Suchergebnisse

The differential scanning calorimetry becomes nowadays an easily available technique able to provide experimental data which can be used to seek for possible correlations with molecular properties. Among these data, the entropy and enthalpy for different phase transition like melting or decomposition of various related compounds proved to be very fruitful. In the present paper, the enthalpy and entropy data for different phase transitions and decomposition of two classes of related energetic compounds (13 based on phenoxazone derivatives and 6 on substituted (E)-3-(azulen-1-yldiazenyl)-1,2,5-oxadiazole) are analyzed and presented. The heats of decomposition seem to present no correlations as functions of molecular mass or melting temperature, while the heats of melting and the temperatures of melting present a fair correlation as a function of the molecular mass or melting temperature. A particularly good correlation is provided by the entropy of melting as a function of the enthalpy of melting, in accord with their significance for a process at equilibrium.

The presence of a flammable gas in a combustible dust cloud significantly modifies its explosivity parameters. Thus, a hybrid mixture can become flammable even when both the dust-air and gas-air binary mixtures are under the corresponding lower explosion limits. The pressure-time histories of hybrid mixtures formed by coal dust, methane and air at different concentrations, at 1 bar initial pressure and normal temperature, were studied using the standard 20 L spherical explosion vessel and 5kJ chemical igniters or 10 J permanent sparks. From the early stages of the pressure-time history, when the pressure increase is equal to or less than the initial pressure, the normal burning velocities were evaluated and discussed.