Topotactic conversions of γ-FeOOH and comparative transformation methods of iron oxides in magnetic spinels

Materials

Chemistry

TOPOTACTIC METHODS

E.

and Physics,

10 (1984)

CONVERSIONS OF

OXIDES

IRON

MENDELOVI

Cl,

Laboratorio

R.

OF

y-FeOOH

IN

MAGNETIC

VILLALBA

1010-A,

Received

31

de

579

AND

and

Fisicoquimica

Caracas

579-584

COMPARATIVE

TRANSFORMATION

SPINELS

A.

SAGARZAZU

Materiales,

CIC,

IVIC,

Apartado

1827

(Venezuela)

January

1984;

6

accepted

1984

March

ABSTRACT

The

DTA

taining the

of

a

small conversion

phase)

of

occurs peak

nor

does

it

when

the

appears

sample by

ing

H20.

zed

by

is

XRD

at

tR

materials

sol by

of

disks

of

additives

a

(1 -4%

state

SiOZ)

is

into

are is

reaction

containing

of alkali

the

not

spinels, folby

discussed

of

iron and

halides

as

boil-

characteri-

also

heating

ex-

affected,

alkoxide)

transformations

combination

metastable

magnetic

products

conthat

temperature

(iron

solid

sample shows

y-Fe203

reflux

solid

final

te

y-FeOOH

FeOOH at

This id

the

synthetic

of

resulting and

docroci manganese

(through

pure,

gl’ycerol

spectroscopy.

into

cycles

500”.

the

lepi and

Quartz

with

the

203 in

reacted

with

pressing

-.

y-FeOOH

and

a-Fe

transformation

comparatively magnetic

to whereas

of

1 i zed quartz

the

hydrolysis Starting

crystal

goethite,

y-FeOOH

hamper

1

we1 of

44O”C,

at

othermic

lowed

natural,

amounts

oxides

grindingdiluting

agents.

I NTRODUCTI The ence

ON

solid-state or

vestigated and dide

in

hematite disks,

conversion

absence our may by

a

of

synthetic

like

alkali

laboratory. be

Thus,

to

transformed

combination

of

it

iron

has

magnetite,

heating

oxides

halides

and

has shown

been in

diluted

grinding-pressing

in been that

the amply

presin-

goethite alkali

i ocycles

[1,21.

0254-0584/8?/$3.00

0 Elsevier

Sequoi~/Printed

in The Netherlands

580 In ted

the

context

that

sing

of

pure

y-FeOOH was

the

te

where

transformation

of

al

[4,51.

On

the

formation

into

magnetic in

AI,

Si,

Iepidocroci

(see

Table

using

The

1).

characterize

the

oxides

a

and

Mn,

te,

which

first

described

pure

lepidocroci

iron

oxides

In

this

decomposition

of

in

this

I

by

Mendelovici

may

undergo

trans-

glycerol

At

this

the

stage

presence we

amounts

work

is

of

natural

transformation

structural,

mechano-chemical

framework, smal

of

(y-Fe203)

with

.

f6f

te

te

te

reacting

contains

the

miscellaneous

been

reporproces-

lepidocroci

The

have

etc.

also

maghemi

preserved. during

purpose

study

or

1e

occuring

reaction of

Ti,

tab

thermochemical

after

two-step

been

comminution

cl-FeOOH

me tas

is

synthetic

has

dry

te

no

changes

transformation

like

natural

in

lepidocrocite

hand,

it of

goethi

case,

pseudomorphism

other

the

like

magnetic

temperature

studying

reactions product

latter unlike

and

tives

final

detected,

Iepidocroci

flux

id-state

the

, In

morphological

et

sol

is

oxyhydroxides

[3,41

phase

of

hematite

reare

of

have

of to

at we

addichosen

Si

and

a

Mn

comparatively lepidocrocite

methods.

EXPERIMENTAL

The was

natural

kindly

lepidocroci supplied

After

(Paris). solved

in

rian

1200

was

carried

and

model

1730

(50

by

was

and

model

MnO

total

the

Ti

were to

form

DISCUSS

detected these

to

the

anatysis

16

the

hr

at

by

using

AAS

Fe-Ka

R absorption

solid

Mines

was

disa

Va-

DTA

with

(Stanton

water-free

followed with

radiation

spectroscopy

and g)

245*C,

reacted

it

using

(3

des

mesh),

characterization

mineralogical

I

Wurtemburg’

Nationale (150

diffraction

sample

Lubeneck,

by

boiling

therglycerol

thorough

was-

water.

