Shock synthesis and synthesis-assisted shock consolidation of suicides

Abstract

Shock-induced chemical synthesis and synthesis-assisted consolidation of high-temperature materials (suicides) were investigated. Niobium, molybdenum, and titanium powders mixed with silicon powders were chosen as reactant materials for shock-induced synthesis of silicides. In parallel experiments, these reactant materials were also respectively mixed with inert intermetallic compound powders of NbSi₂, MoSi₂, and Ti₅Si₃ in different proportions and were shock consolidated. Shock processing was carried out using a modification of the experimental set-up developed by Sawaoka and Akashi. The shock waves were generated in the materials by the impact of a flyer plate at a velocity of 2 km sec⁻¹. An explosive plane-wave generator was used to initiate the main explosive charge to accelerate the flyer plate. The passage of shock waves of sufficient pressure and temperature induced a highly exothermic and self-sustaining reaction between reactant materials. The shock-synthesized intermetallic compounds and the heat of reaction enhanced bonding between inert matrix materials. The proportion of reactant powder mixtures blended with inert intermetallic materials plays a very important role in the synthesis-assisted consolidation process. Characterization of compacts was done by optical microscopy, scanning electron microscopy, and X-ray diffraction. A preliminary analysis of shock-induced chemical reactions is conducted; it predicts a 30% increase in shock pressure and shock-wave velocity over those in unreacted powders. For shock synthesis, the profuse formation of voids indicates that melting of the material occurred; in contrast, unreacted regions did not exhibit porosity.