Ti/C‐3Ni/Al as a Replacement Time Delay Composition

Abstract

AbstractReplacement reactive systems for the tungsten delay composition (W/BaCrO4/KClO4/diatomaceous earth) are needed due to recent concerns over the toxicity of hexavalent chromium and perchlorates. Systems based on condensed phase reactions, that are typically used in combustion synthesis (e.g., Ti/C or Ni/Al) are of interest as replacements due to their wide range of combustion velocities and potentially low environmental impact. In this work, the combustion characteristics of the Ti/C‐3Ni/Al reactive system were examined in microchannels with inner diameters ranging from 3.0–6.0 mm (i.e., similar to that of a common delay housing). It was found that this reactive system could be tailored to overcome the heat losses associated with small diameter microchannels by changing the relative amounts of Ti/C and 3Ni/Al. At 40 wt.‐% Ti/C content, the failure diameter was found to be between 3.0 and 4.0 mm, while at 30 wt.‐% Ti/C the failure diameter was between 4.8 and 6.0 mm. Measured combustion temperatures in metal microchannels were approximately 1700 K while those of unconfined pellets were around 100 K greater. Increasing Ti/C content resulted in faster combustion velocities while decreasing microchannel diameter resulted in slower combustion velocities. At these small sizes the effects of adding a thermal barrier (specifically Grafoil™) to minimize radial heat losses to the microchannel were shown to be minimal with respect to combustion velocity. The Ti/C‐3Ni/Al system was shown to be a suitable delay fuze composition with tunable combustion velocities ranging from 2.1–38.1 mm s−1 in aluminum microchannels with diameters ranging from 4.0–6.0 mm.