AQUEOUS SLIP CASTING OF COMPLEX-SHAPED CERAMIC
F. Ya. Borodai,
Yu. V. Lipovtsev,
M. Yu. Rusin,
and A. S. Khamitsaev
Translated from Novye Ogneupory, No. 6, pp. 25 – 32, June, 2006.
Original article submitted March 14, 2006.
Results of theoretical and experimental studies of the process of aqueous slip casting of complex-shaped ce
ramic components using plaster molds are given. A technology for manufacture of complex-shaped homoge
neous high-quality preforms from quartz ceramics such as aerial fairing shells is proposed.
The casting of aqueous slip into plaster molds is a cur
rently employed technique for shaping thin-walled ceramic
components, for example, aerial fairing shells [1, 2]. The
buildup of a preform on the surface of a complex-profile
mold involves two major processes:
– capillary suction of the liquid phase of the slip by the
plaster mold and movement of slip particles towards the
mold and their deposition on the mold surface;
– deposition of slip particles on the mold surface under
the action of gravity.
One of the two processes becomes prevailing depending
on the density, viscosity and grain composition of the slip.
A judicious trade-off between these parameters is a major
concern in developing a technology for shaping preforms.
With the former process predominant, a more dense and uni
form packing of particles is achieved, and the preform shape
exhibits higher strength characteristics.
Apart from the capillary suction and gravity forces, a slip
particle is subjected to the buoyancy force of liquid phase
(static lift) and to the viscous force of the medium. The parti
cle’s velocity vector is controlled by the direction and inten
sity of all the forces involved. With allowance for Stokes’
law the equation of motion of a particle towards the curved
surface of a mold takes the form
VV r P P
=- + -()( )cos,6ph q
where m is the mass of the particle; V
is the velocity of mo
tion of the particle towards the preform surface; V
speed of water filtration; r is the radius of the particle; h is
the viscosity of the medium (the slip); q is the horizontal
slope of the tangent to the curved surface of the preform;
is the gravity force, P
= mg; P
is the buoyancy force,
g; r is the particle density; r
is the slip density;
is the slip mass; m = r(4pr
Equation (1) describes the transient motion of a particle
from the state of rest to a fully established quasi-stationary
motion when the inertial force on the left side of the equation
can be neglected. According to , one has the solution
is the gravitational deposition velocity of a slip particle),
expression (2) can be written as
cos q. (3)
The particle velocity V
is a major factor controlling the
preform buildup rate; by analogy with Eq. (3), the preform
buildup rate for a curved surface can be written as
h = h
cos q, (4)
is the portion of the wall thickness that was built up
by capillary filtration of water in the plaster mold; h
Refractories and Industrial Ceramics Vol. 47, No. 3, 2006
1083-4877/06/4703-0192 © 2006 Springer Science+Business Media, Inc.
Tekhnologiya Research and Production Enterprise, Obninsk,
Kaluga Region, Russia.