Journal
of
Alloys
and
Compounds
524 (2012) 59–
62
Contents
lists
available
at
SciVerse
ScienceDirect
Journal
of
Alloys
and
Compounds
jou
rn
al
h
om
epage:
www.elsevier.com/locate/jallcom
Letter
Oxidized
electroplating
zinc-covered
carbon
fibers
as
microwave
absorption
materials
Jun
Zeng
a,b,∗
,
Huiqing
Fan
a
,
Yangli
Wang
b
,
Shiquan
Zhang
b
,
Jun
Xue
b
,
Chenjun
Zhang
b
a
State
Key
Laboratory
of
Solidification
Processing,
School
of
Materials
Science
and
Engineering,
Northwestern
Polytechnical
University,
Xi’an
710072,
PR
China
b
Department
of
Physics,
Engineering
University
of
CAPF,
Xi’an
710086,
PR
China
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
3
November
2011
Received
in
revised
form
7
February
2012
Accepted
8
February
2012
Available online xxx
Keywords:
Annealing
Electroplating
Scanning
electron
microscopy
(SEM)
Nanostructures
Oxides
Microwave
absorption
a
b
s
t
r
a
c
t
Zinc
oxide
nanosheet/zinc-covered
carbon
fiber
composites
(ZNSZCFs)
were
synthesized
by
annealing
the
zinc-covered
carbon
fibers
with
electroplating
in
air.
The
diameter
of
the
ZNSZCFs
was
about
25
m.
The
strongest
RL
of
ZNSZCFs
was
−32.98
dB
at
3.31
GHz.
The
strong
absorption
of
ZNSZCFs
was
less
than
−4
dB
(>65%)
over
the
range
of
7.54–18
GHz
(1.6
mm
in
thickness)
and
5.96–18
GHz
(2.0
mm
in
thickness),
respectively.
The
ZNSZCFs
are
believed
to
be
ideal
microwave
absorbing
materials.
© 2012 Elsevier B.V. All rights reserved.
1.
Introduction
The
electromagnetic
wave
in
gigahertz
range
is
being
widely
used
in
industrial,
commercial
and
military
fields,
which
results
in
many
electromagnetic
interference
(EMI)
problems.
In
order
to
properly
solve
the
EMI
problems,
the
microwave
absorbing
materials
have
been
extensively
investigated.
In
particular,
the
nanostructure
materials
and
carbon
fiber
composites
have
received
steady
growing
interest
as
microwave
radiation
absorbing
and
shielding
materials
in
the
high-frequency
range
due
to
their
fas-
cinating
properties
[1–4].
Additionally,
considerable
theoretical
and
experimental
investigations
have
been
focused
on
the
effec-
tive
microwave
absorption
materials
[5,6].
Zhang
et
al.
[7]
indicate
that
the
complex
permittivity
ε
r
=
ε
−
jε
,
the
complex
perme-
ability
r
=
−
j
,
electromagnetic
impedance
match,
and
the
microstructure
of
the
absorber
determine
the
microwave
absorp-
tion
properties.
Zinc
oxide
(ZnO),
a
wide
band-gap
(3.37
eV)
semiconductor
at
room
temperature
and
large
exciton
binding
energy
(60
meV)
[8],
is
a
potentially
commercial
material.
Therefore,
the
preparation,
characterization
and
application
of
ZnO
nanostructures
(ZNs)
are
extensively
investigated
[9–16].
Recently,
Chen
et
al.
[17]
reported
∗
Corresponding
author
at:
Department
of
Physics,
Engineering
University
of
CAPF,
Xi’an
710086,
PR
China.
Tel.:
+86
29
84563510;
fax:
+86
29
84563510.
E-mail
address:
zengjun2006@gmail.com
(J.
Zeng).
that
EM
wave
absorption
composites,
consisting
of
foam
glass,
zinc
and
zinc
oxide,
were
prepared
by
sintering
mixture
of
foam
glass
raw
material
and
zinc
powder.
The
results
showed
that
zinc-
containing
foam
glass
absorbed
efficiently
microwaves.
Li
et
al.
[18]
and
Liu
et
al.
[19]
reported
that
the
carbon
nanotubes/tetrapod
– and
whisker
– shaped
ZnO
nanstructure
composites
had
excel-
lent
absorbing
properties,
respectively.
Additonally,
Cao
et
al.
[20]
reported
the
effects
of
temperature
and
frequency
on
the
dielectric
properties,
electromagnetic
interference
shielding
and
microwave-
absorption
of
short
carbon
fiber/silica
composites.
Results
indicated
that
the
composite
had
good
electromagnetic
interference
shield-
ing
property.
However,
the
coating
thickness
and
densities
of
these
microwave
absorbing
materials
were
usually
quite
high
that
restricted
their
applications
in
low
density
field
such
as
aerospace.
Therefore,
it
was
essential
to
research
excellent
microwave
absorb-
ing
materials
with
wide
frequency
range,
strong
absorption,
and
low
density.
In
this
work,
we
try
to
synthesize
zinc
oxide/zinc-carbon
fiber
composites
(ZNSZCFs)
by
annealing
Zn/CF
composites,
which
are
expected
to
exhibit
excellent
microwave
absorption
properties.
2.
Experimental
details
The
carbon
fibers
used
in
this
study
were
PAN-based
carbon
fiber
(3
K)
and
produced
by
Lan
Zhou
Activated
Carbon
Industries
of
China.
The
Zn/CF
composites
were
prepared
by
electroplating
process.
Fig.
1
shows
the
FESEM
images
of
carbon
fiber
and
Zn/CF
composites.
The
carbon
fibers
were
cut
to
80–100
mm
in
length
before
the
surface
treatment.
The
electroplating
process
was
achieved
at
the
room
temperature.
The
zinc
bath
conditions
are
listed
in
Table
1.
The
electroplating
time
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matter ©
2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.jallcom.2012.02.068