Physicochemical Properties of Silicon Carbide Rods:

Element Texture: Hard and brittle, resistant to rapid cooling and heating, not easily deformed at high temperatures. Other physical properties are as follows:

Thermal Conductivity: 20 cal/m·h·°C

Linear Expansion Coefficient: 5×10?? (m/°C)

Chemical Properties: Good chemical stability, strong resistance to acids. Alkaline substances can erode it under high-temperature conditions.

When silicon carbide rod elements are used long-term above 1000°C, they react with oxygen and water vapor as follows:

① SiC + 2O? → SiO? + CO? ② SiC + 4H?O = SiO? + 4H? + CO?

This causes the SiO? content in the element to gradually increase, and the resistance slowly rises, leading to aging. Excessive water vapor promotes the oxidation of SiC. The H? produced by reaction ② combines with O? in the air to form H?O, creating a vicious cycle and reducing the element's lifespan. Hydrogen (H?) can reduce the mechanical strength of the element. Nitrogen (N?) can prevent SiC oxidation below 1200°C but reacts with SiC above 1350°C, causing SiC decomposition. Chlorine (Cl?) can completely decompose SiC.