Magnesiothermal Synthesis and Consolidation of the Multicomponent Powder Ceramics in the Zr–Si–Mo–B System

Resumo

This work is devoted to the fabrication of ZrB₂–ZrSi₂–MoSi₂-based composite powder ceramics by self-propagating high-temperature synthesis (SHS) according to the scheme of magnesium thermal reduction from oxide feedstock and its subsequent hot-pressing (HP) consolidation. The combustion of reaction mixtures has rather high adiabatic temperatures in a range of 2060–2120 K and burning rates in a range of 8.3–9.4 g/s. The end product yield of the 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; has high structural homogeneity; and consists of composite polyhedral particles with an average size on the order of 8 μm. The structure of ceramics consolidated by HP from the SHS powder is homogeneous and includes needle ZrB₂ grains distributed in the ZrSi₂ matrix, MoSi₂ inclusions of various morphologies, and inclusions of ZrSiO₄ silicate distributed over the ZrSi₂ grain boundaries. The HP-formed samples have a high degree of homogeneity of the chemical composition and residual porosity of 2.5–7.4%.