Silicon Carbide Coatings for Pyrolytic Graphite Substrate
Silicon carbide (SiC) is composed of tetrahedra of carbon and silicon atoms with strong bonds in the crystal lattice.
This produces a very hard and strong material. Silicon carbide is not attacked by any acids or alkalis or molten salts
up to 800°C. In air, SiC forms a protective silicon oxide coating at 1200°C and is able to be used up to 1600°C.
The high thermal conductivity coupled with low thermal expansion and high strength gives this material exceptional
thermal shock resistance properties.
- Low density
- High strength
- Low thermal expansion
- High thermal conductivity
- High hardness
- High elastic modulus
- Excellent thermal shock resistance
- Superior chemical inertness
Heat and Wear-Resistant Materials
Carbon composites are routinely used in airplane brakes where light weight, low wear rate, and temperature resistance are critical.
Carbon composites also provide self-lubricating features that promote extended life. For example, a specialized brake pack for the
V-22 Osprey aircraft was developed in cooperation with Parker Hannifin using a carbon composite coated with silicon carbide.
This brake surface offers exceptional friction performance over a wide temperature range and excellent wear results.
The high thermal conductivity coupled with low thermal expansion and high strength gives this material exceptional thermal
shock resistance along with very high friction properties
Carbon Composite SiC Product Applications
- Mechanical drives
- Torque transmitters/limiters
Pyroid® pyrolytic graphite is available as custom free standing as deposited shapes, having diameters up to 18 in. (46 cm) and wall
thickness of 0.050 in. (0.127 cm). Some of the shapes we manufacture are cylindrical tubes, spherical domes, rods, crucibles, trays,
and shapes to match your specifications and drawings.
Pyrolytic Graphite for the Glass Industry
Pyroid pyrolytic graphite material is a universal glass-handling material having exceptional heat resistance, strength, and durability
with non-absorption characteristics to perform under the most rigorous conditions without damaging the glassware.
The material offers:
- Exceptionally high purity > 99.999%
Benefit: No marring of glass surfaces
- Exceptional high oxidation resistance
Benefit: Extremely long tool life
- High thermal conductivity
Benefit: Exception tolerance to thermal shock
Ideal for all types of glass including:
- Lead Glass
- Aluminosilicate glass
- Fused silica
Found in such applications as:
- Fine stemware
- Pharmaceutical packaging
- Specialty glass tubing
Pyroid PG SN and CN is ideal material for tools for manufacturing of all mirror surfaces
Analytical Instrument Accessories
Low metallic impurities (< 5 ppm total metallic ash) make Pyrolytic Graphite ideal material for manufacturing atomic absorption
spectrograph planchettes, crucibles for plasma vaporization, and sputter-coating scanning electron microscope samples
requiring a conductive, non-metallic coating and bio-compatible material requirement.
Pyroid® pyrolytic graphite has a long history of successful operation as a material of choice for solid propellant rocket exhaust
nozzles, throat inserts, and guide vanes.
Pyrolytic graphite is an excellent thermal insulator in the direction normal to the deposition layer planes. The material offers
the lowest known erosion resistance of any material operating under severe conditions up to flame temperatures of
3,600 oC (6,500 oF).
The best erosion resistance is achieved by exposing the pyrolytic graphite layer plane to the hot discharge gases. When used in
this orientation for best erosion resistance, the inherent insulating properties in the material leads to a rapid rise in nozzle surface
temperature and a significant reduction in the heat leakage along the nozzle body, promoting a near stoichiometric combustion
Pyroid® pyrolytic graphite is also available as a nozzle throat insert, compatible with most composite
AGM-88 High-Speed Anti-radiation Missile (HARM)
(Courtesy of Raytheon Corp.)
materials. These inserts are orientated to better withstand mechanical erosion of the hot exhaust gases while promoting rapid
thermal transfer away from the hot zone.
Because the throat geometry remains constant throughout the propellant burn, this promotes a more predictable burn of the
propellant grain, even under high acceleration loads.
Studies have shown that for low temperature propellants, the erosion of Pyroid® pyrolytic graphite is negligible. Also
environmental firing test results indicate pyrolytic graphite nozzles and inserts are relatively insensitive to a wide range of
reactive propellant combinations.
These advantages, coupled with Pyroid® pyrolytic graphite's high strength, high thermal conductivity, low thermal expansion,
and low weight are keys to extending the range of today's advanced rocket technology.
The ultrahigh purity (< 5 ppm ash) and high density (2.2 g/cc) of PG material results in sputtered carbon films showing enhanced
mechanical and tribochemical wear critical to the protection of rigid disks.