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CHAPTER-4
RESULTS AND DISCUSSIONS FOR Fe3O4
4 . 1 . X-Ray Diffraction (XRD):X-rays are a form of electromagnetic radiation. X-rays exhibit both wave
nature and particle nature. Arthur Compton confirmed the particle nature of Xrays by scattering of X-rays from electrons. The observation of X-ray diffraction
in the year 1912 was a confirmation for most of the scientists that X-rays were
a form of electro magnetic radiation.
X-Ray diffraction is a characterization technique. The basic
equation governing XRD is the Bragg Law. The
Bragg’s law is given by the equation, nλ= 2dsin
mathematical
form
where λ is the wavelength
of the x-rays, d is the spacing between certain crystalline planes, and
angle through which the x-ray is diffracted.
of
is the
Incident x-rays are diffracted at
different angles depending upon the d-spacing of crystal lattices.
Standard
data of XRD patterns of different crystals have been compiled and stored in
large database so that an experimental sample can be compared to a standard
on order to identify
the material and/or phase. For this analysis, a standard
for magnetite was obtained and plotted along with the experimentally collected
data.
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In crystals, atoms are arranged in a regular array(repeated arrangement
of atoms) like structure. When X-rays are incident on these atoms, they are
scattered by electrons revolving in those atoms. When an X-ray strikes the
electron, secondary spherical waves are produced .These secondary spherical
waves emanate from the electrons in the atoms. This phenomenon is called
elastic scattering and it is clearly understood that electron pays the role of
scatterer. A regular array of atoms produces a regular array of spherical waves.
In most directions, these secondary waves interfere destructively. Constructive
interference also takes place between these spherical waves in certain specific
directions given by Bragg’s Law:
Figure 4.1.1: Utilizing Bragg's law in XRD
Here d is the spacing between diffracting planes, θ is the incident angle, n is
any integer, and λ is the wavelength of the beam. These specific directions
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appear as spots on the diffraction pattern called reflections. Thus, X-ray
diffraction results from an electromagnetic wave (the X-ray) impinging on a
regular array of scatterers (the repeating arrangement of atoms within the
crystal).
To observe diffraction any diffraction clearly, the wave length of the incident
radiation should be comparable to the spacing between the scatterers. The
wave length of visible light is too high to observe to observe diffraction of
crystals. Wave length of X-rays is comparable to the unit cell spacing in the
crystal. That means, crystals can be used as diffraction gratings for X-rays and
there by we can understand crystal structure. Prior to the discovery of X-ray
diffraction, the d-spacings between the lattice planes in various crystals were
not known exactly.
Sample preparation for XRD is relatively simple since is
adhered to a glass slide. The particle powder was then deposited on top of the
tape and spread out to cover the entire surface of the tape.
Figure 4.1.2 shows the X-ray diffraction patterns of the samples at
different Fuel to Oxidizer Ratio Varying from 0.25 to 2. The heating
temperature for samples are 2500C. Fe3O4 nanoparticles prepared under
standard conditions reveals diffraction peaks at (220), (311), (400), (422), (511),
(440), These peaks are consistent with the database in JCPDS file(PDF No. #19629) etc. which are the characteristic peaks of the Fe3O4 crystal with a cubic
spinel structure. It is clear that only the phase of Fe3O4 is detectable for F/O
Ratio 0.75, 1.25, 1.5 and 2. There are some other impurities for o/f ratio 0.25,
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0.5,1 and 1.75. In this procedure. It could also been learned that particle size
is small from the relatively wide half-peak breadth. With the XRD pattern, the
average diameter which can be evaluated from Scherrer equation is obtained as
13.2 nm.
Figure 4.1.2: X-ray diffraction patterns of the samples at different Fuel to
Oxidizer Ratio
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Calculation of Crystallite Size:
The crystallite size of as prepared and calcinated or annealed
compositions were calculated from the full width at half maximum (FWHM) of
all the peaks in XRD pattern using the Debye-Scherrer formula.
