The analytical capability of laser-produced plasma for the analysis of low alloying elements in c... more The analytical capability of laser-produced plasma for the analysis of low alloying elements in cast iron samples has been investigated. The plasma was induced by irradiation of a sample in air at atmospheric pressure using an infrared CO 2 laser. Emission spectra were recorded by time-integrated spatially-resolved measurement technique. A set of ten cast iron samples in a powder or particulate form were provided by BAM (Bundesanstalt für Material Forschung und Prüfung, Deutschland), seven of which were used for calibration, and three were treated as unknowns. Linear calibration curves were obtained for copper, chromium, and nickel, with correlation coefficients above 0.99. Precision and accuracy of the LIBS method was evaluated and compared to those obtained by the inductively coupled plasma (ICP) analysis of the same samples. Detection limits for Cu, Cr and Ni were close to those reported in the literature for other comparable iron-based alloys obtained using different LIBS systems. Analytical figures of merit of the studied LIBS system may be considered as satisfying, especially in the light of other advantages of the method, like cost effective and fast analysis with no sample preparation, and with a possibility for real-time on-site analysis.
In this work we present biological effects of silver nanoparticles (AgNPs) synthesized by picosec... more In this work we present biological effects of silver nanoparticles (AgNPs) synthesized by picosecond laser ablation of silver in deionized water. We examined induction of chromosomal aberrations, lymphocyte micronuclei, appearance and recovery of double strand breaks (DSBs) of DNA, cell proliferation potential, concentration of lipid peroxidation products and insulin-like growth factor 1 (ILGF-1). We found that AgNPs sized from 3nm to 8nm induce cell cytostasis, which is accompanied with its clastogenic action on DNA, while AgNPs, sized 2nm behaves contrary stimulating cell proliferation by enhancing ILGF-1 concentration.
Spatially resolved, time-integrated optical emission spectroscopy was applied for investigation o... more Spatially resolved, time-integrated optical emission spectroscopy was applied for investigation of copper plasma produced by a nanosecond infrared (IR) transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 μm. The effect of surrounding air pressure, in the pressure range 0.1 to 1013 mbar, on plasma formation and its characteristics was investigated. A linear dependence of intensity threshold for plasma formation on logarithm of air pressure was found. Lowering of the air pressure reduces the extent of gas breakdown, enabling better laser-target coupling and thus increases ablation. Optimum air pressure for target plasma formation was 0.1 mbar. Under that pressure, the induced plasma consisted of two clearly distinguished and spatially separated regions. The maximum intensity of emission, with sharp and well-resolved spectral lines and negligibly low background emission, was obtained from a plasma zone 8 mm from the target surface. The estimated excitation temperature i...
Diamond coatings were deposited by the synchronous and coupled action of a hot filament CVD metho... more Diamond coatings were deposited by the synchronous and coupled action of a hot filament CVD method and a pulsed CO 2 laser in spectro-absorbing and spectro-non-absorbing diamond precursor atmospheres. The obtained coatings were structured/patterned, i.e., they were comprised of uncovered, bare locations. An extra effect observed only in the spectro-active diamond precursor atmosphere was the creation of another laser spot in the coating-a reflection spot. In order to establish the practical usability of the latter one, extensive microscopic investigations were performed with consideration of the morphology changes in the spot of the direct laser beam. Normal incidence SEM images of this spot showed a smooth surface, without any pulse radiation damage. AFM imaging revealed the actual surface condition and gave precise data on the surface characteristics.
in HV conditions, just before the growing process. This prevents the catalyst oxidation, responsi... more in HV conditions, just before the growing process. This prevents the catalyst oxidation, responsible for the reduced yield of tubes in the growth. No hydrogen and/or ammonia or other time-consuming pre-treatments are needed. Isolated SWCNTs are obtained starting from a 1 nm thick catalyst film. These results make the technique here described an efficient method (the total time of growth, including catalyst preparation, is $40 min for MWCNTs and $15 min for SWCNTs in our used catalyst deposition rate, see above), and a promising way for the growth of nanotubes.
