of CNFs has a significant enhancement effect on the strength of concrete, but the excessive amount of CNFs (0.5%) will weaken the performance of concrete; CNFs can effectively reduce the total pore volume and average pore size of concrete, and the internal pore structure of concrete can be improved reasonably.

Physical and biological properties of alginate/carbon nanofibers hydrogel films

Alginates are renewable materials with excellent biocompatibility and cost-effectiveness in comparison with other biodegradable polymers. However, these hydrogels have poor mechanical properties that restrict their applications in biomedical fields such as skin tissue engineering. In this regard, the study follows an enhanced engineering route to produce alginate-based films reinforced with different amounts (0, 0.1, 0.5, 1 and 2% w/w) of carbon nanofibers (CNFs) and characterize their physical and biological properties. The results of this study showed that these composites possess similar biological properties to neat alginate hydrogels. Thus, none of the synthesized composite materials were cytotoxic and no cell adhesion was observed on the films. Water sorption at the body temperature did not suffer strong changes with the incorporation of CNFs into the alginate matrix. The dynamic mechanical and tensile/compressive properties of calcium alginate significantly improved with the addition of even a very low amount of CNFs. Thus, the tensile and compression modulus of the calcium alginate films in the dry and hydrated state increases up to three and six times, respectively, with the addition of 2% w/w CNFs. In addition, the composites reinforced with the lowest CNFs content have the advantage of possessing more transparency and lower production costs.

One-step synthesis of carbon nanotubes with secondary growth of carbon nanofibers: effect of chlorine, synthesis time and temperature

Applications of carbon nanotubes (CNTs) in nanoscale electronic, filtration and adsorption platforms, requires the production of a high density network structure of the CNTs, which are intermeshed and/or chemically connected to each other. Strong network structures can be created if a stable connection is established through cross-linked CNTs. In a previous preliminary study, we reported the secondary growth of carbon nanofibers (CNFs) that grew on top of the CNTs during the CNT synthesis through decomposition of 1,2-dichlorobenzene (DCB). In the current study, we studied in detail the effect of synthesis time and temperature on the secondary growth of CNFs on CNTs as well as the morphology of CNFs that were grown. The amount of CNFs that grew onto the main CNTs increased with an increase in the synthesis time for reactions performed at 60 and 90 min but decreased with a 120 min growth time. It is proposed that decomposition of the DCB let to Cl/carbon radicals that either (i) eroded the CNT surface or (ii) deposited on the CNT surface, depending on the synthesis parameters. The CNFs grew at defective sites of the CNT walls. A synthesis temperature of 700 °C and synthesis time of 90 min were the growth conditions that resulted in the highest formation of the CNFs, presumably due to formation of defects that were uncovered by carbon deposition and allowed for the secondary growth of CNFs. The types of defects created were identified as on-site defects in the graphene sheet by Raman spectroscopy. All other studied synthesis temperatures (i.e. 600, 650, and 750) were unfavorable for growth of secondary CNFs.

Study on the Self-Monitoring of Bending Fatigue Cumulative Damage for Carbon Nanofiber Polyurethane Cement

Polyurethane cement (PUC) is a kind of high-strength composite bending and strengthening material that is made by adding an appropriate amount of super fine aggregate, such as cement, into the polyurethane matrix. Carbon nanofiber polyurethane cement (CNFPUC) prepared by adding an appropriate amount of carbon nanofiber (CNF) can significantly reduce the resistivity of PUC. In order to reveal the change regulation of electrical resistivity of CNFPUC under fatigue load, the four-point bending fatigue life test of CNFPUC under different temperatures and stress levels was conducted by using a multifunction test device on a mixture of UTM-30 asphalt. The results showed that the resistivity increased slightly with the increase of bending strain in the process of the CNFPUC bending test, which presented a two-stage trend of a small increase and a sharp increase, and the maximum bending tensile stress was up to 26.65 MPa. Under periodic load, the resistivity increased with the increase of stress level and cycle times. When the damage amount reached 90%, the fatigue resistivity increased sharply, and with the increase of stress level, the effect of temperature on resistivity decreased gradually. This study may provide a theoretical basis for practical engineering applications.

