study of nanosized ferrite materials prepared by co …7ncc.unionchem.org/presentations/7ncc-5-o4-z...

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.