The results of experimental investigation of the influence of 0.1÷5.0 mass percent of K2CO3 and KCl additives on the dispersion of combustion products, which were obtained by the combustion of an Al gas suspension in a laminar diffusion flame, are presented. The extreme dependence between the average particle size of Al2O3 and the additive concentration () was experimentally observed. At the K2CO3 additive concentration over 0.5%, the increase in the average particle size of Al2O3 (10 ∼ 50 nm for = 5%) was observed. It is shown that a change in the character of dependence between the Al2O3 average particle size and the concentration of low ionizing additives is due to the interaction between the dust and the ion subsystems of the combustion product plasma in the flame combustion zone. The theoretical calculation of the ion concentration in the system, at which the ion drag force is comparable to the Coulomb force, was done. K e y w o r d s: aluminum flame, gas-dispersion synthesis, low ionizing additives, combustion product dispersion, coagulation rate, dusty plasma.

Terbium-doped AlO samples were obtained by gas-dispersed synthesis. It was shown that the resulting powders, with particle sizes of 10-70 nm, consist of a mixture of transition aluminas, among which the δ -polymorph is dominant. The luminescence properties of AlO:Tb have been studied upon excitation in the UV-visible range of the spectrum. It was found that Tb ions cause several groups of inhomogeneously broadened emission bands in the range of 470-640 nm, which are characteristic for disordered materials. In addition, the emission spectra contain a broad band at about 450 nm and several narrower ones in the 680-720 nm region. These features are attributed to surface defects and impurity Cr ions occupying Al octahedral positions, respectively.

No abstract

No abstract

This paper discusses the fl ame ionization effect on the combustion processes in gaseous suspensions of the dispersed fuels. It is shown that the two-phase fl ame ionization affects almost all the processes of the fuel conversion -kinetics of the dispersed fuel combustion, processes of the interphase heat and mass transfer, processes of the nucleation and coagulation in the fl ame, formation of nanoscale products of the metal particles combustion. It is shown that the electrostatic interaction between the charged nanoparticles and ions or polar molecules in the gaseous phase leads to the appearance of molecular "pumps" that can signifi cantly change the kinetics of the heterogeneous chemical reactions and the heat exchange between particles and gas. The infl uence of the thermal ionization of the fl ame on the nucleation mechanism and rate in gas-dispersed systems is discussed. The possibility of a barrier-free homogenous and heterogeneous nucleation in the dusty fl ame of metallic particles is shown. The effect of electrostatic and polarizing interactions of ions and molecules on the kinetics of the ternary gas-phase reactions is considered. The infl uence of the monodisperse aerosol ionization degree on the kinetics of its coagulation is analyzed. It is concluded that electrostatic interaction between the particles strongly affects the inhibition of the coagulation process in gas-phase combustion products and the possibility of very fast (explosive) charged particle coagulation of monodisperse aerosols. The possibility of the targeted size of metal oxides nanoparticles control, controlled ionizing of dusty fl ames and the role of ion particle entrainment, the dependency of their size of the fl ame ionization degree are discussed. Some effects arising in complex plasma of condensed combustion products under its own electric fi elds in fl ames, also when the burning dust is entrained into a constant electric fi eld and their practical applications for diagnosis are considered.