SCIENTIFIC RESEARCH AND DEVELOPMENTS
IMPROVING MOLD SETS FOR LARGE-SIZED COMPONENTS
PREPARED FROM AQUEOUS SLIPS.
PART 2. INTENSIFIED TECHNOLOGY FOR PREFORMS SLIP-CAST
INTO POROUS MOLDS
E. I. Suzdal’tsev,
D. V. Kharitonov,
A. V. Dmitriev,
and T. P. Kamenskaya
Translated from Novye Ogneupory, No. 5, pp. 21 – 28, May, 2006.
Original article submitted January 10, 2006.
Basic methods for manufacture of large-sized complex-shaped ceramic components by casting from aqueous
slips — cryogenic, centrifugal, electrophoretic, etc. — are considered. Of these, the slip casting in porous
molds is advantageous in terms of cost and technological simplicity. To achieve further progress, attention
should be focused on the development of adequate molding equipment to minimize the rejection rate of fi-
The shaping of ceramic preforms is a notoriously com-
plex technological process, and for this reason the techniques
and molding equipments normally used to prepare compo-
nents from aqueous slips need some comment. The shaping
of preforms from aqueous slips of inorganic materials has
been discussed in some detail in [1 – 4]. Major techniques
commonly employed for that purpose are: (i) casting into po
rous molds, (ii) cryogenic, (iii) centrifugal, (iv), electropho
retic shaping (v), shaping under pressure (vi) vacuum-as
sisted shaping, and (vii) heat-assisted shaping.
The range of techniques suited for making large-sized
complex-shaped components such as aerial fairings is rather
limited. First, the size, profile, and performance parameters
of fairing preforms rule out the possibility of using cryogenic
shaping techniques. For example, viewed technologically,
one may imagine that the cryogenic method can be applied
if, during the molding, the slip is cooled through the inner or
outer shell of a metallic mold. However, as regards the qua
lity of product, this method is clearly deficient since the po
rosity of the molded preform (even if a highly concentrated
slip is used, with solid phase concentration C
reaches 25 – 26%. Preparation of densely sintered high-
strength preforms from such a material requires very strict
control over a range of negative factors such as the crystalli-
zation of quartz glass, shrinkage and buckling of the pre-
forms during sintering, the use of high sintering tempera
tures, and the difficulty of maintaining an optimum ratio of
crystalline phases in the glass ceramic of lithium aluminosili
cate composition. A mold set for manufacture of the fairing
preforms from aqueous quartz glass slips by a cryogenic
method (using liquid nitrogen to cool the suspension on the
surface of a metallic core) was designed but, regrettably,
proved to be a modest success.
Sufficient attention has been given to the molding of pre
forms from aqueous inorganic slips by centrifugal techniques
in the literature. However, most researchers agree that this
method is preferably used to shape cylindrical components
[1, 3]. Indeed, it is virtually impossible to provide an equal
centrifugal force to particles of different mass and staying
away from center of rotation at different distance (Fig. 1).
Furthermore, the centrifugal method for all its advantages
fails to provide high-density preforms uniform over the bulk,
of which data presented in Fig. 2 are illustrative .
In this context, the experience gained in the use of this
method at the Tekhnologiya Research and Production Enter
prise is worthy of comment. Dating back some 30 years, a
Refractories and Industrial Ceramics Vol. 47, No. 3, 2006
1083-4877/06/4703-0158 © 2006 Springer Science+Business Media, Inc.
Tekhnologiya Research and Production Enterprise, Obninsk, Ka
luga Region, Russia.