The interaction of an Er, Yb, Cr-glass laser, operating at 1540 nm wavelength and a pulse duratio... more The interaction of an Er, Yb, Cr-glass laser, operating at 1540 nm wavelength and a pulse duration of 40 ns, with Ni/Ti multilayer thin films has been studied. Five (Ni/Ti) bilayers deposited by DC ion sputtering on Si(100) wafers to a total thickness of about 180 nm were treated with laser fluences of about 6.4 and 8.8 J cm −2. Single and multi-pulse laser irradiation was done at normal incidence in air, water and ethanol ambients. The composition and surface morphology were monitored by particle-induced x-ray emission, Rutherford backscattering spectrometry (RBS), scanning electron microscopy and profilometry. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the target surface. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. RBS analysis revealed that laser modification induced inter-mixing between the components of individual Ni and Ti layers, with indications of the formation of NiTi intermetallic compounds. An interesting finding is the morphological changes dominant in the Si substrate, whereas the Ni/Ti multilayer structure has mainly undergone changes in the chemical composition.
Creation of laser-induced morphology features, particularly laser-induced periodic surface struct... more Creation of laser-induced morphology features, particularly laser-induced periodic surface structures (LIPSS), by a 532 nm picosecond Nd:YAG laser on crystalline silicon is reported. The LIPSS, often termed ripples, were produced at average laser irradiation fluences of 0.7, 1.6, and 7.9 J cm À2 . Two types of ripples were registered: micro-ripples (at micrometer scale) in the form of straight parallel lines extending over the entire irradiated spot, and nano-ripples (at nanometer scale), apparently concentric, registered only at the rim of the spot, with the periodicity dependent on laser fluence. There are indications that the parallel ripples are a consequence of the partial periodicity contained in the diffraction modulated laser beam, and the nano-ripples are very likely frozen capillary waves. The damage threshold fluence was estimated at 0.6 J cm À2 .
Journal of Optics A: Pure and Applied Optics, 2007
The interaction of a picosecond Nd:YAG laser (wavelength 532 nm, pulse duration 40 ps) with a pol... more The interaction of a picosecond Nd:YAG laser (wavelength 532 nm, pulse duration 40 ps) with a polycrystalline titanium nitride (TiN) film was studied. The TiN thin film was deposited by physical vapour deposition on a silicon substrate. The titanium nitride/silicon system was modified with an energy fluence from 0.2 to 5.9 J cm −2 . Multi-pulse irradiation was performed in air by a focused laser beam. Surface modifications were analysed after 1-100 successive laser pulses. Depending on the laser pulse energy and pulse count, the following phenomena were observed: (i) increased surface roughness, (ii) titanium nitride film cracking, (iii) silicon substrate modification, (iv) film exfoliation and (v) laser-induced periodical surface structures on nano-(NPSS) and micro-dimensions (MPSS).
Surface texturing of the metals, including steels, gained a new dimension with the appearance of ... more Surface texturing of the metals, including steels, gained a new dimension with the appearance of femtosecond lasers. These laser systems enable highly precise modifications, which are very important for numerous applications of metals. The effects of a Ti:sapphire femtosecond laser with the pulse duration of 160 fs, operating at 775 nm wavelength and in two operational regimes -single pulse (SP) and scanning regime, on a high quality AISI 1045 carbon steel were studied. The estimated surface damage threshold was 0.22 J/cm 2 (SP). Surface modification was studied for the laser fluences of 0.66, 1.48 and 2.37 J/cm 2 . The fluence of 0.66 J/cm 2 , in both working regimes, induced texturing of the material, i.e. formation of periodic surface structures (PSS). Their periodicity was in accordance with the used laser wavelength. Finally, changes in the surface oxygen content caused by ultrashort laser pulses were recorded.
