Action Of Laser Radiation Research Articles

Lifting of Dust Particles under the Action of Laser Radiation on a Chondritic Target and the Possibility of Modeling Plasma–Dust Processes on the Lunar Surface

The first investigation devoted to experimental modeling of the lift of dust particles by shock wave over a target surface has been performed on the Saturn setup for studying the interaction of laser radiation with a porous chondritic target surface bearing finely dispersed talc particles. Results of experimental modeling can be used to describe the lift of dust particles from the zones of nonlinear and linear elastic deformation of a regolith substance characterizing a meteoroid impact on the Moon’s surface.

Dynamic Effects of Laser Action on Quasi-Two-Dimensional Dusty Plasma Systems of Charged Particles.

We present the results of an experimental study of the behavior of a colloidal plasma system formed by copper-coated and uncoated polymer particles under the action of laser irradiation. A comparative study of particle velocity distribution profiles depending on the power of the pushing laser was conducted. In the case of uncoated melamine-formaldehyde (MF) particles, we observed the well-known action of light pressure, causing shear stress in the colloidal plasma structure and leading to the occurrence of a laminar flow within the affected area. For the copper-coated MF particles, we revealed some additional patterns of behavior for the dust particles, i.e., kinetic temperature growth due to laser radiation absorption by the copper coating, as well as the appearance of chaotic particle motion. We believe that this happens due to the existence of defects in the coating, causing asymmetric heating of the particles, which in turn leads to chaotic deviations of the photophoretic force pushing the particles in different directions.

Mathematical modeling of the process of selective laser melting of Ti-6Al-4V titanium alloy powder

A digital (finite element) model has been developed for heating and melting of a layer of metal powder under conditions of its heating by a laser heat flux using a modern standard software product for assessing the geometric parameters of a molten bath brought about by the action of laser radiation on a layer of Ti-6Al-4V titanium alloy metal powder. The model takes into account latent heat released during the phase transition of the material; melting of the material in the temperature range of solidus and liquidus; radiation and convection from the surface of a layer of metal powder. It has been established that the formation of interlayer defects arising from inadequate penetration between layers or insufficient overlap between tracks is the main reason for the formation of porosity in materials synthesized by selective laser melting technology. So the depth of the molten bath should be at least 1.5 of the layer thickness for the synthesis of dense material. The results of numerical simulations made it possible to determine the range of technological scanning parameters upon application of which a melt pool with a depth of more than 75 m is formed.

Intensification of growth of Schizophyllum commune using laser irradiation

The growth processes of the basidiomycete fungus Schizophyllum сommune under the action of laser irradiation have been studied. To determine the growth rate of strains S.c.-01, S.c.-02, S.c.-03 of the fungus S. commune mycelium was cultured on agar medium (CGA) with different concentrations of glucose (10, 8, 6 and 4 g/dm3 ). In order to study the effect of laser irradiation on the growth of the fungus S. commune, the mycelium was irradiated with LED lasers: BRP — 3010-5, with red spectrum radiation with a wavelength of 635 nm; BBP — 3010-5 is a blue spectrum with a wavelength of 405 nm and BGP — 3010-5 is a green spectrum with a wavelength of 532 nm. Effective modes of photoactivation of mycelium by coherent light are determined. The results are obtained, which allow to state that the most effective for all studied strains of this species is irradiation of the mycelium with red light with a wavelength of 635 nm (irradiation energy 51.1 mJ/cm2 ) lasting 10 s. Under these irradiation conditions for strains S.c.-01, S.c.-02, S.c.-03 S. commune the rate of radial growth of the mycelium increased from 63.8 to 84.3%. Laser irradiation of the mycelium with blue light with a wavelength of 405 nm (irradiation energy 51.1 mJ/cm2 ) for 10 s was also effective. The average growth rate increased for strains S.c.-03, S.c.-01 and S.c.-02 by 71.8 — 52.7%. The optimal concentration of glucose (8 g/dm3 ), the value of which is less than the standard (10 g/dm3 ), which is used for CGA medium, was determined. It was found for the first time that the use of CGA medium with a glucose concentration of 8 g/dm3 in combination with laser irradiation with red (wavelength 635 nm) or blue (405 nm) light with an irradiation energy of 51.1 mJ/cm2 can significantly increase the average radial velocity mycelial growth.

