Patent ID: 6274191
Filing Date: 2001-08-14
Classification: B01J,C23C

Abstract:
A method of controlling the rate of deposition of pyrocarbon onto a substrate while it is being levitated in an enclosure along with a fluidized bed of particles in order to produce a precise thickness of deposit of pyrocarbon of uniform crystalline properties, which method comprisesestablishing a bed of particles in fluidized condition in a coating zone within an enclosure along with at least one substrate to be coated, all of which are levitated by supplying an upward flow of a gaseous atmosphere which comprises an inert gas,heating said bed of particles and said substrate to a pyrolysis temperature in said coating zone and supplying said levitating gaseous atmosphere in a form that includes a mixture of a hydrocarbon component and an inert gas component, each of which components is supplied to said coating zone at a certain initial flow rate, such that pyrolysis of said hydrocarbon occurs causing pyrocarbon to be deposited upon surfaces of said substrate and upon said particles in said coating zone,monitoring either (a) the weight of said fluidized bed, or (b) the differential pressure between a location within or below said bed and a location above said bed, to determine changes that occur either in said weight or in said differential pressure, andadjusting the amount of said hydrocarbon component being supplied as a part of said upward coating flow based upon changes determined to have occurred either in said weight or in said differential pressure so as to compensate for such changes and thereby precisely regulate the rate of deposition of pyrocarbon over time and thereby produce a precise thickness of pyrocarbon coating of uniform crystalline properties upon said surfaces of said substrate during a coating run lasting for a definite period of time.