Effect of oxide coated thickness on thermal ignition of titanium-based pyrotechnics
The effect which variations in oxide coating thickness can have on thermal ignition of titanium-based pyrotechnics was examined theoretically. The analyses were developed using previously published experimental studies of ignition mechanisms. Those studies indicated that ignition is controlled by the rate at which an already existing oxide coating dissolves in the bulk metal. The specific case of hot-wire ignition at near minimum energy was considered. It was assumed that oxide dissolution occurs by molecular diffusion, and an approximate ignition model was developed to examine the relative variations in ignition times which result from variations in oxide coating thickness. The model consists of a heat conduction equation for the wire and pyrotechnic and a Fick's-law diffusion equation, with Arrhenius-type diffusion coefficient, for the oxygen in the titanium particles. Calculations showed that the ratio of ignition times t/sub i/sub 2///t/sub i/sub 1// could be estimated from t/sub i/sub 2///t/sub i/sub 1// approx. = (h/sub 2//h/sub 1/)/sup y/, where y = 2/(1 + Q/6 kcal mole/sup -1/); h/sub 2//h/sub 1/ is the respective ratio of oxide coating thicknesses, and Q is the oxygen-diffusion activation energy. Literature values for Q vary from 16 to 75 kcal/mole, while the exponent y varies from 0.6 to 0.2, respectively. At lower activation energies, moderate variations in oxide coating thickness could cause significant variations in ignition time.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6734293
- Report Number(s):
- SAND-84-0459C; CONF-840867-3; ON: DE84013061
- Resource Relation:
- Conference: 9. international protechnics seminar, Colorado Springs, CO, USA, 6 Aug 1984
- Country of Publication:
- United States
- Language:
- English
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