Graphite
Description
PYROLYTIC GRAPHITE is a GRAPHITE MATERIAL with a high degree of preferred crystallographic orientation of the c‐axes perpendicular to the surface of the substrate, obtained by GRAPHITIZATION HEAT TREATMENT of PYROLYTIC CARBON or by chemical vapor deposition at temperatures above 2500 K.
See: GRAPHITE MATERIAL, GRAPHITIZATION HEAT TREATMENT, PYROLYTIC CARBON.
Notes
“Pyrographite,” a synonym for PYROLYTIC GRAPHITE, was introduced as a trademark and should not be used as term.
Hot working of PYROLYTIC GRAPHITE (by heat treatment under compressive stress at temperatures above 3000 K) results in HIGHLY ORIENTED PYROLYTIC GRAPHITE (HOPG).
See: HIGHLY ORIENTED PYROLYTIC GRAPHITE.
Raw Coke
Description
See: GREEN COKE.
Notes
The term RAW COKE is equivalent to GREEN COKE although it now used less frequently.
See: GREEN COKE.
Rayon‐Based Carbon Fibers
Description
RAYON‐BASED CARBON FIBERS are CARBON FIBERS made from rayon (cellulose) precursor fibers.
See: CARBON FIBERS.
Notes
RAYON‐BASED CARBON FIBERS have a more isotropic structure than similarly heat‐treated polyacrylonitrile (PAN)‐ or MESOPHASE PITCH‐BASED (MPP‐BASED) CARBON FIBERS. Their Young’s modulus values are therefore drastically lower (Youngs modulus, E < 100 GPa; tensile strength, σ > 100 MPa). RAYON‐BASED CARBON FIBERS can be transformed into anisotropic CARBON FIBERS with high strength and Young’s modulus values by hot‐stretching treatment at temperatures of approximately 2800 K.
See: CARBON FIBERS, MESOPHASE PITCH‐BASED CARBON FIBERS, PAN‐BASED CARBON FIBERS.
Regular Coke
Description
REGULAR COKE is a PETROLEUM COKE with good graphitizability and is characterized by a combination of properties that differ significantly from those of METALLURGICAL COKE but do not reach the quality level of PREMIUM COKE. These properties are optical anisotropy, medium reversible thermal expansion, and low ash content.
See: METALLURGICAL COKE, PETROLEUM COKE, PREMIUM COKE.
Notes
Typical characteristics for REGULAR COKE in comparison with those of METALLURGICAL COKE and of PREMIUM COKE calcined at 1620 K are:
| Regular coke | Premium coke | Metallurgical coke | |
| Real densitya) (g × cm−3) | 2.07–2.09 | 2.12–2.14 | 1.95–2.02 |
| CTEb) (293–773 K) (K−1) | 2.0 × 10−6 | 1.1 × 10−6 | >3.0 × 10−6 |
| CTEb) (293–773 K) (K−1) | 1.0 × 10−6 | 0.5 × 10−6 | 2.0 × 10−6 |
| Ash (wt%) | 0.4 | 0.05 | 8–12 |
| Sulfur (wt%) | 1.0–1.5 | 0.6 | 0.6–5.0 |
a) Measured with m‐xylene.
b) Coefficient of thermal expansion.
REGULAR COKE is mainly used for the production of SYNTHETIC CARBON and GRAPHITE MATERIALS.
See: CARBON MATERIAL, GRAPHITE MATERIAL, METALLURGICAL COKE, PREMIUM COKE, SYNTHETIC GRAPHITE.
Rhombohedral Graphite
Description
RHOMBOHEDRAL GRAPHITE is a thermodynamically unstable allotropic form of GRAPHITE with an ABCABC stacking sequence of the layers. The exact crystallographic description of this allotropic form is given by the space group D53d‐R3m (unit cell constants: a = 256.6 pm, c = 1006.2 pm).
See: GRAPHITE.
Notes
The structure of RHOMBOHEDRAL GRAPHITE can be best considered as an extended stacking fault in HEXAGONAL GRAPHITE. RHOMBOHEDRAL GRAPHITE cannot be isolated in pure form (NATURAL GRAPHITE and laboratory preparations contain less than 40% of RHOMBOHEDRAL GRAPHITE in combination with HEXAGONAL GRAPHITE). It is produced by shear deformation of HEXAGONAL GRAPHITE and transforms progressively to the hexagonal (ABAB) modification on heating above 1600 K.
See: HEXAGONAL GRAPHITE, NATURAL GRAPHITE.
Semicoke
Description
SEMICOKE is a carbonaceous material intermediate between a fusible MESOPHASE
