Category:
Non-metal
Material Type:
non-metal
Alternative Names:
Tags:
Graphite
Non-metal
Basic Information
Composition & Structure
Composition:
Pure carbon (hexagonal crystal structure, sp² bonded layers)
Microstructure:
Layered hexagonal crystalline carbon with basal plane cleavage
Description
Graphite is a crystalline allotrope of carbon with a layered hexagonal structure. It is soft, friable, and electrically conductive along the basal planes. Used in electrodes, nuclear reactor moderators, crucibles, battery anodes, and mechanical seals. Preparation is challenging due to extreme friability — particles pull out easily creating artifacts confused with porosity.
Mechanical Properties
Hardness:
7-11 HV (extremely soft)
Hardness (HV):
7-11 HV
Hardness Category:
very soft
Tensile Strength:
10-40 MPa
Physical Properties
Density:
1.5-2.3 g/cm³
Melting Point:
Sublimes ~3650°C
Material Characteristics
Work Hardening:
No
Magnetic:
No
Corrosion Resistance:
excellent
Sectioning
Diamond wafering blade - fine grit / low concentration. Very low feed rate. Abrasive cut-off wheels cause catastrophic fracture.
Mounting
Castable with epoxy. Vacuum impregnation strongly recommended. Hot compression acceptable for dense grades.
Grinding
Start at 240 grit SiC minimum. Light pressure (10-15 N). Never use coarser grits.
Grinding sequence:
Grinding sequence:
- 240 grit: Planar grinding
- 360 grit: 1 min
- 600 grit: 1 min
- 800 grit: 1 min
- 1200 grit: 1 min
Recommended Sequence:
Polishing
Polishing sequence:
- 1μm diamond: on ATLANTIS pad with SIAMAT colloidal silica (2 min)
- 0.05μm alumina: on NAPPAD with DIALUBE Purple (30 sec)
Recommended Sequence:
Etching
Examined as-polished. Polarized light reveals crystallographic orientation through optical anisotropy. Crossed polarizers show color contrast between grains. Thermal etching (1000-1200°C) for grain boundaries if needed.
Common Etchants:
Heat Treatment
Manufactured through baking (carbonization) at ~1000°C and graphitization at 2500-3000°C. Not heat treated in service.
Applicable Standards
- ASTM C709
- ASTM C559
- ASTM C769
Applications
- Electrodes
- Nuclear reactor moderators
- Crucibles and molds
- Mechanical seals
Typical Uses
- Electric arc furnace electrodes
- Battery anodes
- Rocket nozzle throats
- Semiconductor processing fixtures
- Carbon brushes