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Classification scheme based on the atomic percentage (at%) used to distinguish particle types based on their elemental composition.
| Classes | Ti [at%] | Cl [at%] | Si [at%] | Na [at%] | Ca [at%] | Al [at%] | C [at%] |
|---|---|---|---|---|---|---|---|
| Ti-based | ≥5 | – | – | – | – | – | – |
| Si-based | – | – | ≥5 | – | – | – | – |
| NaCl | – | ≥5 | – | ≥5 | – | – | – |
| Ca-based | – | – | – | – | ≥5 | – | – |
| Al-based | – | – | – | – | – | ≥25 | – |
| C-based | – | – | – | – | – | – | ≥70 |
| Unclassified | <5 | <5 | <5 | <5 | <5 | <25 | <70 |
