- Email: [email protected]
On the mechanism of sulphurization of copper
t,he theory information
of Wagner. t3) In order to obtain further about the mechanism of this process
t,he kinetics
of growth
of both sulphide
scale layers
n-as investigated. Metal sheets 4 x 3 x 0.5 cm were sulphurized liquid
sulphur
experiments
at 444°C
varying
from 3 to 60 min.
the
time
in
of the
After having separated
the scale layer from the metal sheet, parts of scale formed
on principal
surfaces
were cut
out.
Scale
fragments formed at corners could not be investigated because of the decrease of reaction rate t)here (related to the scale Fro. 5. Slip indent&on
lines and cracks around a microhardness on the ( 1 IO) surface of a MgO crystal.
for the opportunity
to discuss the results of this work
with him.
A. S. KEH Edgar C. Bain Laboratory for
J. c. 31.
Fundnmestal
Y. T. CHOU
Resea,rch, United
States Steel Corporation Cen,tey, Monroeville,
LI
boundary was
the
mechanism
of
350”--444°C law;
occurs
AW(‘)
inner
layer
was determined.
its
mass
investigations
were carried out in the case of scales
formed
on both surfaces of the sulphurized
tions.
The relative short
the values
for both
surfaces
amounted gations
times
(which
there was practically
between
of AW
and
of a given
sometimes
AW(‘)
not
determined For longer
15 rnin) the difference
to 20 per cent.
The
investi-
that the scale formation
process occurs in accordance
k = the parabolic
did
no difference
specimen.
times (exceeding
have demonstrated
was
It has been st’ated that
sulphurization
sulphurization
prcpara-
error of the measurements
&5 per cent.
IO min)
These
lvith the parabolic
law
rate constant,
This result agrees well with previous investigations in liquid
in accordance
sulphur
at
with a parabolic
from this it must be concluded
layer formed
the porous
corresponding
sulphurization
of copper
of
mass
t = time of sulphurization.
of copper*
The sulphurization
area
the
to the area unit AW was calculated.
where On
and
separated
having
exceed
References 1. lt. .J. STOKES, T. 1;. JOHNSTON and C. H. Lr, I’l~il. Mcxg. 3, 518 (1968). 2. J. \Y.MHBURE;, A. E. GORUM and E. R. PARKER, Tmns. Amw. Inst. Min. (Xetflll.) Engrs. 215, 230 (1959). 3. il. H. COTT~ELL, Tmnx. Amer. Inst. Min. (Metall.) Eagrs. 212, 19% (195X).
surface
corresponding
after
Pennsylvania
The
integrated
After
approximately
Research
effect.(**j))
graphically
that the scale
carried
out
by the authors
The relation between
by another
method.(l)
(AW)2 and t is shown in Fig. 1
as a straight line.
on the surface of the metal is compact
and that the diffusion of one or both reagents through the scale layer is the slowest step which determines Using radioactive rate of sulphurization.(l)
the
sulphur as tracer (S3j) the authors have demonstrated that under the conditions sulphide
scale
on
copper
used the formation proceeds
of the
exclusively
by
outward diffusion of the metal.(2) Since the sulphide
scale on copper
consists of two
distinct layers it must be assumed that the mechanism of formation of these layers is different. The outer layer which forms the main part of the scale is compact, while the inner one is porous and finecrystalline and can be easily separated (mechanically) from the outer scale layer. The formation of a two-layer scale in this case cannot be explained by
I 0
5
IO Time,
FIG. 1. Sulphurization 444T.
15
20
25
min
of copper Parabolic
in liquid plot.
sulphur
at
LETTERS
TO
THE
697
EDITOR
According
to Rees@)
by the following cu &
this process
can be described
equat’ion:
F)I (3 ~ Zy)Cu+l + yCu I? + L’e-l + JS$J) (5)
Cu2+ denotes an electron free electrons
formed
diffuse via cation vacancies direction
“hole”.
where they
The decomposition
by equation
(5) appears
process
and electron holes in the
of the scale surface,
with sulphur.
