Thermal gradient of in-flight polymer particles during cold spraying

International audienceThe manufacture of polymer coatings via the cold-spray process remains challenging owing to the viscoelastic-viscoplastic behavior exhibited by polymers. One crucial step to improve cold-spray polymer coating is to determine the particles' thermal history during their flight from inside the nozzle to their impact on the substrate. In this study, we propose estimating the velocity and temperature of an isolated polymer particle traveling through a nozzle with a sharp change in its cross-section. The preliminary results show that the geometric discontinuity constricts the flow, thereby increasing the particle velocity. Moreover, a significant thermal gradient is expected inside the particle, which in turn leads to a gradient of mechanical properties of the polymeric particle during impact

Spatiotemporal dynamics of discrete sine-Gordon lattices with sinusoidal couplings

The spatiotemporal dynamics of a damped sine-Gordon chain with sinusoidal nearest-neighbor couplings driven by a constant uniform force are discussed. The velocity characteristics of the chain versus the external force is shown. Dynamics in the high- and low-velocity regimes are investigated. It is found that in the high-velocity regime, the dynamics is dominated by rotating modes, the velocity shows a branching bifurcation feature, while in the low-velocity regime, the velocity exhibits step-like dynamical transitions, broken by the destruction of strong resonances.Comment: 10 Revtex pages, 8 Eps figures, to appear in Phys. Rev.E 57(1998

Computational simulation of reactive species production by methane-air DBD at high pressure and high temperature

Computational simulations of a single streamer in DBD in lean methane-air mixture at pressure of 1 and 3 atm and temperature of 300 and 500 K were conducted for plasma-enhanced chemical reactions in a closed system. The effects of surrounding pressure and temperature are characterized for reactive species production by a DBD discharge. The results show that the production characteristics of reactive species are strongly influenced by the total gas number density and the higher concentration of reactive species are produced at higher pressure and lower gas temperature for a given initial reduced electric field

Improvement of CO

In this study, an innovative approach for the selective absorption of carbon dioxide (CO2) by ionic liquid electrospray was proposed. First, the fluid dynamical characteristics of ionic liquid electrospray with 1-ethyl-3-methylimidazolium acetate in ambient air was clarified by high-speed imaging and aerosol analysis. This was followed by enhancement of CO2 absorption by ionic liquid electrospray in a closed chamber filled with CO2 which was successfully demonstrated for the first time. The ionic liquid electrospray drastically improves CO2 chemisorption by achieving higher CO2 loading ratio of ionic liquid due to the continuous generation of nano-sized droplets with a large specific surface area, as well as the sufficient spreading of the spray by the Coulomb repulsion between charged droplets

Simulation study of SiH

Using the Particle-in-Cell/Monte Carlo (PIC/MC) method, the behavior of SiH4 plasma discharge in a narrow channel was studied. Simulations were carried out at a gas pressure of 5 Torr for an electrode distance of 20 mm and a narrow channel with an inner diameter of 2 mm. Most SiH$_{2}^{+}$ ions were found to be changed into SiH$_{3}^{+}$ ions due to SiH$_{2}^{+}$-SiH4 collisional charge exchange. The dominant charged species in the discharge were electrons and SiH$_{3}^{+}$ ions. The inner surface of the narrow channel greatly affected SiH4 plasma behavior due to an accumulation of charged particles. An intense ionization rate was found for the first time in the sheath on the inner surface of the narrow channel. The largest electron and SiH$_{3}^{+}$ ion densities appeared at the edge of the plasma bulk abutting the sheath on the inner surface of the narrow channel