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The Ti−45Nb (wt.%) alloy properties were investigated in relation to its potential biomedical use. Laser surface modification was utilized to improve its performance in biological systems. As a result of the laser treatment, (Ti,Nb)O scale was formed and various morphological features appeared on the alloy surface. The electrochemical behavior of Ti−45Nb alloy in simulated body conditions was evaluated and showed that the alloy was highly resistant to corrosion deterioration regardless of additional laser surface modification treatment. Nevertheless, the improved corrosion resistance after laser treatment was evident (the corrosion current density of the alloy before laser irradiation was 2.84×10−8 A/cm2, while that after laser treatment with 5 mJ was 0.65×10−8 A/cm2) and ascribed to the rapid formation of a complex and passivating bi-modal surface oxide layer. Alloy cytotoxicity and effects of the Ti−45Nb alloy laser surface modification on the MRC-5 cell viability, morphology, and proliferation were also investigated. The Ti−45Nb alloy showed no cytotoxic effect. Moreover, cells showed improved viability and adherence to the alloy surface after the laser irradiation treatment. The highest average cell viability of 115.37% was attained for the alloy laser-irradiated with 15 mJ. Results showed that the laser surface modification can be successfully utilized to significantly improve alloy performance in a biological environment.

This paper presents a study and comparison of surface effects induced by picosecond and nanosecond laser modification of a Ti6Al4V alloy surface under different ambient conditions: air and argon- and nitrogen-rich atmospheres. Detailed surface characterization was performed for all experimental conditions. Damage threshold fluences for picosecond and nanosecond laser irradiation in all three ambient conditions were determined. The observed surface features were a resolidified pool of molten material, craters, hydrodynamic effects and parallel periodic surface structures. Laser-induced periodic surface structures are formed by multi-mode-beam nanosecond laser action and picosecond laser action. Crown-like structures at crater rims are specific features for picosecond Nd:YAG laser action in argon-rich ambient conditions. Elemental analysis of the surfaces indicated nitride compound formation only in the nitrogen-rich ambient conditions. The constituents of the formed plasma were also investigated. Exploring the impact of process control parameters on output responses has been undertaken within the context of laser modification under different environmental conditions. Parametric optimization of the nanosecond laser modification was carried out by implementing an advanced method based on Taguchi’s parametric design and multivariate statistical techniques, and optimal settings are proposed for each atmosphere.

Tungsten disulfide, a transition metal dichalcogenide, has numerous applications as active components in gas- and chemical-sensing devices, photovoltaic sources, photocatalyst substrates, etc. In such devices, the presence of water in the sensing environment is a factor whose role has not been well-understood. To address this problem, the in situ probing of H2O molecule adsorption on WS2 films supported on solid substrates has been performed in a near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) setup. Instead, on the individual nanoflakes or spray-coated samples, the measurements were performed on highly transparent, homogeneous, thin films of WS2 nanosheets self-assembled at the interface of two immiscible liquids, water and toluene, transferred onto a solid substrate by the Langmuir-Schaefer technique. This experiment shows that edge defects in nanoflakes, tungsten dangling bond ensuing the exfoliation in the liquid phase, represent active sites for the WO3, WO3-x, and WO3·nH2O formation under ambient conditions. These oxides interact with water molecules when the WS2 films are exposed to water vapor in the NAP-XPS reaction cell. However, water molecules do not influence the W-S chemical bond, thus indicating the physisorption of H2O molecules at the WS2 film surface. © 2023 American Chemical Society.

In this study, surface modification of the graphite plate electrode induced by laser irradiation treatment is presented. The electrode was irradiated in air and argon atmosphere using the Nd:YAG laser. Surface modifications were analyzed by profilometric measurements. The influence of irradiation atmosphere on electrochemical active surface of graphite electrode was observed using cyclic voltammetry. The results indicate that electrochemical active surface area of graphite electrode was increased using laser irradiation, and highest value was obtained by laser irradiation in air atmosphere. These cognitions can be useful for application of laser-treated electrode in environmental chemistry for detection or removal of organic pollutants.

