- Email: [email protected]
Investigation of microwave absorbing properties for magnetic nanofiber of polystyrene–polyvinylpyrrolidone
Accepted Manuscript Investigation of microwave absorbing properties for magnetic nanofiber of polystyrene-polyvinylpyrrolidone Seyed Hossein Hosseini, Mahsa Sadeghi PII:
S1567-1739(14)00057-1
DOI:
10.1016/j.cap.2014.02.020
Reference:
CAP 3581
To appear in:
Current Applied Physics
Received Date: 8 November 2013 Revised Date:
3 February 2014
Accepted Date: 22 February 2014
Please cite this article as: S.H. Hosseini, M. Sadeghi, Investigation of microwave absorbing properties for magnetic nanofiber of polystyrene-polyvinylpyrrolidone, Current Applied Physics (2014), doi: 10.1016/j.cap.2014.02.020. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Investigation of microwave absorbing properties for magnetic nanofiber of polystyrene-
1∗
RI PT
polyvinylpyrrolidone
2
M AN U
SC
Seyed Hossein Hosseini , Mahsa Sadeghi
1. Department of Chemistry, Faculty of Science, Islamshahr Branch, Islamic Azad University, Tehran-Iran
TE D
2. Department of Chemistry, Faculty of Science and Engineering, Saveh Branch, Islamic
AC C
EP
Azad university, Saveh, Iran
*Correspondence to: Seyed Hossein Hosseini, Department of Chemistry, Faculty of Science, Islamshahr Branch, Islamic Azad University, Tehran-Iran; Email: [email protected].
1
ACCEPTED MANUSCRIPT
ABSTRACT Aligned magnetic blend of polystyrene-polyvinylpyrrolidone (PS-PVP) nanofibers were prepared by this method. First, polystyrene-polyvinylpyrrolidone (PS-PVP)
RI PT
blend solution in THF was synthesized. Then magnetic of PS-PVP-Fe3O4polyethylene glycol (PEG) was prepared by masking method. Finally, magnetic nanofiber of PS-PVP-Fe3O4- PEG was prepared by electrospinning method, too.
SC
An electric potential difference of 25 kV was applied between the collector and a
M AN U
syringe tip, and the distance between the collector and the tip was 13 cm. Fe3O4 is exhibit various magnetic properties of which the complex permeability and the permittivity, in particular, are important in determining their high frequency characteristics. The magnetic oxide particles and nanofiber of nanometer size were
TE D
characterized by TEM and SEM respectively. The thermal properties of nanofibers were determined by TGA and DSC. The magnetic characterization of the fibers
EP
was also performed by VSM and AFM techniques. On the other hand, nanofiber with diameters ranging from 30 to 40 nm, showing at room temperature, coercive
AC C
field values of around 25 KV and saturation magnetization was 1.1 emu/g. Microwave reflection loss of the sample was tested at 8–12 GHz microwave frequencies and the results showed that magnetic nanofiber possessed the microwave absorbing properties.
Keywords:
Nano-structures;
Polymer 2
(textile)
fiber;
ACCEPTED MANUSCRIPT
Polymer-matrix composites (PMCs); Electrical properties; Magnetic properties
RI PT
1. Introduction Many types of radar absorbing materials are commercially available and, at present, the most cost effective means of shielding radar radiation, controlling
SC
electromagnetic interference and dissipating electrostatic charge is to use either
M AN U
magnetic or dielectric fillers [1] or intrinsically conducting polymers [2]. Magnetic absorption materials made by dispersing magnetic fillers in an insulating matrix continue to play an important role in the investigation and application of microwave absorption materials [3]. As ferrites can avoid the skin effect at high
TE D
frequency and make the electromagnetic wave enter effectively due to their high resistivity, they can attenuate electromagnetic wave efficiently. In addition, for its
EP
higher efficiency and lower cost than that of other materials, they have been among the most popular conventional magnetic fillers. However, for a long period
AC C
of time, much attention about ferrites has been focused on researching microwave absorption properties of new types of ferrites [4,5]. We have reported synthesis of nanocomposites containing some of ferrites compounds and investigated their microwave absorption properties [6,7]. Nanofibers are fibers that have diameter equal to or less than 100 nm. Considering the potential opportunities provided by nanofibers there is an increasing interest in nanofiber technology. Amongst the technologies including the template method 3
ACCEPTED MANUSCRIPT
[8], vapor grown [9], phase sepration [10] and electrospinning has attracted the most recent interest. Electrospinning is a simple and versatile method for generating ultrathin fibers from a rich variety of materials that include polymers,
RI PT
composites and ceramics [11]. In this paper, the main object is to develop a fiber compounds with microwave absorption properties. So we have synthesized magnetic nanofiber with
SC
polystyrene-polyvinylpyrrolidone- Fe3O4-polyethylene glycol, PS-PVP-Fe3O4-
M AN U
PEG.
