Carbon nanofibers (CNFs) gained much interest in the last few years due to their promising electrical, chemical, and mechanical characteristics. This paper investigates a new nanocomposite composed of carbon nanofibers hosted by PVA and both are integrated in one electrospun nanofibers web. This technique shows a simple and cheap way to offer a host for CNFs using traditional deposition techniques. The results show that electrical conductivity of the formed nanofibers has been improved up to 1.63 × 10−4 S/cm for CNFs of weight 2%. The peak temperature of mass loss through TGA measurements has been reduced by 2.3%. SEM images show the homogeneity of the formed PVA and carbon nanofibers in one web, with stretched CNFs after the electrospinning process. The formed nanocomposite can be used in wide variety of applications including nanoelectronics and gas adsorption.
Carbon fibers are of great technological and industrial interest because of their promising characteristics such as high strength to weight ratio, excellent chemical resistance, and superior electrical and thermal conductivity [
Carbon nanofibers from Sigma Aldrich, composed of graphitized (iron-free) conical platelets, have been used. In addition, polyvinyl alcohol (PVA) is used as the host material of electrospun nanofibers, with 88% degree of hydrolysis from Dupont, Taipei, Taiwan. Based on the authors’ experimental work, PVA is dissolved in deionized water at concentrations 13 wt% for best electrospun nanofibers. In more detail, the chosen concentration is found to be optimal for producing electrospun mats with minimal visual defects such as pinholes or wet fleeces. Carbon nanofibers with different weight ratios (1 and 2 wt%) are added to the PVA solution and stirred at room temperature for two hours to form a homogeneous gel.
The electrospinning setup, as shown in Figure
Schematic illustration of the setup of the electrospinning device.
The mean diameter of the electrospun nanofibers is measured by FEI Quanta 200 Environmental Scanning Electron Microscope (ESEM); 5 × 5 mm sections of nanofiber web were mounted on SEM holder. The conductivity of the electrospun nanofibers has been measured through 4-point probe station, in which Keithley 2400 voltameter measures the
Thermogravimetric analyses (TGA) of the electrospun composites have been done to observe the influence of carbon nanofibers on the degradation process of PVA. The electrospun nanofibers have been placed in an aluminum pan and heated from room temperature to 600°C at nitrogen atmosphere with the heating rate of 10°C/min. Differential Scanning Calorimetry (DSC) has been used to analyze the degree of crystallization using Perkin Elmer DSC 7.
Figures
SEM images of (a) PVA nanofibers and (b) CNFs.
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SEM images of electrospun nanofibers composed of PVA with (a) 1% wt CNFs and (b) 2% wt CNFs.
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FTIR of the electrospun PVA nanofibers (a) and PVA nanofibers contain CNFs (b).
The electrical conductivity has been increased with increasing the carbon nanofibers in the PVA nanofibers. The electrical conductivity has been increased from 1.01 × 10−5 S/m (for pure PVA) to 2.91 × 10−5 S/m and 16.36 × 10−5 S/m (for PVA nanofibers with 1 wt% and 2 wt% carbon fibers’ content, resp.). The increase of the electrical conductivity of PVA/carbon fiber mat is due to the high conductivity of carbon nanofibers [
Figure
Weight loss versus temperature measured by TGA of PVA nanofibers: PVA: CNFs 1% wt nanofibers and PVA: CNFs 2% wt nanofibers.
First derivative of weight loss versus temperature measured by TGA of PVA nanofibers: PVA: CNFs 1% wt nanofibers and PVA: CNFs 2% wt nanofibers.
Regarding the DSC analysis of the corresponding electrospun fibers, the melting point of PVA is shifted arbitrary from 178, 186.5, and 190°C for PVA and PVA with 1% and 2% CNFs, respectively. The shift of the melting point is attributed to the assistance of carbon nanofibers in increasing the degree of crystallization as they act as nucleating agents in the polymer [
This paper investigates a new nanocomposite composed of both PVA and carbon nanofibers integrated in one electrospun nanofibers web. This technique shows a simple and cheap way to offer a host for CNFs without affecting them using traditional deposition techniques. Our results show that thermal and electrical conductivities of the formed nanofibers have been improved with increasing of the carbon nanofibers content. SEM images show the homogeneity of the formed PVA and carbon nanofibers in one web, with stretched CNFs after the electrospinning process. TGA results show that the degradation of PVA nanofibers is favored by addition of carbon nanofibers due to increase of thermal conductivity. DSC results show that addition of carbon nanofibers within PVA nanofibers increases the degree of crystallization of PVA around 31%. The formed nanocomposite can be used in wide variety of applications including nanoelectronics and nanomedicine.
The authors declare that they have no competing interests.
Nader Shehata carried out the mixing of CNFs within PVA solution to obtain the optimum concentrations applicable for electrospinning process. In addition, Nader Shehata did the electrospinning process with selection of the optimum process parameters. Nabil Madi and Mariam Al-Maadeed both guided Nader Shehata in the overall work in addition to the critical revision of the paper. Ibrahim Hassounah contributed critically in the explanation of the resulted data especially the FTIR spectroscopy analysis. Abdullah Ashraf followed up the different characterizations done in Central Laboratory Unit (CLU) in Qatar University. All authors read and approved the final paper.
This work was funded by a QSTP grant (Award no. 0906). The authors would like to thank Central Laboratory Unit (CLU) in Qatar University for their assistance through the used characterization facilities. Also, the authors are grateful to the financial support of Center of Advanced Materials (CAM) in Qatar University and Virginia Tech Middle East and North Africa (VT-MENA) program in Egypt.