Interfacial bonding, wettability and reactivity in
metal/oxide systems
N. Eustathopoulos, B. Drevet
To cite this version:
N. Eustathopoulos, B. Drevet.
Interfacial bonding, wettability and reactivity in
metal/oxide systems. Journal de Physique III, EDP Sciences, 1994, 4 (10), pp.1865-1881.
<10.1051/jp3:1994244>. <jpa-00249229>
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J.
Phvs.
III
Fiance
(1994)
4
1865-1881
1994,
OCTOBER
1865
PAGE
Classification
Phj.tic.i
Ab.itia<
68.10C
t-1
68.22
73.40N
wettability
bonding,
Interfacial
reactivity
and
metal/oxide
in
systems
N.
Eustathopoulos
j')
Laboratoire
CNRS,
j2)
Section
Grenoble
en,ed
Rdsumd.
est
d[ectroniques
(dtats
observd,
Caractdrisd
rajouter,
mdta[/oxyde.
de
entre
le
peut
dtre
d'ox
dans
Cet
solutd
fortes
states).
B
As
both
result,
a
CENG,
h 90°.
Un
17
For
oxygen.
by
un
des
O-B
interactions
une
B
la
moddrdes.
l'oxygbne
provenant de
diminution
va[eurs
de 9 jusqu'h des
conduire
h la
prdcipitation
peut
[e
la
force
des
This
di.iir)/titian
du
solute
B
this
also
can
new
perfect wetting
can
favourable
a
lead
to
the
features
be
on
to
a
the
the
oxygen
decrease
ec.ipitatir)n at
metallic
bonding.
pi
of 9
the
metal/oxide
the
sen~e
strength
the
interactions,
O-B
clusters,
lead
phase
in
OB
can
60°.
de
[iquide
substrat
Pour
de
phase
mouillage
nouve[le
h
est
develop
weak
interaction~
with
iono-cova[ent
oxides
metals
interfacial
chemical
(low density
physical (van der Waah) and
non-wetting i~ generally observed~ the contact angle being larger
of wetting can be
obtained
by alloying the metal with a reactive
of
mechanism
interactions
cbtd
d'une
est
l'interface
l'interface
l'ordre
de
[age
mouil
favorablement
B
OB,
clusters
moderate
adsorption
Martyrs,
des
rue
d'amdliorer
moyen
capable de modifier
d6pendant de
mdcanismes,
solutd
deux
depending
mechanism~
two
i,ia
substrate.
1.
be
Improvement
capable of modifying
dissolved
When
non-reactive
can
29
UA
1994)
supdrieur
Pour
de
[~d[dment
degrees.
achieved
the
i,ia
entraine
O-B.
which
electronic
interface
Grenoble,
iono-covalent
(isolantl
mdtal pur non
rdactif et un oxyde
Waalo et chimique
interactions
de type physique (van der
mauvais
moui[[age est
faib[e
densit6).
Par
con~dquent, un
dissous.
adsorption
Pure
Abstract.
(insulatom)
90
INP
France
un
de
obtenu
est
par
d'Hdres
caractkre
partiellement mdta[lique, [e
Lorsque ce produit posskde un
parfait pouvant dtre obtenu.
de fagon ~ignificative,
moui[[age
presque
un
amdliord
solute
faible~
mdcanisme
interactions
l'interface.
than
entre
de
par
l'oxygdne
modifide
Cedex,
20./une
contact
par un angle de
matrice
mdtallique,
ef'fet
B et
yde. Ce
accepted
interfaciaux
une
Mdtallurgique~,
Martin
CEA-DTA-CEREM-DEM,
interfaciale
assurde
Physico-chimie
France
1994,
liaison
La
gdn6ralement
et
Saint
Matdriaux,
9.
Febiuaiy
(2)
Drevet
3840~
des
Cedex
28
B.
75,
B-P.
Gdnie
de
and
Thermodynamique
de
ENSEEG,
38054
(Ret
(')
of the
solute
B
coming
down
to
~olid-side
wetting
can
can
from
60°.
=
of
be
For
the
solute
between
modify
the
This
interface.
interactions
the
interface
strongly
be
B
and
liquid-side
of the
of
oxide
di,i.ioiutioii
strong
can
O-B
of
the
interactions,
a
improved
new
and
phase.
nearly
obtained.
Introduction.
Interfaces
strategic
between
materials
ceramics
with
better
and
metals
are
mechanical~
of
practical
thermal
and
importance for the development of new
electronic
properties. Several fields of
1866
JOURNAL
materials
science
processing,
fundamental
interface
N°
III
joining~
technology. In
metal/ceramic
e.g.
packaging
microelectronic
metal/ceramic
the
of
concerned,
are
PHYSIQUE
DE
film
thin
or
liquid
involves
state
processes
composites
matrix
metal
formation
the
many
cases,
which
for
IO
wettability
is
a
property.
characterized
angle b
by the
usually
is
described
by
line
(Fig.
This
triple
I).
angle
wettability
metal/ceramic/vapor
is
The
formed
liquid
Young's
the
at
well-known
the
equation
«~v
where
«~v~
and
«~v
liquid~
L
«~~
~~~
"sL
«sv
=
energies
interfacial
the
are
6
cos
between
(S
phases
two
solid,
=
vapor).
V
=
=
VAPOR
LIQUID METAL
CERAMIC
Fig.
Definition
I,
the
of
thermodynamic
The
angle of
contact
work
of
adhesion
«sv
=
per unit
and a
work
solid/vapor
that
area
Young-Duprd
«~v(
=
W
be
can
ceramic
solidification
and
solid
of
states
metal/ceramic
A
drop
the
metal~
and
can
the
surface
by Duprd
(2)
«sL
solid-liquid interface
a
equations (I) and (?), one
separate
to
+
follows
as
«Lv
;ubstrate.
cos
the
contact
tension
of
the
resulting
of
measurements
provide useful
information
to
obtain
obtains
a
the
(3)
6
angle
between
metal.
W
are
on
As
«~v
roughly
the
the
and
liquid
metal
«~~
applicable
mechanical
and
vary little
both to
behaviour
the
with
liquid
of
the
6
and
interface.
elevated
At
«~v.
by measuring
calculated
by determining
and
defined
+
flat
a
Combining
interface.
