pressure or by radiation damage.
See: GRAPHITIC CARBON.
Nuclear Graphite
Description
NUCLEAR GRAPHITE is a POLYGRANULAR GRAPHITE material for use in nuclear reactor cores consisting of GRAPHITIC CARBON of very high chemical purity. High purity is needed to avoid absorption of low‐energy neutrons and the production of undesirable radioactive species.
See: GRAPHITE MATERIAL, GRAPHITIC CARBON, POLYGRANULAR GRAPHITE.
Notes
Apart from the absence of neutron‐absorbing impurities, modern reactor graphites are also characterized by a high degree of GRAPHITIZATION and no preferred bulk orientation. Such properties increase the dimensional stability of the NUCLEAR GRAPHITE at high temperatures and in a high flux of neutrons. The term NUCLEAR GRAPHITE is often, but incorrectly, used for any GRAPHITE MATERIAL in a nuclear reactor, even if it serves only for structural purposes.
See: GRAPHITE MATERIAL, GRAPHITIZATION.
Pan‐Based Carbon Fibers
Description
PAN‐BASED CARBON FIBERS are CARBON FIBERS obtained from polyacrylonitrile (PAN) precursor fibers by STABILIZATION TREATMENT, CARBONIZATION, and final heat treatment.
See: CARBON FIBERS, CARBONIZATION, STABILIZATION TREATMENT.
Particulate Carbon
Description
PARTICULATE CARBON is a CARBON MATERIAL consisting of separated monolithic particles.
See: CARBON MATERIAL.
Notes
Distinctions should be made between coarse PARTICULATE CARBON or GRANULAR CARBON (larger than about 100 μm, but smaller than about 1 cm in average size), fine PARTICULATE CARBON or powder or flour (between 1 and 100 μm in average size), and COLLOIDAL CARBON (below approximately 1 μm in size in at least one direction), e.g. CARBON BLACKS and COLLOIDAL CARBON.
See: CARBON BLACK, COLLOIDAL CARBON, GRANULAR CARBON, PARTICULATE CARBON.
Petroleum Coke
Description
PETROLEUM COKE is a CARBONIZATION product of high‐boiling hydrocarbon fractions obtained in petroleum processing (heavy residues). It is the general term for all special PETROLEUM COKE products such as GREEN, CALCINED, and NEEDLE petroleum COKE.
See: CALCINED COKE, CARBONIZATION, GREEN or RAW COKE, NEEDLE COKE.
Notes
High‐boiling hydrocarbon fractions (heavy residues) used as feedstock for PETROLEUM COKE are residues from distillation (atmospheric, vacuum) or cracking (e.g. thermal, catalytic, steam‐based) processes. The nature of feedstock has a decisive influence on the graphitizability of the CALCINED COKE.
See: CALCINED COKE.
Petroleum Pitch
Description
PETROLEUM PITCH is a residue from heat treatment and distillation of petroleum fractions. It is solid at room temperature, consists of a complex mixture of numerous predominantly aromatic and alkyl‐substituted aromatic hydrocarbons, and exhibits a broad softening range instead of a defined melting temperature.
Notes
The hydrogen aromaticity (ratio of aromatic to total hydrogen atoms) varies between 0.3 and 0.6. The aliphatic hydrogen atoms are typically present in alkyl groups substituted on aromatic rings or as naphthenic hydrogen.
Pitch
Description
PITCH is a residue from pyrolysis of organic material or tar distillation, which is solid at room temperature, consisting of a complex mixture of numerous, essentially aromatic hydrocarbons and heterocyclic compounds. It exhibits a broad softening range instead of a defined melting temperature. When cooled from the melt, PITCHES solidify without crystallization.
Notes
The ratio of aromatic to aliphatic hydrogen depends mainly on the source of the starting material. The hydrogen aromaticity (ratio of aromatic to total hydrogen atoms) varies between 0.3 and 0.9.
The aliphatic hydrogen in PITCH is largely associated with alkyl side chains substituted on aromatic rings. The content of heterocyclic compounds in pitches varies depending on their origins. Also the softening temperature can vary in a broad range between about 320 and 570 K depending on the molecular weight (relative molecular mass) and composition of the constituents.
Pitch‐Based Carbon Fibers
Description
PITCH‐BASED CARBON FIBERS are CARBON FIBERS obtained from PITCH precursor fibers after STABILIZATION TREATMENT, CARBONIZATION, and final heat treatment.
See: CARBON FIBERS, CARBONIZATION, PITCH, STABILIZATION TREATMENT.
Notes
The term PITCH‐BASED CARBON FIBERS comprises the ISOTROPIC PITCH‐BASED CARBON FIBERS as well as the anisotropic MESOPHASE PITCH‐BASED CARBON FIBERS (MPP‐BASED CARBON FIBERS). The isotropic type belongs to the CARBON FIBERS TYPE LM (LOW MODULUS) and is mainly used as filler in polymers and insulation materials and for similar applications. The anisotropic type (MPP‐BASED CARBON FIBERS) belongs to the CARBON FIBERS TYPE HM and is used mainly for reinforcement purposes due to its high Young’s modulus value.
See: CARBON FIBERS TYPE HM, CARBON FIBERS TYPE LM (LOW MODULUS), ISOTROPIC PITCH‐BASED CARBON FIBERS, MESOPHASE PITCH‐BASED CARBON FIBERS.
Polycrystalline Graphite
Description
