1. Compaction: General
Pressing operation
1. Filling the mold or die with powder
- free-flowing spherical granulated powder prepared by spray drying
are generally used to optimize the die filling
- typical granules ( range: ~44 to 400 µm, avg. ~100 to 200 µm)
- typical granule density : 45-55%
- typical die fill density before pressing: 25-35%
2. Compacting the powder to a specific size and shape
- consolidation by granule rearrangement
- granule deformation
- increase in particle-coordination number, green density, and compact
strength
- typical compaction pressure : 35- 104 MPa
3. Ejecting the compact from die
- elastic springback (the expansion of a compact upon ejection from the
die should be minimized.
S. J. Glass and K. G. Ewsuk, MRS Bulletin, Dec., 24 (1997)
Advanced Electronic Ceramics I (2004)
Spray drying
Spray drying : the process that granulates the fine primary particles into
spherical secondary spheres in order to increase the flowability of the
powder via the spray of the mixture between powder, additive, and
solvent
The additive for spray drying
1. Binder : strength
2. Plasticizer : deformable granule
3. Lubricant : reduce the frictional effect
S. J. Glass and K. G. Ewsuk, MRS Bulletin, Dec., 24 (1997)
Advanced Electronic Ceramics I (2004)

2. Possible problems in compaction
End capping
- body with poor green strength and high springback
- High die-wall friction and high pressing pressure
Ring capping
- poor tolerances between the punch and die body
- excessive differential springback
Lamination
- poor green strength
- pressing at excessively high pressures
- high springback or die fraction
Vertical cracks
- excessive springback
S. J. Glass and K. G. Ewsuk, MRS Bulletin, Dec., 24 (1997)
Advanced Electronic Ceramics I (2004)
Consideration of Die
Narrower diameter die usually results lower packing density
because the packing density at the die wall is lower than that at the
bulk of the compact.
High aspect-ratio (height/diameter) are undesirable
because the packing density can vary with height
In order to reduce the die-wall effect
- Use the smaller particle or large die
recommended compact diameter and thickness
1. Diameter: ~X250 of the average agglomerate size of powder
2. Thickness: ~X40 of the average agglomerate size of powder
S. J. Glass and K. G. Ewsuk, MRS Bulletin, Dec., 24 (1997)
Advanced Electronic Ceramics I (2004)

3. Dual-action and Single-action Pressings
Density gradients
predicted by the FE
compaction model in a
quarter section of a 94
wt% alumina tube.
The 25,4 mm long
tubes were compacted
uniaxially at 103.4
Mpa by: a) dual-action
pressing and b) single-
action pressing from
the top. Density
changes with color
from blue to green,
yellow, orange, and
red.
K.G. Ewsuk et al., Am.Ceram.Soc.Bull., 80(1), 53 (2001)
Advanced Electronic Ceramics I (2004)
Green-Density Gradient along the pressing axis
The density gradients
through the cross
section of a
cylindrical powder
compact of 94wt.%
alumina after uniaxial
pressing at 69 MPa:
a) measured by
ultrasound velocity
measurements
completed on a
bisque-fired part, and
b) predicted using the
FE compaction model
assuming a die wall
friction coefficient of
0.25.
K.G. Ewsuk et al., Am.Ceram.Soc.Bull., 80(1), 53 (2001)
Advanced Electronic Ceramics I (2004)

4. Compaction curve
S. J. Glass and K. G. Ewsuk, MRS Bulletin, Dec., 24 (1997)
Advanced Electronic Ceramics I (2004)
Compaction: the effect of granules
Easy rearrangement No rearrangement proper rearrangement
No deformation deformation at center proper deformation
S. J. Glass and K. G. Ewsuk, MRS Bulletin, Dec., 24 (1997)
Advanced Electronic Ceramics I (2004)

5. The properties for the granules
1. Hard enough to rearrange during die filling and low-pressure compaction
2. Soft enough to completely deform under maximum pressing pressure
S. J. Glass and K. G. Ewsuk, MRS Bulletin, Dec., 24 (1997)
Advanced Electronic Ceramics I (2004)
Compaction
S. J. Glass and K. G. Ewsuk, MRS Bulletin, Dec., 24 (1997)
Advanced Electronic Ceramics I (2004)