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what is the transparency and fracture of graphite
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Briefly:
- Transparency: Bulk graphite is essentially opaque in the visible range (it looks black/steel‑gray). However it is highly thickness‑dependent: very thin flakes transmit light. A single graphene layer absorbs about 2.3% of visible light (so a monolayer is nearly transparent), and each additional layer adds roughly the same absorption, so only a few layers are needed before the material appears dark.
- Fracture / cleavage: Graphite is extremely anisotropic. Strong covalent sp2 bonds hold atoms together within the hexagonal basal planes, while weak van der Waals forces bind those planes to one another. That gives graphite perfect basal cleavage (it splits easily into thin, flexible sheets parallel to the (0001) planes). Breakage across the layers (perpendicular to the basal planes) is much less regular and typically produces uneven or brittle fracture surfaces. This anisotropy is also why graphite is soft and a good lubricant along the planes but mechanically weak perpendicular to them.
- Transparency: Bulk graphite is essentially opaque in the visible range (it looks black/steel‑gray). However it is highly thickness‑dependent: very thin flakes transmit light. A single graphene layer absorbs about 2.3% of visible light (so a monolayer is nearly transparent), and each additional layer adds roughly the same absorption, so only a few layers are needed before the material appears dark.
- Fracture / cleavage: Graphite is extremely anisotropic. Strong covalent sp2 bonds hold atoms together within the hexagonal basal planes, while weak van der Waals forces bind those planes to one another. That gives graphite perfect basal cleavage (it splits easily into thin, flexible sheets parallel to the (0001) planes). Breakage across the layers (perpendicular to the basal planes) is much less regular and typically produces uneven or brittle fracture surfaces. This anisotropy is also why graphite is soft and a good lubricant along the planes but mechanically weak perpendicular to them.
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