Вплив лазерного опромінення на ксантиноксидазну активність та генерацію супероксидного радикала в цитозольній фракції печінки щурів-пухлиноносіїв

The effect of tumor growth in the body and laser irradiation on the enzymatic activity of xanthine oxidase, in particular its D- and O-forms, and also the rate of generation of the superoxide radical (O2–) and the level of protein sulfhydryl groups in the liver rat cytosolic fraction has been investigated. It has been found that in the cytosolic fraction of rats with transplanted Guerin’s carcinoma decreases the enzymatic activity of the D-form of xanthine oxidase with a simultaneous increase in its O-form during the period of intensive (14 days, which corresponds to the logarithmic phase of on cogenesis) and the period of final tumor growth (21 days, which corresponds to the stationary phase of oncogenesis). The increase in the enzymatic activity of the O-form of xanthine oxidase was accompanied by an increase the rate of superoxide radical generation and a decrease in the level of protein SH-groups in the liver cytosolic fraction of tumor-bearing rats. Daily directed action of laser irradiation on the area of growth of Guerin’s carcinoma leads to less destructive changes in the liver. Thus, there is an increase in the enzymatic activity of the D-form of xanthine oxidase, a decrease the rate of superoxide radical formation and an increase the content of protein SH-groups in the cytosolic fraction of the liver of experimental animals compared with non-irradiated tumor-bearing rats.

Granular dynamic structures of different topologies on the surface of solid materials; control of their distribution by laser treatment

The topic is focused on the technological features of the laser radiation action on the surface of metals to study various modes of formation of granular structures, which ultimately determine the functional and structural properties of products being under laser treatment. It is presented the results and algorithms being useful to predict the development of new technological processes on the material surface induced by laser radiation with an appropriate choice of key control parameters for the corresponding phenomena.

Прямий лазерний запис мікрорельєфних структур в халькогенідних склах лазерним променевим записувачем мастер-дисків

Methods to create microrelief phase elements for diffractive optics and ophthalmology were analyzed. Direct laser writing, by a laser beam recorder used for master discs is an effective method for the formation of flat microrelief phase elements on thin films of chalcogenide semiconductors, where photo-structural transformations occur under the action of laser radiation.

Energy Conversion and Biocompatibility of Surface Functionalized Magnetite Nanoparticles with Phosphonic Moieties.

Magnetite nanoparticles (MNPs) were synthesized using two distinctly different approaches, co-precipitation (CP) and thermal decomposition (TD), and further surface functionalized with organophosphonic ligands containing different numbers of phosphonic groups. We have shown that it is possible to fabricate flower-like assemblies of MNPs through TD at lower temperatures, whereas CP MNPs formed agglomerates of particles with broad size distribution and irregular shapes. The effect of the organophosphonic ligands on the heating efficiency of the TD and CP MNPs under dual mode stimulation (simultaneous action of AMF and NIR laser radiation) was studied for the first time. It was found that in the case of the cost-effective CP MNP synthesis surface functionalization with chosen phosphonic ligands leads to higher heating efficiency upon laser stimulation, whereas better performance of TD MNPs was found under the action of AMF due to the significant difference of nanoparticle properties. The biocompatibility of surface functionalized MNPs with organophosphonic ligands was evaluated through thorough studies of the metabolic activity of MNPs in normal human foreskin fibroblasts as well as oxidative stress induction and oxidation stress response which has not been previously reported for most of the organophosphonic moieties used in this study.

Features of Vanadium-Surface Damage Induced by Pulsed Laser Radiation

The features of the damage of the surface layer of vanadium under the action of pulsed laser radiation are studied. Laser irradiation is carried out in air using a GOS 1001 setup in the Q-switching mode with the following parameters: flux power density q = 1.2 × 108 W/cm2, pulse duration τ0 = 50 ns, and number of pulses N = 1–6. The typical surface damages induced by the laser pulses are found to include the melting of material, a microcrack network, a wavy relief, and drop-like particles. The central region characterized by the greatest degree of damage contains also individual drops of metal, which crystallized like a spiral. The heat-affected zone (HAZ) adjacent to the central one is damaged to a significantly weaker extent. Surface degradation increases as the number of pulses increases. Laser irradiation is revealed to change the X-ray diffraction (XRD) patterns: loss of texture, presence of vanadium-oxide signal, peak broadening, and lattice parameter increase (from 3.022(2) to 3.027(3) A). It is shown that preliminary irradiation with argon ions (dose of 1022 m–2, E = 20 keV) affects no surface damage of the central region, while in the adjacent heat-affected zone, there is a spallation of local surface regions.

