Structural and Magnetic properties of α-Fe 2 O 3 Nanoparticles د.محمد عبد الله ولد...
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![Page 1: Structural and Magnetic properties of α-Fe 2 O 3 Nanoparticles د.محمد عبد الله ولد محمد الأمين قسم الفيزياء كلية العلوم جامعة الإمام](https://reader036.fdocuments.net/reader036/viewer/2022062300/56649e7b5503460f94b7cdae/html5/thumbnails/1.jpg)
Structural and Magnetic properties of α-Fe2O3 Nanoparticles
األمين. محمد ولد الله عبد محمد دالفيزياء قسمالعلوم كلية
اإلسالمية سعود بن محمد اإلمام جامعةE-mail : [email protected] /[email protected]
SPS 4th annual meeting11-12 November 2008 - Riyadh
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Introduction
Experimental
Results
Conclusions
Outline
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Introduction
Maghemite (γ-Fe2O3) Hematite (α-Fe2O3) Magnetite (Fe3O4)
Magnetic iron oxides nanoparticles have attracted an increasing interest in the fields of nanoscience and nanotechnology.
Sol–gel processMicroemulsion techniqueForced hydrolysis methodChemical precipitation
Ball milling :has been used by several groups:
the phase transformations of α-Fe2O3 to γ-Fe2O3 or vice versa.
Recently L.C.Sanchez et al Physica B 389 (2007) : by milling in ethanol and in air (the jars were opened to the atmosphere)
Rhombohedrally centered hexagonal structureR3c space groupa=5.0356 Åc=13.7489 ÅT<TM = 260 K: antiferromagnetic
260 K<T<950 K: weak ferromagnetic (spin canting)T>TN = 950 K: paramagnetic
Aim of this work
Production of hematite nanoparticles without phase transformation by dry milling (the jars were
closed) ?
-Structural and magnetic properties
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Mechanical Alloying
Magnetic PropertiesStructure and Morphology
Mössbauer Spectrometry Hysterisis Loops XRD, SEM and FT-IR
Experimental
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Mössbauer Spectrometry
Information obtained from Mössbauer :
- Magnetic hyperfine characteristics of ironoxide phases.- Information concerning the valence stateof iron atoms.- Relative abundance of each component
Samples preparation
-Commercial α-Fe2O3 powder -Fritsch-P6 – Intensity 250rpm
-Stainless steel balls(10 and 15 mm in diameter) . -The sample to balls weight ratio 1:10
-Different milling times
Information obtained from Mössbauer: Mössbauer effect is the recoil-free emission and resonant absorption of gamma ( γ) rays from the nuclei of certain radioactive isotopes such as 57Fe
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Results
X-ray diffraction
All Bragg peaks were only assigned to the presence of α-Fe2o3.
The diffraction peaks became broader and their relative intensity decreases.
The peak broadening can be caused by both a reduction in crystallite size and an increase in lattice strain ???
In order to obtain these parameters (particles size and strain), a qualitative and quantitative phase analyses using the Rietveld method have been performed.
Visual observation : the color of the samples remains red (no new phase).
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Rietveld Analysis
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0 10 20 30 40 50
Milling time (H)
Fra
cti
on
al
va
ria
tio
n o
f u
nit
ce
ll
0
0
0 a
aa
a
a
0
0
0 c
cc
c
c
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60
Milling time (h)
Av
era
ge
pa
rtic
le s
ize
(n
m)
Δa/a0 and Δc/c0 were found to be positivefor all milled samples indicating a lattice expansion.-The variation have the same tendancy indicating anisotropic expansion.
The average grain size decreases
0
0.5
1
1.5
2
2.5
3
0 10 20 30 40 50 60
milling time(h)
Mic
ros
tra
in(%
)
The microstrain increase with milling time
-Using FullProf program
-The fitting is performed by a least square method.
-Information given by Rietveld : lattices parameteres,
microstrain average particle size
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FT-IR measurements
0
200
400
600
800
1000
1200
1400
3500 3000 2500 2000 1500 1000 500
Wave number (cm -1)
Tra
nsm
itta
nce
0 h
6 h
12 h
0
200
400
600
800
1000
1200
1400
3500 3000 2500 2000 1500 1000 500
Wave number (cm -1)
Tra
nsm
itta
nce
0 h
6 h
12 h
to access at possible structural changes of the hematite particle during the milling process ?
No new peaks in the milled spectraImportant changes in the relative intensities and broadening,
In agreement with XRD results
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Magnetic properties
Mössbauer Spectrometry Hysterisis Loops
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Mössbauer at room temperature
Unmilled
0.88
0.9
0.92
0.94
0.96
0.98
1
1.02
-15 -10 -5 0 5 10 15Velocity (mm/s)
Tra
nsm
issi
on
(a.
u)
48H
0.91
0.92
0.93
0.94
0.95
0.96
0.97
0.98
0.99
1
1.01
-15 -10 -5 0 5 10 15
Velocity (mm/s)
Tra
nsm
issi
on
(a.u
)
Only one sextet
= 0.37 mm/s
Q = -0.2 mm/s
H = 51.3 T
Bulk -Fe2O3
Micrometric (100%)
First sextet
= 0.37 mm/s
Q = -0.2 mm/s
H = 50.2 T
Micrometric -Fe2O3(52%)
second sextet
= 0.35 mm/s
H = 45 T
Nanometric -Fe2O3(48%)
H (kOe)
-20 -15 -10 -5 0 5 10 15 20
M (em
u/g)
-60
-40
-20
0
20
40
60
S0S4
T=100K
Hysteresis loops
- -The magnetic hysteresis loops for both samples are
typical of ferromagnet;
-Increase of saturation with decreasing size
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Conclusions
-Mechanical alloying of hematite micrometric powder processing can be used for the synthesis of hematite nanoparticles without phase transformation after milling from 1 up to 48h.
-An expansion of lattices parameters due to the increasing of microstrain induced by ball milling
-Mössbauer spectra show that are two component for the milled sample one attributed to the hematite nanoparticles and other due to micrometric hematite .
-XRD, FT - IR and Mössbauer : show that are no phase changing during the milling
Mohamed Alameen et al, (Submitted to International Journal of Nanosciences)
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Perspective
-Thermal analysis are in progress
-Particle size obtained by XRD ??? Furthers measurement of nanoparticles size will be conducted with others methods such as TEM and Brunauer – Emmett- Teller method (BET).
-Magnetic measurements (I will do more analysis on VSM measurements) .
New project :Gamma irradiation preparation of magnetite(Fe3O4) nanoparticles for MRI diagnosis.
Maghemite (γ-Fe2O3) Hematite (α-Fe2O3) Magnetite (Fe3O4)
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Acknowledgments
This work was supported financially by King Abdulaziz City for Sciences and technology (KACST).
Collaborations:
Dr A.Alyemani , R. Msalam and S. Mufti (KACST)
Pr M.Sajieddine, Materials sciences group (Sultan Moulay Slimane University,Béni-Mellal (Morroco).
Pr K.Ziq , Physics department, KFUPM
Dr M.Bououdina,Physics department, University of Bahrain, Kingdom of Bahrain
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شكرا علي حسن اإلصغاء