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US 3,944,686 AGranted
Method for vapor depositing pyrolytic carbon on porous sheets of carbon material
AssigneePfizer Inc.
InventorRobert W. Froberg
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AssigneePfizer Inc.
InventorRobert W. Froberg
Estimating the term…
An elongated continuous porous sheet of fibrous carbon, such as paper of matted graphite fibers, woven graphite cloth or carbonized filter paper is longitudinally traversed through a reduced pressure heating zone (5 mm. of Hg.) in which hydrocarbon gas is perpendicularly directed at relatively high velocities through restricted flow passages at the sheet, which is heated to a temperature of about 2200.degree.C. The sheets are traversed at a speed of about 60 to 3600 feet per hour at a temperature of about 2000.degree. to 2400.degree.C at a pressure of from about 4 to 20 mm. Hg. A hydrocarbon gas, at a flow rate of from about 5 to 20 c.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 (STP).
A method of infiltrating a sheet of porous fibrous carbon with pyrolytic graphite comprising the steps of traversing an elongated sheet of porous fibrous carbon in a longitudinal path of travel, drawing a subatmospheric pressure in a treating zone in said path to reduce sooting, heating the sheet in the treating zone to a pyrolytic carbon-deposition temperature, impinging relatively narrow flow streams of hydrocarbon gas upon the heated sheet in the treating zone through a number of substantially restricted flow channels directed at the sheet to cause the gas to flow at a velocity of from about 20 to about 200 (STP) feet per minute whereby a deposit of pyrolytic graphite is infiltrated on the sheet without substantially obstructing the flow channels.
Dependencies are inferred from the claim text.