To gain further insight into the nature of the liquid-flame structure (LFS), which is characteristic of compressed solid mixtures, containing tetrazole (64 wt%) and sodium tetrazolate monohydrate, a number of physical and chemical characteristics of the liquid flame was studied. The temperature distribution on the surface of the LFS and the temperature profile in a combustion wave were investigated using optical pyrometry, as well as thermocouples and electrochemical methods. The LFS is found to be characterized by highly uniform heat radiation; the temperature on the LFS surface varied from 940 to 1000 K. The small LFSs (up to 5-6 mm in diameter) are capable of voluminous radiation, while the LFSs of larger sizes irradiate as hollow envelopes, with a wall thickness of ~1-2 mm. The temperature and electrochemical measurements in the combustion wave indicate that the LFS represents a spheroidal formation, having to a considerable extent a hollow envelope of melt characterized by a relatively even temperature distribution inside the LFS, the temperature being 1050-1250 K, depending on the LFS size. The chemical compositions of the gaseous and condensed products of the thermal decomposition and combustion of pure tetrazole, sodium tetrazolate, and a mixture of them were studied by 1H NMR, IR, mass spectrometry, gas chromatography, elemental, and x-ray analyses. The data obtained allow one to identify the chemical reactions in the liquid flame. The thermal decomposition of sodium tetrazolate results in the formation of chemically stable sodium acid cyanamide; this is the basic reaction proceeding in the liquid flame. The fragmentation of the tetrazole leads to cyanamide polymer; partial decomposition of sodium tetrazolate proceeds in the melt layer below the liquid flame. Both reactions are accompanied by the evolution of considerable heat and gaseous nitrogen. An analysis of all the measurements suggests that the necessary conditions for an LFS and its development on combustion are a large amount of nitrogen in the initial substances, which must have considerable thermal stability, along with high positive enthalpies of formation, together with the presence of definite chemical fragments and ions of alkali metals in molecules of at least one of the components. In accordance with these criteria, mixtures of tetrazolates and azides of alkali metals with tetrazole, 1,2,3-triazole, 1.2,4-triazole, guanidine, and some of their derivatives are shown to be capable of forming an LFS on combustion.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Fuel Technology
- Energy Engineering and Power Technology
- Physics and Astronomy(all)