2. Experimental 2.1. Material
TE D
Polystyrene (Merck chemical Co.) and polyvinylpyrrolidone (Merk chemical Co.) and ferrous sulfate heptahydrate and poly ethylene glycol (Mw: 4000).
EP
Tetrahydrofuran (THF, 99.5%, Duksan chemical Co.) and hydrogen proxide and
AC C
chloroform were used as solvent.
2.2. Measurement of properties An ultrasonic reactor (Bandelin Sonorex Digitec) was used to provide the ultrasonic field. The physical properties of nanofibers and topographic pictures of nanofibers were studied by Atomic Force Microscopy (AFM). Transition electron microscopy (TEM) measurements were performed using PHILIPS EM 208. One drope of the sample solution was deposited on to a copper grid and the excess of 4
ACCEPTED MANUSCRIPT
the droplet was blotted off the grids with a filter paper. The sample was dried under ambient conditions. The Nanoparticles size & morphology were observed by TEM images. The magnetic properties of fibers and magnetic nanoparticles
RI PT
were measured by a Vibrating Sample Magnetometer (VSM), The morphology of fibers was examined by Scanning Electron Microscopy (SEM, PHILIPS XL30). Microwave absorbing properties were measured by a Vector Network Analyzers
M AN U
SC
(Agilent Technologies Inc. 8722) in the 8–12 GHz range at room temperature.
2.3. Synthesis of Fe3O4 Nanoparticles
Fe3O4 Nanoparticles were prepared by Core-Shell system. First, 70 gr of PEG (Mw: 4000) and 3 gr of FeSO4.7H2O were solved in 140 ml of distilled water. This
TE D
solution was transferred to a three-neck flask equipped with a condenser and nitrogen gas inlet and outlet with vigorous stirring for 30 min. Then 20 ml of H2O2
EP
20% was added to the solution. This reaction was performed at 50°C for 6h at pH: 13. The pH of the reaction was set with NaOH 3 M. Then the solution was
AC C
centrifuged. The Fe3O4 magnetic nanoparticles were prepared
2.4. Preparation of the blend solution The polystyrene-polyvinylpyrrolidone (PS-PVP) blend solution was prepared. A 4:1 mole ratio of PS and PVP were dissolved in THF to a final concentration of 11 wt%. The solution was then stirred at room temperature at 1000 rpm for a period of 7 h using a mechanical stirrer, and then filtered through a filter paper to remove 5
ACCEPTED MANUSCRIPT
any particulate matter. Finally, by adding Fe3O4-PEG to the filtered solution, magnetic PS-PVP-Fe3O4-PEG solution was prepared, which was then stirred for a
RI PT
period of 2 h. This solution was made using the following procedure.
2.5. Electrospinning
Electrospinning, have only 6 or 7 molecules across. The PS-PVP blend and PS-
SC
PVP-Fe3O4-PEG nanofibers were synthesized on a aluminum electrode
M AN U
(10cm×10cm). An electric potential difference of 25 kV was applied between the collector and a syringe tip, and the distance between the collector and the tip was 13 cm. Although we tried to fabricate the same number of blend nanofibers as composite nanofibers on the electrode, a slightly different number of both fibers
TE D
were generated and collected.
EP
3. Results and discussion
The electrospinning process has been documented using a variety of fiber forming
AC C
polymers. By choosing a suitable polymer and solvent system, nanofibers with diameters in the range of 40-2000 nm be made. Magnetization studies have shown that the magnetic PS-PVP-Fe3O4-PEG nanofibers exibit superparamagnetic behavior and shows no hysteresis. The magnetic characterization of the fibers was performed by Vibrating Sample Magnetometer (VSM) and Atomic Force Microscopy techniques. The magnetization curve of PS-PVP-Fe3O4-PEG nanofibers is presented in Figure 1. An electric potential difference of 10 kV was 6
ACCEPTED MANUSCRIPT
applied between the collector and a syringe tip, and the distance between the collector and the tip was 13 cm. On the other hand, nanofiber with diameters ranging from 30 to 40 nm, showing at room temperature, coercive field values
RI PT
was around 25 kV and saturation magnetization was (M r =1.1 emu/g). In our study, the physical properties of PS-PVP-Fe3O4-PEG nanofibers were exhibit by Atomic Force Microscopy (AFM) with different size. The dark spots
SC
that were shown like tops are magnetic nanoparticles Fe3O4 and light area of
M AN U
polymer are base and are PS-PVP nanofibers (Figure 2).
