A-SEMANA 1-CARRAZANA Ferrimagnetic Paper in Situ Method

8/9/2019 A-SEMANA 1-CARRAZANA Ferrimagnetic Paper in Situ Method

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IEEE TRANSACTIONS ON MAGNETICS, VOL.

3 1 ,

NO. 6 NOVEMBER 1995

agnetic Paper Obtained By In Situ Synthesis Of Substituted Ferrites

by: Jorge A. Carrazana-Garcia; M. Am uo Lbpez Quntela ; Jose Rivas Rey.

(Physical-Chemistry Dept.,

Univ of

Santiagode Compostela, Spain,

postal

code: 15706, Spain)

Absfruct-

A procedure for prod ucing magnetic paper by in

situ synthesis

of

substituted (CO,

Ni) ferrites is described

Ferrites are formed in the presence of cellulose fibers and then

forced

to

enter into the fiber lumen where they stay protected

from mechanical influences. The remaining particles are

washed out of the fibers leaving its external surface clean,

so

that its papermaking properties are not affected. Multilayer

papers were prepared in which the colored magnetic layer

is

hidden behind white printable surfaces. Finally, the magnetic

properties of the different kinds of obtained papers are

compared with typical com mercial stan dards, like subway

tickets and airport boarding passes.

I. INIXODUCTION

The magnetic properties are an added value to the

traditional characteristics of paper, &ng it an attractive

objective in such diverse fields

as

recording media, novel

handling systems and

security

paper uses.

In

the literature

there are reports about :;uperparamagnetic paper obtained

through in situ synthesis of femtes [1,2,3] and concerning

ferrimagnetic paper obtained by lumen loading its fibers

[2,3.4] with commercial magnetic pigments (magnetite and

maghemite). It has been established that in order to diminish

the loss of mechanical strength and the poor retention of the

inorganic particles, it is necessary to accomplish the

introduction of the powder into the lumen of cellulose fibers

and then effectively wash the outer surface

[5 6 7].

In this

way, the lumen loading c m be considered a well-established

method for introducin g powder ad ditives into cellulose fibers

to give them important characteristics mith mini

damage to their paperrnaking behavior E8f.The in situ

approach allows a better control of the paper magnetic

properties without

a

considerable injury to their mechanical

properties. At the same time, it

permits

a high variety in the

type of charge loaded into the lumen of the fibers. We report

in this work the obtainment of papers

with

sigmficant values

of coercive field combining the two procedures (in situ

synthesis and lumen loa&ng). Substituting a fraction of

ferrous ions by cobalt, nickel and strontium ions in the

reaction of synthesis of the magnetic material with the

presence of cellulose fibers, the paper obtained exhibits

coercive fields, saturation and remanent magnetization

comparable to commercial standards obtained by more

complicated non i n situ procedures, like a magne tic band of a

subway ticket (as shows

fig.l),

or an i rport boarding pass.

In

our

work w e have used pape r pulp obtained from

Manuscript received Fr eb uay 17 ,1995

J.A. Carrazana; e - ma il u s c q f , j c g @c e s g a . e s Th i s w or kw a s suppo r t ed

by the Sunta de Galicia with the project XU GA 206 12B93 and thanks

to

a

doctoral fellowship of the Insti lkto de Coo pe rac ih Iberoamericano.

sugar cane bagasse. This is, to our knowledge , the first work

reported

wth fibers derived

from

plants other than trees.

11.

EXPERIMENTAL

Mdm zk.

Chemicals reagent grade were used: (F eCI 24H 20,

CoC1~6H20,

BaC12.2H20) from Merck and (NaOH.

Ni N03)26H20) from Aldrich. Suspension and solutions

were prepared with bidistilled water. In generai, no special

care was taken to isolate the system from atmospheric

oxygen. In fact, the u lterior oxidation from Fe2+ to Fe3+

(necessary or the femte formation) is achieved by means of

the dissolved 02 mainly during stirring. In some

experiments we use kr ft pulp from

eucalyptus ssp

but the

pM cipal f i k r source was chemical paper pulp o'otain2d from

sugar

cane bagasse both bleached and not bleaclted.

A

diagram of the process for malung the

magnetic paper

ispresented

in

fig.2.

m

M

i

H 1 - 1 0

Fig.1. Hystsrssis

imps-

.M m d g of

f m t e ) Vs.