W
Thus~
on
performed
be
must
liquid/vapor
equation
liquid
a
W
W
is the
SUBSTRATE
of
temperatures,
the
liquid
is
metal
drop
sessile
set
on
a
flat
method
substrate
is
and
generally
its shape
used
is
to
determine
recorded
and
used
to
liquid metal together with the
angle. In practice,
contact
experiments are performed under high
inert or reducing atmosphere and
substrates
of
vacuum,
controlled
purity and roughness (R~ < 20 nm
needed in order that the experimental 6 does
are
differ
from
Young's angle (Eq. (I)) by more than 2°.
not
Interfaces
between
metals
and
ceramics
usually divided in two classes, I-e- nonpure
are
for
the
of
contribution,
reactive
and
reactive
As
shall first recall in the
contents
systems.
our
we
wetting
behaviour
of
previously
described
in [1, 2]. In
section
the
nofi-ieactii>e
systems,
next
focus
with
particular
emphasis
the
governing
shall
reartii'e
sections~
other
systems~
on
on
we
compute
the
surface
tension
of
the
N°
WETTABILITY
lo
concepts
Wetting
2.
wetting.
of
parameters
developed
Non-reactive
being
in
the
of
substrate
few
a
defined
be
the
range
in
parts
this
for
valid
metalliono-covalent
systems
can
ceramic
of
be
to
oxide
substrates
but
the
ceramics.
reactivity
which
the
the
on
the
of
slight
a
of
amount
order
in
consists
maximum
the
per
metals.
typically found in
experimental and
modelled
concentrations
of
systems.
liquid metal~
million
(ppm), I.e.
in
oxide
concern
families
for
systems
as
paper
other
1867
SYSTEMS
METAL-OXIDE
IN
given
results
excepted
non-reactive
in
dissolution
of the
Most
are
REACTIVITY
AND
dissolution
impurity
metallic
angles and
adhesion
in
non-reactive
previously
Wetting
is
[l~
2].
generally
systems
marginal or poor~ as shown in table I, and W represents typically a few tens of percent of the
cohesion
work of
2 «~v) (Tab. I). It has
been
proposed [3, 4] that
metal
(W~
W~ of the
physic-al (van der Waals)
interactions
and oxide~
resulting from dispersion
between
metal
forces [3] or
from
image forces [4], could
for
these
results.
It also
from
account
seems,
chemical
considerations
[5-7]~ that
for
non-reactive
metal/oxide
theoretical
couples~
even
Both
metalliono-covalent
results
oxide
have
contact
on
been
reviewed
~
interactions
following
localised
interface
the
at
covalent
for
where
and
oxide
V~
oxides.
partial
the
metal
M
and
are
are
E.iperimental
I.
iac.trim
neutral
r)I
~~$tM1
not
both
data
,qa.<
Met~
(if'
[38].
adhesion
of
this
On
metal
a
M
basis,
on
the
iono-
an
~l~~'lM lj
+
alumina
oxide
enough
strong
responsible
bond.
interfacial
the
of
(4)
enthalpies of mixing at
respectively. N~ is the
C is an empirical
constant
metalliono-covalent
they
However,
hi,qfi
of the
non-reactive
interface
the
Table
volume
the
at
bonds.
of
are
the
in
M'
liquid metal.
Equation (4) gives good results for
molar
the
bonds
and
metal
in
work
M
J
W(,j~j
the
i~1/~~2/3
~~'
W(j~j
involved
are
equation has been proposed
M'O~ oxide [8, 9] :
for
and
W
destroy the
to
the
poor
8
metallic
observed
nr)n-ieuc.tit,e
(°)
122
1373
130
than
for
in
these
metal.(
and
refractory
that
seems
der
van
Waals
neighbourhood
in the
bond
oxygen
number
[10]. Thus~ it
stronger
systems.
on
.;aj>pfiiie <irider
W/W~
W
0 27
215
II7
1373
Avogadro~s
equal to 0.2
silica
are
wetting
li)r clilfbient
T @C)
[9] and
interface
of
dilution
infinite
0.24
0.12
0.17
450
l100
The
been
the
influence
recently
pressure
x=0
to
conductivity
has
2, I
melt
been
oxygen in the
x=10~~
has
been
of the
observed,
INFLUENCE
M
metal/oxide
and wetting has
the
adhesion
on
gold/monocristalline Ti02
system. Decreasing
increase
of x
furnace by fifteen
orders of magnitude,
an
produced~ leading to an
of the
electronic
increase
103. Despite these changes, no significant
variation
of 6
predictions of theoretical
models [4].
with
charged defects in the
by Chabert [I I] for
oxide
the
-,
partial
from
of
studied
can
OF
directly
of
oxide
in
by a factor
disagreement
ALLOYING
influence
The
ELEMENTS.
6
and
W
by
addition
adsorption
of
to
the
an
alloying
liquid/solid
element
to
interface
the
or
metal
to
the
1868
JOURNAL
PHYSIQUE
DE
N°
III
lo
liquid/vapor surface, leading respectively to a decrease of «~~ and «~v.
Interfacial
adsorption
adhesion
Surface
adsorption,
improves
both
and
the
hand,
wetting.
other
always
on
deteriorates
adhesion
and only improves
wetting if 6 is originally below 90°. These
effects
been
by Li et al. [12], using the
classical
approximation of a monolayer
have
modelled
surface.
The
leads
following expressions of the energies of adsorption of a
model
the
to
wluteB
the
from
liquid
bulk
matrix
S/L
M
at
+
(W~
W~
«/(
flhi
L/V
and
(noted
interfaces
E~~
and
E~v respectively)
Es~
E~v
=
(«/v
ELV
fl~
(5)
(6)
mA
=
the
exchange
of the
M-B
solution
modelled
regular
solution,
energy
as
a
V(~ and m a structural
occupied by a monolayer of one mole of M atoms (Q~j
reduction
of
parameter roughly equal to I/4 for liquid metals. A negative value of E
a
means
the
corresponding
value of « while a positive value of E
negligible effect of the solute
means
a
where
Q~
B
is
A
the
on
area
=
«.
example
An
10~
m~lmole)
Sn
(«~v
2.2
=
the
as
of
Q15.5
x
=
of Al
Al
present
at
partial
and
again.
value
a
tension
solute
alumina
These
of
is
in
most
pressures
Sn
between
in Al~
the
mJ/m~)
955
6 in
the
systemj
processes
low as
as
well
agree
intermediate
the
'°
10~
Pa
with
role Of
it
as
a
decreases
it is
as
less
experimental
the
compo~ition
becau~e
and
and,
of Al
Consequently,
affected.
not
tension
to
of Sn
ten~ion
alumina
and
surface
predictions
metal/ceramic
In all
is
have
Sn is the
minimum
OXYGEN.
metals
20kJ/mole,
alloys (A
815 mJ/m~~ W
(«~~.
negligible effect on the surface
Al-Sn
in
interfacial
in
When
decreases
a
element
many
mJ/m~ j
between
angle
showing
OF
this
in H.
tension
contact
INFLUENCE
properties
2~0
decrease
decrease
found
Addition~
=
W
significant
a
(Fig. 2)
interest
K.
=
90°,
results
is
?73
at
mJ/m~,
consequence~
a
interfacial
but the
than
approach
alumina
485
induce
but
this
of
on
range
[1?].
Oxygen is Of particular
surface
influences
the
[13]. The
interaction
of
liquid
Sn-Al
T=1213K
I
F(g.
Sn,
2.
Contact
decrea,e,
decrea,e,,
angle
ic,i.>ii>
but
angle
becJu,e
the
coin~lo,itiort
of Sn-Al alloy, on
,apphire
,olid/liquid
irtterfJcial
energy
(r,~
liquid/vapor ,urface
energy (rj v i,
minimum.
through a
pa,,e,
i,otherm
the
becau,e
;tt
T
decreJ,e,.
dccrea,ed.
K
(12(.
