ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 12, pp. 2036 !2039. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + G.F. Klyakin, V.A. Taranushich, 2007, published in Zhurnal Prikladnoi Khimii, 2007, Vol. 80, No. 12, pp. 1958!1961.
AND INDUSTRIAL INORGANIC CHEMISTRY
Phase Stability in the System Constituted
by Ammonium Nitrate, Potassium Dichromate,
and Alkaline-Earth Metal Nitrates
G. F. Klyakin and V. A. Taranushich
South-Russian State Technical University, Novocherkassk, Rostov-on-Don oblast, Russia
Received April 10, 2007
Abstract-Methods for modification of ammonium nitrate as an oxidizing agent for ecologically safe solid
propellants were sought for and the influence exerted on phase transitions in ammonium nitrate by three-
component inorganic additives in which a synergic effect lowering the transition energy is manifested was
A promising approach that can be employed to
make lower the cost of solid propellants and diminish
the amount of chlorine-containing discharges is to
use ammonium nitrate (AN) as an oxidizing agent
partly or completely replacing ammonium perchlorate
(APC). The cost of ammonium nitrate is an order of
magnitude lower and it forms no ecologically danger-
ous products in combustion. The most important dif-
ficulties associated with the development of AN-based
fuels consist in that AN undergoes polymorphic trans-
formations at working temperatures of the fuel, which
are accompanied by an increase in volume, and its
combustion velocity is low.
The existing technical solution  based on cocrys-
tallization of AN with a binary additive (ammonium
nitrate + calcium nitrate) eliminates only the phase
stability problem. Additional use of catalysts making
higher the thermal decomposition rate and combustion
velocity in a phase-stabilizing additive to AN will
allow an integrated solution of the problem of its
suitability as an oxidizing agent for ecologically safe
One of the most effective and readily available
compounds, potassium dichromate (PDC), was used
as a catalyst. It was introduced into a binary addi-
tive composed of potassium nitrate (PN) and nitrates
of alkaline-earth metals, such as magnesium nitrate
(MN), calcium nitrate (CN) and strontium nitrate (SN).
In some systems, potassium nitrate was replaced with
potassium perchlorate. The total content of the addi-
tive in modified AN was 4%.
Experiments were carried out using Scheffe’s de-
sign , which makes it possible to evaluate nonlin-
ear effects in binary and ternary additive mixtures.
The experiments were replicated and their results were
used to construct polynomial models whose adequacy
was estimated by Fisher’s criterion. The models were
constructed with exclusion of nonsignificant (accord-
ing to Student’s criterion) coefficients, followed by
recalculation , which yielded adequate models with
the smallest number of terms.
The additives were introduced into AN by isother-
mal crystallization from aqueous solutions. The solid
phase was additionally dried and subjected to differ-
ential-thermal analysis (DTA). After the drying, all
procedures were performed in a chamber with a rela-
tive air humidity not exceeding 50%.
The DTA of a powder of the <400-mm fraction was
made in the temperature range from 350oC to the melt-
ing point. The weight of a sample for analysis was
about 0.1 g, and the heating rate, 3 deg min
curves were recorded in the coordinates of the sample
temperature and the temperature difference between
a sample and the reference. The phase transition en-
ergy (J g
) was evaluated by the area under the cor-
responding peaks in the DTA diagram, with the use
of a calibration plot.