The histogram nanofibers of polystyrene and magnetic nanoparticles of Fe3O4PEG have been shown in Figure 3. The height of the peak shows the size of nanoparticles that is scattered in polymeric-bed.
TE D
Figure 4 shows the size of MNPs of Fe3O4-PEG were almost 61.5 nm. The TEM images show that size of nanoparticles Fe3O4 were about 10-50 nm.
EP
The SEM images of PS-PVP (w/w 4:1) and PS-PVP-Fe3O4-PEG nanofibers were shown in Figures 5 and 6. The average of diameter of nanofibers is about 100-150
AC C
nm. In the current study nanoparticle are microhollow spherical and the diameter of each hole is about 2 to 5 micrometers.
3.1. Reflection loss Different Fe doped Fe3O4 have the similar change for the dielectric and the magnetic spectra which suggests that their electromagnetism loss mechanism should be the same. Now, the electromagnetism loss mechanism of the materials 7
ACCEPTED MANUSCRIPT
will be explained by the characteristic change of loss factor for sample. A novel phenomenon is discovered that the electromagnetic loss factor has suddenly a step change at a certain frequency. Loss factor is depended to Fe value. When Fe
RI PT
concentration is increased, there is a sharp increase of loss factor [12]. The energy state of anti-ferromagnetic clusters could be linked with the content, which affects the potential barrier height between ferromagnetic clusters and anti-ferromagnetic
SC
clusters [13]. Besides, the microwave loss may also come from the resistive part
M AN U
[14]. The lower resistivity may arouse larger dielectric losses.
In the other hands, according to transmission line theory, the reflection loss (RL) of electromagnetic radiation, under normal wave incidence at the surface of a single-layer material backed by a perfect conductor can be given by
TE D
is the characteristic impedance of free space,
EP
where
(1)
(2)
AC C
Zin is the input impedance at free space and materials interface: (3)
where µr and εr are the complex permeability and permittivity of the composite medium respectively, which can be calculated from the complex scatter parameters, c is the light velocity, f is the frequency of the incidence electromagnetic wave and t is the thickness of composites. The impedance 8
ACCEPTED MANUSCRIPT
matching condition is given by Zin = Z0 to represent the perfect absorbing properties. In this research, nanofiber was pasted on glass or aluminum plate with the area of
RI PT
10mm×10mm as the test plate. The microwave absorbing properties of the nanofiber with the 20 w.% Fe3O4 NPs at 1 mm nanofiber thicknesses were investigated by using vector network analyzers in the frequency range of 8 –
SC
12GHz. Figure 7 shows the variation of reflection loss versus frequency
M AN U
determined from PS-PVP-Fe3O4- PEG. For nanofiber of PS-PVP-Fe3O4- PEG with the coating thickness of 1 mm the reflection loss values less than -11 dB were obtained in the frequency of 8–14 GHz. Its value of minimum reflection losses are -11 and -8 dB at the frequencies of 10 and 12 GHz, respectively. The absorbing
TE D
bandwidth at -10 dB is 0.3 GHz.
Such suitable conductivity and magnetic transformation will be beneficial to the
EP
materials absorbing microwave. Further studies on the relationship among the absorbing properties, electrical conductivity and magnetic domain structures of the
AC C
compounds are in process.
4. Conclusion
Fe3O4-PEG solution was added into blend precursor solution to improve the magnetic and morphology properties and distribution of diameter of PS-PVPFe3O4-PEG nanofibers. The average of diameter of nanofibers is about 100-150 nm and microhollow spherical for nanoparticles. This nanofiber is good candidate 9
ACCEPTED MANUSCRIPT
for microwave absorbing materials. The value of minimum reflection loss for the nanofiber with 20 w.% Fe3O4 NPs is approximately −11 dB with a thickness of 1 mm at the frequency of 10 GHz.
