Hisham Imam

A study of the laser plasma parameters at different laser wavelengths

Abstract Diagnostic of laser produced aluminum plasma was performed adopting a spectroscopic technique. A Q-switched Nd:YAG laser at wavelengths 1064, 532 and 355 nm with maximum energies of 500, 100 and 60 mJ, respectively, and pulse duration of 7 ns with repetition rate of 1 Hz was used. The measurements were carried out to determine the spatial electron temperature using the Boltzmann plot for the Al II lines and the spatial profile of the electron density using Stark broadening formula for the three different laser wavelengths. The maximum attainable value of the electron temperature was found at a certain distance away from the target surface depending on the laser wavelength. The electron density reaches its highest value near the target surface. The measurements are then compared with available published experiment and theory and are found to be in agreement with the theory of local thermodynamic equilibrium (LTE).

LIBS limit of detection and plasma parameters of some elements in two different metallic matrices

In the present work a detailed study has been performed on the effect of the matrix on the limit of detection (LOD) and the plasma parameters of the laser induced breakdown spectroscopy (LIBS) technique. The LOD of magnesium, silicon, manganese and copper as minor elements was evaluated in aluminium standard sample alloys compared to the values of the LOD of the same elements in standard steel alloys. The effect of changing the matrix on the laser induced plasma plume parameters, namely the plasma temperature Te and the electron density Ne, has been also studied. Calibrations were achieved for the four elements with linear regression coefficients between 98–99% on average. According to the obtained results Mn and Cu have the lowest LOD in the steel alloy matrix, while Mg has much lower LOD in the aluminium alloy matrix. These results may be interpreted in view of the compatibility of the physical properties of the elements existing in the same matrix. Approximately similar electronic structure and values of melting point, density, atomic weight, etc., may facilitate better conditions for energy transfer within the matrix. From the application view point, it is possible for LIBS in the on-line industrial process control to follow up only a single element (that with the lowest LOD in such matrix) as a marker for the correct alloying in metals and mixing in pharmaceuticals.

Elemental content of enamel and dentin after bleaching of teeth (a comparative study between laser-induced breakdown spectroscopy and x-ray photoelectron spectroscopy)

The elemental content of the superficial and inner enamel as well as that of dentin was analyzed using laser-induced breakdown spectroscopy (LIBS) and x-ray photoelectron spectroscopy (XPS) of bleached and unbleached tooth specimens. It is thus clear from the spectral analysis using both the LIBS and XPS technique that elemental changes (though insignificant within the scopes of this study) of variable intensities do occur on the surface of the enamel and extend deeper to reach dentin. The results of the LIBS revealed a slight reduction in the calcium levels in the bleached compared to the control specimens in all the different bleaching groups and in both enamel and dentin. The good correlation found between the LIBS and XPS results demonstrates the possibility of LIBS technique for detection of minor loss in calcium and phosphorus in enamel and dentin.

LASER-INDUCED BREAKDOWN SPECTROSCOPY TECHNIQUE IN IDENTIFICATION OF ANCIENT CERAMICS BODIES AND GLAZES

In this paper we report a study on Laser Induced Breakdown Spectroscopy (LIBS) as a promising non-destructive technique for the identification of the colored glazes, and clay’s bodies of Fatimid ceramics ancient artifacts. The scientific examination of ceramics may be helpful in unraveling the history of ancient shards, particularly as the process of its production such as firing condition and temperatures. The analysis of pottery, ceramic bodies and glazed coatings is required in order to structure the conservation or restoration of a piece. Revealing the technical skills of ancient potters has been one of the most important issues for gaining a deep insight of bygone culture and also it is required in order to structure the conservation or restoration of a piece of art. LIBS measurements were carried out by focusing a Nd-YAG laser at 1064 nm with pulse width of 10 ns and 50 mJ pulse energy on the surface of the sample by a 100-mm focal length lens. The plasma emission was collected by telescopic system and transferred through a fiber to Echelle spectrometer attached to an ICCD camera. The focal spot diameter is found to be in the range of 100-150 μm. which is small enough to consider this technique as a non-destructive technique. LIBS technique clarified that each piece of archaeological objects has its own finger print. X-ray diffraction (XRD) analysis was carried out on these archaeological ceramic body samples to study raw materials such as clays, which allowed the investigation of the crystal structure and showed the changes in its structure through firing process. This provided information on the ceramic characteristic and composition of the ceramic bodies.