The influence of two selected bistetrazoles, 5,5′‐bis(1H‐tetrazolyl)‐amine (BTA) and 5,5′‐hydrazinebistetrazole (HBT), on the combustion behavior of a typical triple‐base propellant was investigated. Seven propellant formulations, one reference and six others incorporating 5 %, 15 %, and 25 % of either HBT or BTA compounds, respectively, were mixed and extruded into a cylindrical, no perforations, geometry. The resulting propellants showed high burning rates, up to 93 % higher than the reference formulation at 100 MPa. However, the increase in burning rates came at the cost of higher burning rate dependency on pressure, with a pressure exponent as high as 1.4 for certain formulations. HBT‐containing propellants showed notably lower flame temperature when compared to the reference formulation, with a flame temperature reduction of up to 461 K for the propellant containing 25 % HBT. The thermal behavior of the propellants was also investigated through DSC experiments. The addition of bistetrazoles provided lower decomposition temperatures than the pure nitrogen‐rich materials, indicating that the two compounds probably react readily with the −ONO2 groups present in the nitrocellulose and the plasticizers used in the formulation. The onset temperature of all propellants remained within acceptable ranges despite the observed decrease caused by the addition of the bistetrazole compounds.

No abstract

Nanothermites can provide high energy densities and reaction rates but can also display extreme friction sensitivities. Additives that provide friction modification offer the potential to reduce the friction sensitivity of nanothermites. In the present work, MoS 2 , graphene, and hexadecane additives were dispersed in MoO 3 prior to nanothermite formation with the aim of reducing friction sensitivity. Nanothermites were subsequently prepared using a palmitic acid-passivated nano-aluminum (L-Al) and additive-containing nano-MoO 3 by the resonant acoustic mixing of dry powders. In general, the incorporation of additives results in a reduction in friction sensitivity with the baseline minimum ignition friction rising from 10 to 120 N using 0.5% wt/wt micrometer-sized MoS 2 or 5% wt/wt hexadecane. However, the relationships between loading and performance are complex and vary by additive; for example, the friction sensitivity dependence using micrometer-diameter MoS 2 displays a maximum at 0.5% wt/wt and declines to 7 N using 5% MoS 2 .

Five propellant formulations were test fired both in a vented vessel and a closed vessel. Two formulations contained 35 % weight of nitrogen‐rich materials. The erosion by weight of the propellants ranged from 0.53 g to 1.31 g after two consecutive test firings of a given propellant. The addition of nitrogen‐rich materials resulted in reduced erosion. Scanning electron microscope and energy dispersive X‐ray spectroscopy revealed nitrogen in the erosion pieces for one of the reference propellants (SB) and the two nitrogen‐rich propellants. The two hottest propellants cause melting of the erosion pieces. The presence of nitrogen‐rich materials has a tremendous impact on the burning rates with the burning rate increase at 100 MPa reaching up to 2.4 times that of the formulation used as the base for the nitrogen‐rich propellants.

The performance of a small-caliber propellant is influenced by many factors. Foremost is the chemical composition, however, other factors such as the physical properties of the propellant, the weapon system, and the operating conditions can also greatly influence the performance of a propellant. In this study, researchers investigated the influence of particle size and temperature on the performance of small caliber, ball powder propellant. Particle size is important as it provides the initial surface area available for a propellant to begin the deflagration process. The geometry of the grain will dictate how the deflagration pro-gresses: progressively, regressively, or neutral. The initial temperature of the propellant also has a direct influence on propellant performance. Evaluations were conducted in a constant volume, a temperature-controlled closed vessel to obtain pressure-time data for the various experiments. The data coupled with the propellant thermochemical properties were used to calculate the burning rate coefficient (β) and pressure exponent (α) of the propellant. Dynamic vivacity, relative force, and relative quickness values are also reported.