Liliya Frolova,
Alexander
Pivovarov, Elena
Journal of Chemical
Technology
and Metallurgy,
51, 2, Tsepich
2016, 163-167
ULTRASOUND FERRITIZATION
IN Fе2+-Ni2+-SO42--OH- SYSTEM
Liliya Frolova, Alexander Pivovarov, Elena Tsepich
Received 23 September 2015
Accepted 07 January 2016
Ukrainian State Chemical Technology University
Department of Inorganic Materials Technology and Ecology
Gagarin 8, Dnepropetrovsk 49005, Ukraine
E-mail: [email protected]
ABSTRACT
Synthesis of nanosized spinal ferrite was recently investigated due to potential applications in radio engineering, microwave devices, medicine. The aim of this study was to develop a new method of NiFe2O4 preparation. The work studied
the ultrasonic treatment (US) effect on the ferritization process in Fе2+-Ni2+-SO42--OH- system. A designed experimental
procedure was used to investigate the effects of pH, temperature, US treatment time on the ferritization. The major factors were outlined. The structural and morphological properties of NiFe2O4 particles were determined by X-ray powder
diffraction and Scanning Electron Microscopy. It was concluded that the process rate was higher in case US was applied.
In presence of intensifying factors, the initial pH, temperature and treatment time had a similar effect
Keywords: nickel ferrite, ferrite formation, ultrasound, nanoparticles.
INTRODUCTION
The development of technologies for the production
of ferromagnetic nanoparticles of a spinel structure has
been of considerable interest to researchers for many
years [1 - 6]. The reason is determined by the growing scope. The list of traditional fields of consumption
such as radio engineering, household appliances is now
complemented by the extensive use in medicine. This
demands the improvement of the ferrites quality. The
problem can be solved by the use of hydrophase technologies instead of traditional high-temperature ones [7
- 15]. The electrolysis of aqueous salt solutions, the solgel preparation, the coprecipitation of microemulsions
from aqueous and nonaqueous media are among them.
The ultrasonic treatment, the glow discharge, the
hydrothermal and microwave treatment [16, 17] are
promising but poorly understood methods of technological processes intensification. Ultrasound mixing usually
follows the heat treatment [18, 19]. But the parameters
of the ultrasonic treatment vary the rate of the processes
taking place in various media as well as the phase and
morphological composition of the products obtained.
The latter are also affected by heating, homogenization,
radiolysis which are among the intensifying factors studied [18 - 20]. The Impact mechanisms are studied there.
The aim of this study was to investigate the effect
of ultrasound processing on the ferritization process in
Fe2+-Ni2+-SO42+-OH- system. It focuses on the choice
of optimum ferritization modes using the method of
experimental design, which provides to obtain not
only the relation between the input parameters and the
response function but to determine the optimal conditions required.
EXPERIMENTAL
The co-precipitated compound was obtained by
pouring under continuous stirring to an appropriate
mixture of sulfates solutions of cations ratio corresponding to that of the ferrite. Consequently, a concentrated
precipitant solution was added and ultrasound was
applied. The equipment and the methodology applied
were previously described [16 - 17]. The concentration
163
Journal of Chemical Technology and Metallurgy, 51, 2, 2016
00
10
10
20
20
30
30
40
40
50
50
60
60
70
70
80
80
90
90
100
2θ
Fig. 1. XRD pattern of the nickel ferrite powder synthesized.
of Ni2+ in the samples obtained was assessed complexometrically, while that of the iron cations - by potassium
permanganate and dichromate method.
The reactor used to monitor the reaction progress
was provided with an electrode system including a
platinum electrode, ECL 43-07 glass electrode, and
EVL-1M3 counter electrode. The temperature was
thermostatically controlled.
All precipitates were washed until a negative sulfate
ion reaction. After precipitation the suspension was left
for 48 hours in the mother liquor. Following the extraction the precipitate was magnetically separated. The
washed and filtered precipitates were dried at 1000C.
The relative magnetic characteristics were determined
by the method described in ref. [16]. The ferritization
degree was calculated on the basis of the magnetic flux
density saturation growth.
The end of the process referred to the constant value
of the system redox potential.
The dry powder phase content was determined by
X-ray diffraction (DRON-2.0, Cu-Ka-radiation). The
solution electron microscopy with X-ray microanalysis
was performed with Remmy-102 (SELMI, Ukraine).
The crystallite average size was assessed with the application of the Debye-Scherrer method.
Fig. 2. A photomicrograph of the nickel ferrite powders
obtained.
Based on experiments conducted, we selected the
ferritization, the initial pH of the solution, the ultrasound
processing time or CNR and the temperature of the process as the main technological parameters influencing
the process. The following values of the factors were
proposed as boundary conditions (Table 1).
RESULTS AND DISCUSSION
The factors which allow to adjust both phases
composition and the size of the particles obtained
are currently known. They refer to the initial solution
concentration, the sequence of fluids draining, the ratio
Table 1. Factors influencing the ferritization process.
Factor
Name
X1
X2
X3
рН
Temperature
Processing time
Dimension
o
С
Min
Max
11,0
24
0
Value
Min
8,0
50
8
The major effects and interaction between the main factors can be estimated using A = X1* X2 (1) B = X2*
X3 (2) C = X1* X3 (3)
164
Liliya Frolova, Alexander Pivovarov, Elena Tsepich
Table 2. Results of the full factorial experiment.