The interaction of a transversely excited atmospheric (TEA) CO 2 laser with austenitic stainless ... more The interaction of a transversely excited atmospheric (TEA) CO 2 laser with austenitic stainless AISI 316 and high-speed tool AISI M2 steel is considered. The results have shown that both types of steel were surface modi®ed by the laser beam, for the laser energy densities used. Morphological features on the AISI M2 were more prominent in comparison to a AISI 316 steel. On the AISI M2 steel crater like forms, solidi®ed boundary and hydrodynamical modi®cations were observed, while on the AISI 316 one, corrugation, cracking and resolidi®ed areas were registered. The morphology changes of steel surfaces in dependence of laser pulse temporal shape were analyzed especially. The pulse with a tail for difference of a tail-free pulse, for the same incident peak power density, as a rule caused higher level of damage. #
The interaction of a transversely excited atmospheric (TEA) CO 2 laser, pulse duration of about 2... more The interaction of a transversely excited atmospheric (TEA) CO 2 laser, pulse duration of about 2 ms (FWHM of initial spike 120 ns), with p-type single crystalline silicon doped by boron, was studied. The results have shown that the silicon was surface modi®ed by the laser beam of 12.0 J cm À2 energy density. The energy absorbed from the CO 2 laser beam is converted partially into thermal energy, which generates a series of effects such as melting, vaporisation of molten material, shock waves, etc. Morphological manifestations on the silicon surface are: nonuniform modi®cations (central zone of interaction); wave-like periodical microstructure (inner periphery zone); hydrodynamical structure-like droplets (outer periphery zone). Wave-like microstructure consists of periodic parallel fringes with a period of about 0.8 mm. Formation of these wave-like microstructures is very complex. Explanation includes a consideration of the laser-induced periodic surface structure (LIPSS) effect. The process of the CO 2 laser interaction with silicon was not initially accompanied by plasma. Plasma, in the form of a spark, typically appeared after about 100 cumulated laser pulses. #
The interaction of a transversely excited atmospheric (TEA) CO 2 laser with austenitic stainless ... more The interaction of a transversely excited atmospheric (TEA) CO 2 laser with austenitic stainless AISI 316 and high-speed tool AISI M2 steel is considered. The results have shown that both types of steel were surface modi®ed by the laser beam, for the laser energy densities used. Morphological features on the AISI M2 were more prominent in comparison to a AISI 316 steel. On the AISI M2 steel crater like forms, solidi®ed boundary and hydrodynamical modi®cations were observed, while on the AISI 316 one, corrugation, cracking and resolidi®ed areas were registered. The morphology changes of steel surfaces in dependence of laser pulse temporal shape were analyzed especially. The pulse with a tail for difference of a tail-free pulse, for the same incident peak power density, as a rule caused higher level of damage. #
Interaction of a TEA CO 2 laser, operating at 10.6 m wavelength and pulse duration of 100 ns (FWH... more Interaction of a TEA CO 2 laser, operating at 10.6 m wavelength and pulse duration of 100 ns (FWHM), with a titanium implant in various gas atmospheres was studied. The Ti implant surface modification was typically studied at the moderate laser beam energy density/fluence of 28 J/cm 2 in the surrounding of air, N 2 , O 2 or He. The energy absorbed from the TEA CO 2 laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium implant surface changes and phenomena were observed, depending on the gas used: (i) creation of cone-like surface structures in the atmospheres of air, N 2 and O 2 , and dominant micro-holes/pores in He ambient; (ii) hydrodynamic features, most prominent in air; (iii) formation of titanium nitride and titanium oxide layers, and (iv) occurrence of plasma in front of the implant. It can be concluded from this study that the reported laser fluence and gas ambiences can effectively be applied for enhancing the titanium implant roughness and creation of titanium oxides and nitrides on the strictly localized surface area. The appearance of plasma in front of the implants indicates relatively high temperatures created above the surface. This offers a sterilizing effect, facilitating contaminant-free conditions.
