Carbon-based thin films deposited on surfaces exposed to a typical capacitively-coupled RF plasma are sources of molecular precursors at the origin of nanoparticle growth. This growth leads to drastic changes of the plasma characteristics. Thus, a precise understanding of the dusty plasma structure and dynamics is required to control the plasma evolution and the nanoparticle growth. Optical diagnostics can reveal some particular features occurring in these kinds of plasmas. High-speed imaging of the plasma glow shows that instabilities induced by nanoparticle growth can be constituted of small brighter plasma regions (plasmoids) that rotate around the electrodes. A single bigger region of enhanced emission is also of particular interest: the void, a main central dust-free region, has very distinct plasma properties than the surrounding dusty region. This particularity is emphasized using optical emission spectroscopy with spatiotemporal resolution. Emission profiles are obtained for the buffer gas and the carbonaceous molecules giving insights on the changes of the electron energy distribution function during dust particle growth. Dense clouds of nanoparticles are shown to be easily formed from two different thin films, one constituted of polymer and the other one created by the plasma decomposition of ethanol.
Ignition and combustion characteristics of a low‐vulnerability propellant mainly composed of nitrocellulose are studied experimentally. Ignition is obtained using a 10 W laser diode. Experiments are performed in a cylindrical closed‐volume reactor for different initial pressures and initial propellant masses under nitrogen and argon surrounding atmospheres. Ignition delays, maximal overpressures and propagation rates are obtained for different initial pressures and laser powers. Ignition probabilities for different laser powers and gaseous atmospheres are also investigated using the modified Langlie method. Argon is found to be a combustion enhancer for this kind of propellant, compared to nitrogen. Laser power plays a significant role on ignition probabilities and ignition delays, but not on propagation rates. As expected, ignition delay is highly dependent on initial pressure.
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