rel="nofollow" href="#ulink_d101a1e2-d8c4-5b2c-aadd-ecb4538700f2">Table 5.2 shows a classification [16, 17]. The host rocks consist of quartz, mica, gneiss, feldspars associated with pegmatite aplite, granite magnetite, and calcite.
Figure 5.5 Scanning electron microscopy (SEM) picture of a flake natural graphite.
Table 5.2 Classification of natural graphite.
| Deposit | Carbon content (%) | Average crystallite diameter (mm) | Origin | |
|---|---|---|---|---|
| Macrocrystalline flakes | Brazil | <60 | <0.1 | Syngenetic cata‐ and mesozonal metamorphism of sapropelites |
| Germany (Kropfmühl) | ||||
| China | ||||
| Canada | ||||
| Malagasy Republic | ||||
| Norway | ||||
| India | ||||
| Zimbabwe | ||||
| Russia | ||||
| Mozambique | ||||
| Tanzania | ||||
| Macrocrystalline lumps | Sri Lanka | <100 | <0.01 | Epigenetic, probably pneumatolytic |
| Mesocrystalline | Austria | 30–90 | <0.001 | Syngenetic metamorphism of sapropelites |
| Czech Republic | ||||
| Microcrystalline | China | 30–90 | <0.001 | Syngenetic, epizonal metamorphism of coals |
| Korea | ||||
| Russia | ||||
| Mexico Austria |
5.3 Synthetic Graphite
According to IUPAC nomenclature [11], the term “synthetic graphite” should be used instead of “artificial graphite.” The IUPAC describes “synthetic graphite” as follows:
Synthetic graphite is a material consisting of graphitic carbon which has been obtained by graphitization of non‐graphitic carbon, by chemical vapor deposition (CVD) from hydrocarbons at a temperature above 2500 K, by decomposition of thermally unstable carbides or by crystallizing from metal melts supersaturated with carbon.
Figure 5.6 Classification of different forms of carbon according to IUPAC nomenclature. Approved IUPAC terms are printed in italics [11].
Figure 5.6 provides an overview on the recommended IUPAC nomenclature, together with examples for visualization.
In principal all carbon‐containing substances are suited as raw materials for the production of non‐graphitic or graphitic solid carbon materials as long as sufficient carbon remains after the first thermal degradation, the so‐called pyrolysis. Other technical synonyms for heat treatment below graphitization temperatures (>2500 K) under the exclusion of oxygen are coking, calcining, and baking. Whether the product of pyrolysis is a non‐graphitizable or graphitizable carbon depends in general on the mobility of the molecules during pyrolysis. This means the capability to arrange the necessary microstructural pre‐order for the subsequent solid‐state healing process under graphitization conditions (>2500 K). The principle is illustrated in Figure 5.7.
Carbon‐containing materials passing through a liquid or gaseous form during pyrolysis give graphitizable carbons. Materials that remain solid under pyrolysis conditions maintain their microstructural arrangement also under graphitization treatment conditions. Transitions between solid‐, liquid‐, and gas‐phase pyrolysis do exist and can result in partially graphitic regions after graphitization treatment.
Examples for a solid‐phase pyrolysis are chars derived from natural matter and glass‐like carbon derived from thermosetting resins. Due to the original structural disorder and impossibility of molecular rearrangement during pyrolysis, these materials do not graphitize.
Another industrially important example is polyacrylonitrile (PAN) based carbon fibers. PAN precursor