When
Sn
273
A,
a
re,u[t.
When
ii
Al
added
the
curve
added
i,
to
Al.
ot
~Jl,o
contact
lo
N°
lo
WETTABILITY
with
metals
low
results
oxygen
temperatures,
Dissolution
of
in the
formation
single
a
or
REACTIVITY
AND
of
oxides,
either
phase
metallic
METAL-OXIDE
IN
containing
tendency
a
oxygen.
liquid metals
increases
the wettability of oxides by
oxygen
concentration
be as
low
few
ppm[14]
(see Fig.
may
as
a
phenomenon,
[3] proposed that oxygen in solution in the metal
Naidich
the
form
to
metal
the
to
oxygen
(Fig. 4). It has recently
adding to the metal M
dissolved
order
first
as
be
a
The
oxygen.
partially
a
These
atoms.
and,
ceramics
covalent
having
clusters
interaction
yoj~~
and
yo
and
Xa
where
interaction
the
and
B
Si
clusters
strong
B
in
angles,
which
effect
are
solutes
the
cases,
needed
are
and
in
can
contact
some
cases
this
~( XB
of
of B in M.
O,
and
non-reactive
favourable
most
B
+
coefficients
fraction
molar
yojmj
=
activity
the
are
the
In
y~
associates
is
of
Et
that
iono-
«
interfaces
be
F( being
0,
by
enhanced
interactions
with
Wagner's
oxygen
The
~~~
+'
more
greater is the
found in O and Cr
the
in pure M and in the M-B alloy,
highly negative Et is, the stronger
interfacial
activity of a cluster of O
clusters in Cu/AI~O~ [15]~ or O and
improve wetting on
iono-covalent
oxide, but even in
60°. In principle,
angles remain
above
lower
contact
(e.g. in the joining of ceramics by brazing alloys)~ can
using a reactive
B.
However,
central
question is how
solute
the
model of general
being available relating wettability to reactivity.
acceptance
sections~
reviewed
in order
experimental
of
reactive
wetting will be
results
governing thermodynamic and physico-chemical
parameters.
expected
be
from
with
metal/oxide
can
metal
transfer
interactions
oxygen
solute-solute
this
with
charge
in
the
explain
To
by
defined
parameter,
results
develop
coulombian
adsorb
strongly at the
capable of developing
thermodynamic
requirement for
solute
at
though
even
3).
can
effect
Examples of this
Au/AI~O~ [16].
atoms.
which
beneficial
between
conclusion,
In
the
is
clusters
consequence,
[15] that the
a
shown
in
respectively,
character,
ionic
predominates
which
dissolved
oxygen
atoms
1869
SYSTEMS
B,
select
to
no
following
identify the
the
In
to
(degree)
135
130
i~5Q0c
~~~
e.(~
~$i~~~~
1100°C
~
ffleta(
~~
120
BULK
METAL
~
its
adsorption
no
,05
%~j
+
loo
~~
~~
~~
~~
~
oi~(o~
~~
Fig.
Fig.
3,
Fig.
of
JOURNAL
the
~tmi~
surface
angle
60°
is
with
the
oxygen
partial
to
the
c-axis.
From
clu,ter,
at
a
METAL
88~8°
~
Fig.
oxygen-metal
of
~
3.
contact
sapphire
Ad;orption
4.
Naidich
of the
Variation
orientation
~
pre,,ure
for
the
~ ~~~~
4.
Cu/,apphire
The
,y,tem.
[14].
metal/oxide
interface
according
to
the
model
(3).
DE
PHYSIQUE
iii
T
4
N'
lo
ncT(JBER
1994
b>
of'
1870
JOURNAL
Wetting
3.
in
EXPERIMENTAL
3,1
generally
the
on
used
to
reaction
the
approximate
change AG(
of
~~
~~~
~
criterion
~~
(M
with
M
~
Alio~
+
reactivity at the
negative, that
notations~
the
reaction
will
we
of
formation
oxide,
MO
a
is
focu~
now
(Al ).
+
interface
that
is
(8)
the
Gibbs
standard
free
energy
is
standard
~t~e
~~~
MO
~
is
~~~~~
lo
type
for
reaction
this
metal
a
simplify
to
Oxido-reduction
the
systems,
Order
In
by
alumina
of
of
~
An
metal/Oxide
pure
reactivity [3, 17].
reduction
the
a
N°
III
systems.
in
RESULTS.
discuss
to
of
case
according
metal/oxide
reactive
PHYSIQUE
DE
Glbbs
~~~~
~~
~~~~~~~~
~~~~~~~~~
~~
and
the
~~
~~~
A[O~.
However,
into
this
(8)),
(reaction
does
criterion
Therefore~
account.
a
which
a
liquid M~ coming
from
the
final
(that
is
X~j
initial
and
l~
the
described
in
«
interactions
criterion
be
obtained
can
~~,
take
not
better
dissolution
in
zero
equilibrium X~j
the Appendix)
by calculating
of AI~O~. a~~ is
AG(
~~'
AH(jj~
where
will
see
consists
in
is the
in
a
reduction
simple
only
but
system,
AGiIRT is
dissolution
Thus~
reaction.
given
at
calculated
the
of
or
of
oxide
the
term
a
Al
are
specified
in
oxides~
needed
Concerning
Naidich
the
caption
for
the
by
Experimental
calculated
the
Pi(.j~j
Miedema
[18]~
of
be
not
scale
reported
figure
5.
data (M'
[22] are
angles 6
of
in
between
the
In
detailed
case
calculation
is
~~~~
dilution
in M.
lie
between
is
systems
data
of the
Note
that,
(10)),
metallic
different
for
experimental
which
for
000 K and 2 200
for
which
respectively come
concerning
results
(3].
review
his
reactivity
systems,
standard
the
XAj.
RT
relative
of
of the
being
difference
as
we
quantity AG(/RT, the real reactivity
oxidoin the liquid metal
and not in an
used to quantify the real reactivity for a
AG((Eq.
Data
calculation
(the
follows
of Al in
concentration
Al,
of
infinite
metal/oxide
pure
also
the
as
at
angle are available. Working temperatures
contact
non-reactive'systems
M/Alio~ and M/Sioj,
that
calculated
by equation (10) are of the order of 10~ ~,
Sangiorgi et al. [10]. Most
of Chatain
et al. [8] and
from
equilibrium
equal to
thus
M
reaction
of the
of
taken
the
matrix
interfacial
AGf
substrate
will
rough
different
for
progress
the
~~~~
mixing of
high values
AG(/RT
establish
to
written
Al
of
fraction
RT
moderate
dissolved
AH(jj~~
+
~~~
partial enthalpy
3.3,
section
(8) is
the
of
mole
case)
our
reaction
for
between
degree
the
is
For
Gibbs
are
species
the
free
provided
of
the
K.
systems.
values
For
the
X~jj~~ or Xs~j~j
compilations
from
reactive
others~
systems
references
are
energies of formation of
references
[19-21].
by
oxide
substrate)~
values
used.
in figure 5 as a
of the
function
parameter
We
observe
increase
couples.
that
of
an
is
correlated
with an
Moreover,
values
of AG(/RT~ 6 tends
at high
140°~ a value typical of noble
metals
alumina
and
towards
61
(e.g. Au and Ag) on
a limit~
when
AG(/RT
steeply and perfect wetting can be
In the
decreases
silica.
