Aluminothermic combustion in Аl–ZrSiO4–N2 and Al–SiO2–N2 systems at high nitrogen pressure

Abstract

This paper contains study results of the nitride-containing composites formation in pressed samples of  АІ–ZrSiO₄–N₂ and Al–SiO₂–N₂ systems in the high pressure reactor with various nitrogen pressure values. Zir-conium concentrate with 97 % ZrSiO₄ produced by Obukhov Mining and Smelting Plant (North Kazakhstan region, Kazakhstan) has been used as a zirconium-containing feedstock. To obtain composites with good technical properties and to increase reactionary capacity of the studied systems, the SH-synthesis has been carried out con-sidering a wide range of the components ratio. Nitrogen pressure in the reactor varies from 5 to 20 atmospheres. The effect of the nitrogen pressure on the combustion temperature, durability and change in the synthesized composite mass has been determined. Electron microscopy of the SHS products and energy dispersive element analysis allowed for establishing rachislike structures’ reinforcing role in the composite matrix. Performed X-ray phase analysis allowed for identification of the basic SHS products that form both the refractory and mechanical properties of the composite materials. There have also been determined formation conditions of the nitride-containing composites with an aluminum oxynitride matrix, and silicon and zirconium nitrides as well as aluminum silicides used as reinforcing structural elements. Undertaken study has demonstrated that the zircon based aluminothermic systems in the SHS process using the nitrogen atmosphere lead to production of the nitride-containing composite materials with high refractory and physical and mechanical properties.