Si<SUB>3</SUB>N<SUB>4</SUB>粉とFe-Ni合金粉との高温反応機構

Abstract

The kinetics and the mechanism of the reaction between Si3N4 and Fe-Ni alloy have been investigated in N2 or Ar atmospheres at temperatures from 1123 to 1573 K. Using a Si3N4/Fe-46.9 mass%Ni alloy powder mixture, the reaction rates were determined with a thermobalance.A characteristic feature of TG curves was the incubation period that preceded the mass loss. The incubation period was decreased with increasing temperature. The mass loss was larger in Ar atmosphere than in N2 atmosphere. A prolonged heating resulted in establishment of equilibrium in N2 atmosphere. The reaction continued for 72 ks in Ar atmosphere.The initial rate followed a linear rate law. Below 1323 K, the rate constant was less in N2 atmosphere than in Ar atmosphere. The activation energies were 348 kJ·mol−1 in N2 atmosphere and 304 kJ·mol−1 in Ar atmosphere. The reaction rate was controlled by the interfacial reaction. At 1373 K and above the rate constant in N2 atmosphere was identical to that in Ar atmosphere and the activation energy was 98 kJ·mol−1. The rate-determining step was considered to be the gaseous diffusion through the interparticle pores.When the alloy particles were covered with the reaction layer, the kinetics was described by the parabolic rate law. The rate constant was independent of the atmosphere. The activation energy was 337 kJ·mol−1. The rate-controlling step was the solid-state diffusion through the reaction layer.