Shock synthesis of silicides; 2: Thermodynamics and kinetics

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

DOI:https://doi.org/10.1016/0956-7151(94)90269-0· OSTI ID:5150208

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

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

A thermodynamic and kinetic analysis of shock-induced reactions in the (Nb or Mo)-Si systems provides a framework for the extraordinarily high reaction rates and a quantitative interpretation of the experimental results obtained in Part 1. The thermodynamic analysis is conducted by adding the heat of reaction to the shock energy; increases in shock pressure, temperature, and velocity are predicted. At the particle level, melting at the silicon-metal interface is found to be a necessary condition for the initiation of reaction; heat conduction calculations enable the prediction of a critical molten (Si) region size for which the heat generated through the reaction exceeds the heat lost to the unreacted regions. The calculation of melt fraction (of Si) as a function of shock energy for the initiation of shock-induced reaction. At the local level, the reaction kinetics can be rationalized through the production of a liquid-phase reaction product (NbSi[sub 2]), the formation of spherical nodules of this product through interfacial tension to melt niobium along the interface which facilitates both the expulsion of the NbSi[sub 2] nodules into the liquid Si, and the generation of fresh Nb interface for further reaction. In addition, the dissolved Nb enriches the surrounding Si liquid, promoting more NbSi[sub 2] reaction and formation.

• OSTI ID: 5150208
• Journal Information: Acta Metallurgica et Materialia; (United States), Vol. 42:3; ISSN 0956-7151
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
MOLYBDENUM SILICIDES
REACTION KINETICS
THERMODYNAMIC PROPERTIES
NIOBIUM SILICIDES
QUANTITATIVE CHEMICAL ANALYSIS
SHOCK HEATING
CHEMICAL ANALYSIS
HEATING
KINETICS
MOLYBDENUM COMPOUNDS
NIOBIUM COMPOUNDS
PHYSICAL PROPERTIES
PLASMA HEATING
REFRACTORY METAL COMPOUNDS
SILICIDES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
400201 - Chemical & Physicochemical Properties