I ON

analysis Si02

a

Ecole

sieving

chemicat The

for of

and

the

I

as

spectrophotometer)

of

performed

of

of

diffractometer),

chemical

(2.47%)

in

due

AND

labeled

and

powder

model

hydrolysis

RESULTS

A

X-ray

Reaction

cc)

Museum mixing

submitted

283

moanalyzer).

the

sample

spectrometer.

out

(Perkin-Elmer

hing

by

crushing,

HCI

(Philips

te

(1.39%)

separate in

elements

of

the

as

impurities

phase,

this are

sample, ruled

lepidocroci (Table

quartz,

as

therefore out

in

te

shown

sample 1).

The

by

XRR.

possible the

Iepidocrocite

reveals latter No

perturbations study.

Al

is nor

581

1.

Analysis

Constituents

F20;

Table

of

Natural

Cepidocroci

te

by Atomic

FeOa

SiO2

MnO

K20

0.49

1.39

2.47

0.016

Absorption

Spectroscopy b

Ti02

LOI

none

12.38

A’ 203

H20

Total

(total)

%

83.68

a Determined 6

LOI

and

tively

by standard H20-

in

The

infrared

tions

of

bands

are

This of

band

lepidocroci

indicate by

the

UL

same

Shoulders

a)

Infrared

in

here

890

goethite

spectrum reaction

thermal

and

105°C

respec-

to

lepidocrocite.

as

centered

a

band

between 800 the

cm

the -1

samp

these The

at3140 Fe-O-OH

in

e,

Fe-O-H

of

synthetic

and in

absorp-

intensities

IO00

this

as

cm

-1

layers

spectrum

further

confir-

reaction

which to

In

cc-Fe203

at

5

diagram

of

the

the

the

500”,

natural,

endothermic

of takes

second the

lepidocrocite

glycerol

y-Fe

0

2 3 step

well

250

and

(0.25%

place

in

crystallized 301”,

a

steps. by

y-Fe203

at

is

two

accompanied

being

CSI

pellets);

hydrolysis.

lepidocrocite

process

effect

J

600

lcm-1)

natural

decomposition

dehydrates 300°C.

of

with

potactic

shows

and relative

1503

y-FeOOH -

as

at

of

2500~ \

b) after

at

1000

characteristic -1 1155 cm , due

H-bonding

WAVENUMBER

The

745

suggests

presence

3m

1.

at

XRD.

4000

Fig.

sample

displays

and

appears

also te.

the

1020,

positions

vibration

broad

med

at The

1)

(Fig.

practically

stretching

100.26

muffle.

lepidocrocite

.

the

0.32

K Cr 0 2 27

with

by heating

spectrum

[7]

methods

determined

a calibrated

vibrations

OH

were

titration

none

an

In

the

to

exothermic

its

the

step reaction

polymorph The (Fig.

exothermi

to-

first

nature.

lepidocrocite whereas

state

endothermic

transforms of

solid

DTA 2)

c

effect

.

582

Fig.

2.

T”Cthermal

Differential

crocite

(-

30

appears

at

440°C.

exothermic

mg),

at

crystal

1 i ni ty,

of

sample

the

calcined

Synthetic

peak

sented

using

analysis

at

,

When

other

alumina

whereas

the

heating

a

factors

(see

air)

Table

such 1)

may

of

as

lepidocrocite,

508”,

304”[81

(in

natural

reference.

however,

displays

endothermic

effect

material,

beside

as

particle

affect

the

lepido-

the

size

the

is

repre-

degree

and

of

composition

position

of

the

DTA

peaks. The

X-ray

diffractogram

lepidocrocite

with

responding lines

to

are to

goethi

te

4.187

both

The

of

peaks

lowed

by

and

Typical material

after

of

product)

cubic

spine1 .

dark

after

brown

quartz the

by have

is

goethite

disappeared,

of

transformed

are

Traces

at

of at

3.34

i,

and

and

or detected

and

well

with

solid the

at

this the

the

(fi-

pattern

ruled -

(Fig.

also

star-

brown

of

magnetite out

1.4%

SiO2

transformation.

at is

folboiling

dark

diffractogram

resolved

spine1

mixture

X-ray

be (at

spine1

o-FeOOH

for to

disordered

quartz

on

magnetic

since

gives

hamper

the

solid

and

cannot

y-Fe203 like

glycerol,

blackish

a

a

with

reddish-yellow reaction

resembling of

into

reacted

The

magnetic

again

is

the

observed.

disturb

appearance

detected

from

Impurities, not

positions

reflexion

are

glycerol

presence

cor-

diffraction

their

overnight

of

color,

mostly

the

peak

be

strongly

powder. do

undisturbed traces

is

oxide,

However,

centration), the

can

1 ized

6.2j’8i,

y-FeOOH

uninterferred

reacted

hydrolysis

after

at

crystal

lepidocrocite.

small quartz

being

green

peak of and

sample

changes to

hydrolysis,

nal

3b)

washing

we1 1

goethite.

lepidocrocite after

tin

of by

structure,

set

crystalline the

a

sharp

full

diffractogram,

by

oxide

indicates

and

The

synthetic

small

3a)

strong

the

interferred

natural

water.

a order.

recognized

Also

i,

020 on

that

are

i.