Copper ions and
in the decomposition
combine
process
described
to be the slowest
which determines rate of formation
process
of the inner layer.
Special appreciation is due to Prof. dr. L. Czerski for his help and suggestions. Time
FIG. 4. Formation
,
S. ~tRO\VEC
min
of inner scale layer at 444°C. plot,.
Department of Genera,1 and
Linear
Coal Chemistry
School of &%&g The
growth
described
of the inner
by the following AW’i’
where the index “2
layer
can however
be
References
= k’i’t
(2)
The plot of the rate of formation
of the inner scale
layer is shown in Fig. 2. is therefore not constant
increases with increasing time of experiment be described
by the following A W(l)jAW
but
and can
equation
= (W/2/k)@
(3)
1.
L.
CZERSKI,
fi.
linear
formation
rate
inner
not by diffusion,
occurring
scale
diffusion
crack is formed
In the case of equilibrium
deficit,
the dissociation
the
value. cuprous
pressure of
between
cuprous
the minimum
a
and the
The pressure of sulphur vapour
and therefore
sulphide,“)
copper
the metal
pressure,
has
33,
of the reaction
occurring
between
as a
gaseous
is compensated cuprous
cu,_,s
(4)
of sulphur caused by reaction
by the process
sulphide
of the
of decomposition compact
outer
(4) of
layer.
in
von Versetzungen
ist bisher durch die &tzung,(z)
bei Eisen und bei Nickel durch chemische
;itzungc3t4)
und
thermische
bei
Fe-Ni-Legierungen
Atzung.(j) Literatur
Unseres noch
.Legierungen
be formed
Versetzungen
Siliziumeisen (Trafoblech) entwickelte elektrolytische
chemische
can
fiir
Eine Sichtbarmachung gelungen bei von Morris(l)
This means that on the metal
(2 - .- x)Cu + _3sp *
the
c&2%.
Fe-Ni-Legierungen*
sulphide
sulphur and metal
where II:< y. The consumption
xtzverfahren
The
as a consequence
the metal surface
and p-semiconducting
product
ROCZ?l.
May 12, 1959
as a result of the
in this space is equal to the dissociation
surface
iTERBER.
layer
boundary.(fi)
proceeds
of copper;
between
growing scale layer. Cu,_,S.
T.
2. J. MIPULSKI, S. MROWEC, I. Srrro& and T. Wmmx, Roczn. Chem. 33, (1959) In press. 3. C. WAGNER, Z. phys. Chews. 21, 2.i 1!133; 1hhl. 32, 447 (1936). 4. L. CZBXSK~ and 6. PATZAU, Archiw. Ghm.-Hutn. Pd. Alid. A~~fu_Lk. 2, 353 (1954). 5. H. ESGELL, Acttr Met. 5, 695 (1957). 6. K. HAITFFE, Oxydlxtim van Jletrrllen unrl Jletrr/le!Jierun!/Pn. Springer, Berlin (1956). 7. 12. HIMHAM, J. Phys. Sm. Jtrprrn 6, 422 (1951). 8. a. REES. Chemistry of the Ikfect Solid Strctr. Methum London (1954).
but by the chemical
at the phase
process of sulphurization outward
sulphide
and
shows that the rate of growth of this layer
is determined reaction
of
~fROWEC
(1959) In press.
* Received
The
ard Metallurgy
Pola,nd
linear equation:
refers to the inner layer.
The ratio AW(‘)/AW
Krakow,
berichtet
Atzung
Mssens
nicht von Im
ist
iiber
(insbesondere
worden.
durch
dagegen
Versetzungen mit
in
elektrolytische in
500/b Fe,
folgenden
werden
der oder
Fe-NiSOY// Xi) solche
At’zverfahren mitgeteilt , die Versetzungen in rjO/SO Fe-Ni-Legierungen mit verschiedenem Kckristallisationszustandt an 0,l bzw. 0,1:5 mm dicken Rlechen sichtbar machen. Kleinwinkelkorngrenzen
allcin-ohne
Subgrenzen
of Wagner. t3) In order to obtain further about the mechanism of this process
t,he kinetics
of growth
of both sulphide
scale layers
n-as investigated. Metal sheets 4 x 3 x 0.5 cm were sulphurized liquid
sulphur
experiments
at 444°C
varying
from 3 to 60 min.
the
time
in
of the
After having separated
the scale layer from the metal sheet, parts of scale formed
on principal
surfaces
were cut
out.
