Pyrocarbon Manufacturing

Pyrocarbon is deposited onto a suitable substrate by the thermal decomposition of a gaseous hydrocarbon at high temperature, using a process called Chemical Vapor Deposition (CVD). CVD is a very versatile process used in the production of coatings, powders, fibers and monolithic parts. (Source: White paper: "Medical Applications of Carbonaceous Materials" Authors M. Hassler, S. Ramboud, C. Real, BioProfile.)

With CVD, it is possible to produce almost any metallic or non-metallic element, including carbon and silicon, as well as compounds such as carbides, nitrides, borides, oxides, and many others. A key advantage of the CVD process lies in the fact that the reactants used are gases, thereby taking advantage of the many characteristics of gases. One result is that CVD is not a line-of-sight process as are most other plating/coating processes. In addition to being able to penetrate porous bodies, CVD offers many advantages over other deposition processes, including: (Source)

High purity – typically 99.99-99.999%
High density – nearly 100% of theoretical
Material formation well below the melting point
Coatings deposited by CVD are conformal and near net shape
Economical in production, since many parts can be coated at the same time

Graphite has properties that are particularly well suited for pyrocarbon coating, most notably its thermal expansion coefficient that avoids weakening the coated substrate. In order to appear visible on X rays, graphite is soaked in tungsten. This permeation does not change the mechanical properties of the substrate.

To make pyrocarbon-coated orthopedic implants, a graphite substrate is introduced into a chamber that is heated to between 1,200º and 1,500º Celsius. A hydrocarbon gas, typically propane, is introduced into the chamber. The extreme heat breaks the hydrogen bonds and releases a carbon atom. This carbon atom then deposits itself onto the graphite substrate. Over a period of time the substrate is completely coated with between 300 and 600 microns of pyrolytic carbon. Reaction byproducts are then exhausted out of the system. (Source: BioProfile)

The physical and mechanical properties of this isotropic material fall between those of graphite and diamond, two other materials of the same carbon family.

x The Pyrocarbon Manufacturing Process x
Raw material - graphite substrate rod
Machining of graphite substrate
Pyrocarbon deposited on graphite substrates (CVD technique) CVD Chamber
Inspection
Orthopedic implant BioProfile CMI

Learn more about pyrocarbon in healthcare

    CVD Chamber

 

CVD Diagram
Graphite Substrate
  Cutaway view of the BioProfile™ Resurfacing Capitate Resurfacing Implant (RCPI)
 

Cutaway Graphite Substrate
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