Spectral analysis combined with nonlinear optical measurement of laser printed biopolymer composites comprising chitosan/SWCNT

Biopolymer composites based on two types of chitosan (chitosan succinate and low-molecular weight chitosan) with single-walled carbon nanotubes (SWCNT) were created by laser printing. SWCNT have good dispersibility in chitosan solutions and therefore, can form relatively homogeneous films that was shown in scanning electron microscopy images. For the studies film composites were formed under the action of laser radiation on aqueous dispersion media. Study of the nonlinear optical process during the interaction of laser radiation with a disperse media has shown that low-molecular chitosan has a large nonlinear absorption coefficient of 17 cm/GW, while the addition of SWCNT lead to a significant increase up to 902 cm/GW. The threshold intensity for these samples was 5.5 MW/cm2 with nanotubes. If intensity exceeds the threshold value, nonlinear effects occur, which, in turn, lead to the transformation of a liquid into a solid phase. Characterization of films by FTIR and Raman spectroscopy indicated arising molecular interactions between chitosan and SWCNT detected as a small frequency shift and a change in the shape of radial breathing mode (RBM). The results indicate the possibility using aqueous dispersion media based on chitosan and SWCNT to create three-dimensional films and scaffolds for tissue engineering by laser printing.

Genetic features of the formed population of the genus Eisenia worms

It is known that molecular genetic methods can provide researchers with new, more accurate means for differentiating species of earthworms and determining phylogenetic distances among them. Therefore, using neutral molecular markers, ISSR (Inter-Simple Sequence Repeat) examined the internal genetic polymorphism of genus Eisenia rainworms from the vermiculture array of the Biotechnology Department of the Ukrainian State Chemical Technology University, the parent forms of which were irradiated with an LGN-208B laser for different temporary exposures and cultivated on different organic substrates. Studies have shown that the line of animals has a fairly high level of heterogeneity despite the fact that it was bred from six individuals of the same array. The laser radiation action and the hard substrate during cultivation (bottom deposits) appeared as powerful factors of selective pressure.

Parametric excitation surface waves at plasma boundary under action of p-polarized laser radiation

The parametric excitation of surface waves at the plasma boundary under the action of a p-polarized electromagnetic pump wave is analyzed. The instability, at which the pump wave decays into two surface electromagnetic TM modes, is considered. The dependence of the instability growth rate on the plasma electron density, the angle of incidence of the pump wave, and the direction of propagation of the excited surface waves is investigated. It is shown that the instability growth rate has a maximum value in the case when short-wave quasistatic surface waves are excited.

Study of Desorption Products under Laser Irradiation of the Surface of Organic Films

The paper presents the results of mass spectrometric studies of laser-stimulated desorption from the surface of thin films based on organic copper phthalocyanine molecules with peripheral substituents on gallium arsenide substrates. Thin films (30-80 nm) of copper phthalocyanine with peripheral substituents in this regard are studied for the first time. The composition of particles desorbed from the surface of CuPc and CuPcF16 films by laser radiation of various wavelengths of 532 nm and 1.06 μm with a pulse duration of 10 ns was studied. The identification of the main fragments of molecules present in the desorption stream was carried out. It was shown that under the action of laser radiation, the surface is leveled and the films are fragmented, followed by desorption of molecular fragments.

Effects of pulsed and continuous-wave laser radiation on the fabrication of tissue-engineered composite structures

We studied the formation of a composite from an aqueous dispersed medium with albumin and carbon nanotubes under the action of laser radiation in continuous wave (CW) mode and pulsed mode with a repetition rate of 10 Hz and pulse duration of 16 ns. During the experiments, the temperature was monitored at the site of exposure, as well as its distribution in the liquid. Pulsed solid-state Nd:YAG laser and CW diode laser with an irradiation power of ∼500 mW were used as radiation sources. However, a three-dimensional composite was formed only with constant exposure. The effect of pulsed laser radiation with an intensity corresponding to nonlinear interaction with water dispersion led only to its enlightenment. Thus, it is important not only the energy parameters of radiation but also the frequency of energy portions exposure for the fabrication of tissue-engineered structures (composites). As a result, it was found that the curing of the dispersion and the composite formation occurs under the action of continuous or pulsed (with a high pulse repetition rate) laser radiation at a temperature in the range from 45°C to 50°C; in case the pulse repetition rate is insufficient, composite formation is not observed even under the action of high intensity radiation and heating occurs only to a temperature of ∼40 ° C. This formation process can be generated both in the visible 532 nm and in the infrared 810-nm wavelength ranges. In this case, one of the main conditions is the absence of albumin or cells absorption at these wavelengths so that absorption occurs mainly with single-walled carbon nanotubes. Studies of the surface and internal structure of the composite made it possible to demonstrate the binding of nanotubes to each other. This happened under the influence of laser radiation. This led to high hardness values of the composites. The average value of hardness was 0.26 ± 0.02 GPa.