(3.1.1)
Where B is the full width at half maximum (FWHM) of the XRD all
peaks, t is the crystallite size, λ is the wave length of the X-ray and θ is Bragg’s
angle. B (FWHM) calculated by use of the Gaussian function curve non linear
fitting in Origin8 software.
Determine Crystal Structure and Lattice Parameters:
Compare the XRD patterns of our samples with JCPDS data card and
choose the matched patterns for calculating lattice parameters. Note down the
plane Miller indices of each peak and crystal structure and indicate the same
Miller indices corresponding peaks of our samples. And next step is the
calculating lattice parameters from Bragg’s law (equation 3.2.b) and below
relation between inter planar distance (d) and lattice parameters (a, b, c) and
Miller indices (l, m, n) for each peak and average of those gives the lattice
parameters of unit cell of that sample.
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1/d= ((l/a)2+(m/b)2+(n/c)2)1/2
(3.1.2)
For Cube a=b=c eq.3.1.2 Becomes
( 3.1.3)
Crystallite sizes of Magnetite nanoparticles calculated by Deby-Scherrer
formula and help of Origin8. Our Magnetite nano particles XRD pattern
matched with PDF #19-629 (JCPDS card number). This samples structure is
Cubic and lattice parameters are calculated from above mentioned procedure of
determining lattice parameters. And those values are tabulated below.
F/O(Ratio)
Crystalline
size (nm)
Structure
Lattice
parameters
a(0A)
0.25
21.04
Cubic
8.241
0.5
17.94
Cubic
8.274
0.75
17.40
Cubic
7.633
1
15.66
Cubic
8.955
1.25
13.20
Cubic
6.761
1.5
18.11
Cubic
7.828
1.75
20.75
Cubic
8.400
2
15.80
Cubic
8.292
Table 4.1.1. Crystallite sizes and structure and lattice parameters of Magnetite
nanoparticles for different F/O ratios.
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4.2. Thermo Gravimetric/Differential Thermal Analysis (TG/DTA):
Thermo gravimetric analysis (TGA or TG) is
considered to be one of the five basic thermal analysis techniques. It involves
the measurement of change of sample mass with change of temperature. In
TGA, mass loss is observed if a thermal event involves loss of a volatile
component. Chemical reactions, such as combustion, involve mass losses,
whereas physical changes, such as melting, do not. The latter may be studied
by differential thermal analysis (DTA) or differential scanning calorimetry
(DSC), both of which measure the variation of heat flux in a sample with
variation of temperature.
Both physical and chemical changes in a sample can be measured
simultaneously by using simultaneous thermal analysis (STA or TGA-DTA),
which is a combination of TGA and DTA or, less commonly, DSC (TGA-DSC).
Simultaneous thermal analysis involves measurement of both mass loss and
heat flux of a sample simultaneously with variation of temperature. However,
thermal analysis techniques cannot be used in general for the identification or
characterization of a sample. A more detailed analysis of the thermal behavior
of a sample is possible if the volatile components released from a thermal
decomposition can be identified.
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Figure 4.2.1: TG/DTA Instrument.
While TGA provides mass loss data related to such volatiles, DTA gives
the temperature range over which such volatiles are released.
As materials are heated, they can lose or gain weight by reacting with the
atmosphere in the testing environment. Since weight loss and gain are
disruptive process to the sample material or batch, knowledge of the magnitude
and temperature of those reactions are necessary in order to design adequate
thermal ramps and holds during those critical reaction periods. The gas
environment is pre-selected for either thermal decomposition (inert gases such
as N2, He, Ar), oxidative decompositions (air or pure O2), or thermal–oxidation.
A peak of the temperature derivative of the weight dm/dt is indicate of the
oxidation temperature weigh is shifted to lower temperature for chemically
modified MWCNTs.
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Features:
•
Comprehensive and quick analysis of thermal stability, decomposition
behavior, composition, phase transitions, melting processes .
