Influence Of Carbon Nanofibers Research Articles

Optimizing Catalyst Layer Structure with Carbon Nanofiber Additive for Better Performance of Proton Exchange Membrane Fuel Cell

Increasing the power density of proton exchange membrane fuel cell (PEMFC) is essential for its commercialization. Cathode catalyst layer (CCL) carbon additive is an effective method that can improve membrane electrode assembly (MEA) performance under high current density. In this work, carbon nanofiber (CNF) is used as CCL additive and its mechanism is studied. The influence of CNF on the CCL structure is studied by scanning electron microscope (SEM), nitrogen adsorption method and contact angle experiment. Meanwhile, the mechanism is examined by using polarization decomposition and impedance analysis combined with the result in characterization experiments. The results show that: (1) the MEA used in this work has the best performance when adding 1 wt%. The voltage rises 74 mV (15.42%) at 2 A cm−2; (2) CNF varies the MEA performance mainly through changing the hydrophobicity of CCL, influencing the mass transport resistance and the concentration polarization. The mass transport resistance decreases 57.18% at 2 A cm−2; (3) activation polarization values have a negative linear correlation with the peak volume values of the primary pores at around 4 nm in diameter. This study provided a detailed understanding of the mechanism of CNF additive in CCL and will be helpful for improving PEMFC performance.

Synthesis of Al-Al2O3-CNF Composite by Cold Spray Method: Powder Preparation and Synthesized Objects Characterization.

This paper is devoted to studying the composite material of the aluminum–alumina–carbon nanofiber (CNF) system. The paper considers in detail the process of preparation of the specified composite by ball milling, as well as the process of synthesis of a solid object (coating) by the cold spray method. The synthesized objects were studied using optical and electron microscopy, and the hardness of objects of various compositions was measured. The processes of interaction of composite particles are discussed in detail. The influence of CNF on the distribution of particles in a solid object and on the hardness of objects has been considered and discussed.

The effect of carbon nanofibers on transverse cracking in carbon fiber reinforced polymer: A 3D finite element modeling and simulation

The influence of carbon nanofibers (CNFs) on carbon fiber (CF) reinforced polymer (CFRP) is investigated in this study. A program is developed to generate the finite element model (FEM) for the nanocomposites. The randomness of both CNFs and CF in CFRP is considered. The effects of volume fraction of CNFs and CFs, as well as interfacial strength are analyzed numerically. The improvement in strength and toughness of composites under different loading conditions is investigated. It shows that CNFs lead the redistribution of stress in the matrix, which releases stress concentration between CFs and polymer and increases the initial damage threshold.

Influence of carbon nano fibers (CNF) on the performance of high strength concrete exposed to elevated temperatures

Carbon nano fibers (CNFs) were added into high strength concrete (HSC) to evaluate the fire endurance of incumbent matrix. The residual mechanical performance was evaluated by conducting material property tests namely compressive strength, tensile strength, stress-strain response, elastic modulus, compressive toughness and mass loss made with 0.1% CNF and 0.2% CNF as cement replacement in the temperature range of 23 °C to 800 °C. The internal structure damage on exposure to fire was analyzed by ultrasonic pulse velocity (UPV) in macro-phase while scanning electron microscopy (SEM) is used for micro and nano forensics. Being exceptionally conductive and resilient, these fibers reduce spalling potential via low thermal inertia and crack bridging action as established in forensic analysis. The test results revealed better retention in mechanical and physical properties of high strength concrete containing CNFs. Mathematical relationships based on statistical analysis have been proposed for predicting mechanical, durability and energy related properties of HSC modified with varying percentages of CNFs at elevated temperatures.

Homogeneously Dispersed Carbon Nanofiber/High-Density Polyethylene Nanocomposite Compatibilized by Dilakylimidazolium Tetrafluoroborate

High-density polyethylene (HDPE) was used in this study as a matrix for accommodating carbon nanofiber (CNF) along with ionic liquid, to investigate the effect of nanofibers loading on the morphological thermal and rheological properties of the composites. The nanocomposite materials were prepared via melt processing using dilakylimidazolium tetrafluoroborate (ionic liquid) as a compatibilizing agent. The samples blended with imidazolium ionic liquid exhibited higher thermal stability, while DSC analysis showed the clear miscibility of ionic liquid in the HDPE matrix with a single endothermic peak. The influence of CNF (ranging from 0, 0.5, 1, and 2 wt.%) and ionic liquid concentration on the viscoelastic parameters was investigated. The rheological analysis showed the shear-thinning behavior of the composites. An improvement in the viscoelastic properties was observed as the nanofiber concentration increased. Composites blended with ionic liquid (HDPE/CNF/IL) exhibited slightly lower values of complex viscosity and modulus over the corresponding HDPE/CNF nanocomposites. Therefore, it is also significant that the reduction in melt viscosity is an additional benefit for polymer composite processing as a result of the wetting effect by polymer-ionic liquid combinations.

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.