Interaction of a nanosecond transversely excited atmospheric (TEA) CO 2 laser, operating at 10.6 ... more Interaction of a nanosecond transversely excited atmospheric (TEA) CO 2 laser, operating at 10.6 mm, with tungsten-titanium thin film (190 nm) deposited on silicon of n-type (1 0 0) orientation, was studied. Multi-pulse irradiation was performed in air atmosphere with laser energy densities in the range 24-49 J/cm 2 . The energy absorbed from the laser beam was mainly converted to thermal energy, which generated a series of effects. The following morphological changes were observed: (i) partial ablation/exfoliation of the WTi thin film, (ii) partial modification of the silicon substrate with formation of polygonal grains, (iii) appearance of hydrodynamic features including nano-globules. Torch-like plumes started appearing in front of the target after several laser pulses. #
Interaction of an Nd:YAG laser, operating at 1064 or 532 nm wavelength and pulse duration of 40 p... more Interaction of an Nd:YAG laser, operating at 1064 or 532 nm wavelength and pulse duration of 40 ps, with titanium implant was studied. Surface damage thresholds were estimated to 0.9 and 0.6 J/cm 2 at wavelengths 1064 and 532 nm, respectively. The titanium implant surface modification was studied by the laser beam of energy density of 4.0 and 23.8 J/cm 2 (at 1064 nm) and 13.6 J/cm 2 (at 532 nm). The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium/implant surface morphological changes were observed: (i) both laser wavelengths cause damage of the titanium in the central zone of the irradiated area, (ii) appearance of a hydrodynamic feature in the form of resolidified droplets of the material in the surrounding outer zone with the 1064 nm laser wavelength and (iii) appearance of wave-like microstructures with the 532 nm wavelength. Generally, both laser wavelengths and the corresponding laser energy densities can efficiently enhance the titanium/implant roughness. This implant roughness is expected to improve its bio-integration. The process of the laser interaction with titanium implant was accompanied by formation of plasma. #
The interaction of a transversely excited atmospheric (TEA) CO 2 laser with chromium oxynitride (... more The interaction of a transversely excited atmospheric (TEA) CO 2 laser with chromium oxynitride (CrON) coating deposited on a AISI 304 steel substrate was considered. The results have shown that CrON was surface-modified by the laser beam of 45 J/cm 2 energy density. The energy absorbed from the TEA CO 2 laser beam was partially converted into thermal energy, which has generated a series of effects such as melting, vaporization of the molten material, and shock waves in the vapor and in the solid. Morphological manifestations on the CrON coating surface can be summarized as follows: nonuniform features with ablation and appearance of crater-like form (central zone of interaction); appearance of three damaged areas and presence of hydrodynamic effects with resolidified droplets (periphery zone of interaction). In case of applied energy density the interaction of laser radiation with CrON has been always followed by plasma creation in front of the coating. PACS 79.20.Ds; 61.80.Ba
The analytical capability of laser-produced plasma for the analysis of low alloying elements in c... more The analytical capability of laser-produced plasma for the analysis of low alloying elements in cast iron samples has been investigated. The plasma was induced by irradiation of a sample in air at atmospheric pressure using an infrared CO 2 laser. Emission spectra were recorded by time-integrated spatially-resolved measurement technique. A set of ten cast iron samples in a powder or particulate form were provided by BAM (Bundesanstalt für Material Forschung und Prüfung, Deutschland), seven of which were used for calibration, and three were treated as unknowns. Linear calibration curves were obtained for copper, chromium, and nickel, with correlation coefficients above 0.99. Precision and accuracy of the LIBS method was evaluated and compared to those obtained by the inductively coupled plasma (ICP) analysis of the same samples. Detection limits for Cu, Cr and Ni were close to those reported in the literature for other comparable iron-based alloys obtained using different LIBS systems. Analytical figures of merit of the studied LIBS system may be considered as satisfying, especially in the light of other advantages of the method, like cost effective and fast analysis with no sample preparation, and with a possibility for real-time on-site analysis.
In this work we present biological effects of silver nanoparticles (AgNPs) synthesized by picosec... more In this work we present biological effects of silver nanoparticles (AgNPs) synthesized by picosecond laser ablation of silver in deionized water. We examined induction of chromosomal aberrations, lymphocyte micronuclei, appearance and recovery of double strand breaks (DSBs) of DNA, cell proliferation potential, concentration of lipid peroxidation products and insulin-like growth factor 1 (ILGF-1). We found that AgNPs sized from 3nm to 8nm induce cell cytostasis, which is accompanied with its clastogenic action on DNA, while AgNPs, sized 2nm behaves contrary stimulating cell proliferation by enhancing ILGF-1 concentration.
Spatially resolved, time-integrated optical emission spectroscopy was applied for investigation o... more Spatially resolved, time-integrated optical emission spectroscopy was applied for investigation of copper plasma produced by a nanosecond infrared (IR) transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 μm. The effect of surrounding air pressure, in the pressure range 0.1 to 1013 mbar, on plasma formation and its characteristics was investigated. A linear dependence of intensity threshold for plasma formation on logarithm of air pressure was found. Lowering of the air pressure reduces the extent of gas breakdown, enabling better laser-target coupling and thus increases ablation. Optimum air pressure for target plasma formation was 0.1 mbar. Under that pressure, the induced plasma consisted of two clearly distinguished and spatially separated regions. The maximum intensity of emission, with sharp and well-resolved spectral lines and negligibly low background emission, was obtained from a plasma zone 8 mm from the target surface. The estimated excitation temperature i...
