Use Of Carbon Nanofibers Research Articles

A new sustainable filtration membrane extraction method based on nanoconfined liquid phase extraction: Determination of organochlorinated pesticides and pyrethroids in tea samples

BackgroundPesticides are used in agricultural production for prevent and control crop diseases and pests, but it is easy to cause excessive pesticides residues in agricultural products, polluting the environment and endangering human health. Due to their unmatched and sustainable capabilities, nanoextraction procedures are becoming every day more important in Analytical Chemistry. In particular, nanoconfined liquid phase extraction has shown extraction capabilities toward polar, medium polar, and/or nonpolar substances, which can be easily modulated depending on the nanoconfined solvent used. Furthermore, this “green” technique showed excellent characteristics in terms of recoveries, extraction time (≤1 min), reliability, and versatility. (97) ResultsIn this work, the advantages of this technique have been coupled with those of filtration membrane extraction, making use of carbon nanofibers (CnFs) growth on carbon microspheres (CμS). This substrate has been deposited on a filter, which combined with gas chromatographic mass spectrometry (GC-MS) analysis successfully employed for the nanoextraction of 30 pesticides (18 organochlorine and 12 pyrethroids) in tea samples. Under the optimized extraction conditions, the linear range with standard solutions was from 1 to 1000 ng mL−1 (R2 ≥ 0.99), the limit of detections in tea samples were in the range 0.56–17.98 μg kg−1. The accuracy of the developed method was evaluated by measuring the extraction recovery of the spiked tea samples, and recoveries between 74.41 % and 115.46 %. (119) SignificanceConsidering the versatility of nanoconfined liquid phase extraction and the functionality of the filtration membrane extraction procedure, this new extraction method can be considered a powerful candidate for automatized high-throughput analyses of real samples. (34)

Carbon nanofibers and PVA fiber hybrid concrete: Abrasion and impact resistance

This study investigated the effects of carbon nanofibers (CNFs) and PVA fibers on the mechanical properties, impact resistance, abrasion resistance, and microstructure of ultrafine fly ash (UFA) high-performance concrete when used alone and in blends. CNFs and PVA fibers were incorporated at 0.1 %, 0.2 %, and 0.3 %, respectively. The results of the study revealed that CNFs and PVA fibers significantly enhanced the mechanical strength and cracking toughness of concrete, whether added individually or in blends. The enhancement of cracking toughness was more prominent in the mixed systems with higher fiber additions. Notably, the combined use of CNFs and PVA fibers can also significantly enhance the impact resistance and abrasion resistance of concrete. When the fiber addition is appropriate, the impact energy consumption is significantly increased. The optimal incorporation ratio was 0.1 % by volume of PVA fibers and 0.3 wt% by mass of CNFs. at this ratio, the impact resistance of concrete was improved by 128.24 % and the abrasion resistance was improved by 18.17 % compared to the control group. Further scanning electron microscopy (SEM) and mercury-in-pressure (MIP) tests revealed that the mixing of CNFs and PVA fibers effectively enhanced the densification of the concrete matrix, increased the amount of its hydration products, and strengthened the bonding of the fibers to the matrix.

Use of Carbon Nanofibers in the Additive Manufacturing of Aluminum Matrix Composites

Use of Carbon Nanofibers in the Additive Manufacturing of Aluminum Matrix Composites

Carbon nanofibers and polyvinyl-alcohol fiber hybrid-reinforced high-performance concrete: Mechanical property, chloride penetration resistance, and material characterization