0~
way,
same
Ti,
Zr/MgO). A similar
correlation
reactivity and wettability has
between
reached
(ex.
observed
by Naidich [3] and by Nicholas [17] using the function AG(.
already been
AGf/RT
AGf/RT
for
contact
a
number
of
are
represented
metal/oxide
pure
increase
of o.
-
N°
WETTABILITY
lo
REACTIVITY
AND
METAL-OXIDE
IN
1871
SYSTEMS
o(o)
140
.SnMgO
.Cufmgo
~
120
~~. ~~
CofA1203
~~ flfljSiO2
°°~~~~~~~afA1203
G~fS[°2 . fufT1203
°
e
.
°
SbfSi02
~
AUfTt2°3
SbfAl203
~
.CrfTl102
AufTio
A
cuiTio
,
~(~~~~A1203
.
NIfCOO
[~~l
°
CufFe304
.
j~q
~
.Sn/Fe304
~~
.VfBeO
SUfNiO
j8j
o
80
60
~gfs'°2
°p~~f~/~~~
oPbfA1203
CrfBeo
.FefCr2°3
j"~~°~
~
AgfAl2°3
°
.
$efAl2$i~~~~~~
loo
aAufSi02
.PbfBeo
~
FefSi02~
oAUfAl2°3
CufA1203
A
[44]
o
[45]
13i
.
.
[17]
.
20
j46]
,
Tifmgo
zrmgo
-20
sn/coo
-10
Fig.
0
10
Experimental
right to
5.-
from
increa,e;
However~
the
20
30
angle~
contact
40
AGIIRT
ie/.>.n>
60
50
AG(
70
90
80
100
/ RT
for
M/oxide
pure
The
sy;tem~.
reactivity
left.
correlation
figure
couples.
of
(AGiIRT,
5
presents
lndeed~
limitations~
some
as
can
be
seen
from
the
great
highly reactive systems~
such
Al/SiO~
for
which
intense
reaction
is
experimentally,
ob;erved
well
for
as
an
as
as
systems with a negligible reactivity~ for example Al/AI~O~ and SilAl~o~. In all cases~ the work
of
adhesion
of 900-1
W has a typical
000 mJ/m2.
Likewise,
for AGiIRT
value
25,
contact
angles lie
80°
Cu/TiO (W =1600mJ/m~)
and
between
for
=140°
for
Sn/MgO
(W
150 mJ/m~l. In the
of the;e
non-reactive
couples, W varies by one order of
two
case
magnitude.
The;e
of any simple
relation
reactivity and
the
ab;ence
between
comment;
on
wettability are also valid for other kinds of ceramics. A typical example is the reactive
system
Al-Silsic
55° at
1373 K) than
the
Al/SiC,
characterized
by the same
angle (H
contact
for
which
reactivity (AI~C~ precipitate~ at the interface) has been suppressed by
system,
presaturation of Al in Si (23].
Any model of reactive wetting should explain both the general tendency of improvement of
wetting with reactivity and the strong
of results
around the H-AGiIRT
In the next
scatter
curve.
section~ we will briefly present the
different
wetting.
attempts of interpretation of reactive
of
~catter
the
=
80°
is
obtained
for
=
=
=
=
3.2
ATTEMPTS
capable
transfer
in
a
OF
reviewed
progress,
of
at
THEORETICAL
by
Laurent
DESCRIPTION
[231,
there
is at
OF
the
REACTIVE
present
describing satisfactorily
reactive
wetting~ that
solid/liquid
According to Laurent,
interface.
system is given by
the
reactive
time
co~
H~~~~~
=
cos
is
the
Am
AG~
«Lv
«Lv
Hjj
WETTING.
no
theory
wetting
smallest
Despite
some
general acceptance
followed
by material
angle possible
contact
of
1872
JOURNAL
PHYSIQUE
DE
III
lo
N°
substrate
in the
reaction.
angle of the liquid on the
absence
of any
interfacial
interracial
in
energies
about
by
the
the change
brought
a«~
account
of the
released by the
material
reaction.
reaction
AG~ is the change in free energy
per unit
area,
immediate
interface
[24].
contained
in the «
vicinity of the
metal/~ub;trate
different
interpretation; of reactive
wetting exi;t, based (I) on the a~;umption that the
Two
contribution
related
predominant
is the Gibbs free
term ~G~ [3, ?4, 2~], I-e- a
parameter
energy
that the
predominant
with the
interfacial
reaction~,
and iii) on the as~umption
inter.;ity of
is the
interface
related
with the
detailed
contribution
A«~ [26-28 ], I.e, a parameter
tern
energy
c.hemi,itiy and
interfacial
reaction
of
products.
,itiuc.tm.cJ
where
Hjj is the
into
takes
contact
»
reactive
wetting was fir~t
Mr)del,i
ha.;ed
This
contribution
3.2.I
the AG~
to
term.
r)fi
considered
reaction
between
that the
the
proposed by Aksay et ul. (24] and by Naidich [3 who
liquid and a fresh,
periphery of the drop increases the driving
unreacted,
~olid
;urface
at the
force for wetting. Aksay et ul. argued that,
becau~e
interfacial
reaction is
maximum
the rate of
first
instants
the
liquid and the solid, the effect of the
the
of
between
at
contact
very
interface
Thereafter,
the
become~
during these early instants of contact.
AG~ term is strongest
is
Consequently,
in
reaction
products and the overall
controlled
by diffusion.
saturated
reaction
kinetics
the
slow
down
and
gradually approach
reaction
and the
angle would
contact
increase
the equilibrium
value (Fig. 6). Note that, in practice~
be
difficult
;uch a dewetting
would
to
ob~erve
triple
line
a;peritie~
created
by
reaction
itself
the
be
blocked by
(roughne~s)
the
as
can
of wetting.
in the
course
a)
~
60
~°
Arcos
~
°LV
~
~~
~~~
Ar
cos
°LV
b)
'
/
/
fi~
~°
'
,
',
~
~~
6min
~
~
Fig.
6.
of
reaction
a
time
at
Schematic
a
product
con;tant
of
representation
P
according
temperature.
to
b)
the
the
model
~~
~~~
~
$
reactive
of
Corre,ponding
wetting
Ak,ay
contact
et
of
a
M
metal
[241. a)
itngle~ in
al.
on
a
Variation
a
,e,,ile
Slid
S
of the
drop
with
the
contact
experiment.
formation
angle
with
N°
10
WETTABILITY
major
However,
conditions
A;
consequence,
a
vicinity
been
have
of
De;pite
reactive
other
in
by
of
the
with
the
aG~
po;sible
of
the
wetting
reaction
coupling
the
unknown.
are
in
zone
«
the
differing by a factor 10
only provide order of magnitude
choice;
and
calculation~
of
1873
Indeed,
term.
kinetic;
thickne~,
the
not
;uch
can
performed
calculations
of AG~ as~uming
that
the
li~uid-;ide of the interface, the
monolayers,
at the
one
equilibrium in thi; region is reached rapidly,
chemical
(3(
Naidich
of
two
Supposing
;olid-side.
e;timated
of
still
is
»
Clearly,
consists
reaction
calculation
SYSTEMS
METAL-OXIDE
IN
calculation
the
interfacial
interface
the
interface
the
at
of
[3. 24, 25].
