Papers by Author: S. Petrović

Abstract: The effects of nitrogen pre-implantation of AISI C1045 steel substrates on the properties of deposited TiN coatings were investigated. Nitrogen ion implantations were performed at 40 keV, to the fluences from 5x1016 – 5x1017 ions/cm2. On so prepared substrates we deposited 1.3 μm thick TiN layers by reactive sputtering. Structural characterizations of the samples were performed by grazing incidence X-ray diffraction analysis (GXRD), standard X-ray diffraction analysis (XRD), and scanning electron microscopy (SEM). Microhardness was measured by Vicker’s method. The obtained results indicate the formation of iron-nitrides in the near surface region of the substrates, more pronounced for higher implanted fluences. The structure of the deposited TiN coatings shows a strong dependence on the pre-implantation of the substrates, which is attributed to the changed local structure at the surface. Ion implantation and deposition of hard TiN coatings induce an increase of the microhardness of this low performance steel of more than eight times.

Abstract: In this work we investigated the interaction of ns laser pulses (TEA CO2 and Nd:YAG) with a titanium nitride (TiN) thin film. The TiN thin film of 1μm thickness was deposited by PVD method on silicon substrate. Modification of TiN film was induced by laser pulses with power densities of about 108 and 109 W/cm2. Part of the laser energy absorbed on the target surface was converted into thermal energy and effects such as melting, vaporization and exfoliation were observed. Nd:YAG laser produced craters with sharp periphery, while TEA CO2 laser created damages with broad boundary zone. Hydrodynamic effects were especially pronounced during irradiation with TEA CO2 laser.

Abstract: The effects of TEA CO2 laser radiation on AISI 420 stainless steel and formed surface structures are studied. The laser energy density of 45.0 J/cm2 has modified the target surface. Qualitatively, the modifications of AISI 420 steel can be summarized as follows: change of color after action of one laser pulse; central zone of interaction in crater like form and periphery zone of interaction (for more than 10 laser pulses); appearance of grainy features and ablation rate of near 4 nm per laser pulse (action of 400 laser pulses); hydrodynamical effects like resolidified rim and droplets.

Abstract: We investigate theoretically the angular distributions and the rainbows of 1 GeV protons channeled in the ropes of (10, 0) single-wall carbon nanotubes. The rope length is varied between 0.53 and 5.29 µm. The angular distributions of channeled protons are generated using the numerical solution of the proton equations of motion in the transverse plane and the computer simulation method. We use Molière’s expression for the continuum interaction potential of the proton and the rope. The rainbow lines in the impact parameter plane and scattering angle plane are also determined numerically. We show that these lines ensure the full explanation of the angular distributions. The possible applications of these results are discussed.