Picric acid is known to react with metals to form highly unstable metallic picrates, which are known to have been involved in serious explosive accidents. In this study, transition-metal picrates of chromium, manganese, cobalt and nickel salts are synthesized, and the thermodynamic and explosive properties (for example, initiation sensitivity) are examined.
The decomposition of Mn-picrate or Co-picrate determined through differential scanning calorimetry (DSC) begins at a lower temperature than that of picric acid, and the heat of decomposition of transition-metal picrates is found to be lower than that of picric acid. Thermogravimetry and Karl Fischer analysis confirm that transition-metal picrates contain crystal water, and the amount of crystal water in metastable-phase picrates is determined experimentally. Thermogravimetric analysis reveals that crystal water begins to dehydrate in a temperature range extending from slightly above room temperature to approximately 470 K. The activation energies of the decomposition reaction of these transition-metal picrates are 204.1 kJmol-1 for Cr-picrate, 108.1 kJmol-1 for Mn-picrate, 132.3 kJmol-1 for Co-picrate, and 184.3 kJmol-1 for Ni-picrate. Drop-hammer test results show that Cr-picrate has higher strike sensitivity than picric acid, and friction tests reveal that all of the transition metal-picrates examined here have equal or lower friction sensitivity compared to picric acid.

Picric acid is known to react with metals to form highly unstable metallic picrates, which have been implicated in a number of serious explosive accidents. In this study, lead picrates were synthesized by several methods, and the thermodynamic and explosive properties such as sensitivity were examined. Differential scanning calorimetry (DSC) results revealed that lead picrates had several heat decomposition patterns depending on the synthesis method, and they had lower temperature of start of exothermic reaction than sodium picrate had. The heat of decomposition of lead picrates was found to be lower than that of picric acid. Lead picrate from lead acetate and picric acid had lower activation energy of thermal decomposition than the other lead picrates. Thermogravimetry analysis and Karl Fischer analysis confirmed that lead picrates contained crystalline H2O, which dehydrated at above 375 K. And, lead picrates did not have property of fusion. Drop hammer test results showed that lead picrates had high strike sensitivity, whereas the lead picrates had low friction sensitivity in friction tests, attributable to the presence of crystalline H2O. The ignition temperatures of lead picrates were found to be in the range 543.9–600.3 K.

A mixture of tri-n-butyl phosphate (TBP) and nitric acid is used in the PUREX method for reprocessing nuclear fuel, and is performed safely. However, when fuming nitric acid (FNA) is employed, it behaves like a liquid explosive. In the present study, the explosion strength of TBP/FNA mixture was evaluated by underwater explosion tests. Shock wave energy, bubble energy, and total energy of detonation were determined. The explosion strength reaches a maximum and decreases as the mixture ratio deviates from stoichiometric. It was demonstrated that heat of detonation of TBP/FNA that determined from thermochemical calculation was consistent with total energy that determined from underwater explosion test.

Breaking rocks and concrete accompanies ultrasonic waves called acoustic emission. Since generation and extension of cracks causes the acoustic emission, their locations help to clarify the breaking mechanism. In this paper, the breaking mechanism of a 200 mm cubic mortar specimen by rapid type of expansive cement agent was investigated by locating acoustic emissions. At the first stage when expansive pressure of the cement agent increased gradually, acoustic emissions were distributed around the center hole of the specimen in which the cement agent was filled. At the second stage while the expansive pressure started to increase intensively and reached its maximum, they clustered near a surface on the one side of the specimen, in contrast to the distribution near the center hole at the first stage. Finally, at the third stage while visual cracks appeared and separated the specimen completely, they distributed along the cracks.

This short note proposes a concept of two stage accelerator which can attain more than 4 km/s with fairly high acceleration level under the condition of tolerable heat damage of accelerator tube. Here the electro-magnetically pre-accelerated projectile with a charge by a composite armature is further accelerated by the pressure and the jet thrust of the ignited charge. The ignition of travelling charge is performed by the ohmical explosion of a metallic filament in the composite armature at a pre-determined moment. A possiblity of this ignition is discussed briefly with a result from a basic experiment.