Micro-scale simulation of dynamic compaction of oxide and metal powder mixture

Many features of the dynamic compaction of powders are potentially favorable for use in processing high T(sub c) oxide superconductors. Conventional sintering methods tend to produce unwanted impurities, voids, and oxygen-deficient grain boundaries and have, thus, failed to form bulk oxide superconductors with high critical current. One proposed approach for a dynamic process is to compress a mixture of high purity single crystallite particles and fine silver particles. Computer modeling of dynamic compaction has thus far been limited to bulk simulation of the process by continuum mechanics codes. Results of compaction experiments are not reliably predicted with such techniques because the micro-scale dynamics of powder compaction are only modeled by phenomenological approximation. A micro-scale simulation technique was developed and applied to computer models similar to those of molecular dynamics, which were originally designed to simulate the flow behavior of inelastic, frictional particles. In this method, the oxide grain is represented by a nearly elastic sphere while an individual silver grain is modeled by an aggregate of effective inelastic-frictional particles bound by a prescribed interparticle force. The first 2-D simulation results for a simple configuration (a single aggregate silver grain crushed between two nearly elastic ceramic spheres) are compared with the continuum calculations for the same configuration. This micro-scale simulation technique can be extended to study an assembly of dissimilar grains in 3-D space.