2.44

quite

the

indicated

similar

(Fig.

in

this

conIn

fact,

recorded 3b),

3.332

(Fig.

i.

transformed

this The

time goe th i te by

the

583

glycerol

reaction

latter

is The

IR

glycerol Here

lb. as

550

spectrum

of

elimination

the

only

370cm

maghemi

The

inter1

to In

ry.

iron

to

magnetic are

,

iron

broad

of

indicate

presence the

is

reaction

are

presence

the powder. with

represented

bands the

of

magnetic

after

alkoxide,

absorption

which

structures which

a-FeOOH), by

a

a

cubic

wide

range

spine1

contrast,

by

des

-1

*

lepidocrocite,

of

(orthorombic)

and inked

ranged

natural

two

The

0 2 3 ++Y304 [61 analysis the Fe

from

in

displayed of

Fig.

at

magnetite

as

well

te.

open

(y-FeOOH

y-Fe

also

and

and

of

into

inferred

for

octahedra

more

more

iron iron

via

close

an

iron

the case

of

rearintermedia-

hematite,

In

every

layers

easily

alkoxide like

packing,

mechanism

oxyhydroxides

octahedral are

structure

sluggish.

general

these by

hydrogen-bonding,

rigid

hexagonal is

The

produced.

of

of formed

structure

a

in

spine1

are

iron

formed

transformation the

alkoxide

iron

alkoxi

-

formation

b

Fig. b)

3. after

spine1

X-ray

“28 (random powders)

diffractograms

reaction oxide,

30”

4v

5w

60”

with

Q = quartz,

glycerol

and

G = goethite.

hydrolysis. Spacings

20”

of:

a) L= are

IO”

natural

lepidocrocite;

lepidocrocite, given

in

M = Magnetic i.

4”

584

[61

involves

tion

of

condensation

the

iron

corresponds step

to

this

is

not

changed

mine

has

only

y-Fe203

been

0314

Thus,

during

the organic

reported

ted iron

oxide

was mitted

to

spinet In

is

it

disks) was

intensive

is

grinding, more

and

as

or

out

or

hematite

materials, .

had

resulting

in for

a

Here

be

(dilu-

goethite

previously

a defect

the

that

transitional

again,

to

is

oxide.

point

goethite

[1,2,f01

n-hexyla-

product

spinei

to

hematite

reactant

y-FeOOH

final

a magnetic

of

favorable

the

pyridine the

reaction

regenerates of

reaction

magnetic

detected

second

A topotactic such

interesting

whereas

is

03

Fe2c3

also

into

the

sub-

structure

formation

of

which

the

cubic

combination

of

structure. this

heating

solid-state

and

mechanism to

0

. In

f

reac-

calculatedformula

configuration

. In this which

transformed,

thermodynamically

Fe

+2

oxidation-reduction whose

*+

transformation

iodide

ly

Fe3

reagents

basis,

compound

readi

+3

initial

[9]

solid-state

atkali

product

transformation.

(magh emite)

the in

and

a

to

the

using

On a comparative during

Fe2

hydrolyzes

C3H803.

transformation

glycerol

giving

E(C3H5

compound

glycerol,

of

oxide,

the

with

cycles,

glycerol,

magnetic

ficant

mechanism,

grinding

the

spinels

changes

in

as

is

color

which well

involves

as

transition

accompanied

and

in

the

chemical

of

the

iron

by

magnetic

a

in

iron

reaction

oxide

materials

reduction

and

signi-

properties.

REFERENCES

1

E.

Mendelovici

2

S.

Yariv

3

E.

Mendeiovici,

(1982)

4

E.

E.

E,

Mendelovici,

Fuls, (1970) White

8

R,C.

Mackenzie,

Academic

10

S.

Acta,

Materials

R.

Vi llalbe

and

A,

Sagarzazu

and

S.

Nadiv

I.

A.

36

Chemistry,

(1980) 5

25.

(1980)

37.

Sagarzazu,

R.

Vijlalba,

Mat.

Res.

Bull,,17

and

Lin,

J.

of

Materials

Sci.

and

Press,

Desiraju Yariv,

(1979)

and

Fripiat

J .J.

Ciays

and

Clay

Minerals,

53.

W.6,

G.R.

Mendeiovici,

Rodrique

L.

7

9

Thermochim.

press].

P.F. 1;

Yariv.

1017.

Mendelovici,

(in 6

and

S.

241.

(1982) 5

and

E. 519.

R.

Roy

Am.

Miner.,49

Differential New York, and

M.

Mendelovici,

Rao.

(1964)

Thermal London, Ma_t. R.

Res.

Villalba

1670.

Analysis. p.

Vol,

1,

1970

276. Bull.,~ and

M.

(1982)

443.

Cohen.

Nature,Z;iP