Fiber Materials

In the class of carbon and graphite fiber materials both insulation and structural materials are combined: Soft and rigid felts are mainly used for thermal insulation at high temperatures. Carbon fiber-reinforced carbon (C/C, CFRC) is a tailor-made temperature-resistant fiber composite material for extreme demands.

Carbon fiber-reinforced carbon (C/C, CFRC) is a high-strength composite material consisting of a carbon or graphite matrix with carbon fiber-reinforcement. A large variety of different C/C materials can be manufactured. The materials are especially well-suited for technologically sophisticated applications.

SGL Group markets its C/C products under the brand name SIGRABOND®.

Typical properties of the material

  • Very strong and stiff
  • High fracture toughness
  • Lightweight
  • Low thermal expansion
  • Thermal shock resistant

C/C manufacturing

Carbon fibers and resins are the raw materials needed to manufacture C/C materials. Molding is accomplished through processes such as lamination or winding followed by pressing and curing of the pieces. The carbonization and graphitization steps are part of the thermal manufacturing process. In the final treatment phase, the work pieces are machined to the desired dimensions through mechanical processing.

Soft felts based on carbon fibers are indispensable when it comes to meeting maximum requirements for insulation properties. Also, soft felt is used as battery felt in energy storage devices.

Our high-temperature insulation soft felt is well-know under the brand name SIGRATHERM®, our battery felt is marketed under SIGRACELL®.

Typical properties of the material

  • Low thermally conductive
  • Low heat capacity
  • High-temperature resistant
  • Ultra-pure

Soft felt manufacturing

Felts from needled cellulose fibers are the soft felt raw materials. Those are converted into carbon soft felt by thermal treatment at 800-1,000 °C. Treating the carbon felt material even at higher temperatures beyond 2,000 °C the carbon fiber structure changes towards a graphite-like structure. These felts are usually called “graphite felts” although the ideal graphite structure does not form completely.

Both carbon and graphite soft felt are easy to handle: They can be cut with knifes or scissors and can therefore be adapted easily to any desired shape. 

Rigid felt is a shape rentending insulation material with low thermal conductivity made from carbon fibers used for the temperature range of 800 °C and above in inert gas and vacuum applications. A carbon binder anchors the fibers to prevent them from being ripped out. The standard shapes are plates or cylinders, other geometries are possible via machining.

SGL Group markets its rigid felt products under the brand name SIGRATHERM®.

Typical properties of the material

  • Shape retending
  • Low thermally conductive
  • Thermal shock resistant
  • Erosion proof

Rigid felt manufacturing

Rigid felt is produced by mixing and pressing of fiber material and binder, followed by high temperature treatment at temperature up to max. 2,800 °C. In the final production step the rigid felt is machined to the desired dimensions.

Also manufacturing of laminated panels with C/C or graphite foil layers as well as the application of an edge and erosion protection is possible.

With a SiC coating the service life of graphite components and composite materials can be extended. At the same time high-purity, inert, and dense surface structures are realized, required e.g. in processing semiconductor materials. Typical coating thicknesses are in the range of 100 µm.

Typical properties of the material

  • Dense
  • Wear resistant
  • Temperature and oxidation resistant
  • High thermally conductive

SiC coating process

Silicon carbide is deposited as thin layers on carbon fiber-reinforced carbon by CVD (chemical vapor deposition). Deposition takes typically place at temperatures of 1,200-1,300 °C. The thermal expansion behavior of the substrate material should be adapted to the SiC coating to minimize thermal stresses. 

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