The Structure and History of the Graphite Plate
Ⅰ. A historical overview of the graphite plate
A fibrous carbon is a graphite plate. Even when heated to 3000°C, however, elemental carbon does not melt. Elemental carbon cannot be melted into a liquid and then drawn into filaments.
As a result, the graphite plate is created from a variety of man-made or synthetic fibres with a high carbon content that are burnt under specialized process conditions, rather than from raw resources like coal or coke.
Natural fibres burned at high temperatures to generate graphite plates (which are both heat-resistant and electrically conductive) were first employed in the filaments of incandescent light bulbs in the 1880s.
The graphite plate produced from charring viscose yarns (such as copper-ammonia rayon and acetate rayon) and polyacrylonitrile filaments (a filament derived from acrylonitrile that polymerizes under the action of an initiator) were created and brought to market in the 1950s.
With a tensile strength of roughly 3500 kg/cm2 and a modulus of elasticity of around 0.28 0.63 x 106 kg/cm2, the original graphite plate was not very good. As a result, it can only be employed as a high-temperature insulating material or a corrosion-resistant filter material, but it can also be utilized as a mechanical industry sealant and an electric wave absorber.
The fast growth of the aviation industry and aerospace technology in recent years has necessitated the creation of a structural material with the following properties: high tensile strength, low coefficient of thermal expansion, high melting point, and superior corrosion resistance.
The tensile strength and modulus of elasticity of the different structural materials to be employed were given special consideration, resulting in the prominence given to the carbon graphite plate and composite.
Many countries conducted extensive research in the 1960s on the production process of the graphite plate and the selection of raw materials. Particularly in 1964, the United Kingdom applied the polyacrylonitrile filament as the main raw material and took in about 2000 °C low temperature pre-oxidation while adding tension, first producing a tensile strength of 21000 kg / cm2 of high strength and high modulus graphite. The manufacturing of the carbon graphite plate has been switched from intermittent to continuous (continuous pre-oxidation and carbonisation), resulting in a significant improvement in the production and quality of the graphite plate.
Ⅱ. The carbon fibre structure of the graphite plate
Of course, the structure of the carbon graphite plate differs significantly from that of raw material fibres. The carbon graphite plate is made up of practically pure carbon after high temperature carbonisation and is a polycrystal consisting of two dimensionally organized layers of disordered graphite microcrystals.
In two key aspects, it varies from a full graphite crystal.
1. The graphite lattice has a spacing of 3.354 A between consecutive layers, but the microcrystalline graphite that makes up the carbon graphite plate has a slightly greater gap of 3.42 A.
2. The layers of graphite lattices are spatially positioned relative to one another (e.g. in an ABAB or A-BCABC structure). The layers in the microcrystals of the carbon graphite plate, on the other hand, are randomly positioned with regard to one another, resulting in a lack of three-dimensional order, thus the name disordered graphite structure.
Graphite plate microcrystals with a disordered graphite layer structure vary in thickness and length depending on the charring process parameters. For example, La is 10~100A, which equates to 330 layers, and La is typically 20~60A but may be as long as 250A.
The microcrystals are subsequently polymerized into small fibres, which are secondary units in the carbon graphite plate, and the small fibres are collected into the carbon graphite plate.
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