AG~.
difficultie;~
the;e
»
AG~ is
lie
made
e,timates
«
difficulties
time-dependent
rigorous
a
of the
immediate
REACTIVITY
AND
that
:
AG,
~~~ AG~
=
(12)
da
o
where
and
a
a~~
AGR the
and
respectively
are
free
Gibbs
AG~ for ;ome
Zr/C,
Silc.. ) and
experimental
the
contribution
of
on
However~
difference,
Cu/TiO),
nor,
example
(H
=
the
on
reactivity
different
but
al;o
the
Sn/NiO,
of W
value;
concluded
ifitefi.;e
an
fact
that
Al/Sioi
example
the
on
reactivity
great
a
been
that
area.
of
U;ing
Tilmgo
agree,
of the
progress
model~
thi;
reaction
Naidich
Zr/M go (but
and
within
factor
a
3G~
the
predominant
represents
required to obtain a good wetting
provides an explicit
A<r~ term~ thi; model
that
lea<.tiofi
i~
(a
wettability I;
SilAl~o~).
similar
reaction
,y~tem
zone
(3 Ii,
of
in
which
in
;everal
from
~i,ettability
hundred;
with
~y,tems
Moreover,
and
Fe/SiC
alw
with
two,
neglecting the
reactivity (Eqs. (I I) and (12)j,
relation
which
;eems
of figure 5.
energetical model, it I; not po~~ible to explain neither
AG(/RT value (for example
Sn/MgO
between
same
a
contrary,
results
calculated
degrees
unit
per
like
Thus,
and
for
(for
from
de;pite
70°
systems
and
[?9, 30].
ob;erved
reactive
has
It
wettability
of
reaction
the
empirical
correlation
u;ing such a purely
the
the
that
wetting
wlid
a
between
confirm
[3].
ones
reactive
to
I%uid
a
relation
found
equilibrium
and
current
of
M/oxide
calculated
Tilc.
the
energy
of
the
and
very
Al/Sioi
the
I;
a
to
rather
micron,
I;
poor
formed
reaction
I; not
a.>ii/jiciefit
that the
of an
inten,e
appears
occurrence
Thi;
condition
neither
good
wettability,
I-e91)°.
I,
to
«
ii<,<.c,.,.>aiv,
i,
J
combination;
clearly ,hown by re;ult, given in table II for,o>ne
nietal/iiietal
metal/ceramic
or
without
;ignificant reactivity (for example, in the ca;e of the metallic
;y,tem; given in thi;
any
table,
;olubility of Fe in liquid Pb and Ag is le;s than 100 ppm). In the,e example,, the good
wetting observed is due to the
establishment
chemical
bond; at the
of,trong
interface
between
the metal
;ubstrate
and the
metallic
bond, of
covalent
type (for example in Pb/Fe) or
type ((or
in
a
minute;)~
few
condition
in;tance
Table
I£>a<
Silsicl.
in
-Ei£ma>/£>.i
II.
<>/,qoa£/ it'£>ttinq
a/>t£nil£>£/
lot- h£yin£11.iah£/
ti.ith
.iv.,t£>fir.,
a
ii£>qhqi/>le
iii-iii-.
3??
Mo<le/.I
AG,
Arr,
two
it
obtain
and
terms
was
T @C)
Liquid
Solid
1273
Pb
u-Fe
32
1240
Ag
u-Fe
40
[39]
[40]
8
Reference
°
1690
Si
SiC
34
3~41
1100
AI
TiN
45
42
ba.iec/
term.,~
(>ii
t~vo
A«~
trio
series
succe~sively
of
kept
In
term.
experiment;
con;tant.
In
appreciate the
to
carried out,
recently
were
the iir~t ~erie,~
the wetting
order
importance
relative
in
oi
which
a
each
CuPd-Ti
oi
oi these
alloy oi
1874
JOURNAL
composition
fixed
stability
the
to
Tijoi layer,
studied
mullite
from
differed
discriminant
chemistry
Adding Ti
at
occurs
to
(Ti~oi)
a
oxide
inverse
value
of
on
the
Gibbs
alumina
of
orders
two
(Tab. III). In another
interfacial
change of
of the
metal/ceramic
reaction.
series
of wetting
transitions
is
the
same
obtained~
been
free
oxides leading
thickness
of the
by the
magnitude. Despite this
energy
substrates~
a
all
with
reacts
evidenced
nearly
is
10
thermodynamic
different
of
Ti
as
to
one
has
N°
systems,
substrates
situation
placed
Xi,
by
other
to
III
substrates
these
reactivity~
but
three
the
on
fixed
alloys
NiPd
oxide
one
wettability
experiment~ the
difference~
great
three
on
silica) [32]. In
and
product
interfacial
~ame
been
has
(aliumina,
PHYSIQUE
DE
I-e-
a
formed at the
interface
change in the type of Ti-oxide
driving
interfacial
Since
Xl
thermodynamic
force~
for
the
when X~,
the
(Fig. 7) [33].
reactions
the change AH can only be explained by a change in Arr~.
the
same,
are
NiPd-Tilc
[27]), it
experiments (on Cu-TilAljoi [26] and
studies
other
From
these
and
two
metal/ceramic
with
weak
reactivity,
moderate
least
in
concluded
that at
has been
systems
a
or
interface
contribution
welling is the term A«~~ reflecting
reactive
predominant
the
to
energy
observed
particular
at
values
with
a
=
Table
Wettabiliti'
III.
eipeiiniefit.I
£Jfi£/
ifiteif£J£.ia/
<.henii.itii'
(>l'cuPd-Ti jX~,
)/o,ride .ie.I.file di~op
0.15
=
[32].
substrate
8
product
interracial
°
alumina
34
Ti~O~
mullite
32
silica
35
Ti O~
Ti O~
(pm)
thickness
0.5
m
~
~
l
10
130
o
ldegl
~~2°3
l10
T1509
90
Ti~O~
7°
so
T
,
~o
~
30
~Ti
°.i°
o-lo
o30
X(j
Fig.
7.
Wetting
Njpd-Tilalumina
the
interlace
transition;
;ystem
at
by microprobe
T
ob,erved
523
analysis.
particular
at
K.
plateau
(33(.