№
pH
Temperature, oС
Time, min
Conversion degree, %
1
2
3
4
5
6
7
8
11
8
11
8
11
8
11
8
50
50
24
24
50
50
24
24
8
8
8
8
0
0
0
0
44,71
0,01
23,53
0
35,29
0
14,12
0
a)
9
t,min
0,01
8
7
7
4
0,002
3
40
6
0,006
5
45
8
0,008
6
b)
9
t,min
35
5
0,004
30
4
25
3
20
2
2
1
22
15
1
0
0
0
27
32
37
42
22
t,52C
47
c)
t,min
10
27
32
37
42
t,52
C
47
d)
t,min
10
9
9
8
7
50
8
25
40
7
20
6
6
10
15
30
20
5
5
4
4
10
3
3
5
0
2
0
2
1
1
7,5
8,5
9,5
7,5
рН
11,5
10,5
t,50
C
e)
40
t, C
рН
0
t, C
0
8,5
9,5
10,5
11,5
t, C
50
50
f)
45
45
30
40
20
40
30
40
20
35
35
10
10
30
0
30
0
25
25
20
7,5
8,5
9,5
10,5
t, C
11,5
рН
20
7,5
8,5
9,5
10,5
t, C
рН
11,5
Fig. 3. Contour lines showing the ferritization degree under the influence of ultrasound in different coordinates a)
a = f(t,t) pH = 7, b) a = f(t,t) pH = 11, c) a = f(t,pH) t = 240C, d) a = f(t,pH) t = 50 0C, f) a = f(t,pH) t = 4 min,
e) a = f(t,pH) t = 8 min.
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Journal of Chemical Technology and Metallurgy, 51, 2, 2016
y,50
%
X2 +
45
40
35
30
25
X2 -
20
15
10
5
0
0
X1 -
0,2
0,4
0,6
0,8
X1 1+
y,50
%
1,2
X3 +
45
40
35
X3 +
30
X3 -
25
20
geneously dispersed are almost rectangular in form with
1mm -10 mm average size.
The ferritization degree value performs as a response
function (Y) in the course the research carried out with
the appication of the experimental design method. It
characterizes the degree of conversion (Table 2). The
model calculations and the subsequent optimization
is performed using STATSGRAPHICS 7.0. It is worth
adding that the low conversion degree corresponds
to the possibility of oxidation of ferric compounds to
oxides and oxyhydroxides. FeOOH, Fe(OH)3, and NiO
are not magnetic.
The correlation between the ferritization degree
and the factors pointed is adequately described by the
equation:
15
X3 -
10
Y=14,71+14,70x1+5,29x2+2,35x3+
+5,29x1x2+2,35x1x3+0,0015x3x2
5
0
0
X2 -
0,2
0,4
0,6
0,8
X1 2+
y,45
%
40
35
X1 +
X1 +
30
25
20
15
10
X1 -
X1 -
5
0
0
X3 -
0,2
0,4
0,6
0,8
1
X3 +
1,2
Fig. 4. The mutual influence of different factors: a) effect A
(x3 = 8 min); b) effect B (x1 = 11), c) effect C (x2 = 50 0C).
of reactants, etc. The ferritization speed which can be
regulated in different ways can also be one of these
factors. It is worth adding that the shape and the size of
the nickel ferrite particles depends substantially on the
production technology.
A typical X-ray diffraction pattern obtained in ultrasound presence is shown in Fig. 1. The juxtaposition
of the XRD pattern of the particles synthesized with the
standard diffraction spectrum (JCPDS:10-0325) shows
that the synthesized product is crystalline NiFe2O4. The
sharpness of XRD reflections clearly indicates that the
synthesized NiFe2O4 is slightly crystalline. No secondary
phase is detected.
The corresponding SEM micrograph is shown in
Fig. 2. It is seen that the particles which are not homo-
166
(1)
1,2
Regression models can be used to describe the dependence of the ultrasound ferritization on the key factors investigated. Analyzing the equation (1) we can say
that the initial pH of the solution has the greatest impact
on ferritization process - the pH increase brings about
the ferritization degree increase. The temperature and
the processing time variation have the same effect. Fig.
3 shows the contour lines corresponding to various ferritization degrees obtained under different coordinates.
Aiming to study mutual influence we made a correlation between the selected factors at their minimum
and maximum values (the third factor was fixed at the
maximum level). Compared to the effect of the initial
pH value, the processing time has a relatively small
effect on ferritization degree. The same is valid for the
temperature change.
When the levels of some factors are fixed at their
maximum and minimum values, the slope characterizes
the degree of the factor direct influence. This provides to
determine the interaction between the factors considered.
The curves in Fig. 4 (b and c) run almost in parallel,
which means that there is no significant interaction between the factors x3 and x2, as well as between x3 and x1.
Fig. 4b shows that the ferritization is at zero level
at low pH and does not depend on the time of the ultrasound processing.
Fig. 4a shows that the treatment time effect on the
ferritization degree is greater at high pH values.
Liliya Frolova, Alexander Pivovarov, Elena Tsepich
CONCLUSIONS
We studied the methods of hydrophase ferritization
by means of ultrasound processing. We followed also
the effect of the key factors on the nature of the final
product on the basis of the full factorial experiment
carried out. The advantage of this approach was in the
provision of complex information concerning the conditions necessary to obtain a final product of predetermined characteristics by conducting a limited number
of experiments. The experimental data obtained shows
that the ferritization degree varies depending mainly
on the initial pH, the temperature and the processing
time. The X-ray diffraction and microscopic analysis
revealed the phase composition of the precipitate and
its particles characteristics as well as their dependence
on the preparation conditions.
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