Hot-Press Method Applied to Anisotropy of Compressed Carbon Product

Abstract

Graphitized carbon products contain anisotropy in their own properties. Its degree depends on the condition of filler and binder. Soft carbon such as petroleum coke, is used as filler material, and tends to become needlelike particles when crushed. The crystallites of graphite orient along its length. By extrusion, these coke particles line up selectively in the pressing direction, whereby anisotropy grows, and in molding process, those ones line up perpendicularly in the pressing direction.
Meanwhile, the product kept under compression during carbonization get shrunk in its own volume, and then it shrinks again in graphitization process. Accordingly, such product results in possessing higher density than usual product.
In this investigation, the carbonization under compression, purposed to increase in apparent density of carbon product, was carried out. The orientation of crystallite grown in the sample was estimated from the anisotropy in electrical resistance, thermal expansion, and X-ray diffraction obtained.
The following results were obtained:
(1) The products from carbonization under compression of mixture of petroleum coke powders and binder possessed more anisotropy than usual molded products. This fact suggests that the compression facilitated the flow of the particles.
(2) The samples from the pre-extruded product, carbonized under compression, possessed less anisotropy than usual extruded products. It is considered that the effect of extrusion on orientation and that in molding interacted reciprocally.