RI PT
References
[1] Z.G. Fan, G.H. Luo, Z.G. Zhang, L. Zhou, F. Wei, Mater. Sci. Eng. B 132
SC
(2006) 85.
[2] M.A. Soto-Oviedo, O.A. Arau´ jo, R. Faez, M.C. Rezende, M.A.De Paoli,
M AN U
Synth. Met. 156 (2006) 1249.
[3] M.P. Horvath, J. Magn. Magn. Mater. 215 (2000) 171. [4] W.Y. Fu, S.K. Liu, W.H. Fan, H.B. Yang, X.F. Pang, J. Xu, G.T. Zou, J. Magn. Magn. Mater. 316 (2007) 54.
840.
TE D
[5] G.H. Mu, N. Chen, X.F. Pan, H.G. Shen, M.Y. Gu, Mater. Lett. 62 (2008)
EP
[6] S.H. Hosseini, A. Asadnia, International Journal of Physical Sciences, 8
AC C
(22), (2013) 1209.
[7] S.H. Hosseini, M. Moloudi, Synthesis and Reactivity in Inorganic, MetalOrganic, and Nano-Metal Chemistry, 43, (6),(2013) 671.
[8] Z. Libor, and Q. Zhang, Material Chemistry and physics, 114 (2009) 902. [9] E. Esmaeili, A. Khodadadi, and Y. Mortazavi, Journal of the European Ceramic Society, 29, (2009) 1061.
10
ACCEPTED MANUSCRIPT
[10]
Y-W Ju, J-H Park, H-R Jung, S-J Cho, and W-J Lee, Composites
Science and Technology, 68 (2008) 1704. [11]
H. Wu, R. Zhang, X. Liu, D. Lin and, W. Pan, Chem. Mater., 19,
[12]
RI PT
(14), (2007) 3506. L. Chen, C. Lu, Y. Zhao, Y. Ni, J. Song, Z. Xu, Journal of Alloys
and Compounds 509 (2011) 8756.
K. Zhou, D. Wang, K. Huang, Trans. Nonferr. Metal. Soc. China 17
SC
[13]
[14]
M AN U
(2007) 1294.
G. Li, G. Hu, H. Zhou, et al., Mater. Chem. Phys. 75 (2002) 101.
TE D
Figure Titles:
Figure 1. Magnetization vs. applied field plot for PS-PVP-Fe3O4-PEG nanofibers
EP
at room temperature
Figure 2. AFM images of electrospun nanofibers of PS-PVP-Fe3O4-PEG
AC C
Figure 3. Magnetic histogram of Fe3O4-PEG nanofibers at room temperature Figure 4. TEM images of electrospun nanofibers of PS-PVP-Fe3O4-PEG Figure 5. SEM images of PS-PVP (w/w 4:1) nanofibers Figure 6. SEM images of electrospun nanofibers of PS-PVP-Fe3O4-PEG Figure 7. Frequency dependence of RL for the PS-PVP-Fe3O4-PEG
11
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Highlights
EP
TE D
M AN U
SC
RI PT
We report a PS-PVP-Fe3O4-PEG nanofiber with magnetic property PS-PVP-Fe3O4-PEG nanofiber is good candidate as microwave absorbing materials
AC C
• •
S1567-1739(14)00057-1
DOI:
10.1016/j.cap.2014.02.020
Reference:
CAP 3581
To appear in:
Current Applied Physics
Received Date: 8 November 2013 Revised Date:
3 February 2014
Accepted Date: 22 February 2014
Please cite this article as: S.H. Hosseini, M. Sadeghi, Investigation of microwave absorbing properties for magnetic nanofiber of polystyrene-polyvinylpyrrolidone, Current Applied Physics (2014), doi: 10.1016/j.cap.2014.02.020. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Investigation of microwave absorbing properties for magnetic nanofiber of polystyrene-
1∗
RI PT
polyvinylpyrrolidone
2
M AN U
SC
Seyed Hossein Hosseini , Mahsa Sadeghi
1. Department of Chemistry, Faculty of Science, Islamshahr Branch, Islamic Azad University, Tehran-Iran
TE D
2. Department of Chemistry, Faculty of Science and Engineering, Saveh Branch, Islamic
AC C
EP
Azad university, Saveh, Iran
*Correspondence to: Seyed Hossein Hosseini, Department of Chemistry, Faculty of Science, Islamshahr Branch, Islamic Azad University, Tehran-Iran; Email: [email protected].