The interaction of lasers with metals has been studied for decades, and has been especially intensified lately, due to the development of new, efficient pulsed lasers. Titanium has a number of excellent properties, making it applicable in various modern technologies. Treatment and processing of titanium is possible with various techniques, and the application of lasers gives a special quality, such as high precision machining or obtaining specific structures on the surface which cannot be generated by other methods. During our research, surface processing of titanium was conducted by various pulsed lasers: nanosecond CO2 laser, picosecond Nd:YAG laser and femtosecond Ti: sapphire laser. In order to find the optimal conditions for surface modification of titanium, the influence of different laser parameters (wavelength, pulse duration, pulse energy, etc.), as well as the influence of the ambient, was examined. The titanium samples were irradiated in different environments, ie. in air, oxygen, nitrogen, carbon dioxide, helium and in vacuum, which affected the chemical composition and morphology of the target surface.

Silicon-based nanoparticles (SiNPs) attract authors’ attention due its application prospects in a mutual field, from energy storage to bio-imaging. One of the most prominent methods for synthesis of SiNPs is pulsed laser ablation in liquid media (LAL), because it is simple, and it provides the minimum of contamination of the sample produced. Employed pulsed lasers in LAL are ns- and ps-, and the usage of fs- lasers are reported recently, as well. The objects of the LAL analyses are ablated craters on the Si target surface and, predominantly, the ablated material. Here, SiNPs are synthesized by ps- laser (150 ps, 1064 nm) ablation of Si single-crystal plates in de-ionized water. The focus of the work is the impact of the additional continuous wave (CW) laser (532nm) on the properties of the ablated material, i.e. SiNPs produced. The comprehensive analyses were performed, including the SiNPs’ size distribution, agglomeration abilities, aging, chemical properties (amount of oxygen and its distribution within the particles), and photoluminescence (PL) properties of the solution produced. It is demonstrated that PL properties of obtained SiNPs solution are impacted by introducing the CW laser in the ablation process. The peculiarity lies in the fact that such impact depends on both the PL excitation wavelength and the power of the introduced CW laser, which might open the possibility of successful tailoring of SiNPs produced by LAL.

Titanium alloys are finding increasing use as biomaterials due to their low elastic modulus and high damage tolerance. However, the somewhat inadequate alloy surface performance can impede their biomedical application. Surface modification methods have been therefore developed to improve the alloys' surface bioactivity and osseointegration. Laser treatment allows the alloy surface to be modified, providing it with new functionalized surface chemistry and morphology, without compromising the rest of the material properties. Thus, the aim of the study was to examine the laser-induced alterations generated on the Ti-45Nb alloy surface by an ultrashort pulsed laser. The obtained results reveal that laser beam interaction with the target material led to the formation of significant alterations in surface morphology. Surface craters, microcracks, and surface features in the form of periodic and rippled structures and solidified droplets can be observed in the irradiated area. Also, it was found that the higher damage degree along with the material depth and the higher surface roughness were achieved during the irradiation in the argon atmosphere due to the formation of the more pronounced morphological changes on the alloy surface that are induced by higher laser ablation. Furthermore, obtained results showed that alloy surface modification in air, argon, and nitrogen atmosphere additionally caused changes in the surface chemical composition. Namely, after irradiation, the presence of oxygen was observed in the central irradiated area indicating the formation of bioactive Ti-oxide surface film with content that varies with the irradiation parameters variation. Therefore, laser beam irradiation can be singled out as the surface modification method for efficient inducement of the specific surface characteristics that can provide titanium alloys with enhanced osseointegration properties.