Formation of Coatings under the Action of Laser Radiation in Liquid Media

The influence of the chemical composition of the substrate material on the chemical and phase composition of the formed coating was investigated. A number of experiments aimed at studying the interaction of titanium alloys with ultrashort laser pulses in different reaction media was carried out. A new method for the formation of titanium carbide under the action of ultrashort laser pulses on the surface of a titanium sample in a liquid hydrocarbon and liquid nitrogen medium is described. The description of the experiment is presented. The treated surface was investigated using a scanning electron microscope. Raman spectra from the surface of treated titanium alloys under different exposure conditions are obtained.

Synthesis of Ultra-Dispersed Spherical Composite Materials

This paper describes a method of laser synthesis of titanium microspheres, titanium carbide and silicon oxide. The formation of microspheres is carried out under the action of femtosecond laser radiation on the surface of the sample. The analysis was carried out on a scanning electron microscope. The obtained titanium and titanium carbide microspheres have an average size of the main fraction of 1-3 μm and can be used in applications of additive technologies and powder metallurgy as the main raw material or as an alloying additive. The main fraction of silicon oxide granules lies in the range of 50-300 nm. To improve the efficiency of the particle output, a combined method of laser action and electric current is proposed.

Estimation of Instabilities under the Joint Action of Laser Radiation and a Magnetic Field on a Plasma

Estimation of Instabilities under the Joint Action of Laser Radiation and a Magnetic Field on a Plasma

Изменение морфологии, структуры и микротвердости образцов циркониевого сплава в результате воздействия лазерными импульсами

The results of experimental studies on the modification of the surface layer of zirconium alloy grade E 110 by the action of pulsed laser radiation are presented. It was established that, as a result of laser treatment, the morphology of the surface layer changes with the formation of nanoparticles up to 50 nm in size. The relief of the treated surface becomes structurally heterogeneous, containing phases of zirconium and monoclinic ZrO2 dioxide. It was revealed that, as a result of exposure to laser pulses, a significant increase in the microhardness of the surface of zirconium samples occurs to 27.1 ± 0.1 GPa.

Occupational diseases caused by exposure to laser radiation

Sources of laser radiation are firmly entrenched in all spheres of human activity: different branches industry, biology, gene engineering, medicine, agriculture. In cases of gross safety violations, laser radiation can be dangerous for people working with it. Biological action of laser radiation is not completely found out. By the nature of human exposure to laser radiation, it is divided into direct, diffuse, specularly reflected and diffusely reflected. It can cause both primary effects, which include organic changes that occur in irradiated tissues, and secondary effects, which are nonspecific changes that occur in response to radiation. The «critical» organs for laser radiation are the eyes and the skin. Laser lesions are divided into acute and chronic. Acute lesions occur either in cases of gross security breaches or emergencies. The development of chronic lesions is possible in cases of prolonged work with low-intensity laser devices. Other adverse factors, such as noise, vibration, light from flash lamps, ultraviolet radiation, tiredness of visual analyzer, air pollution (ozone, oxide of nitrogen), neuro-emotional tension, affect workers during exploitation of laser radiation’s sources. Diagnostics of laser lesions is based on the occupational history data of sanitary and hygienic characteristics of working conditions as well as on the results of clinical examination and dosimetry data. There is no specific treatment for laser lesions.

Study of the mechanism of attenuation of thermocapillary convection of the melt during laser powder cladding

The results of a numerical solution of the thermocapillary microconvection problem arising under the action of laser radiation in a liquid metal during laser surface treatment are presented. A characteristic feature of the behavior of particles of refractory metals in a multi-vortex melt pool is revealed. The influence of falling powder particles in the melt on the inhibition of thermocapillary convection is estimated. The mechanisms of slowing the melt flow associated with the addition of powder components for laser alloying or cladding is discussed. The results of three-dimensional calculations are presented, which show how these mechanisms can work.