VARYING THE GRANULOMETRIC COMPOSITION
OF AN ELECTROFUSED-CORUNDUM-BASED CERAMIC
WITH A PORCELAIN BINDER TO CONTROL ITS OPEN POROSITY
A. V. Belyakov,
Zaw Ye Maw Oo,
N. A. Popova,
Ye Aung Min,
and Kyaw Lwin Oo
Translated from Novye Ogneupory, No. 2, pp. 34 – 37, February, 2016.
Original article submitted January 7, 2016.
A study is made of a strong porous ceramic based on granular mixes of a filler — electrofused corundum with
particle sizes of 2 – 3 and 0.5 mm (95 wt.% of the mix) — and a porcelain binder (5 wt.%). Several mixes
were prepared with different values for the 2 – 3 mm/0.5 mm ratio of filler-particle sizes: 0/95, 35/60, 40/55,
45/50, 50/45, and 95/0. The specimens were pressed at pressures of 25, 50 and 100 MPa and fired at tempera
tures of 1350 and 1450°C. The sintered specimens ranged from 19 to 143 MPa in ultimate flexural strength
and 17 to 26% in open porosity. The results are attributed to the formation of a framework in the semifinished
product along with regions outside the framework. The new porous permeable ceramic is promising for use in
the form of filters and supports for ceramic membranes.
Keywords: ceramic, open porosity, strength, granular powders, electrofused corundum, ceramic filters.
Porous materials are widely used as catalyst supports in
processes that involve oxidation, hydration, and dehydration
at high temperatures, in the processing of raw materials in
aggressive media, and in endothermic and exothermic reac
tions. In particular, various types of corundum-based materi
als that are characterized by a high degree of chemical inert
ness are used for these purposes. Thanks to the high porosity
and unique structure of porous materials, they have specific
properties that differ greatly from the properties of dense ma
terials with a similar chemical composition [1 – 3].
The goal of the investigation being discussed in this arti
cle was to obtain a strong, porous, permeable ceramic based
on electrofused corundum (EFC) for filters and membrane
supports. Porous materials that have a narrow pore-size dis
tribution and an average pore size of 4 – 6 mm are best suited
for use as filtering elements .
Electrofused corundum F20 (0.5 mm) and F100
(2 – 3 mm) were used as the filler and porcelain powder
(gel-like porcelain mass of grade LT, referred to below as
porcelain LT) was used as the binder. The binder strongly
bound the EFC grains to one another during the firing opera
tion. All of the masses that were studied consisted of
95 wt.% granular filler and 5 wt.% binder. In order to obtain
porous permeable ceramic products with adequate strength
for their intended application and good filtering properties,
the following values were used for the 2 – 3 mm/0.5 mm ra
tio of the content of coarse grains of the filler to fine grains
of the filler: 0/95; 35/60; 40/55; 45/50; 50/45; 95/0. Pressing
pressure in the experiment was 25, 50, and 100 MPa (pres
sures of 25 and 50 MPa were used for the compositions 0/95
and 95/0). The highest temperatures during the firing of the
ceramic semifinished products were 1350 and 1450°C. The
specimens that were obtained were used to study porosity,
density, and mechanical strength in accordance with the
methods described in .
Dried gel-like porcelain mass LT (5 wt.%) was mixed
with the filler by the dry method for a certain period of time.
The mixing operation was performed in a corundum drum
with corundum grinding balls. The ratio grinding balls:mate
rial = 1:1. The total amount of time taken to mix the charge
was 3 h. After mixing and the introduction of a temporary
binder, we obtained a powder molding mix that was subse
quently used to obtain test specimens by pressing. The tem
porary binder was an aqueous solution of polyvinyl alcohol
Refractories and Industrial Ceramics Vol. 57, No. 1, May, 2016
1083-4877/16/05701-0077 © 2016 Springer Science+Business Media New York
Russian University of Chemical Technology, Moscow, Russia.