1
ACCEPTED MANUSCRIPT
ABSTRACT Aligned magnetic blend of polystyrene-polyvinylpyrrolidone (PS-PVP) nanofibers were prepared by this method. First, polystyrene-polyvinylpyrrolidone (PS-PVP)
RI PT
blend solution in THF was synthesized. Then magnetic of PS-PVP-Fe3O4polyethylene glycol (PEG) was prepared by masking method. Finally, magnetic nanofiber of PS-PVP-Fe3O4- PEG was prepared by electrospinning method, too.
SC
An electric potential difference of 25 kV was applied between the collector and a
M AN U
syringe tip, and the distance between the collector and the tip was 13 cm. Fe3O4 is exhibit various magnetic properties of which the complex permeability and the permittivity, in particular, are important in determining their high frequency characteristics. The magnetic oxide particles and nanofiber of nanometer size were
TE D
characterized by TEM and SEM respectively. The thermal properties of nanofibers were determined by TGA and DSC. The magnetic characterization of the fibers
EP
was also performed by VSM and AFM techniques. On the other hand, nanofiber with diameters ranging from 30 to 40 nm, showing at room temperature, coercive
AC C
field values of around 25 KV and saturation magnetization was 1.1 emu/g. Microwave reflection loss of the sample was tested at 8–12 GHz microwave frequencies and the results showed that magnetic nanofiber possessed the microwave absorbing properties.
Keywords:
Nano-structures;
Polymer 2
(textile)
fiber;
ACCEPTED MANUSCRIPT
Polymer-matrix composites (PMCs); Electrical properties; Magnetic properties
RI PT
1. Introduction Many types of radar absorbing materials are commercially available and, at present, the most cost effective means of shielding radar radiation, controlling
SC
electromagnetic interference and dissipating electrostatic charge is to use either
M AN U
magnetic or dielectric fillers [1] or intrinsically conducting polymers [2]. Magnetic absorption materials made by dispersing magnetic fillers in an insulating matrix continue to play an important role in the investigation and application of microwave absorption materials [3]. As ferrites can avoid the skin effect at high
TE D
frequency and make the electromagnetic wave enter effectively due to their high resistivity, they can attenuate electromagnetic wave efficiently. In addition, for its
EP
higher efficiency and lower cost than that of other materials, they have been among the most popular conventional magnetic fillers. However, for a long period
AC C
of time, much attention about ferrites has been focused on researching microwave absorption properties of new types of ferrites [4,5]. We have reported synthesis of nanocomposites containing some of ferrites compounds and investigated their microwave absorption properties [6,7]. Nanofibers are fibers that have diameter equal to or less than 100 nm. Considering the potential opportunities provided by nanofibers there is an increasing interest in nanofiber technology. Amongst the technologies including the template method 3
ACCEPTED MANUSCRIPT
[8], vapor grown [9], phase sepration [10] and electrospinning has attracted the most recent interest. Electrospinning is a simple and versatile method for generating ultrathin fibers from a rich variety of materials that include polymers,
RI PT
composites and ceramics [11]. In this paper, the main object is to develop a fiber compounds with microwave absorption properties. So we have synthesized magnetic nanofiber with
SC
polystyrene-polyvinylpyrrolidone- Fe3O4-polyethylene glycol, PS-PVP-Fe3O4-
M AN U
PEG.
2. Experimental 2.1. Material
TE D
Polystyrene (Merck chemical Co.) and polyvinylpyrrolidone (Merk chemical Co.) and ferrous sulfate heptahydrate and poly ethylene glycol (Mw: 4000).
EP
Tetrahydrofuran (THF, 99.5%, Duksan chemical Co.) and hydrogen proxide and
AC C
chloroform were used as solvent.
2.2. Measurement of properties An ultrasonic reactor (Bandelin Sonorex Digitec) was used to provide the ultrasonic field. The physical properties of nanofibers and topographic pictures of nanofibers were studied by Atomic Force Microscopy (AFM). Transition electron microscopy (TEM) measurements were performed using PHILIPS EM 208. One drope of the sample solution was deposited on to a copper grid and the excess of 4
ACCEPTED MANUSCRIPT
the droplet was blotted off the grids with a filter paper. The sample was dried under ambient conditions. The Nanoparticles size & morphology were observed by TEM images. The magnetic properties of fibers and magnetic nanoparticles
RI PT
were measured by a Vibrating Sample Magnetometer (VSM), The morphology of fibers was examined by Scanning Electron Microscopy (SEM, PHILIPS XL30). Microwave absorbing properties were measured by a Vector Network Analyzers
M AN U
SC
(Agilent Technologies Inc. 8722) in the 8–12 GHz range at room temperature.
