Interaction of picosecond and nanosecond pulsed laser radiation on Ti6A14V alloy surface

Istraživanja sprovedena u okviru ove disertacije prvenstveno doprinose razumevanju osnovnh procesa koji se odvijaju prilikom interakcije legure Ti6Al4V i laserske svetlosti. Postojala je mogućnost za ispitivanje parametara laserskog zračenja u širem dijapazonu talasnih dužina, od infracrvenih do ultraljubičastih, pa je ispitivan uticaj talasne dužine na ovu interakciju. Takođe je bilo moguće ispitati uticaj dužine trajanja laserskog impulsa na karakteristike morfoloških promena. Cilj je bio istražiti kako se impulsima laserskog zračenja reda 10-9 i 10-12 sekunde površina može precizno modifikovati, ali uz pažljivo zadate gustine energije i broj impulsa koji padaju na metu. Analitičke metode kojima su okarakterisane promene na uzorcima su bile optička i elektronska mikroskopija, kao i kontaktna i beskontaktna profilometrija. Određen je prag oštećenja Ti6Al4V legure za lasersko zračenje talasnih dužina 222, 266, 308, 532 i 1064 nm. Utvrđeno je da se fine promene na ovom materijalu mogu formirati pri gustinama energija sa vrednostima bliskim pragu oštećenja. Od posebnog je interesa bilo ispitivanje formiranja paralelnih periodičnih struktura na površini, mikrometarskih i nanometarskih dimenzija. Istraživanja ovih interakcija doprinela su boljem razumevanju odgovora legure Ti6Al4V izlaganju jednoimpulsnom i višeimpulsnom ozračivanju laserskim zračenjem.Research conducted in this dissertation mainly contributs to better comprehension of the overall picture of the interaction of the Ti6Al4V and laser light. The effects of lasers that operated in a wide range of wavelengths, from infrared to ultraviolet, were explored and the influence of the wavelength on this interaction also. It was also possible to examine the influence of the length of the laser pulse characteristics of the morphological changes. The aim was to investigate how the alloy surface can be precisely modified by the laser pulses with of 10-9 and 10-12 seconds pulse duration, with careful choice of irradiation conditions, such as energy density and number of applied pulses. Effects of the laser action on the samples were mainly characterized by means of optical and electron microscopy, as well as contact and non - contact profilometry. The damage threshold of Ti6Al4V for laser radiation at wavelengths 222, 266, 308, 532 and 1064 nm was determined. It was found that the fine changes in the alloy can be formed when the energy density of the incident radiation is of values close to the threshold damage. Of particular interest was to examine the formation of periodic parallel structures, microscale and nanoscale dimensions, on the surface morphology. Investigations of these interactions contributed to a better understanding of the response of Ti6Al4V alloy to single – pulse and multi – pulse exposure to laser radiation

The morphological and compositional changes of bimetallic Ti/Al thin film induced by ultra-short laser pulses

Results regarding morphological and compositional changes of bimetallic thin film (BMTF), composed of aluminium (Al) and titanium (Ti) nano-layers, by single fs laser pulses, are presented. Laser irradiation was conducted in the air with focused, linearly polarized laser pulses, the duration being 300 fs, wavelength 515 nm, and pulse energy up to 1.2μJ. Effects of the variations of the pulse energy on the changes were studied. In the experiment, single pulse energy values from 0.03 to 0.08 μ J caused ablation–photomechanical spallation of the upper part of BMTF layer from the Si substrate, without ablation of the whole film. Irradiation at higher pulse energies gradually removed the whole BMTF and even a part of the Si substrate. We explained the influence of different electron–phonon dynamics, in the case of multilayered thin films composed of Al and Ti, on BMTF ablation. Damage/ablation threshold, which is minimal pulse energy/fluence sufficient for starting ablation, was calculated. Graphic abstract: [Figure not available: see fulltext.] © 2021, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature

