Properties of porous cast charges based on mixtures of ammonium nitrate and carbamide

Abstract

The explosive and physicochemical properties of porous mixtures based on ammonium nitrate, carbamide, and aluminum powder are considered. A melting curve for the ammonium nitrate/carbamide system is plotted using differential scanning calorimetry. The critical detonation diameter is obtained for a charge density of 0.6-0.7 g/cm 3 . The dependence of the charge density on the degree of filling of the mold with the melt is determined. Detonation velocity is measured for various densities. An explanation of the difference between the experimental and calculated values is proposed.Key words: eutectic mixture, ammonium nitrate, carbamide, vacuum formation, detonation velocity.Varying charge density is one of the main means for controlling important operation properties of explosive products such as detonation velocity and pressure. The design of new explosive materials with increased detonation velocity and pressure seeks to synthesize materials with crystal density close to ρ = 2 g/cm 3 , and in the manufacture of charges by molding, each hundredth of the density is of significance. However, many explosive engineering applications, for example, soft throwing, soft breaking of valuable rock, explosive processing of metals, etc., require charges with low detonation velocity and pressure and, hence, low density. The simplest method -manufacture of charges of bulk density -is not always convenient because the charge density can change during storage and transportation. This is especially true for ammonium nitrate charges.The explosive properties of condensed liquid porous charges of nitromethane and diethylene glycol dinitrate are described in [1], and the properties of cast porous TNT based charges prepared by melting TNT on a water bath with aeration or addition of fine aluminum and vacuum molding are described in [2]. The high melting point of ammonium nitrate (≈170 • C) does not allow one to use safe melting on a water bath and thus prepare cast porous charges.It is known from the literature that ammonium nitrate is capable of forming eutectic mixtures with materials such as carbamide, nitrates of the some amines, and some others. In the present work, this circumstance was used to reduce the melting point of ammonium nitrate and produce cast porous charges based on eutectic mixtures with carbamide.The physical and chemical properties of mixtures of ammonium nitrate with carbamide were studied by differential scanning calorimeter (DSC) using the Mettler Toledo DSC-30 device designed for the analysis of thermokinetic phase, chemical, and structural transformations, transitions in polymer compounds, halfproducts, materials, mixtures, alloys, ion-exchange materials in the temperature range from −170 to +600 • C.DSC is widely used to measure the endothermic effects of phase and modification transitions. Many enthalpies of melting of nitro compounds obtained by this method were brought into the extensive database of the U. S. National Institute of Standards and Technologies (NIST) and are available to users via the Interne...