NANODISPERSED SILICA AND SOME ASPECTS OF NANOTECHNOLOGY
IN THE FIELD OF SILICATE MATERIALS SCIENCE. PART 4
Yu. E. Pivinskii
Translated from Novye Ogneupory, No. 2, pp. 45 – 55, February, 2008.
Original article submitted December 10, 2007.
Examples are given of the use of nanodispersed forms of silica in making refractory and high-porosity
(thermal insulation) materials. There is a discussion of the use of finely divided silica materials and wet
grinding in the technologies of glass and glass ceramics. Conditions are formulated for wet grinding to reduce
the grain size of hydrating materials. Prospects are considered for using technologies based on finely divided
silica in making many silicate and oxide materials.
NANOSILICA IN THE TECHNOLOGY
OF REFRACTORIES AND THERMAL
The previous parts of this paper have given examples of
the effective use of various forms of nanosilica in refractory
technology. There is a recent publication  on making
cement-free corundum concretes, where results are given on
the effects of the content of the silica sol (SS) used as
The initial silica sol had a concentration of 40 wt.%,
which corresponds to a volume concentration of 25%, i.e.,
the volume content of the liquid phase in the system
constituted 75%. The content of the SS of that concentration
varied in the range 5.0 – 8.7%, which corresponds to a
humidity content of the mass of 3 – 5.2%. The SS content in
the dry mass is then in the range 2 – 3.5%. On the addition of
5% SS, the water content of the mass is raised to 4.5% by the
addition of water. The structure-forming or gel-forming
substance in making concretes is ground magnesian sinter
(median diameter d
= 15 mm). The minimum porosity and
maximum strength corresponded to a composition contain
ing 8.7% SS (3.5% on the dry weight), but even with 5% SS,
the parameters quoted in the paper exceeded the similar ones
for concretes containing 3% of high-alumina cement.
In the same paper, the grain-size composition was
optimized by examining materials containing simultaneously
silica sol and microsilica (MS). By comparison with low-
cement concretes, the technological or working advantage of
cement-free concretes based on silica sol is that during
drying most of the water is lost at 80 – 100°C. For low-
cement concretes, that interval related to dehydration of the
cement is 130 – 180°C. If there are deviations in the mode of
drying, there may be explosive cracking because a critical
vapor pressure is exceeded within the concrete during drying
(p. 69 of ).
These data and others make it quite clear that the
functional essence of adding silica sol and microsilica to the
concrete  is analogous to the technologies for making
high-alumina ceramoconcretes, in which the finely divided
particles in optimal amounts are produced during the
manufacture of the initial finely divided silica for their
production. The comparison presented in the second part of
the paper shows that in this respect the form of technology
based on finely divided silica has indisputable advantages.
On that basis, the compositions and technologies used for
making the low-cement concretes in  imply that this
gives a variety of ceramoconcrete, which resembles other
foreign cement-free concretes that became available at the
end of the last century (pp. 457 – 464 of ). The basis for
this is that all these concretes fall under the definition of
ceramoconcrete formulated by ourselves in the 1970s (p. 241
Properties have been reported  for corundum-
graphite-carbide-silica refractories made by pressing with the
use of binding agents based on modified hydrolyzed ethyl
silicates, which raise the plasticity and increase the strength
of the semifinished material. During the firing, the active
silicon dioxide obtained by decomposition of the ethyl
silicate accelerates the sintering. The resulting synthesized
Refractories and Industrial Ceramics Vol. 49, No. 1, 2008
1083-4877/08/4901-0067 © 2008 Springer Science+Business Media, Inc.
End. Parts 1 – 3 were published in Nos. 11 and 12 for 2007 and
No. 1 for 2008.
Kerambet Refractory Corporation, Russia.