Patent GB-1055981-A (GB)
Title: Low-permeability high-density.carbon and grapite bodies
IPC: C04B35/52
Filed: 1963-06-14
Abstract: A high density carbon body is produced by heating a formed carbonaceous mass in a heat conducting, deformable, impermeable container, under pressure in a system which provides controlled fluid pressure outside (Pe) and inside (Pi) the container Pe being greater than Pi. PI is gas type; Pe may be gaseous or liquid. The carbonaceous mass may be powdered carbon or graphite, raw or calcined petroleum coke, or mixtures with anthracene oil or creosote oil, with or without a binder, e.g. pitch, coal tar, phenolic resins, furfuryl alcohol, or furanketone polymers (15-50 parts per 100 parts carbon). It may be formed into a rod or tube (1 in Fig. 1, not shown) and is wholly or partly surrounded in the container by a refractory powder 2, e.g. carbon grist, coke, or graphite, which may be finer near the body (Figs. 2-5, (not shown) show different arrangements). Container 4 may be of copper sheathing or Al foil, in cylindrical annular, or spherical form, of thickness 0.008-0.045 inch, and may be surrounded in stainless steel pressure vessel 6 by a liquid, e.g. a low melting lead alloy. Vessel 6 is connected between a fluid pressure supply system (compressor 14 and tank 7 for N2, A, or flue gas) and water cooled condenser 8 for escaping gases, kept under pressure by valve 8a.  Pi and Pe are maintained via lines 5 and 10 respectively, and controlled by inlet valves 15 and 11 and vent valves 18 and 20 respectively.  The body may be heated by means of furnace 9 or heating coils, at not more than 100 DEG  C. per hour to a maximum of 800 DEG  C. Pi should be high enough to keep the volume of gases leaving the body small.  Initially, Pe and Pi may be high, e.g. 2200 and 1800 p.s.i. respectively, and during or after heating, while the body is still plastic, the differential pressure is increased, either by keeping Pe constant and venting Pi, or by keeping Pi constant and raising Pe.  Alternatively Pe and Pi may be kept constant throughout, and vented together. The differential pressure may be 50-5000 p.s.i. The body may subsequently be removed from the container and further baked to 800-1250 DEG  C, then gaphitized at 2000-3000 DEG  C., and may be impregnated, e.g. with pitch, before or after baking. Reference has been directed by the Comptroller to Specification 876,924.ALSO:A fluid pressure system comprises a heat-conducting deformable, impermeable container for the body to be treated, means for heating the container, and means for providing a contolled gaseous pressure within the container (Pi) and a larger controlled fluid pressure on the outside (Pe), thereby causing mechanical pressure to be transmitted by the container to the body.  The container 4 (Fig. 1, not shown) may be of copper sheathing on Al foil, in cylindrical annular, or spherical form, of thickness 0.008-0.045 ins. and may be surrounded in stainless steel pressure vessel 6 by a liquid, e.g. a low melting lead alloy.  Vessel 6 is connected between a fluid pressure supply system (compressor 14 and tank 7 for N2, A, or fine gas) and water cooled condenser 8 for escaping gases, kept under pressure by valve 8a.  Pi and Pe are maintained via lines 5 and 10 resp. and controlled via inlet valves 15 and 11 and vent valves 18 and 20 resp.  The system may be heated by means of furnace 9 or heating coils.  Initially Pe and Pi may be high, e.g. 2200 and 1800 p.s.i. resp., and during or after heating the differential pressure may be increased either by keeping Pe constant and venting Pi, or by keeping Pi constant and raising Pe. Alternatively Pe and Pi may be kept constant throughout, and vented together.  The differential pressure may be 50-500 p.s.i. The body may be surrounded in the container by a refractory powder 2, e.g. of carbon grist, coke or graphite.  The body may be a carbonaceous mass, from which a dense carbon body is produced.  Reference has been directed by the Comptroller to Specification 876,924.