From Asphaltenes and Coals to Carbons: Interpreting the Transition from X-ray Scattering to Crystalline Diffraction
Bibliographic record
Abstract
One of the first instrumental techniques applied to asphaltenes and coal to obtain structural information was X-ray diffraction. The broad asymmetric peaks were interpreted on the basis of the graphite crystalline structure, and the resulting lattice spacings and crystallite dimensions have been published regularly for over 60 years. This review examines the basis for this analytical method and tests the underlying assumptions and hypotheses by comparison to X-ray patterns from model compounds and amorphous polymers. These comparisons show that the X-ray patterns of complex asphaltenes are dominated by inter- and intramolecular scattering and that the published methods to quantitatively analyze these data are invalid. High-temperature processing of asphaltenes and coals can give higher order X-ray peaks consistent with graphite, but prior to this, the structural information is highly ambiguous. The use of full width at half maximum for the broad signal from 10° to 30° is recommended for tracking thermal conversion reactions of such highly complex materials as asphaltenes and coal, to avoid unjustified assumptions of the crystalline structure.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".