Each
From
values
oi
the
correspond~
molar
to
a
fraction
particular
of Ti
Ti
for
oxide
the
reactive
identified
at
N°
WETTABILITY
10
during
change
reaction
be
the
quantities
reactivity.
reactive
of
Let
matrix
interaction
in
as
M
on
this
to
way
a
reactions
interfacial
rather
than
modify
the
substrate~
oxide
an
system
by
followed
precipitation
the
instance
for
by
described
be
can
the
Accordingly~
term.
interface.
interfacial
an
practice~
In
to
promoting
of
means
a
iii,iifii
Aljoi
possibly
AG~
metal/ceramic
transient
1875
SYSTEMS
METAL-OXIDE
IN
exploit
wetting
without
causing
reactions
massive
metal
and the
ceramic,
alloy a
non-reactive
base
controlled
metal
with
one
can
reactive
additions, leading to the optimum relation
solute
between
wettability and
consider~ at a given temperature~ a reactive
thus
solute B
in a nondissolved
us
could
between
reaction~
the
REACTIVITY
AND
2 (Al )
~
of
of
substrate.
alumina
in
The
chemical
alloy [26. 34]
the
3 (O
+
oxide
B
a
alumina
an
dissolution
the
(13)
interface,
the
at
example
for
2(B)+3(O)~B~OI.
For
small
X(
oxygen
values
of the
mole
for
reaction
II 3) (the
fractions
and Al~
of B
superscript
(14)
equilibrium
the
stands
D
mole
dissolution)
for
fraction
will
of
dissolved
given by
be
the
equation
Xi
K is
where
and
Xi
rapidly
increases
expected
(curves
D
equation (7).
O-B
strong
:
F( Wagner~s
and
by
defined
solutes
B
[34]
constant
a
(-
Kexp
=
~
F(Xs)
first-order
interaction
F(<0~
If
interactions
will
(15)
high
sufficiently
for
in
the
of
values
di~solution
alumina
promote
between
parameter
Xs~
melt~
the
O
as
Fig. 8).
in
(al
lbl
tog Xo
-2
p
,f
/
I'
P
_~
/
,
,
Al/A1203
Al/A1203
D
-6
-8
-6
-4
-2
0 -6
-4
Fig.
oi
the
a)
Curve
Only
1773
T
curve~.
fraction
mole
log X~.
X~.
Thermodynamic~
8.
K
This
of
diwolution
[47].
occur~
b) The
for
matrix
logarithmically
of
alumina
solute
Ni-Ti
at
the
in
reduces
B
T
=
the
log XB
B/Al~oi
M-solute
variation
of
melt
alumina
773 K [34~
Xo
occurs.
on
48].
j~(
~y~tem~
di~~olution
~toichiometric
from
oxygen
describes
P
of
o
-2
log XB
the
in
<
Curve
0 ).
alumina
of
in
equilibrium
Thi,
right of
is
the
the
MB
with
case
D gives
alloys as
B~OI as
of
intersection
logarithm
the
a
a
junction
of
function
of
alloys
Ni-Cr
point
of
the
at
two
1876
JOURNAL
Moreover,
sati~fying
B
solute
a
B~OI by reaction
in etjuilibrium
oxygen
oxide
with
K'Xi
precipitation
to
fraction
mole
of
X[~ i,
denoted
of
10
an
dissolved
by
given
>( X~
exp(-
~~~
lead
also
can
alloy. The
(reaction (14)),
the
precipitate
Xl
N°
III
0
>~( w
in
oxygen
excess
B,Oi
the
with
condition
the
the
PHYSIQUE
DE
(16)
=
is
K'
where
(34].
con;tant
a
it
When
X~
Xl
0,
-
higher X~
at
Xl
increases
predominates and
rapidly with
oi
and precipitation,
dissolution
the
ca;es
certain
value of X~.
If for the
of X~ the inequality
value
same
X~.
However~
for
Al~oi
Thi;
condition
being
very
Cr
in
I;
,trong
in
verified
for
(>I'
concentration
Xl
Xl
chromium
the
but
<m
alloy~
Ni-Ti
100)~
I)
increa,ed
an
it
for
not
;t,
iroiT1
oi
ad,orption
incre~i,ed
chromiuiT1
oxygen (or~ in
oi
nickel.
ca,e
decre~i,e
dissolved
verified~
is
increases
oxygen
the
solute
will
B
above
reduce
a
the
B~OI
other
I,
more
teriT1;~
the
interactions
between
oxide
alloy.
the
in
Ni
Indeed~
?5j,
A;
the
additions
only
effect
figure
in
,hown
The
aliiiiina.
~jn
solute~
titanium
and
oxygen
El'~
chromium
a
angle tli
c~jntact
(17)
).
alloy
Ni-Cr
the
di,,olved
oi
OM
'(Al
+
oi
of Cr
9~
influence
Cr
oi
eiiecl,
two
concentration
concentration
an
Indeed,
re,ult
~.ould
increa,ed
P in
(curves
of
~
decreasing function of
equation (16)
in
term
Thus,
in both
Fig. 8).
a
exponential
increa~ing X~
?(B
+
=
con,iderably
Ni
~'~, i-e- it is
the
iorm~ition
oi
up to 20 at-T> in Ni do not lead to the
oi
alumina
matrix I, to
the
di,,olution
thi,
increa,e
Jdditi~jn,
Xi
as
Bjoi
forming
alumina~
varie~
values~
w0~
clu,ter,
which
due
oxygen
be
can
to
ad;orbed
reaction,,
interf'~ici~il
at
metal/oxide
the
I-einterlace
an
;
capability oi tfie OCr cluster; a; compared with the ONi clu,ter~.
electropo,itive than nickel~ the charge tram,ier from
chromium
to
the degree oi ionicity oi OCr
would be greater
than in the
clu;ter;)
0
(dog>
120
fi
_~~,-
loo
Ni-cr
go
Ni.Ti
60
j
s
4o
~'~~
~
Fig.
Cr
Contact
9.
I,imple
ii?
773
K.
angle,
di,,olution
oi
Ni-ba;ed
oi
alumiia)
alloy,
and
on
Ni-Ti
~'~~
~'~ ~
alumina
a,
(34. 48(
a
X
~'~~
B
function
ldi,,olution
oi Cr
i
or
Ti
fraction
mole
precipitation
of
a
Ti
for
oxide)
Niat
N°
WETTABILITY
10
Note
that
for
i-t
I,e.
same,
tensioactive
the
effect
wettability
on
by
character
an
TilAljOi
of
oxide
the
is~
decrease
licjui£/-.fide
the
additions
Table
in
K
1877
I) and iii
both
effects
the
are
be
than
is
metals
oxide
eifects~
(b) formation of
explain the ~trong
into
I-e-
(a)
in
decrease
7].
[~~
very
account
nickellaluiT1ina
metallic
more
in
clearly
effect
This
metallic-like
the
;ystem~~
be
Aljoi.
Thus,
in the
Nioxide
Tijoi
increase
mu~t
adwrption of OTi clusters at
oxide
~uch as Tiioi at the
angle cau~ed by Ti
contact
semi-metallic
a
mu;t
take
like
semi-metallic
the
two
in Ni
also
Tijoi layer at the
accepted that the
Cu/oxide
non-reactive
the~e
cluster~
mu~t
one
generally
by molten
and
can
ca;e~
iono-covalent
Aljoi by
of
OTi
continuous
a
wetted
an
oi
this
(Fig. 9).
ail,ale
-Cofita<.t
IV.
