J. Am. Ceram. Soc., 88 [9] 2659–2661 (2005)
DOI: 10.1111/j.1551-2916.2005.00493.x
r 2005 The American Ceramic Society
ournal
J
Al2O3/Ni Laminar Ceramics Shaped by Tape Casting
and Electroless Plating
Kai Hui Zuo, Dong Liang Jiang,w and Qing Ling Lin
The State Key Laboratory of High Performance Ceramics and Superfine Structure, Shanghai Institute of Ceramics,
Chinese Academy of Sciences, Shanghai 200050, China
Tape casting and electroless plating were used to fabricate
Al2O3/Ni laminar ceramic composites with close control of
the thickness of the Al2O3 and Ni layers. Ninety-seven percent
relative density, macrodefect-free composites were obtained by
spark plasma sintering. In electroless plating solutions, the sta-
ble potential of grain boundary led to the first deposition of
nickel on the grain boundary of Al2O3. Scanning electron mi-
croscopy, energy-dispersive X-ray, and X-ray diffraction were
used to analyze the structure, elements distribution, and phase
composition of the Al2O3/Ni laminar composites.
tion are about 51C and 801C, respectively. The formula of Ni
electroless plating is as follows:
2þ
½Ni complexꢀ þ H2POꢁ2 þ H2O ! HPO32ꢁ þ Hþ
(1)
þ Ni þ H2 þ complex
where [Ni complex]21 is the citric acid complex of Ni21. To in-
vestigate the relationship between plating time and the thickness
of Ni deposits on Al2O3 substrates, the following experimental
procedure was used. Twenty Al2O3 sheets were placed in 20
separate electroless solutions with equal initiative reactants. All
the solutions were heated at the same time, and then the Al2O3
sheet with the Ni deposition was taken out at regular intervals.
The layer deposits were left in a vacuum drying chamber for 5 h.
The nickel layers in the laminar materials were formed at an
electroless plating time of 15 h on both surfaces of Al2O3-sin-
tered sheets. Twenty Al2O3-sintered sheets with Ni deposition
were stacked together, and there were two pieces of Al2O3-sin-
tered sheets without nickel layers stacked on the top and bot-
tom, respectively. Then, the composition was sintered by SPS at
14001C and 30 MPa for 4 min.
Microstructure characterization was performed by scanning
electron microscopy (SEM) (JSM-6700F, JEOL, Akishima,
Japan). An energy-dispersive X-ray (EPMA-8705QH2, Shi-
mazu, Tokyo, Japan) spectrum across the interfacial layer was
taken to determine the diffusion of elements from adjacent lay-
ers. The crystal structure was measured by X-ray diffraction
(XRD, Rigaku D/max 2550V X, CuKa, Akishima, Japan).
I. Introduction
AMINATED composites are recieving more and more atten-
tion in the ceramic field from the biomimetic point of view.
L
Thick layers of laminar ceramic composites are usually pre-
pared by tape casting,1,2 slip casting,3 centrifugal casting,4 and
self-propagating high-temperature synthesis.5 Thinner layers
can be realized by screen printing,6 electrophoresis deposi-
tion,7–9 tape casting,2 plasma spraying,10 electroless plating, etc.
Electroless plating is a simple and inexpensive method for
depositing metals. It has been used to fabricate coatings and thin
metal films,11 widely used in fields, such as electronic and com-
puter technologies. In addition, electroless plating is a valuable
method for producing thin layers of laminar materials.
We tried using electroless plating and tape casting to produce
nickel thin layer and Al2O3 thick layer, respectively. The above
two methods can well control the thickness of layers. Mean-
while, Al2O3/Ni laminar materials were obtained by the fast
spark plasma sintering (SPS) technology.
III. Results and Discussion
Figure 1 shows the SEM micrograph of a 3.88 g/cm3 dense
pressureless sintered Al2O3 tape casting sheet (a) and an Al2O3
sheet coated with nickel for a deposition time of 1 min (b), 10 min
(c), and 7 h (d), respectively. Ni grains on the grain boundaries
of Al2O3 are more compact than those on the surfaces of Al2O3
grains (Fig. 1(b)). Ni grains firstly deposit on Al2O3 grain, and
then gradually form an Ni-coated film (Fig. 1(c)). The third
micrograph (c) shows the alumina buried under a thin film of
electroless Ni. The grain size of the electroless film is mostly
likely of the order of the initial electroless particles, that is to say,
the new Ni nucleates on the boundaries of prior electroless Ni
particles deposited on the Al2O3 grains. The stable potential of
grain boundary is more negative than the surface of the grain,
which causes the first deposition of nickel on the grain bound-
ary. Figure 1(d) shows the thick electroless Ni layer with signif-
icant cracks. The Ni layer fragments into irregular polygons of
about 2–3 mm size, and within each fragment, the film structure
is dense and free of pinholes. The reason for fragmentation is the
non-uniform distribution of heat energy between the inner and
outer layer when the film is drying.
II. Experimental Procedure
Al2O3 green tapes were prepared by aqueous tape casting keep-
ing in mind environmental and health considerations. The com-
position of the high solid (56.4 wt%) alumina tape casting slurry
is given in Table I. Tape casting was performed on Procast Pre-
cision Tape Casting Equipment (Division of the International
Inc., Ringoes, NJ) with a blade height of 500 mm. Drying and
binder removal were conducted at room temperature in air and
at 8001C for 2 h in a muffle furnace, respectively. The Al2O3
sheet (thickness B0.3 mm) was sintered at 16501C for 1 h in a
muffle furnace.
The composition of the nickel electroless plating solution is
shown in Table II. The pH value and temperature of the solu-
W. M. Mullins—contributing editor
Manuscript No. 20120. Received February 22, 2005; approved March 21, 2005.
This work is supported by the Science and Technology Committee of Shanghai Mu-
nicipal under the contract no. 02DJ14065 and by Chinese Academy of Science under the
contract no. ICGCX2-SW-602-3.
The relationship between plating time and thickness of Ni
deposits on Al2O3 substrate is shown in Fig. 2 (original and
smoothing curves). The deposition thickness is calculated by the
wAuthor to whom correspondence should be addressed. e-mail: dljiang@sunm.
shcnc.ac.cn
2659
Zuo, Kai Hui