Interakcija lasera sa metalima proučava se decenijama, a posebno je intenzivirana u poslednje vreme, usled razvoja novih, efikasnih impulsnih lasera. Istraživanja u ovoj tezi su fokusirana na titanijum, koji poseduje niz odličnih osobina, što ga čini primenljivim u različitim savremenim tehnologijama. Obrada i procesiranje titanijuma mogući su različitim tehnikama, a primena lasera daje poseban kvalitet, poput visoke preciznosti obrade ili dobijanja specifičnih struktura na površini koje nije moguće generisati drugim metodama. Cilj ove doktorske disertacije je eksperimentalna optimizacija površinskog modifikovanja titanijuma impulsnim nano-, piko-, i femto-sekundnim laserima. Kao izvori laserskog zračenja korišćeni su nanosekundni CO2 laser, pikosekundni Nd:YAG, i femtosekundni Ti:safirni laser. Poznato je da stepen površinske modifikacije mete zavisi od parametara laserskog zračenja (talasne dužine, dužine trajanja impulsa, energije impulsa, itd.), od geometrije fokusiranja, od stanja površine i apsorptivnosti mete, kao i od sredine u kojoj se interakcija odvija. U cilju nalaženja optimalnih uslova za površinsku modifikaciju titanijuma ispitan je uticaj pojednih parametara lasera, kao i uticaj ambijenta. Utvrđeno je da primenjeni intenziteti laserskog zračenja dovode do modifikacija površine mete, pri čemu impulsi različitog trajanja drugačije modifikuju titanijumsku metu. Nanosekundni i pikosekundni laseri dovode do difuznog karaktera oštećenja uz prisustvo termalnih efekata, dok korišćenje femtosekundnih impulsa rezultuje u bolje definisanim oblastima oštećenja. Pokazano je da promena sredine ozračivanja presudno utiče na hemijski sastav i morfologiju površine mete., The interaction of lasers with metals has been studied for decades, and has been especially intensified lately, due to the development of new, efficient pulsed lasers. Research in this thesis is focused on titanium, which has a number of excellent properties, making it applicable in various modern technologies. Treatment and processing of titanium is possible with various techniques, and the application of lasers gives a special quality, such as high precision machining or obtaining specific structures on the surface which cannot be generated by other methods. The goal of this doctoral dissertation is the experimental optimization of surface processing of titanium by pulsed nano-, pico-, and femto-second lasers. Laser radiation sources used were nanosecond CO2 laser, picosecond Nd:YAG, and femtosecond Ti: sapphire laser. It is known that the degree of surface modification of the target depends on laser radiation parameters (wavelength, pulse duration, pulse energy, etc.), focus geometry, the state of the surface and the absorption of the target, as well as from the environment in which the interaction takes place. In order to find the optimal conditions for surface modification of titanium, the influence of certain laser parameters, as well as the influence of the ambient, was examined. It has been found that the applied laser radiation intensities lead to the modification of the target surface, and that the pulses of different duration modify the titanium target in various way. Nanosecond and picosecond lasers lead to a diffuse character of damaged area with the presence of thermal effects, while the use of femtosecond pulses results in better defined area of damage. It has been shown that the change in the ambient of the irradiation affects the chemical composition and morphology of the target surface.

Surface modifications of metallic biomaterials can in great merit, improve the properties of the hard-tissue implants and in that way contribute to the success of the surgical implantation process. Coating deposition stands out as one of the many surface-modifying techniques that can be used to improve implant surface properties and, in turn, induce successful osseointegration. Deposition of the TiO2 layer on the surface of the metallic implants has a great potential to enhance not only their osseointegration ability but also their biocompatibility and corrosion resistance. In the present study, the possibility of successful deposition of the TiO2 layer on the surface of commercially pure titanium (CP-Ti), as the most commonly used metallic implant material, by spraying the colloidal nanoparticles aqueous solution in the electric discharge plasma at atmospheric pressure was investigated. To characterize the colloidal TiO2 nanoparticle solution, used for the coating deposition process, transmission electron microscopy (TEM) was utilized, while scanning electron microscopy (SEM) and optical profilometry were used to investigate the deposited surface layer morphology and quality. Estimation of the deposited film quality and texture was used to confirm that the arc plasma deposition technique can be successfully used as an advanced and easy-to-apply method for coating the metallic implant material surface with the bioactive TiO2 layer which favors the osseointegration process through the improvement of the implant surface properties. The TiO2 coating was successfully deposited using the arc plasma deposition technique and covered the entire surface of the CP-Ti substrate without any signs of coating cracking or detachment.

