Search

Laser irradiation may have a significant impact on the microwave transmission properties of glass fiber composites. In this study, a two-dimensional microwave transmission transient model of glass fiber composites during the complete laser irradiation process was developed. The numerical results indicate that carbonization during irradiation causes a significant increase in dielectric loss, thus resulting in a decrease in transmittance. After irradiation, the dielectric loss decreased due to the decrease in temperature, which, in turn, led to an increase in transmittance. The increased transmittance after cooling was lower than the original value due to the generation of pyrolytic carbon with a high dielectric loss. The numerical results were verified by conducting an experiment wherein the microwave transmittance of glass fiber composites was measured in real time before, during, and after laser irradiation. In addition, the effects of different laser parameters on the real-time microwave transmittance during laser irradiation were investigated experimentally and numerically. For the same total energy, a laser with a high power density and short irradiation time had a more significant effect on the attenuation of transmittance. • Real-time microwave transmittance of GFRP during laser irradiation is observed. • Carbonization and high temperature are the primary causes of microwave attenuation. • Transmittance reduces to 35 % (6 s, 509 W/cm2), and rebounds to 64 % 10 s later. • Under the same laser energy, higher power density affects more microwave attenuation. • Transmittance at the end of 306 (1019) W/cm2 irradiation for 10 (3) s is 43 (30) %. [ABSTRACT FROM AUTHOR]

Abstract: Dielectric-barrier discharge (DBD) plasma, initiated at ambient condition, has been successfully applied for removing template from the mesoporous MCM-41 molecular sieve. The template removal rate using DBD plasma is eight times higher than the rate via thermal calcination. A perfect hexagonal pore structure was obtained after the template removal using the plasma, according to the characterization using the X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen adsorption analyses. The effectiveness of the plasma prepared mesoporous MCM-41 molecular sieve as the catalyst support has been confirmed using the Suzuki reaction with palladium as the active species. [Copyright &y& Elsevier]

[Display omitted] • The model used temperature dependent surface tension and condensation coefficient. • The fluid flow is mainly driven by Marangoni force during laser irradiation. • Marangoni force and capillary force make the fluid move back and forth during cooling. • Ring ripples are formed by the reciprocating motion of melt during cooling process. • Ripples' distributions are different on different thickness foils. Continuous wave laser (CW laser) ablation morphology of copper foil in low pressure environment is very different from that in atmospheric environment. In low pressure environment, there are few splashes on the surface of molten region. Ring ripples are also observed on the surfaces of molten region after laser irradiation. A 2D axisymmetric model considering temperature dependent surface tension and condensation coefficient is established to investigate the molten flow behavior in molten pool during laser ablation in the environment of 10 Pa. The results show that Marangoni effect caused by temperature gradient is the main driver of fluid flow during laser irradiation. Ring ripples are formed by Marangoni effect and capillary force during cooling process. Compared with those in atmospheric environment, the recoil pressure in 101 Pa environment is smaller and the evaporation rate is higher at the same temperature. For foils with different thicknesses, the differences in temperature gradient make the distribution of ripples different. The mechanisms of the ripple formation on metal foil induced by CW laser irradiation are revealed for the first time. [ABSTRACT FROM AUTHOR]