•
Can be easily operated because of top-loading facility, precise balance
resolution (25 ng resolution at a weighing range of 5g) and highest longterm stability
•
Interchangeable sensors for DSC measurements with highest sensitivity
and best reproducibility for reaction/transition temperatures and
enthalpies as well as for measurements of specific heat
•
A variety of optional system enhancements for ideal system adaption to
user-defined applications
•
Various furnaces, easily interchangeable by the user, available (optional
a swiveling double hoisting device for two furnaces)
•
Pluggable sample carriers (TG, TG-DSC, TG-DTA, etc.)
•
Automatic Sample Changer (ASC) for up to 20 samples
•
Automatic evacuation and refilling (Autovac)
•
Plenty of accessories, e.g. sample crucibles in the most varied of forms
and materials
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•
Unique for STA: temperature-modulated DSC (TM-DSC)
•
Figure 4.2.2: DTA patterns of the samples at different Fuel to Oxidizer Ratio
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Figure 4.2.3: TG patterns of the samples at different Fuel to Oxidizer Ratio
A thermo gravimetric differential
thermal analysis(TGDTA) curve was obtained
for determining the heating process .Then solution was dried at 400
0Cfor
nearly half an hourin air and a dry powder was obtained .Fig 4.2.2 shows a
typical TG_DTA curve for magnetite powder.A careful observation at TG curve
reveals a weight loss step in the temperature range of 250 0C – 400 0C.An endo
thermic peak can also be observed at around a temperature of 320 0C in the
DTA curve.The loss of decomposed organometallic precursor is the reason
behind the appearance of endo thermic peak.Above 400 0C, there is no weig ht
change.that means the heating temperature should be in the range of 250 0C to
400
0C.Below
250
0C,
the organic ester will not decompose.That’s why the
sample was annealed in air for nearly two hours at 2500C - 3500C.
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Experimental Procedure for Cp Calculation:
The sensitivity of the DTA/DSC baseline total heat capacity can be
exploited to determine the specific heat of unknowns. The procedure is outlined
in Fig 3.2.4. First, an empty sample container versus an empty reference
container is run. A known mass of standard material (our standard material is
the α-Alumina) with a known heat capacity (1.089 J/g/K) behavior is then
placed in the sample container and exposed to the identical heating rate.
Finally, a known mass of the material of unknown heat capacity is placed in
the sample container and exposed to the same heating rate. All three traces are
superimposed to the same plot, as shown in the Fig 3.2.4.
If the total heat capacities of the empty sample and reference
containers were perfectly matched, then the empty sample container versus
empty reference container trace should appear as a flat baseline of zero value
during the entire scan. This is rarely the case (due to asymmetries in
instrument construction) and is actually not necessary for this calculation. The
temperature deviation from this base line (empty panels line) for other traces is
a result of the extra thermal mass on the sample side, causing it to lag the
reference in temperature during the heating ramp. Defining Cp as the specific
heat (J/g/K), the sample specific heat is determined by the ratio;
where M is mass as determined from an analytical balance, and ∆T’s
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are measured at the same temperature. For reproducibility, the standard and
reference granules should be of the same size and the sample container should
be of the same size and the samplecontainer should be placed same position in
the DTA cell.
Above mentioned experimental procedure collected from the “Thermal
analysis of materials by speyer, marcelkker” publication. From above procedure
we were calculated the specific heat capacity at constant pressure (Cp) for
Magnetite nano particles at all O/F ratios. Those are shown in Table 4.2.1.
Figure 4.2.4 Outlined procedure for calculation of specific heat capacity (C).
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F/O
Cp(J/g.K)
0.25
0.541
0.5
0.582
0.75
0.643
1
0.631
1.25
0.674
1.5
0.668
1.75
0.672
2
0.675
Table 4.2.1 Specific heat capacity at constant pressure for different F /O ratios.
