Production of Submicrometer-Sized Hexahydro-1,3,5-trinitro-1,3,5-triazine by Drowning-Out

Abstract

In the drowning-out crystallization of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) with a spray, effects of operating parameters such as spray distance, solute concentration, and antisolvent temperature on crystal size were investigated. It was found that there exists an optimum spraying distance of solution for the production of submicrometer-sized crystals: the crystal size decreases with increasing spray distance in the distance shorter than the optimum distance due to incomplete atomization and that increases with the spray distance at the distance longer than the optimum distance due to coalescence among fluttered droplets. Higher RDX concentration in starting solution induced larger product particles. However, too low RDX concentration was also found to be not preferred for the small-sized product since nucleation occurs after complete mixing of atomized solution droplets with the antisolvent. By similar reason, it was found that lower antisolvent temperature, which causes faster nucleation, is preferred for the small-sized product. However, too low temperature was shown to be not preferred because of an increase in coalescence between droplets which leads to agglomeration. Finally, poly­(vinylpyrrolidone) (PVP) was found to act as a nucleation promoter in the drowning-out crystallization with the acetone/water system, and RDX particles with an average size of 790 nm were successfully produced.

New Strategy for the Morphology-Controlled Synthesis of V2O5 Microcrystals with Enhanced Capacitance as Battery-type Supercapacitor Electrodes

“…For instance, a thermal evaporation method was used to synthesize layered-structure nanoribbons; electrodeposition was used to obtain three-dimensional (3D) porous V 2 O 5 hollow spheres; a spray pyrolysis method was employed to produce V 2 O 5 with various porous structures, etc. Among them, the hydrothermal reaction is the most commonly used method due to its facile conditions, and the morphology of the products can be well controlled, while templates were usually needed to fabricate special morphologies and the products were normally nanomaterials. , Drowning-out crystallization is an effective method to get pure crystals through the recrystallization by adding antisolvent in the generated supersaturated solution to reduce the solubility of the solute in the component solvent, and it is possible to control the morphology and size of the crystals by changing kinetic factors like the amount of antisolvent, concentration of the solute, and the crystallization temperature. , According to the above discussion, it is necessary to develop a new synthetic method that can produce a series of materials with different morphologies, so the systematic analysis of the relations between the morphologies of materials and their electrochemical performance can be performed. In this contribution, an innovative, effective, and environmentally friendly strategy that combines the hydrothermal method and the drowning-out crystallization, along with the subsequent thermal treatment, was developed to synthesize porous V 2 O 5 microcrystals with three different morphologies.…”

Formation of Spherical Agglomerates in Cooling Crystallization of Hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine

“…RDX particles were prepared by a spray nozzle‐assisted drowning‐out method . The theoretical number of particles in acetone was calculated by assuming the density to be equal to 1.4 g cm −3 .…”

“…Previously, it was stated that PVP molecules are penetrated and incorporated into the cluster of RDX molecules from the aggregation pattern digitized by molecular simulation , . The PVP molecules provide suitable sites for primary nucleation even when PVP molecules are included.…”

“…The target system was batch cooling crystallization of hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) from acetone with a small quantity of PVP. The RDX‐acetone‐PVP system is quite similar to a paracetamol‐ethanol‐water‐PVP system since PVP is a retarder for both the nucleation and crystal growth of RDX in an acetone solution , . In particular, cooling crystallization is much simpler than drowning‐out because of the absence of any effect due to the mixing of solution with the antisolvent.…”

Process Research of Solution‐Enhanced Dispersion by Supercritical Fluids to Prepare Energetic Material Nano‐Capsules

“…In the two‐step process, the energetic materials are first refined and then coated to form microcapsules. Common refining methods include anti‐solvent injection [5], spray drying [6–9], supercritical RESS [10–12], supercritical SAS [13, 14], and physical ball milling, among others. Coating methods include coating by water suspension [15–20], coating by a supercritical fluid [11, 21–28], coating by spray drying [29, 30], and coating by ball milling [31, 32].…”