Properties of Cu-Ni ferrite nanopowders prepared by coprecipitation method with ultrasound irradiation

Article abstract of DOI:10.1002/pssa.200304597

Cu-Ni ferrite(Cu_1-xNi_xFe₂O₄) nanopowders were synthesized by coprecipitation method with ultrasound irradiation. They were composed of a spinel phase having a spherical shape with the grain size of 20 - 40 nm. The specific surface area of the nanopowders showed a tendency of decreasing with increasing Ni content (x). The maximum value of saturation magnetization was 73.5 emu/g at x = 0.5. The reflection loss was higher than 10 dB in the frequency range from 2.5 GHz to 5.5 GHz. The maximum reflection loss of 25 dB was observed at x = 0.5. Thermogravimetric analysis of the Cu_1-xNi_xFe₂O₄) nanopowders for both H₂ reduction and CO₂ decomposition reaction was carried out with Cahn vacuum electrobalance system. The maximum CO₂ decomposition occurred in the Cu_0.5Ni _0.5Fe₂O₄) nanopowder.

Full text of DOI:10.1002/pssa.200304597

phys. stat. sol. (a) 201, No. 8, 1889–1892 (2004) / DOI 10.1002/pssa.200304597
Properties of Cu–Ni ferrite nanopowders prepared
by coprecipitation method with ultrasound irradiation
S. G. Doh1, E. B. Kim2, B. H. Lee2, and J. H. Oh*, 1
1
School of Materials Science and Engineering, Inha University, Inchon 402-751, Korea
Department of Inorganic Materials Engineering, Myongji University, Yongin 449-728, Korea
2
Received 15 November 2003, revised 5 March 2004, accepted 17 March 2004
Published online 8 June 2004
PACS 75.50.Tt, 81.40.Rs
Cu–Ni ferrite(Cu1–xNixFe2O4) nanopowders were synthesized by coprecipitation method with ultrasound
irradiation. They were composed of a spinel phase having a spherical shape with the grain size of
20 ~ 40 nm. The specific surface area of the nanopowders showed a tendency of decreasing with increasing
Ni content (x). The maximum value of saturation magnetization was 73.5 emu/g at x = 0.5. The reflection
loss was higher than 10 dB in the frequency range from 2.5 GHz to 5.5 GHz. The maximum reflection
loss of 25 dB was observed at x = 0.5. Thermogravimetric analysis of the Cu1–xNixFe2O4 nanopowders for
both H2 reduction and CO2 decomposition reaction was carried out with Cahn vacuum electrobalance sys-
tem. The maximum CO2 decomposition occurred in the Cu0.5Ni0.5Fe2O4 nanopowder.
© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
1 Introduction Coprecipitation process assisted with ultrasound irradiation was an effective method
for the preparation of various multicomponent nanopowders.Ultrasonic irradiation in liquid can induce a
cavitation process. The cavitation leads to hot-spot and microjet impacts on materials, which can result in
activating physical and chemical reaction [1, 2]. Ferrite is one of materials used for microwave absorber.
A number of investigations have been reported for studying the effect of composition on microwave
absorption properties [3]. In addition, oxygen-deficient ferrite is a good material to convert carbon diox-
ide into carbon, which carbon dioxide is one of the greenhouse gases and has been a current subject in
the field of environmental science [4, 5]. The oxygen-deficient ferrite can be formed by hydrogen reduc-
tion (Eq. (1)) of ferrites at a temperature near 300 °C and is represented by a general formula MxFe3–xO4–δ
where M is a bivalent metal ion such as Mn, Fe, Co, Ni and Cu; the oxygen deficiency δ expresses the