4.3. Fourier transform infrared spectroscopy (FTIR):
Fourier Transform is actually a mathematical algorithm.A raw data can be
converted into spectrum by using a fourier transform.Fourier Transform
Infrared
Spectroscopy
has
led
to
new
applications
in
in
Infrared
Spectroscopy.After the invention of FTIR spectroscopy, Dispersive Infrared
Spectrometers are outdated.Using FTIR
infrared
spectrum
of
spectroscopy, we can obtain obtain
absorption,emission,Raman
Scattering
of
a
solid,liquid,gas.The main advantage of FTIR spectrometer is that it can collect
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spectral data in a wide spectral range.A Dispersive Infrared spectrometer can
measure intensity only over a limited range of wave lengths
By looking at the above features, one can come to a conclusion that FTIR is a
novel technique in Infrared Specteroscopy.The vibrational transitions of a
molecule can also be detected by using FTIR.Michelson interferometer is an
integral part ofFTIR spectrometer.By using Michelson interferometer all wave
numbers can be measured at once.
Figure 4.3.1: FTIR Instrument
Michelson interferometer is the main part of FTIR spectrometer.Michelson
interferometer consists of a beam splitter, a fixed mirror and a moving
mirror.these two mirrors produce interference pattern.
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Figure 4.3.2: Scheme of FTIR interferometer
The beam splitter divides the incoming light beam into two beams.One beam is
sent onto fixed mirror and the other beam is sent onto moving mirror.The two
beams are reflected by the two mirrors and the beam splitter again collects
both beams.The resulting beamis passed to the sample compartment with
protein film.
The interference pattern is automatically converted into infrared
spectrum in accordance with the relation: B(ν)= ∫I(δ) cos 2δνπ δν, where B(ν) resulting spectrum, ν – wavenumber, I(δ) - interferogram pattern, and δ -
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optical path difference (difference in optical path length between the paths of
the two beams).
The extent to which a sample absorbs light beams at each wave length ,
is
measured
in
absorption
spectroscopy.In
Dispersive
Spectroscopy
a
monochromatic light beam is made to incident on the sample.The amount of
light energy absorbed by the sample is measured.the above process is repeated
with monochromatic beams of different wave lengths.
In fourier transform spectroscopy,a beam containing many different
frequencies of light is made to focus on the sample.The amount of light energy
absorbed by the sample is measured.In the next step, beam is modified to
contain different combinations of frequencies, giving a second data point. The
above process is repeated many times.All this data isfed to a computer and the
computer works on this data and gives the information about absorption of
light at each wave length by the sample.
The light beam used in FTIR spectrometer is generated by usng a broad
band light source.The broad band light source contains full spectrum ofwave
lengths.The light beam is focused on to configuration of two mirrors.One mirror
is fixed and the is moving mirror.this configuration is called Michelson
interferometer, as already mentioned.this interferometer allows allows certain
wave lengths and blocks other wave lengths.The beam is modified for each new
data pont by moving one of the mirrors.
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The data containing light absorption at different mirror positions is fed
to a computer.The computer processes this data and gives the absorption of
light energy for each wave length,by the sample.
Features:
•
Inorganic compounds and organic compounds in the sample
can be identified.
•
Components of an unknown mixture can be identified.
•
Analysis of solids, liquids, and gasses
•
In remote sensing
•
In measurement and analysis of Atmospheric Spectra
•
Solar irradiance at any point on earth
•
Long wave/terrestrial radiation spectra
•
Can also be used on satellites to probe the space
Fourier Transform Infrared Spectroscopy (FTIR) is a nondestructive analytical technique used to identify mainly organic materials.
FTIR analysis results in absorption spectra which provide information about
the chemical bonds and molecular structure of a material.
To realize the binding mechanism, FTIR spectra of the Fe3O4
samples at different Fuel to Oxidizer ratio Varying From 0.25 to 2. Were
examined as shown in below Figures.