The behavior of 16Cr3Al ODS steel (oxide dispersion strengthened steel), widely employed structural fusion material, under high-intensity laser radiation with intensity up to 10(14)W/cm(2) was investigated in air, helium and vacuum surrounding. Employed system was 65 fs laser at 804 nm, with applied pulse energy up to 5.25 mJ. Morphological effects were studied - cracking, crater parameters (depth, cross-section), LIPSS (laser-induced periodic surface structures) formation at the crater periphery, hydrodynamic effects, as well as chemical variations on the surface. Ablation thresholds were also determined for all three ambiences (for 100 applied pulses), and they were 0.30 J/cm(2), 0.23 J/cm(2) and 0.39 J/cm(2) in air, helium and vacuum, respectively. Plasma occurred in all experiments and it was most prominent in vacuum due to strongest laser-material coupling.

The application of an alternative laser-induced breakdown spectroscopy (LIBS) method based on transversely excited atmospheric (TEA) CO2 laser was investigated for the first time for estimating the hardness of metallic materials. The human eye-safe (TEA) CO2 laser, operating at 10.6 µm, was used for plasma generation. The LIBS spectra were recorded by employing a cost-effective CCD camera for the time-integrated and spatial resolved measurements. The cast iron and aluminum alloys samples with different hardness have been tested. The ratio between the magnesium ionic and neutral lines in LIBS spectra was applied for estimating the material hardness. In addition, the hardness of all samples included in this study was determined using the conventional method for material hardness determination, i.e. Vickers hardness test. The linear dependence of magnesium lines intensity ratio on the sample’s hardness was obtained for both kinds of materials. Profilometric measurements were used to verify that the newly-introduced method is almost nondestructive for the investigated metals. The results obtained in the present work confirmed the potential of using this original LIBS system not only for the fast elemental analysis but also for the direct estimation of the hardness of metals and alloys. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.

Optical emission studies of graphite plasma induced by infrared (IR) Transversely Excited Atmospheric carbon dioxide (TEA CO2) laser pulses in ambient air at atmospheric pressure are reported. The plasma was induced at relatively low-irradiance, up to 40 MW cm−2, and the plasma emission was recorded using time-integrated LIBS measurements. The time profile of the 160 mJ laser pulse is composed of a short, 100 ns long initial spike, and a long 2 μs tail. About 60 mJ is contained in the initial pulse, and the 100-mJ tail contribution is favorable for extended plasma absorption that promotes creation of long-lasting highly-excited plasma. With laser pulse focused behind the target surface, recorded spectra consisted of intensive, sharp atomic and single charged ionic spectral lines of carbon, and trace elements, e.g. Ca, Cu, V, Si, and Ti. Good signal to background ratios obtained indicate potential application in the analysis of impurities in graphite, and also elemental analysis of other materials with high carbon content. The average electron number density was determined from Stark-broadened emission profile of C I 247.9 nm line, and the line intensity ratio of CII 250.9 nm/C I 247.9 nm line pair was used for estimation of ionization temperature. Depending on the applied fluence, electron density was in the range 2.6–4.8 × 1017 cm−3, and ionization temperature between 19,000 and 22,000 K. Beside line spectra, intensive and well-developed band spectra of diatomic molecules C2 (Swan system), and CN (violet system) were obtained. Pulse energy threshold for observation of molecular emission was 50 mJ. From the spectroscopic studies of the emission bands, the rotational and vibrational temperatures were estimated by comparing the experimental and simulated emission spectra. Vibrational and rotational temperatures deduced from Δν = 0 sequences of the Swan system of C2 were 3100 K and 3850 K, respectively. The most intense band of the CN violet system showed strong self-a