Oe) at roan

temperature

*.-*- maget ic band of

a

subway ticket,

-

aper

I

see

t a b k

I)

A. Magnetic

Paper Formation

Syn fAeh .A l g 3g sample of pulp is dispersed i water

200

- 5

mL) using a laboratory mechanical stir:cr with

digital speed control. The temperature is fixed a t tke Gesired

value introducing the reactor in a thermostatic tath or using

a jacketed glass. Quantities of inorganic chemicals were

calculated s that the final fem te concentration was'in the

range from 0.04

M

to

0.1

M. Cations were added, generally

as

hydrated chloride salts, after which (about five minutes

later for ion exchange) stoichiometric amounts of NaOH

were aggregated. Thereafter, the formation of a dark green

precipitate can be observed, if the experimental conditions

established (temperature, ions nature and concen, r a h n , etc.)

0018-9464/95 04.00 995 IEEE


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3127

aq.

suspens ion

of paper pulp

in si tu synthes is of

I

surface c leaned

Fig.2. Diagram of the process

are the optimal for the formation of Green Rust. After the

particle formation, the system is aged at the same

temperature for several hours

1 h- 16h).

Besides the precipitation from the liquid phase, the in

situ approach introduces an important aspect in this

analysis: the formation of particles directly in the cellulose

walls [9]. The pulping (a step in the obtainment of paper

pulp from its vegetal source) dissolves lignin and most

hemicelluloses in fibers, leaving their

walls with

an irregular

structure of micropores and chaps. In addition, the chemical

cooking provokes the combination of cellulose with anionic

functional groups that can capture metai ions (in

this

case

MP that prec ipitate as hydroxides when a n alkali is added to

the suspen sion. In that way, part of the

M(0W2

is formed

directly associated to the fiber in the bulk of its tvalls.

Another strong influence of cellulose fibers in the system is

that local pH inside the fiber wall is much lower than in the

volume of the liquid

[lo],

a fact to take into account during

pH-sensitive reactions, like the fem te synthesis [

1

1 o

151.

Impregnation. The suspension is strongly stirred (2000

rpm or more) during 1 hour vrith a teflon stirring paddle,

forcing the particles to ente r the lum en of fibers. Th is process

can readily be followed with an optical microscope. Particles

can only penetrate into the lu men of the fibers, if they have

diameters lower

th n

the dimensions

of

pits (little holes

distributed along the fiber walls which communicate the

lumen with the outside). The in-out

flus

caused by turbulent

agita tion durin g the im preg natio n step introd,Jc::s the

particles into the lumen.

The formation of ferrite in the fiber walls arri t.ie lumen

loading determine the level of impregnation

th-

t are

achieved during the process. Among the Iariabies that

control

this

aspect are the particle size and the effect- eness

of agitation during the impregnation step.

Also

the ;;Ked at

which precipitation occurs seems to br inq.ortant.

Appropriate control

of

the process permits impregn 1tion to

reach similar levels to those reported for other lum e,i

1

oading

processes. Nevertheless, a good qualih of partlcles formed

can overcome low impregnation levels, as show

:

alues

for paper

I

(see table I)

Table

I. a

b12+

n the starting suspension and their molar ratios; b synthesis temperature; c procedure of addition

of

NaOH to the solution; d c i q w Ilogaphic

phase according;yRD;

e

Hc Oe)of the magnetic paper at room temperature;

f

,g remanent

and

saturation magnetization at room temperature emu/g xfened to

ash content and, in parenthesis, referred to paper mass;

h

ash content (weight per cent

)

of papers obtained,

In the

case of paper

E,

the coiitributio.1 of .adin from

the white layersused, makes impossible the assignationof the ash content to the impregnated ferrite); indicates he presence

of

big p0.25

mm)

particks, gnerally

vitreous and poorly magnetic, contributing to ashes and reducing the specific magnetic parameters.; Q

i

ndicates the presence of a magnetic field during the

synthesis; + indicates that

the f i b

were lumen loaded with presynthesized particlzs, The fmal hvo rows correspond

to

PC

diskette

and he magnet.: band of a

subway ticket,

as

references.

I_ _ _____ _ _ II _ _ ___ _ _ __ _ __ _ _ _ ____LI

a

C

e 11

d

f g ,

Paper cations T

alkali

phase Hc hl r IS

ashes

x

Fe 65OC

solutionjstir.

y-FelO1 7.4 0.95 (.03) 51 (1.8)

3.5

B

Fe 90C

pekts/stU *pFezOl/Fe304

31 4.2 0.4) 59.4(5.7) 9.6

C 8

Fe 65C pellets/stir.

y-Fe~O]iFejO4 56 5.2 (0.2) 43.9(1.7) 3.9

107 17.9 (5.7)- 66.7 (21) 31.8

Fe

65OC pek Wh0 stir y-FezOl

E 8

Fe

65C pellasino stir y-Fe201 . 93 (3.74) (14.1) ?