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100.0
95
937.21
90
1053.77
1116.08
2065.99
85
478.91
461.18
2338.19
470.88
80
1384.36
75
70
680.90
65
60
55
50
%T
45
555.24
40
35
30
1634.21
25
20
15
10
3446.89
5
0.0
4000.0
3600
3200
2800
2400
2000
1800
cm-1
1600
1400
1200
1000
800
600
450.0
Figure 4.3.3. FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio 0.25
Fig 4.3.3.Shows FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio
0.25, the Spectra displays broad absorption around the peak 3446.89 cm−1
observed in curves relates to the –OH Stretching. H-O-H bonding at 1634.21
cm−1 and the main peak at 555.24 cm−1 relates to Fe–O stretching.
69
100.0
95
90
85
80
75
70
65
60
55
%T 50
45 3874.35
2065.46
1384.41
40
915.43
1109.48
1053.24
728.00
474.99
471.04
695.28
35
462.96
455.10
30
25
552.02
20
1631.33
546.84
635.04
15
10
3.2
4000.0
3600
3200
2800
2400
2000
1800
1600
cm-1
1400
1200
1000
800
600 450.0
Figure 4.3.4. FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio 0.5
Fig 4.3.4.Shows FTIR Spectrum of the Sample of Fe3O4having F/O Ratio
0.5, the Spectra displays broad absorption around the peak 3440.061 cm−1
observed in curves relates to the –OH Stretching. H-O-H bonding at 1631.33
cm−1 and the main peak at 552.02 cm−1 relates to Fe–O stretching.
70
100.0
95
829.33
937.35 901.48
808.99
920.74
865.36
848.31
90
3939.83
85 3988.84
452.96
465.61
80
3952.67
479.02
75
70
65
60
3872.90
3883.66
3864.17
3849.18
3798.233824.77
3790.19
3829.87
55
1047.80
1161.63 1021.04
1117.43
3761.19
50
%T
45
3741.35
3773.22
3779.17
1385.07
40
35
30
3721.71
3683.14
693.91
25
20
15
2922.79
10
2494.95
2310.65
3445.71
631.54
1630.72
5
554.47
-2.0
4000.0
3600
3200
2800
2400
2000
1800
1600
cm-1
1400
1200
1000
800
600
450.0
Figure 4.3.5. FTIR Spectrum of the Sample of Fe3O4 having F/O
Ratio 0.75
Fig 4.3.5.Shows FTIR Spectrum of the Sample of Fe3O4 having o/f Ratio 0.75,
the Spectra displays broad absorption around the peak 3445.71 cm−1
observed in curves relates to the –OH Stretching. H-O-H bonding at 1630.72
cm−1 and the main peak at 554.47 cm−1 relates to Fe–O stretching.
71
100.0
95
90
85
80
75
70
65
60
55 3884.19
929.03 780.82
730.17
693.96
%T 50
45
3851.26
40
465.95
1117.27
1045.511021.13
1419.82
35
30
25
20
15
10
1636.79
546.71
3.2
4000.0
3600
3200
2800
2400
2000
1800
1600
cm-1
1400
1200
1000
800
600
450.0
Figure 4.3.6. FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio 1
Fig 4.3.6.Shows FTIR Spectrum of the Sample of Fe3O4 having o/f Ratio
1, the Spectra displays broad absorption around the peak 3430.51 cm−1
observed in curves relates to the –OH Stretching. H-O-H bonding at 1636.79
cm−1 and the main peak at 546.71 cm−1 relates to Fe–O stretching.
72
100.0
95
90
85
80
75
928.78
1021.32
70
460.44
65 3995.89
60
896.98
801.15
3911.17
1116.771053.45
55
50
865.49
836.63
478.34
1412.87
%T
45
40
1384.60
35
30
25
2342.54
20
15
694.36
10
3433.27
633.93
554.99
1630.60
5
0.0
4000.0
3600
3200
2800
2400
2000
1800
1600
cm-1
1400
1200
1000
800
600
450.0
Figure 4.3.7. FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio 1.25
Fig 4.3.7.Shows FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio 1.25,
the Spectra displays broad absorption around the peak 3433.27 cm−1
observed in curves relates to the –OH Stretching. H-O-H bonding at 1630.60
cm−1 and the main peak at 554.09 cm−1 relates to Fe–O stretching.
