Shock-Induced and Shock-Assisted Reaction Synthesis of Materials.
Abstract
The beneficial effects of shock-compression of powders and solid-state chemical reactions were utilized to synthesize Ti-Si and Ti-A1 intermetallics, Ti-B and Ti-C ceramics, and Ti-Si:Ti-A1 composites. Time-resolved stress measurements provided evidence for shock-initiation of reactions in 53% dense Ti-Si powders, based on increased wave speed and volume expansion (due to formation of intermetallic product with higher elastic modulus) measured at shock-pressures exceeding 1.5 GPa. These measurements combined with controlled recovery experiments, revealed the effect of powder morphology and the influence of property differential between reactants on the reaction threshold, demonstrating the dominant role of mechanochemical processes on shock-initiation of chemical reactions. Shock-synthesis was applied to form beta-phase C3N4 compound using cyano group precursors mixed with azides and iodides. The post-shock reaction behavior of shock-densified Ti-C and Ti-Si powder mixtures was observed to reveal enhanced kinetics with activation energies for diffusion of reactants being lowered by four-to-six times. It was also demonstrated that the shock-activated dense-packed state of powders (elemental reactants or compounds) can be used as an intermediate step for fabrication of net-shaped TiC ceramics, nanocrystalline Ti5Si3 intermetallics, and compositionally-graded composites.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 24, 1997
- Accession Number
- ADA332794
Entities
People
- Jong-heon Lee
- Naresh Thadhani
- Partrick Counihan
- Shantanu Namjoshi
- Tyrus Royal
Organizations
- Georgia Tech