Nikolay A. Bulychev

Ag nanoparticles suspensions for stimulated Rayleigh backscattering of single frequency 0.5 micron pulsed laser radiation

The spectral characters and increments of stimulated Rayleigh scattering in pure liquids and suspensions of Ag nanoparticles in toluene and hexane of principally different nature were investigated in this work. The correlation of two photon absorption spectra and stimulated scattering efficiency were discovered and analyzed. It is shown experimentally that the frequency shift of the scattered signal relative to the pump frequency greatly exceeds the theoretical value.

Obtaining of hydrogen in acoustoplasma discharge in liquids

The paper shows, that a low-temperature plasma initiated in liquid media in interelectrode discharge gap is able to decompose hydrogen containing organic molecules resulting in obtaining gaseous products with volume part of hydrogen higher than 90% (up to gas chromatography data). Tentative assessments of energy efficiency, calculated with regard for hydrogen and feedstock heating value and energy consumption, have shown efficiency factor of 60-70%, depending on the source mixture composition. Theoretical model calculations of discharge current and voltage have been performed; the values are in good accordance with experimental data.

Stimulated low-frequency Raman scattering in aqueous suspension of nanoparticles

The low-frequency acoustic mode in nanoparticles of different nature in aqueous suspension has been studied by stimulated low-frequency Raman scattering (SLFRS). Nanoparticles investigated (CuO, Ag, Au, ZnS) had different dimensions and different vibrational properties. Synthesis of cupric oxide nanoparticles in acoustoplasma discharge is described in details. SLFRS has been excited by nanosecond pulses of ruby laser. Spectra of the scattered light had been registered with the help of Fabry-Perot interferometer. SLFRS conversion efficiency, threshold and frequency shift of the scattered light are measured.

Dynamic characteristics of electric discharge in liquid under ultrasonic cavitation

The characteristics of electrical discharges in liquid media under the influence of intense ultrasonic vibrations are investigated and the difference in dynamic characteristics of discharges before cavitation and after cavitation begins. The experiments carried out during this work made it possible to establish that in a liquid in an intense ultrasonic field above the cavitation threshold there exists a special form of an electric discharge characterized by volumetric luminescence in the entire space between the electrodes and the current-voltage characteristic inherent in an anomalous glow discharge in a gas.

Study of physical properties of metal oxide nanoparticles obtained in acoustoplasma discharge

Nanoparticles of tungsten, copper, iron, and zinc oxides were synthesized in acoustoplasma discharge. Their size distribution was studied by electron microscopy and laser correlation spectroscopy. Ultrasound was found to narrow significantly the size distribution width of zinc oxide nanoparticles. Water suspensions of zinc oxide nanoparticles showed photoluminescence in red and near infrared spectral ranges, which makes them a promising material for luminescent diagnostics of biological systems.

Luminescent properties of nanoparticles synthesized in electric discharge in liquid under ultrasonic cavitation

In this paper, differences in the luminescence intensity of nanoparticles of metal oxides synthesized in electric discharges in liquid media under the influence of intense ultrasonic vibrations prior to cavitation and after the start of cavitation regime have been studied. The increase in the luminescence intensity of nanoparticles obtained by ultrasonic cavitation can be explained by the formation of defects in oxide crystals under the influence of intense mechanical action. In the process of synthesis, the particles are exposed not only to the action of electromagnetic fields, but also to shock waves during the collapse of cavitation bubbles, which leads to the formation of defective valence structures and delocalization of electrons.

Comparative analysis of parameters of pulsed copper vapour laser and known types of technological lasers

In the present paper we present the results of a comparative analysis of pulsed copper vapour lasers with visible emission wavelengths of 510.6 and 578.2 nm and pulse duration of 10-30 ns and known types of technological lasers as well as the prospects for using the copper vapor laser for microprocessing of materials.

Properties of metal oxide nanoparticles prepared by plasma discharge in water with ultrasonic cavitation

Acoustic plasma discharge and cavitation in aqueous solutions were used to prepare metal oxide nanoparticles (NPs) based on tungsten, copper, iron and zinc. It was found that ultrasonic cavitation during the NP formation influenced strongly the size and physical properties of NPs, which were measured by means of the electron microscopy, dynamic light scattering (DLS) and photoluminescence (PL) techniques. In vitro studies did not reveal cytotoxicity of the NPs for concentration of up to 0.2 mg/mL and exposure time for one week. The obtained results indicate good prospects of the prepared NPs for biomedical applications in the PL diagnostics of cancer and magnetic hyperthermia.

Possibilities of using pulsed lasers and copper-vapour laser system (CVL and CVLS) in modern technological equipment

Research on CVL installations with an average power of 20–25 W of cutting and drilling has shown wide range of applications of these lasers for micromachining of metals and a wide range of non-metallic materials up to 1–2 mm. From the analysis indicated that peak power density in the focused light spot of 10–30 μm diameter must be 109 –1012 W/cm2 the productivity and quality micromachining, when the treatment material is preferably in the evaporative mode micro explosions, followed by the expansion of the superheated vapor and the liquid. To achieve such levels of power density, a minimum heat affected zone (5– 10 μm) and a minimum surface roughness of the cut (1–2 μm), the quality of the output beam of radiation should be as high. Ideally, to ensure the quality of the radiation, the structure of CVL output beam must be single-beam, diffraction divergence and have at duration pulses τi = 20–40 ns. The pulse energy should have low values of 0.1–1 mJ at pulse repetition rates of 10–20 kHz. Axis of the radiation beam instability of the pattern to be three orders of magnitude smaller than the diffraction limit of the divergence. The spot of the focused radiation beam must have a circular shape with clear boundary, and a Gaussian intensity distribution.

Acoustoplasma synthesis of nanoparticles of metal oxides and formation of nanostructured coatings on material surfaces under ultrasonic treatment

In this paper, a new form of plasma discharge in a liquid under intensive ultrasonic treatment exceeding the cavitation threshold has been explored in view of initiation of various physical and chemical processes. Furthermore, in this plasma discharge, nanoparticles of oxides of various metals with controlled shape and size of particles and narrow particles size distribution have been synthesized. Further research proved that ultrasonic cavitation during synthesis significantly affects the physical and chemical characteristics of nanoparticles. These nanoparticles can be used for formation of nanostructured coatings on surfaces of various materials by an ultrasonic technique.