4?3
T
wettable
interface
oi
concerning
lV~
table
interface
the
Ni
will
combination
of the
of
.relic/-.n£le
for
interactions~
in
Currently~ it
it
more
The
o.
formation
the
alumina.
replacement
the
system,
and
retjuireiT1ents
strong O-Ti
However~
to
interfaces.
of
reduction
in the
of
results
appears
oxide
TiO
being
more
W
due
system~
metal/oxide
at
interface
thermodynamic
the
B~
SYSTEMS
METAL-OXIDE
IN
0.
<
Ni-TilAljoi
the
In
wlute
a
REACTIVITY
AND
anti
ti.oft
(>/
Conduction
type
(>I'(.(>j>pe/.
a</tie.ii/>fi
iljff?/.efil
off
o,ride.I
at
(3(.
=
Oxide
8
insulator
influence
This
due
to
interface.
In
Cu-TilY~oi
Unlike
INTERPRETATION
be
metallic
72
1650
the
in
of
10,
Ii
curve
but
AG(/RT
OF
the
on
ON
RESULTS
contribution
curve
of
figure
alloys
Cu-Ti
on
metallic-like
of
decrea~e
Ca
Al
to
wetting
on
the
at
curve
of
[26, 30]
alumina
TiO
oxide
2j
Yjoi
formed
is
as
opposed
Cu-Ti
into
140° to 80°).
SiO~
sub~trates
or
[35]. lndeed~ the
where,
at
the
to
the
alloy~
(from
o
Aljoi
interface
has
no
effect
iono-covalent
type.
same
M%xiDE
PURE
reactive
to
of
the
perfect (Fig. 10~
where only
dissolution
limited
adding
additions~
case
Ti,
nearly
becomes
spite oi the
formation
of CaO
replaced by an oxide of the
now
predominant
distinguished
the
1460
activity
significant
of Ti
82
in
is
substrate
3.3
effect
the
wetting~
on
[30] (Fig,
a
metallic
greater
even
wetting
case,
~ystem
producing
occurs~
j4
thermodynamic
that
460
l13
of Ti is
higher
the
W
128
Ti~O~
Tioi
(°)
Based
SYSTEMS.
i~ the
Arr,
three
term~
on
kinds
conclu~ion
the
of
behaviour
that
can
5
for
M/oxide
is typically
of ?0 or
couples can be
values
more~
wettability~ as
non-reactive
0). In that case~ the
systems Ii-e- Am,
work of
adhesion
W i~
by metal/oxide
interactions
localized
interface
and for
ensured
at the
iono-covalent
be
described
given
oxides
by equation (4). The
AH
scatter
at
can
a
AG(/RT i~ e~sentially due to the variation of the bonding
of
character
the
~ubstrates,
between
insulating oxides and oxides for which
cohesion
is provided by partially
metallic
bond~.
This
explains
dispersion
=139°
the
between
for
Sn/MgO
and
=77°
Cu/TiO
o
o
for
or
1)
For
considered~
88°
6
with
for
w
0~
regard
that
to
1
Au/TiO.
=
2)
angles
For
lie
po~itive
but
low
value~
between
60°
and
100°.
AG(/RT (of
typical example
of
A
the
is
order
of 10)~
Cu/NiO
the
68°
=
corresponding
at
473
K).
From
contact
data
1878
JOURNAL
PHYSIQUE
DE
N°
III
10
1:Y~O~
2:Al~03
#
cO
i
i
-
,
u
w
#
#
j
I
i
°la)
lot
Fig, lo.
Wetting and work
Reactivity
con,I;t,
in a ;imple
precipitation of a Ti oxide at
of
table
relative
V
to
performed
at
from
diswlution
the
this
of
Cu-Ti
oi
the
interlace
the
and
system
equilibrium
lead
of
adhe,ion
di,solution
oi
NiO
to
in
melt,
oxide
the
,econd
following
the
first
the
at
423
T
ca,e,
and
in
a
from
K
(3U].
di;,olution
+
7
of
value
the
thermodynamic
[36]~
molar
fraction
of
calculations
oxygen
coming
:
xi
Xi,
=1.5
x
=
Xi
Aljoi
and
in
ca,e.
i-l'w
value
the
Yjoi
on
,ub~trate
lo~~
(Xl14 x
enough to produce
precipitation oi the
oxide
Cujo
copper
only possible effect in the Cu/NiO
is
the
adsorption
oi
dissolved
system
This
adsorption
leads
lower
much
angle
for
the
Cu/Alioi
than
to
oxygen.
contact
a
value oi Xii j68° against 100°). This
sy;tem (14] (Fig. 3) ior the
be explained by an
same
can
increased
adsorption capability oi ONi clusters with respect to OCU clu~ters~ as indicated by
the
negative value oi >I'.
Wettability in sy~tems like Sn/Feioj
~("
50 36] )~
Cu/Feioj (~(~
540 [36
or
Fe/Crjoi
10
[37]
be
in
interpreted
the
F(~
Moreover~
the positions oi the
can
same
way.
Al/Aljoi and SilAljoi
that
these couples~
considered
previously
systems in figure 5 suggest
non-reactive
systems IX ], fall into the
category~ in ~pite oi the very low solubility oi
same
a~
re;pectively.
in Al and Si
oxygen
is
10~~).
not
high
Thu~,
the
~
i
~
Table
V.
Trio/.fiia(.fiefiii<.(ll
Clara
at
1473
T
ielatii'e
K
=
to
(lie
Cu/NiO
reaction
o~j
2(Cu)
cn
l~°1
jNio)
cn(CU~O)
5
1°21 °~1°)Cu
~~~~
.iv,item.
N°
WETTABILITY
10
3)
For
and
two
the
.
cases
first
another
corresponds
case
the
of
replacement
the
to
For
type.
same
this
of
kind
bonding
of
1879
phase
new
of
oxide
by
Setting
is
iono-covalent
an
the
at
interfacial
this
improvement
involving the
important
reactivity,
no
a
character
interface
the
at
systems~
SYSTEMS
produces
reaction
Nevertheless,
interface.
layer
METAL-OXIDE
IN
AG(/RT close to zero or negative~
wettability will depend on the
be distinguished
can
of
values
REACTIVITY
AND
of
expected. Al on Sioj provides an example of intenw
reduction
of
SiO~ to form AI~O~ at the interface, and a slight liquid
enrichment
iono-covalent
in Si. As the
oxide
Sioj is replaced by an oxide of the
angle of Al on SiO~
type~ the
contact
same
80
073 K) is
lo
therefore
close to that of Al on Al~oi.
The
explanation is
at
± 5°
same
valid for the
Aljoi or Sioj systems previously mentioned~ for which Ca additions
Al-Ca
on
do not improve wetting
because
interfacial
the
product jCaO) has roughly the same bonding
~
than
character
the
.
by
the
second
a
A
one.
large quantity
a
solid
even
corresponds to the replacement at
typical example of this
situation
case
metallic
dissolve
substrate
interface
the
is
oxygen (a few at-ill O and form
of Ti with high
The
content~.
oxygen
be
explained by the
double
in.iitii
solutions
(Fig. 5) can
system
adsorption of oxygen
of
liquid-side
the
at
and
the
iono-covalent
an
Liquid
metallic-like
oxide~
a
perfect
wetting
a
oxide
titanium
;uch
observed
for
interface
metallic-bonded
phase
of
can
TiO,
as
the
modification
of
formation
of
Tilmgo [3].
this
the
the
at
solid-~ide.
ieature~
These
(Fig. 5).
