A study on combustion behaviour of carbon-sulphur-sodium nitrate mixtures

Abstract

The effect of substitution of KNO3 by NaNO3 in black powder has been studied by DSC, TG/DTG and FFIR emission spectroscopy. Unlike KNO3, there is no visible exothermic reaction between S and NaNO3, immediately after the melting of NaNO3. Instead a minor exothermic reaction is observed at higher temperature between melted NaNO3 and adsorbed S on carbon. However, there is an increase in such reaction, when carbon black instead of charcoal is used. Infrared spectra show that CO2 and Na2SO4 are major gaseous and solid products respectively. This shows that the combustion of ternary mixtures in air is different from that in N2, with slower heating rate, in DSC or TG apparatus.The combustion of black powder [1-3] which has a traditional composition of KNO3 (75%), charcoal (15%) and S (10%) [4][5] has been studied in our laboratories. Although black powder is the oldest explosive known, it is still being used due to its peculiar properties [6]. Extensive studies [7][8][9] have been carried out and a substitute has been sought [10].Sodium nitrate is used as an oxidizer in propellants for air-augmented rocket applications [11][12] and trip flare or ignition mixtures [13].In our study the KNO3 has been substituted by NaNO3 and the combustion behaviour of mixtures containing NaNO3, carbon black/charcoal and S has been studied by DSC, TG/DTG and FTIR emission spectroscopy. ExperimentalThe sieved powdered samples of (<125/zm) NaNO3 (Aldrich Chemical