UDC 666.295:666.3-1
CHEMICAL RESISTANCE OF ZINC-BEARING GLASS-CERAMIC GLAZE
FOR QUARTZ GLASS CERAMICS
N. Yu. Mikhailenko
1
and N. V. Rudkovskaya
1
Translated from Steklo i Keramika, No. 4, pp. 8 – 10, April, 2003.
The chemical resistance of a zinc-bearing glass-ceramic glaze intended to protect refractory products made of
quartz glass ceramics from alkali media is investigated. The water and acid resistance of the glaze exceeds the
analogous parameters of traditional glaze glasses. The alkali resistance of quartz glass ceramics coated by the
glass-ceramic glaze increases more than 4 times.
Quartz glass ceramics are high-silica materials produced
by sintering milled quartz glass or various types of amor
-
phous silica [1 – 3]. Owing to the high thermomechanical
and electroengineering characteristics, radiation permeabi-
lity, technological efficiency, and low cost, quartz glass ce-
ramics finds wide application in spacecraft engineering, nu-
clear power, and metallurgy. Recently, the application areas
of this material have been extended to refractories in the
chemical and glass industry sectors. In particular, there has
been practical experience in using quartz glass ceramics to
produce refractories for glass-melting furnaces. However,
wide use of quartz glass-ceramic refractories is limited due
to the low alkali resistance of this material, especially at ele-
vated temperatures.
The intensity of chemical corrosion of a refractory in ag
-
gressive media is primarily determined by the chemical na
-
ture of the refractory and the medium interacting with it.
Qualitatively, the properties of quartz glass ceramics are cor
-
related with the quartz glass and exhibit high resistance to re
-
actants of group I (water, acid solutions and acids) and also
to liquid metals and gases. In contact with reactants of
group II (alkalis, fluoric and phosphoric acids and their
salts), the material undergoes intense chemical corrosion, up
to complete destruction [4]. A promising method for improv
-
ing the corrosion resistance, service reliability, and durability
of quartz glass-ceramic refractories operating in contact with
high-temperature alkali media is the deposition of chemi
-
cally resistant glaze coatings.
The complexity of glazing quartz glass ceramics, which
is characterized by low thermal expansion, is that its TCLE is
hard to coordinate with the TCLEs of most known glazes. A
substantial difference between the TCLEs of the glaze and
the substrate generates numerous defects in the coating and
decreases the strength of its adhesion to the substrate [5, 6].
A promising line for solving this problem is to develop glass-
ceramic glazes, whose phase composition is represented by
crystalline phases with low thermal expansion, which pro-
vides for a significant decrease in the thermal expansion of
the coating in general and a better coordination with the sub-
strate.
Researchers at the D. I. Mendeleev Russian Chemical
Engineering University have developed a zinc-bearing glass-
ceramic glaze for quartz glass ceramics, whose chemical
composition is in the willemite range of the K
2
O – ZnO –
TiO
2
– SiO
2
system [7]. The fritted vitreous glaze is applied
to the surface of quartz glass ceramics by immersion or cast-
ing and is fired according to a two-stage schedule with expo
-
sures at 1280°C (stage I, spreading of glaze) and 1050 –
1150°C (stage II, crystallization of coating). The thickness of
the coating layer is 160 – 200 mm. A finely dispersed glass-
ceramic volume structure is formed in the glaze under firing,
consisting of willemite crystals and willemite-based solid so
-
lutions, zircon titanates, rutile, and a residual vitreous phase.
The glaze coating forms strong adhesion to the substrate
without crackle, flaking, or other defects.
The present work shows the results of studying chemical
resistance of the specified glass-ceramic glaze in various me
-
dia. The substrate for depositing the glaze was glass ceramics
produced by the Simvol Company (Vladimir Region). The
chemical resistance of vitreous frit and crystallized glaze
were determined by the granular method based on the weight
loss in material samples, and the chemical resistance of the
glass-ceramic coating was determined by the mold surface
method based on weight losses in quartz glass-ceramic sam
-
ples after boiling in water, acids, and in a caustic soda solu
-
tion. For reference purposes the behavior of unglazed glass
ceramics in reaction with water, alkali, and acid media was
evaluated.
Glass and Ceramics Vol.60, Nos.3–4, 2003
108
0361-7610/03/0304-0108$25.00 © 2003 Plenum Publishing Corporation
1
D. I. Mendeleev Russian Chemical Engineering University, Moscow,
Russia.