73
100.0
95
1201.74
3859.56
90
3696.58
3717.79
85
929.34
896.96
867.94
1058.01
829.35
467.07
1101.44
1353.15
1384.76
80
75
70
480.97
65
60
55
50
%T
45
40
35
30
725.95
25
1630.71
20
555.47
582.91
694.25 635.09
15
3430.06
10
5
0.0
4000.0
3600
3200
2800
2400
2000
1800
1600
cm-1
1400
1200
1000
800
600
450.0
Figure 4.3.8 FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio 1.5
Fig 4.3.8 Shows FTIR Spectrum of the Sample of Fe3O4having F/O Ratio
1.5, the Spectra displays broad absorption around the peak 3430.06 cm−1
observed in curves relates to the –OH Stretching. H-O-H bonding at 1630.71
cm−1 and the main peak at 555.47 cm−1 relates to Fe–O stretching.
74
100.0
95
90
85
80
75
893.78
865.05
837.11
924.58
698.55
947.42
70
65
60
55
1116.64
%T 50
1416.91
1385.04
45
809.34
467.59
1047.55
40
780.80
754.39
729.26
461.78
35
30
25
20
1632.84
15
539.27
10
3.2
4000.0
3600
3200
2800
2400
2000
1800
1600
cm-1
1400
1200
1000
800
600
450.0
Figure 4.3.9 FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio 1.75
Fig 4.3.9 Shows FTIR Spectrum of the Sample of Fe3O4 having F/O Ratio
1.75, the Spectra displays broad absorption around the peak 3440.71 cm−1
observed in curves relates to the –OH Stretching. H-O-H bonding at 1632.84
cm−1 and the main peak at 539.27 cm−1 relates to Fe–O stretching.
75
100.0
95
3702.03
870.03
90 3865.80 3718.12
463.22
85
80
1112.86
1053.71
1021.19
2064.97 2026.78
75
70
1384.52
480.45
65
60
55
50
%T
45
40
35
30
726.34
25
20
1630.51
583.73
3427.09
15
694.69
10
555.06
5
606.85
635.17
0.0
4000.0
3600
3200
2800
2400
2000
1800
1600
cm-1
1400
1200
1000
800
600
450.0
Figure 4.3.10 FTIR Spectrum of the Sample of Fe3O4having F/O Ratio 2
Fig 4.3.10 Shows FTIR Spectrum of the Sample of Fe3O4 having F/O
Ratio 2, the Spectra displays broad absorption around the peak 3427.09 cm−1
observed in curves relates to the –OH Stretching. H-O-H bonding at 1630.51
cm−1 and the main peak at 555.06 cm−1 relates to Fe–O stretching.
76
4 . 4 . Scanning Electron Microscope (SEM):
The scanning electron microscope is capable of magnifying the sample’s
surface to 1,00,000times of it’s original size.the sem consists of Energy
Dispersive
Spectroscopy
and
electron
back
scatterer
Diffraction
arrangements.Both elemental and structural analysis of the sample can be
performed by using SEM.
Figure 4.4.1 Hitachi VP-SEM S-3400N
Principle of SEM:
A narrow beam of
electrons is focused onto a sample.The electrons in the
beam impinge on the molecules of the specimen.The impinging electrons collide
with electrons in the molecules of the sample.The impinging electrons are
77
deflected by the sample’s electrons.The energy of the deflected electrons
depends upon the interaction between the impinging electrons and sample’s
electrons.The energies of the deflected electrons electrons are analyzed by an in
built micro processor.The micro processor forms a three dimensional image of
the elements present in the given sample.
Figure 4.4.2 Block diagram of a typical SEM
Semi conductor Radiation detector is a Radiation detector in which a semi
conductor(either Silicon or Germanium crystal) acts as a detecting medium.The
Semi conductor Radiation detector can perform the duty of detection and
78
measurement of X-rays by the scanning electron microscopy.the semi
conductor detecting medium consists of a p-n junction.When an ionizing
radiation like X-rays pass throughthrough this junction,a current starts to flow
across the junction.
