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:
- High Temperature Resistance of up to 3000°C
- High Purity
- Extreme Corrosion Resistance
- Impermeability and Non-Porosity
- Good Electrical Conductivity
- High Hardness and Strength
- High Surface Quality and No Particle Generation
- No wetting by melts
- Extreme Resistance to Thermal Shock and Low Thermal Expansion
- Isotropy of Physical and Chemical Properties
- Biocompatibility
- Low Density
SIGRADUR® Material Grades
SIGRADUR® Glassy Carbon can be supplied in two grades, namely SIGRADUR® G and SIGRADUR® K:
SIGRADUR® G
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
SIGRADUR® K (K as in co*king 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.
Physical Properties
SIGRADUR® K | SIGRADUR® G | ||
---|---|---|---|
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
Electrical Resistance
Figure 1: Specific electrical resistance of SIGRADUR® K and SIGRADUR® G Glassy Carbon
Thermal Conductivity
Figure 2: Thermal conductivity of SIGRADUR® K and SIGRADUR® G Glassy Carbon
Thermal Expansion
Figure 3: Coefficient of thermal expansion of SIGRADUR® K and SIGRADUR® G Glassy Carbon
Flexural Strength
Figure 4: Flexural strength of SIGRADUR® K and SIGRADUR® G Glassy Carbon as a function of corrosion time in 65% nitric acid at 120°C; 4-point bending test; geometry of test specimen: circular rod, diameter: 5 mm, length: 60 mm
Loss of Mass
Figure 5: Loss of mass of SIGRADUR® K and SIGRADUR® G Glassy Carbon as a function of corrosion time in 65% nitric acid at 120°C