The hybridization of nanomaterials and macroscopic fibers is currently a popular topic. The aim of this study was to explore the application potential of incorporating carbon nanofibers (CNFs) into concrete and to analyze the effect of CNFs dispersant on concrete slump and early strength. Polyvinyl alcohol (PVA) fibers and CNFs were used to prepare composite fiber-reinforced (CNFs-PVA) concrete to improve the continuity of concrete properties at the micron/nanometer scale. The engineering properties such as compressive strength, flexural strength and resistance to chloride ion erosion performance of the concrete were investigated, and the microstructure of concrete was characterized using X-ray diffraction (XRD), scanning-electron microscopy (SEM), and X-ray computed tomography (X-CT). The results showed that CNFs could improve the early strength. The combined use of CNFs and PVA increased the 28-day compressive and flexural strength by 23.38% and 28.73%, respectively, compared to the control group. Correspondingly, the electric flux and Migration rate of chloride ions (DRCM) were minimized. From the SEM and XRD test results, it is clear that CNFs and PVA fibers can: (i) bridge low-density C-S-H to form higher-density C-S-H gels, (ii) form longer chain-like fibers with enhanced load transfer and chloride binding capacity, (iii) act as internal curing agents to enhance hydration at the interface, (iv) promote the formation of the aluminum phase hydration products and calcium carbonate phase, and (v) CNFs and PVA refine the pore size by increasing the gel pores and reducing the percentage of microcracks. The combined results indicate that the improved performance of CNFs-PVA is due to the combined effect of bridging and nucleation of hydration products by CNFs, adsorption of hydration products by CNFs-PVA, and promotion of pore filling by the generated hydrides such as calcium carbonate and ettringite. These findings provide new insights for the design of high-performance concrete materials.

Efficient removal of Cs ion by electrochemical adsorption and desorption reaction using NiFe Prussian blue deposited carbon nanofiber electrode.

Prussian blue (PB) analog (NiFe, CoFe, FeFe, and commercial(cPB)) decorated carbon nanofiber (CNF) electrodes were synthesized by the drop casting method in this study to investigate the interaction between PB and CNF for the electrochemical adsorption (EA) and electrochemical desorption (ED) of Cs ion (Cs+). The adhesion of PB on the electrode and the EA and ED of Cs+ were substantially higher when the CNF electrode was used, compared with the fluorine-doped tin oxide supporting electrode. The use of CNF led to the smooth occurrence of EA and ED of Cs+, where the reported efficiency was: NiFe >FeFe >cPB. The EA and ED of Cs+ on NiFe decorated CNF (C-NiFe) were strongly affected by the loading amount of NiFe. Although the strongest EA capacity was identified when 1mg of NiFe was used, it decreased as the loading amount of NiFe increased. Thus, the EA of Cs+ occurs under the reduction of NiFe with some Fe(III) reduced to Fe(II) of NiFe, thus inducing more adsorption of Cs+. Overall, we confirmed that the C-NiFe electrode with appropriate thickness of NiFe layer is potentially an excellent adsorbent for Cs removal.

Effect of Carbon Nanofiber Clustering on the Micromechanical Properties of a Cement Paste.

The use of carbon nanofibers (CNFs) in cement systems has received significant interest over the last decade due to their nanoscale reinforcing potential. However, despite many reports on the formation of localized CNF clusters, their effect on the cement paste micromechanical properties and relation to the mechanical response at the macroscopic scale are still not fully understood. In this study, grid nanoindentation coupled with scanning electron microscopy and energy dispersive spectroscopy was used to determine the local elastic indentation modulus and hardness of a portland cement paste containing 0.2% CNFs with sub-micro and microscale CNF clusters. The presence of low stiffness and porous assemblage of phases (modulus of 15–25 GPa) was identified in the cement paste with CNFs and was attributed primarily to the interfacial zone surrounding the CNF clusters. The CNFs favored the formation of higher modulus C–S–H phases (>30 GPa) in the bulk paste at the expense of the lower stiffness C–S–H. Nanoindentation results combined with a microscale–macroscale upscaling homogenization method further revealed an elastic modulus of the CNF clusters in the range from 18 to 21 GPa, indicating that the CNF clusters acted as compliant inclusions relative to the cement paste.

Modeling of Energy Demand and Savings Associated with the Use of Epoxy-Phase Change Material Formulations.

This manuscript integrates the experimental findings of recently developed epoxy-phase change material (PCM) formulations with modeling efforts aimed to determine the energy demands and savings derived from their use. The basic PCM system employed was composed of an epoxy resin, a thickening agent, and nonadecane, where the latter was the hydrocarbon undergoing the phase transformation. Carbon nanofibers (CNF) and boron nitride (BN) particulates were used as heat flow enhancers. The thermal conductivities, densities, and latent heat determined in laboratory settings were introduced in a model that calculated, using EnergyPlus software, the energy demands, savings and temperature profiles of the interior and the walls of a shelter for six different locations on Earth. A shipping container was utilized as exemplary dwelling. Results indicated that all the epoxy-PCM formulations had a positive impact on the total energy savings (between 16% and 23%) for the locations selected. The use of CNF and BN showed an increase in performance when compared with the formulation with no thermal filler additives. The formulations selected showed great potential to reduce the energy demands, increase savings, and result in more adequate temperatures for living and storage spaces applications.