Some times the X-ray photon is absorbed across the p-n junction and
electron-hole pairs are created in the semi conducting medium.By applying
suitable voltage between the opposite faces of the semi conductor block,a
current can be
made to flow through the block.These currents are
recorded,amplified and analyzed to determine the energy energy,intensity and
identity of the incident charged particle.
If these detectors are operated at low temperatures, their sensivity can be
increased.This is because at low temperatures,generation of charge carrriers at
low temperatures(electron-hole pairs) due to thermal vibration can be
suppressed.
The signals produced by SEM contain back scattered electrons,
characteristic X-rays,secondary electrons,specimen current and transmitted
electrons.All SEMs
contain secondary electron detectors.A single machine
cannot have detectors for all types of signals mentioned above.Different types of
signalsin SEM are due to different types of interactios between the electrons
and the atoms at the surface of the sample.In almost all SEMs secondary
electron imaging is the common detection mode..In the
secondary electron
79
detection mode,SEM produces high resolution image of the surface of the given
sample.
These images reveal details about less than1 to 5nm in
size.The electron beam used in SEM is very narrow.That’s why the micrographs
produced by SEM have a large depth of field yielding a characteristic three
dimensional image.These images are of graet help to us in understanding the
surface structure of the given sample.
We
have
performed
SEM
analysis
for
the
best
sample(F/O=1.25).Fig 4.4.3 shows the morphology of magnetite precursor
powder without calcination at 10 µm.Fig 4.4.4 shows the morphology of
magnetite precursor powder after calcinations at 3 µm.Fig 4.4.5 shows the
morphology magnetite precursor powder after calcination at 1 µm.
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Figure
4.4.3
Morphology
of
the
Magnetite
precursor
powder
without
calcinations at 10µm
Figure 4.4.4 Morphology of the Magnetite precursor powder after calcinations
at 3µm
Figure 4.4.5 Morphology of the Magnetite precursor powder after calcinations
at 1µm
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4.5. Energy Dispersive Analysis of X-Ray (EDAX):
Energy dispersive X-ray analysis is a kind of spectroscopy used for
chemical characterization of a sample. Chemical characterization means the
analysis of elements present in a given sample. An X-ray beam is sent on to the
given sample. These X-rays collide with electrons in the sample. As a Result,
the charged particals are knocked out from their shells. Electrons from higher
level jump to the vacant shell and as a result, energy is released in the form of
X-rays. These X-rays are called Characteristic X-Rays. The wave length of these
X-rays are dependent on the atomic number of the element.
The X-Ray wave length emitted by A particular element are its
characteristic By determining the wave lengths of X-rays emitted from the
sample, we can identify the elements present in the sample. The X-ray emitted
from the sample are fed to an energy dispersive spectrometer. The energy
dispersive spectrometer measures the intensity as well as energy of the X-rays.
The energy of X-ray photon is equal to the energy difference between those to
shells, between which electronic Transition is taking place. This energy
difference between two particular shells is the characteristic of the element.
Hence by determining the wave lengths of X-rays emitted, we can identify the
elements present in the sample.
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Figure 4.5.1EDAX analysis of Magnetite nanoparticles at F/O Ratio is 1.25.
Table 4.5.1 gives a list of observed chemical composition of magnetic nano
particles synthesized by chemical combustion method(Fuel is Urea).
Element
Spectrum
Type
Element
(%)
Atomic
(%)
Fe
ED
73.34
44.08
O
ED
26.66
55.92
Table 4.5.1 EDAX analysis of Magnetite nanoparticles at F/O
is 1.25.
