Abstract
Currently, artillery shells and grenades that are introduced into the market are based on melt-castable insensitive high explosives (IHEs), which do not explode while they run a risk of impact, heat or shrapnel. Particles of explosives (such as hexogen, nitroguanidine and nitrotriazolone) are suspended in different proportions in a matrix of 2.4-dinitroanisole. In this paper, we investigated samples of commonly used IHEs: PAX-41, IMX-104 and IMX-101, whose internal structures were determined by a scanning electron microscope. Terahertz time domain spectroscopy was applied in both transmission and reflection configurations. At first, the complex refraction indices of four pure constituents creating IHEs were determined and became the basis of further calculations. Next, the experimentally determined transmission and reflection spectra of IHEs and pure constituents were compared with theoretical considerations. The influence of the grain size of constituent material and scattering on the reflection spectra was analysed, and good agreement between the experimental and theoretical data was achieved.
Highlights
Melt-castable explosive materials are used to manufacture artillery shells
The good agreement between the measurement and the calculation proved that the features appearing in the absorption and the refractive index characteristics can be understood from the sum of the constituents
The absorption peaks are connected with the slopes of the refractive index (Fig. 4) as was proven for two well-known and popular explosives (RDX and NQ) and two materials seldom investigated in the terahertz domain (NTO and DNAN)
Summary
Melt-castable explosive materials are used to manufacture artillery shells. Until now, pure explosives, e.g. 1,3,5-trinitro-1,3,5-triazacyclohexane (known as RDX), have been mixed with 2,4,6-trinitrotoluene (TNT) and melted by the application of heat. With regard to quite big attenuation (∼100–300 cm−1) [6], practical applications are limited to rare situations such as measurements of the thin layer of the powder placed in the envelope For this reason, all samples prepared to transmission measurements are in the form of pressed pellets consisting of material with good transmission in the terahertz range (such as polyethylene) with suspended explosive material particles with a concentration of 5–20 %, which allows for proper determination of absorption characteristics [6] but ensures sufficient transparency. Samples for reflection measurements are mostly manufactured in the form of pressed pellets but consisting of pure explosive material powder, sometimes with a few per cent addition of desynthesizer [7]. Samples were prepared as pressed pellets and melt-castable discs Their surface morphology and grain sizes were determined by means of a scanning electron microscope (SEM). Images from SEM investigations help to draw conclusions about the phenomena taking place during the reflection
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