Fast fabrication of large area concave microlens arrays

A single-step process for rapid fabrication of large-area concave microlens arrays using a diode-pumped solid state (DPSS) laser operating at 473 nm is developed. Using tartrazine sensitized gelatin layer treated with tot’hema - mixture of iron (II)-, manganese (II)- and copper(II)gluconate- (denoted short as tSTG) and a direct laser writing device developed in our laboratory, we could produce 10 000 uniform microlens arrays within 30 min. Uniform microlenses with different diameters and depth can be produced by varying the laser power, exposure time and dye concentration

Picosecond Laser Shock Peening of Nimonic 263 at 1064 nm and 532 nm Wavelength

The paper presents a study on the surface modifications of nickel based superalloy Nimonic 263 induced by laser shock peening (LSP) process. The process was performed by Nd3+:Yttrium Aluminium Garnet (YAG) picosecond laser using the following parameters: pulse duration 170 ps; repetition rate 10 Hz; pulse numbers of 50, 100 and 200; and wavelength of 1064 nm (with pulse energy of 2 mJ, 10 mJ and 15 mJ) and 532 nm (with pulse energy of 25 mJ, 30 mJ and 35 mJ). The following response characteristics were analyzed: modified surface areas obtained by the laser/material interaction were observed by scanning electron microscopy; elemental composition of the modified surface was evaluated by energy-dispersive spectroscopy (EDS); and Vickers microhardness tests were performed. LSP processing at both 1064 nm and 532 nm wavelengths improved the surface structure and microhardness of a material. Surface morphology changes of the irradiated samples were determined and surface roughness was calculated. These investigations are intended to contribute to the study on the level of microstructure and mechanical properties improvements due to LSP process that operate in a picosecond regime. In particular, the effects of laser wavelength on the microstructural and mechanical changes of a material are studied in detail

Wear of diamond-coated cutting tool inserts upon machining of Al-12% Si and glass fiber/polyester resin composites

Results of the wear resistance of the diamond-coated cutting tool inserts upon machining Al-12% Si alloy and glass fiber/polyester resin composites are presented in this paper. The aim of this paper was to demonstrate the advantages of application of cutting tool inserts with the diamond coating over the conventional tungsten-carbide (WC) tools, and to obtain the cheaper serial production (shorter machining time) and satisfactory lifetime of the diamond cutting tool inserts. Surface roughness of the machined samples was measured for both as-received and diamond coated inserts. The diamond microstructure of undamaged part of inserts as well as the appearance of microstructure of diamond coated inserts after machining has been investigated. Results of the behavior of two regimes of preparation of diamond-coated inserts were compared and analyzed. Generally, the wear resistance of the diamond-coated cutting tool is superior over the conventional tool

Na zelenom putu inovacija – vodonik iz laserski potpomognute alkalne elektrolize

The dominant problem that needs to be solved today is the issue of energy sources and how to use them, which must be ecological and sustainable - in a word, green. As the best candidate for a global solution to this problem, hydrogen produced electrolytically stood out as a green fuel with no carbon footprint. However, for a hydrogen-based economy to have a realistic and sustainable perspective in the future, it largely depends on its efficient and economically viable production that would meet the market's needs. Special attention in this paper is devoted to the influence of laser radiation on the possibility of improving the process of alkaline electrolysis for obtaining hydrogen, as well as on increasing the amount of separated hydrogen when the electrolytic cell is directly irradiated with a laser beam during the electrolysis process itself. After the experiments, it was determined that the application of direct irradiation of the electrolyte with a green laser at 532 nm wavelength significantly increases the amount of hydrogen produced and reduces the voltage of the electrolytic process, which is directly related to the increase in the energy efficiency of the overall hydrogen production process.Dominantan problem koji danas treba rešiti je pitanje energenata i načina njihove upotrebe koji moraju biti ekološki i održivi – jednom rečju zeleni. Kao najbolji kandidat za globalno rešenje ovog problema istakao se vodonik proizveden elektolitičkim putem, kao zeleno gorivo bez ugljeničnih otisaka. Da bi ekonomija zasnovana na vodoniku imala realnu i održivu perspektivu u budućnosti, u velikoj meri zavisi od njegove efikasne i ekonomski podobne proizvodnje koja bi zadovoljila potrebe tržišta. Posebna pažnja u ovom radu posvećena je uticaju laserskog zračenja na mogućnost poboljšanja procesa alkalne elektrolize za dobijanje vodonika, kao i na povećanje količine izdvojenog vodonika pri direktnom ozračivanju elektrolitičke ćelije laserskim snopom tokom samog procesa elektrolize. Nakon izvršenih eksperimenata utvrđeno je da se primenom direktnog ozračivanja elektrolita zelenim laserom talasne dužine 532 nm u značajnoj meri povećava količina proizvedenog vodonika i smanjuje napon elektrolitičkog procesa, što je u direktnoj vezi sa povećanjem energetske efikasnosti ukupnog procesa dobijanja vodonika

