(493e) Milling of Energetic Crystals with the Labram

Milling of Energetic Crystals with
the LabRAM

Lance N. Kotter^a
and Lori J. Groven^b,*

^aSouth Dakota School of Mines and
Technology, Department of Material Science and Engineering, Rapid City, SD, US

^bSouth Dakota School of Mines and
Technology, Department of Chemical and Biological Engineering, Rapid City, SD,
US

*corresponding author email:
lori.groven@sdsmt.edu

            The
LabRAM acoustic mixer has widely been used for mixing and processing of
energetic materials from propellant mixes, explosive-binder formulations, to
cocrystal synthesis.  It was only very
recently that it has demonstrated utility in the field of general material
processing such as sieving.  Size
reduction of energetic crystals remains a tremendous processing challenge and
is often time and energy intensive. 
While milling is used extensively to reduce/grind/modify fuel and
oxidizer type materials the LabRAM has not been explored specifically
for that purpose.  The ability for the
LabRAM to be controlled remotely while providing low intensity acoustic waves
(60 Hz) makes it a suitable candidate for the milling of energetic crystals. In
this study, three distinct materials were selected to determine the effective
milling of the LabRAM. Ammonium Perchlorate (AP) as a highly sought after
energetic with distinct spherical morphology, Sodium Periodate as an irregular
crystal that has shown effectiveness in biocidal formulations, and
Nitroguanidine for its interest in energetic formulations while having rod-like
morphology.    In this
study, dry milling of all materials was performed on the LabRAM while
optimizing parameters such as media size and loading, vibrational intensity,
and time duration. The three materials were analyzed by laser particle analysis
and SEM to determine the average particle. The D₅₀ after 15 minutes
of continuous milling for Ammonium Perchlorate, Sodium Periodate, and Nitroguanidine
were 7.01, 2.92, and 22.90 µm respectively. 
In the case of AP this was a reduction of the measured D₅₀
from around 250 to 7 µm in as little as 15 minutes.  The processing technique has the potential to
allow for wet grinding as well or significant particle morphology modification
and will be discussed.