High-density isotropic graphite has high mechanical strength, low anisotropy ratio, wide crystal size, moderate modulus and fracture stress, can maintain high elastic strain for a long time before fracture, and has good abrasion resistance. Features such as low open porosity.
The manufacturing process of high-density isotropic graphite materials can basically be divided into two types: one-component system and two-component system. The one-component system refers to the original single aggregate, such as hard spherical pitch coke, pitch mesosphere sphere, and specially treated petroleum coke. The binary system uses fine-grained aggregate + binder, such as phenanthrene coke + asphalt binder. In order to achieve high-density isotropy, the following measures are taken in the process:
(1) Use aggregates with large shrinkage during heat treatment, isotropic aggregates, add carbon black, and select binders with high carbonization yields. It can also be carbonized under pressure or added sulfur or nitro compounds in the binder to Promote heavy condensation.
(2) When using the unitary system method, use fine particles as much as possible, such as 150μm or less, so that the particle size ratio is appropriate to achieve the maximum packing density.
(3) Adopt isostatic pressing molding or friction impact molding.
(4) During graphitization, keep the product at high temperature for a long time or pass halogen gas at high temperature to reduce the impurity content.
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