Углеродные нановолокна как электропроводящая добавка для электродов суперконденсаторов

The effect of electrically conductive additives in the active layer of electrodes on the electrochemical parameters of supercapacitor cells was studied. Carbon nanofibers (CNFs) obtained by pyrolysis of hydrocarbon mixtures (propane, butane, and isobutene) were used as a conductive additive. The obtained carbon nanofibers were introduced into the active layer of the carbon electrode at 10 to 40 wt %. The electrochemical characteristics of the electrodes were studied by galvanostatic charge–discharge and cyclic voltammetry in the range from 0 to 2.7 V. The impedance spectra were measured in the frequency range from 100 kHz to 10 MHz with an alternating current voltage of 10 mV. A 1 M solution of 1,1-dimethylpyrrolidinium tetrafluoroborate in acetonitrile was used as an electrolyte. The concentration of carbon nanofibers in the active electrode layer decreases the internal electrical resistance of the supercapacitor cell. The use of carbon nanofibers at 30 wt % in the active layer leads to a decrease in the internal series resistance and also increases the speed of ions inside the pores of the active electrode layer. The use of carbon nanofibers at up to 40 wt % leads to a decrease in the total specific surface area of the active layer, which reduces the specific capacity of the cells.

Electrochemical characterization of mixed matrix electrodialysis cation exchange membrane incorporated with carbon nanofibers for desalination

A new type of electrodialysis mixed matrix (MM) cation exchange membrane was prepared by incorporating carbon nanofibers (CNFs) into membrane matrix. The microscopy images showed uniform surface for the membrane relatively. The use of CNFs into membrane body enhanced membrane surface hydrophilicity, potential, transport number, permselectivity, and ionic conductivity obviously, while water uptake decreased. The sodium flux was also enhanced by incorporation of CNFs into membrane matrix from 0 to 0.5%wt and 2 to 8%wt, while declined for the samples in the range of 0.5 to 2%wt CNF ratios. Compared to pristine membrane, a smoother surface was observed for PVC-CNF membrane. Electrodialysis showed the (K+/Na+) flux ratio about 2.14. The transport mechanism of K+ and Na+ ions through the membranes discussed by considering ionic and hydrated radius, hydration potential, hydration free energy, entropy of hydration, and the Jones-Dole coefficient. Optimal performance was achieved for PVC-0.5%wt CNF membrane.

Supported Cobalt Nanoparticles with a Single Active Phase for Fischer–Tropsch Synthesis

Cobalt (Co) with a hexagonal-close-packed structure (hcp-Co) has been documented as a preferred active phase for Co versus face-centered-cubic structure (fcc-Co) in a Fischer–Tropsch synthesis (FTS) reaction. Thus, hcp-Co with high dispersion and durability is highly attractive, and in this work, its controlled formation was targeted. This is challenging, however, because of the complexity of the phase transition during the materials synthesis and processing. With the use of carbon nanofiber (CNF) as the catalyst support, a two-step approach through the controlled formation of an oxide precursor CoO, followed by its reduction, has been demonstrated to synthesize single-phase Co. The obtained Co/CNF catalysts were thoroughly characterized by using in situ and ex situ techniques, and it is revealed that the formation of pure-phase CoO nanocrystals was responsible for the final pure-phase Co that was formed. Compared to the conventional reduction–carburization–reduction (RCR) process, this method allows for ...

