Magnesiothermal synthesis and consolidation of multicomponent powder ceramics in the Zr–Si–Mo–B system

Abstract

The work aims to obtain composite powder ceramics based on ZrB2–ZrSi2–MoSi2 by the self-propagating high-temperature synthesis (SHS) according to the scheme of magnesium thermal reduction from oxide raw materials, as well as its subsequent consolidation by hot pressing (HP). The combustion of the reaction mixtures is characterized by rather high adiabatic temperatures in the range of 2060 to 2120 K and burning rates in the range of 8,3 to 9,4 g/s. The yield of the end product with magnesiothermal reduction is 34–38 %. The resulting powder contains 13–47 % ZrB2, 21–70 % ZrSi2, 2–32 % ZrSi, and 10–18 % MoSi2 depending on the composition of the initial reaction mixture. It is characterized by high structural homogeneity and consists of composite particles of polyhedral shape with an average about 8 microns in size. The structure of ceramics consolidated by the HP method from SHS powder is homogeneous and includes ZrB2 needle grains distributed in a ZrSi2 matrix, MoSi2 inclusions of various morphology and ZrSiO4 silicate, distributed along the grain boundaries of ZrSi2. The samples obtained by HP are characterized by a high degree of homogeneity of the chemical composition and a residual porosity of 2,5–7,4 %.