SCIENTIFIC RESEARCH AND DEVELOPMENT
RESEARCH IN THE AREA OF PREPARING MATERIALS
BASED ON FUZED QUARTZ HCBS.
PART 9. EFFECT OF ALKALI ADDITIONS ON MATERIAL
CRISTOBALITIZATION AND THERMAL EXPANSION
AFTER NONISOTHERMAL HEATING
Yu. E. Pivinskii,
P. V. Dyakin,
and A. Yu. Kolobov
Translated from Novye Ogneupory, No. 3, pp. 123 – 128, March 2016.
Original article submitted January 12, 2016.
The effect of alkali-containing additive of water soluble lump silicate on the degree of cristobalitization and
thermal expansion of specimens based on fuzed quartz HCBS is studied. The additive content (for Na
varied within the limits of 0.1 – 2.0% or from 0.025 to 0.50%. In specimens given prior nonisothermal heating
to 1500°C the cristobalite content is from 32 – 34% (specimens without additive) to 88 and 96% (specimens
with 1 and 2% additive). Specimen maximum thermal expansion corresponding to transition of low-tempera-
ture into high-temperature cristobalite occurs within a limited range of 150 – 300°C.
Keywords: fuzed quartz, low- and high-temperature cristobalite, lump silicate, thermal expansion,
nonisothermal heating, quartz steel-pouring refractories.
It is well known that of all the existing modifications of
silica cristobalite is the most refractory and chemically stable
[1, 2]. In quartz steel-pouring refractories transformation of
amorphous fuzed quartz into cristobalite is accomplished di
rectly during high-temperature operation [2 – 6]. In the pre
vious article of the current series  the process of sintering
and cristobalitization was studied for both original speci
mens and those containing alkali additions during high-tem
perature isothermal heating. The task is set in the present ar
ticle of studying the effect of alkali-containing additives on
phase composition and thermal expansion of specimens sub
jected to prior heat treatment in a nonisothermal heating re
gime up to 1500°C.
SOME ASPECTS OF CRISTOBALITIZATION
In contrast to classical Fenner diagrams for silicon it has
been demonstrated repeatedly that in the diagram for the
composition of pure silica (without significant impurities)
there is no formation of tridymite as an independent phase
[2 – 5]. For both high purity transparent and opaque quartz
glass with a moderate impurity content at elevated tempera
ture there is typically cristobalite formation [1 – 4]. This is
explained by the fact that quartz glass (fuzed quartz) has a
cristobalite-like structure, and therefore for forming cristo
balite nuclei less marked rebuilding of the structure is re
quired [2, p. 97]
From the point of view operational life of quartz refrac
tories the factor of an increased rate of matrix system
cristobalitization to all appearances plays a favorable role.
As has been noted previously [1, 2, 5, 6] compared with
materials cristobalite has maximum refractoriness
and chemical stability. Therefore, during high-temperature
steel pouring accelerated cristobalitization of a matrix sys
tem is desirable, determining as a rule the life in service of
Refractories and Industrial Ceramics Vol. 57, No. 2, July, 2016
1083-4877/16/05702-0135 © 2016 Springer Science+Business Media New York
Part 1 of the article was published in Novye Ogneupory No. 7
(2014), parts 2 – 7 in Nos. 1, 3, 4, 6, 7, and 9 (2015), and part 8 in
No. 1 (2016).
OOO NVF Kerambet-Ogneupor, St. Petersburg, Russia.
FGBOU VPO St. Petersburg State Technological University
(Technical University), St. Petersburg, Russia.
OAO Dinur, Pervoural’sk, Sverdlovsk Region, Russia.