Purification – Our unpurified graphites have typical impurity levels over 1000 ppm. The major constituents are metals, our purification process reduces impurities to 5 ppm (99.9995%) or less as determined by ash analysis.
Carbon Densification - The process of manufacturing bulk synthetic graphite yields tiny voids (pores), which may link to the surface (open porosity) or be isolated (closed porosity). Densification partially fills the open pores with pure carbon, reducing the average pore size and open porosity. The open porosity is reduced by 80% through the process, resulting in graphite with reduced permeability.
Oxidation Inhibition - Graphite is subject to oxidation at high temperatures, typically above 450°C. Service temperature can be raised to 600°C by impregnating the pore structure of the graphite with zinc phosphate. The oxidation threshold increases an additional 50°C if the graphite is purified.
Resin Impregnation - The resin impregnation completely blocks the pore structure. This is applied to keep fluids from penetrating the pore structure of the graphite. The CFS process must be applied to bulk materials with a max cross section of 0.600". The maximum service temperature for the CFS impregnated material is approximately 150°C.
Acrylic Impregnation - The acrylic impregnation keeps fluids and air from penetrating the pore structure of the graphite and prevents cross talk between pores, much like the CFS impregnation. This process, however, yields a less abrasive material, increasing machinability and reducing the total cost of finished components. The process may be applied to bulk materials with a maximum cross section of 1". The recommended maximum service temperature for the impregnated material is approximately 150°C, with short term excursions up to 200°C.
Nickel Impregnation – Nickel metal is impregnated into the porosity of the graphite to adjust the acoustic characteristics of the graphite for use in non-destructive testing applications. The combination of POCO’s unique microstructure and the nickel impregnation gives an ultrasonic velocity signal that meets the requirements of multiple applications.
Silicon Carbide Coating – Silicon carbide (SiC) can be applied to graphite or solid SiC substrates. The coating is 75 microns thick and seals the underlying porosity. The SiC coating is applied via chemical vapor deposition and is inert to high temperature, acid attack, and chemical erosion that will erode graphite and other ceramics.
Pyrolytic Carbon Treatment - Parts go through a unique, proprietary CVI process that provides a nonporous surface with an amorphous carbon coating. The treatment completely seals the surface of one and five micron grade graphites and reduces particle generation in abrasive environments. The treatment must be performed on finished components.