|M.Sc Student||Vasilkovsky Aviv|
|Subject||Comparison of Methods for Calculating Thermodynamic|
Functions of Chemical Reactions of Energetic
|Department||Department of Chemical Engineering||Supervisor||Professor Emeritus Abraham Marmur|
|Full Thesis text|
Differences in the performance and the character of energetic materials reactions such as combustion of propellants and explosion reactions are usually related and explained by kinetics, as differences between their rates of reactions cause differences between their gas product release times and therefore between their obtained products pressures.
However thermodynamic parameters, as a driving force for reactions, may also explain these differences and make a tool for categorization of energetic reactions, which matches their categorization by character and performance.
Although enthalpy values data of different materials at standard conditions are common in the literature, entropy data (or, alternatively, Gibbs free energy data) are not very common, and one needs to make an effort in order to obtain them. Previous works were made, in which different methods, experimental, computational and semi-empirical, were developed and/or used for obtaining entropy values of different groups of materials. These data and methods were used in this work for the calculations of different types of ideal complete energetic reactions' entropy values and enthalpy values, and based on both also their Gibbs free energy values at both, standard isothermal conditions and adiabatic isobaric conditions.
The obtained thermodynamic values were then compared for both types of conditions in order to examine if different types of energetic reactions can be categorized by them. It was found that the analyzed energetic reactions in this work are divided into two major groups by most of their thermodynamic values - different kinds of combustion reactions, either internal combustion engine fuels or rocket propellants, and unimolecular decomposition reactions, either explosion or propulsion reactions. The first group presents higher enthalpy and free energy values at standard isothermal conditions, whereas the latter presents higher ratios of entropy to the free energy of reaction. At adiabatic isobaric reactions a rough but not clear division into these two groups was obtained by the entropy values of reaction per mass unit.
However, at both conditions, the analyzed three explosion reactions and two hypergolic propulsion reactions show either the highest molar entropy values (explosion reactions) or both higher molar entropy values and the highest mass entropy values (hypergolic reactions). Considering that the reactions of both these types occur rapidly, as explosion reactions react immediately with a rapid release of gas, and hypergolic reactions react immediately with reactants contact with the release of gas, this favorability of their entropy values over other reactions of combustion and propulsion types, reflects their unique character. This unique behavior of these types of reactions seems to be caused by their reactants nitro, NO3, and nitrate, NO2 groups, which doesn't exist in the other analyzed energetic reactants. Still, mass entropy values favorability of explosion reactions is not shown, probably due to their significantly higher molar mass comparing to other energetic reactions analyzed here.