Shock synthesis of silicides; 1: Experimentation and microstructural evolution

Journal Article · Tue Mar 01 04:00:00 EST 1994 · Acta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-7151(94)90268-2· OSTI ID:5050873

Vecchio, K S; Yu, Lihsing; Meyers, M A ^[1]

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1. Univ. of California, San Diego, La Jolla (United States). Dept. of Applied Mechanics and Engineering Sciences

Niobium and molybdenum silicides were synthesized by the passage of high-amplitude shock waves through elemental powder mixtures. These shock waves were generated by planar parallel impact of explosively-accelerated flyer plates on momentum-trapped capsules containing the powders. Recovery of the specimens revealed unreacted, partially-reacted, and fully-reacted regions, in accord with shock energy levels experienced by the powder. Electron microscopy was employed to characterize the partially-and fully-reacted regions for the Mo-Si and Nb-Si systems, and revealed only equilibrium phases. Selected-area and convergent beam electron diffraction combined with X-ray microanalysis verified the crystal structure and compositions of the reacted products. Diffusion couples between Nb and Si were fabricated for the purpose of measuring static diffusion rates and determining the phases produced under non-shock condition. Comparison of these non-shock diffusion results with the shock synthesis results indicates that a new mechanism is responsible for the production of the NbSi[sub 2] and MoSi[sub 2] phases under shock compression. At the local level the reaction can be rationalized, for example in the Nb-Si system under shock compression, through the production of a liquid-phase reaction product (NbSi[sub 2]) at the Nb-particle/Si-liquid interface, the formation of spherical nodules ([approximately]2[mu]m diameter) of this product through interfacial tension, and their subsequent solidification.

• OSTI ID: 5050873
• Journal Information: Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 42:3; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
FABRICATION
MICROSTRUCTURE
MOLYBDENUM COMPOUNDS
MOLYBDENUM SILICIDES
NIOBIUM COMPOUNDS
NIOBIUM SILICIDES
PHASE STUDIES
REFRACTORY METAL COMPOUNDS
SILICIDES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS