RESEARCH IN THE AREA OF PREPARING MATERIALS
BASED ON FUZED QUARTZ HCBS.
PART 5. EFFECT OF SINTERING ON MATERIAL POROSITY
Yu. E. Pivinskii
and P. V. Dyakin
Translated from Novye Ogneupory, No. 6, pp. 47 – 55, June 2015.
Original article submitted December 25, 2014.
The effect of sintering on ultimate strength in bending and compression indices is studied for castings based
on both fuzed quartz HCBS with different fineness, and cast systems with a granular filler based upon them.
An effect is detected of a significant increase in strength in the specimen heating stage (nonisothermal
sintering), and maximum strength indices for the majority of materials is achieved after isothermal soaking at
1250°C for 0.5 – 1.0 h. The correlation of shrinkage during sintering with material properties is analyzed. It is
established that maximum strength is achieved with firing shrinkage of up to 1%. Relative compaction indices
(or proportion of sintering pores) are found in the range 0.2 – 0.4.
Keywords: HCBS, sintering, fuzed quartz, isothermal and nonisothermal sintering, ultimate strength in bend-
ing and compression, shrinkage during sintering, density, porosity, relative compaction, proportion of
sintering pores, cristobalite.
In the preceding article of the present series  proper-
ties were provided for original opaque quartz glass (OAO
Dinur fuzed quartz), and also for original dry suspensions
and molding systems with granular filler based upon them.
Shrinkage kinetics and the change in material porosity on
heating and with isothermal sintering were specified.
Data are given in the present article about ultimate
strength in bending and compression indices in relation to
the same factors. A correlation of shrinkage on sintering with
porosity, apparent density, and ultimate strength in bending
indices for specimens based on original suspensions (fuzed
quartz HCBS) and materials with granular filler is estab
lished. A dependence is analyzed on the basis of experimen
tal data for test material strength in bending on relative pro
portion of sintering pores.
EFFECT OF ISOTHERMAL AND NONISOTHERMAL
SINTERING ON STRENGTH PROPERTIES
By analogy with the preceding publication  all re
search on sintering and studying material properties was ac
complished on specimens in the form of bars with a size of
10 ´ 10 ´ 80 mm, which were molded by slip casting in gyp
sum molds [2, 3]. The original suspensions (Table 1) and
systems obtained based upon them with a granular filler (Ta
ble 2) have markedly different properties. The most impor
tant of them are the original solid phase concentration C
grain size composition, and porosity of the semifinished
product obtained. Two of these suspensions presented in Ta
ble 1 (1 and 4) were prepared by traditional HCBS technol
ogy under production conditions [2, 4], and had a normal
density of 1.91 g/cm
, but markedly different finely-dis
persed fraction content (<2 mm). Suspension 2 is a very fine
casting of centrifugal molding, which to a significant degree
is a colloidal component . Suspension 3 was made from a
mixture of suspensions 1 (40%) and 2 (60%).
The dependence of ultimate strength in bending s
on isothermal sintering duration at 1250°C
Refractories and Industrial Ceramics Vol. 56, No. 3, September, 2015
1083-4877/15/05603-0296 © 2015 Springer Science+Business Media New York
Part 1 of the article was published in Novye Ogneupory No. 7
(2014), and parts2–4inNos. 1, 3, and 4 (2015).
OOO NVF Kerambet-Ogneupor, St. Petersburg, Russia.
FGBOU VPO St. Petersburg State Technological University
(Technical University), St. Petersburg, Russia.