Mixing Si and carbon nanotubes by a method of ball-milling and its application to pyrotechnic delay composition

The original delay composition cannot ensure the reliability and safety of the ammunition under complicated environment, for example low precision of burning rate at high density charge. Carbon nanotubes are added into the delay composition for the first time. Si and CNTs were mixed by the ball-milling method. Particle size analysis showed that particle size exponential declined with increase in milling time. TEM showed that individual nanotubes were dispersed in silicon powder after 48 h of milling, and then they did not appear damaged. Optimum conditions of preparing Si/CNTs were found to be: milling time 48 h, milling intensity 300 rpm, CNTs-to-Si weight ratio=1:10 and ball-to-powder weight ratio=150:1. Then Si/CNTs were applied to fuel agent of delay composition. We studied the burning rate of Pb₃O₄/Si and Pb₃O₄/CNTs/Si delay composition with flaming velocity measurement. Results show that burning rate and delay precision of Pb₃O₄/CNTs/Si delay composition (5.85 mm/s and 1.03%) were higher than the ones of Pb₃O₄/Si delay composition (3.80 mm/s and 3.00%). Especially reliability of ignition is improved when charge density exceeds 6000 Kg/m³. It is proved that certain amount of CNTs added to delay composition can increase delay precision and further doing so achieved less temperature dependence.