PRESSURE-MOLDED HIGH-ALUMINA CERAMIC CASTABLES.
3. EFFECT OF PROCESSING ADDITIVES ON PRESSURE-INDUCED
COMPACTION AND PROPERTIES OF BAUXITE-QUARTZ
GLASS MATRIX SYSTEMS
Yu. E. Pivinskii,
Pavel V. Dyakin,
and Petr V. Dyakin
Translated from Novye Ogneupory, No. 4, pp. 126 – 133, April, 2006.
Original article submitted September 13, 2005.
The effect of lignosulfonate (LST) and surface-active substances (SAS) on compaction and properties of
bauxite-quartz glass matrix systems is studied. LST added at an optimum concentration to bauxite-based
highly concentrated ceramic binding suspensions (HCBS) causes a 2 – 3% decrease in preform porosity. In
materials sintered at high temperature the effect of decreased porosity is more pronounced. In preforms
molded at 500 – 700 MPa no defect due to overpress is observed. The SAS, judged from their efficiency for
decreasing porosity, are arranged in ascending order: sodium silicate water glass, sodium tripolyphosphate,
complex organomineral thinner, and FS-20 castament.
Previously [1, 2], the pressure-induced compaction of
materials composed of bauxite-based highly concentrated ce-
ramic binding suspensions (HCBSs) with the addition of
10% highly dispersed quartz glass and 3% plasticizing re-
fractory clay has been studied in some detail. Our goal in this
work was: (i) to find ways to reduce the porosity of pres
sure-molded preforms by introducing, apart from the refrac
tory clay, processing additives; (ii) to study the compaction
process over a pressure range wider than that used in [1, 2];
(iii) to examine the effect of additives on the mechanical
strength of green and dried preforms, and (iv) to study the ef
fect of sintering temperature on properties of a material con
taining various additives.
The processing additives were selected with regard for
their plasticizing or deflocculating (thinning) effect on the
bauxite HCBS. In greater detail, the effect due to ligno
sulfonate (LST) additives was considered. It is well known
 that lignosulfonates are produced from lignin by sulfate
cooking of wood in the production of cellulose . They are
lyophilic water-soluble colloids capable of carrying an elec
tric charge on the colloidal particles; furthermore, they be
long to a class of surface-active substance and are capable of
adsorbing in an orderly arrangement on solid material parti-
cles. Currently, LSTs are understood to be high-molecular-
weight compounds of natural occurrence with molecular
mass varying over a wide range (2000 – 100,000). The ele-
mentary composition of LST, %, is: carbon, 53 – 57; hydro
gen, 5 – 6; sulfur, 4 – 7; nitrogen, £ 5; oxygen, 27 – 34; so
dium, £ 8; calcium, £ 6 . In the refractory molding tech
nology , LST is widely used as a plasticizing and harden
ing additive (bond).
The LST additive was introduced into bauxite HCBS in
the form of a powder of concentration varying from 0.05 to
2.5%. Other inorganic and organic additives, sodium silicate
water glass, sodium tripolyphosphate (SPP), FS-20-grade
castament , and complex organomineral thinner (COMT)
 were used at the same concentration of 0.1% (based on
The object of our study was a suspension prepared under
industrial conditions from a Rota HD sintered bauxite (89%
) from China and fused quartz (10%) . The precur
sor HCBS had median particle diameter d
=6mm; 12% of
the total of particles were less than 2 mm across. The major
plasticizing additive was a 3% suspension of refractory clay
from the Nizhneuvel’skoe deposit.
The additives were introduced to the mixed precursor
suspension with a moisture content of 13%. Adding LST
Refractories and Industrial Ceramics Vol. 47, No. 2, 2006
1083-4877/06/4702-0132 © 2006 Springer Science+Business Media, Inc.
Kerambet Research and Development Firm, St. Petersburg, Rus
sia; St. Petersburg State Technological Institute (Technical Uni
versity), St. Petersburg, Russia.