Definition of terms - Glossary from A to Z
Carbon – What Is It?
Carbon is one of the fundamental materials in modern industry. At Schunk, it forms the basis for high-performance solutions in areas such as bearing technology, sealing systems, and inductive heating systems. As a chemical element with the symbol C and atomic number 6, carbon is extraordinarily versatile: it occurs in various modifications and forms the foundation of countless compounds. Whether as graphite in tribological applications or in complex composite materials – carbon is a key element for material solutions under extreme conditions.
Diversity. Structure. Carbon.
Properties of the Chemical Element Carbon
Crystal Structures and Hybridization
Carbon can exist in various crystal forms – including graphite, diamond, and amorphous carbon. These so-called modifications differ fundamentally in their atomic structure, based on carbon’s ability to form different hybridization states: sp³ in diamond, sp² in graphite, and sp or mixed forms in other modifications.
- sp³ hybridization: 109° bond angle (e.g., methane CH₄)
- sp² hybridization: 120° bond angle, planar geometry (e.g., ethene C₂H₄)
- sp hybridization: 180° bond angle, linear (e.g., ethyne C₂H₂, HCN)
These electronic states explain the enormous structural diversity of carbon compounds.
Reactivity and Bonding Behavior
Carbon prefers to form four covalent bonds, resulting in extremely stable molecular structures. Especially notable is its ability to form chains and rings. In both organic and inorganic compounds, carbon commonly bonds with oxygen, hydrogen, nitrogen, or additional carbon atoms. This bonding versatility is the foundation of organic chemistry.
Circulation. Occurence. Climate.
Occurrence and Natural Cycles
Carbon is an essential component of biological, geological, and atmospheric systems. In nature, it undergoes a global cycle involving processes like photosynthesis, cellular respiration, weathering, and volcanism. It appears in the atmosphere as carbon dioxide, in soils as humus, in living organisms as organic compounds, and in the lithosphere as limestone or fossil fuels.
Major carbon reservoirs in nature:
- Lithosphere: over 99.8% of global carbon, mainly as carbonates (e.g., limestone)
- Hydrosphere: approx. 2.7 × 10¹³ tons, mostly as dissolved CO₂ in oceans
- Atmosphere: approx. 6 × 10¹¹ tons, mainly as CO₂
- Biosphere: approx. 2.7 × 10¹¹ tons, primarily stored in plants
These reservoirs significantly shape the global carbon balance and influence the climate.
Modifications
Graphite, Diamond, and Amorphous Carbon
Carbon exists in various modifications that differ greatly in structure and physical properties. Graphite consists of flat, stacked layers with delocalized electrons – a good electrical conductor.
Diamond, on the other hand, forms an extremely strong three-dimensional lattice. It is not electrically conductive but extremely hard. Amorphous carbon lacks an ordered structure but is technically versatile – e.g., as activated carbon or soot.
Comparison of Physical Properties
Graphite
- Structure type: Layered structure (sp²)
- Conductivity: High
- Hardness: Soft
- Typical applications: Lubricants, electrodes
Diamond
- Structure type: Space lattice (sp³)
- Conductivity: None
- Hardness: Very high
- Typical applications: Cutting tools, jewelry
Amorphous Carbon
- Structure type: Unordered
- Conductivity: Variable
- Hardness: Low to medium
- Typical applications: Filter material, pigments
DLC (Diamond-like Carbon)
- Structure type: Amorphous (sp³ + sp²)
- Conductivity: Medium
- Hardness: High
- Typical applications: Wear protection, medical technology
Glass Carbon
- Structural type: Disordered, isotropic
- Conductivity: Good
- Hardness: Hard, dense structure
- Typical applications: Electrochemistry, process engineering
Foundation. Commitment. Diversity.
Significance for Chemical Compounds and Life
Carbon is the central element of all organic compounds. By forming stable single, double, or triple bonds, it enables the creation of complex molecular structures – from simple hydrocarbons to proteins and DNA. In combination with oxygen, it forms oxidized compounds such as carbon dioxide, which is essential for metabolic processes and the global carbon cycle.
Typical carbon compounds in technology and nature:
• Carbohydrates: biological energy carriers
• CO₂: part of respiration and photosynthesis
• Hydrocarbons: energy carriers and plastics
• Organic acids & esters: metabolic and industrial building blocks
• Aromatics: dyes, pharmaceuticals, plastics
Without carbon, neither life nor modern materials would be possible.
Why Schunk?
Technical Relevance of Carbon Materials
Carbon materials are essential for industrial applications under extreme conditions. As a specialist in materials, Schunk offers a wide range of technical carbon and graphite materials that are characterized by high temperature resistance, electrical conductivity, and wear resistance. They are used in bearings, sealing systems, furnace components, and contact materials, contributing significantly to the efficiency and reliability of technical systems in demanding environments.
Schunk is Carbon Expert
Schunk also employs state-of-the-art techniques in shaping, surface modification, and material property engineering, including:
- CNC machining, 3D printing, slip casting, and isostatic pressing
- High-tech surface treatments like CVD coatings, pyrolytic carbon layers, Si and TaC coatings
- Materials such as C/C (carbon/carbon), C/C-SiC, carbon foams, or carbon felts
- Innovative applications in aerospace, medical, semiconductor, and energy technologies
This combination of material diversity, processing depth, and process integration makes us a leading provider in high-performance material technology.
The World of Schunk
