Studies of the Iranian medieval ceramics surface modified by pulsed tea CO2 and Nd:YAG lasers

This paper presents the results of the morphological and chemical changes on the surface of an Iranian ceramics sample irradiated by a Transversely Excited Atmospheric (TEA) CO2 and an Nd:YAG laser. The sample originates from the archeological site of Yazd (Iran) and is assumed to have been a part of an aqueduct. The effect of laser parameters (energy density (fluency), number of pulses and wavelength) on the induced changes was studied. The tests were performed in order to establish the mechanism of the interaction with the fluence above the damage threshold. This is an essential parameter in the use of lasers for cleaning as well as for eliminating surface defects such as cracks, by melting superficial layers and thus strengthening the objects in question. Another objective was to obtain as much as possible information about the material composition necessary for the conservation and restoration of this ceramics. A TEA CO2 (10.6 μm wavelength, pulse duration 100 ns (Full Width at Half Maximum – FWHM)) laser and an Nd:YAG laser (wavelength 1064 nm and 532 nm, FWHM=150 ps) have been used for the surface treatment. Laser fluences were in the range of 1–20 J/cm2. The ceramics surface morphology modifications, induced by pulsed lasers, were characterized by a scanning electron microscope (SEM), while the composition was examined by energy-dispersive (EDX) and X-ray fluorescence (XRF) spectroscopy. The results show that there are significant differences depending on the laser applied and whether the surface is glazed or not.