Diffusion paths in boron / titanium reaction systems

摘要

A new model for the diffusion controlled gasless reaction between boron and titanium particles is presented. The research focues on modeling the principal geometrical variations of small adjacent particles in close contact as well as the diffusional fluxes caused by the curvature of the connecting neck between the particles which are superimposed on the interdiffusion flux of atoms through the TiB_2 product layer. Computer calculations were used to present the time/temperature dependence of these fluxes and of the geometrical parameters. It was found that for sub-micron particles the diffusional rates induced by the neck's curvature (mainly surface diffusion) may be comparable and even larger than the regular Fick's interdiffusion flow of atoms in the TiB_2 layer, hence they can make a significant contribution to the overall diffusion rate. The model is useful for the study of B/Ti gasless reactions (e.g., in pyrotechnic mixtures) as well as for formulating the effect of boron and titanium interactions on the ignition of B/Ti aggomerates in oxidizing atmospheres.