Macrostructure imaging for SHS product METAL1–METAL2–NITROGEN as reflection of some combustion waves and aftercombustion of gaseous products

Abstract

The paper presents research of formation of a macrostructure at self propagation high temperature synthesis for systems METAL1–METAL2–NITROGEN (where METAL1–Ti, Al, and METAL2–Mo, Cr, Co, Al) in the “L-S” temperatures of equilibrium diagram. Supervision of bright, high temperature trajectories in the course of combustion, and macrostructure features shows existence of a set of waves of combustion which differ time delay of emergence or an arrangement in space. Studying of surface of samples found set of openings – the craters, formed from an exit of burning streams of gas (torches). The gaseous burning streams are created by intermediate products which react with nitrogen just after passing of stationary wave. The types of channels are schematically presented at various sections of the synthesized product. The volume macrostructure in the burned samples are approximately restored by character of channels. Studying thermogram during combustion found a nonclassical profile which differs from standard by existence of several "humps" which correspond to passing of several combustion waves with different sequence of touch of these waves to the thermocouple. At first, the first combustion wave passing with the expanding and narrowing front is fixed, and then the profile from combustion of internal part of a sample is recorded. There can't be one steady wave with the flat front at catalytic combustion because of beginnings and disintegration of intermediate nitrides of "inert" metal which arise at strong thermodynamic instability which is caused by that a temperature interval, emergence and disintegration of intermediate connection the very narrow. It is shown that when combustion in nitrogen under pressure, always at first the spiral "spin" wave in very thin blanket where there is an interaction with external readily available nitrogen "runs".