Ni
or
Co
Niisn
or
explain
also
can
reduction
The
these
of
produced by thi~
Coisni
the
at
reaction
is
by liquid
obtained
possible
Sn is
than
greater
oi
temperature
wetting
excellent
the
substrates
needed
that
for
and
Sn
the
precipitate
to
NiO
on
COO
or
oi
amount
di;solved
intermetallics
the
experiment.
the
Conclusion.
4.
For
with
~y,teiT1;
be
to
appears
free
energy
term
must
localized
term
AG~.
However~
the
excluded
triple
metal/oxide
Pure
by
de~cribed
line
which
interracial
the
in
case~~
divided
be
can
AG(/RTW
at
the
In
order
element
I)
both
OB
B~
into
three
when
intense
an
last
strongly
reaction
categories
?0)~
than
and
10~
~
to
the
is
120°.
about
oi
work
effect
the
nature
oxide
of
adsorbed
efiect
This
substrate.
of
of
wetting
oi
improvement
an
the
substrate
Weak
adhesion
can
be
is
oxygen
greatly
obtained
is
at
with
interiace~
the
by
enhanced
the
precipitation of a new
iono-covalent
layer i for
metallic
compounds (metallicand
interfacial
this
case
or
to
in~tance
of this
it) behaviour
observed
will be
whereas
for
intermetallic~),
nearly perfect wetting
be expected.
can
a
oxides
l'or
Gibbs
transient
the
predominance
the
even
than
wetting
reactive
oi
parameter
rather
equation (4)
~
compounds~
and
(typically greater
sharp
interface
0
iii in system~
characterized
by AG(/RT
regard to the preceding case
80° )~ due
produced by the
dissolution
oi the
oxide
iormation
of
metal-oxygen
cluster~
iii) when AG(/RT w 0~ both
dissolution
phase
Wetting will depend on the
occur.
like
governing
change Arr,,
importance
some
localized
are
the
energy
occur~.
~ystems
for
I) in
systems
metal/oxide
bonds
reactivity,
moderate
or
reflecting
be
not
at
weak
term
the
produce
two
a
strong
conditions
have
improvement
to
be
of
wetting
of
a
non-reactive
metal
by
an
wlute
B
can
alloying
~atisiied
~( must be very negative. Then,
the
thermodynamic
parameter
liquid and solid sides of the interface~ forming at the liquid-side
cluster;
solid-side
and at the
phase1
a
new
the
an
adsorption layer
modify
rich in
1880
JOURNAL
it)
this
It is
carbide
such
only
~uch
criterion
observed
Despite
properties
is
work
is
experimentally
and
for
of
on
degrees
of
tens
concepts
copper
can
covalent
a
metallic-
on
metallicity is not
Indeed~ good wetting has
f'or liquid
silicon
(which
However~
instance
the
for
the
10
past
the
been
is
a
very
the
transient
reactive
very
description
of
systems
in
reactive
and
energetical
experimental and
couple~
for the
further
years~
and
physical
a
physico-chemical
of
non-reactive
because
and
the
in
model
theoretically
by general
considerations.
to
few
ceramics.
knowledge
our
for
systems~
mi~sing~
predicted
AG,~
force,
especially
needed~
~till
in
gained
interfaces
metal/ceramic
level
only a
[3].
it is
the~e
of
some
angle
contact
carbides
ceramics~
improvements
metal/ceramic
non-reactive
while
the
non-oxide
covalent
on
10
(Tab. II).
carbide
significant
of
of
substrates~
oxide
on
molybdenum
or
N°
III
metallic-bonded.
example~
For
wettability
metals
some
the
theoretical
atomic
good
;ilicon
on
focused
work
ceramics.
chromium
as
for
for
metal)
this
of
partially
lea~t
at
B4C is very high II 36° [3 ]),
as
carbides
like
kind;
other
to
be
must
although
that,
noted
applied
be
phase
new
PHYSIQUE
DE
contribution
interface
the
order
an
driving
wetting
the
to
at
evidence
to
Acknowledgments.
Profe~sor
A.
are
Cambridge~
MIT~
of
Mortensen
acknowledged
gratefully
for
USA~
and
reading
critical
their
J.
Dr.
of
of
Garandet
P.
Grenoble
CEN
manu~cript.
the
Appendix.
thermodynamic
The
equilibrium
condition
AG(
where
a~j
As~uming
that
the
RT In
$Aiivi being
equilibrium
partial
the
enthalpy
fraction
mole
of
Al
thi,
=
X~j.
(Henry
law).
;
rough
e;timate
av
I,
n~j
=
overe,tiiT1~ition
W~jjv
4(j~vj
oi
m~jre
oi
is
thus
I;
u;ed
reacti~ity.
W.,jj~~
and
j
reactivity
is
0
IA.
over-e;tiiT1ated.
supposed
of Al,
equal
unity.
to
given by
is
y~j~
~~'~~
AHAIIMI
=
of Al
in
M.
IA?),
and
IA,
relations
From
W,j~~
+
AG/
~~~~
normally
the
constant
in
etju~il
when
the
W(jj~~~j
=
calculation,~
our
Indeed,
an
and
)~
RT
~'
~~'~~
X,j.
on
X~j
A
M~jretlver,
valid.
iollows
as
=
RT
equation~ WAj~vj depend;
;mall
yAj
mixing
of
~~~
W~jjv
For
written
becomes
AG(
~"
In
RT In a~j
+
(8) is
reaction
thermodynamic
activity oi Al in the liquid~ a~
melt is a regular
solution,
the activity
coefficient
the
i~
for
it~
to
undere,tiiT1~ition
value
at
can
in
which
AG(.-0
replacement
oi
X~j
(A.4)
)~
infinite
dilution
con~equence
oi
only
the
X~jand
AH,,jj,i, by AH(j,~j
then
oi
AG/
for
negative
W~jj~
lead,
in
j,
Al
in
M
provide a
hypothesi,
that
to
an
c~i,e~
N°
WETTABILITY
10
REACTIVITY
AND
METAL-OXIDE
IN
1881
SYSTEMS
References
D.,
II
Chatain
[2(
Eu,tathopoulo,
[3]
(4(
[5(
[6(
(7(
(8(
Naidich
[91
(lo(
II
[12(
ii 3(
W..
P.
John;on
Hicter
(21)(
(2 Ii
[22(
(23j
(24(
(25(
[26(
(27
[28(
(29]
[30(
(31(
(32(
(33(
(34(
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M£>tlibian£>
M.../
/
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C.,
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I.,
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M£ilei.
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Mater.
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Univer,ity of Athen,~
Greece
l19911).
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Coudurier
L..
Eu,tathopoulo,
N.. M£n R£>.,
So<..I;>iij)
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