High-purity graphite crucible material has excellent characteristics such as high sublimation temperature, high mechanical strength at high temperature, self-lubrication and good thermal shock resistance, but it is oxidized when it is higher than 4500C in an oxygen-containing atmosphere. In order to further improve the high temperature resistance, abrasion resistance and corrosion resistance of graphite products such as graphite plates and graphite rods, a coated graphite material has emerged, that is, a layer of metal or metal compound is coated or impregnated on the surface of graphite products. To improve the performance of graphite.
The main purpose of high-purity graphite crucible is metal melting and experiment. Because the metal has a high boiling point, other materials and ordinary ceramic crucibles will also melt, which does not meet the requirements. The melting point of graphite is 3652℃, which is ideal, and has good corrosion resistance and strength.
High-purity graphite has the advantages of low electrical resistivity, high temperature resistance, corrosion resistance, oxidation resistance, thermal shock resistance, electrical conductivity, small thermal expansion coefficient, self-lubricating, and easy precision machining.
1. High temperature resistant type: The melting point of graphite is 3850±50°C and the boiling point is 4250°C. Even with ultra-high temperature arc burning, the weight loss is small and the thermal expansion coefficient is also small. The strength of graphite increases with the increase of temperature. At 2000°C, the strength of graphite doubles.
2. Electrical and thermal conductivity: The electrical conductivity of graphite is one hundred times higher than that of general non-metallic minerals. The thermal conductivity exceeds that of metal materials such as steel, iron, and lead. The thermal conductivity decreases with increasing temperature, and even at extremely high temperatures, graphite becomes an insulator. Graphite can conduct electricity because each carbon atom in graphite only forms 3 covalent bonds with other carbon atoms, and each carbon atom still retains 1 free electron to transfer charge.
3. Lubricity: The lubricating performance of graphite depends on the size of the graphite flakes. The larger the flakes, the smaller the friction coefficient and the better the lubricating performance.
4. Chemical stability: Graphite has good chemical stability at room temperature, and is resistant to acids, alkalis and organic solvents.
5. Plasticity: Graphite has good toughness and can be rolled into very thin flakes.
6. Thermal shock resistance: Graphite can withstand drastic changes in temperature without being damaged when used at room temperature. When the temperature changes suddenly, the volume of graphite will not change much and no cracks will occur.
Post time: Oct-31-2020