study of nanosized ferrite materials prepared by co …7ncc.unionchem.org/presentations/7ncc-5-o4-z...
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STUDY OF STUDY OF NANOSIZEDNANOSIZED FERRITE FERRITE MATERIALS PREPARED BY MATERIALS PREPARED BY
COCO--PRECIPITATION METHODPRECIPITATION METHOD
Z. Cherkezova-Zheleva
Institute of Catalysis, Bulgarian Academy
of Sciences
Why it is important to study ferrite nanomaterials
Experimental part of the presented study
Results and discussion
Some conclusions
The study of ferrites is of The study of ferrites is of great importance great importance
Ferrites
magnetic materials electronicscatalystsceramic materials
biomaterials for medical diagnostics and therapy
The study of ferrites is of The study of ferrites is of great importance great importance
Ferrites -biomaterials
for therapy
for medical diagnostics as contrast agents
How to obtain How to obtain better performance better performance of ferrite material ?of ferrite material ?
Ferrite preparation – object of huge number of studies, but not well resolved problem ; Change of chemical composition ; Change of particle size – down to nano-scale.
Methods of nano-ferritespreparation
1、High-energy grinding;
2、Wet chemical processes –co-precipitation, sol-gel, hydrothermal preparation;
3、Plasma flame pyrolysis, electricalexposion, laser ablation, high-temperature evaporation, plasma synthesis techniques
4、And so on…………
Synthesis proceduresMuch attention has been paid to the preparationof nanocrystalline materials, because of difficult synthesis procedures and special techniques typically used. Co-precipitation has proved to be asuccessful method, since co-precipitation of Fe2+
and Fe3+ in alkaline media can be performed to obtain directly the ferrite material.
Spinel structure A B2 O4
each B atom has 6 oxygen n.n.each having just 1 A atom n.n.
B – O – A paths:6 starting from B
each A atom has 4 oxygen n.n.each having 3 B atoms n.n.
A – O – B paths:12 starting from A
oxygen
B atoms in octa-
A atoms in tetra-hedral positions
only front half of the cube is shown
V. Šepelák, F. J. Litterst, K. D. Becker, A Modified Core-ShellModel of Ferrimagnetic Oxide Nanoparticles
with magnetic moments
Co ferrite – distribution of cationsover A and B sites
O2-4Co2+Fe3+Fe3+
tetra- octa-hedral positions
f.c.c. “frame”
with magnetic moments
5μB 3μB 5μB
O2-4Fe3+ Fe3+Co2+
tetra- octa-hedral positions
f.c.c. “frame”
3μB 5μB 5μB
inverse normal
Co2+1-i
Fe3+i
mixed with i = degree of inversionCo2+
iFe3+
2-i
M = MB-MA =[3i+5(2-i)]-(5i+3-3i) = =[10-2i] – (3+2i) = {7 – 4i} [μB]A. Lančok, K. Závěta, M. Veverka, E. Pollert, MÖSSBAUER STUDY OF Co AND Co-Zn FERRITES
Magnetite (Fe3O4), has an inverse spinel structure, the oxygen atomforms a closed packing, and the iron cations take up the interstitialtetrahedral or octahedral positions. Electrons can jump from Fe2+
to Fe3+ at room temperature.
The presence of different ions like Mg2+, Co2+, Cu2+, etc., blocks this electron hopping.
The compounds magnetite (Fe3O4) and Me0.5Fe2.5O4 ferrite (Me = Mg2+, Co2+, Cu2+, etc.) are members of solid solution series, which permits to synthesise samples of different electron delocalization degree.
Me2+
The aim of this investigation is - to synthesise and - to characterise different nanosized
magnetite and magnetite-type samplesMe0.5Fe2.5O4, Me2+=Fe, Mg, Co, Cu
- to study their physicochemical and catalytic properties with respect to different chemical composition and electronic properties.
Aim:Aim:
Experimental:Experimental:
Preparation
Characterisation
Catalytic tests
Preparation Co-precipitation method
Solutions of FeCl2•4H2O, FeCl3 •6H2O and MeCl2•xH2O – Me=Fe, Mg, Co and Cu, with distilled water were prepared.
The main solutions of Fe2+, Fe3+
and Me2+ were mixed at a ratio of 1:4:1 and the co-precipitation process was performed by adding the alkaline solution of NaOH to the mixture.
The precipitate obtained was washed to pH=7 and dried. A black precipitate was obtained in all cases.
