Silicon - carbon rods and silicon - molybdenum rods are commonly - used heating elements in high - temperature electric furnaces, and they each have their own characteristics and are suitable for different application scenarios.

Characteristics of Silicon - Carbon Rods

Silicon - carbon rods are non - metallic electrothermal elements, mainly made of high - purity green hexagonal silicon carbide. Their main characteristics include:

2.Antioxidant property: Under reasonable use conditions, they can be used continuously for more than 2000 hours. Their service life is related to factors such as surface load, environmental atmosphere, heating method, and series - parallel connection mode during the use of the elements.

3.Chemical stability: They are hard and brittle in texture, have a small expansion coefficient, good resistance to rapid cooling and heating, are not easy to deform, have good chemical stability, strong acid - resistance, and do not react with strong acids.

4.Resistance characteristics: The resistance value of silicon - carbon rods changes with the change of element temperature, and it is a non - linear resistance body. From room temperature to about 900 degrees, the resistance value decreases from large to small, and above about 900 degrees, the resistance value increases from small to large.

5.Application fields: They are widely used in high - temperature fields such as electronics, magnetic materials, powder metallurgy, ceramics, glass, semiconductors, analysis and testing, scientific research, etc., and have become electro - heating elements for tunnel kilns, roller kilns, glass kilns, vacuum furnaces, muffle furnaces, smelting furnaces and various heating devices.

Characteristics of Silicon - Molybdenum Rods

Silicon - molybdenum rods are high - temperature - resistant and antioxidant resistance - heating elements made on the basis of molybdenum disilicide. Their main characteristics include:

1.High - temperature antioxidant property: When used in a high - temperature oxidative atmosphere, a bright and dense quartz (SiO₂) glass film is formed on the surface, which can protect the inner layer of the silicon - molybdenum rod from further oxidation. Therefore, silicon - molybdenum rod elements have unique high - temperature antioxidant properties. In an oxidative atmosphere, the maximum use temperature is about 1700°C.

2.Resistance characteristics: The resistivity of MoSi₂ increases rapidly with the increase of temperature. Under normal circumstances, the element resistance does not change with the length of use time. Therefore, new and old silicon - molybdenum rod electrothermal elements can be used in combination.

3.Physical and chemical properties: The density is 5.6 - 5.8g/cm³, the flexural strength is 20MPa (at 20°C), the Vickers hardness (HV) is 570kg/mm², the porosity is 0.5 - 2.0%, the water absorption rate is 0.5%, the thermal elongation rate is 4%, and the radiation coefficient is 0.7 - 0.8 (800 - 2000°C).

4.Application fields: They are widely used in fields such as metallurgy, steel - making, glass, ceramics, refractory materials, crystals, electronic components, semiconductor material research, production and manufacturing, especially for the production of high - performance precision ceramics, high - grade artificial crystals, precision - structured cermets, glass fibers, optical fibers and high - grade alloy steels.

In conclusion, silicon - carbon rods and silicon - molybdenum rods each have their own advantages in the application in high - temperature electric furnaces. When choosing, it is necessary to decide according to specific use conditions and requirements. Silicon - carbon rods are suitable for occasions with a lower temperature range and higher requirements for chemical stability, while silicon - molybdenum rods are more suitable for high - temperature and applications with higher requirements for antioxidant properties.