Scale
fragments formed at corners could not be investigated because of the decrease of reaction rate t)here (related to the scale Fro. 5. Slip indent&on
lines and cracks around a microhardness on the ( 1 IO) surface of a MgO crystal.
for the opportunity
to discuss the results of this work
with him.
A. S. KEH Edgar C. Bain Laboratory for
J. c. 31.
Fundnmestal
Y. T. CHOU
Resea,rch, United
States Steel Corporation Cen,tey, Monroeville,
LI
boundary was
the
mechanism
of
350”--444°C law;
occurs
AW(‘)
inner
layer
was determined.
its
mass
investigations
were carried out in the case of scales
formed
on both surfaces of the sulphurized
tions.
The relative short
the values
for both
surfaces
amounted gations
times
(which
there was practically
between
of AW
and
of a given
sometimes
AW(‘)
not
determined For longer
15 rnin) the difference
to 20 per cent.
The
investi-
that the scale formation
process occurs in accordance
k = the parabolic
did
no difference
specimen.
times (exceeding
have demonstrated
was
It has been st’ated that
sulphurization
sulphurization
prcpara-
error of the measurements
&5 per cent.
IO min)
These
lvith the parabolic
law
rate constant,
This result agrees well with previous investigations in liquid
in accordance
sulphur
at
with a parabolic
from this it must be concluded
layer formed
the porous
corresponding
sulphurization
of copper
of
mass
t = time of sulphurization.
of copper*
The sulphurization
area
the
to the area unit AW was calculated.
where On
and
separated
having
exceed
References 1. lt. .J. STOKES, T. 1;. JOHNSTON and C. H. Lr, I’l~il. Mcxg. 3, 518 (1968). 2. J. \Y.MHBURE;, A. E. GORUM and E. R. PARKER, Tmns. Amw. Inst. Min. (Xetflll.) Engrs. 215, 230 (1959). 3. il. H. COTT~ELL, Tmnx. Amer. Inst. Min. (Metall.) Eagrs. 212, 19% (195X).
surface
corresponding
after
Pennsylvania
The
integrated
After
approximately
Research
effect.(**j))
graphically
that the scale
carried
out
by the authors
The relation between
by another
method.(l)
(AW)2 and t is shown in Fig. 1
as a straight line.
on the surface of the metal is compact
and that the diffusion of one or both reagents through the scale layer is the slowest step which determines Using radioactive rate of sulphurization.(l)
the
sulphur as tracer (S3j) the authors have demonstrated that under the conditions sulphide
scale
on
copper
used the formation proceeds
of the
exclusively
by
outward diffusion of the metal.(2) Since the sulphide
scale on copper
consists of two
distinct layers it must be assumed that the mechanism of formation of these layers is different. The outer layer which forms the main part of the scale is compact, while the inner one is porous and finecrystalline and can be easily separated (mechanically) from the outer scale layer. The formation of a two-layer scale in this case cannot be explained by
I 0
5
IO Time,
FIG. 1. Sulphurization 444T.
15
20
25
min
of copper Parabolic
in liquid plot.
sulphur
at
LETTERS
TO
THE
697
EDITOR
According
to Rees@)
by the following cu &
this process
can be described
equat’ion:
F)I (3 ~ Zy)Cu+l + yCu I? + L’e-l + JS$J) (5)
Cu2+ denotes an electron free electrons
formed
diffuse via cation vacancies direction
“hole”.
where they
The decomposition
by equation
(5) appears
process
and electron holes in the
of the scale surface,
with sulphur.
