Ferial Ghaemi

Magnetized graphene layers synthesized on the carbon nanofibers as novel adsorbent for the extraction of polycyclic aromatic hydrocarbons from environmental water samples

The application of magnetized graphene (G) layers synthesized on the carbon nanofibers (CNFs) (m-G/CNF) was investigated as novel adsorbent for the magnetic solid-phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) in water samples followed by gas chromatography-flame ionization detector (GC-FID). Six important parameters, affecting the extraction efficiency of PAHs, including: amount of adsorbent, adsorption and desorption times, type and volume of the eluent solvent and salt content of the sample were evaluated. The optimum extraction conditions were obtained as: 5min for extraction time, 20mg for sorbent amount, dichloromethane as desorption solvent, 1mL for desorption solvent volume, 5min for desorption time and 15% (w/v) for NaCl concentration. Good performance data were obtained at the optimized conditions. The calibration curves were linear over the concentration ranges from 0.012 to 100ngmL(-1) with correlation coefficients (r) between 0.9950 and 0.9967 for all the analytes. The limits of detection (LODs, S/N=3) of the proposed method for the studied PAHs were 0.004-0.03ngmL(-1). The relative standard deviations (RSDs) for five replicates at two concentration levels (0.1 and 50ngmL(-1)) of PAHs were ranged from 3.4 to 5.7%. Appropriate relative recovery values, in the range of 95.5-99.9%, were also obtained for the real water sample analysis.

Carbon nanofibers decorated with magnetic nanoparticles as a new sorbent for the magnetic solid phase extraction of selected polycyclic aromatic hydrocarbons from water samples

A novel nano-adsorbent, magnetic carbon nanofibers (CNFs–Fe3O4), was prepared by impregnating magnetic Fe3O4 nanoparticles onto the surfaces of carbon nanofibers based on electrostatic interactions. The resulting nanoparticles were used as an adsorbent for the magnetic solid phase extraction of polycyclic aromatic hydrocarbons from environmental water samples. The experimental parameters affecting the extraction efficiency, including the amount of sorbent, desorption conditions, extraction time and salt concentration, were investigated and optimized. Under the optimal conditions, the detection limits of the method (S/N = 3) were in the range of 0.008–0.03 ng mL−1 and the limits of quantification (S/N = 10) were between 0.025 and 0.08 ng mL−1. The repeatability of the method was assessed through five consecutive extractions of independently prepared compound solutions at concentrations of 0.1, 10, and 100 ng mL−1. The observed repeatability ranged between 3.2% and 11.2%, depending on the considered compounds. The developed method was successfully applied to real water samples while the relative recovery percentages obtained from the spiked water samples at three level concentrations (0.1, 10 and 100 ng mL−1) were from 90.1% to 100.9%.

Application of Fuzzy Fractional Kinetic Equations to Modelling of the Acid Hydrolysis Reaction

In view of the usefulness and a great importance of the kinetic equation in specific chemical engineering problems, we discuss the numerical solution of a simple fuzzy fractional kinetic equation applied for the hemicelluloses hydrolysis reaction. The fuzzy approximate solution is derived based on the Legendre polynomials to the fuzzy fractional equation calculus. Moreover, the complete error analysis is explained based on the application of fuzzy Caputo fractional derivative. The main advantage of the present method is its superior accuracy which is obtained by using a limited number of Legendre polynomials. The method is computationally interesting, and the numerical results demonstrate the effectiveness and validity of the method for solving fuzzy fractional differential equations.

Effects of the surface modification of carbon fiber by growing different types of carbon nanomaterials on the mechanical and thermal properties of polypropylene