degree of reduction. The oxygen-deficient ferrites can reduce CO2 into carbon (Eq. (2)) [4–6].
MFe2O4 + H2 = MFe2O4–x + xH2O
(1)
(2)
MFe2O4–x + CO2 = MFe2O4 + CO2–x
In this study, Cu1–xNixFe2O4 nanopowders were synthesized using coprecipitation method with ultrasound
irradiation. Their magnetic properties and CO2 decomposition properties were investigated.
2 Experimental CuCl2 · 2H2O, NiCl2 · 6H2O and FeCl2 · 4H2O were used for preparation of
Cu1–xNixFe2O4 nanopowders by coprecipitation method with ultrasound irradiation. They were dissolved
in distilled water. The total reaction solution volume was 420 ml. The mixed solution of the metallic
chlorides was added to NH4OH solution maintaining pH 12.5, which was reacted for 6 h with ultrasound
irradiation (20 kHz, 750 W; amplitude 50%, ultrasonic tip; 19 mm). The coprecipitate was filtered,
* Corresponding author: e-mail: jaeheeoh@inha.ac.kr, Phone: +82 32 860 7524, Fax: +82 32 866 0131
© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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S. G. Doh et al.: Properties of Cu–Ni ferrite nanopowders
400
350
300
250
200
0.0
0.2
0.4
0.6
0.8
1.0
X
Fig. 1 XRD patterns of the Cu1–xNixFe2O4
nanopowders prepared by ultrasound irra-
diation.; (a) x = 0.0, (b) x = 0.5, (c) x = 1.0.
Fig. 2 Specific surface area of the Cu1–xNixFe2O4
prepared by ultrasound irradiation.
washed with water and ethanol, and then dried at 120 °C for 12 h. The ferrites were analyzed by XRD,
BET, TEM and VSM to examine their microstructures and magnetic properties. The microwave absorb-
ing properties and the CO2 decomposition properties were measured using a network analyzer and Cahn
vacuum electrobalance system, respectively.
The prepared Cu1–xNixFe2O4 (x = 0.0, 0.5, and 1.0) nanopowders were reduced by H2 gas (99.9%) in
Cahn vacuum electrobalance system. The ferrite powder (0.5 g) was placed in a Pt cell in a pyrex tube
and heated up to 450 °Cꢀunder H2 gas (60 cc/min) at the rate of 5 °C/min. And then, after each reaction,
the produt was examined by X-ray diffraction. The CO2 decomposition reaction was performed with
flowing CO2 (99.9%) gas at the rate of 60 cc/min as the temperature increased up to 510 °C.
3 Results and discussion
3.1 Magnetic properties and synthesis of Cu–Ni ferrites Single ferrite phase of the Cu1–xNixFe2O4
nanopowders could be obtained by coprecipitation method with ultrasound irradiation. The X-ray dif-
fraction patterns of the Cu1–xNixFe2O4 (x = 0.0, 0.5, 1.0) nanopowders are shown in Fig. 1.
Figure 2 shows the specific surface area of the prepared nanopowders measured with BET method. The
maximum value of specific surface area was 335.4 m2/g at x = 0.5.
TEM micrographs of the Cu1–xNixFe2O4 nanopowders are shown in Fig. 3. The ferrite particles had a
spherical shape with the grain size of 20 ~ 40 nm.
Figure 4 shows the hysteresis loop of the Cu1–xNixFe2O4 nanopowders with different Ni contents (x).
The saturation magnetization of the Cu1–xNixFe2O4 nanopowders showed the maximum value
(73.5 emu/g) at x = 0.5. The reflection loss of the Cu1–xNixFe2O4 nanopowders are shown Fig. 5. In the
frequency range of 2.5 GHz ~ꢀ5.5 GHz, the reflection loss was higher than 10 dB. The maximum reflec-
tion loss of 25 dB was observed at x = 0.5.
Fig. 3 TEM micrographs of
the Cu1–xNixFe2O4 nanopowders
prepared by ultrasound irradia-
tion.
© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