Effect of carbon nanofibers on electrode performance of symmetric supercapcitors with composite α-MnO2 nanorods

α-MnO2 nanorods have been grown on the surface of carbon nanofibers (CNFs) for enhancing the electrical conductivity of MnO2. We have synthesized α-MnO2/CNF (0–5 wt%) nanocomposites using a co-precipitation method. The x-ray diffraction results confirm the formation of a single phase α-MnO2 and SEM/TEM images reveal the formation of α-MnO2 nanorods, whose size depends on the amount of CNF in the nanocomposite. Both the surface area and electrical conductivity of nanocomposites are found to be strongly influenced by the presence of CNF. While α-MnO2/CNF(1.25 wt%) exhibits the largest surface area (381 m2/g) and only a modest increase in the electrical conductivity compared to pure α-MnO2 nanorods, the α-MnO2/CNF(5 wt%) shows the least surface area (131 m2/g) but an order of magnitude higher electrical conductivity (0.67 S/cm). Cyclic voltammetry measurements show improved performance (higher specific capacitance and better cyclic stability) in all α-MnO2/CNF supercapacitors compared to that of pure α-MnO2. Ragone plot shows that although α-MnO2/CNF(1.25 wt%) exhibits the highest specific capacitance (313 F/g at 1 A/g) and hence the highest energy density of 32.8 Wh/kg, it has the least power density of 4250 W/kg. On the other hand, α-MnO2/CNF(5 wt%) shows the least energy density of 7.9 Wh/kg but with a higher power density of 8478 W/kg compared to α-MnO2/CNF(1.25 wt%). Our studies demonstrate that one can optimize both energy and power densities by controlling the amount of CNF in the nanocomposites.

Effective thermal conductivity for nanocarbon/polyimide and carbon nanofiber/hexagonal boron nitride/polyimide composites

Effective thermal conductivity (TC) was experimentally measured for single‐walled carbon nanotube (SWCNT)/polyimide (PI) composites with a filler content up to 8 vol% and for carbon nanofiber (CNF)/PI composites with a filler content up to 24 vol%. The measurement results indicated that the values for effective TC for SWCNT/PI and CNF/PI composites were similar up to a filler content of 8 vol%. The experimental results were then correlated via thermal conductive models proposed by Xue and by Hamilton and Crosser, and reasonable correlation results were obtained for both the SWCNT/PI and CNF/PI composite sheets. The Nielsen model capably reproduced the experimental TC values without parameter‐fitting operations. Moreover, correlations using the effective medium approach (EMA) were also performed by adjusting the interfacial resistance. Good correlation results were obtained for both the SWCNT/PI and CNF/PI composites, and the correlated interfacial resistance showed reasonable values that compared to those found in the literature. Furthermore, the effect that the coadditions of CNF and hexagonal boron nitride (hBN) exerted on the effective TC of PI was investigated for a wide range of ratios of CNF to hBN. A small amount of CNF significantly increased the effective TC of CNF/hBN/PI composites. POLYM. COMPOS., 40:3032–3039, 2019. © 2018 Society of Plastics Engineers

Influence of Carbon Nanofibers on Thermal and Mechanical Properties of NC‐TEGDN‐RDX Triple‐Base Gun Propellants

AbstractTriple‐base gun propellants composed of nitrocellulose (NC), triethylene glycol dinitrate (TEGDN) and cyclotrimethylenetrinitramine (RDX) with carbon nanofibers (CNFs) were studied to explore the effects of CNFs on the thermal and mechanical properties. The results indicated that CNFs with less than 0.50 wt % were evenly and randomly dispersed in the propellant, otherwise there existed obvious aggregation. Temperatures of initial decomposition and exothermic peak reduced with the increase of NCFs from 0.00 to 3.00 wt %. Decomposition enthalpy of the composites with 0.50 wt % NCFs was 1214.6 J g−1, increased by ∼131.4 J g−1 compared to that of NC‐TEGDN‐RDX propellants. Moreover, the mechanical properties were effectively tailored by varying the amount of CNFs added to the composition. Decomposition enthalpy of the propellant with 0.25 wt % CNFs were hardly compromised for achieving enhancement in the compressive and impact properties, while the tensile strengths decreased slightly compared to that of the propellants.