Milling of Energetic Crystals with the LabRAM

Abstract

Processing energetic materials with the LabRAM acoustic mixer has been widely published; however, using it as a vibratory mill has only recently been explored. The size reduction of energetic crystals remains a tremendous processing challenge as it is often time and energy intensive. The LabRAM has the potential to reduce the time and energy required for milling through the use of low frequency waves. In this study, three distinct materials were selected to determine the effects of milling with the LabRAM. Ammonium perchlorate (AP), sodium periodate (NaIO4), and nitroguanidine (NQ) were chosen as their starting crystal morphologies are spherical, irregular, and needle‐like, respectively. The three materials were analyzed by laser particle analysis and scanning electron microscopy (SEM) to determine the average particle size and any morphology changes that may occur while milling. The average particle size, D50, of the starting materials, AP, NaIO4, and NQ were 253 μm, 415 μm, and 60 μm, respectively. The D50 after only 15 minutes of continuous milling for AP, NaIO4, and NQ was 7.01 μm, 2.92 μm, and 22.90 μm, respectively. This study focuses on the feasibility of safely dry milling micron‐size energetic crystals on the LabRAM acoustic mixer, while optimizing milling parameters for effective size reduction.

Mixed colors by combustion of mixed homogeneous pyrotechnics and heterogeneous charges

“…It was concluded for similarly shaped heterogeneous charges that a burning rate study should be performed to match the regression rates and optimize the interplume mixing [17]. The surface regression rates in this study [5] are in the 0.6–1.0⋅10 −3 m/s range for the compositions without NC, and in the 0.9–3.0⋅10 −3 m/s for NC‐based compositions.…”

Boron Carbide Based Biocide Compositions: A Study of Iodate Particle Size on Combustion and Iodine Output

“…These formulations provided adequate results, but iodine recovery was not substantial, and it was hypothesized that further reduction of the oxidizer could improve iodine recovery. Further reduction of NaIO 4 was done by vibratory milling using a Resodyn LabRAM following the procedure detailed by Kotter and Groven . The milled material was also sieved to further reduce the particle size and simultaneous DSC/TGA analysis was performed on neat NaIO 4 to observe the role of particle size on the decomposition pathway and early oxygen release.…”

Nitrocellulose‐Based Green‐Light Illuminants: A Study of Barium Nitrate Particle Size on Spectral Performance

“…During analysis, the average was taken every 10 seconds and a minimum of three runs were taken for each material. Averages were determined for each run with the particle distribution graphs containing both %Passing and % Channel data (see reference for % Passing and % Channel definitions) [18].…”

“…The milling media and container used was stainless steel media (1/8'') purchased from McMaster Carr (SKU: 9291K43) and clarified polypropylene containers (63 mm-6 oz) from ParkWay Plastics (SKU: A0630600PPC), respectively. In short, a crush ratio of 3 : 1, media to powder, and a mill time of 5-15 minutes at 40 g intensity was selected based off previous results [18]. The milled and � 25 μm were milled for a total of 15 minutes, a substantial 106-150 μm fraction was received after 10 minutes of milling and only 5 minutes of milling was required for the 250-300 μm fraction.…”

“…A size study performed by Fathollahi et al [9] highlighted not only the importance of particle size but how, when particles are irregular in morphology, there is localized energy at the jagged edges resulting in hotspot formation at these stress points. The preparation of irregular-shaped oxidizers can be performed by recrystallization as shown by Fathollahi [9] or by milling [18]. The irregular and variable size distribution of these oxidizers can provide both higher packing density and decreased thermal energy for combustion.…”