ExperimentalExperimental
Sample characterisatonPhase composition Crystal structure and lattice parameters Particle size Particle shape Magnetic structure Temperature behaviour Catalytic behaviour
X-ray powder diffractionMössbauer analysis Infrared spectroscopy Thermal analysis HR-TEM with SAED Catalytic measurements
Used methods
ExperimentalExperimental
Ssimultaneous thermogravimetry-differential scanning calorimetrywas carried out by Linseis STA-PT1600 thermobalance in static air at a heating rate of 10oC/min .
Thermal analysisExperimentalExperimental
The transmission Mössbauer spectra of 57Fe were taken at RT and LNT by Wissel Wissenshaftliche Electronik GMBH (Germany)spectrometer equipped with a source of 57Co in Rh matrix and working in the constant-acceleration mode. The calibration of the velocity scale was made by a standard α-Fe foil at room temperature and the isomer shift is also given with respect to this standard.
Mössbauer analysisExperimentalExperimental
X-ray powder diffraction TUR M62 apparatus, HZG-4 goniometer with Bregg-Brentano geometry, CoKαradiation and Fe filter. Data base (Powder Diffraction Files, Joint Committee on Powder Diffraction Standards, Philadelphia PA, USA, 1997) was used for identification of the phases. Voigt profile was used to resolve instrumental, strain and size contributions to peak broadening.
Wexp=αWL + βWG
D = k λ /WL cosθe=WG/(4tanθ)
ExperimentalExperimental
Infrared spectroscopy
IR and far-IR spectra were recorded by a Nicolet 6700 IR spectro-photometer in KBr pellets within the 250–650–4000 cm–1 range.
ExperimentalExperimental
HR TEM SAED
A JEOL 2100 microscope has been developed to achieve the highestimage quality and the highest analytical performance in the 200-kVclass analytical TEM with a probe size below 0.5 nm.
ExperimentalExperimental
Catalytic measurements
In situ diffuse-reflectance measurements (DRIFTS) on Nicolet 6700 FTIR spectrometer by high temperature/vacuum chamber (Thermo Spectra-Tech) in the region of 1111–4000 cm–1 were carried out by using CaF2 windows.
The catalytic tests were performed in the reaction of CO oxidation.
ExperimentalExperimental
Fe3O4
FeCl2.4H2O , FeCl3.6H2O - main solutions, alkaline solution of NaOH
FeCl2 + FeCl3 + NaOH →Fe[H2 O]6
2+ + Fe[H2 O]63+ + Na+ + OH- + Cl- →
Fe(OH)2 + Fe(OH)3 + NaCl + H2O →[ (Fe3+ ) (Fe2+ )2 (OH- )(O2- )2 ]2- + NaCl + H2 O →Fe3O4 ↓ + NaCl + H2 O
PreparationPreparationResultsResults
PreparationPreparationResultsResults
Cu0.5Fe2.5O4FeCl2.4H2O , FeCl3.6H2O, CuCl2.2H2O main solutions, alkaline solution of NaOH
Mg0.5Fe3O4FeCl2.4H2O , FeCl3.6H2O, MgCl2.6H2Omain solutions, alkaline solution of NaOH
Co0.5Fe2O4FeCl2.4H2O , FeCl3.6H2O, CoCl2.6H2Omain solutions, alkaline solution of NaOH
Chart of preparationChart of preparation
Co-precipitation
Washing
Drying
Samples
Mixture of Fe (Mg, Co, Cu) chlorides
Solution
NaOH
Control pH
XRD study
1 09 8 7 6 5 4 3 2
Inte
nsity
, a.u
.
d , A
M g 0 . 5 F e 2 . 5 O 4
F e 3 O 4
C o 0 . 5 F e 2 . 5 O 4
C u 0 . 5 F e 2 . 5 O 4
Cu0.5Fe2.5O4 < Co0.5Fe2.5O4 < Mg0.5Fe2.5O4 < Fe3O4
-10 -8 -6 -4 -2 0 2 4 6 8 10
84
86
88
90
92
94
96
98
100
Co0.5Fe2.5O4
Rel
ativ
e tra
nsm
issi
on, %
Velocity, mm/s
-10 -8 -6 -4 -2 0 2 4 6 8 10
78
80
82
84
86
88
90
92
94
96
98
100
Cu0.5Fe2.5O4
Rel
ativ
e tra
nsm
issi
on, %
Velocity, mm/s
-10 -8 -6 -4 -2 0 2 4 6 8 10
82
84
86
88
90
92
94
96
98
100
Mg0.5Fe2.5O4
Rel
ativ
e tra
nsm
issi
on, %
Velocity, mm/s
Mössbauer study -RT
-10 -8 -6 -4 -2 0 2 4 6 8 10
92
94
96
98
100
Rel
ativ
e tra
nsm
issi
on, %
Velocity, mm/s
Fe3+2Fe2+O4
IR study
300 400 500 600W a ven u m be r, cm -1
Abso
rban
ce, a
.u.
