SYNTHESIS OF COMPLEX COMPOUNDS IN BINARY AND TERNARY
OXIDE SYSTEMS DOPED WITH NANODISPERSE ALUMINUM
T. A. Khabas,
V. I. Vereshchagin,
and O. V. Nevvonen
Translated from Novye Ogneupory, No. 6, pp. 35 – 38, June, 2003.
The effect of nanodisperse powders on the synthesis of magnesium aluminate spinel and cordierite is studied.
Nanodisperse metallic aluminum is shown to be an efficient activator of this synthesis. The optimum concen
tration of aluminum in the mixture should not exceed 5 wt.%.
Studies of nanodisperse electroexplosive metal powders
have opened up fresh opportunities for their application
[1, 2]; still, despite the twenty-years experience in their prac-
tical use, many properties of these powders have remained
poorly understood. A promising area for application of metal
powders is the technology of ceramic materials, in particular,
the solid-phase high-temperature synthesis of thermally sta-
ble compounds .
Synthesis of magnesium aluminate spinel (MgO × Al
cordierite (2MgO × 2Al
), or mullite (3Al
is a power-consuming process normally carried out at high
temperatures and long sintering times. In practice, in order to
reduce the energy expenditure various additions and tech
niques for activating raw materials have been used [4, 5].
Not infrequently, the sintering aids, along with the beneficial
effect of reducing the temperature of sintering or synthesis,
become a source of contamination for the end product. Ex
periments with nanodisperse aluminum powders are a route
to activating the synthesis and sintering of oxide materials.
Pulverized aluminum produced by the electrical explosion of
a wire was used (the material was available from the TPU
Research Institute for High Voltages). The mean metal parti
cle diameter was 80 – 120 nm and the specific surface was
/g. The metal powder was added to a mixture com
posed of pure oxides (in the synthesis of magnesium
aluminate spinel) or natural silicates (in the synthesis of cor
dierite). The silicate materials for synthesis of cordierite
were clay and talcum, with some aluminum hydroxide added
to the mixture. The curves in Fig. 1 show the x-ray reflection
intensities of synthetic phases for different concentrations
of the nanodisperse aluminum powder added; as can be
seen, at temperature above 1150°C, the added metal activates
The data presented suggest a beneficial effect due to the
dimensional factor considering that the ultradisperse alumi
num added differs substantially in dispersity from basic ox-
ide (3 – 10 mm). The bar chart in Fig. 2 gives the particle size
distribution for metallic aluminum. The granular composi-
tion was analyzed by a weight sedimentation method in a li-
quid medium from the starting layer ; particles and aggre-
gates thereof with size less than 1 mm accounted for 67%.
Refractories and Industrial Ceramics Vol. 45, No. 2, 2004
1083-4877/04/4502-0084 © 2004 Plenum Publishing Corporation
Tomsk Polytechnical University (TPU), Tomsk, Russia.
Fig. 1. The amount of synthetic phase [a) magnesium aluminate
spinel; b) cordierite] plotted as a function of the concentration of ex
plosive aluminum powder added B [I
) the absolute intensity of the
x-ray reflection for spinel with d = 0.285 nm; I
) the same for cordi
erite ith d =0.854 nm]. Numerals at curves indicate the synthesis