Comprehensive ablation study of near-IR femtosecond laser action on the titanium-based alloy Ti6Al4V: morphological effects and surface structures at low and high fluences

The surface of a titanium-based alloy Ti6Al4V was subjected to modifications by a near-IR femtosecond Ti:Sapphire laser, emitting at 775 nm pulses of 200 fs duration, in single-pulse and multi-pulse regimes, with up to 400 accumulated pulses, and pulse energies ranging from 2.5 to 250 \upmu J. The whole range of induced effects is presented, from gentle ablation and pattern occurrence to substantial crater formation. Very observable laser-induced parallel periodic surface structures are reported, appearing both within the damage spot area, with low fluences, and at the peripheries of the craters, with higher fluences—but also on crater walls, and inside the crater structures. Damage threshold fluences $$({F}_{\mathrm{th}})$$and the incubation factor $$(\zeta )$$were also determined

Study of noncovalent interactions using crystal structure data in the Cambridge Structural Database

In the recent review it was point out that the crystal structures in the Cambridge Structural Database (CSD), collected, have contributeto various fields of chemical research such as geometries of molecules, noncovalent interactions of molecules, and large assemblies ofmolecules. The CSD also contributed to the study and the design of biologically active molecules and the study of gas storage anddelivery [1].In our group we use analysis of the crystal structures in the CSD to recognize and characterize new types of noncovalent interactionsand to study already known noncovalent interactions. Based on the data from the CSD we can determine existence of the interactions,frequency of the interactions, and preferred geometries of the interactions in the crystal structures. In addition, we perform quantumchemical calculations to evaluate the energies of the interactions. Based on the calculated potential energy surfaces for theinteractions, we can determine the most stable geometries, as well as stability of various geometries. We also can determine theinteraction energies for the preferred geometries in the crystal structures. In the cases where the most preferred geometries in thecrystal structures are not the most stable geometries at the potential energy surface, one can find significant influence of thesupramolecular structures in the crystals.Using this methodology our group recognized stacking interactions of planar metal-chelate rings; stacking interactions with organicaromatic rings and stacking interactions between two chelate rings. The calculated energies indicate strong stacking interactions ofmetal-chelate rings; the stacking of metal-chelate rings is stronger than stacking between two benzene molecules [2]. The data indicateinfluence of the metal and ligand type in the metal chelate ring on the strength of the interactions. Our results also indicate strongstacking interactions of coordinated aromatic rings [3]. Studies of interactions of coordinated water indicate stronger hydrogen bondsand stronger OH/π interactions of coordinated in comparison to noncoordianted water molecule [4,5]. The calculations on OH/Minteractions between metal ion in square-planar complexes and water molecule indicate that these interactions are among the strongesthydrogen bonds in any molecular system [6].The studies on stacking interactions of benzene molecules in the crystal structures in the CSD show preference for interactions at largehorizontal displacements, while high level quantum chemical calculations indicate significantly strong interactions at large offsets; theenergy is 70% of the strongest stacking geometry [7]