- F e 3O 4 - C u 0.5F e 2.5O 4
- M g 0.5F e 2.5O 4 - C o 0.5F e 2.5O 4
1 0 0 0 2 0 0 0 3 0 0 0 4 0 0 0
C o 0 .5F e 2 .5O 4
Abs
orba
nce,
a.u
.
W a v e n u m b e r , c m -1
C u 0 .5F e 2 .5O 4
M g 0 .5F e 2 .5O 4
F e 3O 4
HR TEM study - SAED
Fe3O4
Mg0.5Fe2.5O4
Co0.5Fe2.5O4
Cu0.5Fe2.5O4
Cu0.5Fe2.5O4 < Co0.5Fe2.5O4 < Mg0.5Fe2.5O4 < Fe3O4
Co0.5Fe2.5O4
Cu0.5Fe2.5O4
Mg0.5Fe2.5O4
DSC study
Cu0.5Fe2.5O4 < Co0.5Fe2.5O4 < Mg0.5Fe2.5O4 < Fe3O4
After DSC study – Mössbauer analysis
-10 -8 -6 -4 -2 0 2 4 6 8 10
90
92
94
96
98
100
- tetrahedrally coordinated - octahedrally coordinated - octahedrally coordinated - octahedrally coordinated
Cu0.5Fe2.5O4-co-precipitation, after DSC
Rel
ativ
e tra
nsm
issi
on, %
Velocity, mm/s
-10 -8 -6 -4 -2 0 2 4 6 8 1088
90
92
94
96
98
100
- tetrahedrally coordinated - octahedrally coordinated - octahedrally coordinated - octahedrally coordinated
Mg0.5Fe2.5O4-co-precipitation, after DSC
Rel
ativ
e tra
nsm
issi
on, %
Velocity, mm/s
-10 -8 -6 -4 -2 0 2 4 6 8 1088
90
92
94
96
98
100
- tetrahedrally coordinated - octahedrally coordinated - octahedrally coordinated - octahedrally coordinated
Co0.5Fe2.5O4-co-precipitation, after DSC
Rel
ativ
e tra
nsm
issi
on, %
Velocity, mm/s
2 CO + O2 → 2 CO2
Activity
In situ diffuse-reflectance measurements (DRIFTS): catalytic tests were carried out in the reaction of CO oxidation.
Catalytic measurements
1500 2000 2500 3000 3500 4000
smes30m125C
smes30m100C
smes30m75C
smes30mTr
Ar prestoi20h
Wave number, cm-1
Abso
rban
ce,
a.u
.
20 40 60 80 100 120 140
0.0
0.5
1.0
1.5
2.0
Y =0.08-0.00769 X+1.78182E-4 X2
CO
2 ban
d in
tens
ity,
a.u
.
Temperature, oC
CO oxidation on sample M1Reaction mixture Ar+N2+CO+O2
(18 vol.%CO in N)2
Activity
Study of acetone conversion reaction
100 150 200 250 300 350 40020
30
40
50
60
70
80
90
100
Ace
tone
con
vers
ion,
%
Temperature, C
Catalytic measurements
ConclusionsConclusions1. The design of synthesis conditions leads to preparation of single
phase spinel ferrite materials - Fe3O4 , Cu0.5Fe2.5O4 , Co0.5Fe2.5O4 , Mg0.5Fe2.5O4
2. Their particle size is nanodimensional, about 3-12 nm, and changes on varying chemical composition in the following order: Fe3O4 > Mg0.5Fe2.5O4 > Co0.5Fe2.5O4 > Cu0.5Fe2.5O4 .
3. Particles have spherical shape and close size distribution. 4. Study of the magnetic properties of prepared materials shows
- CME behaviour of magnetite sample at RT; - SPM behaviour of all magnetite-type materials at RT and
LNT. 4. Initial catalytic tests reveal their good catalytic activity and the
potential to use materials as catalysts.
Prof. I. Mitov, DScAssist. Prof. B. Kunev, Assist. Prof. N. Velinov, Assoc. Prof. G. Kadinov, Assist. Prof. M. Shopska,
Institute of Catalysis
ACKNOWLEDGEMENTThe authors are grateful to the National ScienceFund of Bulgaria for financial support through Project DO 02-295/2008.