This study was carried out to examine the applicability of original laser-induced breakdown spectroscopy (LIBS) setup for determination of the surface hardness of lead glass as a function of its chemical composition. For this purpose, a set of five lead glass samples with different amount of ZrO2 was prepared. The LIBS measurements were carried out using TEA CO2 laser in the air at atmospheric pressure and without sample preparation. A ratio of the intensity between the Zr(II) 355.66 nm and Zr(I) 360.12 nm emission lines has been used to examine the hardness of the material. In addition, the surface hardness of glass samples was determined by Vickers’s indentation tests. Obtained results indicate a linear relationship of the measurements of hardness in glass samples between the LIBS and Vickers method. To show that LIBS based on TEA CO2 laser is an almost nondestructive technique, profilometric surface analysis was used. The proposed LIBS system is suitable not only for a spectrochemical analysis but also as an easy to use and cost-effective way to measure the surface hardness for all types and shapes of glass samples which are in some cases difficult to examine by standard Vicker’s method. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Time-integrated optical emission spectroscopy was applied for the analysis of emission spectra, and determination of electron densities and excitation temperatures of basalt plasma induced by 10.6 micron laser radiation. The plasma was studied in air, argon and carbon dioxide, under pressure of 10, 50, and 100 mbar. The plasma emission intensity was found to be strongly dependent on the nature of the ambient gas and its pressure. The highest emission intensities and signal to noise ratios were obtained in argon. Depending on the composition and pressure of the surrounding atmosphere, the values of plasma temperature varied between 14,400 K (air at 10 mbar) and 17,100 K (carbon dioxide at 100 mbar). Similarly, the electron number density varied between 3 × 1016 cm−3 (10 mbar air) and 1.6 × 1017 cm−3 (100 mbar CO2). The observed behavior was correlated with the properties of the studied gases, in particular, their mass, thermal conductivity and ionization energy, and the role of the ambient gas in controlling the efficiency of laser-target coupling, laser-plasma interaction and plasma shielding. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

The possibility of interlayer mixing in a Ti/Ta multilayer system, induced by laser irradiation, was the main purpose of these experiments. Ti/Ta multilayer system, consisting of ten alternating Ti and Ta thin films and covered by slightly thicker Ti layer, was deposited on Si (100) wafers to a total thickness of 205 nm. Laser irradiation was performed in air by picoseconds Nd:YAG laser pulses in defocused regime with fluences of 0.057 and 0.11 J cm−2. Laser beam was scanned over the 5 × 5 mm surface area with different steps along y-axes. Structural and compositional characterisation was done by auger electron spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, and scanning electron microscopy. Laser processing at lower fluence caused only oxidation of the top Ti layer, despite of the number of applied laser pulses. Interlayer mixing was not observed. Application of laser pulses at fluence of 0.11 J cm−2caused partial and/or complete ablation of deposited layers. In partially ablated regions considerable mixing between Ti and Ta films was registered.

A study of the surface modification of titanium CP grade 2 implant/target with high intensity picosecond (Nd:YAG) laser, operating at 1064 nm wavelength and pulse duration of 40 ps, in gaseous (air) and liquid (water) medium, is presented. The exposure of Ti to a laser pulse energy of 17 mJ in both media - gaseous and liquid, induced specific surface features and phenomena: (i) enhancement of the implant surface roughness (higher in water). In this context, the damage depth is more prominent in water (as high as 40 mu m) vs. air (similar to 14 mu m). Also, the appearance of laser induced periodic surface structures (LIPSS) is recorded in both media, at periphery area, while in water they are registered at lower pulse count; (ii) variation of chemical surface content depending on the applied medium. Thus, in the central irradiation region, the oxygen was absent in air while its concentration was relatively high (6.44 wt%) in case of water; (iii) possibility of direct collection of synthesized titanium based nanoparticles in water environment, and (iv) formation of the plasma above the sample in both mediums, more volumetrically confined in water. These investigations showed that surface structuring and observed phenomena are in strong correlation with the medium used. The liquid - water seems like the medium of choice in regard to titanium implant biocompatibility and bio-activity (the water is a favorable medium for build-up of the oxide layer which affects bioactivity). The process of laser interaction with titanium implant targets was accompanied by the formation of plasma plume, which provides the additional sterilizing effect facilitating contaminant-free conditions. (C) 2017 Elsevier B.V. All rights reserved.