Influence of Carbon Nanofibers on the Shear Strength and Comparing Cohesion of Direct Shear Test and AFM

The stabilization and enhancement of the engineering properties of fine and coarse grained soil has heavily relied on reinforcement and admixture materials. This study discusses the effect of the additive of Carbon nanofibers (CNF) on the characteristics of soils in terms of shear strength. The content of CNF was changed within the range of 0.05 to 0.2% by total dry weight of the reinforced samples. In achieving the objective of minimizing the number of experimental runs and thus conserve material, time as well as overall cost, the Box–Behnken approach was chosen as the method for statistical prediction. The scanning electron microscopy (SEM) and Atomic force microscopy (AFM) has been utilized in studying features of CNF in stabilized soil samples and force at the origin of the cohesion (c) of soil. Test results reveal that the increases peak and residual shear strength of the reinforcement soil samples were increased with an increase in the CNF content. The pre-eminence of ionic correlation forces in the cohesion of soil was confirmed by the force (cohesion) measurements by (AFM). The statistical prediction’s relatively high correlation coefficients justified the results.

Influence of carbon nanofibers on orientative-exploratory behavior of rats

Influence of carbon nanofibers on orientative-exploratory behavior of rats

Influence of Carbon Nanofibers on the Mechanical Performance and Microstructure of Cement-Based Materials

Influence of Carbon Nanofibers on the Mechanical Performance and Microstructure of Cement-Based Materials

Mixed modes interlaminar fracture toughness of cfrp laminates toughened with CNF interlayer

In the present paper, the influence of carbon nanofiber on interlaminar fracture toughness of CFRP investigated using MMB(Mixed Mode Bending) tests. Vapor grown carbon fiber VGCF and VGCF-S, and multi-walled carbon nanotube MWNT-7 has been employed for the toughener of the interlayer on the CFRP laminates. In order to evaluate the fracture toughness and mixed mode ratio of it, double cantilever beam (DCB) tests, end notched fracture (ENF) tests and mixed mode bending (MMB) tests have been carried out. Boundary element analysis was applied to the CFRP model to compute the interlaminar fracture toughness, where extrapolation method was used to determine the fracture toughness and mixed mode ratio. The interlaminar fracture toughness and mixed mode ratio can be extrapolated by stress distribution in the vicinity of the crack tip of the CFRP laminate. It was found that the interlaminar fracture toughness of the CFRP laminates was improved inserting the interlayer made by carbon nanofiber especially in the region where shear mode deformation is dominant.

The effect of carbon nanofiber on the thermo-physical behavior of polyethylene oxide

Composites of polyethylene oxide (PEO) filled with carbon nanofiber (CNF) were prepared using solution mixing followed by melt mixing. The morpho- logy and thermophysical properties of these composites and of pristine polyethylene oxide were analyzed by scanning electron microscopy, differential scanning calo- rimetry, thermogravimetric analysis, and dynamical mechanical analysis. Crystallization kinetic data were an- alyzed within the Avrami approximation for the pri- mary stage of crystallization. The influence of CNF on the temperature dependence crystallization of PEO and the tendency of forming three-dimensional crystallites at higher crystallization temperature were observed. The nucleation features of CNFs dispersed within PEO were investigated by using Lauritzen-Hoffman nucleation theory. Crystallization activation energies were also com- puted; the results are in agreement with the Lauritzen- Hoffman theory. Thermogravimetric analysis and dyna- mical mechanical analysis showed a gradual increase of the thermal stability and of the storage modulus of the polymeric matrix due to the loading with CNFs and formation of a polymer-carbon nanofiber interface. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 120: 3574- 3580, 2011

Influence of Carbon Nanofibers and Piezoelectric Particles on the Thermomechanical Behaviour of Epoxy Mixtures

Vapor growth carbon nanofibers (CNFs), lead zirconate titanate piezoelectric (PZT) particles, as well as a combination of these two were added in an epoxy resin (EP), and their influence on the curing reaction was investigated. Moreover, the cured samples were characterised by dynamic scanning calorimetry and dynamic thermal mechanical analysis. The presence of the fillers had no significant effect of the curing reaction of the EP system and the glass transition temperature, Tg.

Processing and characterization of carbon-carbon nanofiber composites

Carbon-carbon composites (CCCs) have extremely high thermal stability and shock resistance and find use in aerospace applications and aircraft disk brakes. The processing of CCCs can be divided into three stages: curing of precursor resin/fiber-reinforced-laminate; carbonization; and densification. During carbonization, the precursor resin (such as phenolic and furfuryl alcohol) develops microcracks and oftentimes delaminations, which reduce the mechanical properties of the material. In this study, we investigated the influence of carbon nanofibers (CNFs) when mixed with phenolic matrix precursor on the microstructure and interlaminar shear strength (ILSS) of the ascured and carbonized composite specimens. CNFs offer low cost benefits, unlike traditional carbon nanotubes (CNTs) that tend to be expensive. Different loadings (0%, 2%, and 5% weight/weight of resin) of CNFs, in conjunction with various percentages of surfactant (0%, 12.5%, and 50% by weight of acetone) treated carbon fabric reinforcement were used for the study. The rationale for treating the fabric with surfactant was to vary interfacial conditions of reinforcing fiber-CNF-matrix. This paper outlines the work done in the processing of CCC-CNF composites, and the influence of surfactant and various percentages of CNFs on the resulting microstructure and ILSS properties. The use of CNFs provided a bridging mechanism for matrix microcracking and reducing matrix shrinkage that occurs during first carbonization. Porosity and delaminations were found to increase with increase in surfactant treatment. An inverse relationship was observed between ILSS and porosity. At the as-cured and carbonized stages, an optimal value of 2% CNFs yielded the highest ILSS values of ∼40 MPa and 6 MPa respectively.