F Fe/Co = 4/1

25C

pelletdstir

FeOOWCo00H

6

O.l(O.007) ll.l(O.73) 6:j

G Fe/Co

=

411

41C pelletdstir CoFezO4/FesOd 327 18.5(2.05) 62.7 (7.0) 11.1

H FdCo = 211

65OC

pelletdstir

CoFe2O~iFe104 393 19.1 (2.43) 65.1 (8.3) 12.7

I FdCo

=

4/1 90C

pelletdstir

CoFe204/Fej04 333 18.1 (1.34) 61.3 (4.5) 7.4

J Q Fe/Co = 211 65C pelletdnostir CoFel Od/Fe~04 520 4.36(0.66) 17.3 (2.6) 15.1

K FeNi

=

2/1 65C pelletdstir (Ni,Fe)Fet04 52 1.7

0.05) 10

0.32) 3.2

L Fe/TJi = 2/1

9OoC pelletdstir (Ni,Fe)Fez04 54 9.23 (0.5) 44.2 (2.4) 5.4

M

FelCoMi= 2/.5/.5

90C pelletsstir NiFe204 169 10.8

6 .5 )

40.2 (2.4) 6

N Q Fe/Ni

=

2/1

65OC

pelletsnostir NiFe204 83 9.98 (1.7) 42.1 (7.2) 17.4

Fe/Ba = 12/1

90C pelletsstir Fe3O4+BaCO3 83 11 (0.4) 62.9 (2.4) 3.7

P FeBa = 1/1 9OoC pzllstslstir d3a0.yFe20,

5

0.2 (0.01)

9 7

0.5) 5.2

Q Fe/Ba = 111

9oC

pelletsstir

BaFellOls+ 2722 3.3 (0.04) 6.2 (0.08) 1.2

addition

.........................................................................................................................................................................................................................

a-FezOl

PCDisk y-Fe203 717 45.5 76.2 4

7

Fe203 242 10.3 26.1


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3128

(in m u ) at fixed extemal fieldwith temperature (in IC fw

ferrite particles corresponding to paper

I.

LEGEND: kt vs.T at 50 Oe (curve

I),

Washing. The excess particles remaining in the suspension

are filtered out through a 0 .25

mm

sieve. Those particles

adhered at the extemal surface of fibers are removed by

washing. Two procedures were implemented for this

purpose. In the first, discontinuous process, the suspension

of fibers is stirred

1000

rpm) and filtered alternately,

changing the water in every batch. In the continuous

procedure, the suspensi.on is stirred within

a

meshed

cylinder which is placed into

a

glass

nlth

an upper water

outlet. and a water flow from inside to outside of about 2

liters per minute. The particles collected are washed until

negative chloride test, repeatedly decanting the suspension

with the help of a magnet, and drying at 60C. The optical

photograph in fig.3 b shows a cellulose fiber after the

washing step. with its lumen filled with femte particles and

the outer su rface clean, rrxidy to form m agnetic paper.

Sheet formation. Tlhe sheets of paper were formed

pressing the pad of fiber:; formed during the filtration of the

washed suspension in a Buchner funnel, and then vacuum

drying them in an oven at 60C. The colors of magnetic

papers formed range from light brown to black. This is

irrelevant for many of its potential applications, however,

printing demands low colored surfaces, white

if

possible. We

have obtained bi- and tri-layer papers where the colored

magne tic fibers are. behi.nd white printable surfaces. These

multilayer papers were compressed and dried in a press at

90

kglcm', heating the paper on both sides. The

magnetic response of these papers

J

and

E

respectively) are not affected at all by this

inclusion between w ht e layers.

B.

Analysis

Techniques

Structural analysis has been performzd in a

Phdips automatic powder X-ray dffraction

system

(XRD)

goniometer

P W

1820, w3h Cu

K a

radiation, of wavelengths: a1=

1

54439

and

a2=

1.54060 a2/ul intexity ratio of

0.5)

. The obtained diffractograms were

matched with a data base (TAD D+oO) end were

also used for crystallite size estimations

Electron micrographs were take

by a

Phdips

CM

12 transmission electron

microscope with an accelerating voltage of

120 kV.

