PROPERTIES OF POWDERS OF FUSED SPINELS AND PERICLASE
PULVERIZED BY DIFFERENT TECHNIQUES
I. D. Kashcheev
and K. G. Zemlyanoi
Translated from Novye Ogneupory, No. 12, pp. 36 – 42, December, 2004.
Original article submitted February 24, 2004.
The properties of electrofused spinel and periclase powders prepared by different milling techniques are re
ported. Vibratory milled specimens display a higher structure imperfection of the surface, and the amorphous
surface layer differs compositionally from the percursor material. In the pulverized products, contaminating
elements (Na, Si, and, to a lesser extent, Fe) tend to migrate towards the surface of particles. Vibro-milled
powders show a better sinterability in comparison to jet-milled powders. Pulverization produces little effect
on the properties of precursor fused periclase.
Finely dispersed powders are the starting raw materials
in many technologies. The increase in dispersity of a material
causes an increase in the interphase surface and, conse-
quently, a change in its microstructural features [1, 2]. Dur-
ing pulverization, changes are imparted to the crystal struc-
ture and the energy state of particles in the surface layer
which, in turn, produces an effect on the interaction of parti-
cles with the surrounding medium, on the chemical interac-
tion between particles , phase transformations in ZrO
and other processes.
Fine pulverization has gained importance in the techno
logy of thixotropic unshaped materials and ceramic castables
; it should be recalled that at present, unshaped compo
nents in quality are frequently superior to shaped compo
nents, and demand for unshaped refractories is increasingly
on the rise, whereas for shaped components, it is clearly in
Buildup and development of an amorphous surface layer
on grains are controlled by the physicochemical pulveriza
tion conditions. The larger the surface and the higher the brit
tleness of a material (corundum, quartz, etc.), the higher the
amorphization of the surface. In such materials, the energy
conveyed has no time to dissipate, and the disintegrated par
ticles accumulate a major part of the energy, which is spent
for the creation of intrinsic defects .
In industrial practice, mechanical milling is the most
used and the least expensive method for the large-scale pro
duction of finely dispersed powders. This technique makes it
possible to prepare powders of particle size 0.1 – 0.5 mm,
which is quite sufficient for use in the production of refrac-
tory materials. For fine and ultrafine grinding in the refrac-
tory industry, vibratory milling (the most sophisticated ver-
sion of ball milling) and jet milling have gained wide accep-
tance; these techniques are commonly used to treat sintered
and fused materials (corundum, spinel, mullite, etc.).
In our studies, we have focused on pure materials that are
traditionally used in the refractory industry: ShD-type fused
alumomagnesian spinel of different chemical compositions
(available from Dinur Joint-Stock Co., Pervouralsk), SpB-type
spinel, and PP-type fused periclase (available from Ogne
upory JSC, Bogdanovich). The precursor materials were
ground using vibratory and jet milling techniques. The spi
nels were prepared using different technologies. By Dinur
JSC technology, Al
was added to molten magnesium ox
ide, and the molten mixture was cast into molds. By
Ogneupory JSC technology, a mixture of magnesia and alu
mina powders was melted in an electric arc furnace (using
the so-called “block fusion” technique).
The chemical composition of precursor materials and
end products are given in Table 1.They differ in concentra
tion of alkaline oxides (MgO and Al
) and minor compo
nents, and, as will be shown later, in phase concentration and
distribution (periclase, spinel, and glassy phase).
Fused periclase (available from Ogneupory JSC) was
prepared by electric melting of brucite. The vibratory milling
of materials was effected using an M10 vibratory mill with a
1 : 3 material-to-grinding body (steel balls) ratio; the vibra
Refractories and Industrial Ceramics Vol. 46, No. 1, 2005
1083-4877/05/4601-0042 © 2005 Springer Science+Business Media, Inc.
Urals State Technical University, Ekaterinburg, Russia.