The potential usage of different types of carbon nanoparticles in the herringbone, tubular and sheet structures of graphene plates, such as carbon nanofibers (CNF), carbon nanotubes (CNT) and graphene (G) flakes and also CNF–G and CNT–G on the carbon fiber (CF) surface as fillers in composite materials, is discussed in this paper. The combination of 2D graphene of high charge density and 1D CNTs or CNFs of large surface areas generates a versatile 3D hybrid network with synergic properties. A one-step process, chemical vapour deposition technique has been applied to synthesis these carbon nanoparticles (1D, 2D and 3D structures) by use of bimetallic catalyst (Ni/Cu). The morphology and chemical structure of the fibers, which have an effect on the polymer properties, were characterized by means of scanning electron microscopy, transmission electron microscopy, and specially Raman spectroscopy. These techniques were used to identify carbon nanoparticles, access their dispersion in polymers, evaluate filler/matrix interactions and detect polymer phase transitions. Compared with the neat CFs, the synthesized hybrid fibers led to an increase of the BET surface area from 0.7 m2 g−1 to 46 m2 g−1. Besides that, polypropylene (PP) composites with different carbon-based fillers, such as G on CF (CF–G), CNF on CF (CF–CNF), CNT on CF (CF–CNT) and also CF–CNF–G and CF–CNT–G were prepared by the melt mixed method, and the effects of these particles on the mechanical and thermal properties were analyzed. The mechanical results were confirmed by a mathematical model that state the mechanical reinforcement of the resultant composites strongly depends on the type of filler used. Noteworthy, composites based on combination of G and CNT presented the highest mechanical and thermal properties than those based on other carbon nanoparticles.

Effect of growing graphene flakes on branched carbon nanofibers based on carbon fiber on mechanical and thermal properties of polypropylene

A one-step process, the chemical vapor deposition method, has been used to fabricate graphene flakes (G) on branched carbon nanofibers (CNF) grown on carbon fibers (CF). In this contribution, the G–CNF–CF fibers have been used as reinforcing fillers in a polypropylene (PP) matrix in order to improve the mechanical and thermal properties of the PP. A bimetallic catalyst (Ni/Cu) was deposited on a CF surface to synthesize branched CNF using C2H2/H2 precursors at 600 °C followed by growing G flakes at 1050 °C. The morphology and chemical structure of the G–CNF–CF fibers were characterized by means of electron microscopy, transmission electron microscopy, and Raman spectroscopy. The mechanical and thermal behaviors of the synthesized G–CNF–CF/PP composite were characterized by means of tensile tests and thermal gravimetric analysis. Mechanical measurements revealed that the tensile stress and Youngs modulus of the G–CNF–CF/PP composites were higher than the neat PP with the contribution of 76%, 73%, respectively. Also, the thermal stability of the resultant composite increased about 100 °C. The measured reinforcement properties of the fibers were fitted with a mathematical model obtaining good agreement between the experimental results and analytical solutions.

Bulk Production of High-Purity Carbon Nanosphere by Combination of Chemical Vapor Deposition Methods

A simple method to produce pure carbon nanosphere (CNS) in high yield using continuous chemical vapor deposition (CVD) technique (combination of floating catalyst CVD and fluidized bed CVD) is proposed. Carbon fiber substrate, acetylene precursor, and Fe catalyst are employed to produce CNS. X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectrometry confirm the formation of a high percentage of hexagonal carbon. The scanning electron microscopy images reveal spheres that confirm uniform structures. Thermal gravimetric analysis implies that the CNS are free from the carbon fiber substrate as they start to decompose at a lower temperature compared to that of carbon fiber substrate. Under the optimal conditions of 700°C in ambient pressure at 60 min of reaction time and 300 mL/min of acetylene flow rate, CNS with an average diameter of less than 200 nm, 98% purity and yield of 3.07 mg/mg is obtained.

Few- and multi-layer graphene on carbon fibers: synthesis and application

In the current study, we investigated the influences of chemical vapor deposition parameters on the formation of uniform structures of few- and multi-layer graphene (FLG and MLG) as a coating phase on carbon fiber (CF). To this end, the process conditions of the chemical vapor deposition method, such as catalyst concentration, reaction temperature and time, and also carbon source flow rate, were optimized. The resulting FLG and MLG with high yields led to the modification of the CF surface by improving its properties. By applying scanning electronic microscopy, transmission electron microscopy and Raman spectroscopy, the surface morphology and structural information of the G–CF were analyzed. It was observed that under different conditions the FLG–CF and MLG–CF were obtained with 54%, 58% yields and also 10.21 m2 g−1, 8.78 m2 g−1 BET surface areas, respectively. Besides that, the FLG–CF and MLG–CF were used as fillers in the polypropylene (PP) composite and the effects of the number of graphene layers on the mechanical and thermal properties of the composite were analyzed. It is noteworthy to mention, composites based on the CF coated with G with only a few layers presented the highest surface area, strength and thermal resistance compared to those based on multi layers.

