Thermodynamic analysis of pure and impurity doped pentaerythritol tetranitrate crystals grown at room temperature

Abstract

Pentaerythritol tetranitrate (PETN) powders are used to initiate other explosives. During longterm storage, changes in powder properties can cause changes in the initiation performance. Changes in the morphology and surface area of aging powders are observed due to sublimation and growth of PETN crystals through coarsening mechanisms, (e.g. Ostwald ripening, sintering, etc.). In order to alleviate the sublimation of PETN crystals under service conditions, stabilization methods such as thermal cycling and doping with certain impurities during or after the crystallization of PETN have been proposed.In this report we present our work on the effect of impurities on the morphology and activation energy of the PETN crystals. The pure and impurity doped crystals of PETN were grown from supersaturated acetone solution by solvent evaporation technique at room temperature. The difference in the morphology of the impurity-doped PETN crystal compared to pure crystal was examined by optical microscopy. The changes in the activation energies and the evaporation rates are determined by thermogravimetric (TGA) analyses. Our activation energies of evaporation agree with earlier reported enthalpies of vaporization. The morphology and activation energy of PETN crystals doped with Ca, Na, and Fe cations are similar to that for pure PETN crystal, whereas the Zn-ion-doped PETN crystals have different morphology and decreased activation energy.

Effect of Zn doping on the sublimation rate of pentaerythritol tetranitrate using atomic force microscopy

“…This value of activation energy for pure PETN is similar to literature values (Burnham et al 2009;Pitchimani et al 2007a). The decrease of activation energy due to doping of Zn ion is consistent with the result found by Pitchimani et al (2007c) for PETN crystal. As the doping concentration increases beyond a certain limit (1,000 ppm) activation energy and A parameter increase again with increasing Zn doping concentration.…”

“…A small amount of nitro compound, such as mono-, di-, and trinitrobenzenes, result in decrease in stability at elevated temperatures (Bourjol 1953;Urbanski et al 1935), whereas the addition of small amount of urea stabilizes PETN (WestfalischAnhaltische Sprengstoff 1940). Among the metal ions, Zn was found to be an ideal impurity which when added in a small amount does not change the crystal structure or interact with PETN but changes the surface morphology, evaporation rate, and activation energy (Pitchimani et al 2007b; Pitchimani et al 2007c). In the present study, we have investigated the effect of Zn ion doping concentrations on sublimation rates and activation energy of evaporation of PETN thin films using AFM.…”

Sublimation Properties of Pentaerythritol Tetranitrate Single Crystals Doped with Its Homologs

“…Pitchimani et al. showed that doping with inorganic salt changed the evaporation rate as well as Arrhenius parameters 30. Rogers et al.…”

Effect of Homolog Doping on Surface Morphology and Mass‐Loss Rates from PETN Crystals: Studies using Atomic Force Microscope and Thermogravimetric Analysis

“…Atomic force microscopy (AFM) imaging has revealed morphological changes in the growth center in the presence of impurities [8][9][10]. Impurities have also been shown to alter the thermodynamic properties of singles crystals [11].…”

“…Keywords: Single crystal · PETN · Doping · Impurities · Mass-Loss rate · Morphology ous works have demonstrated that doping with appropriate compounds can control such aging process of PETN [11,17,18]. For instance, it was shown that doping with homologs like dipentaerythritol hexanitrate (diPEHN) and tripentaerythritol octanitrate (triPEON) can lower the vapor pressure of PETN single crystals [19].…”