Copper ions and
in the decomposition
combine
process
described
to be the slowest
which determines rate of formation
process
of the inner layer.
Special appreciation is due to Prof. dr. L. Czerski for his help and suggestions. Time
FIG. 4. Formation
,
S. ~tRO\VEC
min
of inner scale layer at 444°C. plot,.
Department of Genera,1 and
Linear
Coal Chemistry
School of &%&g The
growth
described
of the inner
by the following AW’i’
where the index “2
layer
can however
be
References
= k’i’t
(2)
The plot of the rate of formation
of the inner scale
layer is shown in Fig. 2. is therefore not constant
increases with increasing time of experiment be described
by the following A W(l)jAW
but
and can
equation
= (W/2/k)@
(3)
1.
L.
CZERSKI,
fi.
linear
formation
rate
inner
not by diffusion,
occurring
scale
diffusion
crack is formed
In the case of equilibrium
deficit,
the dissociation
the
value. cuprous
pressure of
between
cuprous
the minimum
a
and the
The pressure of sulphur vapour
and therefore
sulphide,“)
copper
the metal
pressure,
has
33,
of the reaction
occurring
between
as a
gaseous
is compensated cuprous
cu,_,s
(4)
of sulphur caused by reaction
by the process
sulphide
of the
of decomposition compact
outer
(4) of
layer.
in
von Versetzungen
ist bisher durch die &tzung,(z)
bei Eisen und bei Nickel durch chemische
;itzungc3t4)
und
thermische
bei
Fe-Ni-Legierungen
Atzung.(j) Literatur
Unseres noch
.Legierungen
be formed
Versetzungen
Siliziumeisen (Trafoblech) entwickelte elektrolytische
chemische
can
fiir
Eine Sichtbarmachung gelungen bei von Morris(l)
This means that on the metal
(2 - .- x)Cu + _3sp *
the
c&2%.
Fe-Ni-Legierungen*
sulphide
sulphur and metal
where II:< y. The consumption
xtzverfahren
The
as a consequence
the metal surface
and p-semiconducting
product
ROCZ?l.
May 12, 1959
as a result of the
in this space is equal to the dissociation
surface
iTERBER.
layer
boundary.(fi)
proceeds
of copper;
between
growing scale layer. Cu,_,S.
T.
2. J. MIPULSKI, S. MROWEC, I. Srrro& and T. Wmmx, Roczn. Chem. 33, (1959) In press. 3. C. WAGNER, Z. phys. Chews. 21, 2.i 1!133; 1hhl. 32, 447 (1936). 4. L. CZBXSK~ and 6. PATZAU, Archiw. Ghm.-Hutn. Pd. Alid. A~~fu_Lk. 2, 353 (1954). 5. H. ESGELL, Acttr Met. 5, 695 (1957). 6. K. HAITFFE, Oxydlxtim van Jletrrllen unrl Jletrr/le!Jierun!/Pn. Springer, Berlin (1956). 7. 12. HIMHAM, J. Phys. Sm. Jtrprrn 6, 422 (1951). 8. a. REES. Chemistry of the Ikfect Solid Strctr. Methum London (1954).
but by the chemical
at the phase
process of sulphurization outward
sulphide
and
shows that the rate of growth of this layer
is determined reaction
of
~fROWEC
(1959) In press.
* Received
The
ard Metallurgy
Pola,nd
linear equation:
refers to the inner layer.
The ratio AW(‘)/AW
Krakow,
berichtet
Atzung
Mssens
nicht von Im
ist
iiber
(insbesondere
worden.
durch
dagegen
Versetzungen mit
in
elektrolytische in
500/b Fe,
folgenden
werden
der oder
Fe-NiSOY// Xi) solche
At’zverfahren mitgeteilt , die Versetzungen in rjO/SO Fe-Ni-Legierungen mit verschiedenem Kckristallisationszustandt an 0,l bzw. 0,1:5 mm dicken Rlechen sichtbar machen. Kleinwinkelkorngrenzen
allcin-ohne
Subgrenzen