Characterization of the interfacial transition zone of CNF-Reinforced cementitious composites

Carbon nanofibers (CNFs) has become one of the most promising nanomaterials as an additive to cementitious composites, due to the improvements that can be seen in mechanical, electrical and thermal properties. Mechanical characterization has been conducted with cement paste, mortar and concrete with 0.1 wt% well-dispersed CNFs, and the modulus of elasticity is found to be improved by 21%, 34% and 29%, respectively. The improvement is more significant in mortar and concrete in spite of the presence of aggregate which reduces the volume fraction of CNFs, indicating a potential enhancement in the interfacial transitional zone (ITZ). The nano-characterization of the ITZ is performed in CNF-modified mortars and concrete using atomic force microscopy (AFM) and energy-dispersive X-ray spectroscopy (EDS). The results show the ITZ is enhanced mechanically (elastic modulus is increased) and chemically (Ca/Si ratio is reduced) due to the addition of CNFs. The characterization of the ITZ in the presence of CNFs offers an explanation for the different behaviors seen in nanomodified cement paste, mortar and concrete and facilitates the use of CNF in concrete in field applications.

Carbon Nanofibers As a Conductive Additive for Supercapacitor Electrodes

The effect of electrically conductive additives in the active layer of electrodes on the electrochemical parameters of supercapacitor cells was studied. Carbon nanofibers (CNFs) obtained by pyrolysis of hydrocarbon mixtures (propane, butane, and isobutane) were used as a conductive additive. The obtained carbon nanofibers were introduced into the active layer of the carbon electrode at 10 to 40 wt %. The electrochemical characteristics of the electrodes were studied by galvanostatic charge–discharge and cyclic voltammetry in the range from 0 to 2.7 V. The impedance spectra were measured in the frequency range from 100 kHz to 10 mHz with an alternating current voltage of 10 mV. A 1 M solution of 1,1-dimethylpyrrolidinium tetrafluoroborate in acetonitrile was used as an electrolyte. The content of of carbon nanofibers in the active electrode layer decreases the internal electrical resistance of the supercapacitor cell. The use of carbon nanofibers at 30 wt % in the active layer leads to a decrease in the internal series resistance and also increases the speed of ions inside the pores of the active electrode layer. The use of carbon nanofibers at up to 40 wt % leads to a decrease in the total specific surface area of the active layer, which reduces the specific capacity of the cells.

Antimicrobial properties of polysulfone membranes modified with carbon nanofibers and silver nanoparticles

Abstract The aim of this study was the fabrication of polysulfone membranes with antimicrobial properties. The strategy employed was based on the use of carbon nanofibers (CNF) presenting carboxyl functional groups (CNF COOH) and silver nanoparticles (AgNPs). The materials were investigated by XPS, SEM, TEM, EDX, and ICP-MS. The antibacterial activity was ascertained towards Escherichia coli and Bacillus subtilis both in solid and liquid media employing different synthesis routes for the AgNPs. In solid phase the Gram-positive bacteria showed higher sensitivity for PSF-CNF-Ag membranes, while in liquid phase the antimicrobial activity of the hybrid membrane is more pronounced towards Gram-negative species. Furthermore, in the case of E. coli, the growth inhibition in liquid medium is probably due to the synergetic action of the modified CNF and AgNPs.

Highest recorded electrical conductivity and microstructure in polypropylene–carbon nanotubes composites and the effect of carbon nanofibers addition

In the last decade, numerous investigations have been devoted to the preparation of polypropylene–multiwalled carbon nanotubes (PP/MWCNT) nanocomposites having enhanced properties, and in particular, high electrical conductivities (> 1 S cm−1). The present work establishes that the highest electrical conductivity in PP/MWCNT nanocomposites is limited by the amount of nanofiller content which can be incorporated in the polymer matrix, namely, about 20 wt%. This concentration of MWCNT in PP leads to a maximum electrical conductivity slightly lower than 8 S cm−1, but only by assuring an adequate combination of dispersion and spatial distribution of the carbon nanotubes. The realization of such an optimal microstructure depends on the characteristics of the production process of the PP/MWCNT nanocomposites; in our experiments, involving composite fabrication by melt mixing and hot pressing, a second re-processing cycle is shown to increase the electrical conductivity values by up to two orders of magnitude, depending on the MWCNT content of the nanocomposite. A modest increase of the highest electrical conductivity obtained in nanocomposites with 21.5 wt% MWCNT content has been produced by the combined use of carbon nanofibers (CNF) and MWCNT, so that the total nanofiller content was increased to 30 wt% in the nanocomposite with PP—15 wt% MWCNT—15 wt%CNF.

