Fabrication and characterization of magnetic nanocomposites by electric fields assisted electrospinning

Song, Y., et al.: Fabrication and Characterization of Magnetic … THERMAL SCIENCE: Year 2019, Vol. 23, No. 4, pp. 2365-2372 2365 FABRICATION AND CHARACTERIZATION OF MAGNETIC NANOCOMPOSITES BY ELECTRIC FIELDS ASSISTED ELECTROSPINNING by Yanhua SONG, Lan XU *, and Jianhua SUI * National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, China Original scientific paper https://doi.org/10.2298/TSCI1904365S A magnetic and electric fields assisted electrospinning, in which a charged copper ring was placed between the needle and the two paralleled magnets receivers, was presented to produce aligned polyacrylonitrile/graphene/Fe3O4 (PAN/Gr/Fe3O4) magnetic composite nanofibers. Characterizations of the magnetic composite nanofibers were investigated by means of scanning electron microscopy, Fourier transform infrared spectroscopy, high-resistance meter, and other methods. The results showed that Gr and Fe3O4 nanoparticles are suitable additives to improve alignment degree and conductive properties of nanofibers. Key words: graphene, aligned nanofibers, magnetic nanocomposites, electrospinning, Fe3O4 nanoparticles Introduction In recent years, polymeric nanocomposites embedded nanoparticles with properties of electricity and magnetism have attracted the great interest of many researchers due to their wide applications in biomedical [1, 2], electrochemical [3], microwave absorption [4], and optical materials [5]. Electrospinning (ES) is an efficient method for the fabrication of magnetic composite nanofibers (MCNF) [6]. However, the obtained nanocomposites usually show random structures, which could not satisfy the application requirement. Therefore, it is desirable to generate aligned MCNF to broaden the application areas [7]. Graphene (Gr) is a 2-D structure and one-atom thickness, and has remarkable mechanical, electrical, thermal and magnetic properties [8], and it is thought to be an excellent material of electronic devices [9], gas sensors [10], and electrochemical devices. The Fe3O4 nanoparticles have special advantages of high theoretical capacity, low cost and unique superparamagnetism. Therefore, Fe3O4 and its composites have a wide range of applications in electrochemical, medical [11], microwave absorption [12], and environmental protection [13] materials. Polyacrylonitrile (PAN) is a favorable electrical material and can be applied as the basis material to fabricate electrochemical devices. The Fe3O4/carbon/polymer composites have features of relatively light quality, special magnetism, outstanding electricity and wide absorption band. In this study, aligned PAN/Gr/Fe3O4 MCNF with the different Fe3O4 concentrations were prepared successfully by a magnetic and electric fields assisted electrospinning –––––––––––––– * Corresponding authors, e-mail: , 2366 Song, Y., et al.: Fabrication and Characterization of Magnetic … THERMAL SCIENCE: Year 2019, Vol. 23, No. 4, pp. 2365-2372 (MEFAE), in which a charged copper ring was placed between the needle and the two paralleled magnets receivers. The apparatus was shown in fig. 1. Morphologies, crystalline structures and conductive properties of the MCNF were investigated by SEM, energy dispersive spectrometer (EDS), FTIR spectroscopy, XRD and high-resistance meter. The results indicated the combination of magnetic and electric fields could improve the alignment degree and conductive property of PAN/Gr/Fe3O4 MCNF produced. Experimental Materials The PAN powder, 150,000 g/mol, was supplied by Beijing Lark Branch Co. Ltd. N,N-dimethylformamide (DMF) (analytical reagent) was purchased from Shanghai Chemical Reagent Co. Ltd. Graphene nanoparticles Figure 1. Experimental set-up for the MEFAE were purchased from Shanghai Aladdin Biochemical Technology Co. Ltd. (thickness: 6-8 nm, width: 5 μm). Fe3O4 nanoparticles (purity: ≧99.5%, length: 20 nm) were supplied by Shanghai Maclin biochemical technology Co. Ltd. All materials were used without any further purification. Preparation of spinning solution All concentration measurements were done in weight by weight to solution (w/w). Diffeent weights of Fe3O4 and 0.5 wt.% Gr were dispersed in DMF using an ultrasonic cleaner (SL-5200DT, Nanjing Shunliu Instrument Co. Ltd., China) for 4 hours at 25 ±2 °C (room temperature). Then the ES solution was prepared by dissolving 8 wt.% of PAN in Gr/Fe3O4/DMF solution under magnetic stirring for 24 hours at room temperature (25±2 ºC) until it became homogeneous. The calculated Fe3O4 concentrations for each component of the various samples were 0, 0.5, 1, 1.5, 2.0, and 2.5 wt.%. Fabrication of highly aligned PAN/Gr/Fe3O4 MCNF Aligned PAN/Gr/Fe3O4 MCNF with the Fe3O4 concentrations ranged from 0 wt.% to 2.5 wt.% were prepared directly by MEFAE at room temperature and a relative humidity 50%. The spinning voltage was 15 kV, the ring voltage was 5 kV. The spinning distance was 18 cm and the distance of two magnets (77×57×17 cm) was 4 cm, the ring was 21 cm in diameter. The flow rate was 0.8 mL/h. Measurements and characterizations The morphologies of aligned PAN/Gr/Fe3O4 MCNF were examined by a SEM (Hitachi S-4800, Japan) at acceleration voltage of 3 kV. The MCNF structure and the interactions of polymer and additives were investigated through FTIR spectroscopy (Nicolet5700, Thermo Song, Y., et al.: Fabrication and Characterization of Magnetic … THERMAL SCIENCE: Year 2019, Vol. 23, No. 4, pp. 2365-2372 2367 Nicolet Company, USA). The XRD (Philips X’Pert-Pro MPD, Netherlands) analyses were performed to elucidate the crystalline structure of MCNF with diffraction angle 2θ range of 5°-80°. Energy dispersive Spectrometer (EDS, Japan) fitted to TM3030 SEM was utilized to prove the existence of Fe3O4. The surface resistance was measured by high-resistance meter (ZC36, Shanghai, China) at room temperature and ambient condition. Results and discussion Morphological characterization of aligned PAN/Gr/Fe3O4 nanocomposites Figure 2 shows the morphologies pictures, 2(a), and the diameter distribution, 2(b), of MCNF. It could be seen that the diameters of PAN/Gr/Fe3O4 MCNF decreased sharply compared to the PAN/Gr nanofibers. It was possible that the spinning solution was magnetized due to the addition of Fe3O4 nanoparticles. The magnetic field force could decrease the energy loss much more of the charged jet in the MEFAE process than that without Fe3O4 nanoparticles [14]. However, with the increase of the Fe3O4 contents the diameters of MCNF increased and their surface became rough, which could be related to the aggregation of Fe3O4. Besides, the diameter of MCNF obtained by MEFAE was smaller than that by ES due to the charged ring, which would increase the kinetic energy of the moving jet, accelerate the downward movement of the jet, and shrink the radius of whipping circle [15]. The relationship between the contents of Fe3O4 nanoparticles and the average diameters of MCNF was shown in ta (...truncated)