1070-4272/01/7404-0560 $25.00 C 2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 4, 2001, pp. 560!563. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 4, 2001,
Original Russian Text Copyright + 2001 by Massalimov, Sangalov.
AND INDUSTRIAL INORGANIC CHEMISTRY
Influence of Intensive Mechanical Treatment
on Decomposition of Barium Peroxide
I. A. Massalimov and Yu. A. Sangalov
Research Institute of Low-Tonnage Chemical Products and Reagents, Ufa, Bashkortostan, Russia
Received May 11, 1999; in final form, November 1999
Abstract-The effect of mechanical treatment on the properties of barium peroxide-high-temperature source
of oxygen-is considered.
Peroxide compounds of alkaline-earth metals at-
tract attention of researchers and technologists as
a source of chemically bound and readily evolved
oxygen. These compounds have pronounced thermal
stability and are widely used in metallurgy, polymer
chemistry, medicine, etc. . The basic technological
parameter ensuring the possibility of using the per-
oxides is the temperature of their decomposition in-
to an oxide and active oxygen. The most stable of
the known metal peroxides-barium peroxide, starts
to actively evolve oxygen at 500oC, with complete
loss of oxygen at 900oC . The change in enthalpy
in the process is 75 kJ mol
(BaO) = 3548 kJ mol
is accompanied by rupture of the peroxide bond and
liberation of oxygen .
The kinetics of BaO
dissociation depends on ex-
ternal pressure and atmosphere composition. In the
atmosphere of oxygen, BaO
is more thermally stable,
as would be expected, whereas in the atmosphere of
water vapor or carbon dioxide it starts to decompose
already at 200oC . However, the presence of water
vapor or carbon dioxide in the reaction volume is not
always desirable or acceptable. The synthesis tempera-
ture (with peroxide used) may be lower than the tem-
perature at which intensive oxygen evolution occurs.
In such cases, modification of barium peroxide is
desirable, lowering the temperature of its dissociation.
In the present communication, a method for con-
trolling the temperature of barium peroxide decompo-
sition in air under normal pressure is proposed, rely-
ing upon intensive mechanical treatment.
Barium peroxide [GOST (State Standard) 6054375]
was preliminarily dried at 105oC. Barium peroxide
powders-both initial and mechanically treated-were
stored in a desiccator over calcium chloride. An anal-
ysis of the IR spectra of the samples demonstrated
the absence of water and carbon dioxide adsorbed
The mechanical treatment of barium peroxide was
done in the working chamber of a D-109 disintegrator.
Powders mechanically treated to varied extent were
obtained by repeated or multiple grinding in the same
apparatus. Sedimentation, thermal, and X-ray diffrac-
tion analyses of the initial and mechanically treated
samples were made under identical conditions.
The sedimentation analysis was made on a Retsch
Lumosed photoelectric instrument (Germany). A 2-g
sample was placed in a chamber filled with cyclo-
hexanol, thoroughly stirred, and the chamber was
mounted on the analyzer. In the course of particle
settling, the intensity of a light beam passing through
the chamber changed, which was recorded by the an-
alyzer. A computer connected to the analyzer calcu-
lated by means of appropriate software the size dis-
tribution of the particles.
Thermal analysis was done on a Q-1000 deriva-
tograph (Hungary), with differential-thermal (DTA)
and thermogravimetric (TG) curves recorded. The ther-
mal effects were evaluated from the DTA curves,
using reference samples.
X-ray analysis was made on a DRON-2.0 diffrac-
tometer. The BaO
unit cell is tetragonal, with two
molecules and each barium ion surrounded by six
peroxide ions forming an octahedron. The unit cell
parameters of the initial powder were as follows:
a = 3.818 and c = 6.854 A.