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Machined Parts

Surface treatments such as pyrolytic coatings should only be done on finished, machined parts. Machining after treatment will expose the graphite substrate.

  

Purification

Suffix -2 for semiconductor grades that end in the number 1; and -1 for other grades (industrial)
Effect Reduces impurities to 5 ppm or less as determined by ash analysis
Summary Unpurified POCO graphites have typical impurity levels of about 1000 ppm, but they can have up to 3000 ppm. The dominant impurity is vanadium, with some iron, aluminum, calcium, nickel, titanium, and silicon. Gaseous impurities do not show up in ash tests, and may be present in small amounts in purified materials
Physical Properties Not affected
Application Recommended after final machining

Densification

Suffix -3 for semiconductor grades that end in the number 1; and -1 for other grades (industrial
Effect Reduces open porosity by 80%
Summary Graphite has 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. This produces a graphite with very low permeability
Physical Properties Not affected
Application Can be applied to bulk material
Does not affect dimensions
 

Pyrolytic Treatment

The treatment completely seals the surface of the graphite and reduces particle generation in demanding environments. These materials resist attack by acids.

 

POCO produces a number of pyrolytic carbon treated materials marketed under different trade names for semiconductor applications. Each of these different materials is targeted at specific applications.

 

For industrial application, POCO produces a pyrolytic carbon treatment on AXF-5Q and this material is designated as AXF-5QPyC.