Surface changes created by interaction of transversely excited atmospheric carbon dioxide (TEA CO2) laser with titanium target/implant in nitrogen and carbon dioxide gas were studied. TEA CO2 laser operated at 10.6 mu m, pulse length of 100 ns and fluence of similar to 17 J/cm(2) which was sufficient for inducing surface modifications. Induced changes depend on the gas used. In both gases the grain structure was produced (central irradiated zone) but its forms were diverse, (N-2: irregular shape; CO2: hill-like forms). Hydrodynamic features at peripheral zone, like resolidified droplets, were recorded only in CO2 gas. Elemental analysis of the titanium target surface indicated that under a nitrogen atmosphere surface nitridation occurred. In addition, irradiation in both gases was followed by appearance of plasma in front of the target. The existence of plasma indicates relatively high temperatures created above the target surface offering a sterilizing effect.

Multilayers consisting of five (Al/Ti) bilayers were deposited on (100) silicon wafers. On top was deposited the Ti layer, aimed at preventing Al from diffusing to the surface upon laser treatment. The total thickness of the thin-film structure was 200 nm. Laser irradiations with Nd:YAG picoseconds laser pulses in the defocused regime were performed in air. Laser beam energy was 4 mJ and laser spot diameter on the sample surface was 3 mm (fluence 0.057 J cm(-2)). The samples were treated with different numbers of laser pulses. Structural characterizations were performed by different analytical methods and nano-hardness was also measured. Laser processing induced layer intermixing, formation of titanium aluminides, oxidation of the surface titanium layer and enhanced surface roughness. Aluminum appears at the sample surface only for the highest density of laser irradiation. Laser processing induces increment of nano-hardness by approximately 20% and decrease of residual Youngs modulus for a few percentages from the starting value of the untreated samples. These results can be interesting toward achieving structures with a selective extent of Al-Ti reactivity in this multilayered system, within the development of biocompatible materials.

Metallic biomaterials should exhibit excellent biocompatibility, high corrosion resistance and low elastic modulus which are close to that of human bones. It was shown that in this sence Ti-Ta alloys have considerably better mechanical properties compared to pure titanium or tantalum [1, 2]. The main purpose of these experiments was investigation of possibility to induce interlayer mixing in an Ti/Ta immiscible multilayer system by laser irradiation.The absence of interlayer mixing was previously shown on this system during the Ar+ ion irradiation up to relatively high fluence of 2x1016 ions cm-2 [3]. The system consisted of ten alternate Ti and Ta thin films (~18 nm each) and covered by slightly thicker Ti layer (~27 nm) on the top with the purpose of creating an appropriate porous structure very important for potential biocompatibility [4]. Structure was deposited on Si (100) wafers to a total thickness of 205 nm. Laser irradiation was performed in air by picoseconds Nd: YAG laser. Defocused laser pulses had a laser spot on the sample surface of 3 mm in diameter and fluences of 0.057 and 0.11 J cm-2 . Laser beam was scanned over the 5x5 mm2 surface area with different steps along y-axes to provide a variation in deposited energy density. For structural and compositional characterisation following methods were used: Auger electron spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. The obtained results show that laser processing at a lower fluence causes only oxidation of the top Ti layer, invariable to the number of applied laser pulses and no interlayer mixing was observed. Appliance of laser pulses at fluence of 0.11 J cm-2 , on the other hand, caused significant increase of surface roughness and partial and/or complete ablation of deposited layers, but in partially ablated regions considerable mixing between Ti and Ta films was registered. These experiments indicate that the use of picoseconds laser pulses w

