Molybdenum disilicide

product information:
Name: Molybdenum Disilicide
Purity: ≥99.5 single phase


Particle size: D50: 5~10 microns


Melting point: 2030°C


Density: 6.24g/cm3


Properties: gray powder

 

Uses: Molybdenum disilicide is used as a structural material for high-temperature parts of aviation and automobile gas turbines, gas burner nozzles, and high-temperature filters. Silicon molybdenum rods, heating elements, integrated circuits, high temperature anti-oxidation coatings, capacitor glass electrodes, etc.

Molybdenumdisilicide (MoSi2) is a silicon compound of molybdenum,


Since the radii of the two types of atoms are not much different and the electronegativity is relatively close, they have a similarity to


The nature of metals and ceramics. The melting point is as high as 2030°C, it is conductive and has surface energy at high temperatures.


A passivation layer of silicon dioxide is formed to prevent further oxidation, and its appearance is gray metal color,


Derived from its tetragonal a-type crystal structure, there is also a hexagonal but unstable β-modified crystal structure. Insoluble in most acids, but soluble in nitric acid and hydrofluoric acid.


MoSi2 is an intermediate phase with the highest silicon content in the Mo-Si binary alloy system, which has a fixed composition


Dalton type intermetallic compound. With the dual characteristics of metal and ceramics, it is a kind of excellent performance


High-temperature materials. Very good high temperature oxidation resistance, the oxidation resistance temperature is as high as 1600 °C, which is equivalent to SiC; has a moderate density (6.24g/cm3); a low thermal expansion coefficient (8.1X10-6K-1);


Good electrical and thermal conductivity; high brittle-to-ductile transition temperature (1000°C) or less has ceramic-like hardness and brittleness. It is metal-like soft plasticity above 1000"C. MoSi should be used as heating elements, integrated circuits,


High temperature anti-oxidation coating and high temperature structural materials.


In MoSi2, molybdenum and silicon are connected by metal bonds, and silicon and silicon are connected by covalent bonds.


Molybdenum disilicide is a gray tetragonal crystal. Insoluble in ordinary mineral acids (including aqua regia),


But it is soluble in a mixed acid of nitric acid and hydrofluoric acid, has good high temperature oxidation resistance, and can be used as a heating element working in high temperature (<1700°C) oxidizing atmosphere.


In an oxidizing atmosphere, a protective film is formed on the surface of the dense quartz glass (Si02) that burns at a high temperature.


To prevent continuous oxidation of molybdenum disilicide. When the temperature of the heating element is higher than 1700°C, a protective film of SiO2 is formed, which fuses at a melting point of 1710°C and fuses with Si02 into a molten drop. Due to the movement of its surface extension,


Therefore lose its protective ability. Under the action of an oxidant, when the element is used continuously,


Form a protective film again. It should be noted that due to the strong oxidation at low temperatures,


This element cannot be used for a long time in the temperature environment of 400-700C.
Molybdenum disilicide is used in high-temperature oxidation-resistant coating materials, electric heating elements, and integrated electrode films. Structural materials, reinforcing agents for composite materials, wear-resistant materials, and connecting materials for structural ceramics are distributed in the following industries:


1) Energy and chemical industry: electric heating elements, high temperature heat exchangers of atomic reactor devices,


Gas burner, high-temperature thermocouple and its protection tube, melting vessel crucible (used to smelt sodium, lithium, lead, bismuth, tin and other metals).


2) Microelectronics industry: MoSi2 and others-some refractory metal silicides Ti5Si3, WSi2. TaSi2, etc. are important candidate materials for large-scale integrated circuit gate and interconnection film.


3) Aerospace industry: As a high-temperature anti-oxidation coating material, it has been extensively and deeply researched and applied. Especially as turbine engine components, such as blades, impellers, burners, nozzles and sealing devices, molybdenum disilicide is used as a structural material for high-temperature parts of aviation and automobile gas turbines, gas burners, nozzles, and high-temperature filters And spark plugs have become the latest hot spot in the research of intermetallic compound structural materials. The biggest obstacle to this application is its high room temperature brittleness and low high temperature strength. Therefore, molybdenum disilicide is low


Temperature toughening and high temperature reinforcement: it is the key technology for its practical application as a structural material. Research in this area shows that alloying and compounding are effective means to improve the room temperature toughness and high temperature strength of molybdenum disilicide. The components generally used for alloying of molybdenum disilicide are only those few silicides that have the same or similar crystal structure as molybdenum disilicide, such as WSi2.NbSi2, CoSi2, Mo5Si3 and Ti5Si3, among which the most ideal is WSi2.


However, alloying with WSi2 will obviously lose the advantages of molybdenum disilicide in terms of specific gravity, and its application will be limited. Practice has proved that molybdenum disilicide has good chemical stability and capacitance with almost all ceramic reinforcements (such as SiC, TiC, Zr02, A1203, TiB2, etc.). Therefore, compounding, that is, preparing molybdenum disilicide-based composite materials is the most effective way to improve the mechanical properties of molybdenum disilicide.