MANUFACTURING AND EQUIPMENT
FABRICATION OF HIGH-DENSITY QUARTZ CERAMICS:
RESEARCH AND PRACTICAL ASPECTS.
PART 2. SHAPING METHODS
E. I. Suzdal’tsev
Translated from Novye Ogneupory, No. 9, pp. 26 – 35, September, 2005.
Original article submitted January 3, 2005.
Methods for molding of quartz ceramic preforms from quartz glass suspensions are surveyed and various as
pects of their practical application are discussed.
In what follows, a survey of the currently employed tech-
nologies for molding of ceramic preforms from quartz glass
suspension is presented in some detail, and the strengths and
weaknesses of these technologies are compared.
1. SLIP CASTING FROM AQUEOUS SUSPENSIONS
Slip casting is a technique based on the property of sus
pensions to form a solid deposit on the surface of a porous
mold. At present, this technique is principal for manufacture
of components from quartz ceramics .
Slip casting is good for molding components from oxi
des, carbides, or other materials suspended in an appropriate
liquid. For each material, appropriate liquid medium and dis
persant are elected. For oxides, water is a good choice and
provides the needed rheological and technological properties
of suspensions. Specific requirements, occasionally even
conflicting, are placed on slips: they should; (i) have a low
viscosity to provide good flowability; (ii) have a low settling
velocity; (iii) provide a clean surface for molding; (iv) have
an adequate mass build-up rate; (v) be free of foam, gas bub
bles and other inclusions; (vi) provide a low shrinkage dur
ing drying and burning, and (vii) provide a high strength for
the semi-finished (green) product.
For this reason, the optimum, or compromise, choice of
slip casting parameters that would meet the aforesaid requi
rements and provide a high quality of the end products is an
issue of most important concern.
So, in the case of quartz glass suspensions, increasing the
percentage of finely dispersed particles to improve the green
perform strength and sintering rate  causes a decrease in
mass build-up rate and an increase in rejection rate during
molding because of the high shrinkage stress . Increasing
the percentage of large particles (i) increases the mass build-
up rate; (ii) decreases the shrinkage during drying and sin
tering; (iii) increases the settling velocity; (iv) decreases the
strength of green performs; (v) decreases the sintering rate;
and (vi) decreases the ceramic strength . The compromise
reached on major properties of the quartz glass slip 
makes it possible to prepare high-quality large-sized ceramic
components with a porosity of 8 – 10%.
According to current concepts, many important proper
ties of dispersed systems are closely related to the structure
of the double electric layer [4 – 6]. The formation of a double
electric layer in aqueous quartz glass suspensions involves
surficial dissociation of the solid-phase material by the
Refractories and Industrial Ceramics Vol. 46, No. 6, 2005
1083-4877/05/4606-0371 © 2005 Springer Science+Business Media, Inc.
Tekhnologiya Research and Production Enterprise, Obninsk,
Kaluga Region, Russia.