第
11
卷第
3
期
2007
年自月
工程设计学报
J
ournal
of
Engineering
Design
Vol.
14
"1
0.3
]un.
2007
Experimental
study
of
influence
on
electric
double
layer
on
aqueous
lubrication
BAI
Shao-xian
1
,
HUANG
Ping
2
,
MENG
Yong-gang
1
,
WEN
Shi-zhu
1
(1.
State Key Laboratory of Tribology , Department
of
Prccision lnstruments and Mechanology ,
Tsinghua University , Beijing 100081 , China;
2.
College
of
Mechanical Engineering, South China University
of
Technology, Guangzhou 510640, China)
Abstract
, Near interfaces of solid and liquid , electric double
lay巳
r
has electro-viscosity effects. TheoreticaI study
shows that this electro-viscosity wilI make friction coefficient increase
in
thin film lubrication. The purpose
of
this
study
is
to vcrify the influence
of
electric double layer on aqueous lubrication
in
an
expcrimentaI way. Experiments
were done on a composite sliding block
test
盯,
with distilled water
as
basic lubrican
t.
Two different methods were
adopted
in
the experiments. One
is
to add external electric
field
口 n
friction pair and
thεother
is
to change ionic con-
ccntration
in
lubricant with additivc - KCL here. Both methods can makc electro-viscosity change according to
theoreticaI research. During experiments
, friction coefficient and steaming potential were measured. Experimental
results show that electro-viscosity has significant influence on friction coefficient when film
is
thin. Friction
coeff
卜
cient increases obviously under thin film situation when external electric field
is
added or ionic concentration of
Iu
bricant
is
changed. In
additio
口,
with the increase of concentration of KCL , friction coefficient increases quickly.
Test results indicate that electro-viscosity has significant effects on aqueous lubricating performance.
Key words: electric double Iayer; electro-viscosity; friction coefficient; streaming potential
CLC
number , TH117. 2 Document code , A
Electric
double
layer
(EDL)
ís a
ubíquitous
natural
phenomena
[1
-2J.
In
the
research
of
electríc
double
layer
C3
5J
,
experiments
indicate
that
viscosi
ty
increases
obviously
in
micro-channels
such
as
capi
l!
ary.
In
lubrication
,
the
effects
of
EDL
can
be
neglected
without
error
,
because
the
thickness
of
EDL
is
relatively
thinner
compared
with
that
of
lu-
brícation
fílm.
However
,
in
thin
film
lubrication
,
where
lubrication
film
thickness
is
below
100
nm
,
the
effects
of
EDL
cannot
be
neglected.
Recently
,
electrical
sticky-effect
by
EDL
has
been
introduced
to
the
research
of
lubrication.
There
appear
some
theoretical
models
considering
the
EDL
effects
on
lubrication
i
口
some
literatures.
Prieve
and
Bike
l6J
first
introduced
effect
of
EDL
to
TFL
and
set
up
a
model
to
calculate
e1
ectro
kinetic
lif
t.
This
e1
ectro-kinetic
force
is
always
repulsive
and
acts
to
push
friction
pair
apart.
Electro
•
kinetic
Received date , 200612-10.
Article ID: l006-754X(200n03-02S3-09
Iift
may
reduce
the
e1
ution
volurne
of
particles
in
chromatographic
columns
,
inhibit
capturing
parti-
cles
from
moving
f1
uids
,
or
cause
detachment
by
losing
particles
from
solid
surfaces.
Zhang
and
Umehara
[7J
derived
the
modified
Reynolds'
equa-
tion
with
consideration
of
ED
L.
In
their
papers
,
the
effect
of
zeta
potential
in
EDL
on
water
lubri-
cation
of
ceramics
was
theoretically
analyzed
with
a
modified
Reynolds'
equation.
These
papers
indi-
cate
that
when
friction
coefficient
decreases
with
the
increase
of
zeta
potential
,
the
minimum
film
thickness
increases.
Recently
,
theoretical
study
by
Huang
and
his
co
l!eagues[S-12J
developed
a
mathe
matical
model
of
EDL
electro-viscosity
and
discov
ered
significant
e1
ectro-viscous
effects
on
thin
film
lubrication.
Meng
and
his
colleagues[13
叫
have
car
ried
out
study
o~
the
influence
of
extern
且
I
voltages
on
lubrication
behavior
of
aqueous
solution
in
an
Foundation item: N ational
Scienc
巳
Foundation
of China (50375052); National Science Foundation for Post-doctoral Scientists
。
f
ChinR
(2005037336).
Biography
,
RAI
Shao-xian
(l
976-)
, male , Ph.
D.
, research area: thin
film
lubrication theory , E-mail: bshaoxian@163.ne
t.