Supporting Information
Magnetite-Embedded Electrospun Polyacrylonitrile-Based Carbon Fibers:
Synthesis and Electromagnetic Wave Absorption Characteristics
Ying Yang1,2 Zhen Guo3 Huan Zhang1 Daqing Huang3 Jialin Gu3 Zhenghong Huang3
Feiyu Kang3 T Alan Hatton1 Gregory C Rutledge1
1
Department of Chemical Engineering, Massachusetts Institute of Technology, 77
Massachusetts Avenue, Cambridge, MA 02139 (USA)
2
Department of Electrical Engineering, Tsinghua University, Beijing, 100084, China.
3
Department of Materials Science and Engineering, Tsinghua University,
Beijing,100084 China
A. Solution Rheology.
Composite solutions prepared with Fe3O4 nanoparticles exhibit higher zero-shear-rate
viscosity and sharper shear thinning behavior than do pure PAN solutions. Shear
deformation is the most common mode of polymer deformation, but stretching flow
occurs in fiber spinning, blow molding, film blowing, injection molding, and coating
of films. So, extensional deformation [1] came to the fore in the last two to three
decades. Extensional viscosity is the measure of the resistance of a material subjected
to stretching flow and is identified by the extensional stress measured in the test
divided by the constant strain rate. Fig. S1(a) shows shear viscosity measured in a
Thermo Scientific HAAKE VT550 Viscometer viscometer for several solutions of PAN
in DMF with various amounts of Fe3O4 added.
Fig S1(b) shows the variation with
time of the filament diameter in the CaBER extensional rheometer for several
solutions of PAN in DMF with various amounts of Fe3O4 added. The addition of
iron oxide serves to increase both the shear viscosity and the relaxation time (obtained
from the inverse of the slope of diameter vs time in Fig S1(b)) of the PAN/DMF
solution.
(a)
(b)
Fig. S1 Rheological behavior (a)viscosity vs. shear rate; and (b) extensional
viscosity
B. Magnetic hysteresis loops
Fig. S2 Magnetic hysteresis loops at different particle loadings in Fe3O4/PAN
composite fibers at room temperature. Inset shows linear correlation of saturation
magnetization with Fe3O4 loading.
C. Calculation of concentration of magnetic nanoparticles in carbon fiber
For purpose of this calculation, we assume that all of the nanoparticles were Fe3O4. If
the Fe3O4 were reduced to Fe or Fe3C, the weight % would be smaller than that
calculated under this assumption, so that the estimates calculated here serve as upper
bounds.
Based on the TGA results in Figure S3, it can be seen that around 30% of the weight was
left after heating to 800°C.
The actual weight loss for each sample upon heating to
800°C is presented in Table S1.
Fig. S3. The degradation trends in nitrogen environments for as-electrospun Fe3O4/PAN
fibers by thermogravimetic analysis Thermogravimetric analysis (TGA) was conducted
using a Q5000IR thermogravimetric analyzer (TA Instruments, Inc.). Samples were
subjected to heating scans (3°C/min) in a temperature ramp mode..
Table S1 The degradation trends in nitrogen environments for as-electrospun Fe3O4/PAN
fibers by TGA
Fe3O4 loading in PAN
0%
2%
7%
17%
Weight lost
70%
70%
83%
64%
Based on this information, the content of iron in the form of iron oxide in each sample
of carbon fibers was estimated as follows.
(1) For 1 wt % sample (nominally 2% Fe3O4/C fibers);
1 g 2% Fe3O4/PAN fibers produces ~0.3g nominally 2% Fe3O4/C fibers
The real concentration Fe3O4 in carbon fiber should then be
0.02g/0.3g=6.7 wt%
The concentration of Fe3O4 in EM absorber is then 1wt%*6.7wt%=0.067wt%
(2) For 5 wt % sample (nominally 2% Fe3O4/C fibers)
1 g 2% Fe3O4/PAN fibers produces ~0.3g nominally 2% Fe3O4/C fibers
The concentration of Fe3O4 in EM absorber should then be 5wt%*6.7wt%=0.33 wt%
(3) For 5 wt % sample (nominally 17% Fe3O4/C fibers)
1 g 17% Fe3O4/PAN fibers produces ~0.36g nominally 17% Fe3O4/C fibers
The real concentration Fe3O4 in carbon fiber should then be 0.17/0.36=0.47 wt%
The concentration of Fe3O4 in EM absorber should then be 5%*47%=2.4 wt%
References：
[1] Chen L, Bromberg L, Hatton TA, and Rutledge GC. Electrospun cellulose acetate
fibers containing chlorhexidine as a bactericide. Polymer 2008;49(5):1266-1275