The thermal decomposition of an explosive material is accompanied by generation of a certain amount of heat and, under certain
conditions, can lead to the well-known phenomena of self-ignition. Therefore, it is of great importance to predict whether
or not an explosive material will ignite under given conditions (specimen mass and shape, surrounding temperature, etc.).
An own computer program named THERMEX, for studying thermal ignition phenomena, is discussed in this paper. The program uses
the finite difference method to describe the reactive heat conduction phenomena in infinite slab, cylindrical, and spherical
geometry of explosive materials.
The analysis of the stability requirements of the finite difference method applied in the program is carried out. The program
is tested by the comparison of calculated results with the results of calculation by other authors. Reasonable agreement was
found under identical computational conditions.
The kinetics of the thermal decomposition of ammonium perchlorate at temperatures between 215 and 260°C is studied, in this
work, by measuring the sample mass loss as a function of time applying the isothermal thermogravimetric method.
From the maximum decomposition rate – temperature dependence two different decomposition stages, corresponding to two different
structural phases of ammonium perchlorate, are identified. For the first region (215–235°C), corresponding to the orthorhombic
phase, the mean value of the activation energy of 146.3 kJ mol–1, and the pre-exponential factor of 3.43⋅1014 min–1 are obtained, whereas for the second region (240–260°C), corresponding to the cubic phase, the mean value of the activation
energy of153.3 kJ mol–1, and the pre-exponential factor of 4.11⋅1014 min–1 are obtained.
The ageing of double base rocket propellants (DB rocket propellants), which is a consequence of chemical reactions and physical
processes that take place over time, has significant effect on their relevant properties (e.g. chemical composition, mechanical
properties, ballistic properties, etc.). The changes of relevant properties limit the safe and reliable service life of DB
rocket propellants. This is the reason why numerous research efforts are devoted to finding out reliable methods to measure
the changes caused by ageing, to assess the quality at a given moment of time, and to predict remaining life-time of DB rocket
In this work we studied dynamic mechanical properties of DB rocket propellant artificially aged at elevated temperatures,
in order to detect and quantify changes in dynamic mechanical properties caused by the ageing. Dynamic mechanical properties
were studied using dynamic mechanical analyser (DMA).
The results obtained have shown that the ageing causes significant changes of DMA curve’s shape and positions. These changes
are quantified by following some characteristic points on DMA curves (e.g. glass transition temperatures; storage modulus,
loss modulus and tanδ at characteristic temperatures, etc.). It has been found out that the most sensitive parameters to the
ageing process are: storage modulus at viscoelastic and softening region, peak width and height on loss modulus curve, glass
transition and softening temperature, and tanδ at viscoelastic region.
The paper deals with results of thermal analysis of low-alloyed chromium-molybdenum steel. The methods of analysis were dilatometry,
differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The Ac1 and Ac3 temperatures of the steel samples measured by dilatometry and DTA during the heating period were in good agreement. Generated
by cooling a martensitic structure first became apparent at 503 K. Tempering of the as-quenched samples showed the presence
of the second tempering stage in the region between 473 and 573 K. At that stage heat capacity decreased from 0.48 to 0.32
J g-1 K-1, as a result of conversion of transition carbide due to heat consumption. After normalization of the as-quenched samples
the heat capacity values were restored to between 0.42 and 0.47 J g-1 K-1 in the temperature range from 373 to 673 K.
Authors:M. Gojić, J. Črnko, M. Sućeska, and M. Rajić
Heat treatment of pipes was performed under industrial conditions at 580C in a dry protective gas containing a CO2–CO–H2–N2 mixture. A commercial adsorbent (733 kg) used for production ofthe gas removed 52.7 l of water in five h and 22.5 min. During
the annealing of pipesoxidation and decarburization were not observed. The results were confirmed bymetallographic analysis.
The values of enthalpy of water desorption (36.4–40.5 kJ mol–1) obtained by DSC and TG measurements were close to those of water evaporation(44.1 kJ mol–1). This suggests that the bonds between the water molecules andadsorbents were not of chemical but of physical nature.