Diamond coatings were deposited by the synchronous and coupled action of a hot filament CVD metho... more Diamond coatings were deposited by the synchronous and coupled action of a hot filament CVD method and a pulsed CO 2 laser in spectro-absorbing and spectro-non-absorbing diamond precursor atmospheres. The obtained coatings were structured/patterned, i.e., they were comprised of uncovered, bare locations. An extra effect observed only in the spectro-active diamond precursor atmosphere was the creation of another laser spot in the coating-a reflection spot. In order to establish the practical usability of the latter one, extensive microscopic investigations were performed with consideration of the morphology changes in the spot of the direct laser beam. Normal incidence SEM images of this spot showed a smooth surface, without any pulse radiation damage. AFM imaging revealed the actual surface condition and gave precise data on the surface characteristics.
in HV conditions, just before the growing process. This prevents the catalyst oxidation, responsi... more in HV conditions, just before the growing process. This prevents the catalyst oxidation, responsible for the reduced yield of tubes in the growth. No hydrogen and/or ammonia or other time-consuming pre-treatments are needed. Isolated SWCNTs are obtained starting from a 1 nm thick catalyst film. These results make the technique here described an efficient method (the total time of growth, including catalyst preparation, is $40 min for MWCNTs and $15 min for SWCNTs in our used catalyst deposition rate, see above), and a promising way for the growth of nanotubes.
The interaction of an Er, Yb, Cr-glass laser, operating at 1540 nm wavelength and a pulse duratio... more The interaction of an Er, Yb, Cr-glass laser, operating at 1540 nm wavelength and a pulse duration of 40 ns, with Ni/Ti multilayer thin films has been studied. Five (Ni/Ti) bilayers deposited by DC ion sputtering on Si(100) wafers to a total thickness of about 180 nm were treated with laser fluences of about 6.4 and 8.8 J cm −2. Single and multi-pulse laser irradiation was done at normal incidence in air, water and ethanol ambients. The composition and surface morphology were monitored by particle-induced x-ray emission, Rutherford backscattering spectrometry (RBS), scanning electron microscopy and profilometry. Most of the absorbed laser energy was rapidly transformed into heat, producing intensive modifications of composition and morphology on the target surface. The results show an increase in surface roughness, formation of parallel periodic surface structures, appearance of hydrodynamic features and ablation of surface material. RBS analysis revealed that laser modification induced inter-mixing between the components of individual Ni and Ti layers, with indications of the formation of NiTi intermetallic compounds. An interesting finding is the morphological changes dominant in the Si substrate, whereas the Ni/Ti multilayer structure has mainly undergone changes in the chemical composition.
Creation of laser-induced morphology features, particularly laser-induced periodic surface struct... more Creation of laser-induced morphology features, particularly laser-induced periodic surface structures (LIPSS), by a 532 nm picosecond Nd:YAG laser on crystalline silicon is reported. The LIPSS, often termed ripples, were produced at average laser irradiation fluences of 0.7, 1.6, and 7.9 J cm À2 . Two types of ripples were registered: micro-ripples (at micrometer scale) in the form of straight parallel lines extending over the entire irradiated spot, and nano-ripples (at nanometer scale), apparently concentric, registered only at the rim of the spot, with the periodicity dependent on laser fluence. There are indications that the parallel ripples are a consequence of the partial periodicity contained in the diffraction modulated laser beam, and the nano-ripples are very likely frozen capillary waves. The damage threshold fluence was estimated at 0.6 J cm À2 .