Paper ashes

were meas ured b;t drying the

sheet at

105C

overnight and the? tuning 4

hours a weighted sample in an oven

at

925C.

The ashes content of pulps were determined

sepa rately for correctlon purpose? g:ving the

values of: eucal?ytus kraft


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3129

Cuba errite. Th e subs titu tion of som e Fe ions by

CO?,

ermits the formation of papers with hlgher values of

Hc. Experiments w ere performed from room temperature to

90C. The spinel phase (C oFe204a n d o r

Codoped

Fe304)

s

formed above 40OC. Below

this

temperature,

a

mix of iron

and cobalt oxyhydro xides, with bad m agnetic response, are

formed.

Typical values of the magnetization parameters of

the samples are reported in table

I

(papers

F

to

J)

Notice

that the Hc = 520 Oe for paper

J

was attained with the

reaction vessel that was placed over a 3000 Oe magnet (like

those marked with n table I) and by adding NaOH pellets

without stirring.

TGA measurements in presence of a magnetic field for

particles charged in paper I, show a sharp fall in the sample

weight above 500C, and the fitted value lies between the

tabulated [16]Tc for magnetite (585C) and cobalt femte

(520C). This seem s

to

indicate the presence of a mixed or

non stoichiometric magnetic phase as c an be expected from

the cationic composition of the starting solution, in this

case: Fe

/CO=

4 1 . Measureme nts of the magnetization

at fixed external field in

this

temperature interval, with a

step of

2

degrees, were performed

wth

DC-VSM at constant

100

Oe and

50 Oe

field. Figure

4

shows the

M

Vs. T

depen dence s obtained and their first derivatives (computed

with finite increments) looking for an estimation for the Tc

[17] by the inflection point in the M

Vs.

T curve. There is

a minimum in the first derivatives at approximatelly 547C

which can

be

interpreted as the presence of a cobaltite with

some defect in its iron conten t.

Blagev and Him [18] have reported a surface doping of

magnetite

wth

cobalt, thanks to an ionic interchange of

solids particles with a CO solution. Following the

suggestion, we redisperse the paper A (formed with femte

charged fibers) in a 0.055 m o m solution of CoC12.6H20at

9OoC for 15 hours. The magnetic values for the paper

formed later: Hc =

5.85

Oe,

Mr

= 0.04 emu/g, Ms = 1.3

emu/g (referred to paper weight) and ashes 3.02

,

do not

seem to jus* Co dop ing in

this

case. Similar results were

obtained with paper

B.

Other ferrites. Look ing for a diversifica tion of the

magnetic charge installed in paper fibers, we used as well

Ni and Ba as substitute cations in the starting solution.

The results in table

I

show that the ferrimagnetic spinel

phase is formed in the first case, with Ni, but not with Ba.

Then, for this last element, we tried another way. The

particles were synthesized without fibers and once washed,

were heated 16 hours at 9OOOC in air and in argon

atmosphere. Finally the fibers were impregnated in a

traditional lumen-loading procedure. The

XRD

of thermal

treated particles shows the presence of barium hexaferrite

phase (13aFe12019) nd hysteresis curves reveal a very high

coercive field, greater than 2700 Oe. However, high

amounts of a-F e2 03 are also formed, and the specific

saturation and remanent magnetization are quite small

(paper

Q).

Other handicaps are that the advantages of in

situ synthesis are lost, and that during the thermal

treatment, sintering occurs,

so

that the fraction of suitable

particles for lumen loading

is

very small. This effect can be

observed in the low ash co ntent of paper Q .

IV. CONCLUSIONS

Magnetic paper with useful range values of Hc,

F r

and

Ms, can be prepared combining the in situ syr-thesis of

femtes and lumen loading of cellulose fibers. The cobalt

femte or Codoped magnetite formed in a we- w q in the

presence of paper fibers, allows the obta inmen t of mhgnetic

papers with coercive fields as high as

500 Oe.

Other

substitute cations (Ni, Ni+Co) can be used in the s m e way

but the values of Hc achleved are smaller. It nas been

observed that the precipitation rate is

an

important miable

in the control of the m agnetic properties of particles formed.

The method developed in this work permits the obtainment

of papers loaded to high levels, with a very good retention of

the magnetic filler and without damage to :heir paper-

making properties. The inclusion of the colored magnetic

layer b e h w x white surfaces improve its sptical

cha rac teristic s and does not affect the magneti,: re;pmse of

the paper.

