About SIGRADUR®

SIGRADUR® glassy carbon is characterized by the following properties:

High Temperature Resistance in an Inert Gas or Vacuum at Temperatures up to 3000°C

SIGRADUR® glassy carbon is highly temperature resistant in inert gas or vacuum up to 3000°C. Unlike all other ceramic and metallic high temperature materials, glassy carbon increases in strength with rises in temperature up to 2400°C. Glassy carbon exhibits twice its room temperature strength at 2426°C. Compared to ceramic and metallic materials, glassy carbon is also not brittle at higher temperatures.

High Purity

SIGRADUR® glassy carbon consists of pure carbon. Glassy carbon’s raw materials have an extremely low content of foreign elements.
SIGRADUR® G is heated over 2000°C. At these high temperatures, most foreign elements vaporize and only pure carbon remains. Due to its high purity, glassy carbon is suitable for applications in chemical analysis, semiconductor technology, and ultra pure materials technology. Glassy carbon shows no memory effects which is advantageous in ultratrace analysis.

Extreme Corrosion Resistance

SIGRADUR® glassy carbon is extremely corrosion resistant. Due to its closed microstructure, glassy carbon doesn't form intercalation compounds. This characteristic gives extremely high resistance to corrosion by acids, alkaline agents, and melts. Strong oxidizing substances such as oxygen at temperatures over 600°C, in addition to hot melts and acids with powerful oxidizing actions, are the only substances that can harm glassy carbon. Even in this case, testing has shown that glassy carbon is still the most oxidation-resistant carbon material. Due to its high purity, the catalytic action of foreign elements (reaction centers) concerning oxidation and corrosion is limited to a minimum. SIGRADUR® G shows a higher corrosion resistance to oxidizing substances like nitric acid, perchloric acid, or oxygen. The oxidation speed of SIGRADUR® G in boiling 65% nitric acid is 24x lower than that of SIGRADUR® K.

Impermeability to Gases and Liquids (Non-Porous)

Glassy carbon is an impermeable material comparable with silica glass. The helium permeability as determined by the vacuum drop method is only 10-11 cm2 s-1. Thus glassy carbon is an ideal material for the vacuum technology.

No Wetting by Melts

SIGRADUR® glassy carbon shows no wetting by many saline, metallic, and ceramic melts. This is advantageous in metallurgy, ultra pure materials technology, and the glass industry.

Beneficial Hardness and Strength Characteristics

The mechanical properties of SIGRADUR® glassy carbon, including hardness and strength, are comparable with those of high-performance ceramics. Unlike all other ceramic and metallic high-temperature materials, glassy carbon increases in strength with rises in temperature up to 2400°C. Glassy carbon exhibits double its strength at 2426°C when compared to its strength at room temperature.

Low Density

Despite its high strength, SIGRADUR® glassy carbon has a very low density. For example, charging equipment made of glassy carbon has a very low thermal absorption due to its low mass. This enables short heating and cooling times. Additionally, for light weight constructions and units with high dynamic stress, glassy carbon can be used due to its low density.

High Surface Quality with No Particle Generation

SIGRADUR® glassy carbon has a very high surface quality and can be polished. Due to its hard and smooth surface, glassy carbon doesn't exhibit any particle generation like other carbon materials. Because of this, glassy carbon is very suitable for the semiconductor and glass industries.

Low Thermal Expansion

SIGRADUR® glassy carbon has very low and isotropic thermal expansion comparable with silica glass. Therefore, it retains its shape under heat, which is very advantageous for all high temperature applications.

Extreme Resistance to Thermal Shock

Compared to most ceramic and metallic materials, SIGRADUR® glassy carbon has an extremely high resistance to thermal shock. Therefore, short heating and cooling times are possible without issue.

Isotropy of Physical and Chemical Properties

SIGRADUR® glassy carbon is an isotropic material. Due to its fullerene-related microstructure, glassy carbon has no directional material properties.

Good Electrical Conductivity

SIGRADUR® glassy carbon is electrically-conductive and therefore suitable in uses such as electrochemistry and sensor technologies. Additionally, melting crucibles can be heated inductively.

Biocompatibility

SIGRADUR® glassy carbon is resistant to biological systems and has excellent compatibility with blood and tissue. Its good mechanical properties at low densities, its high purity, and its biocompatibility make SIGRADUR® glassy carbon a beneficial material for medical technology and biotechnology.