FABRICATION OF HIGH-DENSITY QUARTZ CERAMICS:
RESEARCH AND PRACTICAL ASPECTS.
PART 4. PROPERTIES OF MIXED QUARTZ GLASS SLIPS
AND PREFORMS PREPARED BY CASTING INTO POROUS MOLDS
E. I. Suzdal’tsev
Translated from Novye Ogneupory, No. 11, pp. 19 – 24, November, 2005.
Original article submitted April 25, 2005.
Results of a study of rheological properties of quartz glass suspensions and cast preforms prepared from slips
containing oxides and oxygen-free additives (sintering aids) are reported. Controlled routes towards preparing
mixed suspensions that permit fabrication of cast materials with tailored quality parameters are discussed.
At present, the technology for preparation of quartz glass
slips and slip casting are well-established methods [1 – 3].
Still, the mixed slips, their preparation and shaping, have not
yet received sufficient attention despite the fact that many
properties of mixed systems are related in a complicated
manner to the properties of individual components, their
quantitative ratio and dispersity . Viewed in this light, the
study of the properties of mixed suspensions is an issue of
special interest. Its importance is emphasized by the fact that
the rheological and technological properties of suspensions
are essential for preparing preforms with tailored quality
In our study, we used rather inexpensive materials com
mercially available from domestic manufacturers: transpa
rent quartz glass from rejected illumination tubes, titanium
dioxide (in the form of rutile TiO
) of chemically pure
qualification (TU 6-09-1211–67 Specifications) and in the
form of anatase TiO
(TU 10-1360–78 Specifications), bo
ron nitride (TU 2-036-707–77 Specifications), silicon nitride
(2-036-38–72 Specifications), and chromium oxide, of che
mically pure and chemically pure for analysis qualification
(TU 6-09-4272–76 Specifications), to be used as activators
for quartz ceramic sintering.
To prevent the ingress of contaminants, the quartz glass
prior to grinding was chemically treated for cleanness in a
9 – 16% solution of hydrofluoric acid. The precursor material
was wet-ground in a single-step process to be prepared for aque
ous quartz-glass slip . The slip parameters were: density
1.87 – 1.90 g/cm
, viscosity 4.9 ´ 10
– 13.8 ´ 10
Pa × sec,
pH = 4.5 – 7.0. Quartz-glass particle size grading was:
10 – 30% fraction finer than 5 mm, 50 – 90% fraction
5–63mm, 0 – 20.0% fraction 63 – 500 mm.
The additives introduced were finely dispersed powders;
relevant characteristics are given in Table 1. The additives
were introduced into the slip as powders or water suspen-
sions. As needed, to improve the slip flowability, some dis
tilled water was added. As is seen, the addition method pro
posed here is technologically simple.
The suspensions and preforms were tested using standard
techniques and equipment: pH values were measured on an
pH-121 instrument, rheological properties were measured on
a RV-8 viscosimeter, mass buildup rate was measured using a
device shown in Fig. 1. The suspension stability was deter
mined by comparing the density of specimens in different
zones, and the suspension density was determined using
samples drawn over the volume of the shaped material. Den
sity and porosity of the cast preforms were determined as
recommended by the State Standard GOST 2409–95.
Refractories and Industrial Ceramics Vol. 46, No. 6, 2005
1083-4877/05/4606-0391 © 2005 Springer Science+Business Media, Inc.
Tekhnologiya Research and Production Enterprise, Obninsk,
Kaluga Region, Russia.
TABLE 1. Properties of Additives Introduced into the Quartz Glass
Property BN Cr
2.2 5.2 3.44 4.25 3.9
Specific surface, m
5.1 3.3 2.30 1.60 8.7