Towards understanding the catalytic properties of lead-based ballistic modifiers in double base propellants
Bibliographic record
Abstract
Lead-based ballistic modifiers are additives in double base propellants (DBPs) which render the burn rate insensitive to changes in pressure within a defined pressure range, thus imparting greater control of combustion conditions. In-coming European legislation will soon ban the use of lead in propellant formulations, however, and few suitable candidate replacement materials are currently available. In an effort to understand better the unique properties offered by lead-based modifiers, we present a first-principles computational study on Pb, PbO, PbO2, SnO2 and Bi2O3, all of which have been investigated experimentally as ballistic modifier materials. Our study demonstrates that various quantifiable properties exist for the lead-based materials. Overall, they have narrower electronic band gaps, lower surface energies and lower surface work functions than the lead-free systems, indicating a greater propensity to form stable chemical surfaces with higher catalytic activity. We also show that of the set, only Pb and α-PbO can support the formation of a weakly bound layer of amorphous carbon, a key experimental observable in the burning of DBPs.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".