High-speed Optical Imaging Technique for Combusting Metal Nanopowders

This paper discusses a technique for studying laser initiation and combustion of high-energy materials in real time using a two-channel video recording system. Traditional high-speed imaging is used as one channel, and a brightness-amplified laser projection system (laser monitor) is used as the second channel. The synchronization of laser ignition and high-speed imaging of the flame and the sample surface is considered in detail. The rela-tionship between the propagation of the flame glow and the change in the surface of the nanoAl + MnO2 thermite mixture during combustion has been established. A method of simultaneous high-speed recording of images of a laser monitor by two cameras with different recording frame rates is proposed to provide the possibility of studying the initial stage of combustion and the entire combustion process of the same nanopowder sample with different temporal and spatial resolutions. Imaging of the surface of nanoAl + MnO2 thermite mixtures at a recording frame rate of 20,000 fps has been implemented using a laser monitor. The possibility of determining the propagation velocity of the combustion wave on the surface of the sample is demonstrated to be up to 85 mm/s. The influence of the exposure time of a high-speed camera on the image quality of a laser monitor is investigated. It is demonstrated that the image quality is almost the same for the images formed by 1-9 emission pulses of the brightness amplifier.