Showing papers by "Ali Reyhani published in 2014"

Time-resolved evolution of metal plasma induced by Q-switched Nd:YAG and ArF-excimer lasers

Abstract: Laser-induced breakdown spectroscopy (LIBS) has been performed on the palladium samples as well as various metal targets (Mo, Ni, Cu, Co, and Au) at the atmospheric air, using a Q-switched Nd:YAG laser at 1064 nm and ArF-excimer laser at 193 nm. The evolution of the laser-induced plasma is characterized in terms of the temporally resolved spectral emissivity at the onset of plasma up to several microseconds. Time-resolved induced plasmas are studied using the pulsed energy ranging 50–100 mJ in various time delays (1–32 μs). Effect of the pulsed energy on the plasma lifetime is investigated to attain the local thermodynamic equilibrium (LTE) conditions. IR and UV laser induced plasma with different pulsed energies are utilized in various time delays in order to optimize the spectroscopic performance. Those involve peak-to background ratio (P/B), line intensity, electron density and plasma temperature. It was shown that P/B ratio is taken into account as a supportive indicator to evaluate LTE condition accompanying McWhirter criterion. Moreover, the correlation between electronic plasma characteristics with thermal properties of metal targets is investigated.

Methane Decomposition Using Metal-Assisted Nanosecond Laser-Induced Plasma at Atmospheric Pressure

Abstract: Methane decomposition has been extensively investigated using a Q-switched Nd:YAG laser, focused on the metal catalysts including Ni, Fe, Pd, and Cu within the controlled chamber to verify the effect of catalyst, plasma properties, and yield and selectivity of the products. Fourier transform IR spectroscopy (FTIR) and gas chromatography (GC) are employed to support the characterization of the components. This indicates that methane is strongly decomposed within the metal-assisted laser-induced plasma, leading to the subsequent recombination and the production of heavier hydrocarbons. The dominant species, including propane, ethane, and ethylene, have been identified examining different metallic catalysts. The dissociation rate, conversion ratio, selectivity, and yield of products are strongly dependent on the metal target and plasma characteristics.

Chemo-physical properties of renal capsules under ultraviolet-c exposure

Abstract: The renal capsule tissue of lamb was irradiated with ultraviolet-C light and the treated samples were analyzed by uniaxial tensile test, dynamic mechanical analysis, attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. It was shown that the skin cross-linking is dominant in low doses in accordance with the contact angle assessment. Conversely, the strong bulk degradation takes place at high doses. Similarly, the bulk cross-linking affects the mechanical tests as to enhance the stiffness at low doses, whereas strong degradation occurs at high doses that mainly arises from the strong bulk chain scission.

Characteristic emission enhancement in the atmosphere with Rn trace using metal assisted LIBS

Abstract: Several characteristic emission lines from the metal targets (Cu, Zn and Pb) were investigated in trace presence of radon gas in the atmospheric air, using Q-SW Nd:YAG laser induced plasma inside a control chamber. The emission lines of metal species are noticeably enhanced in (Rn+air), relative to those in the synthetic air alone. Similar spectra were also taken in various sub-atmospheric environments in order to determine the optimum pressure for enhancement. Solid-state nuclear track detectors were also employed to count the tracks due to alpha particles for the activity assessment.

The effect of atmospheric Rn trace decay on Cu target characteristic lines in laser induced breakdown spectroscopy

Abstract: Several characteristic emission lines due to the metal target (Cu) were investigated in the presence of radon trace in the atmospheric air using Q-SW Nd:YAG laser induced plasma within the irradiation control chamber. Regarding the previous experiments the emission lines of metal species in (Rn+air) are noticeably enhanced respect to those in the synthetic air, while those peak intensities instantaneously decreases due to radon decay, such that the radon's half-life can be determined by an optical method too. Here we made an attempt to utilize optical methods in order to determine nuclear characteristics accordingly.

Propane dissociation in the laser induced plasma using Q-switched Nd:YAG laser in the presence metal targets

Abstract: In this paper, the dissociation of propane in the presence of metal targets Iron, copper, nickel and palladium using Nd:YAG laser with specifications: wavelength 1064 nm, energy 100 mJ, width of 10 ns and pulse repetition rate of 5 Hz were investigated. In order to identify the products obtained from these experiments methods infrared spectroscopy (FTIR) and gas chromatography (GC) has been studied. Results from the experiments indicate the production of heavier hydrocarbons such as ethylene, acetylene, ethane, methane and so on due to propane dissociation. The results showed that product mainly depends on the type catalyst and the maximum hydrocarbon product is ethane with selectivity 24/6% in the presence of nickel target.

Generation of Graphene and nitrogen doped graphene by using laser ablation in cryogenics media

Abstract: In this paper by using laser ablation of graphite target, graphene and nitrogen-doped graphene was generated in liquid Argon and liquid nitrogen, respectively. The generated graphene in liquid Argon was purer and less defect because of Lack of reactivityof argon. However, graphene doped nitrogen is generated in nitrogen liquid because of reactivity of nitrogen. Also graphene structure has Advantages such as easy sample collection, lower production costs and a single stage of production rather than the other way Graphene is produced.