Combustion behaviour of single silicon particles in different oxidizing environments
Bibliographic record
Abstract
Silicon, despite its abundance and high energy density, remains underexplored as a carbon-free fuel, with limited data available on its combustion characteristics. In this work, the combustion behaviour of silicon particles is examined using an electrostatic levitator with laser ignition. Five oxidizing environments at atmospheric pressure are investigated: air, pure oxygen, and mixtures containing 40% oxygen (by mole) diluted with nitrogen, helium, or argon. The burning droplet peak temperature, measured by three-colour pyrometry, increases by 337 K from air to pure oxygen. The measured peak temperature of the silicon droplet in the 40%O 2 –60%He mixture is noticeably lower than that in the 40%O 2 –60%Ar mixture, in contradiction with thermodynamic predictions, due to a higher Lewis number of the helium-diluted mixture. Although oxygen diffusivity is higher in the helium-diluted mixture, a lower burning rate is observed, attributed to the lower combustion temperature. High-speed colour camera observations (with a resolution of about 1.25 μ m/px) reveal that the square of the particle diameter, d 2 , decreases with time, t , in each individual combustion run, following a strong linear relationship ( R 2 > 0 . 99 ) across all oxidizing environments. However, the combustion lifetime, τ c , and initial particle diameter, d i , follow a trend of τ c ∝ d i n , with n ranging from 1.69 to 1.82. This deviation from the expected n = 2 appears to result from unavoidable measurement uncertainties and the limited particle size range, rather than differences in combustion physics. The decrease in silicon droplet size during combustion is attributed to the formation of gaseous SiO as an intermediate combustion product. The SiO species is observed using a UV camera, showing a UV intensity decay from the particle surface. High-speed imaging and LED absorption signals indicate that the final condensed product, SiO 2 nanoparticles, are not optically visible, suggesting they possess very low emissivity. Novelty and significance statement We present the first experimental demonstration of ignition and complete combustion of single silicon particles, providing the first evidence that their combustion follows the classical d 2 law, unlike many previous studies on metal particles that reported deviations. The identified influence of Lewis number and particle size on combustion time, as well as the observed radiative properties of silicon combustion products, offers insights of scientific and engineering significance for developing combustion technologies using silicon as a carbon-free energy carrier.
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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".