Laser-Induced Modification of Hydrogenated Detonation Nanodiamonds in Ethanol
Irena BydzovskaEkaterina ShagievaIvan GordeevO. RomanyukZuzana NěmečkováJiří HenychLukáš OndičAlexander KromkaŠtěpán Stehlík
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Apart from the frequently used high-temperature annealing of detonation nanodiamonds (DNDs) in an inert environment, laser irradiation of DNDs in a liquid can be effectively used for onion-like carbon (OLC) formation. Here, we used fully de-aggregated hydrogenated DNDs (H-DNDs) dispersed in ethanol, which were irradiated for up to 60 min using a 532 nm NdYAG laser with an energy of 150 mJ in a pulse (5 J/cm2) at a pulse duration of 10 ns and a repetition rate of 10 Hz. We investigated the DND surface chemistry, zeta potential, and structure as a function of laser irradiation time. Infrared spectroscopy revealed a monotonical decrease in the C–Hx band intensities and an increase of the C–O and C=O features. Transmission electron microscopy (TEM) revealed the formation of OLC, as well as a gradual loss of nanoparticle character, with increasing irradiation time. Surprisingly, for samples irradiated up to 40 min, the typical and unchanged DND Raman spectrum was recovered after their annealing in air at 450 °C for 300 min. This finding indicates the inhomogeneous sp3 to sp2 carbon transformation during laser irradiation, as well as the insensitivity of DND Raman spectra to surface chemistry, size, and transient structural changes.Keywords:
Zeta potential
Abstract As a promising method for synthesizing nanosized materials, detonation method was used to prepare TiO 2 nanoparticles. A new method for predicting the Chapman‐Jouguet (C‐J) detonation parameters of C a H b O c N d Ti e explosives, such as detonation heat, detonation temperature, and detonation pressure, was introduced according to the approximate reaction equations of detonation. The coefficient of oxygen balance of explosive was also calculated according to the specific detonation synthesis experiment. The calculation method was more useful in predicting the formation processes of detonation products and optimizing the experimental procedure. It could also support theory foundation for further experiments to some extent.
Nanocrystalline material
Oxygen balance
Detonation velocity
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Mach reflection
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WT5”BZ]The comparative experimental study on the single detonation wave of an ethyne air mixture under various conditions was made.The effect of the detonation chamber closeness on the detonation wave formation was studied.It was found that the developed detonation wave (CJ detonation) was produced when the detonation chamber was completely closed,but the strength of the detonation wave was obviously decreased when one end of the detonation chamber was closed and the other end was open. [WT5”HZ]
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Equivalence ratio
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Abstract Precursor air shocks with velocities that are 50 % higher than the velocity of detonation occur not only in cylindrical holes, but also in flat slits. By attaching to the test charge a sufficiently long plexiglass body with the same hole or slit profiles it is possible to observe the end face of the test charge and, thus, to record the changes in the detonation profile caused by slits, in particular by such that are oblique to the direction of detonation. One result is, that there is no through‐detonation across thin slits that are at a flat angle to the detonation wave.
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We investigate the evolution of cylindrical cellular detonation with different instabilities. The numerical results show that with decreasing initial temperature, detonation becomes more unstable and the cells of the cylindrical detonation tend to be irregular. For stable detonation, a divergence of cylindrical detonation cells is formed eventually due to detonation instability resulting from a curved detonation front. For mildly unstable detonation, local overdriven detonation occurs. The detonation cell diverges and its size decreases. For highly unstable detonation, locally driven detonation is more obvious and the front is highly wrinkled. As a result, the diverging cylindrical detonation cell becomes highly irregular.
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Calculations of the interaction of plane (one-dimensional) and cellular (two-dimensional) detonation waves in hydrogen-air mixture with inert filters were carried out on the basis of the proposed physical and mathematical models, based on the detailed and reduced kinetics, describing such processes. The realized detonation regimes of attenuation and suppression of detonation were revealed. Comparison of results obtained by detailed and reduced kinetics showed that reduced kinetics gives overestimated detonation velocities compared to the detailed kinetics. But the obtained concentration limits of detonation practically equal to each other for both kinetics models. Comparison of processes of attenuation and suppression of plane and cellular detonation showed that the suppression of cellular detonation is more difficult to achieve compared to a plane detonation wave. Detonation failure criterion that shows that at the increasing the filter particles diameter, it is necessary to increase the volume concentration proportionally in order to successfully suppress detonation both in the case of a plane detonation wave and in the case of cellular detonation, was obtained.
Inert
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Rotating detonation engines are studied more and more widely because of high thermodynamic efficiency and high specific impulse. Rotating detonation of hydrogen and oxygen was achieved in this study. Rotating detonation waves were observed by high speed cameras and detonation pressure traces were recorded by PCB pressure sensors. The velocity of rotating detonation waves is fluctuating during the run. Low frequency detonation instabilities, intermediate frequency detonation instabilities and high frequency detonation instabilities were discovered. They are relevant to unsteady heat release, acoustic oscillations and rotating detonation waves.
Detonation velocity
Specific impulse
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