Journal of Optics A: Pure and Applied Optics, 2007
The interaction of a picosecond Nd:YAG laser (wavelength 532 nm, pulse duration 40 ps) with a pol... more The interaction of a picosecond Nd:YAG laser (wavelength 532 nm, pulse duration 40 ps) with a polycrystalline titanium nitride (TiN) film was studied. The TiN thin film was deposited by physical vapour deposition on a silicon substrate. The titanium nitride/silicon system was modified with an energy fluence from 0.2 to 5.9 J cm −2 . Multi-pulse irradiation was performed in air by a focused laser beam. Surface modifications were analysed after 1-100 successive laser pulses. Depending on the laser pulse energy and pulse count, the following phenomena were observed: (i) increased surface roughness, (ii) titanium nitride film cracking, (iii) silicon substrate modification, (iv) film exfoliation and (v) laser-induced periodical surface structures on nano-(NPSS) and micro-dimensions (MPSS).
Surface texturing of the metals, including steels, gained a new dimension with the appearance of ... more Surface texturing of the metals, including steels, gained a new dimension with the appearance of femtosecond lasers. These laser systems enable highly precise modifications, which are very important for numerous applications of metals. The effects of a Ti:sapphire femtosecond laser with the pulse duration of 160 fs, operating at 775 nm wavelength and in two operational regimes -single pulse (SP) and scanning regime, on a high quality AISI 1045 carbon steel were studied. The estimated surface damage threshold was 0.22 J/cm 2 (SP). Surface modification was studied for the laser fluences of 0.66, 1.48 and 2.37 J/cm 2 . The fluence of 0.66 J/cm 2 , in both working regimes, induced texturing of the material, i.e. formation of periodic surface structures (PSS). Their periodicity was in accordance with the used laser wavelength. Finally, changes in the surface oxygen content caused by ultrashort laser pulses were recorded.
The interaction of a transversely excited atmospheric (TEA) CO 2 laser with austenitic stainless ... more The interaction of a transversely excited atmospheric (TEA) CO 2 laser with austenitic stainless AISI 316 and high-speed tool AISI M2 steel is considered. The results have shown that both types of steel were surface modi®ed by the laser beam, for the laser energy densities used. Morphological features on the AISI M2 were more prominent in comparison to a AISI 316 steel. On the AISI M2 steel crater like forms, solidi®ed boundary and hydrodynamical modi®cations were observed, while on the AISI 316 one, corrugation, cracking and resolidi®ed areas were registered. The morphology changes of steel surfaces in dependence of laser pulse temporal shape were analyzed especially. The pulse with a tail for difference of a tail-free pulse, for the same incident peak power density, as a rule caused higher level of damage. #
The interaction of a transversely excited atmospheric (TEA) CO 2 laser, pulse duration of about 2... more The interaction of a transversely excited atmospheric (TEA) CO 2 laser, pulse duration of about 2 ms (FWHM of initial spike 120 ns), with p-type single crystalline silicon doped by boron, was studied. The results have shown that the silicon was surface modi®ed by the laser beam of 12.0 J cm À2 energy density. The energy absorbed from the CO 2 laser beam is converted partially into thermal energy, which generates a series of effects such as melting, vaporisation of molten material, shock waves, etc. Morphological manifestations on the silicon surface are: nonuniform modi®cations (central zone of interaction); wave-like periodical microstructure (inner periphery zone); hydrodynamical structure-like droplets (outer periphery zone). Wave-like microstructure consists of periodic parallel fringes with a period of about 0.8 mm. Formation of these wave-like microstructures is very complex. Explanation includes a consideration of the laser-induced periodic surface structure (LIPSS) effect. The process of the CO 2 laser interaction with silicon was not initially accompanied by plasma. Plasma, in the form of a spark, typically appeared after about 100 cumulated laser pulses. #
The interaction of a transversely excited atmospheric (TEA) CO 2 laser with austenitic stainless ... more The interaction of a transversely excited atmospheric (TEA) CO 2 laser with austenitic stainless AISI 316 and high-speed tool AISI M2 steel is considered. The results have shown that both types of steel were surface modi®ed by the laser beam, for the laser energy densities used. Morphological features on the AISI M2 were more prominent in comparison to a AISI 316 steel. On the AISI M2 steel crater like forms, solidi®ed boundary and hydrodynamical modi®cations were observed, while on the AISI 316 one, corrugation, cracking and resolidi®ed areas were registered. The morphology changes of steel surfaces in dependence of laser pulse temporal shape were analyzed especially. The pulse with a tail for difference of a tail-free pulse, for the same incident peak power density, as a rule caused higher level of damage. #
Interaction of a TEA CO 2 laser, operating at 10.6 m wavelength and pulse duration of 100 ns (FWH... more Interaction of a TEA CO 2 laser, operating at 10.6 m wavelength and pulse duration of 100 ns (FWHM), with a titanium implant in various gas atmospheres was studied. The Ti implant surface modification was typically studied at the moderate laser beam energy density/fluence of 28 J/cm 2 in the surrounding of air, N 2 , O 2 or He. The energy absorbed from the TEA CO 2 laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium implant surface changes and phenomena were observed, depending on the gas used: (i) creation of cone-like surface structures in the atmospheres of air, N 2 and O 2 , and dominant micro-holes/pores in He ambient; (ii) hydrodynamic features, most prominent in air; (iii) formation of titanium nitride and titanium oxide layers, and (iv) occurrence of plasma in front of the implant. It can be concluded from this study that the reported laser fluence and gas ambiences can effectively be applied for enhancing the titanium implant roughness and creation of titanium oxides and nitrides on the strictly localized surface area. The appearance of plasma in front of the implants indicates relatively high temperatures created above the surface. This offers a sterilizing effect, facilitating contaminant-free conditions.
