Pentaerythritol tetranitrate (PETN) is one of the most commonly used explosives for both military and mining applications. PETN is used in EBW (exploding bridge wire) and EFI (exploding foil initiator) detonator devices. Due the widespread usage of PETN, studies focusing on how the explosive changes with age, primarily its function in detonators has received particular interest. Aging studies have identified several factors that affect PETN detonator function over time, most notably the specific surface area of the explosive powder. Though small-scale studies have been performed on specific detonator systems with isolated batches of material, what is missing is a large statistically-significant study focusing on PETN aging characteristics-such as powder coarsening-and their influence on detonator performance. Herein we report the first large statistically viable PETN aging study focusing on four batches of PETN powder from the same stock of PETN using two stabilizers, polysaccharide and TriPEON. PETN was aged both as a free-flowing powder as well as in modified EBW RP-2 detonators, for one month at 75°C. The PETN powder has been analyzed chemically using Fisher specific surface area analysis, SEM imaging and light scattering particle size analysis. Additionally the detonators were tested for performance through voltage-sweep threshold testing and function time measurements. Findings from the study indicate that aging at 75°C for one month significantly changes the specific surface area and particle size of unstabilized PETN, leading to increases in detonator function time, but not detonator threshold values. Powders stabilized with TriPEON displayed less significant increases in function time, while powder stabilized with polysaccharide exhibited no aging effects, despite the high temperature aging.
While
bulk gold is generally considered to be a catalytically inactive
material, nanostructured forms of gold can in fact be highly catalytically
active. However, few methods exist for preparing high-purity macroscopic
forms of catalytically active gold. In this work, we describe the
synthesis of catalytically active macroscopic nanoporous gold foams
via combustion synthesis of gold bis(tetrazolato)amine complexes.
The resulting metallically pure porous gold nanoarchitectures exhibit
bulk densities of <0.1 g/cm3 and Brunauer–Emmett–Teller
(BET) surface areas as high as 10.9 m2/g, making them among
the lowest-density and highest-surface-area monolithic forms of gold
produced to date. Thanks to the presence of a highly nanostructured
gold surface, such gold nanofoams have also been found to be highly
catalytically active toward thermal chemical vapor deposition (CVD)
growth of carbon nanotubes, providing a novel method for direct synthesis
of carbon nanostructures on macroscopic gold substrates. In contrast,
analogous copper nanofoams were found to be catalytically inactive
toward the growth of graphitic nanostructures under the same synthesis
conditions, highlighting the unusually high catalytic propensity of
this form factor of gold. The combustion synthesis process described
herein represents a never-wet approach for directly synthesizing macroscopic
catalytically active gold. Unlike sol–gel and dealloying approaches,
combustion synthesis eliminates the time-consuming diffusion-mediated
steps associated with previous methods and offers multiple degrees
of freedom for tuning morphology, electrical conductivity, and mechanical
properties.
The aging of high
explosives in an ionizing radiation field is
not well understood, and little work has been done in the low dose
and low dose rate regime. In this study, four explosives were exposed
to low-level gamma irradiation from a 137Cs source: PETN,
PATO, and PBX 9501 both with and without the Irganox 1010 stabilizer.
Post-irradiation analysis included GC–MS of the headspace gas,
SEM of the pellets and powder, NMR spectroscopy, DSC analysis, impact
sensitivity tests, and ESD sensitivity tests. Overall, no significant
change to the materials was seen for the dose and dose rate explored
in this study. A small change in the 1H NMR spectrum of
PETN was observed and SEM and ESD results suggest a surface energy
change in PATO, but these differences are minor and do not appear
to have a substantial impact on the handling safety.
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