Understanding the critical chemistry to inhibit lithium consumption in lean lithium metal composite anodes

Understanding the consumption of active lithium using lean lithium composite anodes.

Use of Carbon Nano-Fibers in Cementitious Mortar

Cementitious materials, especially those with higher compressive strengths, provide relatively low toughness, tensile strength and strain capacity, and are susceptible to cracking under load and restrained shrinkage effects. These drawbacks were overcome through development of multi-scale reinforcement systems comprising carbon nanofibers and microfibers for high-strength cementitious mortars. Multi-scale reinforcement of the high-performance mortar produced significant gains in the flexural strength and toughness, and abrasion and impact resistance. Microstructural investigations were also conducted in order to provide insight into the structure and failure mechanisms of high-performance cementitious mortars with multi-scale reinforcement.

Designed Synthesis of Size‐Controlled PtCu Alloy Nanoparticles Encapsulated in Carbon Nanofibers and Their High Efficient Electrocatalytic Activity Toward Hydrogen Evolution Reaction

Well‐dispersed PtCu alloy nanoparticles (NPs) with a diameter of only ≈2 nm encapsulated in carbon nanofibers (CNFs) are synthesized using electrospinning technology followed by a graphitization process in a chemical vapor deposition furnace. Distinctly, even with a small amount of Pt, the PtCu/CNFs‐1:2 catalyst possesses outstanding hydrogen evolution reaction (HER) activity, including small overpotential, long‐term stability, and a high exchange current density as well as large double layer capacitance (Cdl). The excellent HER performance of the PtCu/CNFs‐1:2 catalyst is attributed to the synergistic interaction between Pt and Cu, the uniform distribution of the alloy NPs and the use of CNFs with 3D architectures. This development may provide a simple, efficient, and green synthesis method to design bi‐ or multimetal alloys for use as the cathode electrocatalysts for the HER or other electrocatalytic devices.

Monitoring Damage Propagation in Glass Fiber Composites Using Carbon Nanofibers.

In this work, we report the potential use of novel carbon nanofibers (CNFs), dispersed during fabrication of glass fiber composites to monitor damage propagation under static loading. The use of CNFs enables a transformation of the typically non-conductive glass fiber composites into new fiber composites with appreciable electrical conductivity. The percolation limit of CNFs/epoxy nanocomposites was first quantified. The electromechanical responses of glass fiber composites fabricated using CNFs/epoxy nanocomposite were examined under static tension loads. The experimental observations showed a nonlinear change of electrical conductivity of glass fiber composites incorporating CNFs versus the stress level under static load. Microstructural investigations proved the ability of CNFs to alter the polymer matrix and to produce a new polymer nanocomposite with a connected nanofiber network with improved electrical properties and different mechanical properties compared with the neat epoxy. It is concluded that incorporating CNFs during fabrication of glass fiber composites can provide an innovative means of self-sensing that will allow damage propagation to be monitored in glass fiber composites.

Use of Carbon Nanofibers Loaded With 1-Phenyl-3-Methyl-4-Benzoyl-5-Pyrazone for Preconcentration and Separation of Trace Rare Earth Elements Prior to Their Determination by ICP-MS

Use of Carbon Nanofibers Loaded With 1-Phenyl-3-Methyl-4-Benzoyl-5-Pyrazone for Preconcentration and Separation of Trace Rare Earth Elements Prior to Their Determination by ICP-MS

Mechanical property characterization of carbon nanofiber/epoxy nanocomposites reinforced by GMA-grafted UHMWPE fibers

Carbon nanofibers (CNFs) dispersed epoxy resin was reinforced with unidirectional glycidyl methacrylate (GMA) grafted ultra-high molecular weight polyethylene (UHMWPE) fibers. Tensile tests were performed on unfilled, and CNF filled epoxy to identify the effect of adding CNFs on the mechanical properties of epoxy. The highest improvement in strength was obtained with 1 wt% of CNF. Tensile and flexural properties improvements in three-component nanocomposites were confirmed by obtained results. The combined use of CNFs and GMA-grafted UHMWPE fibers leads to a significant synergy in the mechanical properties of nanocomposites. The mechanisms of such synergism were analyzed by fracture studies using scanning electron microscopy.