Interaction of a nanosecond transversely excited atmospheric (TEA) CO 2 laser, operating at 10.6 ... more Interaction of a nanosecond transversely excited atmospheric (TEA) CO 2 laser, operating at 10.6 mm, with tungsten-titanium thin film (190 nm) deposited on silicon of n-type (1 0 0) orientation, was studied. Multi-pulse irradiation was performed in air atmosphere with laser energy densities in the range 24-49 J/cm 2 . The energy absorbed from the laser beam was mainly converted to thermal energy, which generated a series of effects. The following morphological changes were observed: (i) partial ablation/exfoliation of the WTi thin film, (ii) partial modification of the silicon substrate with formation of polygonal grains, (iii) appearance of hydrodynamic features including nano-globules. Torch-like plumes started appearing in front of the target after several laser pulses. #
Interaction of an Nd:YAG laser, operating at 1064 or 532 nm wavelength and pulse duration of 40 p... more Interaction of an Nd:YAG laser, operating at 1064 or 532 nm wavelength and pulse duration of 40 ps, with titanium implant was studied. Surface damage thresholds were estimated to 0.9 and 0.6 J/cm 2 at wavelengths 1064 and 532 nm, respectively. The titanium implant surface modification was studied by the laser beam of energy density of 4.0 and 23.8 J/cm 2 (at 1064 nm) and 13.6 J/cm 2 (at 532 nm). The energy absorbed from the Nd:YAG laser beam is partially converted to thermal energy, which generates a series of effects, such as melting, vaporization of the molten material, shock waves, etc. The following titanium/implant surface morphological changes were observed: (i) both laser wavelengths cause damage of the titanium in the central zone of the irradiated area, (ii) appearance of a hydrodynamic feature in the form of resolidified droplets of the material in the surrounding outer zone with the 1064 nm laser wavelength and (iii) appearance of wave-like microstructures with the 532 nm wavelength. Generally, both laser wavelengths and the corresponding laser energy densities can efficiently enhance the titanium/implant roughness. This implant roughness is expected to improve its bio-integration. The process of the laser interaction with titanium implant was accompanied by formation of plasma. #
The interaction of a transversely excited atmospheric (TEA) CO 2 laser with chromium oxynitride (... more The interaction of a transversely excited atmospheric (TEA) CO 2 laser with chromium oxynitride (CrON) coating deposited on a AISI 304 steel substrate was considered. The results have shown that CrON was surface-modified by the laser beam of 45 J/cm 2 energy density. The energy absorbed from the TEA CO 2 laser beam was partially converted into thermal energy, which has generated a series of effects such as melting, vaporization of the molten material, and shock waves in the vapor and in the solid. Morphological manifestations on the CrON coating surface can be summarized as follows: nonuniform features with ablation and appearance of crater-like form (central zone of interaction); appearance of three damaged areas and presence of hydrodynamic effects with resolidified droplets (periphery zone of interaction). In case of applied energy density the interaction of laser radiation with CrON has been always followed by plasma creation in front of the coating. PACS 79.20.Ds; 61.80.Ba
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