4.6: Vibrating sample magnetometer (VSM)
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Vibrating sample magnetometer was invented by Symon Foner(a
Scientist of MIT) in 1956.Later VSM’s are commercialized by EGG Princeton
applied research. By using VSM we can determine the magnetic properties of
diamagnetic materials, paramagnetic materials, Ferro magnetic materials, Ferri
magnetic materials and Anti Ferro magnetic materials
Figure.4.6.1 shows the vibrating sample magnetometer
It’s flexible design permits us to mount the sample and exchange
the samples easily. VSM has high sensitivity. In VSM, samples can be
interchanged rapidly at an operating temperature. Very small magnetic
moments of the order of 10-5 emu can also be measured by using VSM. VSM cn
be operated upto a maximum temperature of 1050K. using VSM magnetic
properties and parameters of powders, bulk and thin films can be studied.
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Principle:
The sample of a material whose magnetic properties have to be
determined is to be placed between the poles of an electro magnet. A uniform
magnetic field exists between the poles. A magnetic moment will be induced in
the sample. If the sample exhibits simple harmonic motion, a sinusoidal
electric signal is induced in pickup coils. The signal has the same frequency of
vibration as that of the vibrating sample. The amplitude of the signal is directly
proportional to the magnetic moment induced in the sample.
Figure.4.6.2 shows the vibrating sample magnetometer block diagram.
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The sample is fixed to a small sample holder located at the end of a
sample rod mounted in an electro mechanical transducer. A power amplifier is
driven by an oscillator of frequency 90 Hz. This power amplifier interm drives
the electro mechanical transiducer. The sample vibrates simple harmonically
perpendicular to mangnetising field. As a rsult of this an electric signl is
induced in the pickup coil system. This signal is fed to a differential amplifier.
The output from differentil amplifier is sent into a tuned amplifier and an
internal lock-in amplifier. The oscillator supplies reference signal to lock-in
amplifier. The output of this lock-in amplifier is the output of vibrating sample
magnatometr.
Magnetic characterization of the nano particles was carriedout byVSM at room
temperature.The applied magnetic fieldon the samplevaries from-5000 Oe to
+5000 Oe.The saturation magnetization (Ms) and coercive field(Hc) of the
sample are determined by using VSM.Magnetization curves of Fe3O4 particles
are shown in Fig 4.6.2 .The Hc value of sample was observed to be5.2Oe.Such
a small value of Hc is an indicativeof soft magnetic material.The Ms value was
found to be high and equal to 92 Am2 /Kg.From the above data we can
understand that these nanoparticles can be used in biological field and
targeted drug delivery.
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Figure 4.6.2 Field dependence of magnetization for Fe3O4nano particles at 10K.
Figure 4.6.3 Field dependence of magnetization Fe3O4nano particles at 350K.
87
Fig 4.6.2 and 4.6.3 show hysterisis loops of Fe3O4 at 10K and 350K
respectively.From these hysterisis loops it is clearly understood that they
exhibit characteristic of a soft magnetic material. A little amount of hysterisis is
observed at 10K, when the remenance and coercivity are very small.The
hysterisis almost diappears at 350K.
Figure 4.6.8 Temperature dependence of magnetization for Fe3O4 nano
particles at an applied field of 5000 Oe.
Gauss/Tesla-Meter
The magnetic response of the product in the magnetic field was
analyzed and evaluated by an electronic balance. 0.05 g Fe3O4 magnetic
nanoparticles prepared under the standard conditions were tested. This study
evaluated the magnetic response of magnetic particles through a Gauss/TeslaMeter to give more direct data for further research of targeted drug. Firstly, the
88
distance between ferromagnet and Fe3O4 powder placed on the balance dish
was changed to explore its influence to magnetic response (Fig. 4.6.4). The
maximum density of the ferromagnet itself was 206.5 mT which was tested at 0
cm position from ferromagnet.
Figure 4.6.4.Effect of the distance between Ferro magnet and Fe3O4
powder
Secondly, the number of the ferromagnets was changed to investigate the effect
on magnetic response (Fig. 3.6.5). All the ferromagnets had the same magnetic
performance, and the distance between ferromagnets and Fe3O4 powder was
fixed at 2 cm.