phys. stat. sol. (a) 201, No. 8 (2004) / www.pss-a.com
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100
0
-10
-20
-30
80
(b)
60
(c)
(a)
40
(c)
(a)
20
0
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-40
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(b)
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-5000
0
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10000
2
4
6
8
10
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Magnetic field(Oe)
FREQUENCY [GHz]
Fig. 5 Reflection loss of Cu1–xNixFe2O4 nanopowder
prepared by ultrasound irradiation; (a) x = 0.0, (b)
x = 0.5, (c) x = 1.0.
Fig. 4 Hysteresis loop of Cu1–xNixFe2O4 nano-
powders prepared by ultrasound irradiation.; (a)
x = 0.0, (b) x = 0.5, (c) x = 1.0.
Table 1 shows the matching frequency and thickness of the Cu1–xNixFe2O4 nanopowders with different
Ni contents (x). The matching frequency decreased with increasing the Ni content, while matching thick-
ness increased with increasing the Ni content.
3.2 Redox of Cu–Ni ferrites The redox behaviors of the Cu1–xNixFe2O4 nanopowders were investi-
gated by TGA and XRD. The weight lossꢀof the ferrite for H2 reduction are shown in Fig. 6. The weight
loss percentages were 32% (x = 0.0), 32% (x = 0.5), and 37.5% (x = 1.0).
The phases of the reduced powders were metallic Cu, Ni, α-Fe, and Ni–Fe alloy, indicating that oxy-
gen atoms in the Cu1–xNixFe2O4 were eliminated during the reduction.ꢀ
The weight gainꢀof the reduced samples for CO2 decomposition are shown in Fig. 7. The weight gain
percentages of the oxidized samples were 13% (x = 0.0), 15.8% (x = 0.5), and 8.7% (x = 1.0).
During the decomposition of carbon dioxide, which decomposed into carbon and oxygen was ad-
sorbed in the special sites of oxygen-deficient ferrite [6]. The CO2 decomposition was observed to occur
greatly in the sample of x = 0.5. As the smaller particle size, the CO2 decomposition was activated. The
oxidized powder was composed of mixture of metallic Cu, Ni, and spinel ferrite.
4 Conclusion Cu–Ni ferrite(Cu1–xNixFe2O4) nanopowders were synthesized by coprecipitation method
with ultrasound irradiation. The nanopowders had a spherical shape with the grain size of 20 ~ 40 nm.
The ferrite nanopowder with the Ni content of x = 0.5 exhibited the maximum specific surface area and
the maximum saturation magnetization. The nanopowders showed that the reflection loss was more than
10 dB in the frequency range of 2.5 GHz ~ 5.5 GHz and reached the highest level at x = 0.5. Addition-
ally, the redox reaction of the nanopowders was studied for CO2 decomposition. The CO2 decomposition
ability was highest in the ferrite powder of x = 0.5. Thus, the ferrite nanopowder prepared in this study
can be promising materials applied for CO2 decomposition.
Table 1 The matching frequency and thickness of Cu1–xNixFe2O4 nanopowders with the composition of x.
mole fraction of Ni (x)
matching thickness [mm]
matching frequency [GHz]
6.44
7.50
7.90
5.05
4.37
4.00
CuFe2O4 (x = 0)
Cu0.5Ni0.5Fe2O4 (x = 0.5)
NiFe2O4 (x = 1)
© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

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S. G. Doh et al.: Properties of Cu–Ni ferrite nanopowders
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65
60
(b)
(a)
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81
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75
72
69
66
63
60
(b)
(c)
(a)
(c)
0
100
200
300
400
500
600
0
100
200
300
400
500
Temperature (˚C)
Temperature (˚C)
Fig. 6 Weight loss of Cu1–x NixFe2O4 nanopoders for H2
reduction; (a) x = 0.0, (b) x = 0.5, (c) x = 1.0.
Fig. 7 Weight gain of Cu1–x NixFe2O4 nanopowders
for CO2 decomposition; (a) x = 0.0, (b) x = 0.5, (c)
x = 1.0.
Acknowledgements This work was supported by grant No. R01-1999-000-00192-0 from the Basic Research
Program of the Korea Science & Engineering Foundation.
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[4] Y. Tamaura and M. Tabata, Nature 346, 255 (1990).
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© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim