radiations in this process are used for the identification of the elemental composition of the sample [7][8][9].LIBS offers many advantages over other spectroscopic techniques such as mass spectroscopy, electrode spark and inductively coupled plasma. Some of LIBS unique advantages include the ability to make in situ analysis even in hostile environment, remote sensing, little or no preparation of the sample, and multi-element analysis [10][11][12]. Based on these advantages, LIBS has been extensively investigated on several samples including liquids [13], gases [14] and as well from non-conducting and conducting solids [15].LIBS is also a spectroscopic technique for the determination of the density of electron, electron temperature and number densities of the plasma plume [16,17]. Laserinduced plasma temperatures are influenced by various experimental conditions such as ambient surrounding, laser energy and laser pulse width. Most of the studies on LIBS temperatures report that the plasma temperature tends to increase with increasing laser energy, pulse width, laser wavelength and ambient pressure [18][19][20][21].Although LIBS has been employed successfully in several experimental and theoretical works, to analyze the spectroscopic composition of the samples, there are still many aspects which need to be investigated [6]. For example, Barthelemy et al. [22] investigated the influence of the laser parameters of an aluminum-induced plasma. They reported that the temperature slightly decreases at the plasma edge and close to the aluminum surface. This decrease in temperature at the plasma edge is basically caused by radiative cooling, while the decrease in temperature at the aluminum surface is as a result of thermal conduction. The authors also found that at the first microsecond of the ablation plume, the electron density was spatially homogeneous.Zhang et al.[23] also reported on the influence of laser parameters on plasma temperature. Their results predicted Abstract The magnesium plasma induced by a 1064-nm Q-switched Nd:YAG laser in atmospheric air was investigated. The evolution of the plasma was studied by acquiring spectral images at different laser energies and delay times. We observed that the intensities of the spectral lines decrease with larger delay times. The electron temperature was determined using the Boltzmann plot method. At a delay time of 100 ns and laser energy of 350 mJ, the electron temperature attained their highest value at 10164 K and then decreases slowly up to 8833.6 K at 500 ns. We found that the electron temperature of the magnesium plasma increases rapidly with increasing laser energy.

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The purpose of this paper is to demonstrate a new process technology using the cavitation phenomenon, mainly a water-jet shock microforming, for the fabrication of a metallic foil. 304 stainless steel was exposed to a high-speed submerged water jet with different incident pressures and certain working conditions. In this experiment, a KEYENCE VHX-1000C digital microscope, confocal laser-scanning microscope (Axio CSM 700), and micro-Vickers hardness tester were utilized to observe the forming depth, surface quality, thickness distribution, and section hardness distributions under different incident pressures. The experimental results indicated that the surface morphology of the metal foils attained good geometrical features under this dynamic microforming method and there were no cracks or fracture. The forming depth and surface roughness increased with the incident pressure. In addition, the forming depth increased from 124.7 μm to 327.8 μm, while the surface roughness also increased from 0.685 μm to 1.159 μm at an incident pressure of 8 MPa to 20 MPa. Maximum thickness thinning of the formed foils occurred at the fillet region when the thickness thinning ratio was 21.27% under the incident pressure of 20 MPa, and there was no fracture at the bottom or the fillet region. The tested hardness indicated that during the cold-rolled state of the sample, the hardness sample increased slightly along the cross section of the formed region and the hardness of the annealed 304 stainless steel foils increased significantly along the cross-sectional region.

In this work, the effect of the sample temperature on the magnesium (Mg) and titanium (Ti) plasmas generated by a Q-switched Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) laser operating at its fundamental wavelength of 1064 nm has been investigated. We observed that increasing the sample temperature significantly enhanced the emission intensities of the plasmas. Comparing the emission peak intensities of the case of 100 °C to the case of 300 °C, we recorded a substantial enhancement of the peak intensities of the latter compared to the former. From these results it can be observed that increasing the sample temperature has a significant effect on the emission intensities of the plasmas. We also studied the plasma dynamics and found that increasing the sample temperature also decreases the air density around the Mg sample surface. The reduction in the air density resulted in a decrease in the radiation process and lowers collision probability. Furthermore, as the plasma expands, the plasma pressure also decreases. In addition, we also employed circular and square cavities to confine the titanium plasma, and investigated the effect of the sizes of the circular and square cavities on the titanium plasma. We observed a general improvement in the emission intensities with both the circular and square cavities and attributed this improvement to the plasma compression effect of the shock waves produced by the plasma within the cavities.

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