Molybdenum silicide uses

Physical and chemical properties of molybdenum silicide

Molybdenum disilicide is a molybdenum silicon compound, also known as molybdenum silicide, is a gray ceramic powder.

Chemical formula: MoSi2

Molecular weight: 152.11

Density: 6.3g/cm3

Coefficient of thermal expansion: 5.1×10-6/degree Celsius

Resistivity: 21×10-6Ω.cm

Microhardness: 1200kg/mm2.

Since the radii of the two atoms do not differ much, and the electronegativity is relatively close, it has similar properties to metals and ceramics. The melting point is as high as 2030°C, and it is conductive, and a silicon dioxide passivation layer can be formed on the surface to prevent further oxidation at high temperatures. Its appearance is gray metallic, derived from its square α-type crystal structure, which also has a hexagonal shape, but unstable β-modified crystal structure. Insoluble in most acids, but soluble in nitric acid and hydrofluoric acid. 

Molybdenum silicide has high melting point, low density, good thermal conductivity and good electrical conductivity as well as excellent high temperature oxidation resistance, high elastic modulus, low thermal expansion coefficient, high strength, chemical corrosion resistance and good thermal shock resistance, is widely used in high-temperature heating element materials and high-temperature anti-oxidation coating materials, and is also a high-temperature structural material and wear-resistant material with great development potential.

Preparation of molybdenum silicide

With the rapid development of powder metallurgy technology and material technology. The preparation process of molybdenum silicide has also made significant progress. On the basis of traditional arc melting, casting and powder pressing and catalyzing processes, in the late 1980s, self-propagating high-temperature synthesis (SHS), mechanical alloying (MA), hot pressing Technologies such as (HP) have achieved rapid development, and they overcome the shortcomings of the traditional process of molybdenum silicide, such as high melting point, difficult synthesis, and easy oxidation of materials during the synthesis process. In the past few years, a new process of spark plasma sintering has appeared, and new expansions have also appeared in SHS and MA. However, these methods all use molybdenum powder and silicon powder as raw materials, and because the price of molybdenum powder is relatively high, the cost of raw materials is relatively high. 

Another method is to use MoS2 powder and Si powder as a low-cost method for preparing molybdenum disilicide. The preparation method uses MoS2 powder and Si powder as raw materials, mixes them evenly, roasts them in a furnace, and obtains molybdenum silicide products after cooling. Adopting this scheme has the following beneficial effects:

(1) Using MoS2 powder as a raw material can effectively utilize the rich MoS2 resources in my country and reduce the production cost of preparing molybdenum silicide; 

(2) The process is shortened, resources are saved, and production costs are reduced; (3) The prepared molybdenum silicide has high purity and less impurities through the control of the proportion of raw materials, the selection of roasting process, and the reasonable selection of other process parameters.

Application of molybdenum silicide

Molybdenum disilicide is used in high-temperature anti-oxidation coating materials, electric heating elements, integrated electrode films, structural materials, composite material reinforcement materials, wear-resistant materials, structural ceramic connection materials and other fields. Distributed in the following industries:

1. Energy and chemical industry: electric heating elements, high-temperature heat exchangers for atomic reactor devices, gas burners, high-temperature thermocouples and their protective tubes, melting vessel crucibles (for melting sodium, lithium, lead, bismuth, tin and others Metal).

2. Microelectronics industry: MoSi2 and some other refractory metal silicides Ti5Si3, WSi2, TaSi2, etc. are important candidate materials for gate and interconnect films of large-scale integrated circuits.

3. Aerospace industry: As a kind of high-temperature anti-oxidation coating, it has been extensively and deeply researched and applied. Especially as a material for turbine engine components such as blades, impellers, combustors, tail nozzles and seals.

4. Automobile industry: turbocharger rotor, valve body, spark plug and engine parts of automobile turbine engine.