Surface changes created by interaction of transversely excited atmospheric carbon dioxide (TEA CO2) laser with titanium target/implant in nitrogen and carbon dioxide gas were studied. TEA CO2 laser operated at 10.6 mu m, pulse length of 100 ns and fluence of similar to 17 J/cm(2) which was sufficient for inducing surface modifications. Induced changes depend on the gas used. In both gases the grain structure was produced (central irradiated zone) but its forms were diverse, (N-2: irregular shape; CO2: hill-like forms). Hydrodynamic features at peripheral zone, like resolidified droplets, were recorded only in CO2 gas. Elemental analysis of the titanium target surface indicated that under a nitrogen atmosphere surface nitridation occurred. In addition, irradiation in both gases was followed by appearance of plasma in front of the target. The existence of plasma indicates relatively high temperatures created above the target surface offering a sterilizing effect.

Measurements and analysis of broadened profiles of the H-alpha line following laser-induced optical breakdown are presented. A primary goal of this work is to weigh the feasibility of pulsed CO2 laser to produce analytically useful plasma in aqueous aerosol at open atmosphere. Transversally Excited Atmospheric pressure (TEA) CO2 laser lasing at 10.6 µm was used to generate atmospheric pressure breakdown plasma. Plasma was created by striking the laser pulses over the solid metal interface through which aqueous aerosol drifts carried by a current of argon [1]. Laser pulse duration was about 100 ns and energy of 160 mJ. Emission spectra were recorded by time-integrated space-resolved measurement technique using a 2-m spectrograph equipped with a CCD camera. The applied experimental setup gives the spectral resolution of 0.0086 nm/pix and instrumental line width of 0.02 nm. H-alpha line was recorded at successive distances from the surface of the metal interface. H-alpha line profiles were analyzed using Full-widths at half-maximum (FWHM) parameter. The pseudo-Voight function consisting of a weighted sum of a Gaussian function and a Lorenzian function has been found to fit the H-alpha line profile successfully [2, 3]. On the very surface of the interface the Lorenz width was found to be 1.5 nm and gradually increases to about 1.8 nm at distances of 3-5 mm above the surface. This corresponds to the electron density range 1.5-2×1023 m-3 . Thereafter, the line profile width steeply declines to distances of 7 mm that is the diameter of the stream of the aerosol. The Gauss width has more complex spatial shape. In the range of 0 mm to 3 mm from the surface the Gauss width was about 0.25 nm and then reaches maxima of about 0.4 nm at distances 4-5 mm from the surface. The appropriate red shift of the H-alpha line was also recorded. Maximum shift of about 0.06 nm was recorded at distances of 4-5 mm from the surface. The spatial position of the maximal red shift corresponds to t

Interaction of a TEA CO2 laser with a titanium implant in vacuum (air pressure 0.1 mbar) was studied. The laser operates at 10: 6 mu m with pulse duration of 100 ns (FWHM). The surface alternations were studied at the moderate laser beam energy density/fluence of 52 J/cm(2). The energy absorbed from the TEA CO2 laser beam was partially converted to thermal energy, which generated 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: (1) creation of superficial damage which takes crater-shaped form at a higher number of accumulated laser pulses. Maximal depth of the damage was 9 mu m for 500 laser pulses. The damage cross-section had a conical form; (2) melt pools, inside the damage region, especially prominent for higher number of accumulated pulses; (3) preservation of chemical surface composition in central, and changes at the peripheral region, and (4) occurrence of plasma in front of the implant. The results have shown that under the applied experimental conditions, TEA CO2 laser can effectively be applied for enhancing the titanium implant roughness and creation of surface chemical changes. The appearance of plasma in front of the implant offers a sterilizing effect, facilitating contaminant-free conditions.