2.3. Synthesis of Fe3O4 Nanoparticles
Fe3O4 Nanoparticles were prepared by Core-Shell system. First, 70 gr of PEG (Mw: 4000) and 3 gr of FeSO4.7H2O were solved in 140 ml of distilled water. This
TE D
solution was transferred to a three-neck flask equipped with a condenser and nitrogen gas inlet and outlet with vigorous stirring for 30 min. Then 20 ml of H2O2
EP
20% was added to the solution. This reaction was performed at 50°C for 6h at pH: 13. The pH of the reaction was set with NaOH 3 M. Then the solution was
AC C
centrifuged. The Fe3O4 magnetic nanoparticles were prepared
2.4. Preparation of the blend solution The polystyrene-polyvinylpyrrolidone (PS-PVP) blend solution was prepared. A 4:1 mole ratio of PS and PVP were dissolved in THF to a final concentration of 11 wt%. The solution was then stirred at room temperature at 1000 rpm for a period of 7 h using a mechanical stirrer, and then filtered through a filter paper to remove 5
ACCEPTED MANUSCRIPT
any particulate matter. Finally, by adding Fe3O4-PEG to the filtered solution, magnetic PS-PVP-Fe3O4-PEG solution was prepared, which was then stirred for a
RI PT
period of 2 h. This solution was made using the following procedure.
2.5. Electrospinning
Electrospinning, have only 6 or 7 molecules across. The PS-PVP blend and PS-
SC
PVP-Fe3O4-PEG nanofibers were synthesized on a aluminum electrode
M AN U
(10cm×10cm). An electric potential difference of 25 kV was applied between the collector and a syringe tip, and the distance between the collector and the tip was 13 cm. Although we tried to fabricate the same number of blend nanofibers as composite nanofibers on the electrode, a slightly different number of both fibers
TE D
were generated and collected.
EP
3. Results and discussion
The electrospinning process has been documented using a variety of fiber forming
AC C
polymers. By choosing a suitable polymer and solvent system, nanofibers with diameters in the range of 40-2000 nm be made. Magnetization studies have shown that the magnetic PS-PVP-Fe3O4-PEG nanofibers exibit superparamagnetic behavior and shows no hysteresis. The magnetic characterization of the fibers was performed by Vibrating Sample Magnetometer (VSM) and Atomic Force Microscopy techniques. The magnetization curve of PS-PVP-Fe3O4-PEG nanofibers is presented in Figure 1. An electric potential difference of 10 kV was 6
ACCEPTED MANUSCRIPT
applied between the collector and a syringe tip, and the distance between the collector and the tip was 13 cm. On the other hand, nanofiber with diameters ranging from 30 to 40 nm, showing at room temperature, coercive field values
RI PT
was around 25 kV and saturation magnetization was (M r =1.1 emu/g). In our study, the physical properties of PS-PVP-Fe3O4-PEG nanofibers were exhibit by Atomic Force Microscopy (AFM) with different size. The dark spots
SC
that were shown like tops are magnetic nanoparticles Fe3O4 and light area of
M AN U
polymer are base and are PS-PVP nanofibers (Figure 2).
The histogram nanofibers of polystyrene and magnetic nanoparticles of Fe3O4PEG have been shown in Figure 3. The height of the peak shows the size of nanoparticles that is scattered in polymeric-bed.
TE D
Figure 4 shows the size of MNPs of Fe3O4-PEG were almost 61.5 nm. The TEM images show that size of nanoparticles Fe3O4 were about 10-50 nm.
EP
The SEM images of PS-PVP (w/w 4:1) and PS-PVP-Fe3O4-PEG nanofibers were shown in Figures 5 and 6. The average of diameter of nanofibers is about 100-150
AC C
nm. In the current study nanoparticle are microhollow spherical and the diameter of each hole is about 2 to 5 micrometers.
