Graphite is widely used in the aerospace field due to its advantages such as self-lubricating performance, easy molding and processing, good thermal conductivity, thermal stability, and stable chemical properties. It is used in applications such as sealing materials, throat liner materials, brush materials, aerospace equipment parts, insulation materials, and radiation-resistant materials, such as graphite rings for aviation, piston rings, aviation bearings, graphite sealing components for aerospace, etc.
In the military industry, isostatic graphite, due to its small expansion coefficient, can be used to manufacture graphite nozzles for solid fuel rockets. The non-magnetic property of graphite can be used for the nose cone of ballistic missiles. It can be used as the throat liner material for small rocket solid rocket engines. The electrical conductivity and wear resistance of graphite are used as brush materials for various engines, frequency converters, and motors.
Characteristics of Graphite Products
(1) Density
The theoretical density of graphite single crystal is 2.26g/cm³. Usually, the density of artificial graphite is between 1.5 - 1.9g/cm³. The density of solid pyrolytic carbon can reach 2.1g/cm³. The density value of pure graphite is the quotient obtained by dividing its mass by volume (including all pores).
(2) Mechanical Strength
Unlike most other materials, the tensile, flexural and compressive strengths of artificial graphite increase with the increase of temperature. After reaching 2200K, its strength will decrease. At 2200K, the strength value of graphite is twice that at room temperature.
(3) Electrical Conductivity
Unlike other metals, the temperature coefficient of resistance of graphite is negative. Graphite has good electrical conductivity. Close to absolute zero, it has only a few free electrons and can act as an insulator by itself. As the temperature rises, its electrical conductivity increases. The electrical conductivity of graphite is higher than that of many metals, and its value decreases with the increase of temperature. The thermal conductivity of graphite varies depending on its degree of graphitization.
(4) Thermal Expansion
The thermal expansion coefficient of graphite is ranked at the level of 3×10⁻⁶K⁻¹, which is only equivalent to 1/4 of that of iron. The thermal expansion coefficient values of different grades of graphite will change and are also related to the anisotropy and temperature of the graphite material.
(5) Specific Heat
The specific heat of graphite varies greatly in the temperature range of 500K - 1500K. It increases greatly with the increase of temperature. However, for different grades of graphite, the change in specific heat is very small.
(6) Temperature Resistance
Graphite does not melt but can withstand temperatures up to 750K at 3900K. Graphite has very good thermal shock resistance, so rapid heating or cooling will not cause problems for graphite.
(7) Machinability
Graphite is easy to machine, and its edge strength and wear resistance are good. Components with complex structures and strict tolerances can be obtained through finish machining. Graphite has very good resistance to infiltration and will not be infiltrated by molten glass or most metals.
