Glassy Carbon Material Properties

Glassy carbon, also known as vitreous carbon or glass-like carbon, is a non-graphitizing form of pure carbon that exhibits a unique combination of ceramic and graphite-like properties. While the exact microstructure of glassy carbon is still a topic of ongoing research it is commonly agreed upon that its basic building blocks consist of irregularly stacked and curved sheets of graphene. This mixture of ordered and amorphous microstructures leads to a variety of unique material properties.

SIGRADUR® Glassy Carbon is an ultrapure form of glassy carbon heat treated up to 2200°C and is characterized by the following properties:

SIGRADUR® Material Grades

SIGRADUR® Glassy Carbon can be supplied in two grades, namely SIGRADUR® G and SIGRADUR® K:


SIGRADUR® G (G as in graphitising temperatures) is heated up to 2200°C and fulfils highest standards in terms of material purity, inertness as well as hardness and strength.


SIGRADUR® K (K as in coking temperatures) has a production temperature of 1100°C and is used in applications where increased reactivity is desirable, as e.g. in electrochemical or analytical applications.

TEM images of (a) SIGRADUR® K glassy carbon and (b) SIGRADUR® G Glassy Carbon. SIGRADUR® G has a more ordered graphene structure with less open-ended reaction centres, which imparts superior temperature resistance and intertness to the material. (Images adapted from P J F Harris, Phil Mag 84, 3159 (2004).

Physical Properties

Bulk density g/cm³ 1.54 1.42
Ash values acc. to DIN 51903 ppm < 100 < 100
Maximum service temperature (vacuum or inert gas) °C 1000 3000
Electrical resistance Ω·cm 50 x 10⁻⁴ 45 x 10⁻⁴
Open porosity % 0 0
Permeability coefficient cm²/s 10⁻¹¹ 10⁻⁹
Vickers hardness HV1 340 230
Flexural strength¹ N/mm² 210 260
Compressive strength² N/mm² 580 480
Young’s modulus¹ kN/mm² 35 35
Coefficient of thermal expansion (20-200°C) 1/K 3.5 x 10⁻⁶ 2.6 x 10⁻⁶
Thermal conductivity W/(K x m) 4.6 6.3

1) = 4-point bending test; geometry of specimen: circular rod, diameter: 3 mm, length: 60 mm
2) = geometry of specimen: circular rod, diameter: 7 mm, length: 10 mm