Nanocomposites and nanomaterials

Structural and Magnetic Properties of 
Copper-Iron Spinel / Reduced Graphene Oxide Nanocomposites
Hodlevska M.A., Kotsyubynsky V.O., Zapukhlyak R.I., Boychuk V.M, Bandura Kh.V., Fedorchenko S.V.

Vasyl Stefanyk Precarpathian National University. 
57 Shevchenko Str., Ivano - Frankivsk, 76025, Ukraine.
E-mail: kotsuybynsky@gmail.com
Copper iron spinel CuFe2O4 has various practical applications as catalyst and oxidative destruction, biologically active agent and material for gas sensitive systems, anode material for Na and Li-ion power cells. The performance of CuFe2O4 ferrite as functional material can be improved by using composite systems with graphene and reduced graphene oxide (rGO). CuFe2O4/rGO composite materials demonstrate enhanced performance as an electrode of supercapacitors. In this work the study of magnetic and structural properties of hydrothermally synthesized nanostructured CuFe2O4 and CuFe2O4/rGO was realized. 
Ultrafine CuFe2O4 and CuFe2O4/rGO were hydrothermally synthesized (160oC, 10 h) using GO obtained by Hummers method. The additional annealing at temperatures in the range of 300-700oC in argon atmosphere were done. Structure, morphology, chemical and magnetic properties of the materials were studied by XRD, low temperature nitrogen absorption, XRF and Mössbauer spectroscopy. CuFe2O4 samples have a cubic structure not depending on the annealing temperature. The correlation between structural (average particle size in the range of 7-14 nm) and morphological (SBET in the range of 50-70 m2/g) properties for CuFe2O4 indicates the low agglomeration degree. As-synthesized CuFe2O4/rGO was amorphous but annealing at 300oC causes both tetrahedral and cubic ferrite phases presence. Mössbauer spectra of as-synthesized CuFe2O4 system consist of doublet and sextet components, the annealing causes gradual doublet components intensity decreasing. The cation distribution for as-synthesized CuFe2O4 is (Fe)A[CuFe]BO4. The increase in annealing temperature in the range of 300-500oC causes inversion degree changes from 0.86 to 0.76 and SBET decrease in the range of 120-90 m2/g. As-synthesized and annealed at 300oC composite materials are paramagnetic ones but its Mössbauer spectra at 90 K are formed by combination of broadened doublet and sextet components that corresponds to transitive state between magnetically ordered and superparamagnetic ones with average size of ferrite particles <8-10 nm. The annealing at 400 oC causes beginning of magnetic ordering process that finished after annealing at 500oC. The Mössbauer spectra of CuFe2O4/rGO-500 sample were fitted by two magnetic sextets with hyperﬁne ﬁelds of 48.3 and 44.6 T, corresponding to octahedral and tetrahedral sites. The decrease in these values compared to typical data is caused by rGO fragments presence into the ferrite particles pores that results in the superexchange interaction distortion.