REFERENCES

[l] R. H.

Slarchessauit, S Ricard

P.

Riouu;

In situ sjnthcis

t f 1

:mites in

cellu losics. Carboh?drate Researches,

Vol

224 pp 133-1 39, : Ic2

[2]

S. Ricard

R.

H.

Marchasault, Preparation

of

in situ niagne ticeliy loaded

cellulox fibers, lat.

Res.Spc.

Sjmp Proc.

Vol

197, pp 319-334, 1990

[3] R H. Marchessauk, P Rious. L. Ra>niond Slag~~eticelldose

libers

and

paper: preparation, processing and properties; Polymer. Vo1.33 . No. 19,

pp 4024-4028,1992.

[4] P.

Rioux,

S.

Ricard,

R H. Marchasault;

The

preparatian

3f

inagnetic

papermaking

fib,

J

of

Pulp and Paper Science, Vcl.12, No.1,

pp J39-J43,

jan

1992.

[5]

H.

V. Green, T. J Fox, AMScallan; Lumen loaded paprt pclp , Pulp &

Paper Canada,

Vol.

83,

No. 7

pp 39-43, 198 2.

[6]M.

L. \filler,

D

. Paliwal; F e effect

of

lumen loading on JIC strength

and optical properties

of

paper,

J of

Pulp and Paper Science.

Vol. 1

I,

No.

3, pp J84-588, may.1985,.

[7]

S .

R Middleton, A M. Scallan; Lumen loading of bleached pulps,

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Pulp and Paper Science,

Vol.

15,

No.6,

pp 5229-52311, nov

1

S9.

81 H. V.

Green,

T. J Foq

A.

M

Scallan; Lumen loaded paper pulp,

s

production and use, Can.Pat. 1152266 1983), Eur.Pat. 0042234 1983),

US

Pat. 4510020 1985).

[9] G.G. Allan et al, The microporosity

of

pulp: the precipitation of inorganic

fillem within

the micropores

of

the cell

wall,

Tappi Journal,

Vol.

77,

NO.

1,

p ~ .

75-178,

Jan,

1992.

[lo]

A.

hl.

Scallan The

pH

inside the fiber wall; in Celkulose Sources

Exploitation

Edited by:

J F.

Kennedy and

G. 0

Philips, Lcndon,

U.K.,

~ ~ 2 1 1 - 2 1 5 ,990.


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3130

[111 T. Sujimoto, E. Matijevic; Formation of uniform spherical magnetite

particles by cristalization from ferrous hydroxide gels,

J.

Coll. Inter. Sci.;

Vol. 74, No. 1, pp. 227-243, march 1980.

[I21 H.

Taniura,

E. Matijevic; Precipitation of cobalt femtes; J. Coll. Inter

Sci., Vol. 90, No. 1, pp. 100-109, nov 1982.

[13] Regazzoni,

E.

Matijevic; Formation of spherical colloidal nickel

ferrite particles

as

model corrosion products, Corrosion-NACE,

Vol.

38,

No.

4, pp. 212-218, april 1982.

[14] R. Massarf V. Cabuil; Syntese en milieu alcalin de magnetite colloidale:

contrde du rendiment et de la taille des particules, J. de Chimie Physique,

Vol. 84, No. 7-8, pp. 967-973, 1987

[15] Y Tamaura, T Itoh, M Abe, Reaction mechanism

of k i

f,,miatioii

by

oxidation

of

Fe (11) ion in aqueous solution, in Adva ices I

Territes,

proceedings of the Fifth C o d on Ferrites, ed by C M Srwwn d and M

J Patru, Trans Tech Pub, Switzerland, pp 83-88, 1989

161 E P Wohlfa& Ferroniagnetic M aterials, North-Holland Physics Pub

msterdam reprint of 1986, pag 460

[17] R. M

Ebzorofi,

Ferromagnetism,

IEEE

Press, New York, 1993. pag

719

[18] R V Blagev, S

J

H i n , Effect of Surface Properties on Cobait

Modifications of Iron Oxides

IEEE

Trans on Mag ,

Vel

28 Vo

5

pp 2382-2384, sep 1992

Fig.

3

Optical photogaphs of celhlose fibers,a: at the begining of the process,

b:after the

washmg

step,

with its

lumen loadedwith ferrite and the outer surface clean

A-SEMANA 1-CARRAZANA Ferrimagnetic Paper in Situ Method

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