The present work studies the possibility of using pulsed Transversely Excited Atmospheric (TEA) carbon dioxide laser as an energy source for laser-induced breakdown spectroscopy (LIBS) analysis of rocks under simulated Martian atmospheric conditions. Irradiation of a basaltic rock sample with the laser intensity of 56 MW cm(-2), in carbon-dioxide gas at a pressure of 9 mbar, created target plasma with favorable conditions for excitation of all elements usually found in geological samples. Detection limits of minor constituents (Ba, Cr, Cu, Mn, Ni, Sr, V, and Zr) were in the 3 ppm-30 ppm range depending on the element. The precision varied between 5% and 25% for concentration levels of 1% to 10 ppm, respectively. Generally, the proposed relatively simple TEA CO2 laser-LIBS system provides good sensitivity for geological studies under reduced CO2 pressure. (C) 2016 Elsevier B.V. All rights reserved.

A short overview of Laser Induced Breakdown Spectroscopy (LIBS) with emphasis on the new trends is presented. Nowadays, due to unique features of this technique, LIBS has found applications in a great variety of fields. Achievements in the application of LIBS in nuclear area, for hazardous materials detection and in geology were considered. Also, some results recently obtained at VINCA Institute, with LIBS system based on transversely excited atmospheric (TEA) CO2 laser, are presented. Future investigations of LIBS will be oriented toward further improvement of the analytical performance of this technique, as well as on finding new application fields.

Multilayer structures, consisting of 15 alternate Ti and Al thin films, and covered with thicker Ti layer, were deposited on a Si substrate to a total thickness of 900 nm. Laser treatment was performed in air by defocused Nd:YAG laser pulses (150 ps) with energies of 7 and 10 mJ covering an area of 3 mm in diameter (fluences were 0.1 and 0.14 J cm(-2) respectively). Laser beam was scanned over the 5 x 5 mm surface area. Characterizations were done by Auger electron spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy and transmission electron microscopy. Nano-hardness measurements were performed by Vickers method with applied load of 5 mN. Obtained results show that irradiation with picosecond laser pulses leads to the formation of Ti2O3 in the top Ti layer. This process is more pronounced for higher energy and/or higher number of applied laser pulses. On the surface of all samples very thin amorphous TiO2 layer was formed. Laser irradiation induces surface melting and transformation of relatively flat surface into mosaic shaped one for samples treated with higher energy and higher number of applied laser pulses. Irradiation at smaller energy did not induce any noticeably mixing between Al and Ti beneath the covered Ti layer. Some mixing of Al and Ti appeared in the sample irradiated with higher energy of laser pulses. (C) 2015 Elsevier B.V. All rights reserved.

The applicability of a nanosecond infrared (IR) transversely excited atmospheric (TEA) CO2 laser, operating at 10.6 mu m and 100 ns pulse length (initial spike), induced plasma under reduced air pressure for spectrochemical analysis of bronze and brass samples was investigated. The plasma consisted of two clearly distinguished and spatially separated regions and expanded to a distance of about 10 mm from the surface. The elemental composition of the samples was determined using a time-integrated space-resolved laser-induced plasma spectroscopic (TISR-LIPS) technique. Sharp and well-resolved spectral lines mostly atomic, and negligibly low background emission, were obtained from a plasma region 7 mm from the target surface. Good signal to background and signal to noise ratios were obtained. The estimated detection limits for the trace elements Mg, Fe, Al and Ca were in the order of 10 ppm in bronze and around 50 ppm in brass. Damage on the investigated samples induced by TEA CO2 laser radiation was negligible.

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 gm. 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 in this zone was around 7000 K. The favorable signal to background ratio obtained in this plasma region indicates possible analytical application of TEA CO2 laser produced copper plasma. Detection limits of trace elements present in the Cu sample were on the order of 10 ppm (parts per million). Time-resolved measurements of spatially selected plasma zones were used to find a correlation between the observed spatial position and time delay.