f m effectively infiltrates the carbon sheet material and increases the sheet density by at least 20 grams per square meter the velocity of the carbon depositing flow stream is maintained at from about 20 to 200 ft per minute application_number US 64260775 A description in fig1 is shown a continuous carbon vapor depositing apparatus 10 for infiltrating an elongated sheet 12 of porous fibrous carbon with pyrolytic graphite pyrolytic graphite is anisotropic graphite which is deposited at high temperatures from a hydrocarbon gas the basal planes are randomly stacked which causes a marked directional difference in physical thermal and electrical properties a principal anisotropic property is thermal conductivity in the planar direction similar to copper whereas it is an excellent insulator similar to a phenolic plastic in the direction through the thickness sheet 12 supplied between feed rolls 14 is for example a carbon or graphite material such as a paper of matted graphite fibers a woven graphite cloth or carbonized cellulosic paper after the porous fibrous carbon material is infiltrated with pyrolytic graphite in apparatus 10 it is extremely well adapted for use as an electrode in a fuel cell such as oxygen hydrogen fuel cell like those.