Comparison of properties of carbon particles formed by pyrolysis of C3O2 and C2H2 behind shock waves

Abstract

Various carbon particles formed by the pyrolysis of C3O2 and C2H2 behind shock waves in the temperature range 1200–3800 K are studied. The formation of the condensed carbon particles is observed directly by the multichannel detection of the time profiles of the extinction of the medium in the UV, visible, and near-IR spectral regions. The samples of carbon material deposited on the walls of a shock tube after an experiment are analyzed using transmission electron microscopy with different resolutions and electron microdiffraction. Particles formed from C3O2 and C2H2 at 1500–2000 K are 10–30 nm in size and look like usual soot. The absence of molecular hydrogen in C3O2 only results in faster formation and graphitization. At 2100–2600 K, the formation of particles is retarded, and the yield of the carbon particles decreases for both substances. After experiments on pyrolysis of C3O2 at these temperatures, giant spherical particles up to 700 nm in size are found on the walls of the shock tube. Carbon particles formed at the highest temperatures (2700–3200 K) in C3O2 pyrolysis have the high degree of crystallinity of particles.