What is molybdenum disilicide and how can it be used?
The tetragonal structure is found in the molybdenum-disilicide crystal (MoSi2). It is an intermediate phase containing the highest silicon content within the Mo-Si binary alloy system. It is a Dalton intermetallic compounds with a fixed composition. It is grayish with metallic luster. It has excellent electrical and thermal conductivity, excellent mechanical property and high temperature resistance to oxidation. It is more efficient than silicon carbide and can be used as an heating element. It was originally used to protect a metal substrate’s surface from corrosion and high temperatures. It was initially used to coat gas turbine parts, the jet engine combustion chambers, as well as missile combustion chambers. Today, molybdenum is used in the manufacture of high-temperature heating elements as well as thermocouple protection tubes.
Molybdenum disilicide property:
Crystallographic properties Pure molybdenum is stable and does not undergo any phase changes once it reaches its melting point. Changes in crystallographic properties will not affect the temperature rise or fall within the upper limits of its temperature range.
Thermodynamic characteristics: melting point above 2030degC, high temperature conductivity (similarly to SiO), small thermal expansion coefficient. These characteristics are required for the production and use of thermocouple protection tube or high-temperature heating element.
Electromagnetic properties include low resistivity (2×10-5O*cm), high electricity rate, and good conductivity. This material is great for making heating elements and thermocouple thermoelectrodes.
Mechanical properties: The strength of the material is not lower than general metal materials or some oxide materials (such Al2O3). Also, the hardness and compressive strengths are higher than metals. It has poor impact toughness which is a disadvantage to metals. To make cermet, it is necessary to add a small amount metal bond in the actual production process.
Chemical properties: The chemical status is acidic. It is insoluble at room temperature with all acids and alkalis. MoSi2, other than oxide ceramics is the most stable of all refractory chemicals. The molybdenum’s solubility in silicon is approximately 1% (1800degC), which determines the MoSi2 oxidation stability at below 1700degC.
Molybdenum diicide by itself is not highly resistant to oxidation. However at 1300-1600degC, an extremely thin, dense, and glassy silicon dioxide protective layer is formed to stop further oxidation. MoSi2 is stable in oxidizing media and can also be used at high temperatures in reducing (neutral, inert) or strong corrosive atmospherics. In N2, CO2, and SO2 media, for example, the maximum temperature can reach 1600.
Uses for molybdenum diilicide
The most popular silicide product, with the greatest industrial production, is molybdenum, which has its main products being high-temperature heat elements and thermocouple protective tubes.
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