Chemical stability of molten 2,4,6-trinitrotoluene at high pressure

Abstract

2,4,6-trinitrotoluene (TNT) is a molecular explosive that exhibits chemical stability in the molten phase at ambient pressure. A combination of visual, spectroscopic, and structural (x-ray diffraction) methods coupled to high pressure, resistively heated diamond anvil cells was used to determine the melt and decomposition boundaries to >15 GPa. The chemical stability of molten TNT was found to be limited, existing in a small domain of pressure-temperature conditions below 2 GPa. Decomposition dominates the phase diagram at high temperatures beyond 6 GPa. From the calculated bulk temperature rise, we conclude that it is unlikely that TNT melts on its principal Hugoniot.

Review of Phase Transformations in Energetic Materials as a Function of Pressure and Temperature

“…Unlike at ambient pressure, the difference in the melting and the decomposition temperatures narrowed at high pressures, and TNT was found to decompose rather than melt when heated under pressures above 6 GPa. 60 This is similar to other explosives such as HMX and PETN.…”

“…Dattelbaum et al carried out a detailed study of the high-pressure melting line and chemical stability of molten TNT in a resistively heated diamond anvil cell (DAC), and their studies have shown a steep melt boundary of 61 K/GPa up to 2 GPa (Figure ). Unlike at ambient pressure, the difference in the melting and the decomposition temperatures narrowed at high pressures, and TNT was found to decompose rather than melt when heated under pressures above 6 GPa . This is similar to other explosives such as HMX and PETN.…”

“…59 The bulk modulus (K 0 ) of the monoclinic phase was determined from the P−V curve using a Murnaghan equation of state analysis, resulting in a low value, K 0 = 8.52 GPa, that is consistent with the weak intermolecular interactions in TNT. Dattelbaum et al 60 carried out a detailed study of the highpressure melting line and chemical stability of molten TNT in a resistively heated diamond anvil cell (DAC), and their studies have shown a steep melt boundary of 61 K/GPa up to 2 GPa (Figure 6). Unlike at ambient pressure, the difference in the melting and the decomposition temperatures narrowed at high pressures, and TNT was found to decompose rather than melt when heated under pressures above 6 GPa.…”

A New Multiphase Equation of State for Composition B

“…It was impossible to determine whether the two points at higher pressure (where agreement with our EOS is not as good) were melted, chemically decomposed, or some combination. 28 As has been noted, 28 the melt line is quite steep (∼80 K/GPa). At this point we reiterate that this is the melt line of pure TNT, and that its precise relation to constitutive properties of Comp B is not straightforward.…”

“…The combination of our EOS predict von Neumann spike and CJ pressures of 40.1 GPa and 28.9 GPa, respectively. The TNT melt line was recently measured to high accuracy by Dattelbaum, et al 28 We compare these data with 95500 results in Figure 3. Once again we find good agreement, particularly at lower pressures.…”