Effects of Thickness and Amount of Carbon Nanofiber Coated Carbon Fiber on Improving the Mechanical Properties of Nanocomposites

In the current study, carbon nanofibers (CNFs) were grown on a carbon fiber (CF) surface by using the chemical vapor deposition method (CVD) and the influences of some parameters of the CVD method on improving the mechanical properties of a polypropylene (PP) composite were investigated. To obtain an optimum surface area, thickness, and yield of the CNFs, the parameters of the chemical vapor deposition (CVD) method, such as catalyst concentration, reaction temperature, reaction time, and hydrocarbon flow rate, were optimized. It was observed that the optimal surface area, thickness, and yield of the CNFs caused more adhesion of the fibers with the PP matrix, which enhanced the composite properties. Besides this, the effectiveness of reinforcement of fillers was fitted with a mathematical model obtaining good agreement between the experimental result and the theoretical prediction. By applying scanning electronic microscope (SEM), transmission electron microscope (TEM), and Raman spectroscopy, the surface morphology and structural information of the resultant CF-CNF were analyzed. Additionally, SEM images and a mechanical test of the composite with a proper layer of CNFs on the CF revealed not only a compactness effect but also the thickness and surface area roles of the CNF layers in improving the mechanical properties of the composites.

Microextraction in packed syringe by using a three-dimensional carbon nanotube/carbon nanofiber–graphene nanostructure coupled to dispersive liquid-liquid microextraction for the determination of phthalate esters in water samples

AbstractMicroextraction in packed syringe (MEPS) was combined with dispersive liquid-liquid microextraction (DLLME) for the extraction of phthalate esters (PEs) from water samples prior to their determination by GC with flame ionization detection. A three-dimensional nanomaterial composed of carbon nanotubes, carbon nanofibers and graphene was prepared by chemical vapor deposition (CVD) and employed as a sorbent for MEPS. The porous structure of the sorbent has been revealed by scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller adsorption. The effects of various experimental variables on the extraction efficiencies of the following PEs were studied: Dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, di-n-butyl phthalate, and di-2-ethylhexyl phthalate. After extraction, the GC assay gives a linear calibration plot that covers the 0.02 to 200 ng mL−1 PE concentration ranges. The method displays detection limits (at an S/N ratio of 3) in the range from 1 to 10 ng mL−1. Relative standard deviations for intra-day and inter-day precision are between 5.7 and 8.9%, and between 7.6 and 10.1%, respectively. The feasibility of the method was demonstrated by extracting and determining PEs in (spiked) real water samples, whereby recoveries in the range of 90.3–98.8% and RSD% lower than 10.3% were attained. Graphical abstractSchematic of a method for microextraction in packed syringe (MEPS) combined with dispersive liquid-liquid microextraction (DLLME) as a new approach for the extraction and preconcentration of phthalate esters (PEs). They were quantified by gas chromatography (GC) with flame ionization (FID) detection.

Synthesis of Different Layers of Graphene on Stainless Steel Using the CVD Method

In this study, different types of graphene, including single-, few-, and multi-layer graphene, were grown on a stainless steel (SS) mesh coated with Cu catalyst by using the chemical vapor deposition (CVD) method. Even though the SS mesh consisted of different types of metals, such as Fe, Ni, and Cr, which can also be used as catalysts, the reason for coating Cu catalyst on the SS surface had been related to the nature of the Cu, which promotes the growth of graphene with high quality and quantity at low temperature and time. The reaction temperature and run time, as the most important parameters of the CVD method, were varied, and thus led to the synthesis of different layers of graphene. Moreover, the presence of single-, few-, and multi-layer graphene was confirmed by employing two techniques, namely transmission electron microscopy (TEM) and Raman spectroscopy. On top of that, electron dispersive X-ray (EDX) was further applied to establish the influence of the CVD parameters on the growth of graphene.