Noncovalent interactions of metal complexes and aromatic molecules

Наше истраживање се заснива на анализи података у кристалним структурама из Кембичке базе структурних података (CSD) и на квантнo хемијским прорачунима. Анализа података из CSD-а омогућава да се препознају интеракције у кристалним структурама и да се опишу геометрије ових интеракција, док помоћу квантно-хемијских прорачуна можемо проценити интеракционе енергије и пронаћи најстабилније геометрије интеракција. Користећи ову методологију успели смо да препознамо и опишемо неколико нових типова интеракција. Наше проучавање интеракција планарних метал-хелатних прстенова показало је могућност стекинг интеракција са органским ароматичним прстеновима и интеракције између два хелатна прстена. Израчунате енергије указују на јаке стекинг интеракције метал-хелатних прстенова; стекинг метал-хелатних прстенова је јачи од стекинга између два молекула бензена. Испитивања интеракција координираних молекула воде и амонијака указују на јаче водоничне везе и јаче ОH/π и NH/π интеракције координираних у односу на некоординоване молекуле воде и амонијака. Прорачуни ОH/М интеракција између металног јона у квадратнo планарним комплексима и молекулa воде указују да су ове интеракције међу најјачим водоничним везама у било ком молекулском систему. Студије о ароматичним молекулима указују на стекинг интеракције са великим хоризонталним померањима између два ароматична молекула са значајно јаким интеракцијама, енергија је 70% најјаче стекинг интеракције. Наши подаци такође указују на то да су интеракције алифатичних прстенова са ароматичним прстеном јаче од интеракција између два ароматична молекула, док су алифатично/ароматичне интеракције веома честе у протеинским структурама.Our research is based on analyzing data in crystal structures from the Cambridge Structural Database (CSD) and on quantum chemical calculations. The analysis of the data from the CSD enable to recognize interactions in crystal structures and to describe the geometries of these interactions, while by quantum chemical calculations we can evaluate interaction energies and find the most stable interaction geometries. Using this methodology we were able to recognize and describe several new types of noncovalent interactions. Our study of planar metal-chelate rings interactions showed possibility of chelate ring stacking interactions with organic aromatic rings, and stacking interactions between two chelate rings. The calculated energies indicate strong stacking interactions of metalchelate rings; the stacking of metal-chelate rings is stronger than stacking between two benzene molecules. Studies of interactions of coordinated water and ammonia indicate stronger hydrogen bonds and stronger OH/π and NH/π interactions of coordinated in comparison to noncoordianted water and ammonia. The calculations on OH/M interactions between metal ion in square-planar complexes and water molecule indicate that these interactions are among the strongest hydrogen bonds in any molecular system. The studies on aromatic molecules indicate stacking interactions at large horizontal dispacements between two aromatic molecules with significantly strong interacitons, the energy is 70% of the strongest stacking geometry. Our data also indicate that stacking interactions of an aliphatic rings with an aromatic ring are stonger than interactions between two aromatic molecules, while aliphatic/aromatic interactions are very frequent in protein structures

Study of noncovalent interactions using crystal strucutre data and quantum chemical calculations

The analysis of the crystal structures in the CSD was used to recognize and characterize new types of noncovalent interactions. It was also used to study already known noncovalent interactions. Based on the data from the CSD we can determine existence of the interactions, frequency of the interactions, and preferred geometries of the interactions in the crystal structures [1,2]. The quantum chemical calculations were performed to evaluate the energies of the interactions. For the preferred geometries in the crystal structures we can calculate the interaction energies. By calculating potential energy surfaces for the interactions, we can determine the most stable geometries, as well as stability of various geometries [1,2]. Using this methodology our group recognized stacking interactions of planar metal-chelate rings; stacking interactions with organic aromatic rings, and stacking interactions between two chelate rings. The calculated energies showed that the stacking of metal-chelate rings is stronger than stacking between two benzene molecules. Studies of interactions of coordinated ligands indicate stronger noncovalent interactions that interactions of noncoordinated molecules [2]. REFERENCES [1] Ninković, D. B., Blagojević Filipović, J. P., Hall, M. B., Brothers, E. N., Zarić, S. D. (2020) ACS Central Science, 6, 420. [2] Malenov, D. P., Zarić, S. D. (2020) Cood. Chem. Rev. 419, 213338