Effect of Product Conductivity on Field‐Activated Combustion Synthesis

Abstract

Experimental and modeling results on the field‐activated combustion synthesis (FACS) of Nb5Si3 are reported. In the absence of an electric field and without reactant preheating, Nb5Si3 cannot be prepared by self‐propagating high‐temperature synthesis (SHS). Under the influence of a field a self‐sustaining combustion wave is established whose rate of propagation decreases with traveled distance. For relatively low field values, the wave propagation mode changes from a continuous (smooth) to a spin mode. The product of synthesis depends on the mode of propagation. Synthesis during continuous wave propagation results in the formation of Nb5Si3, primarily in the α‐modification. In contrast, when the wave propagates in a spin mode, the product is NbSi2 with unreacted niobium. The present observations demonstrate a case where the field effect is not localized, as was the case in previous studies. The difference in behavior is attributed to differences in the electrical conductivities of the product phases.