Chemical Properties
Dark-gray, crystalline powder. Not affected by air upto 1648C. Not attacked by most inorganic acidsincluding aqua regia, but very soluble in hydrofluo-ric and nitric acids. Has high stress-rupture strength.
Physical properties
The compound is thermally
stable in air up to 1000°C.
Corrosion resistant to molten
metals such as Zn, Pd, Ag, Bi,
and Rb. Corroded by liquid
metals Mg, Al, Si, V, Cr, Mn, Fe,
Ni, Cu, Mo, and Ce.
Application
Molybdenum disilicide (MoSi2) is a ceramic material with excellent high-temperature oxidation resistance and corrosion resistance. It can be used as a substrate material in the fabrication of thermophotovoltaics. MoSi2 can also be used as a protective coating on carbon-carbon composites for potential applications in aerospace and thermonuclear fusion.
Preparation
Molybdenum disilicide is a promising candidate material for high temperature structural applications. Molybdenum silicide is produced in much the same way as ferromolybdenum. A typical mix for the production of molybdenum silicide is 1,000pounds of molybdenum in oxide, 259 pounds of aluminum, 760 pounds of 90-percent ferrosilicon, 166 pounds of 50-percent ferro-silicon, 160 pounds of lime, and 50 pounds of high-grade fluorspar.
General Description
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Flammability and Explosibility
Notclassified
Industrial uses
High-temperature silicides are a new class of materials with potential applications in the temperature range 1200 to 1600 C.The silicide that seems most promising is molybdenum disilicide (MoSi2) because of its high melting temperature (2200 C) and excellent oxidation resistance. It has a tetragonal crystal structure. A major problem is its absence of ductility at temperatures up to 1000 C. It also has poor high-temperature strength due to the presence of a grain boundary silicon-rich phase that may become viscous at very high temperatures. Recent research has shown that this problem may be solved by the addition of carbon to the material.
