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

摘要

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 mu m. 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%.