Recent work by Gupta and Shen [Appl. Phys Lett. 58, 583 (1991)] has shown that in a nonhydrostatic environment, the frequency of the ruby R, line provides a reliable measure of the mean stress or pressure. When using the frequency of either the R, or R, line to measure pressure at nonambient temperature, it is necessary to know the temperature dependence of the line shift. Unfortunately, the shift of the R2 line with temperature has not been reported. The ruby R i and R2 fluorescence shifts have been determined as a function of temperature from 15 to 600 K. Both can be fitted very well to the simple cubic forms R,(T) =14423+4.49~10-~T-4.81~10-~T~+3.71~10-'T~ cm-' and R2(T) = 14 452 $3.00~ 10m2T-3.88x 10e4T2+2.55x lo-'T3 cm-'. From 300 to 600 K the shifts fit well to linear functions of temperature. In addition, it is found that the RI-R2 splitting changes by about 3 cm-' over the 600 K temperature range. Linewidths were found to vary both with temperature and from sample to sample.

Articles you may be interested inShock initiation of the tri-amino-tri-nitro-benzene based explosive PBX 9502 cooled to −55 ° C The channel effect: Coupling of the detonation and the precursor shock wave by precompression of the explosive We have completed a series of ambient temperature ͑23±2°C͒ shock initiation experiments on four lots ͑batches͒ of the insensitive high explosive PBX 9502. PBX 9502 consists by weight of 95% dry-aminated tri-amino-tri-nitro-benzene ͑TATB͒ and 5% of the plastic binder Kel-F 800, a 3 / 1 copolymer of chloro-trifluoro-ethylene and vinylidene-fluoride. Two of the four lots were manufactured using the "virgin" process. Both of these lots had few fine TATB particles. One virgin lot was stored the majority of its life ͑Ͼ15 yr͒ as a molding powder and pressed as a 240 mm diameter by 130 mm thick cylinder. The other virgin lot was stored the majority of its life as a hollow hemispherical pressing. Two lots were manufactured using the "recycle" process and had many fine TATB particles. One recycled lot was stored the majority of its life as a molding powder, while the other was stored as a pressed charge. Shock initiation experiments were performed using precisely characterized planar shocks generated by impacting an explosive sample with a projectile accelerated in a two-stage gas gun. The evolution of the shock into a detonation was measured using 10 or 11 embedded electromagnetic particle velocity gauges and three "shock tracker" gauges. Results include the following: ͑1͒ high quality particle velocity wave forms which should be useful for calibrating reactive burn models, ͑2͒ no difference in the sustained shock initiation response between lots regardless of material processing or storage history, ͑3͒ responses for all lots equivalent to those measured by Dick et al. ͓J. Appl. Phys. 63, 4881 ͑1988͔͒, additional Hugoniot and Pop-plot data for PBX 9502, and ͑5͒ the short shock response which, when compared to the sustained shock response, shows no extension in the run distance unless the rarefaction overtakes the shock front prior to the distance it would have run towards a detonation as a sustained shock.

The detonation of carbon-rich high explosives yields solid carbon as a major constituent of the product mixture, and depending on the thermodynamic conditions behind the shock front, a variety of carbon allotropes and morphologies may form and evolve. We applied time-resolved small-angle X-ray scattering (TR-SAXS) to investigate the dynamics of carbon clustering during detonation of PBX 9502, an explosive composed of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) and 5 wt % fluoropolymer binder. Solid carbon formation was probed from 0.1 to 2.0 μs behind the detonation front and revealed rapid carbon cluster growth which reached a maximum after ∼200 ns. The late-time carbon clusters had a radius of gyration of 3.3 nm which is consistent with 8.4 nm diameter spherical particles and matched particle sizes of recovered products. Simulations using a clustering kinetics model were found to be in good agreement with the experimental measurements of cluster growth when invoking a freeze-out temperature, and temporal shift associated with the initial precipitation of solid carbon. Product densities from reactive flow models were compared to the electron density contrast obtained from TR-SAXS, and used to approximate the carbon cluster composition as a mixture of 20% highly ordered (diamond-like) and 80% disordered carbon forms, which will inform future product equation of state models for solid carbon in PBX 9502 detonation product mixtures.

Transit through the carbon liquid phase has significant consequences for the subsequent formation of solid nanocarbon detonation products. We report dynamic measurements of liquid carbon condensation and solidification into nano-onions over ∽200 ns by analysis of time-resolved, small-angle X-ray scattering data acquired during detonation of a hydrogen-free explosive, DNTF (3,4-bis(3-nitrofurazan-4-yl)furoxan). Further, thermochemical modeling predicts a direct liquid to solid graphite phase transition for DNTF products ~200 ns post-detonation. Solid detonation products were collected and characterized by high-resolution electron microscopy to confirm the abundance of carbon nano-onions with an average diameter of ∽10 nm, matching the dynamic measurements. We analyze other carbon-rich explosives by similar methods to systematically explore different regions of the carbon phase diagram traversed during detonation. Our results suggest a potential pathway to the efficient production of carbon nano-onions, while offering insight into the phase transformation kinetics of liquid carbon under extreme pressures and temperatures.

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