3.1. Reflection loss Different Fe doped Fe3O4 have the similar change for the dielectric and the magnetic spectra which suggests that their electromagnetism loss mechanism should be the same. Now, the electromagnetism loss mechanism of the materials 7
ACCEPTED MANUSCRIPT
will be explained by the characteristic change of loss factor for sample. A novel phenomenon is discovered that the electromagnetic loss factor has suddenly a step change at a certain frequency. Loss factor is depended to Fe value. When Fe
RI PT
concentration is increased, there is a sharp increase of loss factor [12]. The energy state of anti-ferromagnetic clusters could be linked with the content, which affects the potential barrier height between ferromagnetic clusters and anti-ferromagnetic
SC
clusters [13]. Besides, the microwave loss may also come from the resistive part
M AN U
[14]. The lower resistivity may arouse larger dielectric losses.
In the other hands, according to transmission line theory, the reflection loss (RL) of electromagnetic radiation, under normal wave incidence at the surface of a single-layer material backed by a perfect conductor can be given by
TE D
is the characteristic impedance of free space,
EP
where
(1)
(2)
AC C
Zin is the input impedance at free space and materials interface: (3)
where µr and εr are the complex permeability and permittivity of the composite medium respectively, which can be calculated from the complex scatter parameters, c is the light velocity, f is the frequency of the incidence electromagnetic wave and t is the thickness of composites. The impedance 8
ACCEPTED MANUSCRIPT
matching condition is given by Zin = Z0 to represent the perfect absorbing properties. In this research, nanofiber was pasted on glass or aluminum plate with the area of
RI PT
10mm×10mm as the test plate. The microwave absorbing properties of the nanofiber with the 20 w.% Fe3O4 NPs at 1 mm nanofiber thicknesses were investigated by using vector network analyzers in the frequency range of 8 –
SC
12GHz. Figure 7 shows the variation of reflection loss versus frequency
M AN U
determined from PS-PVP-Fe3O4- PEG. For nanofiber of PS-PVP-Fe3O4- PEG with the coating thickness of 1 mm the reflection loss values less than -11 dB were obtained in the frequency of 8–14 GHz. Its value of minimum reflection losses are -11 and -8 dB at the frequencies of 10 and 12 GHz, respectively. The absorbing
TE D
bandwidth at -10 dB is 0.3 GHz.
Such suitable conductivity and magnetic transformation will be beneficial to the
EP
materials absorbing microwave. Further studies on the relationship among the absorbing properties, electrical conductivity and magnetic domain structures of the
AC C
compounds are in process.
4. Conclusion
Fe3O4-PEG solution was added into blend precursor solution to improve the magnetic and morphology properties and distribution of diameter of PS-PVPFe3O4-PEG nanofibers. The average of diameter of nanofibers is about 100-150 nm and microhollow spherical for nanoparticles. This nanofiber is good candidate 9
ACCEPTED MANUSCRIPT
for microwave absorbing materials. The value of minimum reflection loss for the nanofiber with 20 w.% Fe3O4 NPs is approximately −11 dB with a thickness of 1 mm at the frequency of 10 GHz.
RI PT
References
[1] Z.G. Fan, G.H. Luo, Z.G. Zhang, L. Zhou, F. Wei, Mater. Sci. Eng. B 132
SC
(2006) 85.
[2] M.A. Soto-Oviedo, O.A. Arau´ jo, R. Faez, M.C. Rezende, M.A.De Paoli,
M AN U
Synth. Met. 156 (2006) 1249.
[3] M.P. Horvath, J. Magn. Magn. Mater. 215 (2000) 171. [4] W.Y. Fu, S.K. Liu, W.H. Fan, H.B. Yang, X.F. Pang, J. Xu, G.T. Zou, J. Magn. Magn. Mater. 316 (2007) 54.
840.
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Figure Titles:
Figure 1. Magnetization vs. applied field plot for PS-PVP-Fe3O4-PEG nanofibers
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Figure 2. AFM images of electrospun nanofibers of PS-PVP-Fe3O4-PEG
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Figure 3. Magnetic histogram of Fe3O4-PEG nanofibers at room temperature Figure 4. TEM images of electrospun nanofibers of PS-PVP-Fe3O4-PEG Figure 5. SEM images of PS-PVP (w/w 4:1) nanofibers Figure 6. SEM images of electrospun nanofibers of PS-PVP-Fe3O4-PEG Figure 7. Frequency dependence of RL for the PS-PVP-Fe3O4-PEG
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We report a PS-PVP-Fe3O4-PEG nanofiber with magnetic property PS-PVP-Fe3O4-PEG nanofiber is good candidate as microwave absorbing materials
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