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PHYSICS, CHEMISTRY AND APPLICATION OF NANOSTRUCTURES, 2015
SYNTHESIS AND CHARACTERIZATION OF FCCO
NANOPARTICLES WITH DIFFERENT FC:CO RATIO
S. A VOROBYOVA
Research lrt,rtitute.l'or Phltsigul Chem.ical Problems oJ BSU
Leningradskaya 14, 220030 Minsk, Belarus
jenaenta@tut.by
FeCo nanoparticles with calculated mass content FesoCoso, FezsCozs and Fez:Cozs w€t€
obtained in water solution in a simple chemical synthesis. According to the XRD
analysis all samples contain FeCo alloy ancl the products of the oxidation of metals
(FeO(OH), CoFezO+, FeO). TEM investigations show that samples have bimodal
distributions of the particle size.
1. Introduction
Magnetic FcCo nanomatcrials havc various tcchnical and industrial applications
e.g., biomcdical application. magnctie rcsonance irnaging, high density data
Storage, microwave absorption, electrocatalytic actiVity, drug delivery, and
tumor-specific photothermal therapy Ll-3.] The synthesis of FeCo includes
sol-gel method, hydrogen reduction, thermal decomposition, thermolysis,
borohydride reduction, co-precipitation, alkalide reduction, etc. l4l. It is
necessary to find out the simple method of FeCo nanoparticles synthesis to
crontrol thc composition and particlc sizc, as wcll as their magnctic properties
tsl In this paper, we report a simple chemical synthesis of FeCo nanoparticles
in water solution using sodium borohydride as a reducing agent. Samples with
different mass content of metals were obtained and analyzed by transmission
electron microscopy and X-ray diffraction (XRD).
2. Experimental details
The solution of 1.21 g of cobalt chloride hexahydrate in 15 ml of distilled water
and 1.45 g of ferric (III) chloride hexahydrate in 15 ml of distilled water was
obtained and was heated on the water bath to 70'C under vigorous stirring.
Then, 0.99 g of sodium borohydride and 0.26 g of sodium hydroxide in 20 ml of
distilled warer were injected into the solution (9 ml/min). After that, the system
was allowed to stir for an additional 5 min. Then it was cooled to 25 oC and
placed on a magnet. The supernatant was removed and the resulting product was
washed with distilled water by decantation until pH = 8, filtered on a Buchner
funnel and dried in a vacuum desiccator over silica gel. During the whole
303
304
synthesis, argon was passed through the reaction mixture. As a result, composite
nanoparticles Fe56Co5s were obtained.
To synthesize sample Fe25Co7 s | .82 g of cobalt chloride hexahydrate, 0,73 g
of f-erric (III) chloride hexahydrate, 0.88 g of sodium borohydride and 0.23 g of
sodium hydroxide were used. To prepare Fe75Co25, 0.61 g of cobalt chloride
hexahydrate, 2.18 g of ferric (III) chloride hexahydrate, I .10 g of sodium
borohydride and 0.29 g of sodium hydroxide were utilized.
Dispersion and phase composition of the samples were investigated by
transmission elcctron microscopy (TIIM) and XRD. TEM invcstigations werc
carricd out with an elcctron microscopc LEO-906. The samplcs werc prepared in
the lbllowing way: the obtaincd prccipitatc was redispersed for l0 rnin in ethanol
in an ultrasonic bath SONOREX RK-52, and then a drop of the resulting colloid
was placed on a copper grid coated with carbon film and dried in air.
X-ray microanalyzer (EDX) RONTEG has been applied to investigate the
elemental composition of nanoparticles.
XRD of samplcs was str,rdied with X-ray diffractometer DRON-3 using
CoKs-radiation in the angular range 20 = 10-80 deg.
3. Results and discussion
Three samples of FeCo nanoparticles were obtained with the following
calculated mass content lresoCo5e, F-e,5Cors &fld Fe75Co25. First two samples are
black I-inc-dispcrsed powdcrs with satisl'actor"y rnagnetic propertics, The last one
is the brown powder, has bad magnetic properties, indicating oxidation of iron.
The results of elemental analysis are in Table l. It is clearly seen that all the
samples have mass content of iron below the calculated value. It can occur due
to the fact that part of the resulting iron nanoparticles reduce some amount of
cobalt, as iron has a lower standard electrode potential as compared to cobalt
(il0 ([lc]*/Fe) = -0,440 v, E0 1co2*/Co) = 0.271 v).
Table 1. Elemental analvsis of FeCo nanonarticles.
Calculated
Fe:Co ratio Mass content, 7oCoFe
50:50
2s .15
7-5 :2-5
46,9
?3.1
12.0
53, I
7 6.3
2rJ 0
305
r FeCo
- Feo(OH)
v coFe,o,
i, FCQ
-6ffi
2O
t8
16
12
10
[]igttrc I 'l'l:\{ in.urtlc ltttl X-r'11 tl iilllttrti()n Iirttln ol nitnoParticlcs: Ircs1l('os11 (lt). I:e_'r(icl7r (b)and
I'c11('1r,. (q';.
The TEM images (Fig. la,b) show that nanoparticles of Fe56Co56 erd
Fe25Co75 are aggregated spherical particles characterized by a bimodal
;!
a
rr$q,9*{,;j
306
distribution. Smaller nanoparticles have an average diameter of 6.5 (Fe5eCo5s)
and 6.4 nm (Fe25Co1). Larger nanoparticles are 28.5 (Fe56Co5e) and 31.6 nm
(Fe25Co75). Fe75Co25 (Fig. I c) has translucent particles with undefined shape,
which is a characteristic of iron hydroxides.
According to XRD analysis (Fig. 1) all samples contain the diffraction peak
near angle of 52 deg, which can be related to iron-cobalt alloy: 20
(FeCo) =52,6 deg (JCPDS No.49-156u), In case of Fe75Co25 S?rnple, when the
amount of iron was the highest, peak at 52 deg is weak, indicating almost
complete oxidation of the sample. In addition, all the samples contain products
of iron oxidation: FeO(OH) - 24.7 deg (JCPDS No. 81-0464), CoFe2Oa -
41.7 deg (JCPDS No. 22-1086), FeO - 71.9 deg (JCPDS No. 77-2355),
4, Conclusion
FeCo nanoparticles with calculated mass content Fe5pCo56, Fe25Co75 and
Fe75Co25 were successfully obtained and investigated by TEM and XRD
analysis. The samples contain phases of FeCo alloy, FeO(OH), CoFe2Oa, FeO. It
was shown that the sample with the largest amount of iron was almost
completely oxidized. FeCo nanoparticles are characterized by a bimodal
distribution with average sizes of 6.4-6.5 nm and 28.5-31.6 nm in case of
FcsoCoso and Fe25Co75. Nanoparticles of Fe7.5Co25 vta translucent with irregular
shape.
Acknowledgments
This work was supported by the Belarusian Foundation for Fundamental
Research (project H 1 4D-005).
References
l. A. N. Popova et al., Mater. Lett.74, 173 (2012).
2. A. Hutten et al., J. Magn. Magn. Mater. 293,93 (2005).
3. D. L. Peng et al., J. Alloys Comp. 469,276 (2009).
4. P. Karipoth et al., J. Colloid Inter, Sci. 404, 49 (2013).
5. M. Y. Rafique et al., J. Allovs Contp. 550,423 (2013).
